Nationdal Academy of Sciences National Research Council The Radiochemistry of Plutonium U R 1,111 3% 7 Commission COMMITTEE ON NUCLEAR SCIENGCE D. A. Bromley, Chairman Yale University R. D. Evans, Vice Chairman Massachusetts Institute of Technology Lewis Slack, Secrelary Naticnal Research Council E. C. Anderson Los Alamos Scientific Laboratory N. E. Ballou U. 8. Naval Radiological Defense Laboratory Martin J. Barger National Bureau of Standards C. J. Borkowski Oak Ridge National Laboratory Herbert Goldstein Columbia Universgity Bernd Kahn Taft Sanitary Engineering Center LIAISON MEMBERS Harold Glager Office of Naval Research George A, Kolstad Jerry B. Marion University of Maryland R. L. Platman Argonne National Laboratory Ernest C. Pollard Pennsylvania State University Katharine Way Oak Ridge National Laboratory George W. Wetherill ‘University of California Marvin E. Wyman University of Illinois William §. Rodney National Science Foundation Atomic Energy Commission SUBCOMMITTEE ON RADIOCHEMISTRY Nathan E, Ballou, Chairman 1J. 8. Naval Radiological Defense Laboratory G. R. Choppin Florida State University Herbert M. Clark Rensselaer Polytechnic Institute Richard M. Diamond Lawrence Radiation Laboratory Jerome Hudls Brookhaven National Laboratory Jere D. Knight Los Alamos Scientific Laboratory W. E. Nervik Lawrence Radiation Laboratory Julian M. Nielsen Battelle Pacific Northwest G. D. O'Kelley Oak Ridge National Laboratory E. P. Steinberg Argonne National Laboratory D. N. Sunderman Battelle Memorial Institute John W. Winchester Massachusetie Institute of Technology R. P. Schuman, Consultant Sri Venkateswara University Tirupati, Andhra Pradesh, India The Radiochemistry of Plutonium George H, Coleman September 1, 1965 UNIVERSITY OF CALIFORNIA Lawrence Radiation Laboratory Livermore, California AEC Contract No, W-7405-eng-48 Subcommittee on Radiochemistry Nationel Academy of Sciences— Nationzl Research Council Printed in USA, Price $2.00. Available from the Clearinghouse for Federal Scientific and Technical Informaton, National Bureau of Standards, U. S. Department of Commerce, Springfield, Virginia. FOREWORD The Subcommittee on Radiochemistry is one of a number of subcommittees working under the Commlittee on Nuclear Scilence wlthln the Natlonsal Acedemy of Sciences - Nationael Research Council. TIte members represent government, industrial, and university laboratories in the areas of radiochemiptry and nuclear chemipgtry. Support for the activities of this and other subcormittees of the Committee on RNuclear Sclence is provided by a grent from the Natiomal Scilence Foundation. The Subcommittee has concerned 1tself with preparation of publications, encouraging and supporting activitles in nuclear education, spomsoring sympoeiz on selected current topics 1n radiochemistry and nuclear chemlstry, and investigating special problems as they ariese. A series of moncgraphs on the radio- chemistry of essentielly all the elemente and on radiochemical technlques is being published. Initiation end encouragement of publicatlon of erticles on nuclear education in various subjJect areas of chemistry bave occurred, and development and improvement of certain educetional mctivities (e.g., laboratory and demonstration experiments with radiocasctivity) have been encouraeged and asgisted. Radloactive contaminatlon of reagents end materinls has been lnvestigeted and epeclfic recommendatlons made. This serlies of monographs bas resulted from the need for comprehensive compllations of radiochemical and nuclear chemical information. Each monograph collects in one volume the pertinent information required for radlochemical work with an individual element or with a specialized technique, The U, S, Atomlc Energy Commission hes sponsored the printing of the series. Comments and suggestions for further publicatione and activitles of value to persons working with radlcasctivity are welcomed by the Subcommittee. N. E. Ballou, Chalrman Subcommittee on Radiochemistry iil PREFACE This report has been prepared as one of a series of monographs on the radio- chemistry of the elements for the Subcommitte on Radiochemistry of the Committee on Nuclear Science within the National Academy of Sciences. There is included a review of the nuclear and chemical features of plutonium of particular interest to the radiochemist, a discussion of sample dissolution and counting techniques, and finally, a collection of radiochemical procedures for plutonium . The literature search was completed epproximately through September 1964. It is hoped that the bibliography is sufficiently extensive to serve the needs of the radiochemipt, but it is to be expected that important references were omitted. The author would appreciate being made aware of such omissions, that they might be included in possible future editions of this monograph. The author wishee to express thanks to Dr. Earl Hyde, for the loan of his extensive card file on the radiochemistry of plutonium, to Carl Wenarich and the staff of the LRL Library who greatly assisted in the literature search, to Mrs. Shauna Ness who typed the first draft, and to Mrse. Vivian R. Mendenhall who competently edited the final draft and prepared the bibliography. Finally the author thanks his colleagues at the Lawrence Radiation Laboratory, especially Dr. R. W. Hoff, for reading and criticizing the manuscript, and Dr. P. C. Stevenson for his continued interest and support during the writing of this monogreaph, George H. Coleman Lawrence Radiation Laboratory University of California Livermore, California iv II. IT1. vL VIIL VIIL, CONTENTS General Reviews of the Inorganic and Analytical Chemistry of Plutonium . ' General Reviews of the Radiochemistry of Plutonium . Table of Isotopes of Plutonium . . . . Chemistry of Plutonium of Special Interest to the Radiochemist A. Metallic Plutonium A.1 Preparation A_.2 Physical Properties A.3 Chemical Properties B. Compounds of Pu C. Plutonium Ions in Solution .1 Oxidation States 2 Oxidation Reduction Reactions 3 Disproportionation Reactions .4 Radiolytic Reduction of Pu Solutions 5 Hydrolytic Reactions of Plutonium 6 Pu(IV) Polymer .7 Complex [on Formation . coppaao0 D. Separation Methods D.1 Co-precipitation and Precipitation D.2 Solvent Extraction Methods | D.3 Ion Exchange . Dissolution of Plutonium Samples for Analysis A. DMetallic Plutonium B. Other Compounds C. Biological and Environmental Samples Source Preparation and Counting Methods A. Source Preparation A.1 Direct Evaporation A.2 Electrodeposition A.3 Other Methods B. Counting Safety Considerations A. Radioactive Safety - B. Criticality Safety Collection of Procedures A. Introduction B, Listing of Contents Procedure 1. Determination of Pu in solutions containing large amounts of Fe and Cr . . Procedure 2. Separation and determination of Pu by TTA extraction Page No. © O @M B bR W N R W © O W W O © W O W =~I N N N = =2 == © O 3 1 60 O 0 6 o0 o U Bk b J o0 g, 102 102 103 105 105 105 108 112 Procedure Procedure Procedure Procedure Procedure Procedure Procedure Procedure ‘Procedure Procedure Procedure Procedure Procedure Procedure Procedure Procedure Procedure Procedure Procedure Procedure Procedure Procedure Procedure Procedure Glossary . . References . 3. 4. 9. 6. 9a. 9b. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22, 23. 24. 25. CONTENTS (Continued) "Procedures (Continued) Separation and determination of Pu in U - fission product mixtures Plutonium Plutonium Separation of Plutonium from Uranium and Fisgion Products in Irradiated Reactor Targets Determination of Pu Uranium and Plutonium Analysis Separation of Plutonium from Irradiated Uranium Separation of Plutonium from Urahium Metal Purification of Plutonium from Uranium and Fission Products Uranium and Plutonium from Environmental Samples of Soi1l, Vegetation and Water Plutonium from Environmental Water Samples Plutonium from Environniental Water Samples Separation of Plutonium in Uranium-Plutonium Figssion Element Alloys by TBP Extraction from Chloride Sclutions . . Separation of Pu before Spectrographic Analysis of Impurities Anion Exchange Method . Separation of Plutonium Before Spectrographic Analysis of Impurities. Extraction Chromatography Method Using TBP Separation of Np and Pu by Anion Exchange Separation of Np and Pu by Cation Excha.nge Chromatography . Determination of Plutonium in Urine Determination of Pu239 in Urine (Small Area Electrodeposition Procedure) Determination of Plutonium in Urine Determination of Americium in Urine in the Presence of Plutonium . . Determination of Plutonium in Urine by Anion Exchange Determination of Plutonium in Urine by Co-~ crystallization with Potassium Rhodizonate Determination of Plutonium in Urine and Bone Ash by Extraction with Primary Amines Page No. 114 116 118 122 124 126 129 130 131 132 134 1317 140 142 144 148 149 150 153 155 158 161 164 166 167 169 1. 10. 11. 12, 13. 14. 15. The Radiochemistry of Plufonifim GEORGE H. COLEMAN Lawrence Radiation Laboratory, Universii:y of California Livermore, California I. GENERAL REVIEWS OF THE INORGANIC AND ANALYTICAL CHEMISTRY OF PLUTONIUM ' J. J. Katz and G. T. Seaborg,. '"The Chemistry of the Actinide Elements," Chap. VIO, (John Wiley and Sons Inc., New York, 1957), pp. 239-325. _ "Plutonium," in Nouveau Traite de Chimie Minerale, Paul Pascal, Genl. Ed. Vol. XV, "Uranium et Transuraniens' (Masson et Cie, Paris, 1962) pp 324-864. "The Complex Compounds of the Transuranium Elements,'" A. D. Gel'man, A. I. Moskvin, L. M. Zaitsev, and M. P. Mefod'eva (Consultants Bureau, New York, 1962 transl. by C. N. and T. I. Turton). ' M. Taube, . Plutonium, (Macmillan Co., New York, 1964; transl. by E. Lepa and-Z. Nanowski) Chap. 2, pp 39-84. R. E. Connick, "Oxidation States, Potentials, Equilibria, and Oxidation-Reduction Reactions of Plutonium,''in The Actinide Elements, Natl. Nucl. Energy Series, Div. IV, Plutonium Project Record Vol. 14A; Chap. 8, G. T. Seaborg and J. J. Katz, Eds. (McGraw-Hill Book Co., Inc., New York, 1954) pp 221-300. J. C. Hindman, "Ionic and Molecular Species of Plutonium in Solution," in The Actinide Elements, Vol. 14A, Chap. 10, pp 371~-434. B. B. Cunningham,l'"Preparation and Properties of the Compounds of Plutonium," in The Actinide Elerments, Vol. 14A, Chap. 10, pp 371-434. - C. F. Metz, "The Analytical Chemistry of Plutonium," Anal. Chem. 29, 1748 (1957). D. Nebel, "The Analytical Chemistry of Plutonium,'" Joint Publications Research Service NYC, AEC Report JPRS-11689. transl. from Chem. Tech. Leipzig, 13 522 (1961). P. N. Palei, "Analytical Chemistry of the Actinides,"' transl. by S. Botcharsky, AERE-LIB/TRANS-787. (See also J. Anal. Chem. USSR 12, 663 (1957).) A. J. Moses, ""The Analytical Chemigtry of the Actinide Elemenis' (Macmillian Co., New York, 1963). A. Schiffers, "Plutonium, seine chemischen und physillilischen Eigenschaften," Chemiker Zeit. 86, 656 (1962). K. W. Bagnall, "The Transuranium Elements," Sci. Progr. (London) 52, 66-83 {(1964). V. I Kuznetsov, S. B. Savvin, and V. A. Mikhailov, "Progress in the Analytical Chemistry of Uranium, Thorium and Plutonium,' Russ. Chem. Rev. 29, 243 (1960). R. Kraft, C. J. Wensrich and A. L. Langhorst, '""Chemical Analysis of Plutonium and Plutonium Alloys: Methods and Techniques,' Lawrence Radiation Laboratory, University of California, Livermore, Calif. UCRL-6873, 1262. 1 186. 17. 1a. 19, I0I. GENERAL REVIEWS OF THE RADIOCHEMISTRY OF PLUTONIUM" E. K. Hyde, "Radiochemical Separations of the Actinide Elements!' in The Actinide Elements, National Nuclear Energy Series, Div. IV, Plutonium Project Record Vol. 14A, G. T. Seaborg end J. J. Katz, Eds. (McGraw-Hill Book Co., New York, 1854) Chap. 15. E. K. Hyde, "Radiochemical Separations Methods for the Actinide Elements," in Proc. of the International Conference on the Peaceful Uses of Atomic Energy, Geneva, 1955, A/CONF. 8/7, (United Nations, New York, 1956) pp 281-303, Paper T28. M. P. Faugeras, ''Separation et Purification des Isotopes, (of Plutonium),! in Nouveau Traite de Chemie Minerale, Paul Pascal, Gen. Ed., Vol. IV, "Uranium et Transuraniens," ( Masson et Cie, Paris, 1962) pp 339-385. M. Taube, Plutonium (Macmillan Co., New York, 1884; transl. by E. Lepa and Z. Nanowski). "Radiochemical Methods of Analysis,' pp 78-84. Il — TABLE OF ISOTOPES OF PLUTONIUM " Specific a Particle Activity Type of Energy Isotope Half Life (d/m/ug) Decay (MeV) Method of Preparation Pu232 36 min -- @2%, 6.58 U232 4 100 MeV a EC 98% particles Pu?? 20 min -- @0.1%, 6.30 U233 4 40 MeV o EC 99 + % particles Pu23% 9.0 hr -- @6%, 6.19 233,235 40 MeV o EC 94% particles Daughter of Pu>3® 26 min -- 03 X 10799, 5.85 u233:235 | 50-30 Mev EC 99 + % a particles Pu?3® 285 yr 1.18x10° & 5.763 (69%) TUZ°° + 40 MeV o particles 5.716 (31%) Daughter Np236 Daughter Cm?240 237 235 , . Pu 45.6 days -- a 0.003%, 5.36 (79%) U + 40 MeV agparticles EC99+ % 5.65 (21%) Pu?*®® g4yr 3.88x107 & 5.495 (12%) U228 4 deuterons - 5.452 (28%) Daughter Cm?242 Pu239 1 high energy neutrons Np237 + neutrons Pu??? 24360 yr 1.36 x10° @ 5.147 (13%) UZS® 4 neutrons 5.134 (17%) 5.096 (10%) pu®4? g580yr 5.00x10° 4 5.162 (16%) U235 4 neutrons 5.118 (24%) Pu239 + neutrons Daughter of Cm?244 Pu??l 13.0yr 257x108 sax1073%, 4.89 %38 | neutrons B- 99 + % Daughter of Cm245 U236 + o particles Pu?®? 379 x10° se5x10° o 4.898 (76%) U= 4 neutrons yr 4.858 (24%) Am241 4 neutrons Pu?¥d 498 hr -- B~ --- Pu42 | neutrons Pu244 7.6 X 107 42.8 a -—- Am243 + neutrons yr Pu242 + neutrons Pu?%® 10.6 hr -- B~ --- Pu?4% 4 neutrons Pu246 10.85 days ~-- B~ - U23B + neutrons (ther- monuclear explosion) The data for this table were taken from the recent review of Hyde, 192 This work should be consulted for further details and references to the literature. IV. CHEMISTRY OF PLUTONIUM OF SPECIAL INTEREST TO THE RADIOCHEMIST A, Metallic Plutonium A.1 Preparation Plutonium metal is most commonly prepared by the reduction of a halide by a more electropositive metal such as calcium. Connor ~ has compared various combinations of halide and reducing metal and found that the only satisfactory reactions were PuFB, PuF , and PuCl3 reduced with Ca metal. Harmon and Reaslfi4 and 01:'1:h-3o6 have discussed the conversion of Pu salts to metal on an industrial scale, while Anselin, et 31.30 describe a method for the conversion on a gram scale. A.2 Physical Properties Pu is a typically silver-white appearing metal which has a number of peculiar physical properties. The metal undergoes a total of five allotropic modifications below the melting point, two of which have negative coefficients of thermal expansion. Table IV-1 summarizes the more important physical properties. A.3 Chemical Properties Pu is a very reactive metal. The potential for the couple Pu = Pu Tt + e is 2.03 volts, which places it between acandium (Sc) and thorium (Th) in the EMF series of elements. Pu oxidizes more readily than does U, and resembles cerium (Ce) in its reactions in air. Superficial oxidation of a freshly prepared surface occurs in a few hours in normal air. The oxide is more or less adherent, and in several days the oxidation reaction accelerates until finally the oxidation to Pqu is complete. However, the oxide coating protects the underlying metal in dry air, and the oxidation proceeds more slowly. Pu metal is attacked at elevated temperatures by most gases; Hz, N2' halogens, SOZ’ etc. Pumetal dissolves easily and rapidly in modérately concentrated HCI1 and other halogen acids. Pu forms intermetallic compounds with intermediate solid solutions with most metallic elements. However, simple eutectic mixtures are usually made with the group '_ Va and VIa ‘metals, and very little solubility in either the liquid or solid state is ex- hibited by alkali and alkaline earth metals. ' The behavior of Pu toward various solutions is given in Table IV-~2. TABLE IV-1. Physical Properties of Plutonium Metal” copp Appearance - Melting point 639.5°C Boiling point 3508 +£ 19°C Properties of the various @ B allotropic modifications Transition temperature to next higher phase (°C) 125 210 Density (g/cm?’) 19.82 17.82 (at T°C)~ (25) (133) Crystal structure Monoclinic Body - centered monoclinic Coelficient of linear 67X 107° 41x 107" expansion (°C-1) (in temp range °C) (80-120) (160~200) Liatent heat of trans- formation to next higher 958 140 phase (cal/g-atom) Electrical resistivity 68.5u0- cm (at 25°C) Self heating coefficient {1,923 £ 0.019) X 10™° W/g Ionization potential 5.1+ 0,5 eV "Data compiled from various secondary sources, including 'E‘rancis,137 Silvery white; quickly oxidizes in air 315 17,14 (235) Orthorhombic 35 x 1070 (220-280) 156 460 15.92 (320) Face- centered cubic 8.6 x 1070 (340-440) 17 Colfinberry and Waldron, 475 16,00 (465) Body-or face- céentered tetragonal 94 ~ and Jette, 2 1 L 4 1 640 16.48 (510) Body- centered cubic 15 490G-550 940 TABLE IV-2. -Behavior of Pu Metal in Various Solutions Solution Behavior H20 Very slowly attacked _ Salt water .Rapidly attacked after induction period HCl, HI, HBr Rapid dissoclution Acetic acid HC1O HNO 4 3 H3PO4 H2804 Sulfamic acid No visibie reaction in concentrated acid; slow dissolution in dilute acid ' Rapid dissolution in concentrated acid Very slow attack, limited principelly to the oxide coating. The surface is passivated Rapid dissolution in concentrated acid Very slow attack with similar behavior to I-INO3 Rapid dissolution B. Compounds of Pu Pu forms compounds with a large number of elements. Compounds of Pu in the II through VI oxidation states are known, Cu.n.ningham,7 and Faugeras and Heuberger 128 describe the preparation and properties of those compounds which have been prepared. Gel'man, et al. emphasize the data on complex compounds and attempt to systematize the data by relating the structures and coordination numbers of the complex compounds to other actinide elements, as well as to other regions of the periodic table. The compounds of the III, IV and VI oxidation states are the ones with which the radiochemist deals, and the insoluble compounds are of primary interest. Of these the insoluble hydroxides, fluorides, and oxalates, phosphates and peroxides of the ITT and IV states are of major interest in precipitation and co-precipitation reactions and are described in more detail in that section. Omne of the great complicating factors in Pu chemistry is the formation of a polymeric form by hydrolysis in dilute acigd or neutral solutions. The polymeric form can be quite intractable in many reactions 2 and may be difficult to destroy. The section on hydrolytic reactions of Pu gives details, Table IV-3 lists solubility information for the more stable Pu compounds which have been prepared. TABLE IV-3. Solubility of Plutonium Compounds” .Reference Pul, -PuH, s. ™ Hcl, H,S0,, i. HNO,, decomp. in HyO 'Pu]:"-‘a—PuF4 decompoeses influoride complexing agents; e. g. H3BO3 i. H20, mineral acids Pu02F2 i. H20 27 Na.PuF5 sl. s, dilute H-‘NOBHF, i. NaF-HF s. HSBOS' Pul-'*‘6 decomposes violently in H20 PuCl3 8. H20, acid CszPuCI6 8. acid, HEO PuBr3 s, HZO TABLE IV-3 (Cont.) Reference PuI3 5. H20 Pu(IO3)'.3 s. HNOB, i. H2504-KIO3, excess HIO3 Pu(IO3)4 = HNOS, decomposed in stC)3 PuO2 s. slowly in boiling mineral acids; reaction speeded by fusion with NaHSO4 or HF added to HNOg; solubility is more difficult if ignited " above 500° Pu(OH)3 8. mineral acid Pu(OH) 8. mineral acid 4 -23 264 Pu02(OH)2 g. mineral acid, Kgp = 1.8 X.10 Pu peroxide g, conc. HNO3, HZSO4 MPu(SO4)2, M=Na, K, Rb, Cs, NH4 i. MZSO4-H2$O4, 8. H20 alcohol Pu(SO4)2 8. HZO’ i. alcohol M4Pu(804)4, M=K, Rb, NH4 B. H20, i. elcohol Pu{NO,) s. H.,O, colloidal Pu forms in 3’4 %us MZPU(Noa)G, M=K, Rb, Cs, Tl PuPO 4 PU(HPO4)Z- XHZO Pu,H(PO,),: YH,O0 PucC, szC3 1_31.10(303 KG[Pu(Cos)S]- mH,0 K12 [ Pu(CO3)g] - mHO M,[PuO,(CO4)4], M=K, NH, HPuFe(CN)g- xHg0 PUFe(CN)B PuB[Fe(CN)G] 4 X0 (PuO,) ,[Fe(CN)g] o+ xH,0 PU(C,0,), *6H,0 Pu02(0204) -3 HZO NaPqu(Czl-IBOz)z aque soln. s. HNOS, ether, acetone i. conc.HNO3, 8. H20, dil acid s. hot conc. mineral acid; sl. s. H3P04, NaOH; i. HC2H302 i. rnineral acid — H3PO4 s. HCl, HpSO4, i. cold conc HNO, 8. hot conc. I-l'l\TO3—1\TaLF2 i. H20, gl. s. cold mineral acids i, alcohol s. NagCOs, LiHCOa, sl. s. s. mineral acid i. HCI1 i, HCl i. HC1 i, HC1 i. H30, s. mineral acid; sl. s. K,C,0,, (NH).C.O 27274 : 4'27274 i. Hy0, 8. HySO4, HNO3, HCIOg4 sl. s. acid~-K9Cg0O4, NH2C504 minimum s. in 1.5 M HNOg - 0.025 M H,C50, H20, 264 s. mineral acid; sl. s, acid - H2C204 gl. s. hot H O, s. acid 2 *Compiled primarily from the reviews of Cun.ningharn7 and Faugeras and Heuberger128 Unless otherwise specified, the data are taken from these reviews. **The following abbreviations are usead: s. soluble i, insaluble sl, s. slightly soluble - conc. concentrated dil. dilute . C. Plutonium Ions in Solution C.l Ogxidation States Plutonium in aqueous solution exists in the +3, +4, +5, or +6 oxidation states, resembling both uranium (U), neptunium (Np) and americinm (Am) in this respect. The formal oxidation potential diagrams for Pu in acid and basic solution are teken from Latimer, 220 ACID SOLUTION 2.03 Pu +++ -0.97 Pu+4 -1.15 PuO+ -0.93 Pu02++ Pu 9 l -1.04 BASIC SOLUTION 2 pu 2:42 Pu(OH), 9.95 -0.76 Pu020H -0.26 Pu(OH)4 PuO2 (OH)2 -0.51 Formal oxidation potentials for Pu couples in various 1 M sclutions are shown in Table IV-4. The displacements of the potentials are due to the complex-forming tendencies of the anions with Pu, TABLE IV-4, Formal Potentials for Pu Couples in Various 1 M Solutions Pu(lI)-Pu(IV}) Pu(IV)-Pu(VI) Pu(HI)-Pu(VI) Pu(V)-Pu(VI) HCIO, -0.982 ~1.043 -1.023 -0.92 HCl -0.970 -1.052 -1.024 -0.912 HNO, -0.92 -1,05 -1.04 —----- H,S0, -0.74 -1.2-1.4 e-e-e- —eeees The lower oxidation states become more stable in the actinide series from U to Am, and correspondingly the higher oxidation states become more difficult to attain. - - This effect is illustrated in Table IV-5, which shows the free energies of formation of various actinide ions, TABLE IV-5. Free Energy of Formation of Actinide Ions (kcal/mole) Mt vt Mo; MO';' U ~124.4 . -138.4 -237.6 -236.4 Np _128.4 ~124.9 ~221.0 -194.5 Pu ~140.5 ~118.2 -204.9 -18B3.5 Am -160.5 -110.2 (-194.5) -156.7 Thus the most stable +3 ion in this series is Am , While the most stable +6 ion is +_|. uo, . enough in agueous solution to be useful in separation chemistry. Pu is the first member of this series in which the tripositive state is stable This fact is of supreme importance in the radiochemistiry of Pu, since Pu can be selectively maintained in either the +3 or +4 oxidation states in separation schemes. Advantage is taken of this ability in many of the collected procedures in section VI. - The oxidation-reduction behavior of Pu is complicated by several factors: (1) P&lOt disproportionates into Pu-l-4 and Puo-;'- and under certain conditions Pu+3, put . Puo;' and Puo-;_ can all exist in equilibrium; Put? ig a small, highly charged ion and therefore undergoes extensive hydrolysis at low acidity and forms many stable complex ions. This tendency is a dominant feature of Pu(IV) chemistry. Pu(IV) forms a long-chain compound or polymer by hydrolytic reactions, Pu(IV) polymer is one of the more unpleasant aspects of Pu chemistry from the standpoint of the radiochemist. C.2 Oxidation-Reduction Reactions Table IV-6 lists reagents and conditions to effect changes in oxidation state for Pu ions. It must be emphasized that a relatively small change in conditions may - produce a large change in the equilibrium, and that some of the oxidation-reduction reactions may proceed beyond those listed. Therefore, the listed reactions should be taken as a guide only. In general, the change in oxidation state between +3 and +4 is rapid, since only one electron is invalved in this change. Similarly PuO+ and Pu0++ changes are rapid. 2 2 Changes in the oxidation state of Pu which involve the making or breaking of a Pu-O bond are usually slower. However, Hj.ndmam,184 in a general review of the kinetics of actinide oxidation-reduction reactions, gives examples of reactions involving M-O bonds which proceed as rapidly as some involving only electron transfer, Newton and R:a,bideamu302 have also reviewed the kinetics of actinide oxidation-reduction reactions. C.3 Disproporticnation Reactions The potentials of the various Pu couples are such that appreciable quantities of several oxidation states may exist in equilibrium, Pu(IV) and Pu{V) are both unstable with respect to disproportionation into higher and lower oxidation states in weakly acid, uncomplexed media. There are several important equilibria which must be considered for an understanding of Pu oxidation-reduction chemistry, TABLE TV-6. Oxidation-Reduction Reactions of Plutonium Ions* ' A. Pu(Im)—» Pu(IV) Reagents Selution Temp. Rate Reference - - i K . BrQjg Dilute acid R.T. Very rapid Cett 1.5 MHCI R.T. Very rapid 6§ M HCI, R.T. Very rapid 235 dilute H2504 R.T. Very rapid 235 (312 0.5 MHClL R.T. Slow (tl/2 > 9 hr) H202 R-6 M HCl R.T. Equilibrium at 90% Pu(IV) in several hours 145 4-8 M HCIO, - R.T. Equilibrium at 80-90% Pu(IV) in several hours 145 Crzo; Dilute acid R.T. Extremely rapid HIO, Dilute acid R.T. Extremely rapid MnO, Dilute acid R.T. Extremely rapid 79 O, 0.5 M HCI R.T. No oxidation in 42 hr- 97° C 2.5% oxidized in 4 hr, more rapid in higher NOé HNO, R.T Very rapid 63 0.4 — 2 M HNOg, ) Fe(ll) Sulfamate, R.T. Complete in few minutes 63 0.1 M HNO, b This table is an enlarged version of the one given by Katz and Seaborgl which was compiled from data given by Connick. tained from this source. Aok R.T. = room temperature. 10 Unless otherwise specified, the data were ob- B. Pu(IV)—» Pu(I) Reagents Sclution Temp. "Rate Reference Hydroquinone Dilute HNO, R.T. Rapid Ha, Pt 0.5M — 4.0 M HCI R.T. > 99% reduced in 40 min 1 0.1 M KI+ 0.4 M HCI R.T. ty)p = 2 min I-]ZSO3 8.05 M NH4HSO3, R.T. t1/2 = ~2 min 65 .3 M HNOj3 NH,OH" 0.5 M HNO, + 0.1 M R.T. ;)5 ~40 min NH3OHt NHoOH- HCL, HCI mm== | e e em e me - Zn . 0.5 M HC1 R.T. Rapid 502 1 M HNOj R.T. t1/2 < 1 min Tit+H 6 M HCI, R.T. Very rapid 235 dilute H9504 R.T. Very rapid 235 1 NHNO3 + 1 NHpSO4R.T. Rapid 103 crit Dilute HC1 or H980O4 R.T. Rapid 235, 449 Ascorbic HNO3 Rapid 418, 402 Acid 0.5 M HNO3, 0.01 M R.T. Rapid 65 Ascorbic acid 6 M HNO3 0.1 M Ascorbic acid, Fe(II) Sulfarmate R.T. Rapid 65 H902 7.5 M HCI1 R.T. Complete in several hr 145 11 C. Pu{IvV)—> Pu(VI) Reagents Solution Temp. Rate Reference NaBiQOg 5 M HNOg3 + 0.84 R.T. Complete in less than g/liter 5 min BrO, 0.1 M BrO3, 85° C 99% oxidized in 4 hr 1 M HNOg ce™ 0.1 M cet?, 0.5 M R.T. Complete in 15 min HNO3 HOC1 pH 4.5, -8.2, 8o° C Complete in 15 min 0.1 M HOC1 45% K2CO3 40° C Complete in 5-10 min H5IOg 0.02 M H5IOg, R.T. t1/2 = 100 min _ 0.22 M HNOj Mno; 1 M HNOj3, 0,001 M 25°C t1/2 = 50 min MnOJZ O3 Ce'i_3 or Ag+ catalyst 0°C Complete in 30 min 0.25 M HgS0,, no 19°C Complete in 15 hr 150 catalyst 0.25 M H9S04, no o — catalyst 65°C Complete in 1-1/2 hr 150 2 NHCI, no catalyst R.T. 2-8 hr depending on 275, 276 concentration of Pu Ag™ AgT +890g, 1.1 M 25°C Complete in 1 min HNOj3 0.5 N HgSQOy4, Solid 0 361, 39 Ag(I) Cr,Oq 0.05 M HClOy, 25°C t1/2 = 15 min dilute H3504 R.T. Complete in 9 hr 129 HNO, 0.55 M HNOg3, 98 + 1° 80% complete in 2 hr 301 1x1073 M Pu Cl 0.03 M H,S504 + B0°C t = 35 min 2 Saturated2C12 1/2, 0.1 M HCIOy4, 0.025 22°C t1/2 =2 hr M Cly 0.056 M C1” Electrolysis 0.5 M HC104 R. T. Complete in 30 min 454 12 D. Pu(VI)— Pu(IV) Reagents Solution Temp, Rate Reference HCOOH HNOq R.T. Slow Cg0g 0.02 M HCy04 75° C tj/p = 60 min 1 23MHI, 3.1 M ? Rapid HNOj3 ++ i Fe HCl R.T. Rapid 2-6 M HNO3, 1 M R.T. Rapid 75 Ferrous Sulfamate _ 2-4 N Ho504 R.T. Fairly fast 361, 39 NO,, HNO, ? ? 96 H202 HNOg R.T. Fast, reduction 295 continues to PU(IOI) E. PuV) —>Pu(lV) Reagents Solution Temp. Rate Reference HNOy = =m=mwmmes----—- R.T. Slow NH3OH" 0,5 M HCI, 0.015 M R.T. Slow NH3OH? F. Pul(VI)— Pu(V) Reagents Scolution Temp. Rate Reference I pH 2 R.T. Instantaneous NHoNH3 0.5 M HCL, 0,06 M 25°C ty/g = 180 min NHgNH: SO39 pH -2 25°C Complete in 5 min Fett 0.052— 2 M HClO4, 0-25°C ======-=m=mmmomo oo 301 L= The first of these is the disproportionation of Pu(IV) according to the reaction sput? + 2H,0 = opu®3 + Puos* + 4H" for which the concentration equilibrium constant may be written _ Pud? (puo} ™y (h* +4.3 u ) KC (P Table IV-7 lists K, for this reaction under similar conditions of acidity and ionic strength for different acids. 13 TABLE IV-7. Concentration Equilibrium Congtant for the Disproportionation of Pu*® in Various Acids at 25°C* + o Acid H £1.0M;u=1.0 HClOy4 9x 1073 HC1 2x 1073 HNO3 4x 107 A sto4 Very low H 5 Taken from Gel'man et a1.3 Appreciable quantities of Pu{Ill), Pu(IV), and Pu(VI) cannot exist together in H2504 solutions. These data show that strong influence of the anionic medium on the equilibrium. The equilibrium is shified markedly to the left even at these low ionic strengths by the strong complexes formed by Pu(IV). Conversely, the equilibrium is shifted to the right by lowering the concentration of the acid and complex forming anion, atleast until the onset of hydrolysis at pH 1-1.5. The hydrolytic reactions again stabilize Pu(IV). The disproportionation reaction probably occurs as a series of bimolecular reactions. According to Connick and McVey,lOO the reaction path may be 2Pu** = pu™ + Puo,’ (Slow) Puog + Pu+4 = Pu02++ + Pu+3 (Fast) The firet reaction is slow because Pu-0O bond formation is involved, while the second reaction only requires electron transfer, The rate of the first reaction is second- order in Pu(IV) concentration and inverse third-order in H+ concentration, The fallowing reaction sequence is consistent with these discrepancies Pu** + H,0 = PuoH™ + H PuOH" + H,0 = Pu(OH), " + H' PuOH" + Pu(om), " = Pu™® 4 Puoy + H0 + H C1"ocker'106 determined the relative armount of c_eacfi oxidation state present over a wide range of temperature and HNOg concentration, He found that the minimum concentration of HNOg to prevent formation of Pu(VI) in a 4 X 1073 M Pu(IV) solution is 1.5 M, while at 98°C the required concentration of acid is 8 M. The gecond impartant equilibrium is the disproportionation of Pu(V), which is unstable in moderately acid solution with respect to the reaction 2 Pu(V) = Pu(IV) + Pu(VI) 29 Connick™" describes this overall reaction as proceeding by either of the two slow reactions (a) 2 Puol + 4t = putt ++ 9 + PuO2 + 2H20 (B) Puo, + Pu*® + 48" = 2Pu™ + 2H,0 2 14 followed by the fast reaction (C) Puo;r + putd - Puo;‘* + put3 Reactions A and B involve the breaking of Pu-O bonds, while C does not., HReaction A is probably only important until sufficient Pu*3 is formed for reaction B to occur, since B is kinetically more probable than A. These disproportionation reactions may be involved in oxidation-reduction reactions by other reagents. Instead of direct oxidation or reduction, the disproportionation reaction can occur first, followed by direct oxidation or reduction of the appropriate product. C.4 Radiolytic Reduction of Pu Solutions The alpha particles emitted in the decay of Pu239 um to decompose solutions of Pu239 by radiolysis. The radiolysis products then oxidize supply enough energy to the medi- or reduce the Pu, depending on the nature of the solution and the oxidation state of - the Pu, This effect was first described by Kasha and Shelin(-.-215 who noticed 0.6% reduction of Pu(VI) to Pu(IV) per day in perchloric acid salution which was independent of acidity over a range 0.1 to 2 M. The rate of reduction in HCl was considerably less. In both cases the reaction is slow enough to allow the equilibrium quantities of the various oxidation states to be present. The reduction of Pu(VI) probably proceeds first to Pu(V), and the lower states obtained by disproportionation of this ion. Rabideau rates of HC1O4 and HCl reduction and found that the situation is complicated by the 21_3 26 confirmed the above qualitative results concerning the relative production of Cl~ in HClO4 solutions and Clg in HC1 solutions, Also, if Br is added to HC1O4 solutions, a net oxidation instead of reduction occurs if the mean oxidation number is initially approximately 4, ~ 308 Pages 309 and PageE and Haissinsky found that the rate of reduction depended very strongly on the nature of the anion in a study of external gamma-radiation induced reduction of Pu(VI). The rates of reduction decreased in the order ClOZl= ¥ SOZ >Cl > NOS—. These results presumably also apply to auto-reduction by alpha particles, Popov et 53.1.320 on the other hand found only oxidation by irradiation of HNOg . solutions of Pu with external x-radiation, . The rate of oxidation decreased with an increase of NO3_ and total acidity. The lesson to the radiochemist is clear: The stated oxidation states of old Pu salutions, particularly low acidity HClO,4 and H,50, solutions, should be viewed with suspicion. C.5 Hydrolytic Reactions of Plutonium Pu in all of its oxidation states exists in aqueous solutions as highly charged ions and therefore undergoes hydrolysis reactions in dilute acid solutions. The tendencies for these ions to undergo hydrolysis is dependent on the charge and ionic radius. The tendency thus increases with increasing atomic number for all the oxidation states of the actinide series and in the case of Pu increases in the order PuOéH- < Pu+++ Pu(l) > Pu(VI) > Pu(V) Gel' man et al, 3 show that the anionic ligand has some effect on this series. For example, the positions of Pu(IIl) and Pu(VI) are interchanged in the case of oxalate complexes. Singly charged anions form weaker complexes with actinides generally than do multiply charged anions, The order of complex forming ability with some anions is 3>C1 >C104. CO,; > C,0, > 5O, > F~ > NO Tables IV-10, IV-11, and IV-12 list available gtability constants for complexes of Pu(OI), Pu(fv), Pu(V), and Pu(VI), respectively, which are based on the review of Gel' man et al. 3 The chemigtry of complex compounds and ions of the actinides was also reviewed by Comyns.97 Table IV-13 lists stability constants for some complexes of several actinides for comparison. 18 TABLE IV-10. Stability Constants of Pu(IIl) Iona* IJonic Complex-formation reaction ~_strength K Ref, Putd+ NO, = PuNO;2 . ' 5.8 + 0.5 Putd + 2NO, = Pu(NOa); 14.3 + 0.8 Putd + 3NO; = Pu(No3);’ ' 14.4 + 0.8 Putd + c1” = Pucit? 0.5 0.58 1.0 1,1 putd s 504'2 = PusO, 10 Putd + 25072 = Pu(sO,)." 50 4 4’2 *3 3.6 x 1011 +3 -2 _ - B Pu'” +2C,0, % = Pu(C,0,), 2.0 X 10 . 1.4 x 109 + - - Pu " + 3C,0O 2=Pu(CO) 3 2.4 % 109 294 294)3 10 4.5 X 10 +3 -2 -5 11 Pu*? + 4,02 = Pu(C,0,), 4.2 X 10 8.3 X 10° Pu™ + 4HC,0, = Pu(HC,0,),; 6.3 x 1012 - 1.0 9.1 x 1010 Putd + 4% = pyy~4 1.0 x 1021 1.0 2.3 x 1017 0.1 (1.3-3.9) x 1018 pu'd + Hy 2 = Pupy? 7.7 x 101173 g 1.0 1.6 X 10° + 1 -2 -1 +2 + Pu + -2-1-12-7 = -2-P1.12-y + H -~ +3 -3 _ -9 11 Pu + 4CGH507 = Pu(C6H507)4 1x 10 +3 -2 -9 15 Pu ~ +6C,H,0. = Pu(C,H,0,), 5% 10 + - - Pu'? + 5C,H,0, = Pu(C,H,0,). 2 - 5 x 1016 511 =|=Basel:l on the review of Gel' man et al. 3 The data are taken from this source unless otherwise specified. ke - . ) *'y 4 is the anion of ethylenediaminetetraacetic acid. =|‘3Va|.1ue|a| at zero ionic strengih. 19 TABLE IV-11, Stability Constants of Pu(IV) Complexes” Ionic Complex-formation reaction strength K Ref, Putt+ c1m = puc1t® 1 1.38 putt + 201" = PuCl, 2 0.87 putd + NO; = Pu(N03)+3 . 2.0 2.9 + 0.6 8.0 4.7 1.0 3.48 + 0.06 +3 - _ +2 Pu(NO,)™ + NO; = Pu(NO,), 6.0 0,96 +2 - _ + Pu(NO,), “ + NO; = Pu(NOy)] 6.0 0.33 + - 0 0 - - Pu(NO,) + NO; = Pu(NO,) ] ] = T = '2 - - Pu(NO); + NO; = Pu(NO,); putt + BF = Pur 3+ BT 1 1.7x 10% 2 1.1x 10% Putd + 2HF = PuF2+2+ ai”" - - putt+ 3mF - PuF, + 85" - - Pu+4+4H.F=PuF4+4H+ - - Putd + so4'2 = Pu(SO4)+2 1.0 4.8 X 10° +4 _2 0 Pu""+ 250, = Pu(s0,), - - +4 _2 -3 Pu'® + 350, = Pu(SO,), - ] Pu™ + 0052 = Pu(CO3)+2 10.0 9.1 x 1046 putt + 0204’2 = Pu(C,0,)* 1,3 X 1011%* . , 1.0 3.6 X 108 + - * Pu -~ +2C.0.% = Pu(C.0,)0 3.2 X 1020%* 204 20475 L6 - 1.0 8.3x 108 put +3C.072 = Pu(C,0,) 2 1.0 X 1027 294 204)3 ” : 1.0 2.5 X 1023 Put?t + 4,072 = Pu(Cc,0,) 4 8.0 X 1029%* 204 2044 o 1.0 3.0x 10 : 3.1 X 1027 Pu(HPO,), + (n+ 4 - 3m)H T _ ntH4-Im = Pu(PO,)_H" + (2 - m)E4PO,, - - wherem =1,2,..5andn=0,1,2,..3m 2P + H,0, + H,0 = Pu(00)(OH)Pu*> 0.5 8.8 X 10° + 3HT {brown complex) oput? + 2H,0, = Pu(00), Pu*? + 4u* 0.5 6.3 x 108 (re'd complex) 20 TABLE IV-11. (Continued) Ionic Complex-formation reaction strength K Ref, putd 4+ TP 2 pyy 0 0.1 1.58x 1024 1.4 x 1028 put? 4 S Hypy =3 Pugy +H' - Pu'? + 4c H, 0.7 = PulcH,0), " 1.7 x 1027 pu** + 6C,H,072 = Pulc,H,0,);" 2.0 x 1031 Pu+4 + A(".Ac—:a=3 = Pu(AcAc)-"3 0.1 3.16 X 1010 Pu (AcAc)™S + AcAc™ = Pu(AcAc)2+2 0.1 1.58x 10° Pu(AcAc),;t2+ AcAc™ = Pu(AcAc)y 0.1 2.51X 10° Pu(AcAc); + AcAc” = Pu(AcAc), 0.1 1.0 x 108 Putt + C,H,0, = Pu(C,H,0,)*3 - 2.0 x 10° 359 Putt + 2C,H,05 = Pu(C,H40,)52 , 1 x 10° 359 Pu™ + 3C,H,05 = PulC,H,0,)}1 - 8 x 1013 359 Put®+ 4C,H,0, = Pu(CyH,0,), - 2 x 10%8 359 pa? + 5C,H,0, = Pu(C,H,0,)7" - 4 X 102 359 NOTES: % Based on the review of Gel' man et al. 3 The data less otherwise specified, Kok . Values at zero ionic strength, % 3J.f&b]:)revia‘c:lons are: 1, 474 4 ~ is the anion of ethylenediaminetetraacetic acid. 2. AcAc” = [CH,COCHCOCH,] . 21 are taken from this source un- TABLE IV-12, Stability Constants of Pu(V) and Pu(VI) complexes* Ionic Complex-formation reaction strength K PuO, + Cl™ = Pu02010 0.67 + -9 - 4 PuO, + C,0, 2= Pu0,C,0; 3 0.05 3.3 X 107 + 2 _ - Puo.;’ +y % - puoz.,,""** 7.9 x 1010™3 0.05 1.6 x 1010 puo.? + NO. = PuO.NOT 72 9 3 oNOg + - 0 PuO,NO, + NO; = PuO,(NOg)% 36 + 0.3 PuO, 2 + C1” = PuO,C1" 1.0 1.25 0.73 % 0.07 Pu0, 2 + 2C1” = Pquclg 0.35 PuO;z +y~4 = Pqu'y-z 1.75X 101;’=3 6.9 X 107 Puol? + .02 = Puo,c.0” 1.0 4.3 x 10° 2 204 2C20, »3 5.0 X 1012 +2 ] ! 11 PuOL2 +2C,0, = PuO,(C,0,), - 1.0 3.0 X 10 PuO, 2 + CH,CO0™ = PuO, (CH,CO0)" 1.9 X 10° PuO, 2 + 2CHCOO™ = PuO,(CH4COO), 2.0 x 108 Pu02+2 + 3CH,CO0" = PuO,(CH4COO),” 2.9 X 107 +2 -2_ -2 15%3 Pu0, + 2C0, %= Pu0,(CO,), 1 X10 *Taken from the review of Gel'man et a1’ * - - - o - * ¥ 4 is the anion of ethylenediaminetetraacetic acid. *3Va.1ues at zero ionic strength. TABLE IV-13. Stability Constants of Complexes of Several Act:i.nides* Complex-formation reaction U - Np Pu Am M3+ 2C,0,72 = Me(C,0,),- - - 11.55™3 11.46™3 MeT34 4% = Mey 4** - - 21,0™3 20.6"3 Me* + C,0,% = Me(c,0, 12 8.61 8.54 8.74 - Me*t + 20,02 = Me(C,0,), 16.9 17.54 16.9 - Me*® +3¢,0,72 = Me(C,0,), 2 22.7 24.0 23.4 - Me** + 4c,0,7% = Me(C,0,),7* 27.7 27.4 27.5 - MeO," + C,0, % = MeD,(C,0,) - 5,04 4,52 - MeO," + 2C,0,% = Me0,(C,0,),? - 7.36 7.38 - MeO," % + CH,CO0™ = MeO,(CH,CO0) 2.7 3.31 3.27 - MeO,"? + 2CH,CO0™ = Me02(0H3c00)2° 5.10 5.83 6.29 - MeO, 2 + 3CH,CO0™ = MeO,(CH,CO0);” 6.41 7.90 7.36 - MeO,+2 + €,0,72 = Me0,C,0,” 6.77 - 6.64 - MeO, "2+ 2C,0,7% = Me0,(C,0,);2 12.0 - 11.5 - MeO32 +2C0;2 = MeO,(CO,), 2 14,0 - 15,0 - *Taken from the review by Gel'man et a.l.3 % _ Y 4 ig the anion of ethylenediaminetetraacetic acid. e 3Therrnod:,rn.':unic values calculated by A. 1. Moskvin, 23 D. Separation Methods D.1 Co-precipitation and Precipitation Co-precipitation and precipitation present different problemes to the radiocchemist because, in general, the insoluble compounds of Pu which have degirabie properties in precipitation reactions are not those formed in co-precipitation reactions. Of the and PuF, and co-precipitation of Pu(Il) 3 4 and Pu(IV) by LaF3 are analogous. Since the radiochemist is likely to have small or common reactions, only precipitation of PuF trace quantities of Pu in a relatively large volume, co-precipitation reactions are more important to him, and will be considered first. Co-precipitation Co-precipitation reactions are extremely important in the radiochemistry of Pu. Indeed, the first separation and isolation of the element was accomplished by co-precipitation with LaF,. This method has become the "classic' radiochemical method for Pu and is still widely used. The co-precipitation behavior of Np and Pu toward a number of precipitants is shown in Table IV-14, taken from the review of Hyde.16 The behavior of these elements is represgentative -of the actinides in a given oxidation state, The posgsibility of separa- tion arises when the elements can be maintained in separate oxidation states, and a selective precipifant is used. The review of Bonner and Kahn49 gives a thorough discussion of the mechanism of co-precipitation and a good review of co-precipitation data for all the elements through 1949. The co-precipitation behavior of Pu has been discussed by Leader.253 The separation of Pu by co-precipitation usually takes advantage of the afore- mentioned oxidation and reduction cycles to effect purification. The procedure may be illustrated with the carrying of Pu(III) and Pu(IV) and the non-carrying of Pu(VI) on LaF very similar to that of Pu interfere. The oxidation-reduction cycle may be repeated 3 Only those elements with co-precipitation and oxidation-reduction behavior as many times as needed to get any desired degree of purity. The use of L‘En.F:3 pre- cipitation ig also a valuable group gseparation and volume reduction step, since not very many elements have acid-insoluble fluorides. In many radiochemical procedures, LaF3 is mounted for alpha counting to 191, 83, 82, 446 Chenley et 21,83 report a 2.6 % negative bias by this determine the Pu. method because of absorption of the alpha particles in the LaF3. This bias is a function of the thickness of the counting sample and must be determined for each pro- cedure. Calcium is one of the elements which interferes with LaF3 co-precipitation, since the fluoride is moderately insoluble. One method of solving the problem of high Ca concentrations (>200 mg/1) is reported by Scheidhauer and Messainguiral.351 The Pu is oxidized to Pu(VI) and Can is precipitated away from the Pu. Following re- duction, the Pu can either be co-precipitated or separated by other means. 24 TABLE IV-14. Co-precipitation Behavior of Trace Amounts of Plutonium and Neptunium in Principal Valence States.16 Carrier compound Pu(III) Pu(lv) Pu(VI) Np(IV) Np(V) Np(VI) Hydroxides c* C C C C c Lanthanum fluoride C C NC** C C NC Phosphates: Zirconium phosphate NC C NC C NC Thorium pyrophesphate NC C NC Thorium hypophosphate C NC U(IV) hypophosphate C NC Oxalates: Thorium oxalate C C NC C U(IV) oxalate C C NC Bismuth oxalate C C NC Lanthanum oxalate C C NC NC Iodates: Zirconium iodate C NC Thorium iodate- C NC C NC Ceric iodate : C NC Sodium uranyl acetate NC NC C NC Poor*B C Zirconium phenylarsonate NC C NC C Poor NC Thorium peroxide C C Bismuth arsonate C NC i The letter ""C" indicates that the co-precipitation has been observed to be nearly quantitative under proper conditions. . e The letters ""NC'" mean that co-precipitation may be made less than 1 to 2 percent under proper conditions. : "Poor'" indicates an intermediate percentage of carrying. Co-precipitation of Pu with LaF43 is a common step in the analysis of biological 360, 349, 257, 125, 208, 53 material for Pu’ Bismuth phosphate. The carrying of Pu on BiPO4 is another of the early, widely used methods of separating Pu from U and fission products. The development 401 Like LaFj, BiPO4 carries both Pu(III) and Pu(IV) when precipitated from moderately concentrated nitric acid. A of the process is reported by Thompson and Seaborg. peculiarity is the fact that Pu(IV) is more efficiently carried than Pu(IIl}. The optimum conditions for the co-precipitation of Pu have been reported by Ada.mgon.z0 These are: 1) co-precipitation at the minimum BiPO4 solubility, 2)the absence of strong com- plexing agents, 3) slow precipitation, and 4) minimum digestion after precipitation is éomplete. In addition to being very successful in the large scale processing Pu, BiPO4 pre- 341, 415 126 cipitations have been used in general radiochemical procedures to concentrate 237 Pu from large volumes of water and to determine Pu in urine. The procedure of Rydberg341 uses the familiar oxidation-reduction cycle to effect purification. Plutonium 25 is first oxidized to Pu(VI) with sodium bismuthate, BiPO4 precipitated from 0.1 N HNOS, then reduced with ferrous ion, and finally precipitated with BiPO4. Zirconium phosphate. Zirconium phosphate is a specific co-precipitant for Pu(IV), in contrast to BiPO, and LaFg, which carry both Pu(IIl) and Pu(IV). Hyde16 describes a Np-Pu separation based on the reduction to Pu(IIl) before precipitating zirconium phosphate. 18 Other inorganic co-precipitants. Dupetit and Aten1 described the co- precipitation of actinides with thorium peroxide and uranium peroxide. All the elements were In the tetravalent oxidation state. They found, that in general, the crystal type made little difference in the co-precipitation of these elements. For example, Pu carried equally well with thorium peroxide, which has a similar crystal structure to plutonium peroxide, and with uranium peroxide which has a different structure. A mixture of Pu(Ill) and Pu(IV) has been carried on lanthanum iodate from dilute HC1 solution.293 Plutonium can be separated directly from a urine sample by co-precipitation with calciurn ammoniumm phosphate. 102,74 . Pu(IV) and Am(IIT) have been quantitatively co-precipitated with K5La(SO4)4_,15 and Pu(IV) and Np(IV) have been separated by precipitation of the Pu from solutions 1 which are unsaturated in KZSO4. The minimumn Pu solubility in this system occurs at 0.7 m.1°2 Organic co-precipitants. Zirconium phenylarsonate is a specific carrier for Pu(IV) and has been used in analytical procedures to determine the oxidation 193, 414, 227 and to separate Np and Pu after reduction with NH20H.392 King227 4 state, used 2 X 10~ the same time not oxidizing the Pu(III). Voigt et al. N NHZOH to prevent the reduction of Pu{IV) during the analysis, while at 414 found that the precipitation of Pu is nearly quantitative from a formate buffer of pH approximately 2, and slightly less g0 from HCI solutions. Ice 22 HC1 solutions. Merz273 used mandelic acid and p-bromomandelic acid with Y(TII) to carry | got quantitative recovery in precipitations from 1 M Pu(Ill) quantitatively at pH 2-4 and above. Zirconium was used for Pu(IV) at higher acidities. The precipitation was about 85% complete at 1 M HCl and HNO‘.3 for p- bromomandelic acid, and somewhat lower than this for mandelic acid. 422 Weiss and Shipman quantitatively recovered Fe, Pu, Ce, and Pr from solution by the formation of oxine homogeneously in solution by the hydrolysis of 8-acetoxy- quinoline. _ These workers determined Pu in urine by co-crystailization with potassium rhodizonate.421‘ 374 Kuznetsov and Akimov3247 co-precipitated Pu(IV) from 3 M HNQ3 golutions with butyl rhodamine. The method is quantitative and separates from all elements except Th(IV) and U(VI). Repeated precipitations effect the separation. Other dyes were succegsfully used to separate Pu by the same procedure. 26 Precipitation Precipitation of macro quantities of Pu is necessary in many analytical and radiochemical procedures. The precipitation reactions which have been found useful in practice will be reviewed in this section. The use of various precipitates as purification steps for Pu is illustrated by Table IV-15, which gives decontamination 431 factors for Pu from Fe, Co, Zr, Mo, Ru, and Ce. As usual, Zr and Ru give the mogt trouble. TABLE IV-15. Decontamination Factors for Plutonium by Precipitation Me’chods.431 Plutonium Plutonium (II1) Plutonium (IV) Plutonium (TIT) Element peroxide oxalate oxalate fluoride Fe 50 33 10 1.4 Co 30 47 > 95 8.6 Zr 1 3.5 > 44 1.1 Mo > 140 > 13 > 15 1.1 Ru >14 > 38 | 33 36 Ce 6 1 1 1.1 Hydroxide. Both Pu(Ill) and Pu(IV) may be precipitated from mineral acid solution by sodium, potassium or ammonium hydroxide as hydrated hydroxides or hydrous oxides. Care must be taken in redissolving Pu(IV) hydroxide in acid to pre- vent formation of Pu.(].'V) polymer, by maintaining a high acid concentration during the dissolution. Once formed, the polymer dissolves very slowly in acid solutions. This subject is treated more fully in the section on polymeric Pu(IV). Fluoride. PuF, and PuFs may be precipitated from acid solution by addition of excess HF. Prevot et al.329 found that PuF3 forms a more tractable, crystalline precipitate than does PuF4. The compound is stable to oxidation if the 323 The freshly precipitated precipitate is kept slurried in the supernatant solution. compounds dissolve readily in reagents which complex fluoride ion, such as H3BO3, but if heated to 500° dissolve only with difficulty. Metathesis to the hydroxide with éodium or potassium hydroxide is another method of solution. .Tones214 found that Pu]Ei"3 was suitable for use as a gravimetric standard for Pu, at least for a period of several months. This method has not been widely used, however. It is interesting to note that PuO2 prepared by ignition of this Pu.'E‘3 at 500°C in oxygen was readily soluble in nitric acid, in contrast to the findings of other workers. This solubility is attrib- uted to the extremely fine particle size of PuO2 prepared in this work. Peroxides. Pu(IV) peroxide is formed when hydrogen peroxide is added to acid solutions of Pu(III), Pu(IV), Pu(V), and Pu(VI), because H202 can act as both an oxidant and a reductant. Pu(IV) peroxide always incorporates some of the anion pres- ent into the crystalline precipitate. It has been suggested7 that the presence of the anion is due to a more or less random placement between sheets of Pu and peroxide 27 oxygen in the ratio 1:3. If an excess of peroxide is used in the precipitation, the ratio may be lower. The extra peroxide also serves to hold the sheets together. Precipifation of plutonium peroxide has been used as a purification step for Pu 72,158, 329,425 329 from mosgt other cations and as a step in the preparation of high purity Pu compounds and solutions. This precipitation has been used to separate Pu from Am, the Am remaining in the supernatant solu‘cion,?2 and to separate Pu and U_277 In the latter procedure the Pu was oxidized to Pu{VI) by potassium bromate which served as a holding oxidant, and uranyl peroxide precipitated. Separation factors of 2-4 were cobhtained. Oxalates. Precipitation of plutoniumm oxalate from dilute acidic solution 265 The separation factors from other elements are-not so great in some cases as in the 431, 141 has been used as a concentration step before conversion to oxide or metal. peroxide precipitation procedure (Table IV-14), but the precipitate is easy to filter and work with. These compounds undergo decomposition by the action of their 134, 389, 216 own alpha radioactivity. The oxalate is decompoesed into carbonate and CO, and the CO may reduce either Pu(VI) or Pu(lV). Other compounds. The precipitation of plutonium (IV) sulfate tetrahydrate has been used to prepare a high purity Pu compound for use as a gravimetric standard 424 for Pu. obtained after five successive recrystallizations. This compound is suitably stable as - Starting with a grossly impure solution, a product of 99.98% purity was a gravimetric standard at least for 1!3--months.448 Dicesium plutonium (IV) hexachoride has also been proposed as a primary 279 gravimetric standard. The compound can be prepared by precipitation from an 8 M HCI solution of Pu(IV) by addition of CsCl in HCI. D.2 Solvent Extraction Methods The large-scale processing of reactor targets is largely done by liquid-liquid exiraction. This is so because of a combination of desirable properties of this method; for example, great specificity for U and Pu, easy adaptability to remote handling facilities, etc. These advantages are easily carried over to laboratory separations where specificity and ease of handling are equally important. A very great deal of research on liquid-liquid extraction systems for Pu has been carried out in the development of large-scale processes, and a large portion of the solvent extraction data reported in this section was taken under the spur of the seemingly never-ending quest for more specific extractants, better radiation stability, and the like. The basic data on the extractive properties of a given solvent are, of course, equally applicable in the laboratory or indfistrial situation. The general principles of solvent extraction have been put forth in the book by Morrison and Freiser,292 and in a comprehensive review by Mza.rcus.zs'ir The solvent 388 ' has extraction data for Pu have been thoroughly reviewed by Smith. Carleson written a good general survey of the processing chemistry of nuclear fuel for Pu, while .. 4580 . - . . a recent symposium contained much of interest concerning the newer extraction systems. 28 In this section the data will most often be given in terms of the distribution coefficient D, which is defined by the equation _ concentration of the solute in the organic phase concentration of the solute in the aqueous phase To save gpace, the notation "Dx” for "the distribution coefficient of species x'' will be used in the text. QOrgano Phogphorous Compounds This large and important class of extractants includes the neutral and acidic esters of ortho phosphoric acid and related compounds, the phosphonates, phosphinates and phosphine oxides. The class divides naturally into neutral and acidic compounds by the differences in extraction mechanism. The neutral compounds extract by solvation of a neutral complex in the organic phase by the phosphoryl oxygen, while the acidic compounds, in general, operate by an ion-exchange reaction to form an extractable species. Further solvation may occur in the organic phase in some extiraction systems of this type. Neutral Compounds Tri-n-butylphosphate (TBP), (C4H90)3PO, will serve as the typical compound of thig type. A complete survey of the literature on TBP extraction of Pu ig beyond the scope of this review. The more recent papers will be emphasized, although earlier project work will necessarily be included. A summary of early work on TBP has been given by Geary.m3 The physical and chemical properties of TBP 2 as an extracting agent have been summarized by McKay and Healy. 59 The TBP-nitrate system will be discussed first, followed by other aqueous systems, and finally other neutral organo-phosphorous compounds. TBP-nitrate systems. Hesford and McK.':l.},.r”B have formulated the ex- traction reaction of metal nitrates into TBP as MP +p NO, +q TBP,) = M (NOy) - q TBP,, (1) where p is the charge on the metal ion and gq is the number of TBP molecules solvating the nitrate molecule in the organic phagse. The subscript (o) refers to species in the organic phase, and species withoit subscripts are in the agueous phase. The equilib- rium constant, neglecting activity coefficients, is then =T . : +p P 14 K, = (M(NOg) - q TBP ]/ [M""] [No P [TBP )]~ (2) and the distribution coefficient = -1P q : D = K, {NOg]P [TBP |2 , (3) Under constant aqueous conditiong, and at a sufficient dilution of TBP in an inert diluent to make Eq. (2) valid, the distribution will be proportional to the éth power of 29 391 the TBP concer_ltration. Solovkin has calculated distribution coefficients for this system on a gemi-empirical basis and obtained good agreement with experimental data. Tetra- and hexavalent Pu as well as other actinides have been shown to be di- golvates in the organic phase.44 for Pu(IV) and Pqu(N03)2 the extracted complex is tri-solvated, Pu(NO3)3 - 3 TBP. The extracted complexes are then Pu(NO3)4 -2 TBP - 2 TBP for Pu(VI). Work with trivalent Pu has shown that 372 252 Laxminarayanan et al. have shown that Pu(IV) in 2-4 M HNO, is associated with an average of 2.6 nitrate ions and does not exist as undissociated Pu(N03)4 by combining solvent extraction data from several solvents. the organic phase. 170 There is direct evidence that the complexes are un-ionized in Typical data for the extraction of a number of elements at trace concentration into 19 volume % TBP 'in kerosene from nitric acid solution of various concentrations are shown in Fig. 1. The distribution coefficients riges steeply at low nitric acid concentrations because of the strong salting-out effect of the nitrate ion (Eq. 1), passes through a maximum, and then falls at higher acid concentrations. Some elements (e. g. Th and Y) pass through minima and rise again, 103 102 Np({VT) ™ Th ~ - ul(l) ./ / ~ LTI T T T T S N 102 Pu (OT) R _ [ | L 1 1 | | 1.1 | 5 10 EQUILIBRIUM 1073 0 15 HNO3z CONCENTRATION, AQUEQUS (M) Fig. 1. Extraction of mitrates at trace concentration into 19 volume % TBP in kerosene at 25°C from nitric acid solutions. Taken from McKay and Healy.2%9 The in- dividual references are: yttrium390; thorium ; zirconium M(VI) agents in 40% TBP in kerosene and nitric o> M(III)fM‘ 258,26 pe extractibility acid; after Carleson. of the tetravalent actinides increases with atomic number, i.e., Th(IV) < Np(IV)} < Pu(IV), while that of the hexavalent actinides decreases with atomic number, i.e., Pu(VI) < Np(VI) < U(VI).44 Moiseenko and Rozen281 measured the effect of temperature on the extraction of Pu(IV) as a function of nitric acid concentration and uranyl nitrate concentration (Figs. 3,4, and 5). In the absence of uranyl nitrate the distribution coefficient decreases with temperature below 5 M HNOB, while at higher acidities it increases. This effect is explained by a decrease in the equilibrium constant for the distribution reaction with temperature, with a compensating increase in the activity coefficient of Pu(IV) at higher acidities. This increase is ascribed to a decreased association of Pu(IV) with nitrate ions at higher temperatures. Shevchenko and Federov364 have studied the same system at nitric acid concentrations below 4 M with similar results. Best et_al.43 ' measured the distribution of several tripositive actinides and lanthanides from nitric acid solutions into 100% TBP. Sorme of their data are shown in Fig. 6 plotted as a function of atomic number, along with the lanthanide data of Hesford Lal.l'?'7 for comparison. The curves for the two homologous series are approximately superimposable if adjustment is made to compare ions of the same radius. This illustrates the importance of ionic radius on the chemical behavior of these elements. ' 31 1 | 5 Concentration of HNO3 In aqueous phass, M Fig. 3. Dependence of distribution co- efficient of Pu{IV) into TBP on concentration of nitric acid in aqueous phase (for 281 solutions not containing uranyl nitrate). Curve 1-20°, curve 2-30°, curve 3-50°, and curve 4-70°. 8 10 6 6 4 0.5 3 2 1 o I ] L ] | 20 30 40 50 €0 70 Temperdture,°C Fig. 5. Dependence of distribution co- efficient of Pu(IV) into TBP on temperature with a uranium content of 0.42 Min the aqueous phase. Concentration of HNO3: curve 1-0-5N, curve 2-1N, curve 3-2N, curve 4-3N, curve 5-4N, curve 6-6N, curve 7-8N, and curve 8-10N. 32 20 30 40 50 60 TO Temperature, °C Fig. 4. efficient of Pu(IV) into TBP on temperzafllre in solutions not containing uranium. Dependence of distribution co- Concentration of HNOq: curve 1-0.5N, curve 2-1N, curve 3-2N, curve 4-3N, curve 5-4N, curve 6-10N, curve 7-5N, and curve 8-6to BN. 10 O LANTHANIDES A TRIPOSITIVE ,d%flfl 02— ACTINIDES ,.,‘d HNO3Z i F : i F I.o 10 — N /o D"T R aZom 5 Y o0 HNO3 I £ o< _'cf ~ o o 10 A 10~2 Tol | | | | AmCmBRCr€ | | | 1 LaCe Pr NdPmSmEu GdTbDy Ho Er TmYb La Fig. 6. Distribution coefficientasa function of position in the lanthanide and actinide series. 43,177 o Lanthanides A Tripositive actinides The salting-out effect of non-extractable §§\8M_ 19%V/VTBP In kerosene salts on the extraction of Pu and U has re- 0% W gfl::re: g:'fl%m":‘mrh;om ceived considerable attention. 189,43, 149,52 N In[dlu“d Typical results are gshown in Fig. 7 in which \l % M Na(NO,) is used as the salting agent for D am| N Pu(Iv).44. 258 At 5 constant total nitrate con- 10 | 7 N centration the distribution coefficient decreases q2M / as the proportion of nitric acid is increased, ?7 gfl'r:: for HNQ3\\ but the distribution coefficient is always greater than that of pure HNO3. This effect | is caused by the reduction of competition for 0 5 10 TBP molecules by the lowering of the extract- Aqueous nltric acld concentration M L . . - able nitric acid concentration. Fig. 7. Effect of NaNOj on the dis- Aluminum nitrate has been used as a tribution of Pu(IV) between 19% TBP in kerosene and nitric acid solutions.44, 258 salting-out agent for Pu in several TBP ex- . 149, 165,52, 354 traction processes. Applications of TBP-nitrate systems. Many papers have been written about the application of TBP to the processging of irradiated U for Pu195, 132, 93, 148, 325, 114, 202, 365,109, 133 and U(VI) away from fission products into TBP-kerosene from nitric acid solutions, The process involvesg extracting Pu(IV) stripping the Pu into a relatively concentrated nitric acid solution by reduction to Pu(III), and finally stripping the U(VI) with water. Nitrous acid is added to the feed solution in the first extraction to stabilize Pu(l'V).'76 Ferrous sulfamate was first used as a re- ductant in the Pu stripping stage,335' 195, 132 209, 221, 67, 385, 353, 342, 38 although U(IV) as a reductant has been ex- tensively gtudied. This reagent can be generated from U(VI) and stabilized by volatile reductants, with the considerable advantage in large- scale processing plants of not introducing non-volatile materials (e. g. irom) into the waste streams, thus permitting a smaller waste volume. The behavicr of fission pro- ducts and other elements in this process has received much attention, both in the primary papers and others.BB‘ 161,431, 133, 367 A variant has been described in which the fission products, Pu and U, are successively siripped from the TBP phase by stepwise lower- . . . 203 ing of the acid concentration. TBP was used in the isolation of naturally occurring Pu.315 144,114 Anr:tly‘tical362 and radiochemical procedures for Pu based on TBP ex- traction from HNO3 have been given. An interesting application is the use of TBP in reversed-phase chromatography for - - 124, 156,157, 190 various heavy element separations, : PuflV)andPufiH)huHNo3?8° and for the separation of Pu(IIl), TBP — other aqueous systems. Tetra- and hexavalent actinides extract well into TBP from moderately concentrated HCIl solutions, while trivalent species are 33 essentially unextractable. Larsen and 0% 249 Seils measured the extraction of U and Pu into 30% TBP in CCl, (Fig. 8), and used this system as the basis of an FETTT I analytical precedure for these elements (Procedure 15, Sect. VIII). Both Pu(IV) and Pu(VI) extract better at all acidities than U(IV) and U{VI). The quadrivalent actinides have higher distribution co- (g3 efficients than the hexavalent above 5-6 M HCI, while the reverse is true at lower acidities. These authors report a digtribution coefficient of about 10_3 for Pu(IIT) and 10 for Am(III) in 8 M HCI1 under the gsame conditions. The wvalue T TTTTI] for Am is congidered more reliable be- cauge of possible partial oxidation of the Pu(III) to Pu(IV). HCIL is much less extractable than HNO3 into TBP. Larsen and Seils report D = 0.01 at 6 M HC1 and 0.12 at 8 M HC!I into 30% TBP in CC14,249 Selovkin et al. found that the extraction of Pu(Iv)into 1.1 M (30%) TBP in CCl4 appreciable. The disftribution co~ o~ 1 j 1 ] efficients varied from 0.0045 at 0.4 M 2 4 B 8 1 12 - AQUEOUS HCl CONCENTRATION (M) HClO4 to 0.9 at 6.4 MHC104. The ex- tracted complex was determined to be I TTTTI 390 T from perchloric acid was Fig. 8. Extraction of U and Pu b\g/ 30% TBP in CCI4 from HCL solutions. 24 di-solvated by TBP dilution experiments. PuIV) and Pu(VI) extract well intc TBP from trichloro- and trifluoroacetic acids.183 The distribution coefficients decrease with increasing acidity, rather than the usual increase., The distribution co- efficients for both Pu(IV) and Pu(VI) are about 4 to 5 times as great for CClBCOOH as for CF3COOH at low acid concentrations. For extraction of Pu(IV) into 30% TBP in Amsco-125 (a kerosene type diluent) fr~m an initial concentration of 0.5 M CCIBCOOH, D = 21; for Pu(VI), D = 4. The effect of addition of sulfuric acid and phosphoric acid to Pu(IV) or Pu(VI) — nitric acid — TBP systems is invariably to lower the distribution Coefficient438’ 440, 437 _ sulfuric439 — phogphoric. This effect is presumably due to the formation of unextractable sulfate and phosphate complexes of Pu. The effect is more pronounced in Pu(IV) than in Pu(VI), and at lower nitric acid concentrations. For example, making the agueous phase 0.08 M in HZSO4 lowered D for Pu(IV) from 16 to 9.5 in 4 M HNOB; in 2 M I—INO3 the corresponding decrease was from & to 1.4_437 On the other hand the lowering of D for 34 Pu(VI) by the addition of enough H,50, to 2 M HNO, to make the solution 0.1 M in stO4 was only from 2.6 to 2.2. . Sulfuric acid also decreases the extraction of Pu(IV) into TBP from HCl 441 solutions. A solution 1 M in HZSO4 lowered DPu approximately a factor of 10 throughout a2 change in HC1 concentration of 3-8 M. Other neutral phogsphorous compounds. A wide variety of organo-phosphorous compounds has been studied in an attempt tofind other extractants for Pu and U, Higgins et al. 181 working with the butyl series found the order to be phosphate ((RO),;PO) < phosphonate (R(RO),PO) < phosphinate(Rz(RO)PO) < phosphine oxide (RSPO). Thus the extracting power increases with the number of C-P bonds. 69,70 Burger confirmed this series and correlated the extracting power with the basisity of the phosphoryl oxygen as measured by the P-O stretching frequency. Burger,sg’ 70 and Petrov et al:.318 found that electronegative substituents in the alkyl chain such as Cl and phenyl strongly depressed the extraction. Sidda113 76 tound that increasing the length of the alkyl chain in the phosphate series made little difference up to 8 carbon atoms for quadrivalent and hexavalent actinides. The effect of branching the alkyl chain is to in- crease the extraction of U, Np, and Pu, but to strongly depress that of Th. This effect is atiributed to steric effects and possible tri-solvation of the Th complex at high ex- tractant concentrations. The extraction mechanism of these compounds is generally the same as that for 267 ppion- TBP, but not necessarily with the same solvation number for all elements. octylphosphine oxide (TOPQ) and tri-n-butylphosphine oxide (TBPO) extract Pu(IV) and Pu(VI) as the di—solvate.zsg’ 408 10 for extraction of several elements into 0.1 M TOPO in cyclohexane from HNO3 and HC1 solutions. Pw(IV}) and U(VI) are both extracted well (D = 4-30) from 3 M H,SO, by 0.3 M TOPO. 187 The extraction of Pu(IV) as a function of nitric acid concentration is similar to that for TBP, but very much higher, while that for U{(VI) and Pu(VI) show different acid dependencies. White and Rc-ss427 have written a general review of the The data of Martin andOckenden2%? i5 given in Figs. 9 and extractive properties of TOPO. Trace quantitieg of U have been separated from large amounts of Pu by extracting the .U with TOPO under reducing conditions from 2 M HN03.34 Table IV-16 is a compilation of data for the extraction of Pu{IV) by a large number of compounds of this type. The extraction coefficients were converted to 1 M extract- ant by using the ''square law,'" that is by assuming that the extracted complex is di- golvated in every case. The distribution coefficients were taken at 1 M HNO3 where possible, but cases in which other ions were present or the acidity was different are noted. The extractive power relative to TBP was calculated by direct comparison in the same gseries of experiments where possible, or by comparison to other TBP data taken under the same stated conditions. The conversion of the phosphine oxide datato 1 M extractant generally required large extrapolations, since the experiments were done at low extractiant concentrations. For this reason the numerical values of the distribution coefficients and the relative extractive power are only approximate. 35 1000 ' 1000 Y Ut ~py ¢ /.. *"0‘-{\%| 100 0 / g 100 \ & R 4 é- / R 0. L | P %t o 0 I L 1 1 ] 1 1 "0 2 4 6 8 10 12 14 .01 \ Hydrochlorlc acid molarlty \ Fig. 10. Extraction of metal ions from N hydrochloric _acid by 0.1 M TOPO in 0.001 1 ] ] L | * Am IIL CYC].Ohexane. 0O 2 4 6 8 10 12 14 Nitric acid molarity Fig. 9. Extraction of metal ions from nitric acid by 0.1 M TOPO in cyclo- hexane. Acidic Compounds These compounds are the mono- and di-acidic esters of phosphoric acid and related phosphonates and phosphinates. They have recieved considerable attention in recent years during the search for more versatile or specific extractants. In general, these compounds extract by an ion exchange type reaction anaslogous to chelation. In many cases the chelate compound thus formed is further solvated in the organic phase. For example the extracted complex in the extraction of Th(IV) with bis-2-ethylhexyl phosphoric acid from several acids involves the anions such as NOs_, Cl, and possibly 0104_ in extractions from the respective ar.:ids.312 Mono-acidic compounds. Di-n-butyl phosphoric acid (DBP) and bis-2- ethylhexyl phosphoric acid (HDEHP) are the compounds that have received most attention. They have been shown to be dimeric in the organic phase in a non-polar golvent such as benzene?’.loThe dimerization is presumably due to hydrogen bonding to the phosphoryl oxygen. 130 The extraction reaction can be formulated as M+P + P(HA)Z(O) = M(HAZ)P(O) + PH', (1) 36 LE TABLE IV-16. Compiled Data on Extraction of Pu(IV) by Neutral Organo-Phosphorous Compounds Extractant Extractant Nitric Acid - Pu Datl1 M Relative _— Concentration Concentration Conec. D Given Extractant Extractibility Phosphates Diluent Vol, % (M) (M) (a) (M) in Paper {b) (TBP =1.0)(c) Reference Tributyl (TBP) Kecrosene 19 (0.69) 1.0 p(d) 1,5 3.2 1.0 44 Gulf BT " 30 (1.09) T 3.0 2.5 92, 93 Kerosene 40 (1.46) T 3.5 1.6 76 Kerogene 20 (0.73) Bx107% 1,38 2.6 281 Benzene 20 (0.73) ~3.0 T 14.1 26.3 364 Mesitylene 6.4 11,9 364 Heptane 4,72 8.8 364 Nonane 5.46 10,2 364 —————— 100 (3.65) 1.0 T 36. 1.0 41 Xylene (1) 1.0 T 3.0 3.0 i 187 n -Dodecane 30 (1.09) 3.0 T 16.1 13.5 376 Dibutyl Carbon (0.5) 2 (initial) 0.0038 0.71 2.8 0.45 69 methyl tetrachloride Dibutyl-decyl Carbon (0.5) 2 (initial) 0.0038 2.3 9.2 1.28 69 tetrachloride Triigobutyl n -Dodecane (1.09) 3 T 11.8 9.9 0.73 376 Tri- n-amyl n -Dodecane (1.09) 3 T 15.6 13.1 0.97 376 Tri-igoamyl n -Dodecane (1.09) 3 T 17.8 15,0 1.10 376 Tri- n-hexyl n -Dodecane (1.09) 3 T 15.6 13.1 0,97 376 Tri- n-octyl n -Dodecane (1,09) 3 T 15,3 12.9 0,85 376 NOTES: (a) Equilibrium agueous concentrations are listed except as noted, 142 ' _ (b) Calculated by assuming di-solvation and ideality in the organic phase; i. e., DlM = DxM (E) where x is the concentration of the extractant. - (¢) Calculated by comparing to TBP under the same conditions under the same experimental conditions where possible. Other- wise the comparison is made indirectly. These cases are noted. (d) T represents tracer quantities of Pu. 8t Table IV-16. (Continued) . Extractant Extractant Nitrie Acid Pu Dat1 M Relative Concentration Concentration Cone. D Given LExtractant Extractibility Phosphates Diluent Vol. % (M) D) (2) (M) in Paper (b) (TBP=1.0){c) Reference Tri-2-ethyl n -Dodecane (1.09) 3 T 25 21 1.55 376 hexyl ' Tri-2-butyl n -Dodecane (1.09) 3 T(d) 28 23.5 1.74 376 Tri-3-amyl n- Dodecane (1.09) 3 T 18.1 15,2 1.12 376 Tri-3-methyl- n -Dodecane (1.09) T 24 20 1.49 376 2-butyl Tri-4-methyl- n-Dodecane (1,09) 3 T 22 18.5 1.36 376 2-amyl Tri-sec-butyl Amsco 125-82 (0.3) 0.5+0.5M T7.1X 5 56 3.85 187,420 Al (NO3)3 1075 Tri-2-octyl Amsco 125-82 {(0.3) 4 44 3.07 187,420 Dibutyl ethyl Carbon (0.5) 0.8 M 4,2 X 2,62 10.5 0.62 182 tetrachloride AY(NO,) -4 3’3 10 Diethyl amyl 3.76 15,0 0.89 Diethyl n -butyl 3.73 14.9 0.88 Diethyl isobutyl 3.69 14,8 0.87 Phosphonates _ 0.6 +0.1 M (d) _ Dibutyl butyl CC14 0.7’ M UOE(NO:}); T 1.23 2.2 17.3 181 CC14 0.5 2 (e) 0.0038 32 128 20,4 69 Dibutyl mecthyl CCl4 0.5 2 (c) 0.0038 29 116 20.0 69 Dibutyl decyl cCl, 0.5 2 (e) 0.0038 35 140 22,3 69 Di-n -butyl (f) 1.0 1.0 T 3.2 3.2 1.0 187 phenyl Di-sec-butyl () 1.0 1.0 T 5.1 5.1 1.6 187 phenyl (c) Initial aqueous concentration, (f) Diluent not stated, probably kerosene. 6E Table IV-16, (Continued) Extractant Extractant Nitric Acid Pu Dat1 M Relative Concentration Concentration Conc. D Given Extractant Extractibility Phogphonates Diluent Vol. % (M) (M) (a) (M) in Paper (b) (TBP=1.0){c) Reference Dibutyl butyl n-Dodecane 1.08 1,0 T 160 137 22,0(8) 375 Di-2-amyl n-Dodecane 1,096 1.0 T 53 44 14,7(8) 379 2-butyl Dibutyl methyl ~ CCl, 0.5 M 1.0 + 0,21 0.004 11.15 44.6 16.6 318 M UO,(NO,), Di-~isoamyl 7.43 29,7 11.1 methyl Di- n-hexyl 11.65 46,6 17.4 methyl . Di- n-heptyl 10.95 43.8 16.3 methyl Di- n-octyl 13.65 94.6 20.3 methyl Di- n-nonyl 24,15 96.6 36.0 methyl Di- n-decyl Y Y Y Y 21.65 86.6 33.3 methyl Y Di-cyclohexyl CCl, 0.5 M 1.0(8) +0.21 0.004 17,35 69.4 25.9 318 methyl M UO, (NO,) — 2 32 Diphenyl methyl 1.34 2.4 2.0 n -butyl 11.60 46.4 17.3 n -hexyl methyl n -butyl n- 17.85 71.4 26.6 heptyl methyl Di- n-butyl 7.58 30.3 11.3 cthyl . Di-isobutyl 7.67 30.7 11.4 ethyl v Y Y Y Y (g) Indirect comparison, i.e,, to TBP under the same stated conditions, but determined in a different experiment, o¥ Table IV-16. (Continued) Extractant Extractant Nitrie Acid Pu Datil M Relative _— Concentration Concentration Conc. D Given Extractant Extractibility Phosphonates Diluent Vol, % (M) (M) (2) (M) in Paper (b) (TBP=1,0)(c) Reference Di-n -butyl ccl, 0.5 M 1,0(e) + 0,21 0.004 8.65 34.6 12.9 318 Di-isoamyl 7.46 29.8 - 11.1 n -propyl Di-n -butyl 9,46 37.8 14.1 n -butyl Di-n -butyl 8.91 35.6 13.3 n -amyl Di-isoamyl 8.00 36.0 13.4 n -amyl : Di-igoamyl 7.69 30.8 11,5 isoamyl Di-isoamyl _ 8,92 35,7 13.3 n -octyl Di- n -butyl 1.91 7.6 2.8 benzyl Di- n-butyl 1.186 4,6 1.7 methoxymethyl Di—n -butyl 1,50 6.0 2,2 ethoxymethyl Di 2-(n -butoxy) 3.26 13.0 4,9 -ethyl-1 Di 1-methyl-2- 2,35 9.4 3.5 (n -butylcarboxy) -ethyl-1 Di 2-(n -butyl- 2.38 9,5 3.5 carboxy)- ethyl-1 Tetra-n -butyl . 6.72 10.0 _;fil?;lgl?: nate v * + + ' ¥ Table IV-16. (Continued) Extractant Extractant Nitric Acid Pu Datl M Relative Concentration Concentration Conc. D Given Extractant Extractibility Phosphonates Diluent Vol. %{(M) (M) (a) (M) in Paper (b) (TBP =1.0){c) Reference Tetra-igoamyl ccl, 0.5 M 1.0{®) + 0,21 0,004 8.45 12,6 318 methylene M UO,(NOy), Phosphinates Butyl dibutyl ccl, 0.75M 0.6 Fol 7{d) 49 87 69 181 oNU3l5 Butyl dibutyl ccl, 0.50 2 (e) 0.0038 170 510 108 69 Ethyl dihexyl ccl, 0.50 2 (e) 0.0038 200 800 127 69 Butyl dibutyl m-Dodecane 1.08 1.0 T 160 137 Phogphine Oxides Tri-n-butyl ccl, 0TS M 08+01 @ 499 888 703 181 2\NU3/5 Tri-octyl Cyclohexane 0.1 1.0 T 236 23,600 ~100'8 269 Tri-n-butyl ccl, 0.5 %fi%fl?fl% | 0.004 299 1,196 446 318 2/ tNY3)9 Tri-isobutyl ccl, 0.5 1.0 +0.21 0.004 21.9 876 32.6 318 (UO,)(NO,), Tri-butyl cel, 0.01 1.0 T 110 1.1 x 108 ~3 x 10° @) 408 Tri octyl Amsco 125-82 0.01 0.8 T 100 1,0 x 108 ~3 X 10° 187 Tri-2-ethyl- Amsco 125-82 0.1 0.6 T 200 2.0 x 10 ~6000 187 hexyl In this equation, HA represents any monoacidic ester of phogphoric acid. This equation has been shown to be correct for di- and trivalent ions, but tetra- valent ions in general show a more complex behavior. The extracted complex is some- times further solvated in the organic phase and nitrate, chloride, and even perchlorate complexes may be involved in the extraction reaction, depending on the specific aqueous conditions employed. Thus, no general reaction can be proposed which will account for all of the observed behavior. " Kosyakov Lal.238 studied the extraction of Pu(IV) and other actinides from nitric acid solutions by several dialkylphosphoric acids. Their results for Pu(IV) are shown in Fig. 11. The distribution coefficient increases as the length of the normal |. Dibutylphosphoric acld (HDBP) Dloctylphosphoric acid (HDOP) Dinonylphosphoric acid (HDNP) Didecyiphosphoric acid (HDDP) Di-2-ethylhexylphosphoric {HDEHP) o s wDw 4.0 5 o > 35 é - 30 | 2‘5 l I -1.0 0 1.0 LOG HNO, CONCENTRATION (M) Fig. 11. Extraction of Pu(IV) by dialkylphosphoric acids (0.5 M in isooctane) from HN’O3 solutiong. 238 alkyl chain is increaged from butyl to decyl, but that for 2-ethylhexyl is greater than any of these. The ndn—linearity of the slope of these extraction curves is ascribed to nitrate complexing in the extracted species. The acid dependency was determined by extraction into HDEHP from HC 104 solutions at a constant ionic strength of 1.0 and found to be inverse first power in the region from approximately 0.05 to 1.0 M HT. The Pu is probably exiracted as a hydrolyzed species at low acid concentrations. The disgtribution coefficient wasg found to vary directly as the square of the HDEHP con- - centration. The distribution coefficients for the extraction of Am(II), Pu(IV), Np(V) and U(VI) into HDEHP from nitric acid are shown in Fig. 12. The discontinuity in the Np(V) 42 Log D - | A N L . 3 -1 o 14 : } Log HNO; CONCENTRATION (M) Fig. 12. Extraction of various actinides into 0.5 M HDEHP (isooctane diluent) from HNO, solutions.238 curve at high acid concentrations is due to disproportionation of Np(V) into Np(IV) and Np(VI), both of which are more extractable than Np{V). The minimum in the Am(IT) ‘curve at high acid concentrations is probably due to nitrate complexing of the extracted Am species. Horner and Coleman187 get a different result for the extraction of Pu(IV) by HDEHP. As shown in Fig. 13, the extraction curve is concave downward with increasing HNO3 concentration using 0.01 M HDEHP in Amsco 125-82. The mazgéisitude of distribu- tion coefficients are very much larger than those of Kosyakov et al., if the second power dependence on the extractant concentration is taken into account. Another dif- ference is the decreased distribution coefficient at 0.1 M acid. Horner and Coleman ascribe this decrease to hydrolysis of the Pu(IV). Horner and Coleman prepared Pu(IV) by reduction to Pu(Ill) with hydroxylamine nitrate, and reoxidation and stabilization with sodium nitrite, while Kosyakov La'l.zsa did not state their method of preparation of Pu(IV). Dreze and Duyckaerts121 investigated the extraction of Pu(IV) by di-n-butyl phosphoric acid (HDBP) from nitrate solutions as a function of nitric acid concentration, nitrate concentration, HDBP concentration, and ionic strength. Representative results are shown in Figs. 14 and 15. These experimenters were able to invoke the known stability constants of Pu(IV) nitrate complexes to fit the various functional dependencies. They consider the extraction reaction to be +4 Pu’" + 2(NO4)” + 2(HDBP)y ) = Pu(NO,), (H(DBP),), \ + on" (2) 2(o) for which they calculate the equilibrium constant to be (1.7 £ 0.3) X 109 (m/1)2. 43 4 & 10 | T | 103 102 z[No;] - 6 M (HNOz + NaNOg) | | | 'O | 1001 | 0 HNO, (equllibrlum), M Fig. 13. Pu(IV) extraction by di(2-ethylhexyl)-phosphoric acid: effect of nitric acid and sodium nitrate concentration. @ 0.01 MD2EHPA; (O 0.1 M D2EHPA; diluent, Amsco 125-82. Plutonium reduced with hydroxylamine nitrate, reoxidized and stabi- lized with 0.1-0.5 M NaNO,,. 187 ’ Log D -20 -30 | [ | I | — -2.0 -2.5 -30 -3.5 -40 Log 2 [Hz Aa] Fig. 14. Variation of the distribution coefficient of Pu(IV) as a function of the con- centration of the dimer, (HDBP)5 in benzene.121 HNOj3 + NaNO3 = 6 M; HNO3 con- centrations: Curve 1-0.5 M Curve 4-4 M Curve 2-1 M Curve 5-6 M Curve 3-2 (2= 44 Log D -05 -0.2 (I)IO.IZ 04 06 Log [HNO.&] Fig. 15. Variation of the distribution 08 0 coefficient of Pu(IV) from nitrate solu- tions by HDBP as a function of HNOj3 concentration. @® HNOg + NaNO3 = WM HNO; + NaNOj other workers are included also. centration dependency for the same system. S T | 04 1 AR 6 M 4 M On the other hand, Shevchenko and Smelov?’m3 interpreted their results on the same system by assuming the extracted complex to be nitrate free. Early work on the Pu(IV)-HDBP- HNO, system was done by Stewart and Hicks,394 who found a strong lowering of the distribution coefficient when dibutyl ether was used as the diluent instead of hexane. HDBP has been used as the extractant in a procedure to determine py24l by extraction and counting In a liquid scintil- la‘tor.zss Kimur3225 determined the acid de- pendency of the distribution coefficients of many elements extracted from 50 volume % HDEHP from HCIl solutions. His results, in the form of a periodic table, are shown in Fig. 16 for comparison. Some results from A later similar study was made on the solvent con- 226 [ [éil--IllP'.-IllS] -1 --cl-- ~ 1PN\ % Er e a1 1 2l 2L Ll a L i Al s g Lol 3 —E G m\r e R e R S B S A s.j 5] | 4} 4t 4t 4t 4 !l | 4 i 1} 4+ L aamd b L LIS N S \QA I ::\':'\:*\:: 1L A1 vt ) fi.l -fi--lselll- -llll- lll.l }l llLl- _:.-lll- rI\ l.-h- -jlll -l‘ll-F‘.ll -rllll- i l) F‘I{‘ | 5’4:Y:.i.z.’::ss£.:_:‘°" f‘fl:' RE PeSiE S '“z::’ fg;;* MY SN e .\..::"‘:-\.; L Tk 9 r el B[ L] TR W R o R R B T e Y B e A O N I N1t —~ 11 I 1 A I cm‘:::§r-;L il ] [ I -1 I === 1L Ir ik ;‘/\4’? 3 B ] -.\ .-\ 1 1L - [ 1L 1L |- 1 1- '1 ] -lql i 1 ] ] ’ - DFP Values basing on Data of DF.Peppard et al, -=-CAB Data of CA Blaka et al. Data of T.Ishlmorl . =TI ==EN Dalaof E.Nakamura. Serubbing. 5 T 1. 1 T ™ T T ™ T TTTT --s 4 =0 R R L 4} 4k 1rDFP\IL 4} E p 4} L Pu(VI) > Pu(Ill) and the extractive power of the amines varies in the order 10° quaternary > tertiary > secondary > pr‘im:a.ry'.l87 Pu(IV) extracts very strongly :;I(g and selectively in analogy with anion ex- Th(DL )) change, Keder _Lal.zlg reported the extraction of several actinide elements from HNO3 solutions by tri-n-octylamine (TOA) diluted with xylene. Their regults for quadivalent gpecies are shown in Fig. 19 as a function of HI\T()3 concentration. Pu(IV) and Np(IV) are . much more extractable than are Th and U. These species show a second power depen- dence on the amine concentration, indicating that the extracted complex involves two amine molecules. According to Egs. 1 and 2, the extracted complex involves the M(NOs)fi= o™ . ] _ O 2 4 € 8 10 I2 14 anion and is (TOA),M(NOg)., where M is any Aqueous HNO3 Concentration, M quadrivalent actinide. No conclusions can Fig. 19. The extraction of the be drawn about the nitrate species in the quadravalent actiniéi(f nitrates by 10 v/o TOA in xylene. 21° Keder et al.219 also determined the extraction properties of hexavalent, trivalent aqueous phase, however, and pentavalent actinides as a function of nitric acid concentration, with results shown in Figs. 20 and 21. The maximum distribution coefficients for all these species is very much less than for Pu{IV) and Np(IV), indicating an easy separation of these elements from other actinide elements. For the hexavalent species, the amine concentration dependencies of the distribution coefficients were between first and second power, per- mitting no unambiguous assignment of the extracted complex. The slope of the Am(III) curve was unity, while that for Pu(Ill) was approximately 1.5. No explanation of this fact was given. 48 102 107t D D APa X Ref.(13) 1.0 m Pg (X) ¥ Np(X) e Py (IIT) oAm (1T 107! |0 0 2 q 6 8 0 12 14 0 2 4 6 8 0 12 14 Aqueous HNO3 Concentration,M Aqueous HNOy Concentration,M Fig. 20. The exiraction of the hexa- Fig. 21. The extraction of pentavalent valent actinide nitrates by 10 v/o TOA and trivalent actinide nitrates by 10 v/o in xylene.219 TOA in xylene. 219 Keder et :3.1.2]'8 determined that the extracted complex is M(NO3)62- for quadrivalent actinides and M02(N03)3- for hexavalent actinides by spectrophotometric measurements. 187 and Weaver and Horner"£20 have determined the dis- Horner and Coleman tribution coefficients of Pu(IV), Pw(IIl), and Pu(VI) for a number of amines from HNOg solutions, with results shown in Figs. 22, 23, and 24. Their Pu(IV) results for unsalted tri-n-octylamine (TOA) agree qualitatively with Keder Lal.219 and Baroncelli Lal.?’s but reach the maximumn at a lower HNO3 concentration. The other classes of amines reach a maximum at around 9 M HNOa. The effect of salting with l\TaNO3 at a constant nitrate concentration is to increase the distribution coefficient at lower acidities. Pu(IIl) and Pu(VI) show very much lower distribution coefficients with all classes of amines (Fig. 23) although Al(NO3)3 salting raises the DPu(III) to a relatively high value with tertiary amines (Fig. 24). Baroncelli 51:_3.1_.36 measured the distribution of Pu(IV) between HNO3 golutions and "tricaprylamine' (TCA, sold as "Alamine 336," a mixture of n-octyl and n-decyl-amines), with similar results. The amine was diluted in ""Solvesso 100," an aromatic naphtha. The extraction reached a maximum of approximately D = 140 at 4 M HNOS, and was strongly depressed by the presence of macro uranyl ion, which saturates the extractant. In experiments varying the concentration of the TCA the formation of the hexanitrato Pu(IV) complex is confirmed, but the slope of the log D Pu vs log TCA curve is 1.4 in the presence of 1.5 M uranyl ion. The corresponding slope for U is 1, indicating the for- . mation of a uranyl trinitrate complex. 49 104 — + W Allguat X5 In xylere \ 0 B=I0d In Amco - 8% TOA Q HB-I04 in xylens o © TIOA In Amco - B TOA J V Ditridecyl In Amaca X LA-1 in xylena 107 |- 4524 In Amco B X NBHA in xylers : & Primens JM In Amuco - 5% TDA oz Q Qx 10° - w A i a w \ Fig. 22. Pu(IV) extraction by 0.1 M amines: effect of nitric acid and o L o | sodium nitrate concentrations. , Amine clags: (Q) quaternary am- 2 ¢° '\ monium, (3) tertiary, (2) secondary, x (1) primary amine. Pu(IV) stabilized ! /\ with 0.04-0.1 M NaNOs. Amsco L g i 125-82, T]DI%'?: branched primary 2 A 2 tridecanol. I [Noa] - L [NQJ] - [HNOa] + 0.2 M NaNO, - 8 M(HMC)3 + NuNOa) [ X 4 9 x n.5lll|°|.| L 1 Jlllllll 1 1 ||ILll|Ja‘. 'Ol.zl IIIlLlII 1 1 Illlli HNOS (EQUILIBRIUM), M Baroncelli _fi?s also determined the separationfactorsfor Pu from initially 1.5 M U ion and 4 M HNO4 by amine extractions with tri-n-dodecyl amine ("tri-lauryl- amine," TLA) in an aromatic diluent (''Solvesso 100") and a paraffinic diluent (''Shellsol T'"), and found them to be similar, around 40. The TLA-Shellsol mixture had about 5% nonanol to prevent formation of a third phase by increasi'ng the solubility of the com- plex in the organic phase. Valentini flil.‘mg achieve maximum separation from U by extracting Pu from 2 M HNOs. Other work with tertiary amine nitric acid systems with generally similar results includes that of de Trentinian and Chesfiellsand Chesfie B4 on TLA extraction of TL(IV), U.(VI), Np(IV), Np(VI) and Pu(IV); I{nochZE’2 and Knoch and Lim:].ne1:'231 on tri-iso-octylamine extraction of Pu(IV), U(VI), Zr, and Ru. Bertocci42 found that, with tri-isononyl amine (TNA, tri-3,5, 5-trimethylhexylamine), the DPu(l'V) still increasing at 6 M HNO3, in contrast to work on other amines. Wilson430 found that perchloric acid is a very good stripping agent for Pu(IV) in TOA solutions. The Dp, value was 0.04, bothin 1 M HNO, + 1 M HC10,and 0.8 M HNO3 +02M HClO4. Bertocci42 found that Pu(IV) was not stripped well from TNA solutions by NHZOH- HCI solutions, in contrast to expectations. Valentini Lal.409 1 M Hy50, to strip Pu{IV) from TLA with good results. Several processes for the separation of Pu and U from irradiated U using tertiary Vs HNO3 concentration curve was used amines have been proposed. Wilson429 used TLA + 2% Octanol in kerosene to extract Pu(IV) from 4 M HNO3, and stripped the Pu by reduction to Pu(Ill) with ferrous sulfamate. Cheagne et 31.85 used the same extraction system, but stripped the Pu{IV) by a HT_'\TOB'-stO4 mixture..- Valentini et an.l.‘109 used the TLA—HNO3 gystem. 50 T¢ 0.1 M Reogents: o 8-104 in Amsco - 8% TDA o TIOA in Amsco - 8% TDA " TIOA in xylene | V 5-24 in Amsco X NBHA in xylene o Primene JM in Amsco = 5% TDA ] O~==Pu(l11) 10" gemeaPu(VI) - E2 (Pu) o 103 N o} [ HNO:3 (EQUILIBRIUM), M Fig. 23. Pu(lll) and Pu(VI) extraction by 0.1 M amines: effect of nitric acid concentration. Amine class: (Q) quaternary am- monium, (3) tertiary, (2) secondary, (1) primary amine. duced with 0.03 M ferrous su&f,amate plus 0.05 M excess sulfamic acid, or oxidized with AgO.! (Pu) EO z-z/l I [No3] = 6 N (AI(NO,); + HNO,) | | o - l_ 0 0.1 MTIOA in Amsco - 8% TDA 0 0.1 MTIOA in xylene X 0.3 MTIOA in xylene | ¥{0.3 MTLA in xylene X 0.3 M Alomine 336 in xylene ’,/ /’. 1072 // I, Unsalted HN03 Solutions 10-3 1 | 1 0.01 al [ HN03 (EQUILIBRIUM), M Fig. 24, FExtraction by tertiary amines from solutions of Pu(IM) in nitric acid with and without aluminum nitrate salting. Plutonium reduced with 0.03 M ferrous sulfamate plus 0.05 M excess sulfamic acid, — The fact that Pu(Ill) does not extract into tertiary amines has been made the bagis of 2 Np-Pu separa.tion.%'7 The Np is extracted as Np(IV) away from Pw(III) in a nitric acid solution. Winchester and Maramr:m431 made a study of the decontamination of Pu in an ex- perimental pyrometallurgical laboratory from Fe, Co, Zr, Mo, Ru, and Ce by both TBP and amine extraction. A summary of their results in terms of decontamination factors for Pu is given in Table IV~17. They concluded that the best separation of Pu from these metals was obtained in the secondary amine system and described a batch equilibration process for recovery of Pu on a 300-gram scale in a metallurgical laboratory. ' The Pu and U complexes have limited solubility in the organic phase, and separate as a third phase at high metal conceniration. The addition of a small fraction of polar constituent, e.g. octanol;, into the organic phase, increases the solubility of the extracted complex. Baroncelli i‘a_l.35 have made a study of this effect, and also of the effect of nitrous acid added to stabilize quadrivalent Pu. They found that nitrous acid can have either an enhancing or depressing effect on the distribution coefficient, depending on the nitric acid concentration, while the long chain alcohol always has a depressing effect. At equal molar nitrous acid and alcohol concentration in the organic phase, the distribution coefficient is at a maximum. Thig effect ig explained in terms of the formation of an alcohol-nitrous acid complex in the organic phase. TABLE IV-17. Decontamination Factors for Impurities in Plutonium in Various Solvent Extraction Processes. Initial Decontamination factors for{a) concentration Primary(b) Secondary(c) Tertiary(d) Quaternary(e) Element (g/1) TBP amine amine amine amine Fe 1.26 74 > 492 120 - - Co 1.86 > 300 > 31 > 80 >60 > 52 Zr 0.34 44 > 22 92 31 > h2 Mo ~0.17 > 100 > 8 > 78 >18 > 9 Ru 0.98 1.3 12 38 16 13 Ce 0.36 2.1 25 > 67 >32 > 28 Pu 60.58 -- -- -- -- -- Notes: (a) Procedure consisted of 3 equal volume extractions with 35 vol. % reagent in Gulf BT Solvent (aliphatic hydrocarbon) from 8 M HNOg3 solution (except primary amine extraction in which 6 M HNO3 was used). The secondary, tertiary, and quaternary amines had 10 vol. % decyl alcohol. The solutions were stripped with 3-1/3 volume portions of 0.1 M hydroxylamine nifrate. (b) (c) (d) (e) Rohm and Haas Company "Primene JM-T" Rohm and Haas Company ""Amine 9D-178." TIOA. Sterwin Chermnical Company '""Roccal." Maeck et a1.262 determined the distribution of a large number of elements for quaternary ammonium compounds between various aqueous golutions and methylisobutyl ketone ('"hexone"). The aqueous solutions considered were NaOH, HNO HZSO4, HC1, 3] 52 and HF. No extraction of PwIV) or Pu(VI) was found at any concentration of HZSO4, NaOH, and HF. The results for HNO3 and HCI are given in Figs. 25 and 26 as percent extractions from equal phase volurmnes as a function of aqueous acidity in the form of periodic tables. Berkman and K:a.pla.n40 found that tetrabutylamrmmonium nitrate (TBAN) added to Pu{IV) extracted into hexone caused the formation of a hexanitrate Pu(IV) species, while in the absence of TBAN the tetranitrate appears to be stable. A pro- cedure for radiochemical determination of Np and Pu based on this extraction system using aluminum nitrate as a salting agent has been developed by Maeck e_til.261 They report a better decontamination from fission products, particularly Zr, than is ob- tainable in other amine systemas. ' The quaternary amine "Hyamine 1622'" has been used to extract Pu(IV) from HNO, golutiong as part of an analytical procedure for Pu.48 Chloride Systems Pu(IV) and Pu(VI) extract well from HCI solutions by amines, while Pu(ITl) is poorly extracted, in analogy with the strong base anion exchange system. Plutonium chloride systems have found application mainly in analytical and radio- chemical work rather than in processes because of the corrosive properties of HCl solutions. Keder2 and U from HCI solutions into tri-n-octylamine (TOA). The dependence of the 17 measgured the distribution coefficients of tetra- and hexavalent Pu, Np, distribution coefficients on HCI concentration is shown in Figs. 27 and 28. In every case, the slope of the log D vs log TOA concentration curve is near 2, indicating that the extracted complex has two TOA molecules for both valence states. Pu(IV) is much more extractable than is Np(IV) and U(IV) under the same conditions. The hexavalent actinides are more extractable than the tetravalent in this system. Shevchenko Lla.l.366 . distribution coefficient was approximately 0.005 for Pu(Ill) extracted into 20% TOA in obtained similar results for Pu(IV), and found that the xylene. Moorezaz’ 283 extracted tracer Pu(VI) with 5% tri-isooctylamine (TIOA) in xylene from 4.8 M HCI, using 0.01 M potassium dichromate as a holding oxidant. Niobium and ruthenium extracted to some extent, but separation from these elements is possible by scrubbing with 5 M HC1 and reductive stripping of the Pu. Th(IV) or trivalent and lower speices did not extract. The tri-laurylamine (TLA)-HCl system has been used to separate Pu(IV) before spectrographic analysis of other elernents.234 Sulfate Systems Shevchenko and Zhdanova'73 investigated the extraction of Pu(IV) from HZSO 4 solutions by TOA. They showed that the extracted complex contains 2 amine molecules., The sulfuric acid dependence from 0.1 M TOA is shown in Table IV-18. The decrease in the distribution coefficient at low acidity is ascribed to Pu(IV) poly- merization. As the acid concentration is increased, the decrease in D is ascribed Pu(IV) to the formation of an amine bisulfate complex. 53 ' HI EXTRACTION )96% ! r i % é NOEXTRACTION <1 % L 8 €I N- e r 515- L [ 80| - 5 HNOy SYSTEM L | . L N |} Mg o OFTEYY o Al o P 5 e[ N HNO, -\'n fi'ty . X c # [[ B v &'L"" E['? T'E\B'E‘TH'E“H'E L r X I dk b < 1F - o . L&#L&Lfi& ety (SN - | S | S ] :"--T\ ) } L " . | L L P L " LR E T w LE R AL\ it \ =~ \ —~J} t k \\_ ") " s | wmeed | - . “[f;;"&, *...a;,~[::_}'"~.£;¥_¥_n 2|l 1t L _--LL *eaanar R o -‘ . e, | Lo o Fr Ra |} A ’1-.! ,:-b‘ 1|I'.ll'-.':u:\ +r=- ey l..' :' —— (M4 N I f . - ——— (Butyl), N [ f 7 (Propyl) Nt L - ) T I3 ,P‘?—"’ ’_‘.'-‘f"' =/ /Y || T opyly = - CPP-8-1TOB Fig. 25. Extraction of elements as tetraalkyl amine complexes from nitric acid.262 r HI EXTRACTION )>98% [ | L Qe 5 w00 NO EXTRACTION < % B c it w 0 I x). = oy . B . N i = HCI SYSTEM 3 5 ) h-.--"-. L r L Nlfl L Mg » “oirzden - Cr IAI{ s | P : 5 Mt - Non:tg.m = . - r’\ I’.- [ e ¢ [FTNIE | el ' [ "‘ gt o8 0 42 2 . fi -~ \\ r—\\‘ - }' --._. oIEEX ,f! ; § o YUY AR R FR | il .,'A__. i X o s ';,:— \ ' e o't o [ TR B | ¥ |l X T T R.E\' = ) ———— (Butyl)y Nt eleusdden (Prop,l)4 N+ —oPr——rr o Fi .6%6. Extraction of elements as tetraalkyl amine complexes from hydrochloric acid. 54 106 —a 103 102 E 3 : R - > - 104L /A 1102 - A ; I af ’ 10 03, o : o2} 1.0 - - e U (V) A - /}Z Do - B Nplvi) 10 E / {107 - A Pulvl) .o fl / 4102 — p 3 10~k A :_ Io_l - - |0_3 ™ F o uliv) K - - B Np(IV) 3 n - o PU“V) - 10™2L J10-4 102 l | | ] | F 3 o | 2 3 4 5 6 7 B8 9 |0 - . M HCI -3 ] 1 | L 10-3 10 O1 234 5678 910 M HCI _ Fig. 28. Extraction of hexavalent U, Np, and Pu from HCI solution with 1.0% Fig. 27. Extraction of U(IV) and TOA in xylene.217 Np(IV) by 10% TOA and Pu(71'V) by 1- 0% TOA from HC1 solutions.?21 TABLE IV-18. Dependence of the Distri- Vdovenko et al.412 investigated the bution Coefficient for Pu(IV) Between Aqueous Sulfuric Acid and Tri-n-Octyl- extraction of Pu(IV) by a mixture of 7 to amine.373 9 carbon primary aliphatic amines dis- H2SO4 Concentration solved in chloroform. They determined at equilibrium D that the extracted complex involves 4 (M) Pu(IV) amine molecules, i.e. (RNH3)4PU(SO4)4. 0.01 11.3 , S by the amine concentration dependence 0.037 15.2 . - 0 method, and by direct macroscopic A1 43 3 g 2 measurements of the stoichiometry of the 0.32 i8. 3 reaction. From comparisons of the ad- .88 0.415 ] . sorption specira in the aqueous and 2,44 0.008 organic phases, they conclude that the (a)Initial TOA concentration 0.1 M, Pu(IV) Pu(IV) exists primarily as a neutral sulfate concentration 2.34 X 1074 M. - complex in the aqueous phase. Therefore, they conclude that in this case the anion exchange process does not operate. Extractions from mixtures of H2504 and HNO3 proceeded by the formation of the gsame amine Pu sulfate complex above, but the distribution coefficient decreased with increasing HNO3 concentration because of the formation of arnine nitrate complex. This effect is illustrated by the data in Table TV-189. 55 TABLE IV-19. Distribution Coefficients of Pu(IV) from H2504 Solutions into Primary Amines as a Function of Increaging HNO, Concentration. 2 Concentration of HNO4 (M) 0 0.05 0.10 0.20 0.30 0.50 0.90 1.50 Dpy(rv) 66.3 63.3 50.1 14.6 2.08 0.11 0.01 R *Amine concentration 0.06 M, HQSO4 concentration 0.2 N. By contrast, Horner and Coleman187 get a third-power dependence on amine con- centration for extractions of Pu(IV) from H2804 solutions by primary amines. They also determined distribution coefficients for Pu(IV) of several secondary and tertiary amines. Their results are shown in Fig. 29, showing the successive lowering of the distribution coefficients in going to more complex amine types. They report variable 104 /Prlrneno JM/Amco~ / TDA, 3 M H,SO, 103 L Primena IM/xylens, 0.5 M H,SO 2.0 M (NH).SO 4 %4 / 102 . . i 0> / 873 M 5O, pH~0.7 Fig. 29. Extraction of Pu(IV) NBHA/Amco from sulfuric acid and acidic —3 M Hy50, sulfate solution by primary, sec- ondary, and tertiary amines. Diluents: xylene, Amsco 125-82, or 95% Amsco 125-82-5% MN-benzyl-1-undecy|-lauryl/ /Amlflo, 3 MH2504 3 M SO, pH~0.7 Ditridecyl/Amsco-TDA, tridecanol. For primary amine 3 M H,S0, extraction, Pu reduced with & hydroxylamine sulfate, reoxidized i ' and stabilized at (IV) with 0.5 M Amine 5-24/Amco, 1 - = Aamun;o4, p/|-| -?7 NaNOQOsg. Others stabilized at (IV) with 0.1-0.5 M NaNO,.187 Tri-Im~octyl/Amsco, °3 Mso‘r pH~ 0.7 l 1 I 1 0.001 0.0l 0.1 | 10 AMINE CONCENTRATION, M distribution coefficients for Pu(IIl) by primary amines from sulfuric acid solutions, ranging from ~5 to >> 100 with 0.1 M amines. This behavior is attributed to partial oxidation of Pu(III) to Pu(IV), even in the presence of holding reductants. These authors propose a process for recovery of Pu from sulfuric acid decladding 3 . I . 188 solutions based on primary amine extraction. The primary amine- sto system has been used for determination of Pu in biological material, e.g. urine or solution of bone ash. 61 56 Other Systems Moore285 found that the hexavalent actinides U(VI) and Pu(VI) could be quantitatively extracted from 1 M acetic acid solutions and 1 M acetic acid — 0.1 M nitric acid solutions by 5% TIOA-xylene. Of the fission products only Ru, Zr, and Nb extracted appreciably, and these could be scrubbed with 5 M HCl. A preliminary ferric (or uranyl) hydroxide precipitation in the presence of niocbium carrier improved the decontamination from these elements. The U and Pu were leached from the insoluble Nb205 with 1 M acetic acid. The uranium could be stripped with dilute I—l'J.'\TO3 or HCI, NH4OH or ammonium bicarbonate. The Puw(VI) could be stripped by these reagents or reductively stripped, since Pu(IV) and Pu(Ill) do not extract under these conditions. Alcohols, Ketones, Etherg, and Amides These compounds have in common the fact that they contain a basic oxygen atom which can solvate a proton or metal atom. This type of extractant was once very popular, but the newer organo phosphorous compounds and amines have received more attention in recent years. Nevertheless, they are still important in laboratory and process separations. Indeed, one of the large-scale processes for the processing of irradiated U, the '"redox' process, uses methylisobutylketone (MIBK or "hexone'’) as the primary extractant for U and Pu251 as do several laboratory procedures. The extractive properties of the ethers for U, Fe, and other elements have been known for many years. Nitrate systems have received by far the most attention as extraction media for Pu. Both Pu(IV) and Pu(VI) are extractable at high nitric acid concentrations, or at moderately high nitrate concentrations provided by a salt such as aluminum nitrate. Pu(IIl) is practically inextractable at any nitrate concentration. The extracted species depends on the aqueous phase composition. It has been shown that, for example, the extraction of Pu(VI) from nitric acid solutions by dibutyl carbitol (DBC, the dibutyl ether of diethylene glycol) the extracted species is the neutral plutonyl dinitrate at low nitric acid ( < 0.8 N) is a mixture of dinitrate and trinitrate at intermediate acidities (0.8-3N), is predominately trinitrate at higher acidities (3-6N), and finally is more complex than irinitrate above 6N. 171 At these higher acidities the extraction must in- volve the solvation of a proton to form the species H(DBC)2 Pu(NO3)3, rather ‘;}éa}rn direct solvation of the Pu in the case of the extraction of the dinitrate sgpecies. from 1.5 M HNOS and as HzPu(NOg)6 245, 246 Similarly, Pu(IV) extracts into hexone as Pu(N03)4 at 6 M HNO3, with intermediate composition of the organic phase in between. The species extracted into triethyleneglycol dichloride at high nitrate concentration have been found to be H2Pu(1\703)6 for Pu(IV) and H Pqu(NOB)3 for Pu(VI).7Ei Dibutyl ether behaves similarly. 413 - Pu extraction by hexone has received the most attention, undoubtedly because of its use in processing. The extraction of Pu(IV) and Pu(VI) as a function of nitric acid concentration and the concentration of various salts has been measured by several groups. 57 0 | 0.0l D Q.00 D, _<0.00I Cu< 0.000I DNU_O.OOI La g g a1 0.0000I I 2 3 2 5 e M HNOj; Fig. 30. The distribution ratios of T, Pu(IV) and Pu(VI), Th, Zr, Ce(IV) and La into hexone as functions of the equi- librium concentration of HNO4q in the aqueous phase. The Ce(l‘Vj curve is taken from Glendenin et al.14 Py WI’,u(lV) o T III"I T A \J D Q. - 001 - Ca 0.001 E % . i Dyg < 0.001 1 L L L ] ] | 1 ] 1 00001 I 2 3 4 5 6 AQUEOUS HNO5 CONCENTRATION (M) Fig 31. The distribution ratios of U, Pu(IV) and Pu({VI), Th, Zr, La and Ca intc hexone ag functions of the equilib- . rium concentration of HNO4 in the aque- ous phase. Concentration of Ca(NOg)y 4-3.5 M.343 58 343 measured Rydberg and Bernstrom distribution coefficients for several elements including TU(VI), Pu(IV), and Pu(VI) as a function of nitric acid con- centration both with and without calcium nitrate as a salting agent. Typical results The effect of salting with Ca(NO3)2 is to raise all the are shown in Figs. 30 and 31. digtribution coefficients, but at low acid those of U and Pu are high enough to be efficiently separated from other elements. MacKenzie?®? extended the distribu- tion curves to higher aqueous acidities for Puw(IV) and Pw(VI) as shown in Fig. 32. This curve was replotted from MacKenzie's original data by Smith388 because the original was reported in terms of organic phase acid concentration. The conversion to aquéofi"s'- phase original acid concentration wag made by using data on nitric acid ex- traction by hexone. Both Pu(IV) and Pu(VI) pass through maxima and decrease above approximately 7 M acid. A salting agent, e. g ALNO,),, 271 193 ca(NO,),,343, NH4NO3260 increases the distribution co- efficient. A useful comparison of various galting agents for Pu(IV) into hexone was reported by Stewart3 23 (Fig. 33). The salts increase in salting effectiveness at high total nitrate concentration in this order: ammeonium, lanthanum, nitric acid, mag- nesium, aluminum, and mangafiese. A similar comparison for Pu(VI) into diethyl ether was made resulting in this order: ammonium, calcium, lanthanum, nitric acid. Kooi236 found that .the distribution curves for extraction of Pu(IV) and Pu(VI) into hexone did not decrease at high HINOg4 concentrations, in contrast to other workers. His distribution coefficient for Pu(IV) reached the maximum value of approximately 7 at 8 M initial HNOS o AR R D 0.1 Pu(vI}(d Pu CONCENTRATION 2 2 mg/mi " " #" , Dadjusted PullV) ® Pu CONCENTRATION= 2 mg/ml v " #Fuon yD adjusted 0.0l ~ _1 | I | | | 0.00l 0 2 4 6 8 10 i2 14 INITIAL AQUEOUS HND3 CONCENTRATION (M) Fig. 32. Distribution of Pu(IV) and Pu(VI) into hexone from HNO4 solu‘cions.260 concentration. MacKenziezs0 found that the distribution coefficient for both Pu{IV) and Pu(VI)} in nitric acid increased in the range 0.01-2 mg/ml, while Groot Lal.153 re- port no dependence on Pu concentration from 0.00003 to 0.5 mg/ml for the extraction of Pu(IV). Groot et al.!®3 either 0.03 M Na,Cr O, or 0.3 M sulfonic acid. These reagents are commonly used 271 as oxidizing and reducing agents in redox processes. Rider et al.332 has used hexone in a also find that the distribution coefficients are not affected by laboratory procedure to determine Pu and U in reactor targets. Other Aqueous Systems Stewart393 reports on the comparative extraction of Pu (unspecified initial valence) by hexone from hydrochloric, nitrie, sulfuric, and acetic acids under various conditions (Table IV-20). Plutonium (presumably a mixture of Pu(IV) and Pu(VI)) extracts well from 8 N HCI, but not from H2504 ig very low under reducing conditions for all these acids. or acetic acid, while the extraction 59 100 90 B8O Fig. 33. Effect of total nitrate ion concentration on the extraction of Pu(IV) by methyl isobutyl TO 60 PERCENT Pu(lV) EXTRACTEDBY EQUAL VOLUME METHYL-ISOBUTYL KETONE ketone. 393 50 Curve No. Aqueous Phase II 1IN HNOj3 + NH4NOg III 1N HNOg + Mn(NOj3)g 30 IV 3N HNOg3 + Mg(NO3)y, POy--- v 3N HNOg + A1(NOg)3, POy4--- 50 VI 1M HNO3 + La(NOj)g 10 0 | I L 11 0O | 2 3 4 5 6 7T B8 9 101 12 TOTAL INITIAL NO3 CONCENTRATION IN AQUEOUS PHASE Other Extractants Stewartag3 compiled a table of extraction data for a large number of ethers, alcohols, ketones, etc. for Pu in the tri-, quadri- and hexavalant oxidation states from ammonium nitrate-nitric acid mixtures. These data are reproduced in their entirety as Tables IV-21, and IV-22, to show the variety of compounds tried and to indicate the types of compounds which are efficient as Pu extractants. In general, the ability of these compounds to extract correlates with the basicity of the oxygen, nitrogen or other functional group. Thus, electronegative substituents in- variably decrease the extractibility of Pu (see e. g. diethyl ether vs dichlorodiethyl- ether). TABLE IV-20. Distribution of Pu Between Various Aqueous Phases and Hexone.393 Distribution Coefficient for Extraction from 8 N Acid Composition of Aqueous Layer HCI HNO, Hy50, CH3COOH Acid only 10 8.3 0.06 0.012 0 0.33 3.3 0.005 ----- Acid + 0.7 M UOz(NOS)z IEFH2 Same, saturated with 802 0.0012 0.2 = m==e- —=eea Same, as 2 + 0.06 M hydroquinone 0.0033 -——— mm——= meeee B W N o~ 60 TABLE IV-21, Volume of Various Organic Solvents. Extraction of Plutonium from 10 M NH4NO3, 1 M HNO3 by an Equal % Pu % Pu extracted extracted Solvent (II1)* (IV) (VI) Solvent (II)* :(1v) (VI) Ethers-Cellosolves Acids - Esters Diethyl ether <1 <1 50 2-ethyl butyric acid <1 5.7 - N-propyl ether <1 4.8(?)2-ethyl butyl acetate <1 1.5 - Di-isopropyl ether 7 Ketones Allyl ether 4 - m ethyl ketone N-butyl ether 1 1.5 15% Xylene <1 79 - Hexyl ether <1 1 1. Methy n-amyl ketone <1 52 - Ethylallyl ether 2 - Methyl isobutyl ketone Ethyl-n-butyl ether 1 (Hexone) diethyl ether (DEE) > hexone, while for Pu(VI) the order was DBC > hexone > DEE. Branica and Bona54 found that U(VI) and Th extract at a lower HNO, concentration with several cyclic ethers (e. g. TABLE IV-23. Distribution Co- tetrahydropyran) than with diethyl ether or efficients for Pu(IV) Extracted by Various Ketones from 3.2 M HNO3.245 hexone, and these results are presumably applicable to Pu also. Distribution A number of other process applications Ketone coefficient ) of this class of extractants are worth mention- Methyl-n-propyl 10 L ; dib diethvleth ing at this point. 8,8' - dibutoxydiethylether Methyl-n-butyl 2.2 g P 8.8 yeethy ) ("Butex') has been used as one of the ex- Methylisobutyl 1.6 tractants, along with TBP in a two-solvent Methyl-t-butyl 0.12 process for purification of Pu and recovery Methyl-n-amyl 0.62 450 188 : of U at the Windscale power reactor facility. : Methyl-n-hexyl 0.22 The quoted advantages over hexone are (1) Di-n-propyl 0.12 sufficient resistance to attack by high con- Ethyl-n-butyl 0.23 centrations of HNO3 to permit use of the acid as a salting agent, and (2) superior separation factors of Pu from U. TBP is used as the second extractant because it gives superior decontamination of the Pu from Ru. Vdovenko and Kovalskaya.411 used a mixture of dibutyl ether and carbon tetra- chloride in a Redo-type process with satisfactory results. Dibutoxytetraethylene glycol (''pentaether') has been used as an extractant,lso along with a 50% pentaether-50% dibutyl ether 1'nixtur<-:-.28 Sidda11377. 378 for tetra- and hexavalent actinides. The carbonyl oxygen in these compounds has en- has pioneeredthe use of N, N disubstituted amides as extractants hanced basicity because of the presence of the amido nitrogen, and therefore should be analogous to the neutral organo-phosphorous compounds in extraction properties. Typical results for a number of elements and amides are shown in Fig. 34 and Table IV-24. He found that U(VI) behaved similarly to the phosphorous compounds (e. g. TBP) in that the extracted complex involves two amide molecules. However, the quadrivalent species (Pu, Th, etc.,) are extracted with more than two amides per 63 ¥9 TABLE IV-24, at 3 and 6 M HNO, (Ref. 379).% Extraction of Actinides and Zirconium by Various N, N-Disubstituted Amides — 3.0'M HNOj4 in the aqueous phase — —6.0M HNO3 in the aqueous phase—— SExtraction coefficient is defined as moles/liter in the organic phasge divided by moles/liter in aqueous phase. bA]_'l 0.50 M in toluene. b Pu Pu- Np- U- Np- Amide u(viy (av) (V) Np(IV) (VD) HNO; (VD) PuV) (IV) Th Zr HNOq N, N-Dihexylformamide 4,1 2.4 0.119 3.6 4.0 0.10 0.54 0.090 N, N-Dibutylacetamide 9.9 21 138 6.4 38 .74 .21 .102 N, N-Dibutylpropionamide 4.5 3.5 112 4.5 7.2 .11 .044 .094 N, N-Dibutylisobutyramide 2,4 0.080 0.23 0.024 1.2 .103 3.3 0.21 0.070 .0040 .0026 ,083 N, N-Dibutylpivalamide 0.60 0.0009 .051 0.33 .057 1.4 0.0048 .0001 <,001 .060 N, N-Dibutylbutyramide 5.3 . 4.0 .63 1,0 3.4 114 4.7 8.7 2,2 085 ,039 .095 N, N-Di-isobutylbutyramide 5.1 3.5 0.48 0.62 3.0 .108 4.8 7.1 1.6 .028 ,046 .088 N, N-Di-isobutylisobutyramide 2.0 0,057 0.0070 100 3.1 0.11 0,037 .0010 00,0012 .085 N, N-Dicyclohexylformamide 9.4 9.9 .150 4.8 11 .21 1.1 .100 N, N-Dicyclohexylacetamide 14 11 2.2 .142 8,3 16 .68 0,026 ,091 N, N-Dicyclohexylbutyramide 7.9 1,7 .148 5.1 2.9 .16 .010 .103 - N, N-Dibutyl-2-ethylhexanamide 4.0 0.19 125 4.1 0.29 .0043 .0022 .094 N, N-Dimethyldecanamide 4.9 10 115 4,4 39 .63 096 ,091 N, N-Diethyldecanamide 5.1 6.9 .120 5.0 16 .34 049 .096 1-Hexanoylpiperidine 7.2 B.7 .115 5.8 20 .32 077 .096 1-(2-Ethylhexanoyl)-piperidine 2.8 0.60 .087 4,2 1.5 .025 .011 ,080 N, N-Di-sec-butylhexanamide 5.5 .90 120 4,0 3.9 .092 ,0092 .0%4 N, N-Dibutylcyclohexanecarboxamide 3.1 .19 103 4 1.0 .0040 ,0034 .090 N-Butyl-N-phenylbutyramide 1.4 .23 .088 2.4 1,3 .0033 .0099 .085 N, N-Dibutylberizamide 0.86 .34 105 1.2 0.69 .0099 ,0070 .088 N, N-Dibenzylacetamide 3.3 0.22 0.077 4.3 1.0 0.014 0.021 0.077 metal atom at high nitrate concentrations. Zr exhibits a maximum distribution co- efficient at about 7 M HNO, and decreases at higher acidities. A large decrease in the distribution coefficient of quadrivalent Pu and Th occurs as the branching of the alpha carbon atom is increased, while that of U(VI) is only decreased moderately. N, N- dihexyloctanamide was superior to TBP in decontamination of Pu from Zr-Nb, but slightly inferior for Ru decontamination. The potential uses of these compounds are (1) as selective extractants for quadrivalent actinides, or (2) as selective extractants for U(VI) in the case of amides with highly branced alpha carbon atoms (e. g. N, N- dihexyltrialkylacetamide). Chelating Agents A large number of bi-functional reagents which form strong coordination complexes with metal ions have been investigated. These complexes are more soluble in non-polar organic selvents such as benzene or carbon tetrachloride than in the aqueous phase, and are therefore extractable. Of these compounds the fluorinated / B-diketone, 2-thenoyltrifluorc acetone (TTA) and 100 the ammonium salt of N-nitrosophenylhydroxyl- amine (''Cupferron') have been used most widely T in radiochemical and analytical applications. uivn Thenovyltrifluoro acetone {TTA) S This compound has the structural i) O L) 8 e, S formula FTTTTIT] Th{lv) and exists primarily in the enol form in both aqueous and organic solutions. TTA forms strong complexes with many metal ions, particularly those of high valence. T T ITTT] The general reaction for the extraction can be written as +m + o /¢ M +mHT = MTm(o) + mH (1) 0.l (o) ~ and the equilibrium consgtant T TTT +,m LM, ) g — (2) (M+T™ (HT)IE:)) 0.01 g L GL B where the quantities in parentheses are activ- HNOz CONCENTRATION AT ities. EQUILIBRIUM (M) Thus, if activity coefficients are neglected, Fig. 34. Extraction of actinides and no aqueous complexing occurs, the distribu- and Zr by 1.09 M N, N-dibutyloctan- amide in n-dodecane at 30°.378 tion coefficient should show a direct mth power 65 dependence on the TTA concentration and an inverse mth power dependence on the aqueous acidity. This expectation is borne out for many elements, including Pu. The most comprehensive summary of TTA data is that of Poskanzer and Forema_n324 who found that the extraction data for most elements could be fitted by the equation +.x -p—HL 3) &Py g o ) HT in which K is a constant, [H+] is the activity of the hydrogen ion in the aqueous phase (HT) is the concentration of the TTA in the organic phase, x is the observed TTA con- centration dependence of the reaction, m is that of Eq. 1, and f is the organic phase activity coefficient of the TTA. For benzene solutions of TTA 0.48 228 (4) f =1-0.24 (HT) HT Equation (3) assumes that the activity coefficients of the TTA and the metal chelate are equal in the organic phase. These authors determined the parameters of Eq. (3) for all available experimental data on TTA extractiones and calculated pH50, the pH at which 50% of the ion is extracted by equal volume phases into 0.2 M TTA in benzene. They displayed some of these data in the form of a periodic table to show the trends in extractability of the elements (gee Fig. 35). In cases in which the pH50 value is negative only HCI data are given, while other data may be for a variety of acids and acid-salt combinations. The reader is referred to the original paper for more detail. However, this figure shows that the quadrivalent ions are much more extractable than others. ELEMENT H.. OXIDATION STATE — \ LIZ|jBem PHsq 2l 8 c | n\olr‘ >® ||#**] pHgy = pH. OF 50 % EXTRACTION WITH EQUAL VOLUME NEGATIVE "pH,, ° ® —LOG HCI CONCENTRATION No [l Mg . X~ COEFFICIENT OF pH DEPENDENCE OF LoG & D |AIIO(l SI P s cl = OXIDATION STATE WHEN NOT INDICATED 2.4 K Call ||SeII||l TI v Cr Mn Fe CoIl || NITT||CuIX |) Zn Ga Ge As Sa Br 6.7 Y] Lo.eami| 4.1 || > 1.38 B Rb SrJIlYIII ZrI¥|( Nb | Mo Te Ru Rh Pd Ag Cd |{{InIO|| Sn Sh Te 1 74 || 3.20 )[-1.o08 >s e Cs |[BoII |[LaTO/IHI ) Ta w Rs Os || IrTOT|| Pt Au My TI [|PoII | BIOI| Peo At 334 8.0 4.24 || -1.O >7 3331 L8O || 0.8 {3.3) 2mm z) 0.5m Fr [|ReTL | AeIdD >7 || a57 L (9 || ¢eo || PrIO|| NdIX|[PmIO 3sem| 3sa || xse || 342 SmII||[Eu IO|[\GdIX||Th L || Oy IX|[|Ho TX|| Er || TemIO|| YO IX||LuIX 3.20 (| 329 || 3.26 || 524 || 308 || 28 308 || 297 299 ThIX AmII||CmII||IBk IX ||Cf II|| E IX || FmIX|| Mv | 102 0A8 ez || 3s 0 || A a 34 —_ Fig. 35. Extraction of the elements with 0.2 M TTA in benzene.324 66 The extraction of Pu(IV) from nitric acid solutions was investigated by Cunninghame and Milesllo' 111 using CCl4 and benzene as solvents primarily, al- though other chlorinated hydrocarbons were used also. They find that, by neglecting aqueous phase nitrate complexing of the Pu, the equilibrium can be expressed by the equation 4 AHNO, 'pur, € Ppurw) 1 ;4 - %) HT® g They derive the f's from the TTA concentration dependence of.t.he distribution co- efficient, and find that C is close to 1 X 10+5 over the range from 1 to 10 M HNO3 for tracer Pu. Heisig and HiCkS,173 in a very extensive study of the kinetics of the ex- traction of Pu(IV) from nitric acid solutions by TTA, in sec-butyl benzene, determined that the rate of transfer of Pu chelate acrosa the organic aqueous boundary controls the forward and reductive back extraction rates. They find that at low nitric acid concentrations (0.5 M) the extracted species is PuT4, while at 4.9 M total nitrate con- centration some partially nitrated complex such as PuNO, T, exists. 373 174 found that for Pu{VI) extractions into TTA-benzene from Heisig and Hicks nitric acid solutions the dependencies are direct second-power on the TTA concenira- tion and inverse second-power on the hydrogen ion concentration, indicating that Eq. (1) represents the reaction. These authors measured the distribution coefficients for the Pu(IIl) obtained by reduction with 0.005 M ferrous perchlorate—-0.0l.l\_/I_ sulfuric acid as a function of nitric acid and TTA concentrations. Theyobtaineda direct 2.3 power dependency on T'TA concentrationand aninverse 2.6 power dependencyonhydrogenion. These solutions were never stabilized in the presence of TTA, however. Since the distribution co- efficient increased with time, extrapolations to time zero were made, and the extrap- olated values were used. Plots of the distribution coefficients for Pu(IIl) and Pu(VI) obtained by Heisig and Hicks are shown in Fig. 36. Cunninghame and MJLleE'.111 determined the extraction properties of 2 number of possible impurities in the development of a batch process for separating Pu from ir- radiated U. Their results are shown in Fig. 37. Their procedure, which should be easily adaptable to the laboratory scale, is to pre-extract the Zr from 0.5 M HNO3 while the Pu is reduced to Pu(Ill) with hydroxylamine, oxidize to Pu(IV) with NaNOz, extract with 0.2 M TTA-benzene, scrub with dilute HNOB, and back-extract the Pu into 8 M [-INOB. They report a 99.4% Pu recovery on a 1-gram scale with decontamination factors from Zr and U of 3000 and 667, respectively. Other reporis on the use of TTA for processing irradiated uranium for Pu are those of Crandall et al.'%® and cutler.1%? to strip Pu from TTA solutions by reduction to Pu(Ill) or a combination of reduction and displacement.342 The application of TTA to analytical and radiochemical pro- An interesting variation is the use of U(IV) cedures for Pu has been reported many times, either as the only purification step287’ 50, 356 for rapid analysis (see for example, Procedure 2, Section VIII) or in 136, 351,50, 284 BiPO,, 341, 237 332,315, 168, 261 combination with co-precipitation steps involving LaF3, chemisorption on a CaLF2 suspension,352 or other separation steps. 67 Pul{lll) ol ] L | | 0 004 0.08 0.2 0.16 0.20 HNO3 CONCENTRATION (M) Fig. 36. Extraction of Pu(III) and Pu({VI) into TTA-benzene as a function of I—INO3 concentration at constant total nitrate concentration. LiNOj added.174 Pu(VD) Pu(III) TTA conc. (M) 0,74 1,65 Total nitrate (M) 0.175 0.096 Agueous conditions 0.006 M 2 X 10-4 M KMnOy FelClOy), oZr 1000 100 \ 0.l _Tatk/ 0.0l ': y hx / J | P o 0.001 I A W2 = \vog' i PuI ‘ o.000|° | 2 3 4 5 6 7 8 % 01 12 HNOs MOLARITY Fig. 37. Distribution coefficients of various ions from nitric acid solutions into 0.2 M TTA in benzene.110.111 TTA has been used to separate a small amount of U from macro Pu,194 o . 415 vice versa, to concentrate Pu from en- r 3 352 vironmental water samples and to determine the oxidation state of Pu in environmental samples, including sea 136 water. In the latter procedure, Pu(IV) is extracted from 0.5 M HCI and the acqueoug raffinate adjusted to pH 4.3 with ammonium acetate from which the Pu(III) and Pu(VI) are extracted together. On a second sample, the Pu(IV) and Pu(IIl) are coprecipitated together with LaF are then calculated by difference. q- The relative amounts of the three valence states TTA has been used to separate Pu from impurities for a spectrographic . 411 ahalysis. In this procedure an HCI solution of the metal is reduced to Pu(Ill) with hydroxylamine and impurity elements extracted with TTA in hexone. The Pu in the aqueous phase is then oxidized to Pu(IV) and extracted into TTA-hexone. By this pro- cedure both extractable and non-extractable impurities can be determined. TTA has been used for several procedures for the determination of Pu in bio- logical material, expecially urine Procedure 21, Section VIII). 125, 349, 360, 257,56, 316 (see, for example, % EXTRACTION Cupferron N-nitrosophenylhydroxylamine or cupferron has been used as a pre- cipitating agent for many metal ions for many years, and the solubility of these complexes. in non-polar solvents such as chloroform was recognized at an early date. The extrac- tion reaction is analogous to Eq. 1, although little quantitative work has been done on Pu. Furman et al. 138 have reviewed the subject and have given data for U(IV) and U(VI). Kemp220 into chloroform from HCl-ammonium chloride solutions (g = 1.0 pH = 4.5 - 5). found that Pu(IlI) required four cupferron molecules per Pu atom in extractions He ruled out oxidation of the Pu(IlI) by the reagent and postulated an "extra' cupferron molecule in the organic phase to complete the eightfold coordination sphere. The pH dependence for Pu(Ill)from these solutions was found to be third power, in accordance with Eq. 1. The pH dependence of Pu(Ill) with and without the presence of hydroxylamine and Pu(IV) is shown in Fig. 38. Kirk and Rodden229 report that most light elements are not extracted by cupferron- CHCl and listed Fe, U(VI), U(IV). and Pu(IV) as extractable species. They report low extraction for Pu(VI), but essentially complete extraction for Pu(IIl) and Pu(IV). The extraction of reduced Pu is lowered above pH 0.8 in HZSO4. Phosphate interferes with the extraction, but a small concentration of iron is beneficial, Nigon and Pennemr:m.304 the Pu in the presence of ferrous ammonium sulfate from 1 N HCI1 solutions. 100 |- (3) 8ol (m pulim (2) Pullil)INPRESENCE OF HYDROXYLAMINE (3 Pullv) 60 40 20 1 | 1 1 1 00 ! 2 4 6 pH Fig. 38. Extraction of Pu(IIl} and Pu(IV) from 1.0 M chloride into cup- ferron-CHCl3. 220 Curve 1: Pu(IIl) = 2.16 X 10-9 M, cupferron = 3.98 X 10-2 M; Curve 2: Pu(III) = 3.65 X 10-3 M; cupferron = 3.68 X 10-2 M, 10 w/v% hydroxylamine hydrochloride. The curves are % extraction for equal phase volumes va equilibrium pH. report a separation of Pu and Am, based on extraction of The fact that the extraction rate of Pu is slowed by cooling from room temperature to 5°C suggests that oxidation from Pu(III) to Pu(IV) is taking place in the presence of cupferron. They re- port a separation factor of 10° with quantitative recovery of both Am and Pu. A similar pro- cedure has been used to separate Pu from U 417 231 has used cupferron ex- Kooi and Hallatein tractions to concentrate Pu from environmental Beaufait and Luken.'s37 corporated a cupferron extraction step in a water samples. in- general radiochemical procedure for Pu. Cupferron has been used in several pro- cedures to separate Pu before spectrographic determination of impurity elements.zgs' 45 Finally, cupferron, has been widely used in procedures to separate and concentrate Pu from biclogical rnaterials.loz’ 387,.248,272 Chmutova M.BT for determination of Pu by extraction from 3 M developed a procedure HNOg by a chloroform solution of N-benzoyl- phenylhydroxylamine (BPHA), an analog of 69 cupferron, followed by back extraction of the Pu(IV) into sulfuric acid. It was found that U, Am, Np(V), and fission products (except Nb and Zr) do not extract under these conditions. The Nb and Zr are separated in the back extraction step. Other Chelating Compounds Many organic chelating agents were investigated in the Manhattan Project for possible extractants for Pu, including acetylacetone, trifluoroacetylacetone, and various other fluoridated diketones. Stewart393 has compiled extiraction data for such compounds as well as many other complexing agents. Extraction data for several chelating agents are shown in Table IV-25. TABLE IV-25. Comparison of the Extractabilitg' of Plutoniurmn into Benzene Phases Containing Various Fluorinated Diketones. 93 Pu(IV) _ , dlstr;butlon ratio Relative concentration Code SngtltutEd group fl_%n_z}%r%_ needed to give same name Rl(a) = 3 extraction of Pu(IV) TFA CHgq 1.0 1 PTA CHSCH2 9.0 1/3 ITA (CH3)2CHCH2 ~ 100 1/5 ~ 1/17 BTA CgHg ~ 100 / TTA HC - CH 42 1/15 HC\ /C— S FBTA pFCE;H4 ~100 1/ NTA ~ 100 1/7 FTA CH - CH . ~100 1 HC\ C- O/ (a)The general formula for these compounds is Rl—C(O)CHZC(O)CF3. 70 Pu(VI) and Pu(IV) complexes with pyridine-N-oxide-2-carboxylic acid which precipitate at pH 2-3 have been prepared.176 These compounds are iso-structural with TTA complex. A possible application ig the separation of U(VI) and Pu(VI) from solutions of salts. Mixed Extractants Synergism The term synergism is used to denote enhanced (or depressed) ex- traction of metals by mixed extractants, as against the extraction by each extractant taken separately. This subject has received considerable attention in recent years. Pu has received its share {(perhaps more than its share) of the general research, and while not many radiochemical applications have appeared for this phenocmenon, it is to be expected that more will be found. Considered in this section are all cases of changed extraction properties due to changes in the nature of the supposedly inert diluent, as well"’ as mixtures of different t{ypes of extractants such as TBP-TTA, TBP-DBP, etc. The range of phenomena described under the term synergism is thus diverse, complex, and in general not completely understood. The review of Marcus267 is excellent in this re- gard, and the reader is referred to it for a more complete discussion. Influence of Diluent Taubeage' 397,398 polarity and polarizability of supposedly inert diluents on the extractability of tetra- conducted extensive studies on the effect of the and hexavalent actinides with verious extractants, including hexone, TBP, DBC, TTA, TLA, and TBAN. Examples of diluents used are polar (P): chloroform, non-polar (L.): carbon tetrachloride, non-polar but polarizable (H): benzene., He found that the nature of the diluent exerted a large influence on the extractability, and proposed a theory based on (1) the interaction between the dipole of the organic molecule and the diluent dipoles, and (2) mutual interaction between permanent dipoles in the diluent mixture giving rise to structure in the organic phase. The effects can be large; e. g., DPu(IV) increases a factor of three in going from pure CHCl3 to pure benzene in TBP extractions. In general, the extraction of a non-polar complex (Pu(IV) and Pu(VI) with hexone, TBP, TTA, etc.) is favored by a non-polar diluent, In the case of the highly polar Pu(IV)-TBAN complex, the extraction is favored by a polar diluent; however, the presence of a polarizable diluent increases the extraction. The extraction as a function of the mole fraction of H-type diluent thus exhibits & maximum. This is explained by disruption of the agsociation of the dipoles in the P-type diluent, followed by participa- tion of the induced dipoles in the H-type diluent in the extraction. Shevchenko E’fl.afig' 371 found that the extractability of U(VI), Pu(IV), Zr(IV); and Ce(IIT) decrease with increasing polarizability of the diluent by TBP solutions from 3 M HNO,. Far greater effects are observed when two different classes of extractants are mixed. The enhancement (or depression) of the distribution coefficients may be 10% or 71 more. Siekierski and Taube,381 and Taube400 have proposed a systern for synergistic mixtures based on classification of extractors as anionic (A™), neutral (BO), or cationic (C). Anionic extractants are acidic compounds such as TTA, DBP, HDEHP, etc. that act as organic anions in the extracted complex; similarly neutral extractants (TBP, TOPO, etc.) are neutral compounds that form complexes through a basgic oxygen atom, and cationic extractants are strongly basic-compounds (TOA, TBAN, etc.) that act as cations in the extracted complex. In general the synergistic effect is small in mixtures of compounds of the same class, and may be small or large in mixtures of different clasges. These authors define a synergistic coefficient as D g = log' 1,2, exp (1) D; 2. aad Dl, 2, exp is the experimental distribution coefficient of a mixture of extractants 1 and 2, and Dl, 2. add is the calculated distribution coefficient based on additivity of the individual distribution coefficients. Additivity is based on the assumption that (1) no interaction be- tween the extractants occurs, and (2) no mixed complex of the extracted metal ion with the two extractants occurs. Both assumptions are commonly not true when extractants of different types are mixed. A summary table of examples of synergistic mixtures for U and Pu extraction is given in Table IV-26, based on this clagsification system. Taube400 has made an extensive survey of mixed extraction systems. Synergism in the system M-TTA-P, where M is an actinide and P is a neutral phosphate compound has been studied by Irving and Edg‘lng‘ton,lgfi_zoo in nitric acid and Healy169 in HCl. Healy found no evidence of participation of chloride in the ex- traction. The extraction reaction is thus X = + M™ + x HT(o) +y P(o) =M (T)x (P)y(o) +x H . (2) Values of y ranged from 1 to 3 for various di-~, tri-, and hexavelent ions. Th(IV) had a y value of 1 as did U02++, except in the case of TOPO where a value of 3 was also obtained at high P concentrations. Irving and Edgington found that 1 or 2 nitrates could enter into the complex, depending on the nitric acid concentration. With tributyl phosphine oxide (TBPO) the species identified were M(IV) T3(N03)P1, M(IV) TZ(NO3)2 P,, and M(III) T, (NO3)P2, whereas with P = TBP they were M(III) T3P2, M(IV) TB(N03)P1, and M(VI) T2P1, where M is an actinide. Thus the complex is influenced by the basic strength of P. These authors postulate that the reaction mechanism for hexavalent species ig the re- placement of a water molecule in the complex by P, giving a coordinately unsaturated product, thus MOZTZ H20 + P = MOZTZP(O) + HZO‘ (3) In the case of tetravalent species, one or more chelates are displaced by P molecules, with nitrates added to preserve electrical neutrality, thus MT4 + rnHNO3 + mP = MT4_m(NO3)um + mHT. (4) 72 TABLE IV-26. U and Pu Extractions.3 Synelé-gistic and Antagonistic Effects in Two Extractant Systems in Synergism or antagonism Exampleg for plutonium and References System OCCUrs uranium extraction and remarks A7+ A S>0 ? anionic + 59 anionic S << 0 U(VI), HG9PO + HaGPO Blake, 1959 At Be S>> 0 U(VI), H,S04, D2EHPO + TBPO Blake, 195929 anionic + UVI), HNO,y, TTA + TBP Irving, 1960196 non-ionic Pu(VI), HN(gg, HDEHP + TBPO Blake, 195999 Pu(VI), HpSO4, DNNSA + TBP Oak Ridge, 1960443 Pu(VI), HNO3, TTA + TBP Irving, 1961198 Taube, 1961400 S<< 0 U(VI), HoSO4 DDPA + TBP Blake, 195999 Pu(VI), Pu(IV), HpSO4, DBP + TBP Taube, 1961400 A +cCt S>>0 U(VI), HpSO4, DBP + TOA Deptula, Minc anionic + 1961115 cationic U(VI), HDEHP + tertiary amines Blake, 195928 Pu(VI) H3SO4, DBP + TOA Taube, 1961400 S<0 Pu(IV), H,SO,, DBP + TBAN Taube, 1961400 B + B, 5> 0 U(VI), TBP, TiBP _ 376 non-ionic + 5<0 ? Siddal 1960 .. no data non-ionic B° +C+ Pu(VI), Pu(IV), HNOs, TBP + TOA Taube, 1961400 non-ionic + S~ 0 Pu(VI), Pu(IV), HNO3, TBP + TBAN Taube, 1961400 cationic cf+c; cationic + S~ 0 Pu(IV), HNO,, TOA + TBAN Taube, 1961400 cationic ' SYMBOLS G* general alkyl group D2EHPO di-2-ethylhexyl phosphine oxide TBPO tri-n-butyl phosphine oxide DNNSA dinonylnaphthalenesulfonic acid TBAN tetrabutyl ammonium nitrate TiBP triisobutyl phosphate The trivalent species are considered to become 8-coordinated by either addition of two P molecules or replacement of two water molecules. The addition reaction is MT:3 + 2P = MT3P2. The synergistic effects discussed so far are for relatively small concentrations of P. synergism or antagonism sets in. Ii the P concentration is increased to about 1 M and above, a strong negative- The P dependencies for several M/TTA/P/HCl systems as quoted by Healy169 are shown in Table IV-2T7, Thus it is possible by judicious addition of one of these compounds to effect the selective return of ions to the aqueous phase. 73 TABLE IV-27. Slope of the Dependehce of the Distribution Coefficient on the Concentration of the Added Reagent for Mixtures of Phosphorous Esters, Amides, Alcohols and Ketones with TTA.41 Ion Valence Synergism region Antisynergism region Th v +1 -2 Am, Pm o1 +2 -4 UO2 VI +1 -2 Fused Salt Systems Some research has been done on the solvent extraction properties of actinide and other elements in relatively low-temperature eutectic mixtures of fused salts because of their potential use in homogeneous power reactors. Gruen ia_l.154 give a general discussion of oxidation states and spectra of actinides in LiNOs—ICNO3 mixtures, and indicate that TBP extracts a number of elements efficiently from the eutectic mixture. Isaac %-201 determined the distribution coefficients between Co(II), M(III) (where M is a trivalent actinide or lanthanide), Np(V) and Np(VI), and U(VI) in this eutectic mixture (MP 120°C) and dilute golutions of TBP in a mixture of polyphenyls at 150°C. In general, the distribution coefficients were a factor of 102 or 103 higher than the corresponding concentrated aqueous nitrate solutions. The dis- tribution coefficients all showed the same TBP concentration dependency a8 in acqueous solutions, indicating that the extraction mechanism is the same, the higher distribution being due to the increased salting-in effect. The effect of added chloride was to lower the distribution coefficients. Quadrivalent actinides would be expected to behave gimilarly, although none was determined. Borkowska iai.m used a KC1-CuCl eutectic mixture at 180° to study the ex- traction of Pu, U, and Am by solutions of TBP, TOA, and HDBP in diphenyl. For TOA they find the extractability is in the order << D Dpyam < Pamm < Puwn Uavy In this system a maximum in the D vs concentration of TOA curve occurs at ~40% TOA, where DU(IV) ~3. TBP shows similar behavior. The maximum in this case is at §7% TBP,2 where DU(IV) ~50. For U(].'V)’ HDBP is similaer to TBP. Moore measured the distribution of a number of ions between the immiscible galt pair LiCl—A1C14_K+ at 650°C. [t is perhaps not proper to speak of this system as extraction; however significant distributions (Kd > 1 on a mole fraction basis) in favor of the LiCl phase were noted for UCl4 (for which SnCl2 was added as a reductant), PuC14, and FeC13. The ratio of the distribution coefficients for tri- and tetravalent actinides was > 40. Since the SnCl2 used fo stabilize the U(IV) also reduced Pu to the trivalent state, an easy separation is possible in this system. Similar results were cbtained by Moore and Lyon290 for the system KCl-AlClB-Al. In this case the separation factor for U from Pu and Th is approximately 100, while that for Th from Pa is up to 800, Cafasso gt_a_l.73 determined the partition coefficient of a number of elements, including U and Pu, between liquid lead and zinc at 703°C. The results (Zn/Pb) are Pd:600, U:21.5, Pu:7.3, Ce:3.4, Sr:0.05, 74 D.3 Ion Exchange The phenomenon of ion exchange is of great utility in the radiochemaical separa- tion of Pu. Cationic Pu in dilute, non-complexing, acid solution will readily adsorb on cation resin in the hydrogen or alkali metal form. On the other hand Pu(IV) and Pu(V]) form anionic complexes in moderately concentrated nitric or hydrochloric acids and s0 will adsorb on anion exchange resins. Anion and cation exchange methods are thus both usable to separate Pu. The anion exchange separation is especially valuable in the laboratory because of the simple equipment required, the ease of manipulation, and the excellent decontamination from fission products by the use of redox cycles. Recently synthetic inorganic cation exchangers such as zirconium phosphate have been developed, A good introduction to the subject of ion exchange in the actinides is contained in Chapter 7 of Seaborg and Katz.l The review of Hyde 17 is valuable for ion exchange separations of the actinides. The general gsubject of ion exchange has been reviewed many times. The books of Helfferich175 and Samuelson348 are good references to the theory and applications of ion exchangers. Samuelson has a good review of recent work done on actinides. Helfferich gives a table of the names and properties of commercially available J".on-exchange materials. Kraus and Nel.":zon241 reviewed the general subject of ion-exchange separations in 1957, while [—Iard.y162 reviewed the ion exchange data for actinides in 1858, Cation Exchagge The general cation exchange reaction for an exchanger in the hydrogen form (acid solution) is M'P + bHR = MR, + bH" . 1) In this equation R is an exchanger site. The exchange reaction is favored by a low acid concentration or conversely, high acid can be used to displace the metal from the exchanger by mass action. Anocther way to remove metal ions from the exchanger is to decrease the concentration of M+b by complexing. In general, the absorbability of cations on ion exchangers increases with increasing charge and decreasing hydrated radius. Thus, the order of absorbability on cation exchangers for Pu is Pu(IV) > Pu(Ill) > PU(VI). For example, Schubert 358 found the following adsorption affinity for the strong base cation resin Amberlite IR-1: Th(IV)> Pu(IV)> La(Ill) Rare Earths > Y(III) Rare Earths > Ba(II)> Cs(I)> Sr(II) > U02++. All Pu species are absorbed well at low acld concentration, and are desorbed at high acid concentrations, However, many anions form neutral or anionic complexes with Pu in all of its oxida- tion states, and therefore Pu may be desorbed by reaction with the anion of the acid, as well as the massg action displacement. The sulfonated cross-linked polystyrene resins have been by far the most popular materials for the separation of inorganic species, including the actinides. Typical of these is Dowex-50. This resin is usually specified ag "X 4" or "X 12,” ete., which means 4% or 12%, etc. divinylbenzene was added to the styrene in the 75 - polymerization of the resin to provide the crogs linkage. In general, the low-cross- linked resins have the advantage of faster kinetics, but also have the disadvantage of greater volume change with changing ionic milieu, As mentioned above, under non-complexing conditions, i.e., dilute acidic solution, the absorption of Pu is esgentially independent of the anions present. How- ever, many anions form Pu complexes at moderate concentrations, which makes the elution behavior of Pu variable. The elution behavior of Pu on cation resin is summarized in Fig. 39, where the distribution coefficient for Pu(Il), Pu(lV), and Pu({VI) on Dowex-50 is plotted ag a function of the acid molarity, 104 104 0% T Pul¥ Pud¥dL ! / 103 103 _ 1031 — / : / \ / 2l 2 D 100 ' HCl 0T /hciog \ | 0 [¢ H 10 |-\ .\__ \. NOs 2 Hnos \ \ cl v L s ) 1 O 2 4 6 B0 O 2 4 6 B0 0 2 4 6 8 10 MOLARITY OF ACID Fig, 39. Typical distribution coefficients of Pu on Dowex 50 in common acidic solu- tions. These data are intended to be only illustrative of the behavior of Pu. In some caseg, the data of other actinides (e. g.-Am(II), U(VI)) were adjusted to corre- pond to Pu in the same valance state. The data in every case were taken from litera- ture mentioned later in this section. ' In general, the slopes of the curves are steeper for HNO3, H2504, and HCI1O, than for HCl. A strong increase in the distribution coefficient in HC1O, at high acidities is shown for Pu(Ill) and Pu(VI). This increase occurs in a great number of elements,soo and probably also for Pu(IV). The classic work on cation exchange of the actinide elements in HC1 solu- tion was done by Diamond et al. 117 whose principal results are shown in Fig, 40 as a plot of relative volumes required to elute tracer amounts of the ions from a Dowex- 50 column 10 cm long by 1 or 1.5 mm in diameter. These data are proportional to the distribution coefficients, and illustrate the separations obtainable in this system. The points for the. Pu species have been connected to make a crude elution pogiton vs HCl concentration plot. The exireme decrease of the Pu(IV) elution position in going from 3.2 to 9.3 M HCI is undoubtedly due to the formation of 'an anionic chloride complex. The tetravalent actinides elute in this sequence: Pu, Np, U, Th; i.e., Th has the highest distribution coefficient at any HCIl concentration. This order of elution is in accord with the decreasing hydrated radii in going from Pu to Th. Th(IV) was not 76 3.2M HCI Th(IV) —e= ! Ll oyl N g Np(¥) Pu{iD| UTZ Cs YbSrY CmTPuCoLnRu Ac Pu(lY) —== / Np (D / Am _ - / /’ - / / - / 6.2 M/ HCI -~ [ w/ L ||/|||u/'|/| - T T T 1 T T T T ¥ Th Np D futam csvp Y cs mI)os/Lua:1Ru| fe w Pu(¥D Am .~ PullVINp(IX) I ! 7 r > 93M HCI L1 L | t Th(¥) —e= PulD ’U’(%c. Puluabflp élfll |Eu Src. Lu Ac Pu[ID Am uay | I | ' / L byl Th (D) —=— Np(¥) Cs Pu(I'V)CI!)AmCEEYI: RoY EuBa C|LuSr Ac Um(&n Pu Pu | L |I|||||l| ] L1l ] Lol | 100 1000 VOLUME OF ELUTRIANT Fig. 40. Relative elution peak position of actinides and other ions in varigus HC1 concentrations. The positions of the Pu ions have been connected by lines, 117 eluted at all under the conditions of the experiment. A plot of the elution position of the tetravalent actinides under slightly different conditions is shown in Fig. 41 to show the relative elution position of Th(IV). The well-known separation of the trivalent actinides and lanthanides is illustrated by the increase in the elution positions of the lanthanides at high acidities, Nelson _eifl.So summarized the cation exchange behavior of most of the elements in HC1l, The summary is in Fig. 42 as a periodic table of DV ve HCll concentration. Dowex-50 X 4 resin was used. Although relatively few data for Pu are included, the curves for Th(IV), U(VI), and Am(OI) permit a normalization to the data of Diamond et al. 117 Strelow 395 jnve stigated the cation exchange behavior of 43 elements on Dowex-50 X B resin at HCl concentrations up to 4 M with results in general agreement with those above. He arranged the elements in decreasing order of the equilibrium distribution coefficients in 1 M HCl. The values ranged from 7250 for Zr{Iv) to 0.3 for Hg-H-. The distribution coefficient of Th(IV), the only actinide studied, wag 2049, just below Zr. 1 1000 Oc— * [ Th B [ .o - o c - = = 100 s t Fig. 41, Elution peak position of the = - tetrapositive ions vs hydrochloric acid = [ Y molarity, 117 g | > ¥ 5 10 Pu a = =2 - o | '— > - | w I I j — 1 6 9 HCI MOLARITY [ ELEMENT | AND Fox10ATION ] STATE oAl o 4 8 2 MOLARITY =0 LOG DISTR. GREPF., 0, o n LI Fig. 42. Volume distribution coefficient of the elements vs HCI concentration for Dowex 50 X 4 cation exchange resin, Tracer concentrations of the elements were used for the most part. : 78 Prevot et al.st. determined coefficients of Pu(Il) and Pu(lV), along with other ions as a function of HNO'3 concentration (Fig. 43)., They used C- 50 resin (similar to Dowex-50). Pu(IT) and Pu(IV) are expected to absorb very strongly below 1 M acid. The distribution coefficient is very low at I—lNO3 concentrations < 4 M, since the U(VI) and Fe(Ill) curves are flattening out. A partial separation frbm these ions can be achieved in the elution of the Pu. - Nelson e_‘t_il.300 used I-IClO4 as the aqueous medium in also their survey of cation exchange behavior. The results shown in Fig. 44 show some striking differences from the HCI data. In high HC1O, concentrations > 2 M) most elements have increasing distribu- tion coefficients after having gone through minima, These authors state that essentially all the actinides in what- ever oxidation state have appreciable l. 17150 | | L\ ) \\ Pull¥) D 100 \\W \ % \ \ \\ cu NN \ 10 Aw — A ™~ .\\ \ "‘—--U(ID Fe (D™ Pu (I ~_ IO | 2 3 4N NITRIC ACID“S()DNCENTRATION Fig, 43. Distribution of Pu(lII) and Pu(IV) and other ions between nitric acid solutions and the catloréggsm C-50 (similar to Dowex-50). distribution coefficients at high HClO concentration, and that this phenomenon might be made the basis of an actinide group separation, Neill and Higgins 299 getermined distribution coefficients for Pu(Ill) and Pu(IV) for several regins in sulfuric acid solutions. Their results are shown in Table IV-28. They used Dowex-50 resin to demonstrate a process for recovering Pu from sulfuric acid decladding solutions which contain stainless steel, The Pu is normally trivalent in dilute sulfuric acid solutions, and is adsorbed from 0.5 M acid, scrubbed with 0.5 M sulfuric acid, wasghed with water to remove sulfate, and eluted with 6 N HNO primarily iron and chromium. 3 The product Pu solution contained 5% of the original stainless steel materials, The most common applications of cation exchange techniques for Pu are (1) concentration from a dilute solution, or (2) separation from nonabsorbable impurities, such as hydrazine. 419 concentration of Pu from solvent exiraction plants have been developed. processes should be easily adapted to the laboratory gcale. Several processes for final purification and Thesge Bruce 60 describes the process-as adsorption of Pu(lll) from 0.25 M I—INO3 by Dowex-50 X 12 from a 0.15 g/1 golution of Pu(IlI) which is 0.1 M in hydroxylamine sulfate, washing with 0.1 - 0,25 M HNO3 containing 0.05 M hydroxylamine sulfate, and eluting with 5.7 M HNO3 containing 0.3 M sulfamic acid to prevent oxidation to Pu(IV). Bruce reports a concentration 480 o= Fig. 44, Volurne distribution coefficient of the elements vs HClO4 concentration for Dowex-50 X 4 cation exchange resin. TABLE IV-28. Distribution Coefficients for Pu for Various Cation Resins in H,SO, Solutions 299 Resin Concentration (M) Pu(II) Pu(IV) Duolite C-65 0.5 5.3 35 Dowex 50 X 8 0.5 360 -- 3.6 3.6 -- Dowex 50 X 12 0,25 144 -- 0.5 1470 - factor of 330 for Pu in this process. Decontamination factors of approximately 20 to 30 for Zr and Nb, and 2.4 tc 8 for most other ions were obtained. During the entire process the Pu is kept trivalent for several reasons; among these are (1) the Pu isg initially trivalent as it is stripped from TBP in the Purex process, (2) oxidation during adsorption liberates gasses which may channel the resin and (3) Pu(OI) is more eagily desorbed, permitting a higher concentration factor. Durham and Aiken 119 describe essentially the same process. Prevot 325 255 and Sikl{eland382 elute with 6~8 M HCI in preparation for et al. Lingjaerde 80 anion exchange in an HCl system. The latter workers use an additional 2 M HCI wash to elute the U(VI) and sorme fission products before elution of the Pu, Pm and Ce were the major contaminating fission product activities in this procedure (see procedure insert VIII). Den Boer and Dizdar 114 used the same general scheme except 1.5 N [—INO3 wasg used to elute the U02++ and hydrazine was the reductant, and the Pu(Ill) was eluted with 8 M [—INO3. Chetham-Strode 5 investigated the behavior of NH, (), Fe(lI), P{IV), and Al(ITI), which are common contaminants in the laboratory purification of trivalent actinides for spectrometer sources. His results are shown in Fig. 45 with Am(ITI) as a typical actinide. His procedure was to adsorb the ions from a very dilute HCI1 solution, wash with 1 M HCI, and elute with 6 M HCI. 0OO05M HCI © = 6M HCI I 0 + ol +4 , 43 prtd af t+3 = I by af-mme e - = m @ CONCENTRATION Fig. 45. Separation of Am from some common impuritieg by elution with HC1. The abcissa is drop number for a 0.3-cm diam- eter by 10-cm column. The 86 resin used was Dowex 50 X 4, e - e e — e A e —— e —————— 10 16 DROP No. Zolotov and Nishanov 436 report the separation of Np from U, Pu and fission products by elution of Np(V) ahead of U(VI) by 1 M I-INO3 from the cation ex- change resin KU-2. In the presence of 1 M HNOS, Np(VI) is reduced to Np{(V) on the resin. The Pu(IV) is then eluted with 3 M HN03. Zagral and Sel' chenkov 435 separated Np and Pu by elution from cation resin (KU-1 and KU-2) with 0.02 M hydrofiuoric acid after reduction to Pu{Ill) and Np(IV) with SO, for 20 minutes at 90-100°C. The preparation of cation exchange resin beads with scintillating properties was reported by Heimbuch and Gee. 172 Polyvinyl toluene-divinylbenzene rnixtures were polymerized with p-terphenyl and 1, 4-bis- 2-(5-phenyloxyazolyl) -benzene as scintillators. The resin beads were then surface-gulfonated, to give capacities rang- ing from 0.01 to 0.1 milliquivalents/gram, Srgo, Pu239, find P0210 have been adsorbed with this resin and counted with efficiencies from 30 to 50% of the adsorbed activity. Several applications are suggested: 1. Easy sample preparation for adsorbable radionuclides. 2. A combination of concentration of ions from dilute solution and sample preparation. 3. Rapid qualitative analysis for radionuclides in dilute solutions. Kennedy et al. 222 prepared and tested phosphorylated resins, which are analogous to acidic phosphorous compounds in solvent extraction systems. They found that these resinsg are between carboxylic and sulfonic resins in acidity. The adsorption 81 affinity of geveral ions was Th(IV), U(IV)> U(VI), Fe(ll)> La(OI)> H > Cu(1), Co(Il), Ca(m})> Na+. Pu was not measured, but Pu(IV) would presurnably be with Th and U. Inorganic Ion Exchangers Although inorganic ion exchangers have been long known, they have been largely superseded by the synthetic resins, principally because of the higher capacities and more tractable physical characteristics obtainable in the synthetic exchangers. However experimentation has continued on natural and synthetic com- pounds. In the actinide field this work has proceeded primarily toward the finding of better geparations from fission products, The inorganic exchangers are also quite resistant to radiation damage, which is an advantage in process applications. A general discussion of the ion exchange properties of hydrous oxides has been given by Kraus et al. 242 Inorganic phosphates as ion exchange materials have been reported. 31, 1.3 The use of zirconium phosphate to separate Pu, U, and fission products has been reported by Gal and Ruvarac. 140 Equilibrium distribution coefficients for a number of ions are shown in Fig. 46, plotted against nitric acid concentration. The solution containing U, Pu and fission products was loaded onto a column at 0.5 M I-INC_)3 +0.02 M NaNO2. The U, Ce, Sr, and Ru pass through the column. After washing the column, the Pu and Cs are removed with 8 M HNOa. The Zr and most.of the Nb stay on the column. Of the ions studied, only Cs follows the Pu and must be separated by an additional step. Ahrland et al. 21,22 and proposed a separation of Pu, U and fission products similar to the one described studied the behavior of several ions on silica gel for zirconium phosphate above. The distribution coefficients are plotted as a function of pH in Fig. 47, revealing an easy separation of Zr, U, Pu, and other ions by pH and valency adjustment, Rydberg 341 separated Zr-Nb from Pu by adsorption of the former on silica gel from a 6 M HNOj3 solution (see Procedure 11 in Sect. VIII). 112 Cvjetcanin extracted Pu(VI) and U(VI} with hexone in the presence of gilica gel to effect a Zr-Nb separation. Cvjetcanin and Cvjetcanin 113 uged a column of MnO2 to separate U and Pu from long-lived fission products. The method is adsorb the fission products from 0.1 N H_NO3, while pasging U(VI) and Pu(VI) through the column. QOver 99% of the Zr, Ru, and Cs activity was adsorbed on the column. The capacity for zirconium for MnO2 dried at 110°C was determined to be 1 milliequivalent/gram. An exchanger eomposed of Zr and Si oxyhydrates has been prepared and applied to Pu separations. 291 Pu has been concentrated from environmental water samples by chemi- 352 (see Procedure sorption of Pu(IV) on calcium fluoride from a nitric acid solution 13 in Sect. VIO). ' Kennedy et al. 223 describe the absorption of Pu(IV), U(VI), Ru, Zr, and Nb from aqueous carbonate solutions by hydrated titanium oxide (HTO). About 82 Zr(IV)+ NB (¥) HNO 3 CONCENTRATION (M) Fig. 46. The dependence of the distribution coefficients of several ions on zirconium phosphate on the aqueous HNOg concentration. All adsorbates present in tracer amounts. Solutions of Pu({Ill} were 0.005 M in sulpharmc acid and 0.015 M in l}g'drazine; solutions of Pu(IV) 0.02 M in NaNO and solutions of Pqu 0.02 M in KBI‘Og T - 2riv 7] +Nb u(vn ® ulivy/ feutivy — Co Na of _ 1 ] 1; o LOoG D pH Fig. 47 Log D for some metal ions as a function of pH on silica gel (KEBO, 50-100 mesh).2 83 95% of Pu(IV) was removed from a 0.5 M Na,COjg solution by passage of 2000-bed volumes at a flow rate of 1. ml/cm /mm of the seclution through an HTO column. The abgorption of Pu(lV) was not affected by the presence of 5 mg/1 of U(VI). The absorp- tion of Pu(VI) was only 20% in 1000-bed volumes under the same conditions. A possible application of this system to recover Pu and other ions from carbonate wastes in processing plants is discussed. Paper Chromatography Clanet 0 determined paper chromatographic Rf values for Pu(IIl), - Pu(IV) and Pu(VI), U(IV), and U(VI), and Am(III) in HCl-butanol mixtures (1:1) ranging from 1to 10 M HCl. The Rf values reached a maximum around 6 M HCI and ranged from 0.27 for U(IV) to 0.50 for U(VI), the other ions falling in between. The ions of lower valency tended to have lower Rf values, Bildestein ‘_at;al.fl geparated U and Pu by several paper chromatographic methods, using different combinations of solvent and acid. The use of ion-exchange paper to separate U and Pu was also reported by these workers. For example, with Whatman ET-20 using 6 M HC1 as a developer, the R, values are 0.56 and 0.98 for U and Pu, respectively. The oxidation states of the U and Pu were not specified. ‘F'ink and Fink 131 investigated many combinations of solvent and acid to develop paper chromatograms of both Pu(IV) and Pu(VI). In most systems Pu(lV) failed to move or streaked, but in a few cases moved quantitatively. The resgults indicated Pu(VI) and U(VI} might be separated in a methyl ethyl ketone — dilute nitric acid system. Anion Exchange The behavior of the actinide elements in various oxidation states on a strong base anion exchange resin (typically Dowex 1 or 2) in HCl is shown in Table IV- 29. Strong adsorption of the actinides in the higher oxidation states (IV-VI) occurs at HC1 concentrations above 6 M while desorption occurs below 2 M HCI, TABLE IV-29, Absorption and Desorption of Actinides on Strong Base Anion Exchangers in HCI Solutions Oxidatiop _State of %%Concentratlon M) for —57 Actinide Absorption Desorption 1 Not abgorbed | - Iv 6-8 2-4 v 6-8 2-4 Vi 2-3 0.1-1 @)k 4 = 10-100 for absorption. (b)Kd = 0.1-1.0 for desorption. A convenient way of separating Pu from other actinides and most other elements is to adsorb Pu{IV) or Pu(VI) onto such a resin from> 6 M HCI solution, wash with HCl, and desorb by reducing the Pu to the trivalent with a suitable reducing 84 agent. This method is so simple and effective that it has become one of the standard laboratory methods for the separation of Pu, as well as in larger scale process plants. Pu(IV) may be also adsorbed from 7 M HNO3 solutions and desorbed either by dilute acid or by reduction. The distribution coefficients and separation factors from fission products are higher than in the HCI system, but the room temperature reactions are slower, resulting in some loss of convenience, 325 Many of the procedures collected in this volume are based on anion ex- change, Wigh and Rowell 432,433, 434 coefficients for several actinide and other elements for Dowex-2 in HC], HNOB, H2804, and HC1-HF solution with results shown in Figs. 48-51. Although no Pu data in I-INO3 was obtained by these workers, the curves are included for comparison. have determined equilibrium distribution Dowex-2 is made by addition of dimethylethanol amine to chloromethylated polystyrene, while Dowex-1 is made with trimethylamine, 175 The equilibrium distribution data for 434,240 55 that the behavior of the actinides in Dowex-2 is also valid for Dowex-1. The behavior of the ions in the HC1- the 2 resins is quite similar, e.g. for U(VI) HF mixture shows the effect of strong HF complexing in Zr and Pu. These workers geparate Pu from Zr and other elements by eluting the Zr with 11 N HCI - 0.06 M HF, and the Pu and Np together with 6.5 N HC1 - 0,000¢ N HF. Marcus 266 measured distribution coefficients for macro amounts of T, Np. and Pu in the tetra- and hexavalent states on Dowex-1. The oxidation states of the ions in these experiments were measured spectrophotometrically both in the solu- tion and in the resin pPhase. The results, which differ somewhat from those above are shown in Fig. 52 as volume distribution coefficients, Dv’ obtained by multiplying the usual D by the resin bed density, 0.45, in thig case. Hardy 162 hag summarized equilibrium data for the actinides in HNO3 and HC1 solutions for various strong base quaternary anion resins. These are shown in Fig. 53. The Pu(IV) data in HNO4 show significant differences for different resins and different workers. The species adsorbed from 7 M HNO3 has been shown to be = 337,120 — Pu(NO3)Ei . Data for the adsorption of other elements on Dowex 1 from HCI1 solutions 240 and [—INO3 solutions 127 are shown in Figs. 54 and 55. The great specificity for actinides in the higher valence states is shown by Fig. 55. Many examples exist of the use of anion exchange resins for Pu separations, both in HC1 and HNO, solutions. Adsorption in 8 to 12 M HCI and elution by reduction to Pu(IlD) with NH,I in 8 M HC1, 108 382, 447,185,383 o5, by 45 concentrated HC, 185 293 or with NHZOH and NH4I in concentrated H%19:31155are common procedures. An : is to adsorb Pu(lV) from 7 M HNOS, wash the column first with 7 M [-I.NOa, then with concentrated HC1, and finally strip in 10 M HC1 - 0.5 M HI or NH,I solution. This method combines the advantages of the somewhat greater selectivity and removal of iron of the nitrate system with the alternative procedure which has been used ease of reduction to Pu(Ill) of the chloride system with resulting small strip volume. The elution of Pu(IV) by HC1-HF mixtures has been mentioned before, 432, 433 These 85 104 K = o D STRIBUTION COEFFICIENT) = L Ep (DI (™ . o 167 0 2 L 6 8 10 12 1y Irig. 48. Equilibrium distribution coefficients for Dowex g in HCI solutions. 432, 433 (Mo, Zr, and Nb curves furnished by L. R. Bunney et al.b 36 2100 o 8 10 12 14 N HNO, Fig. 49, Absorption of various iong by Dowex 2 from nitric acid éolutions.433 . 87 1049 103 102 Kp 100 Qi N H,SO, Fig. 50. Absorption of various actinide ions from H2804 solutions by Dowex 2.433 88 0 2 L 6 8 10 12 1k N HC1 CONTAINING O.3N HF Fig. 51. Equilibrium distribution coefficients of various ions on Dowex 2 in HCI ~ HF solutions. , 85 1000 - 1T 1 Np (3M, Pu (¥I) 500 | U (¥D) 200 100 50 | R A N 0 | 2 3 4q 5 6 HCI CONCENTRATION (M) Fig. 52. Volume distribution coefficients, Dv, for tetra and hexavalent U, Np, and Pu between Dowex 1 and hydrochloric acid solutions. 90 ANION EXCHANGE ANION EXCHANGE ANION EXCHANGE IO‘ T T =T T DEACIDITE FF f‘HflB,‘%ROL'TE (9] DeACIDITE FF e) (fl) J/—s -(\ 103 im foro T D o2 // I/ Dowex ! ' Pol¥ | — M T oL LA g | o AnSeLTe e 7/ o N /23000 / ‘ alL polTH | [ 1 Q 2 4 6 810 0O 2 4 6 B O 0 2 4 6 6 10 M,HNO : M,HNO3 M,HNO3 o4 T T . I T - I | 10 T T DOWEX | AMBERLITE IRA 400 FRENCH A 300D D yor b} no~gTRONGLY d) FoarroNeLY | (f) 103} apsonmep -ADIORBED AT 102 apsoreep } [ >6 W MGl >eH 0100 / 10 | # o] Pu 10 [ 7 //flm um Np Pum 1 ol | 0O 2 4 66 8 10 0 2 4 & 8 10 0 2 4 © B 10 MHCI M, HCI M,HCI Fig. 53. Equilibrium distribution coefficients for actinides on various strong base anion exchangers, 162 Individual references: 63 Th and U; Carswell 80 240 2) Pa; Hardy et al.1 b) c,d) e) Kraus and Nelson Ward and Welch (unpublished data) De-acidite FF; Phillips and Jenkins 23 319 Dowex 1; Aiken Amberlite 1 RA 400 and French A 300 D; Prevot et al. 325 Prevot et al. 325 f) 91 o I no ads. - NO ADSQRPTION 0.4 <« M HClL.<12 sl. ads, - SLIGHT ADSQORPTION IN 12 Af HCI (035D { 1l ads. Fig. 54. Adsorption of the elements from hydrochloric acid solution by Dowex 1.2%0 NGO \DE. - NO ADSORPTION FROM |-14M HNOy BL. ADS. ~ JLIGHT ADSORPTION o 4 1i2i4 MOLARITY HNOp . [ Fig. 35. Removal of elements from solution in 1 M nitric acid with strongly basic anion-exchange resin.127 u2 methods have been incorporated in sequential separation schemes for Pu and many 108,432, 433,434 other elements. Np and Pu have been separated by reduction of the Pu with NH4I before adsorption on the resin, 204 The removal of macro amounts of Pu before analysis of other elements is 280,405, 319, 55 commonly done by anion exchange either from HNO, or HCI1 solutions for example . ’ The separation of Pu irom U by adsorption of U(VI) on anion exchange regin in 60% ethanol which is 2 M in HCl has been reported. 298 Pu is reduced to Pu(Ill) with hydroxylamine and is not adsorbed in this form. The advantage of this system over a pure aqueous one is low shrinkage of the resin and rapid adsorption and de- sorption of the U(VI). In the nifrate system Pu is usually adsorbed from 6 to 8 M HNO3 because the distribution coefficient decreases above this concentration and because resin de- gradation becomes a problem at high acid concentrations. The applications are either to separate Pu, or to separate other materials from Pu. Roberts and Brauer 333 separate Am, Pu, and Np by adsorbing the Pu and Np from 8 M HNOS, eluting the Pu with 0,02 M ferrous sulfamate, and finally eluting Np by oxidation with Ce(IV) sulfate in 0.25 M HNOS. In another method, Th is included in the separation scheme by adsorption of Th(IV), Pu(IV) and Np from 8 M HNOS, elution of the Thby 12 M HCl, of Puby 12 M HCI - 0.1 M NH4I, and of Np by 4 M HCl. These authors report a clean separation with greater than 95% yields by both methods. Buchanan et al. 66 report separations of U, Mo, Ce, and Zr from Pu by anion exchange methods in analysis of Pu-"'fissium" binary alloys for these elements. Other eluting agents for Pu adsorbed on anion exchange resin in the nitrate 159, 419,319,189 ;14 0,36 M HCI - 0.01 M HF, 243 243 used a "slurry-column" technique for the system are hydroxylamine Kressin and Waterbury rapid separation of Pu from other ions. The 7 M I—INO3 solution of the ions ig slurried with about half of the resin to adsorb the bulk of the Pu before placing in a column containing the other half of the resin. The solution can then be run through the column at a more rapid rate without Pu breakthrough, because most of the Pu is already adsorbed. Thesge authors used a low cross-linked resin (Dowex 1 X 2) to speed the kinetics of the adsorption reaction. They report greater than 99,9% recovery of the Pu by this technique when mixed with substantial quantities of over 40 elements, The Pu is desorbed with an HC1-HF mixture, again to speed the elution. | Anion exchange from HNO, solutions is used ag a unit process in a number 3 of large scale processes of different types. Among these are: (1) the concentration and purification of Pu following a solvent extraction separation; 338, 339, 340, 325, 255 (2) the recovery of Pu metal scrap; 336, 331 23, 57 and (3) the main separation step from fission products. 207 The separation of Pu and Th in HCI1 solutions has also been described. Anion exchange methods have been used in several procedures for the 33, 404 205, 74, 254, 421 determination of Pu in biological material, especially urine. 93 Toribara et al. 403 used a liquid scintillation technique for counting Pu [rom bio- logical materials, The counting was done by a single-phase mixture of sample in aqueous solutions, absgolute alcohol, and liquid scintillator, Electrolytic Separation Methods Separation methods based on electrolysis have been used for radiochemical applications, but are not common because of the relative complexity of the method. In very early work, Cook 101 found that Pu could not be separated from Np and U by electrodeposition from acetate solutions at pH 6-~7. However, Samartseva 344 found that U, Pu, and Np could be separated by electrolysis from nitric acid 'solutions by varying the pH. His results are shown in Fig. 56 as a plot of % yield vs pH for the gtated conditions. Optimum conditions _f(_Jr the separation are stated as (1) current density 750-1000 ma/ cmz, (2) plating time 2 to 3 hours, and (3) solution volume 20 to 40 ml. Samartseva also found that electrolytic separation of Pu was successful against many competing ions in concentrations up to 0.5 mg/ml. Among the ions tested were Fe, Al, La, Ba, Cr, Mn, Ca, Mg, Bk, and Na, Of these only Fe interferred with the separation to an appreciable extent. Oxalic acid at 0.002 M concentration was added to complex the Fe. On the other hand, Sinitsyna et al.384 found that the deposition of U and Pu was strongly dependent on pH and current density, but that quantitative separations could not be achieved at any pll from nitric acid solutions and acetate buffers. Rein Qt_g_l_.azg separated Pu from Cr, Co, Ni, FFe, Pb, Mn, Sn, and Zn by deposition of these elements on a Hg cathode [rom 1 N HCI. Por’l:ersz1 found that Pu metal could be deposited on a mercury cathode from an organic solution, and determined that dimethyl sulfoxide solution saturated with the metal chloride was the best solvent among those investigated.322 Np 60 U,Np & Pu YIELD, % 1 L 7 9 Fig. 56. Relation of element yield to solution pH. The current density on the cathogif‘lwas 100 rnA/cm2 and the electrolysis time, 2 hr. The solution was nitric acid. 94 Clanet et al.gl separated U(VI), Pu(IV), Am(III), and Cm(III) by paper electro- phoresis using 10 M HN03 as the electrolyte. A plot of a radioactivity scan of their "electrophoretogram' is shown in Fig. 57, which gives the experimental conditions, U(VI) would lie between Pu{IV) and Am(III) in this plot, according to the measured mobilities in this system. cm (i) 100 Pu{IV) Amd{inn) a -~ Qo ACTIVITY (COUNTS/min) N 0 1 A 1 1™~ 3 11 2 4 6 8 IO m DISTANGE {cm) Fig. 57. Separation of Pu(IV)-Am(III)-Cm(I11).91 Electrolyte: 10 NHNOj. Support: "Millipore" HAWP paper. Development voltage: 250 volts. Time: 6 hours. 95 V. DISSOLUTION OF PLUTONIUM SAMPLES FOR ANALYSIS A. Metallic Plutonium Plutonium metal dissolves in HCl and other halogen acids, but not in H'NO3 or concentrated H,SO,. Dilute H,SO, attacks Pu slowly.! The addition of HF to HNO, 274 renders Pu svr::luble.428 Sulfamic acid has been used to dissolve Pu metal.zlo Pu-Al alloys can be dissolved in 6 M HNOS -0.056 M Hg‘(NO3)2 - 0.02 M HF, as well as HCI1 and HC104. An alternative method is to dissolve the Al in a solution of NaOH - NaNO,. The Pu and other actinide elements can then be dissolved in boiling 3 HNO3 or HCI1 after filtrE).‘cion.317‘166 317 B. Other Compounds Pqu, if ignited, dissolves only with great difficulty in the usual acids. Boiling with concentrated nitric acid plus 0.005 M HF,445’328 with B5-100% H3P04 at 200° or with 5-6 M HI451 have been recommended methods. Another method is fusion with ammonium bifluoride, followed by treatment with aqueous aluminum nitrate or 107,62 acid. Ignited Pu oxalates and fluorides have been dissolved by fusion with potassium bisulfate, dissolving the residuein water to precipitate Pu(OH)4, and finally 263 The sealed tube method of Wichers et alfl53 has been 454 dissolving the hydroxide. used to dissolve Pu-containing samples. C. Biological and Environmental Samples The Pu in thece samples ranges {rom readily soluble in the case of metabolized plutonium in excreted samples, to extremely refractory in the case of fallout samples. Nielsen and Beas‘.ley303 describe methods for dissolving various biological samples. Most procedures for dissolving fallout or other environmental samples involve treat- ment with HF or a basic fusion step which renders the Pu soluble in acids. VI. SOURCE PREPARATION AND COUNTING METHODS A. Source Preparation A universal problem in Pu radiochemistry is the preparation of sources suitable for counting. Owing to the short range of alpha particles in matter, the thickness of foreign material on the counting sample is limited to approximately one mg/crn2 for counting without serious loss. The requirements are much more severe if the ratios of alpha-emitting isotopes are to be determined by energy analysis. This is so because an alpha particle will be degraded in energy by interaction with the surrounding medium, and the resulting pulse height distribution will be smeared out. Most of the methods used for preparing alpha counting sources in use today were developed in the Manhattan Project. Jaffey and Hufford and Scott189 summarize the project experience. Source mounting techniques are, in general, a trade-off of quantitativity on the one hand with thinness on the other. In assay work it is very important to be quantitative but not so important to have a "thin'" sample. On ihe other 26 hand, for the separation of alpha particle energies by energy analysis the thinness of the source is paramount, while guantitativity is not required, at least in the case of isotopic dilution analytical methods. Table VI-30 is a surnmary of the project method for alpha source preparation. The reviews mentioned above are the primary source of this information and should be con- sulted for more detail and literature references. Other general reviews may be con- sulted for a discussion of the problem of mounting thin sou.r'ces.mz’a86’307 Two of the most widely used methods for preparation of alpha sources on a metal backing for counting or spectroscopyare (1) direct evaporationof an aqueous or organic solution and (2) electrodeposgition. Other methods, such as volatilization of the sample in a vacuum, adsorption from an agqueous solution, are not so widely used. However, the method of vacuum 'flashing' from a tungsten filament produces very satisfactory sources and is in routine use in some laboratories. (See for example Procedure 4 in Sect. VIII.) A.l Direct Evaporation This method has the advantage of speed and simplicity and the disadvantage of tending to concentrate any mass present in the solution to produce local thick areas. The classic ”LaF3” of LaF VII). In general, the method is satisfactory if only total alpha counting is to be done. method for the determination of Pu utilizes direct evaporation of a slurry 446 (Procedure 1 in Sect. 3—Pu, followed by alpha counting to determine the Pu However, in methods which depend on alpha energy analysis, direct evaporation of even a ""carrier free' solution will not be completely satisfactory. The reason for this failure lies in the above mentioned concentration effect to produce an effectively "thick' plate. The great advantage of other methods in this regard ig that the Pu and impurities in the solution to be plated are spread evenly over the entire area of the plate. Tucl-:qt06 describes a method for evaporating organic solutions of alpha-emitting ma- terials by heating only the edge of a circular plate, thus confining the liquid to the center. The same principle was used by \a‘Vestru.m426 to evaporate sulfuric acid solutions. A. 2 Electrodeposition This method has the advantage of producing thin uniform plates suitable for energy analysis of the alpha particles, and the disadvantage of requiring a relatively complex apparatus and relatively greater effort. The time to produce one sample can be as much as two hours. K0233 Cm. He chose a buffered solution of formic, perchloric or sulfuric acid and ammonium gives specific conditions for electrodeposition of the actinides from Th to formate and achieved high yields for up to 100 ug of Pu at current densities of 100-300 rnA/crnz. The deposition of all these elements occurs as a precipitation reaction ai the cathode. In the case of Pu, the compound precipitated is Pu(OH)4 (hydrated). Moore and SmithzBB also used an acid solution of ammonium oxalate to electrodeposit Pu. Mi’cchellfl""-:'2 gives a rapid method for electroplating trace quantities of actinides from HCl-ammonium chloride solutions. He gets essentially queanlitative deposition in 15 minutes from a ¢.1-0.2 g/ml chloride solution at pH about 1 using a current density of 1 A/cmz. 97 86 TABLE VI-30. Source Preparation Methods for Alpha Radioactivity Measurements(a) Method and Principle . Normal Evaporation - Placing 1, solution on a suitable backing, usually Pt, and evaporation under a heat lamp, and igniting, 9 Solution may be pipetted quanti- ’ tatively if desired. . Slurry Transfer of Carrier Salts - Co-precipitation with suitable salt, transfer to plate, spread, evaporate and ignite, . Electrodeposition - Electrolytic reduction of plutonium at a platinum cathode. . Low Temperature Sublimation in Vacuum - Prepare volatile compound, place in low temp- erature oven in vacuum, collect vapor on suitable cold plate, The volatile compound is rendered non-volatile and the organic material destroyed by ignition, . High Temperature Sublimation in Vacuum - Place material in oven with suitable orifice, evacuate and volatilize at high temperature. Collect on a cold plate. The oven may be a dimpled W or Ta strip heated by resisiance heating. In this case the plate need not be cooled, Applications Preparation of sources for alpha counting from agueous solution, Preparation of sources for alpha counting from organic solution, Volume reduction for cases where solvent extraction or ion ex- change methods are not applicable. Preparation of sources for energy analysis. Preparation of extrcmely thin sources for highest resolution alpha energy analysis, Preparation of high- quality thin samples for alpha energy measure- ments. 1- Advantages Rapid, convenient, quantitative. Easier to get uni- form spreading. Organic may not have refractory impurities, Relatively fast, easy method, Very thin, uniform films are attainable. Method can be made quantitative, Excelient sources - any kind of backing may be used. Very good sources obtainable. Resist- ance heated strip method applicable to routine lsotopic dilution analysis. Disadvantages Sample not uniformly spread if > 25 ug of material. May cause error due to self adsorption. Same as 1 + more difficult to prevent loss over edge of plate. May require edge heating or stippling small volume at a time, Co-precipitation and transfer may not be quantitative, Requires at least 0.3 mg of carrier. Self absorption losses may be serious. Requires special preparation of solution, requires rela- tively long time to prepare 1 sample, Only a small fraction of sample collected. Volatile compounds are difficult to handle and constitute a health hazard. Not a routine method. Not quantitative, however under favorable conditions ~ 90% yield can be obtained, Yield is usually about 50%. The apparatus is relatively large and expensive. (a)Cornpiled from References 206 and 189, Miller and Broun3276 give a detailed procedure for electrodepositon of Pu(VI) from 1-2 N KOH solution. The Pu was oxidized with ozone. This method has the disadvantage that all elements which precipitate in basic solution interfere with the deposition. A. 3 Other Methods El Guebely and Silfl:kca-land]'22 report an interesting method for preparation of ex- tremely thin Pu sources. The basis of the method is adsorption of Pu(IV) onto glass or metal plates from dilute (~0.01 M) HCIl solutions, presumably as the polymeric form. The method is not quantitative. Sa.I:".h..':n:'tseva347 reports that adsorption of Pu(IV) is 97- ! t0 1077 M HNO, solutions. Carswell and MilfiteadB1 made thin sources of U and Pu by electrostatically . 98% complete on Pt from 10~ focussing a jet of the material to be plated which was dissolved in a volatile solvent. B. Counting The subject of the determination of the amount of alpha radioactivity has been re- viewed by JnsmffeyzoEi and recently by Johnson et a.l.,z13 169 and Hanna. These accounts should be consulted for details of the various detection systems and literature references. Table VI-31 lists the major types of counting systems with applications, advantages, and disadvantages of each. The ratios of the isotopes of Pu can be determined by making use of the difference in the energies of the alpha particles in alpha pulse analysis. The isotope Pu236 is very useful as a tracer in this method. This isotope is pre- pared by the reaction 0?3 (4, n) Np236_E . 36 using highly enriched 1235 1o make the Pu23f 4g pure as possible. Since Pu236 is not made by any neutron reaction on U, an unspiked sample need not be run if the Pu236 is isotopically pure. Since the alpha energy Pu236 occurring isotopes (Pu239, Pu‘?40 238 is higher than that of the other commonly ), care must be taken that the added Pu236 activity is not very much greater than the activity of the other Pu isotopes. The reason . and Pu for this precaution is that imperfections in the sample and detecting instrument always result in low-energy alpha particles which appear as a continuum or low energy ''tail" in the spectrum. The subtraction of this tail becomes difficult if higher energy isotope pre- dominates. C. Other Methods 242 as the tracer and a mass spectrometer as the detecting instrument. Highly enriched Pu242 is a product of 239 39 Another isotopic dilution method uses the rare isctope Pu long reactor irradiations of Pu -Pu240 isotopic ratio must be made if the specific A determination of the Pu2 activity of a particular sample is needed. This determination must be made by meang of a mass spectrometer since the alpha particle energy of these 2 isotopes is the same. Schwendiman and Healy360 have described a nuclear emulsion technique for low- level Pu analysis. Nielsen and Bea:s.lejyrs03 have reviewed the radiochemical determination of Pu in biological materials and include a critical comparison of various counting systems. 29 001 TABLE VI-31. Techniques for Measuring Alpha Radioactivity. Method Total Alpha Activity Air ionization chamber I'ree-electron-gas ionization chamber (A, A—COZ, He, Nz, ete,) Alpha proportional counter Scintillation alpha counter Low-geometry counters Nuclear Emulsions Application Total assay -~ survey instrumentas, Total assay. Total assay. Total assay. Total assay. Total assay. Advantages Simple, easily repaired and cleaned, reliable, inexpensive, Sharp pulses permit high count rates and tolerance to B activity. Not micro- phonic, Reliable and stable. A known relatively unchanging geometry, High signal-to-nois¢ ratio, good B discrimination, Not at all microphonic. Very low background, Can count sources of greater activity. Count- ing rate not so sensitive to sample thickness. Reproducable and reliable. No low-angle back scatter- ing correction. Great sensitivity and stability. Very simplce apparatus. Disadvantages Long decay time of pulse makes inherently wide pulses - limited to low counting rates. Low tolerance to B activity. Signal-to-noise inferior to proportional counters, therefore more prone to spurious counts. Must be corrected for low-angle back scattering. Count rate sensitive to applied voltage., Requires pure gas for stability. Difficult to maintain stability for long periods. Lower tolerance to 8 radiation than ionization chamber or proportional counter, Greater sensiti- vity to sample size, and position. Not suitable for low activity. Sensitivity to sample posi- tion and area. Limited accuracy, consider- able technique required in ex- posing and developing emulsions. Counting tracks is time con- suming and tedious. 101 TABLE VI-31, Techniques for Measuring Alpha Radioactivity (Cont'd) Method Alpha Energy Measurement Magnetic deflection alpha spectrometer Total ionization and pulse analysis, I'risch grid ionization chamber Semiconductor charged particle detector Application Energy measurement - mainly for determination of energy spectrum. Energy measurement - determination of iscotope ratios. Energy measurement - isotope ratios. Advantages Very high precision and accuracy. Convenient, easy to use. High geometry - up to 50%. Tolerates large area sources, Resolution can be improved by collima- tiom. Very convenient - capable of high resolution, Disadvantages Large, expensive equip- ment. ‘Requires photo- graphic technique for recording data. Count- ing tracks is tedious and time-consuming. Very low geometry. Thin sample required. Requires gas purifica- tion. Requires low geometry for high resolution, Detector may become irreversibly contaminated by volatile radioactivity. Solvent extraction of Pu into a liquid scintillator has been proposed aa a method to 135, 403 The determination of 256 eliminate source preparation in radiochemical procedures. the B activity of ZE"u241 in low-level biological samples by this method has been reported. The incorporation of a scintillator in the polymerization of an ion-exchange resin has been ::-el:gi)rtedl'72 (see page 81 for details). Scintillation counting of the weak 0.4 MeV gamma-ray in Puz'?'9 by Nal detectors has been used to monitor the concentration of Pu in process strea.ms.123 VI. SAFETY CONSIDERATIONS Hazards to personnel who work with Pu in the leboratory arise primarily from two causes. First, Pu is extremely poisonous becruse of its high specific alpha activity, long biological half-life, and tendency to concentrate in the bone. Second, inadvertent criticality may occur. A full discussion of these hazards is beyond the scope of this re- view, but some general comments concerning precautions and techniques can be made. The subject of personnel monitoring and radiation surveying has been treated by Mt:;rg‘an.291 Appleton and Dunster32 bave writien a manusl on the safe handling of Pu. A. Radioactive Safety The primary hazard is due to the posgibility of ingestion, since the alpha particles are easilglr shielded and the gamma rediation associated with the common long-lived lsotopes is slight. The hazard is better stated in terms of the activity level rather than the mass, since the biological damuge is done by the alpha radioactivity and the isotopic composition of Pu varies widely. Table VII-32 lists body burdens and maximum per- missable concentrations (MPC) of Pu isotopes for continuous occupational exposure. These data are taken from the National Bureau of Standards Handbook 69, which should be consulted for details. TABLE VII-32. Health Hazard Data for Plutonium Isotopes. . Maximum Permissable Maximum Permigaasble Concentration for 40- Body Burden in Bone hour week Isotope (microcuries) (microcuries/ecc) Water Air Pu23? goluble 0.04 1074 2 x 10712 py238 p 240 242 insoluble —_— 8 x 10-4 (@) 3 x 10-11 ®) Pu??! goluble 0.9 7 X 1073 s x 10”11 insoluble — 0.04 (&) 4 X 1078 ® (a)Assuming the gastiro-intestinal tract to be the critical organ. (b) Assuming the lung to be the critical organ 102 The most common control practice is total containment of high activities of alpha-emitting isotopes by means of an enclosure which is maintained at a negative air pressure with respect to the laboratory atmosphere. Operations are done either with remote manipulators or with arm length gloves gealed to the enclosure, In an intermediate or high-level alpha activity laboratory, a variety of auxiliary equipment and practices in addition to the primary enclosure of the activity, are necessary to insure personnel safety. Among these are: 1. Adequate monitoring of the accidental release or "spilling" of radioactivity. This monitoring can be done by hand-held survey instruments, by continuous filtering and monitoring of the laborat-ory air, and by persocnnel monitoring instfu.ments placed at exits to the working area, 2. Protective devices and clothing. In most high-level radiochemical labora- tories, special clothing is part of the laboratory practice. The availability of respirators to prevent inhalation of airborne radioactivity in the event of a spill is esgential. 3. Procedures for normal operation of the laboratory as well as emergency procedures must be worked out in advance and understood by all personnel, ""Good housekeeping," or the maintainance of a clean and orderly work space, should be especially emphasized. The kind, amount, and distribution of protective devices, as well as laboratory practices for normal and emergency operation, vary considerably in detail from laboratory to laboratory. This very brief introduction to the subject of the handling and manipulation of large amounts of alpha activity iz intended to serve mainly as a warning to the uninitiated. The subject of enclosures for radicactive materials is treated fully in a review by Garden and Nielsen, 142 Low activity can, of course, be handled in an ordinary radiochemical laboratory. The limit beyond which total containment becomes a necessity is not very well defined. The concentration of the alpha-active material, as well as the nature of the operation and the skill and care of the operator, are factors which must be considered. At the level of one microcurie, ordinary laboratory procedures can be done if reasonable care is taken, while at higher levels the operations become more and more limited. At the millicurie level total containment becomes necessary for any chemical operation. In any case, proper monitoring of the activity is essential. B. Criticality Safety This hazard is most generally met in the radiochemistry laboratory bjr only permitting an "always safe'' amount of Pu in any room or area. This is an amount which will not be a critical mass in any configuration or dispersed in any medium, While the determination of the always-safe amount in a particular situation is beyond the scope of this review, Table 32 gives basic data for Pu239, This table was ex- tracted from the USAEC Publication "Nuclear Safety Guide" *4% sulted for further information on this subject. which may be con- 103 TABLE VII-33. Basic Data for Criticality Hazard for Plutonium-239. Mass of Isotope (kg) which is maximum Form of Isotope Recommended for Safety Minimum Critical Metal, & phase(a) 2.6 5.6 Metal, 6 phase(a) 3.5 7.6 Solution 0.22 0.51 (a) The metal is assumed to be surrounded by a thick hydrogenous layer. 104 VIII. COLLECTION OF PROCEDURES A. Introduction The literature of Pu is replate with radiochemical and analytical separation procedures. A survey disclosed 54 papers with procedures which were written in enough detail to do justice to the name, and many more methods which could easily be developed into procedures by making the directions quantitative or more complete. Of the 54, 26 survived screening and are included in this collection. The basic criteria for screening were fourfold: (1) distinctivenegs in chemistry, (2) completeness in detailed instructions, (3) generality in application, and (4) utility. In some cases a rather arbitrary choice had to be made between procedures which met these criteria equally well, The procedures are divided into (1) general radiochemical procedures, (2) special purpose separation procedures, and (3) urinalysis procedures. The procedures in the first group are concerned with purifying Pu from other alpha emitiers and from fission products sufficiently for the purpose at hand, usually for alpha counting or alpha pulse analysis. The starting materials range from reactor target dissolver solutions of varying ages to fresh samples of nuclear explosion debris to very dilute environmental samples. There are 13 of these procedures included. The second group of procedures ig concerned with a specific separation involving Pu. Two examples are the separation of Np and Pu and the removal of Pu before analysis for impurities in Pu metal. Urinalysis is a separate category, primarily because there are so many pro- cedures in the literature, all purporting to do the same thing. The chemistry after the initial separation step is, of course, similar to that in the other categories. The urinalysis procedures included were chosen primarily for distinctiveness of chemistry. B. Listing of Contents General Radiochemical Procedures Procedure Author No. (principal) Title or method Page 1. Welch Determination of Pu when large amounts 108 of Fe and Cr are present (LaF3 method) 2. Moore Separation and determination of Pu by 112 TTA extraction 3. Maeck Separation and determination of Pu in 114 - U-fission product mixtures (extraction of quaternary alkylammonium-plutonyl nitrate complex into hexone-TTA extraction 4. Morrow Plutonium (anion exchange) 116 5. Hoffman Plutonium (anion exchange) 118 105 Procedure No. 6. Oa, 9b, 10. 11. 12. 13. Author (principal} Hart (No author) Rider Lingjaerde Rydberg Rydberg Geiger Sheidhauer Kooi Special Procedures 14, 15, 16. 17. 18. Larsen Trowell Trowell Jackson Zagrai Urinalysis Procedures 18. 20. Brooks Perkins Title or method Separation and determination of Pu from U and fission products in irradiated reactor targets (anion exchange — TBP extraction) Pu (CeFy4-LaFjg cycle, TBP extraction, anion exchange% U and Pu determination in highly irradiated fuel. (Hexone extraction, TTA extraction) Pu from irradiated U (cation exchange, anion exchange) Separation of Pu from U and fission products (BiPQg4 precipitation, TTA ex- traction) Separation of Pu from U and fission products (adsorption of Zr-Nb on silica gel, preciditation of CuS, TTA extraction) U and Pu from environmental sampleg of soil, vegetation and water (TBP extraction) Pu from environmental water samples {chemisorption on Can, TTA extraction) Pu from environmental water samples (BiPO4 precipitation, co-extraction with ferric cupferride) Separation and spectrophotometeric determination of Pu from U-Pu-fission element alloys (TBP extraction from HCl solution) Separation of Pu before spectrographic analysis of impurities in Pu metal (anion exchange Separation of Pu before spectrographic analysis of impurities in high purity Pu metal (extraction chromatography using TBP) Separation of Np and Pu by anion exchange Separation of Np and Pu by cation exchange chromatography Determination of Pu in urine (ferric cupferride extraction) Determination of Pu in urine (PrF3 pre- cipitation, TTA extraction) 106 Page 122 124 126 129 132 134 137 140 142 144 148 149 150 153 155 Procedure No. 21, 22. 23. 24. 25. Author {principal) Everett Bokowski Campbell Weiss Bruenger Title or method Determination of Pu in urine (LaFj precipitation, TTA extraction) Determinaiion of Am in urine in the presence of Pu (BiPO, precipitation, LaF'g precipitation extraction of Pu into di-(2-ethylhexyl) phosphoric acid Determination of Pu in urine (alkaline earth phosphate precipitation, anion exchange Determination of Pu in urine {(co-crystal- lization with potassium rhodizonate, LaF g precipitation, anion exchange) Determination of Pu in urine and bone ash (extraction by primary amines from HoSO0y solution) 107 164 166 Procedure 1. Determination of Pu in solutions containing large amounts of Fe and Cr. G. A. Welch et al. (Ref. 446). Qutline of Method Hydroxylamine is added to the sample to reduce plutonium and chromium to the trivalent state. The acidity of the solution is adjusted and lanthanum nitrate carrier added. Lanthanum fluoride is precipitated by adding a limited amount of ammonium fluoride and carries the plutonium with it, By strictly controlling the amount of fluoride added the precipitation of iron and chromium is prevented. The precipitate is separated by centrifuging, washed and mounted on a {lat stainless-steel counting tray, and the a-activity measured with a scintillation counter calibrated against standard sources. Reagents All reagents are analytical reagent quality where available. 1. Ammonium hydroxide, 9M 2. Nitric acid, 2M 3. Hydroxylamine hydrochloride, 5% w/v 4, Lanthanum nitrate solution, 5 mg La/mil. Digsolve 7+ 8 g of lanthanum hyxahydrate in 500 ml of distilled water. 5. Ammonium fluoride solution, 12+ 5% w/v Store in a polythene bottle, 6. Cellulose lacquer. Dilute "ZAPON" lacquer with amyl acetate, 7. Standard Pu solution, 05 ug/ml. Dilute a solution of known Pu concentration. The exact Pu concen- tration of the diluted solution need not be known, but the isotopic constitution should be eséentially the same as that of the samples requiring analysis. Eguipment 1. a-scintillation equipment, Type 1093A or B scintillation unit with associated equipment, 2, Counting trays. Stainless steel, flat, mirror finish, 1-1/16 in, diameter, Prepare for use by heating in a flame until the surface is straw coloured. Allow to cool and paint a ring of cellulose lacquer round the edge. Allow the lacquer to dry and store the p:t.'epared trays in a closed container, Procedure 1. Transfer a suitable portion of the sample to a 3 ml glass centrifuge tube. Wash out the pipette with 2M nitric acid and add the washings to the tube. [Note (a)]. 108 10. 11. 12. 13. Notes (a) (b) (c) (d) Add 0- 15 ml (3 drops} of hydroxylamine hydrochloride solution and stir well. [Note (b)]. Adg 9M ammonia solution until a faint permanent precipitate is formed, Add 2M nitric acid until the precipitate just redissolves, then add 0-1 ml (2 drops) in excess. Add 0-1 ml (2 drops) of lanthanum nitrate solution (5 mg La/ml), dilute the solution to about 2 ml and stir well, Add 0-15 (3 drops) of 12+5% ammonium fluoride solution, stir well and centrifuge for 10 min, Remove the supernatant liquor [ Note (¢)] with a transfer pipette [Note (d)] and wash the precipitate twice by stirring with a mixture of 1 ml of water, 01 ml of 2M nitric acid and 0*25 ml of ammonium fluoride solution. After each wash, centrifuge for 5 min before removing the supernatant liquor. Slurry the precipitate with 2 drops of water and transfer it to a prepared counting tray with a transfer pipette. Do not allow the slurry to enter the wider part of the tube. [Note (e)]. Wash the centrifuge tube with 5-10 drops of distilled water and transfer the washings and the residual precipitate to the counting tray. Spread the slurry evenly over the tray within the cellulose lacquer ring and break up agglomerations of solid matter with additional drops of water where necessary. Dry the slurry beneath a radiant heater and ignite the counting tray in a flame to a dull red heat to drive off excess ammonium fluoride and burn off the ""ZAPON" ring. Allow to cool. Measure the activity on the counting tray using stable a-scintilla- tion equipment [ Note (f)]. Using a clean counting tray, measure the background of the equip- ment and correct the counting rate of the sample source for back- ground, [ Note (g)]. Calculate the concentration of Pu in the sample solution from the relation Pu (dpm/ml) = 100 Cel/EE2 V [Note (h)]. Usually not more than 500 gl should be used. After each addition of reagent the mixture should be well stirred with a platinum wire, About 0-1 ml of liquid should be left behind at this stage and after each wash to ensure that the precipitate is not disturbed, A piece of glass tubing drawn out to a capillary and attached to a rubber teat, i08 (e) The precipitate is easily washed from the narrow portion of the tube, but it is difficult to remove it if it is allowed to dry on the wider part of the tube. (f) The stability of the counter may be checked statistically using a standard plutonium source (see Appendix IT). {g) The background should not normally exceed 2 cpm, (h) The ratio E;/Eg may be replaced by the ratio of the counting rates of the plutonium control source at the time of standardizing and at the time of sample count provided that the same control source is used, Where C = Counting rate of sample source corrected for background as cpm. V = Volume of sample in ml, E = Percentage efficiency of the counting equipment for the standard plutonium source (Appendix I). E1 = Percentage efficiency of the counting equipment for the Pu control source at the time of calibration (Appendix I). E2 = Percentage for the Pu control source at the time of sample count (para. 11). APPENDIX I. Calibraiion of the e-counting equipment, Using 500 ul of the standard Pu solution (0.5 ug Pu/ml) (see Section B, para. 7) obtain a series of standard sources by the procedures described in Section D, paras. 2 to 10. ' Measure the counting rate of each source and correct for background. Determine the disintegration rate of each source using an a-proportional counter of known efficiency. (This efficiency is measured with a source calibrated in a low geometry counter.) Calculate in each case the ratio Corrected counting rate as cpm Disintegration rate as dpm and calculate the counter efficiency E = 100 mean ratio. APPENDIX II, Preparation of the Pu control source, Prepare a standard Pu solution containing about 10 pg/ml of Pu. Transfer approximately 20 mg of this solution from a weight pipette to a clean prepared counting tray, ensuring that the liquid forms a small spot in the center of the tray. Evaporate the liquid on the tray fo dryness by warming gently beneath a radiant heater. Allow the tray to cool and add just sufficient of a solution containing 10 ug/ml of collodion in acetone to cover the spot of activity. Allow to dry at room temperature, Determine the counting rate of the control source and determine the disintegration rate using an a-proportional counter of known efficiency. Calculate the efficiency of the couniing equipment, - 110 100 Corrected counting rate (as cpm) Efficiency = Disintegration rate (as dpm) NOTE: The procedures of Appendix I and Appendix II are carried out at the same time and E the efficiency of the equipment for the control source at the time 1 J of calibration of the equipment, is obtained. The counting rate of the control source is measured with each set of sample determinations and E2 , the efficiency of the equipment at the time of sample count, is calculated using the previously obtained disintegration rate, Procedure 2. Separation and determination of Pu by TTA extraction., F, L.. Moore and J. E. Hudgens, Jr. (Ref. 287). Outline of Methond The_sample is pre-treated if necessary, with either I—_INO3 or by precipita- ting LaF g and dissolving in Al{NO3)3-HNO,. The pre-treatment destroys any polymer which may be present and assures the proper valence state (IV) for the TTA extraction. Pu(lV) is extracted from 2 M HNOg and stripped into 10 M HNO,, evaporated onto a plate, and counted. Yield is quantitative. Reagents Hydroxylamine hydrochloride, 1 M, is prepared by dissolving 68.5 grams of C.P. grade end diluting it to 1 liter. Sodium nitrite, 1 M, is prepared by dissolving 69 grams of C. P. grade and diluting it to 1 liter. 2-Thenoyltrifluoroacetone-xylene 0.5M, is prepared by dissolving 111 grams of the ketone and diluting it to 1 liter with C. P. xylene. (2-Thenoyltrifluoro acetone may be obtained from Graham, Crowley, and Associates, Inc., 5465 West Division St., Chicago 51, Iil.) Pretreatment Nitric acid method. A suitable allquot of the sample solution is pipetted into a 100-ml volumetric flask containing 13 ml of concentrated nitric acid. The solu- tion is heated carefully to a low boil on a hot plate and the temperature is held just under boiling for 5 min. The solution is then made to a known volume with distilled water, The nitric acid concentration of this solution should be approximately 2M. Fluoride method. A suitable aliquot (1 ml) of the sample solution is pipetted into a 5-ml centrifuge cone, After addition of 0.4 ml of concentrated hydrochloric acid and 0.1 ml of lanthanum carrier (5 mg per ml) the solution is mixed well. Then 0.3 ml of hydroxylamine hydrochloride (5M) and 0.4 ml of hydro- fluoric acid (27 M) are added and the solution is stirred with a platinum stirrer, After a 5-min digestion at room temperature, the solution is centrifuged for 3 min. Next, 0.1 ml of lanthanum carrier (5 mg per ml) is added and the supernatant is stirred, care being taken not to disturb the precipitate.” After another 5-min digestion at room temperature, the solution is centrifuged for 3 min and the supernatant is removed with mild suction. The precipitate is washed twice with 0.5-ml portions of 1M nitric acid — 1 M hydrofluoric acid, centrifuging each time for 3 min. The lanthanum fluoride precipitate containing the Pu is then dissolved in 0.3 ml of 2 M aluminum nitrate and 1 ml of 2M nitric acid. This treatment not only aids in depolymerizing Pu(IV) but offers a method of removing the Pu from interferences, as sulfuric acid, before performing the extrac- tion. The liquid-liquid extraction technique described in this paper has been applied successfully for several years to the purification and isolation of Pu isotopes. 112 Procedure The choice of the sample gize is governed by the magnitude of the con- centration of Pu activity and of the beta and gamma ray emitters in the original solution. The presence of high levels of radiocactivity must be congidered because of the health hazard involved and because a beta ray counting rate of over 109 counts per minute will interfere with the alpha counting on the Simpson proportional alpha counter, One ml of the sample solution (pretreated if necessary) is pipetted into a 10-ml beaker., Three ml of 2 M nitric acid and 1 ml of 1M hydroxylamine hydro- chloride solution are added. The solution is mixed thoroughly and heated at approxi- mately 80°C. for 5 min, The volume of the solution is adjusted to approximately 4 ml by the addition of several drops of 1 M nitric acid. The solution is transferred to a 30-ml separatory funnel using 2 ml of 1 M sodium nitrite, mixed thoroughly and allowed to stand until gas evolution ceases. The aqueous phase at the time of extrac- tion should be approximately 1 M in nitric acid. The solution is extracted for 10 min with an equal volume of 0.5 M 2-thenoyltri- fluoroacetone-xylene. When the two phases have disengaged, the aqueous phase is drawn off and discarded. The organic phase is washed by mixing with an equal volume of 1 M nitric acid for 3 min. After the phases have settled, the aqueous wash solution is discarded, care being taken not to lose any of the organic phase. The Pu is then stripped from the organic phase by mixing thoroughly for 2 min with an equal volume of 10 M nitric acid. If the aqueous strip solution is too high in gamma radicactivity for alpha measurement, the last traces of radiozirconium and protactinium may be removed readily by a 5-min re-extraction of the 10 M nitric acid strip solution with an equal volume of 0,5M 2-thenoyltrifluoroacetone-xylene. Pu remains quantitatively in the aqueous phase, The small percentage of iron extracted (produces a red color) remains in the organic phase when the Pu is stripped into 10 M nitric acid. The aqueous strip solution is drawn off into a centrifuge tube and centrifuged for 1 min, A suitable aliquot is pipetted onto a platinum (or stainiess steel) plate and evaporated to dryness under an infrared heat lamp, The plate containing the evaporated sample aliquot is heated to a dull red heat over a Fisher burner to destroy organic matter and counted in a suitable alpha counter. In this laboratory, the methane flow propor- tional alpha counter is used almost exclusively, 113 Procedure 3. Separation and determination of Puin U — fission product mixtures. W. 8. Maeck, G. L. Booman, M. E. Kussy and J. E. Rein (Ref. 261). Outline of Method Plutonium is oxidized to Pu(VI) with permanganate and quantitatively extracted as a tetraalkylammeonium complex into methyl isobutyl ketone from an acid- deficient aluminum nitrate salting solution. Pu is stripped from the organic phase and reduced to Pu(lll) with a hydroxylamine-iron(Il) mixture, oxidized to Pu(IV) with nitrite, then quantitatively extracted into TTA. Yield Overall recovery of Pu is 98.8%. Decontamination Overall figsion product decontarnination is greater than 1 X 104; U carry-through is less than 0.05%. Reagents Reagent grade inorganic chemicals, Eastman Kodak Co. White Label tetrapropylammeonium hydroxide, and thenoyltrifluoroacetone obtained frorm Peninsular Chemical Research, Inc., Gainesville, Fla,, were uged without purification. Aluminum nitrate salting solution. Place 1050 grams of aluminum nitrate nonahydrate in a 2-liter beaker and add water to a volume of 800 ml. Warm on a hot plate. After dissolution, add 135 ml of concentrated (14.8 N) ammonium hydroxide and stir for several minutes until the hydroxide precipitate dissoclves. Cool below 50°C. Add 50 ml of 10% tetrapropylammonium hjrdroxide reagent and stir until dissolution is complete, Transfer to a 1-liter volumetric flask and dilute to volume with water. The 0.2 M ferrous sulfate and 0.22 M sodium nitrite solutions should be pre- pared fresh daily, The 1.25M hydroxylamine hydrochloride and 0.05M potassium permanganate solutions are stable for a month or longer. The potassium perman- ganate solution is stored in a dark bottle. Unless otherwise stated, the Pu levels in ex-tractibns were approximately 100,000 disintegrations per min (dpm). The stock solution was prepared from high purity Hanford metal dissolved in 6 N hydrochloric acid. The isotopic composition of the metal was 95,40% Pu239, 4,31% Pu240, 0,28% Pu24l, and 0.01% Pu242, Equipment The methyl isobutyl ketone (4-methyl-2-pentanone) extractions and strips were made in 15 X 125 mm test tubes with polyethylene stoppers. An end-for-end extraction wheel was used. Thenoylirifluoroacetone extractions were made in 50 ml centrifuge cones with a motor-driven wire stirrer. The samples plates were 1-in. stainless steel. An alpha scintillation counter was used for gross counting and a Frisch grid chamber, 256-channel analyzer system, for pulse height analysis, Procedure. Add 6 ml of salting solution to a test tube containing 0.1 ml of 0.05 M potassium permanganate, Pipefte 1 ml or less of sample into the tube. Add 3 ml of methyl isobutyl ketone, stopper the tube, and extract for 5 min on the extraction wheel. Centrifuge to facilitate phage separation. Pipette 3 ml of 3.125M nitric acid, 2 ml of 1.25 M hydroxylamine hydrochloride, and 2 ml of the above organic phase into another 15 X 125 mm test tube. Stiopper the tube and strip for 10 min, and then centrifuge. Carefully transfer 2 ml of the aqueous strip phase to a 50-ml centrifuge tube containing 0.1 ml of freshly prepared 0.2 M ferrous sulfate and allow the mix- ture to stand for 5 min. Add 3 ml of freshly prepared 0.22 M sodium nitrite and let stand until gas evolution ceases. Add 5 ml of 0.5 M thenoyltrifluoroacetone-xylene and stir vigorously for 20 min. Remove an aliquot of the organic phase and dry on a planchet under a heat lamp. Ignite and count. 115 Procedure 4. Plutonium R. J. Morrow (Ref. 293) Outline of Method The Pu is co-precipitated from acid solution with La{OH)3 with NH;OH. The precipitate is washed with NaOH solution, dissolved and the co-precipitation repeated using La(IOg)g as the carrier. The hydioxide precipitation is repeated and the Pu adsorbed on an anion resin column from 8 M HNOg. The column is washed successively with HNOj3 and 2 portions of 10 M HCl. Finally, the Pu is eluted with a mixture of HCl and HI and mounted for counting, Purification This procedure is designed primarily for separation of Pu samples to be alpha-counted; it does not yield samples highly purified from beta- and gamma- emitters. Samples containing 1013 - 1014 atoms of Pu have been isolated from four- day old solutions of 5 X 1013 figsions. No foreign alpha activities could be detected, and the beta content was 107 dpm or less, Yield 60% if an electroplating technique is used for the final step, and 35% if vacuum volatilization is used. Procedure One operation can do 12 samples in 6 hours, exclusive of volatilization or electroplating. 1. To an acid solution of mixed activities in a plastic centrifuge cone add ~1 mg La*3 carrier and an appropriate amount of standardized Pu alpha-emitting tracer, the isotope added and its level of activity depending upon the isotope sought afid its estimated level of activity. Add 2-3 drops sat. NaNO2 solution and heat in a hot-waler bath for five minutes. 2, Add enough conc. NH4OH to make the solution basic. Stir, and digest at 60°C in a hot-water bath for five minutes. Centrifuge and discard supernatant solution. 3. To the precipitate add 5 ml 25% NaOH solution, Siir and digest for 5 min at 60°C in a hot-water bath, Centrifuge and discard the supernatant solution, 4. The hydroxide precipitate is then dissolved in a minimal volume of 3M HCl and a volume of 0.5 M HIOj3 is added of the order of 4-5 times the volume of HCI solution. 5. The precipitate is then digested for 10 min in a hot water bath. §. The sample is centrifuged and the supernatant solution is decanted, after which the precipitate is washed with 0,1 M HIOgq. 7. The sample is again centrifuged and the supernatant golution decanted. 116 8I 10. 11. 12, 13. 14. A minimal amount of concentrated HCl is used to dissolve the precipitate with stirring. After dissolution the sample is precipitated with sodium hydroxide and centrifuged. The supernatant solution is discarded and the precipitate is washed with HyO and centrifuged after which the supernatant solution is again discarded. To precipitate, add enough 8 N HNOj saturated with HgBOg (usually ~5-10 drops) to dissolve. Heat in hot-water bath if necessary. Pipet the solution onto a 3 mm i.d. X 6 em long Dowex A-1 (1 X 8) anion exchange resin column (previously washed thoroughly with 8 N HNOQ,) and discard effluent. Wash column twice with 2 ml 8 N HNOg each time, and twice with one ml portions of 10 N HCl, Disgcard all washes. To column add 2 ml of a solution 10 N in HCI and 0.5 N in HI, collect- ing eluate in a 50 ml Erlenmeyer flask or a 40 ml centrifuge tube, Either of two alternatives may now be followed: a. Boil the solution to a very small volume and pipet the remainder onto the central depression of the tungsten filament of vacuum bell jar apparatus. Carefully boil the remaining solution to dryness in the filament in air by application of current through filament, Evacuate system and flash the contents of the filament onto a platinum disc located about 1/4 in. - 1/2 in. from filament. b. Evaporate the solution to dryness and redissolve residue with three drops of conc. HCl, Transfer to an electrolysis cell suitable for 1-in. diameter plates. Rinse tube successively with three more drops of conc. HCI and three drops of water adding the rinses to the solution in the cell, Carefully adjust acidity to the methyl red end point with cone. NH,OH, then make barely acidic with two drops of 2M HCl. With a 1-in, Pt disc as cathode, and a volume of roughly 1 to 2 ml, plate at 5-6 volts with about 2.5 amps for roughly fifteen min. Before stopping the current, add 1 ml conc. NH,OH. Shut off current, remove solution and wash the disc first with water, then with acetone. Mild flaming of the plate is desirable. 117 Procedure 5, Plutoniurmn D. C. Hoffrnan (Ref. 185) QOutline of Method The essentially gpecific procedure for Pu utilizes the almost quantitative carrying of Pu(IV) on lanthanum fluoride and also the great difference in ability of Pu(Ill}) and Pu (IV) in 12 M HCl medium to be absorbed on a Dowex A-1 anion resin, One cycle of the procedure serves to separate Pu from other o-emitters, and two cycles usually gives complete decontamination from B-emitting fissian products. The initial lanthanum fluoride precipitation, carried out in the presence of hydroxylamine, is an excellent volume-reducing step and also eliminates many elements (notably iron) which may interfere in the subsequent adsorption of Pu on the resin column, After dissolution of the lanthanum fluoride precipitate in 12 M HCI1, adsorption on the anion resin column of Np, Pu, and any traces of Fe and U present is effected, while the rare-earths Am and Cm pass through the column. Pu is eluted from the column after reduction to Pu(Ill) with hydriodic acid; Np is not reduced to the +3 state and remains quantitatively behind. (A solution containing 15 ug of U235 was run through the procedure, and no fission counts above the usual background of 0.1 - 0.2 smidgins (1 smidgin = 10-6 mg) could be detected.) The Pu is collected directly from the resin column on 2-in. Pt plates which are flamed, o-counted, and, if necessary, pulse-analyzed., The plates are usually very clean and may be @-pulse-analyzed with a resolution of 1 - 1.5%. Samples are usually run in quadruplicate and yields are determined in one of two ways. Pu236 tracer to the extent of about one-fourth to one-half of the total Pu @ -activity expected may be added to one or two of the original aliquote, On completion of the analysis, the fraction of Pu236 in the sample is determine by pulse analysis, thus permitting the calculation of yield. Yields may also be determined by spiking two of the four samples with a standardized solution of Pu activity which is at least five times as active as the aliquot to be analyzed. The average of the number of cpm in the two unspiked samples is subtracted from the average in the two spiked samples. The resulting value divided by the number of cpm in the spike gives the yield. The chemical yield is usually about 97% and for a set of four aliquots analyzed simultaneously is constant to within +1%. In analysis of solutions of very high ionic strength the yields are somewhat lower (90-97%), probably because under these con- ditions the lanthanum fluoride carrying step is less efficient, Quadruplicate analyses can be performed in 3 h, Reagents La carrier: 5 mg La/ml (added as La(NO,), - 6H,0 in H,O) Pu?36 standardized tracer solution (in 3 N HCI), or Pu standardized spike solution (any mixture of Pu isotopes in 3N HCl). HCl: cone. (12M) HCl: 3M 118 HF': conc. HF-HNOg: equal volumes of 2 M solutions H3B03: saturated solution NHoOH - HC1: 35% by weight in H20 Solution I: 0.1 ml conec. HNO3 per 15 ml conc, HC1 Dowex A-1 (10% cross-link, Nalcite SBR) anion resin slurry in H20. Preparation The 200-400 mesh moist solid is washed about three times with successive poriions of water and conc. HCl, After each wash the resin is allowed to settle and the liguid decanted by siphoning or by means of a vacuum pipet. The resin is then stirred thoroughly with several times ita volume of water in a large gfaduated cylinder, and the following fractions are withdrawn on the basis of sedimentation rates: < (1 cm/min, <5 cm/min, <10 cm/min and > 10 cm/min, The <10 cm/min fraction is employed in the procedure. HI stock solution. Distill HI (Mallinckrodt analytical reagent grade, 5.5M in HI, 1.5% H3P02 preservative) under nitrogen. The HI cannot be used with- out distillation, since the H‘.‘,‘PO2 preservative appears to cause the eluted drops to attack the Pt coliection disks and make the samples unguitable for pulse analysis, Commercial preparations of HI without preservative usually contain enough free iodine to make them unsuitable. Even after storage under nitrogen, distilled HI is slowly oxidized. Oxidation is inhibited by the addition of sufficient hydrazine (up to 20% by volume of 64-84% NyH, in H20) to decolorize the HI solution. The final solution is about 4.4 M in HIL . HI-HCI elutriant. 1 ml of HI stock solution is added to 9 ml of conc, HCI to give a solution about 0.44M in HI. The precipitaté which resulté from the hydrazine present is removed by centrifugation and the supernate is saturated with gaseous HCI. The solution is permitted to come to equilibrium at room temperature before use and since the solution is readily oxidized, fresh reagent is required every few days. Equipment Centrifuge Block for holding centrifuge tubes Fisher burner Heat lamp Pt digks: 2 in, diameter Pt wire stirring rods Transfer pipets and syringes Vacuum trap for withdrawing supernates (optional) 10-cm glass ion exchange columns (see_* Note 4, Np procedure) (one per sample) ' 40-m]l conical centrifuges tubes: Pyrex 8140 (one per sample) 118 Procedure Step 1. Pipet the samples (2 M in HCl or HNO,) into 40-ml long taper conical centrifuge tubes. (1-ml aliquots are used if possible, although aliquots as large as 25 ml can be taken if necessary). If tracer or spike is added to 1 or 2 of - the samples, make the others up to the same volume with a solution of acid strength identical to that of the tracer or spike. Stir, Step 2. Add 1-2 drops of La carrier and then 2~4 drops of NH20H- HCl per ml of solution. Make the solution at least 2.5M in HF by addition of conc. reagent (Note 1). Agitate the solution and permit to stand for 5 min after the addi- tion of each of the above reagents. Step 3. Cén‘trifuge and digcard the supernate, Step 4. Wash the precipitate with about 0.5 ml of 2M HF-2M HNO solution. Stir, centrifuge and discard the supernate. 3 Step 5. Dissolve the LaF3 precipitate by adding 1 drop of saturated H3BO3 gsolution, stirring, and then adding conc. HCI to a volume of 1.5-2.0 ml, The solution may be warmed if necessary. Step 6. Transfer the solution to a 5-cm Dowex A-1 regin column (see Note 4 of Np procedure) which has been washed with 1-2 column volumes (Note 2) of Solution I (Note 3). Wash the centrifuge tube with two l—m.'l' aliquots of Solution I. The washes may be driven through the column with air pressure if so desired. The effluent solutions from these washes may be used for the Am and Cm determinations; if not to be so used the washes are discarded. Step 7. Wash the sides of the centrifuge tube with 1.5 ml of conc. HC], wash and remove the Pt stirring rods, centrifuge and pass the solution through the column with the use of pressure. Step 8. Add a few crystals of NH20H- HC] directly to the top of the resin column. (This helps to prevent immediate oxidation of the HI solution by any traces of HNO3 remaining on the column, ) Wash the centrifuge tube with 1.5 ml of cone. HCI1, transfer the washings to the column, and permit them to pass through. The column should not be permitted to run dry while air pressure is being applied to it, since air bubbles will be forced into the column and channeling and erratic elution of activity may occur, Step 9. . 1-2 ml of the HI-HCI elutriant is put on the top of the column and no pressure is applied during elution. The dark band of the elutriant may be seen migrating down the column, The activity appears to be concentrated about the lower edge of the elutriant band and most of it comes off in a 6- to 8-drop peak. However, to obtain quantitative ylelds, drop collection is begun on a 2-in. Pt disk when the band is about 0.8 cm from the end of the column, and collection is continued for 10-15 drops after the band has reached the end of the column. This allows for possible irregularities in the band or misjudgements regarding its position. The drops taken before the band reaches the end of the column are arranged on the periphery of the Pt disk, and those which are expected to contain most of the activity are collected near the center. The drops are not permitted to run together. 120 Step 10. Place the Pt disk under a heat lamp and allow the drops to evaporate. Heat the plate to red heat in an open flame and cool; @-count if the origifial aliquot was spiked, and pulse analyze and e-count if Pu236 tracer was employed (Notes 4 and 5). ' Notes 1. When an appreciable quantity of Fe is present, en'ou.gh HF must be added not only to complex this element (thus decolorizing the solution) but also to precipitate La carrier. 2. The column volume is defined as about one-half the volume calculated from the actual dimensions of the column, The column volume may, of course, be measured experimentally in each case if the interfaces can be clearly seen. 3. The presence of conc, HNO3 in Solution I is necessary to destroy the reducing properties of the original resin and thus avoid premature reduction of Pu(IV) to the tripositive state. 4, If it is desired to fisgsion count the Pu, plates may be prepared by taking the activity directly from the column. However, if any drops are permitted to run together giving an extreme ''bathtub effect," the figsion counting results are invariably toc low. To avoid such effects atiributable to sample thickness, the following procedure for plate preparation is employed. The Pu activity is evaporated on a 1-mil W filament under a heat lamp, but the filament is not flamed. It is then placed in a vacuum evaporating apparatus constrficted at this Laboratory. The chamber of the apparatus is evacudted to 5 X 10-4 mm or less of Hg pressure and the filament is heated rapidly several {imes to about 1300°C to remove readily volatile material. A 1-in, diameter collector plate is then placed in position directly above the sample (1/4 to 1/2-in, away) and the filament is heated to 2000°C for a few seconds to violatilize Pu. The Pt disk is then flamed and mounted for fission counting. The yields vary, depending upon the size of the sample being evaporated and also upon the distance between the filament and the disk, but are ugually about 40%. By careful control of the W filament tempera- tures, plates having no visible deposit and checking to within 0,1% are ordinarily obtained. 5. The Np activity whcih quantitatively remains on the column after elution of Pu may be removed in the following manner: Step 1: By means of pressure, run conc. HCI containing several drops of HNO3 per ml through the column until the dark color has been removed, Discard the effluent, (During this process the column may separate as a result of bubbling, etc,, but can be resettled by means of pressure.) Step 2. Wash the resin with conc, HCI and pressure, permitting the column to rebed itself, Step 3. Elute the Np with 0.1 N HCl, If the yield is very low after only one elution with 0,1 M HC], about three cycles of elution alternately with ¢,1 M HCI and conc. HCI usually give yields up to 85%. ' 121 Procedure 6, Separation of Plutonium from Uranium and Fission Products in Irradiated Reactor Targets R. G. Hart, M. Lounsbury, C. B. Bigham, L. P. V. Corriveau, F. Girardi (Ref. 167) Qutline of Method The Pu is adsorbed on anion exchange resion (Dowex 1) from 7-11 M HNO3 , the U and most of the fission products passing through. The Pu is then eluted by reduction with 1 M N'H20H- HNO3 and impu.rit_.ies are extracted into TBP while the Pu remains as Pu(IlI). The Pu is then precipitated as the hydroxide, dis- solved in HNO3 and extracted into TBP. Finally, the Pu is back-extracted by NHZOH . I-I'NO3 , This procedure describes two specific types of analyses to be done on 240 followed followed by @ precipitated as hydroxide, and dissolved in HNO3 for analysis. digssolved, irradiated, U targets. These are (1) isotopic dilution by Pu by mass spectrograph analysis, and (2) isotopic dilution by PuZBB pulse analysis. These analyses are described before the separation procedure is given, Procedure Total Pu, isotopic dilution with Pu240. Two aliquots, one containing ~ 800 ug of Pu and the other containing ~ 400 ug of Pu, are removed from the dissolver solution. Only the second aliquot need be measured accurately. To the second aliquot is added ~ 400 ug of Pu containing a high percentage of the heavier isotopes. This aliquot must be accurately measured and the Pu concentration and isotopic composi- tion must be accurately known. The samples are allowed to stand for 4 or 5 days to allow the spiked sample to reach isotopic equilibriurn:l and are then carried through the Separation procedure. The purified Pu is then mass analysed. From the isotopic compositions of the standard, the unknown and the mixture, and the total Pu content of the standard, it is possible to calculate the total Pu concentration in the unknown., 238 Total Pu, isotopic dilution with Pu Two aliquots, one containing ~ 100 pug of Pu and the other containing ~ 50 ug of Pu, are removed from the dissolver solution. Only the second need be meeasured accurately. To the second aliquot is added ~0.19 ug of Pu238, This aliquot must be accurately measured and the Pu238 digintegration rate of the solution must be accurately known. Both samples are diluted to 15 ml with 7 M nitric acid, and are allowed to stand for 4 or 5 days to allow the spiked sample to reach isotopic equilibr-iurn.2 The two samples are now carried through the Separation method and ¢-counting discs are prepared from each as described in the following section. From the ratios of Pu238 to Pu23? in the spiked and unspiked samples, the total disintegration rate of the standard Py238 solution, and the isotopic composition of ungpiked sample, it is possible to make an accurate calculation of the total Pu content of the solution. 1No detailed study has been made to determine the length of time required to reach isotopic equilibrium, but it is known that some considerable time is necessary, 2See Footnote 1, 122 Preparation of @-counting plates. An aliquot containing about 50 ug of U was transferred to a stainless steel source tray in the usual manner, The micropipette used was then washed three times with a solution of tetraethylene glycol (TEG) in dilute nitric acid (4 drops of TEG in 10 ml of 1 M nitric acid). The solution on the source tray was then evaporated to dryness under an infrared lamp and the disc was ignited to redness, The evaporation must take place very slowly to avoid decomposition of TEG by hot nitric acid. Two to three hours are necessary for the drying. Separation procedure (1) The aliquot, in 7-11 M nitric acid, was passed through a 1-ml column of 250-mesh Dowex 1 in the nitrate form to absorb the anionic Pu nitrate complex. (2) The uranium and fission products were washed through the column with 20 ml of 7.5 M nitric acid. The strong acid was then displaced with 1 ml of 1 M nitric acid. (3) An aliquot of the effluent containing ~40 mg of U was retained for U isotopic analysis and the remainder wasg discarded. (4) The Pu was eluted from the column with 4 ml of 1,0 M hydroxylamine nitrate. (5) The Pu solution was extracted five times with 2 ml portions of 30% TBP-solirol to remove any U left with the Pu, (8) The Pu was precipitated from the aqueous phase with concentrated ammonium hydroxide, dissolved in 100 A of concentrated nitric acid, diluted to 0.5 ml and extracted with two 0.5-ml portions of 30% TBP- soltrol,3 {7) The Pu was then backwashed from the organic phase with 3 half-volume 1 M hydroxylamine nitrate washes, precipitated with ammonium hydro- xide, washed once with water, and dissolved in 20 A of concentrated nitric acid. The solution was then diluted to 100 A with 1 M nitric acid. 3The TBP extraction is necessary to separate the plutonium from resin decompo- sition products. 123 Procedure 7. Determination of Pu (Ref. 447) Outline of Method This procedure used an oxidized CeF 4—reduced LaF3 cycle and extraction of Pu(VI) into hexone, in addition to two cycles of adsorption of Pu(lV) on anion resin from concentrated HCl and desorption by reduction with NH4I. Procedure 1. 10. Add 5 mg Fe' ' and 1 ml HNO, to the acid solution containing the Pu activity. Boil the solution down to about 3 ml and transfer to a 50-ml lusteroid tube, Make the solution ammoniacal to precipitate Fe(OH)3. Digest for a few minutes on a 75°C water bath. Wash the hydroxide with 5 ml water containing 1 drop NH4OH. Discard the supernate and wash. Dissolve the Fe(OH)3 in 3 drops HNO3 and dilute with water to a - volume of 15 ml (Note a). Add 3 mg Ce™ and 2 granules of NaZCr207 . Sti.r well and heat for 5 min on a 75°C water bath. Cool in tap water until sample reaches room temperature. Precipitate CeF4 by adding 10 drops HF treated with dichromate (Note b), Stir well and centrifuge immediately. Wash the precipitate with 2 ml 1 N HT_\TO3 1 N HF. Decant the supernate and wash into a clean 50-ml lusteroid tube. Make the solution basic with 8 N NaOH. Let stand 3 min and centri- fuge. Wash the Fe(OH)3 with 10 ml water. Discard the supernate and wash. Dissolve the hydroxide in 3 drops of I-_INO3. Add 5 mg La, 1 mg of Zr and dilute to 10 ml with water. Heat the solution for 3 min on a 75°C water bath. Add 20 mg NaHSO3 a little at a time, to insure complete reduction, Continue to heat for 5 min. Add 10 drope HF with stirring, and heat for a few minutes. Cool and centrifuge. Wash the LaF3 with 2 ml 1N HCl1 -1 N HF. Digcard the supernate and wash, Slurry the LaF3 in 1 ml saturated H3BO3 and heat on a 75°C water bath for a few minutes. Add 1 ml HCl and 1 ml water and continue to heat on the water bath to obtain a clear solution, Transfer the solution to a 40-ml glass tube with water washes, Add NI-I4OH to precipitate La(OH)s. Digest in a hot water bath for a few minutes. Centrifuge, and wash the precipitate with 5 ml water containing 1 drop NH4OH. Discard the supernate and wash. Dissolve the L.EL(OH)3 in 1 ml HC1 and 2 drops HNO,. Heat the solution for 3 min in a hot water bath, Cool the solution in an ice bath, and saturate with HCl gas. Allow io come to room temperature. Transfer the solution to a prepared Dowex AG 1-X8 (100-200 mesh) colurnn, Prepare a wash solution containing 15 ml HCI and 1/2-ml 124 11, 12, 13. 14, 15. 16. 17, 18. 19, 20, 21. Notes a. HNO3 . Rinse the tube with several 1-ml portions. of this sclution. Transfer these washes to the column. Wash the column with the remaining solution in 2-ml portions. Wash with 15 ml HCI in 2-ml portions. Discard the effluents and washes. Prepare an eluting solution containing 20 ml HCl and 75 mg NH 41. Elute the Pu from the column into a 50-ml beaker with 2-ml portions -of thig solution, allowing the first 2-ml portion to pass through. Add the second 2-ml portion and plug the top of the column with -a piece of pressure-sensitive tape for 5 min. Remove the tape and continue to elute in 2-ml portions. Pass through 6 ml of HC1 in 2-ml portions. Add 2 mg of La and evaporate the solution to approximately 5 ml. Transfer to a 50-ml lusteroid tube and dilute to a volume of 10 ml. Add 20 mg NaHSO3 a little at a time. Add 10 drops HF with stirring, and allow to stand for a few minutes. Cool in an ice bath, centrifuge, and wash the LaF, with 2 ml 1 N HCIl X 1N HF. Discard the supernate and wash, ? Repeat Steps 7 through 11. Evaporate the solution in the 50-ml beaker to approximately 5 mls with addition of HI\‘IO3 to drive off all iodine. Transfer the solution to a 40 ml centrifuge tube. Add 5 mg Fe' " and precipitate Fe(CH), by addition of NH,OH. Digest in a hot water bath for a few minutes. Céntrifuge, and wash thé precipitate with 5 ml water containing 1 drop NH4OH. Digcard the supernate, Disgolve the Fe(OI’-I,'v3 iIn5ml6éN HNO3 . Add 4 drops saturated NaBrO solution. Warm on a hot water bath for a few minutes. Saturate the solution with NH,NO,, crystals, add 5 ml hexone (methyl isobutyl 4 73 ketone) and stir with a mechanical stirrer for 3 min, Centrifuge to 3 separate the phases, and withdraw the hexone (upper) layer with a transfer pipet. Transfer the hexone to a clean, dry 40-ml centrifuge tube.. Repeat the extraction twice, adding 1 drop of saturated N:;.BrO3 and more N'H4N03 if necessary. 241 Record the time of extraction as the '"Final Separation of Pu and Am241." Wash the hexone phases by stirring with 5 ml 6 N HNO3 . Stir for 2 min, centrifuge, withdraw the acid (lower) phase and combine with original aqueous phase, Back-extract the Pu from the hexone by stirring for 3 min with 5 ml 0.1N HN03. Centrifuge, and transfer the aqueous phase into a 50-ml beaker. Repeat twice and combine the agueous phases, The solution is now ready for electroplating. Do not continue step 3 unless there is enough time to carry the procedure completely and rapidly through step 5. b. Dissolve 1 granule of Na,CR,Oy with 1/2 ml HF in a Pt dish. 125 Procedure 8, Uranium and Plutonium Analysis B. F. Rider, et al., (Ref, 332) QOutline of Method Sample of dissolved irradiated fuel contain highly radioactive fission products., For this reason, U and Pu are geparated before analysis. The procedure described here gives a good yield, together with a good decontamination factor. Reagents 1. Distilled conc. H'NO3 - 2, 2M HI\TO3 - distilled conec, HNO3 , double distilled H,O. 3. U233 solution, standardized, 4, Pu.236 Solution, standardized, 5. KBrO3 - crystals, reagent grade. Low natural U blank, 6. 8M NH4NO3 in2 M HNO3 - Place 200 ml distilled 16 M HNO3 + 100 ml double distilled Hzo in a large beaker. Bubble l\iI'I-I3 gas through solution until basic to pH paper. Boil off excess NH3 (solution neutral). Transfer to mixing cylinder, add 50 ml of distilled 16 M HNO3 , dilute t0.400 ml, Check density of solution (1.31 £ 0.01 @20°C). . Hexone - distilled. HCl - C.P. reagent. Low natural U blank, . I M HNO3 - distilled conc. HN03 , double distilled HZO' 10. 30% H202 - meetg A. C. S, specification, low natural U blank, 11, 0.2 M TTA in xylene - 4,44 gm TTA dissolved in 100 ml digtilled xylene, 12, Xylene - distilled. 13, Ether - distilled, 14, 0.05 M HNO:3 - distilled conc. HNO3 , double distilled HZO' 15. HZO - double distilled. Glassware All glassware used is Pyrex which has been soaked overnight in 50% HNO:3 and rinsed with double distilled water. Pipets are rinsed with 50% HNO3 and double distilled water before being used. Separation and Decontamination Procedure 1. Place the aliquot for analysis in a 15-ml cone and evaporate to about 1 ml., Add a suitable U233 and P1.1236 spike, one drop conc, nitric acid, and several KBTOBH_ crystals. Allow to stand for 1 hr to allow oxidation of Pu to Pqu. Add 1.5 ml 8 MNH4NO:'3 in 2 MHNOS, Prepare two scrub solutions in separate 15-ml cones, containing 1 ml of 8 M NH4NO3 in 2 M HNO, and about 10 mg KBrO;. Preoxidize about 10 ml Hexone with 2 ml of 2 M HNO3 and KBrO until ready for use. and evaporate to about 2 ml, Keep covered 3- 126 10. 11. 12, 13. 14, Extract the U and Pu four times for 5 min with 2-ml portions of hexone (methyl isobutyl ketone), adding 1 drop of 16 M HNO, to the original solution after each extraction. Scrub each extract in turn with the two solutions prepared in step 3. Strip the combined hexone extracts with five 2-ml portions of HZO‘ Evaporate the combined aqueous portions to dryness, add a few drops of H'NO3 and HCI1, take to dryness. Evaporate to dryness with HNO3 under a gental stream of pure nitrogen on a boiling water bath. Prepare 3 ml of 1 MHNO3 and 1 drop of 30% H202, add 1 ml to the Pu and U residue from step 5 and two 1-ml portions to separate 15 ml cones. Extract immediately the Pu two times for 20 min with 2-ml portions of 0.2 M TTA (thenoyltrifluoroacetone} in xylene. Scrub each in turn with solutions prepared in gtep 6. Save the aqueous phase for U. Combine the TTA extracts and add a few crystals of trichloroacetic acid. Mount the combined TTA extracts on a Pt plate for o-pulse analysis. After pulse analysis, remove the Pu for mass analysis as follows: Cover disk with HF'. Evaporate to dryness under a heat lamp. Again cover disk with HF and evaporate to dryness. Cover disc with cone. HNO3 and evaporate to dryness. Repeat three or four times. Cover disk with conec, nitric, reflux a few seconds, and transfer with a pipette to a 15-ml cone. Repeat three or four times, Evaporate the combined conc. HNO3 refluxes to dryness. Treat residue with aqua regia and evaporate to dryness. Evaporate to dryness with cone. HNO3 on a bolling water bath several times. Add 50X of 0.01 M HNO3 to the evaporated sarmple and submit sample for mass spectrographic analysis. Wash the original 1 M HNO3 U fraction (step 7} with xylene. -Add 1 drop of HNO3 and 3 drops of HCI to the washed 1 M HNO3 and reflux for about 1/2 hour to destroy the organic present., Evaporate to dryness, flame gently to destroy organic matter and dissolve the residue with 2 drops of HNO3 and evaporate to dryness on a water bhath, Pipette three 1-ml portions of 8 M NH4N03 in2 M HNO3 . dissolve the evaporated U fraction in one 1-ml portion. Place the other 2 portions in two 13-ml cones for scrub solutions, Extract the U with four 2-ml portions of diethyl ether, adding 100 A of conc. HNO3 before each extraction. Scrub each extract in turn with two scrub solutions prepared in step 12. Evaporate the combined ether extracts over 1 ml of HZO in a 15-ml cone. Ewvaporate to dryness. 127 15. Add 3 drops of HC1 and 1 drop of HNO:3 , and evaporate to dryness repeatedly until the organic is destroyed. Flame gently to expel ammonium salts. Then dissolve in H'NO3 and evaporate to dryness - on a water bath, Add 50X of 0.05 M HNO3 to the dry cone and submit sample for mass spectrographic analysis. Plutonjium Calculation To determine the amount of Pu in the original sample, it is necessary to measure in a Frisch chamber the ¢ spectrum of the plate prepared in step 8. The 239 and Pu240 activity to Pu236 activity is calculated. If the ratio is 236 239 ratio of. Pu multiplied by the original activity of Pu Pu240 obtained. The specific activity of the mixture is calculated from that of the individual 239 plus Pu240 activity can be converted to Pu239 plus Pu2.40 added, the original activity of Pu can be obtained. From the mass analysis a Pu239 to Pu240 atom ratio is plus isotopes. The Pu weight by dividing this activity by the specific activity of the mixture. Uranium Calculation The ratio of the various U isotopes to U233 from the mass spectrometer data is rnultiplied by the amount of U233 spike originally added to the sample to obtain the amount of each U isotope present in the original sample. 128 Procedure 9a. Separation of Plutonium from Irradiated Uranium R. O. Lingjaerde (Ref. 255) Outline of Method The Pu, U and figsion products are adsorbed on a cation exchange column from 0.3-0.5 M HNO3 and washed with 0.5 M HNOS. The U and fission products are then eluted with 2.0 M HC], and the Pu is stripped with 8 M HCl. The Pu is then adsorbed onto anion exchange resin, washed with 8 M HCl, and finally stripped with 2 M HCI. Procedure 5 ml of stock solution {containing about 15 ug Pu), 5 ml of 4.0 M HNO, and Smlof 1.0 M NaNO2 were mixed in a flask, and made up to a volume of 50 ml with water, NOZ‘ reduces Pu(VI) to Pu(IV), Care has to be taken that concentration of HNO3 is not allowed to fall below 0.1 M, since Pu then will hydrolyse and conse- quently coagulate on the column. This solution was adsorbed on Dowex 50 (140-160 mesh) and the column was washed with 0.5 M HN03. ing fission products. The washing with 2.0 M HCl wasg continued until the S8-activity Then 2.0 M HCl was applied to elute U and accompany- was close to background. Pu and remaining fission products were eluted with 8 M HCI, a small 3 + some NaNOZ added (to oxidize Pu(Ill) to Pu{IV)), and this fraction was transferred to another column containing Dowex 1 (50-100 mesh), amount of concentrated HNO which beforehand had been washed with concentrated HC1 containing a little concentrated HNO3. After the sorption step, the column was washed with 8 M HCI (containing a little concentrated HN03) until the effluent was practically free from B-activity. T"inally the Pu was eluted with 2.8 M HCI. 129 Procedure 9b, Separation of Plutonium from Uranium Metal, J. Rydberg (Ref. 341) Qutline of Method This procedure makes use of the co-precipitation properties of the different oxidation states of Pu on BiPO4. The Pu is first oxidized to Pu({VI) which does not carry on BiP04, and then reduced to Pu(IV) which carries, An additicnal purification step is provided by extraction into TTA. Yield is greater than 60%. Procedure 1. The U sample is dissolved in hot conc, HNO3 and kept at 90°C for 30 min, giving a solution of U(VI) and Pu(IV). The solution is diluted to 5 M in HNO, and solid NaBiO3 is added to oxidize Pu to the +6 valency state. The solution is made 0.1 M in HNO, (if it becomes turbid, HNO, is added until the solution is clear) and 0.1 M in phosphate. The BiPO4 precipitate is centrifuged off. This precipitate carries most of the 3 fission products, and especially those with a chemistry similar to Pu(IV). The supernatant solution containing Pu(VI) ig made 1 M in HNO3 , 0.05 M in NoH, and 0.005 M in Fe''. In this solution Pu is rapidly reduced to Pu(III). The solution is diluted to 0.1 M in HNO, and made 0.1 M in phosphate. Bi™1 is then added (1 drop 0.1 M Bi' ' for each ml solution) to precipitate BiPO4 , which carries all the Pu, The precipitate, which ig usually contaminated with some U is centrifuged off and washed, The phosphates in the precipitate are converted into hydroxides by treating with warm ~10 M KOH. After centrifuging the solution is drawn off, and the precipitate is washed and dissolved in hot conc. HNOa. . After some hours at room temperature, the solution is diluted to 1 M HNOS, acetone in benzene. This gives a pure Pu(IV) solution in the benzene and extracted with an equal volume of 0.3 M thenoyltrifluoro- phase, leaving the rest of the U and the fission products in the aqueous phase. . If desired, the Pu(IV) can be back-extracted in to the aqueous phase with 10 M HNO, or HCI0 phase with benzene. 4 after a two-fold dilution of the organic 130 Procedure 10, Purification of Plutonium from Uranium and Fission Products J. Rydberg (Ref, 341) Oufline of Method The method takes advantage of the fact that Zr and Nb are adsorbed very well on silica gel from strong nitric acid solutions. Further decontamination from fission products is achieved by precipitation of CuS from a 0.5 M HNO:3 solution. Pu(IV) does not carry. Finally the Pu{lV) is extracted into TTA. Yield is greater than 90%. Purification is approximately 106 from B—y radiation of fission products. Procedure 1. 2. The U03 sample is dissolved in hot conc. HNO3 and kept at 20°C for 30 min, giving a solution of U(VI) and Pu(IV), The acidity of the cooled solution is adjustied to 6 M in HNO3 , and the . solution is run through two columns of SiO2 gel. This removes most of the Zr and Nb. The columns have a dimeter of 0.8 ¢cm and a length of 10 cm. Cu-H-, La*tt and ZrO-H- (1 drop 0.1 M carrier for each ml of solution) are added to the solution, and it is then diluted to 0.5 M in HN03. On the addition of HZS‘ CuS precipitates and carr’ies most of the fission products with sulfides insoluble in 0.5 M HNOS. The precipitate i's centrifuged off, The solution is evaporated almost to dryness and then kept for 30 min in hot ~10 M HNO valency state. The solution is diluted to 1 M in HNO3 volume of 0.3 M thenoyltrifluoroacetone in benzene. Under these 3" This removes H28 and restores the Pu(IV) and extracted with an equal conditions practically only Pu(IV) and Zr(IV) are extracted, leaving U, Th(UXl) and the rest of the fission products in the aqueous phase. After a two-fold dilution of the organic phase with benzene, Pu(IV) can be extracted back into an aqueous phase with 10 M HNO3 or HClO4 . This provides an additional purification from Zr. In practice it has not proved necessary to use this step, Procedure 11. Uranium and Plutonium from Environmental Samples of Soil, Vegetation and Water E, L. Geiger (Ref. 144) Outline of Method . The samples are pre-ireated to bring the Pu into solution as Pu(IV) in Al(N03)3 - HNOS. The U and Pu ia then extracted together into 50% TBPF in tetradecane, washed with 4 N HNO3, and back-extracted into water for mounting and counting as total U and Pu, Yield is approximately 80 £ 15 (S, D. of mean)%. Procedure Preparation of samples Vegetation. Cut oven-dried vegetation into small pieces and weigh 10.0 g into a 150-ml beaker. Heat the sample at 600°C, starting with a cold muffle furnace. When only white ash remains, remove the beaker from the muffle furnace and allow to cool. Carefully add 2 ml of water, then add 10 ml of 8 l\T_HNOB—O.5 MAI(NOa)3 tion, Cover the beaker with a watch glass and boil the solution for 5 min. Allow to cool, add 1 ml of 2 M KNO2 tube. Use 4 N HNO3 to complete the transfer. Centrifuge and decant the supernate solu- solution and transfer the sample to a 100-ml centirifuge into a 125-ml cylindrical separatory funnel graduated at 30 ml. Wash the residue with 4 N HNOS, centrifuge, and decant the wash solution to the separatory funnel. The acid normality of the combined solutions at thig point ig 4-6 N and the total volume should not exceed 29 ml. Proceed to the extraction procedure. Soil. Grind 5 g of oven-dried soil with a mortar and pestle until the entire sample can pass through a 200-mesh sieve. Weigh 1.0 g of the 200-mesh soil into a 50-ml Pt crucible and heat the sample at 800°C for 4 hr. Remove the sample from the muffle furnace and allow to cool. Add 3 ml of 70% HNO3 and 10 ml of 48% HF, then stir the sample for 2-3 min with a Pt rod, Heat the sample in a 200°C sand bath until all traces of moisturs are removed. Repeat this HNO,_-HF treatment, being careful that the sample is completely dry before proceeding to tl?;e next step. Allow the sample to cool and then add 15 ml of 6 N HN03-0.25 M AI(NO3)3 solution, Cover with a watch glass and heat in the sand bath for 5 min. Allow to cool and decant the solution through a filter, such as Whatman No, 40, into a 125-ml cylindrical separatory funnel graduated at 30 ml, Leave as much of the residue as possible in the crucible and repeat the hot 6§ N I-I'N03—0.25 M AI(NO3)3 treatment. Allow to cool and then filter, Proceed to the extraction procedure. Water. Place 1 liter of the sample in a 1.5-liter beaker and if basic, neutralize with nitric acid. Add 15 ml of 70% HNO3 and evaporate to 30-40 ml. Decant the solution through a filter, such as Whatman No, 40, into a 100-ml beaker. ~ Wash the 1.5- liter beaker, the residue and the filter with 4 N HNO,. Evaporate the combined solution in the 100-ml beaker to 5 ml. Add 20 ml of 4 N HNO,, cover with a watch glass, and heat for 5 min. Transfer the sample to a 125-ml cylindrical separatory funnel graduated at 30 ml. Wash the beaker with 4 N HN03 to the separatory funnel, being careful that the total volume in the separatory funnel and transfer does not exceed 29 ml. Proceed to the extraction procedure. 132 Extraction. Add 1 mlof 2 M KNO, to the sample in the 125-ml cylindrical separatory funnel. Dilute to the 30-ml mark with 4 N HNO, and stir the solution briefly. Add 30 ml of 50% TBP in n-tetradecane. Agitate the solution vigorously for 4 min with an air-driven stirrer. Discard the acid portion (lower layer). Wash the TBP portion with 4 N HN03 and again discard the acid portion. Back extract with seven 15-ml portions of distilled water, collecting the sirip solution in a 150-ml beaker., Evaporate the combined aqueous portions to 10-15 ml, then quantitatively transfer the solution to a flamed stainleas steel planchet. Allow to dry under a heat lamp, flame the planchet to burn off organic residue, and count on an ¢-counter. Retain for pulse-height analysis if the e¢-count exceeds a specified level, 133 Procedure 12. Plutonium from Environmental Water Samples J. Scheidhauer, L. Messanguiral, and A. M. Meiraneisio {(Ref. 352) Outline of Method Pu(IV) is spearated by chemisorption on solid Can as the concentration step, and further purified with two TTA extraction cycles. The chemisorption step has been shown to be quantitative and very efficient. The sensitivity can be made very -11 great, as low as 0.7 X 10 Ci/ml by taking a large sample. Reagents Concentrated nitric acid (d = 1.38) 10 N nitric acid 2 N nitric acid 1 N nitric acid Concentrated hydrofluoric acid Concentrated perchloric acid Ferric nitrate Hydroxylamine hydrochloride 1 M hydroxylamine hydrochloride Sodium nitrite Ammonium thiocyanate 2M Al(NO3):3 -05N HNO3 Calcium fluoride Solution of 111 g/1 TTA in xylene Procedure 1. Place 3 liters of filtered water to be analyzed in a beaker and add 5 g each of ferric nitrate and hydroxylamine hydrochloride. 2. Heat and agitate with a glass stirring rod to about 60-70°C. T+ is reduced by spot Let the sclution cool down, making sure the Fe testing with several crystals of ammonium thiocyanate from time to time. 4. Pour this solution in a plexiglass column which is closed at one end and edd water to within 0.5 cm of the top. Start agitation with a magnetic stirrer. 5. Add 10 g sodium nitrite. After several minutes add 60 ml concentrated HNO3 (d =1.38), then 45 ml concentrated HF when the HNO3 has redis- solved the ferric hydroxide which has formed. 6. Then add 0.2 g calcium fuloride powder and place the filtration system on the column (see Fig.58). 7. After agitating for 1 hr, invert the column over a 5-10 liter plastic receiving vessel. The filtration may be speeded by maintaining pressure by means of a laboratory pump. 8. Wash the filter cake two times with 250 ml of distilled water introduced into the tube under pressure. 134 k L Fig. 58. Cross sectional view of the agitation column. The material is "Altuglas MZD" throughout except for the brass screws. The diffuser plate has a total of 213 holes drilled on 8 concentric circles. The inside dimensions of the column are 8.0 c¢m diameter by 60 cm high. The reader is referred to the original paper for a more de- tailed drawing. 135 10. 11. 12. 13. 14, 15. 186. 17. 18. 19. 20. 21. 22. 23. 24, 25. 28. ~the organic phase two times with 3 ml 10 N HNO After disassembly of the filtration apparatus the filter membrane is placed in a 100-ml beaker. The apparatus is washed briefly with distilled water which is poured into the beaker. Add 4 ml of the 1"—\1(N03):3 - HNO:3 volume is reduced to approximately 20 ml, remove the filter and wash it solution and bring to a boil. When the with water. Continue to evaporate to about 15 ml. Add 4 ml 1 M hydroxylamine hydrochloride and let cool. Make sure the Fe+++ is completely reduced by spot testing (with ammonium thiocyanate). Add 0.5 sodium nitrite and start agitation. Add 1.5 ml 10 N HNO3 make sure by spot testing that the ferrous ion is oxidized. Expel the and nitrous vapors. Add 15 ml TTA-xylene solution. Agitate so that the two phases are well mixed for 1/2 hr. Perrmit the phases to separate and draw off the aqueous phase with a pipette. Wash two times with 5 ml I N HNOB. Back-extract the Pu(IV) by agitation with 5 ml 10 N HNO,, for 1/2 hr. Wash 3 3 The 10 N HNO,, phases are combined in a 30-ml beaker and evaporated to dryness. 3 Take up with 2 ml fuming HNO3 and 3 ml HClO4 and evaporate to dryness. Stop heating and add 1 ml 1 M hydroxylamine hydrochloride when the tem- perature permits, Let the solution cool and verify that Fe'*" ig reduced by spot testing using a very thin glass rod. Add 1 mi 1N HNO3 and transfer to a 30-ml separatory funnel, washing the beaker two times with 1 ml of 1 N HN03. Add 0.15 g NaNO, to the funnel. Wash the beaker again with 1 ml 2 N HNO and 0.5 ml 2 N HNOS. Combine these washes in the funnel. Stir slowly for 5 min to expel the nitrous vapors. 3 Add 5 ml TTA-xylene and stir for 20 min at maximum speed. Let the phases separate and eliminate the aqueous phase. Wash two times by agitation for 10 min with 3 ml of 1 N HNO3. The Pu is next re-extracted by agitation for 20 min with 5 ml of 10 N HNO and the organic phase is washed two times with 2 ml of 10 N HNOa. 3! The combined aqueous phase is evaporated on a watch glass and counted. 136 Procedure 13. Plutonium from Environmental Water Samples J. Kooi and U. Hollstein (Ref. 237). QOutline of Method B:i_PO4 is used to concentrate the Pu after reduction to Pu(IV) with SO2 9 The Pu is further purified by co-extraction into ferric cupferride as Pu(III) from dilute gas. The solution is heated to 100°C for several minutes to expel excess SO nitric acid, Finally, the organic matter is destroyed by wet-ashing with stO4 and HNO3 and the Fe'' ¥ precipitated as the hydroxide, mounted and counted. 6 Yield. Approximately 99% from solutions containing 0.8 X 10" ° g CiPu/ml. Procedure 1. Acidify a 500 ml sample of water with 15 ml of 2 N nitric acid and add 10.4 mg of Bi°T, 2. Bubble 502 gas, technical, gently through the solution for 20 min, using a wide capillary. 3. Heat the solution to boiling and keep it boiling at 100°C for some minutes 9- Add slowly 60 ml of a 1 M solution of orthophosphoric acid under continuous stirring with a glass rod and leave to expel the excess of the SO the suspension at 90°C for 30 min with occasional stirring. Allow the precipitate to settle for at least 2 hr, by preference overnight. 4, Filter through a fine-fritied funnel, the stem of which has been drawn into a wide capillary. Use 25 ml of 8 N HCL in total to rinse the beaker and the glass rod ahd to dissolve the precipitate on the funnel. Suck the solution through the funnel directly into a 50-ml narrow-necked flask placed in a filtering flask with cut-off bottom, resting on a ground-glass plate. 5. Transfer the Bi-Pu solution to a 250-ml beaker, rinse the flasic with a little distilled water and add 5 ml of freshly prepared 10% hydroxylamine hydrochloride solution. After 15 min make up to about 100 ml with distilled water. _ 6. Using a pH meter, adjust the pH to 0.7-0.8 by addition of 70-90 ml of 2 N ammonia. Add 0.1 mg of Fet 7. Transfer the solution into a 1~-1 separatory funnel, lubricating the stopcock with any kind of grease that can be completely removed by the oxidation as described in 14-16. Add 2 ml of a freshly prepared 5% cupferron solution in water, shake, and let stand for 45 min. 8. Add 30 ml of purified chloroform. Shake the mixture repeatedly for 1 min and run the chloroform extract through a 4-5 ¢m No. 41 Whatman filter paper into a 250-ml separatory funnel, using the same kind of grease for the stopcock. 9. Shake the chloroform solution with 20 ml of 0.3 N hydrochloric acid con- taining 1.5 g of cupferron per liter, and run the chloroform layer through a No. 41 Whatman filter paper into a 250-ml roundbottom flask with ground joint. Transfer the water layer of the lower separatory funnel into the upper one, 137 10. 11. 12. 13. 14. 15. 186. 17. 18, 19, 20. 21. Add to the solution in the upper funnel 0.1 mg Fe™ and 2 ml of a 5% cupferron solution, shake, and let stand for 45 min. Repeat the whole extraction procedure twice (8 and 9) with 25 ml of purified chloroform. Transier the water-layer resulting from the first repetition from the lower to the upper funnel. Discard both water-layers in upper and lower funnel after the second repetition, Wash down the sides of the two filter papers into the roundbottom flask with as little chloroform as possgible io remove traces of red-brown iron-cupferrate, Distill off the chloroform until about 20 ml is left and remove the remainder of chloroform by gentle blowing or suction, as shown in F1g 59. Add 1 ml of concentrated sulfuric acid (C. P. grade) and attach to the round- bottom flast a 15-c¢m condenser. Reflux for 30 min. Add 2 ml of fuming nitric acid (C. P. grade) and heat until the solution appears light yellow. Remove nitrous vapors and sulfur trioxide first by heating, later by sucking air through an attachable tube, creating slight turbulence in the bulb and the neck of the roundbottom flask. Two burners should be used, one to keep the bulb hot, without heating the dry residue to a red glow, however; and the other to prevent condensation in the neck of the round- bottom. If the dry residue does not appear snow-white after cooling, repeat 14 and remove sulfur trioxide by heating as above, Dissolve the white residue in 1 ml of concentrated HCL while gently heating. Some time may be needed before the solid is completely dis- solved, | The final sample for counting is deposited on a Pt tray of 35 mm diameter and 1 /8 cm thick. Determine the counter background with the tray in counting position. Place the tray under a radiant heater and, using a drawn-off pipette, transfer the green-yellow solution onto the tray, covering about half of the area. Rinse the flask with a second ml of con- centrated HCL and {ransfer the washing onto the tray. Repeat with 1 ml of water. After evaporation to near dryness, add a few drops of water, Enclose the tray and two 10-ml beakers filled with 10-15% ammonia in a large beaker upside down. I.et stand for at least 5 min to ensure the formation of ].-'-‘e(OH):3 to be completed., Evaporate to dryness. Place the tray in a porcelain dish, cover it with a second dish, and ignite for 10-15 min to convert the hydroxides to oxides. Count the sample under an @-counter. A simple counting device consisting of a photomultiplier and a ZnS screen, provided with a light trap for insert- ing samples without switching off the high voltage, showed to be very re- liable and satisfactory. Efficiencies up to 47-50 percent may easily be ob- tained. Calculate the Pu concentration according to the formula S - -S A Cp, = 9.01 X 107" & pe/ml P where A = activity of sample in counts per minute and E = percentage efficiency of counter. 138 ~ ~ \\ Y * ) ,I (a) (b) Fig. 59. Roundbottom flask used for destruction of organic matter. (a) Set-up used for refluxing (----) and removal (—) of nitric acid. (b) Set-up used for removing chloroform and sulfur-trioxide vapors. 139 Procedure 14. Separation of Plutonium in Uranium-Plutonium Fission Element Alloys by TBP Extraction from Chloride Solutions R. P. Larsen and C. A. Seils, Jr. (Ref. 249) Qutline of Method The U and Pu are reduced to U(IV) and Pu(Ill) by contact with Mg turnings in 2 2 M HCI solution. The U is then extracted into TBP. The Pu is then oxidized to Pu(IV) with NaNO3 and exiracted into TBP and back-extracted with 0.1 M HCl. The Pu is then precipitated as the hydroxide and taken up in HNO:3 for spectrophotometric determination. Reagents Unless otherwise stated, reagent grade materials are used. 1. Tributyl phosphate, 30-volume % in carbon tetrachloride. 2. Tributyl phosphate, 30 volume % in Amsco-140 {a kerosine distillate). 3. Dilute 300 ml of tributyl phosphate (Commercial Solvents Corp.) to 1 liter with carbon tetrachloride (or Amsco-140). Scrub once with 200 ml of 0.5 N sodium hydroxide to remove traces of mono- and dibutyl phos- phate. Scrub four times with distilled water and filer through a large dry filter paper to remove cloudiness. Procedure Dissolve the alloy sample, using the procedure described by Larsen® for this type of material, and dilute to volume. Pipette an aliquot containing 10 to 20 mg of Pu into a 50-ml Erlenmeyer flask. For 20% Pu alloys, there will be 35 to 70 mg of U, more than enough for its determination. Convert to a chloride medium by evaporation to near dryness (3X) with 12M hydrochloric acid. Adjust the volume to 10 ml and the hydrochloric acid concentration to about 2M. Add approximately 0.1 g of Mg turnings over a period of several minutes. Using a double layer of glass fiber filter paper in a filter chimney assembly, separate the precipitated Group VIII elements by filtration, and catch the filtrate in a 60-ml cylindrical separatory funnel. Rinse the flask and filtering assem- bly with three 5-ml portions of 12M hydrochloric acid. Add 15 ml of 30% tributyl phos- phate in carbon tetrachloride and shake for 1 min. Allow the phases to separate and transfer the U-béaring organic phase to a second 80-ml separatory funnel. Repeat the extraction with 10 ml of 30% tributyl phosphate in carbon tetrachloride and combine the U-bearing organic phases in the second separatory funnel. Treat the Pu—beafing aqueous phase by the procedure outlined in the next paragraph. Add 15 ml of 0.5M hydrochloric acid to the combined organic extracts and shake for 1 min. Allow the phases to separate and drain the stripped organic phase into a 60-ml separatory funnel. Add 10 ml of 0.2M hydrochloric acid and repeat the stripping operation. Discard the organic phase and combine the aqueous strip solutions in the second separatory funnel, Add 5 ml of carbon tetrachloride and shake 30 sec to wash out dissolved tributyl phosphate from the aqueous phase, Discard the organic layer. Rinse the U solution into *Larsen, R. P., Anal. Chem. 31, 545 (1859). 140 a 50-ml Erlenmeyef flask and evaporate to dryness (2X) on a sand bath after addition of 2-ml portions of 16M nitric acid. Add 5.0 ml of 16M nitric acid to dissolve the U. Transfer to a 50-ml volumetric flask with water and make up to volume. Determine U x-ray spectrometrically. For samples containing less U, use proportionately smaller volumes of nitric acid and volumetric flasks (down to 5 ml). Add approximately 100 mg of sodium nitrite to the agueous raffinate from the U separation to oxidize the Pu to the quadrivalent state. Add 20 ml of tributyl phosphate-Amsco-140 and equilibrate 1 min. {(Amsco-140 is used as the inert diluent to give a light organic phase.) Discard the lower aqueous raffinate., Add 15 ml of 0.2M hydrochloric acid and equilibrate 1 min. Allow the phases to separate and irans- fer the aqueous phase to a 50-ml Erlenmeyer flask. Add 10 ml of 0.2M HCL to the organic phase and repeat the stripping operation. Combine the aqueous strip solutions, add 2 ml of 12M hydrochloric acid, and evaporate on a sand bath to reduce the volume to approximately 2 ml. Transfer the solution to a 15-ml glass centrifuge cone with a transfer pipette and dilute to 7ml with water. Add 0.5 ml of 20% hydroxylamine hydro- chloride and let stand 15 min with occasional mixing. While mixing with a Pt stirring wire, add 10M sodium hydroxide dropwise until plutonium hydroxide precipitates. Add 10 drops of sodium hydroxide solution in excess and let stand for 5 min. (Evaporation is not a satisfactory volume-reduction step, as it does noi remove chloride. With the nitrate introduced in the next step, oxidation of the Pu to the sexivalent state would occur.) Centrifuge for 5 min and discard the clear supernate, Wash the precipitate with water, centrifuge for 3 min, and discard the wash solution. Add 2.0 ml of 16M nitric acid and stir to dissolve the precipitate. Heat the nitric acid solution in a boiling water bath for 20 min. (This treatment will destroy any polymeric Pu which may be present and ensure complete oxidation of the Pu io the quadrivalent state, If the precipitate were digsolved in hot 3M nitric acid, some oxidation to the sexivalent state would occur.) Allow the solution to cool and dilute to volume in a 10-ml volu- metric flask with water. HRead the absorbance vs a reagent blank in 1-cm cells at 475 mu and a slit width of 0.02 mm. Calculate the Pu present from a calibration factor prepared from a series of standards carried through the hydroxide precipitation step only. 141 Procedure 15. Separation of Pu before Spectrographic Analysis of Impurities Anion Exchange Method F. Trowell (Ref. 405) Qutline of Method Pu metal is dissolved in HCIl and an excess of 8 M HNO, ig added. Pu ig adsorbed on an anion exchange column from the resulting mixture and the column is washed with 8 M HNO3. The solution and wash is evaporated to dryness, taken up in 6 M HCI, and spectrographically analyzed for Al, Be, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Ti, and U. Reagents 1. 8 M HNO, (Note a). 2. 6 M HCI (Note b). 3. Resin (Note c). Procedure 1. Weigh duplicate portions of 0.25 g of Pu metal and dissolve each by tipping into 1 ml 6 M HCI in 50-ml silica beakers. . 2. When all traces of metal have dissolved, add 5 ml 8 M HNO3 and mix well. Note (d). 3. Transfer the resulting green solutions to the ion exchange columns (Note (e)) using the minimum volume of 8 M HNO, to rinse out the beakers. 4. Place 50 ml silica beakers containing 1 ml of 100 yg/ml Sc solution under the columns to collect the eluted solutions. Allow the Pu solutions to drain down to the top of the resin. 5. Add 15 ml 8 M HNO through. 3 to the columns and allow this eluting acid to drain 6. Transfer the silica beakers to the fume cupboard and evaporate the solu- "~ tions to dryness. Note (f), 7. Add 1 ml 6 M HCI to the dry residues and warm slightly to ensure com- plete solution; draw into polythene ampules. Note (g) 8. Prepére duplicate reagent blanks using the procedure and reagents above but omitting the Pu, 9. Pass 0.3 M HNO, through the columns until all traces of green color have been removed (Note (h)). Recondition the column for further use with 8 M HNOa. Note (i). Notes {2) Prepared from concentrated HNO3 (redistilled from silica) and deionised water. (b) Prepared from gaseous HCI1 and deionised water. (c) Deacidite FF (SRA 68). Remove fines by stirring with water. Allow to settle for 10 min and decant off any resin still in sugpension; repeat this 142 procedure until all fines are removed. Use 3 ml wet resin in a 6-mm bore gilica column fitted with a quartz wool plug. (See Fig. 60). for dimensions. } _ ' (d) At this stage the color changes from blue to green. (e) Condition the columns immediately before use by allowing 10 ml 8 M HNO3 to run through them. (f) This solution contains the impurities free from Pu. (g) This solution is ready for analysis by the polythene funnel method. (h) Collect the washings and transfer to the appropriate residue bottle. (i) Add about 10 ml 8 M HNO3 perspex rod until it is in suspension and all air bubbles have been and stir the resin with a pointed 1/8-in. removed. Allow to settle for 10 min and decant off any resin still in suspension. Add fresh resin to bring the total resin volume to 3 ml. - I.5¢cm BORE 4cm 4cm BORE Bem 20 em 6émm BORE QUARTZ WQOL PLUG Fig. 60. Ion exchange column. 143 Procedure 16. Separation of Plutonium Before Spectrographic Analysis of Impurities. Extraction Chromatography Method Using TBP ¥. Trowell (Ref. 405) QOutline of Method Pu in 8 M HNO, solution is adsorbed on a KelF/ TBP chromatographic c¢olurnn and the impurities eluted with 8 M HNO3. Sc is added as an internal standard to the eluted scolution which is then concentrated by evaporation and analyzed by the graphite spark technique for Al, Co, Cr, Fe, Ga, Mn, Ni, and Ti. Applicability. This method is intended for the analysis of high-purity Pu. The concentration range covered is from 0.5 to 10 ppm. The lower limit of analysis may be restricted by the reagent blank. Equipment 1. Column (for dimensions and preparation see Appendix). Reagents . 6 M HCl. Note (a). 2. 16 M HNO,. Note (b). 8 M HNO,. 0,32 M HNO,. 2 M HF. Note (c). CC14. Note {d). Tri-n-butyl phosphate. Note (e). KelF. Note (f). Grease solution. Note (g). = 3 s W Procedure 1. Weigh 2 g of Pu and dissolve by tipping into 5 ml 6 M HCl in a 50-ml silica beaker. Cover with a clock glass and warm. Note (h). 2. When all traces of the metal have dissolved, rinse and remove the clock glass, rinse down the sides of the beaker, and evaporate the solution to dryness. 3. Cool (Note (i)), add 5 ml 16 M H'NOS, warm and add 5 drops 2 M HF to ensure complete solution. Evaporate to a moist residue. Note (j). 4. Redissolve this regidue in 10 ml 8 _I\gHNOa, warming to ensure complete solution. 5. Transfer the solution to the KelF/TBP column using the minimum volume of 8 M HNO3 to rinse out the beaker. WNote (k). 6. Place a 50-ml tall-form silica beaker containing 1 ml 20 gg/ml Sc solution under the column. Note (1). 144 Notes 10. 11. 12. 13. (a) (b) (c) (d) (e) (f) (g} (h) (i) (j) (k) (1) Allow the solution from (5) to drain down to the top of the chromatographic column maintaining a flow rate of approximately 0.5 ml/min. Add40ml 8 M HNO, and allow to drain through the column at the same rate. Transfer the eluted solution to a 100-ml separating funnel and wash with 10 ml conditioned CC14, repeat the wash with two further portions of 10-ml CCl4. Transfer the washed solution to the 50-ml beaker and evaporate to dryness in a fume cupboard. Note {m). Redissolve the residue in 1 ml 6 M HCl while the beaker is still warm. Duplicate reagent blanks are prepared using the procedure and re- agents above, but omitting the Pu. Prepare the electrodes for sparking by pipetting 0.1 ml of the solution from (10) on to the tops of a pair of waterproofed graphite electrodes, dividing the aliquot equally between the two electrodes, and dry under an infrared lamp. Prepare duplicate pairs of electrodes for each standard sample and reagent blank golution. Note (n). Remove the adsorbed Pu from the column by eluting with 0.32 M HNO3 {Note (o)) and then wash the column with water to remove the HNO,. Note (p). Prepared from gaseous HCl and deionized water, HNO, AR redistilled from silica apparatus. Diluted with deionized water. Prepared from HF AR and delionized water. CC14 AR conditioned before use by shaking with an equal volume of 8 M HN03. Commercial TBP purified by steamn distillation and alkaline washing (see Appendix). Low density KelF moulding powder, less than 100 mesh (see Appendix). 0.1% Apiezon M in CC14. Each sample should be done in duplicate. A vigorous reaction occurs if addition of concentrated HNO3 is made to hot residue. If the residue is allowed to go to dryness it will be difficult to re- dissolve, See Appendix for column preparation. Vitrosil tall-form beaker nominally 50 ml capacity in fact has a volume of about 75 ml. 145 (m} (n) (o) (p) The activity of the solution is due almost entirely to the Am content of the Pu metal. In general this is sufficiently low to allow a number of solution to be evaporated to dryness at one time without exceeding the tolerance limit allowed in a fume cupboard. Each sample and reagent blank will thus have four exposures. Transfer the solution to the appropriate residue bottle. The column life is limited as some TBP is washed off with each run. The effect of this is that the adsorbed Pu layer becomes longer with each run and the column must be replaced when the danger of Pu break-through becomes apparent. Purification of TBP Appendix 1. 2. 3. 4. Place 250 ml commercial TBP and 100 ml 0.5 M 'NaOH in a 1-litre flask fitted with a splash head for steam distillation. Heat the mixture to 80°C, but take care not to heat above this temperature. Note (a). Remove the source of heat and steam distil for 3 hr, rejecting the distillate. Note (b). Pour the hot TBP/NaOH mixture into a separating funnel and reject the (lower) aqueous phase. Wash the TBP with two 100-ml portions of hot deionized water and then with two 100-ml portions of cold deionized water. Note (c). Filter (Whatman 541 paper) the washed TBP into a clean dry reagent bottle, Preparation of KelF Powder 1. Chill KelF low density molding powder with solid CO2 and grind in a microhammer mill. Note (d). Sieve the milled powder and collect the material passing 100 mesh (BSS). Note (e). Wet the powder with acetone, transfer to a 1-liter beaker and add excess of 6 M HCL (Note (f)). Allow the KelF/HCl suspension to stand overnight. ' Pour the KelF/HC1 suspension into a funnel fitted with a cotton wool plug and allow the acid to drain away. Wash the KelF free from acid by pouring deionized water through the funnel. Finally, dry the washed KelF by pouring acetone through the funnel and then spreading the powder out onto a polythene sheet and allowing the acetone to evaporate. Preparation of Column 1. Mix 12 g KelF powder and 12 g TBP to a smooth paste, add about 10 ml deionized water and mix to a slurry. 146 Notes (a) (b) (c) (d) (e) () (g) (h} Transfer about a quarter of this slurry to the column (Note (g)) filled with water and gently press small quantities of this slurry down with a glags plunger so that an evenly packed column of the KelF/TBP is formed. Note (h). Repeat this procedure with further portions of the slurry until the column is complete. Keep the column filled with water until required for use and condition with 40 ml 8 M HNO3 when required. TBP/NaOH mixtures bump violently. This removes most of the free n-butyl alcohol from the TBP; the remainder is removed by washing. The initial sepafation and washings must be done hot to avoid emulsification. Chilling assists the grinding process. Making the powder just moist with acetone will prevent it sticking to the sieve. To remove any metallic impurities. . , 28 cm X 1.2 cmn Pyrex calumn, 2-mm bore tap and fitted with a quartz wool plug. Care must be taken in the preparation of the column, loose packing may result in Pu breakthrough during elution; tight packing will give a very slow flow rate. 147 Procedure 17. Separation of Np and Pu by Anion Exchange N. Jackson and J. F. Short (Ref. 204) QOutline of Method This procedure is desgcribed for macro amounts of Pu and Np. Tt is based on the fact that Pu(IIl) is not adsorbed on anion exchange resin, while Np(IV) is strongly adsorbed at high HC1 concentrations. The valence adjustment is done before adsorption on the column by dissolving the hydroxides in a concentrated HCI solution which has been saturated with NH4I. The Np is removed from the column with 2 M HCl. The separation is quantitative and complete. Procedure The purification of 2.3 g of Np237 from approximately50mg of Pu239 was then undertaken. The Np and Pu were precipitated as hydroxides, cenirifuged, and dissolved in 210 ml of conc. HCI1 sat. with NH4I. The solution was allowed to stand for 30 min and poured onto a Deacidite FF anion column 20 ¢m long and 2.5 cm diameter while a flow rate of 1 ml/min was mainta.ined. The first 200 ml of effluent were pale blue [Pu(IIl)]. The. column was then washed with 100 ml conc. HCl and the wash collected separately. No activity was found in a drop collected at the end of the washing. The Np was finally eluted with 2M HCl. It was possible to follow the dark green band of the Np down the column and the first 40 ml of eluate was included with the conc. HC1 wash. The whole of the Np was collected in the next 50 ml of eluate, No activity was found in any eluate after this stage. Some 8-y activity was detected on the glass wool at the top of the resin column and was assumed to be Pa233, the daughter of Np237. 148 Procedure 18. Separation of Np and Pu by Cation Exchange Chromatography V. D. Zagrai and L. I, Sel'chenkov (Ref. 435). Qutline of Method Np(IV) and Pu(IlI) are adsorbed on the cation resin KUl or KU2 from 0.25 M HCI1 solution after reduction with SOZ at boiling water temperatures. Np is eluted with 0.02 N HF and the Pu stripped with 0.5 N HF. Procedure 1. To 6-8 ml of 0.25 N HCI containing ug amounts of Np and Pu, add about half of the resin in the hydrogen form required to fill the plexi- glass column (1 mm diameter X 90 mm high) and 1-2 ml of water. 2. Pass SO2 gas through the solution vigorously for 15-20 min while heating on a boiling water bath. 3. Allow the solution to cool to room temperature and transfer the resin to the column with a pipette. Plug the top of the column with cotton and pass the remaining solution through the column. Wash the resin with 10 ml of 0.25 N HCI, followed by 10 ml of H,O. 5. Elute the Np into a Pt dishor a Teflon beaker with 40-60 ml of 0.02 N HF. 6. Elute the Pu with 4-5 ml of 0.5 N HF. 149 Procedure 19. Determination of Plutonium in Urine R. O. R. Brooks (Ref. 56) QOutline of Method A 24-hr gsample of urine is dried and ashed and the residue dissolved in dil. HCl and adjusted to a pH of 1. The Pu is reduced to the trivalent state with hydroxylamine hydrochloride solution and co-precipitated on iron cupferride. This is extracted with chloroform, the chloroform is distilled off, and the cupferrides residue is wet oxidized. Thé iron carrying the Pu is finally mounted wi;ch conc. HCI, dried, precipitated with ammonium hydrOxide, dried again, and flamed off to Fe203. This 233 procedure is based on that described by Smales et al. Differences in the two procedures are given at the end of this procedure. Reagents Ferric chloride solution. 145 mg of FeC13/1iter (i.e. 50 mg Fe/liter). Hydroxylamine hydrochloride solution. 50 g of NHZOH-HCI/liter. Cupferron. 5% aqueous solution, renewed weekly. Procedure 1. Evaporate a 24-hr sample of urine overnight in a 2-liter porcelain basin under infrared lamps. 2. When dry, scrape out and quantitatively transfer the regidue to a 200-ml sgilica dish with washings of 4 N HCI, and re-dry it under infrared lamps. 3. Place the sample in a muffle furnace at 500°C, and hasten oxidation by periodic additions of 3-ml lots of conc. HNO3 to the dish when it is cool. 4. Dissolve the white residue in ~30 ml of 4 N HCI, transfer to a 250-ml beaker and make up with alternate 4 N HCI and water washings to about 100 ml to a final acidity of 2 N. Stir until only an insoluble silica residue remains. Add 5 ml of FeCl3 sclution and 10 ml of NHZOH' HC1 solution followed by a few drops of cresol-red indicator. 5. Adjust the pH of the solutionto 1 (with a pH meter until the operator can correctly do it visually) with 2 N NH4OH added dropwise from a burette with constant stirring. It is essential that no phosphate precipitate forms, as this may reduce recoveries. Allow the solution to stand for 1 hr to ensure reduction of Pu(VI) to Pu(IIl). 6. Transfer the solution to a 500-ml separating funnel and add 2 ml of 5% cupferron solution, Shake the contents thoroughly and let stand for 3/4 hr to allow complete formation of iron cupferride. 7. Add 30 ml of chloroform and shake the funnel thoroughly. Allow the chloroform layer to settle and then run it off through a 7-cm Whatman No. 41 filter paper into a 100~-ml scparating funnel. Wash the chloroform by shaking with 20 ml of distilled water and run the 150 10. 11. 12. 13, 14, chloroform into a 250-ml round-bottomed flask through a 7 cm No. 41 filter paper as before. Return the water to the original aqueous golution and add a further 5 ml of FeCla and 2 ml of 5% cupferron as 2 scavenge. After shaking, leave the solution to stand for another 3/4 hr. Extract the cupferrides with three 15-ml lots of chloroform — or until the chlorlform remains colorless — and filter each lot separately into the 100-ml funnel. Wash the filter paper with chloroform from a pipette to remove the ring of cupferrides which forms around the top, and collect the washings in the 100-ml separating funnel. Add 20 ml of distilled water to the chloroform extracts, and shake the funnel. After they have settled out, filter the extracts into the 250-ml round-bottomed flask and wash the filter papér with chloroform. Evaporate off the excess chloroform in a fume cupboard using an "Electro-Thermal'" mantle. Remove the final drops by blowing in air. Add 3 ml of conc. H2304 heat. Evaporate the final traces of HZSO4 by blowing in air. If the and 1 ml of conc. HNO3 to the residue and residue is not white, add further aliquots of the acids and take to dry- ness again. Dissolve the residue in 3 ml of conc. HCI and transfer by means of a pipette to a Pt tray previously counted for background. Use two further 3-ml aliquots of conc. HCI to obtain a quantitative transfer. Dry the final solution, then take up in a few drops of water and add enough 2 N NH 4 Spread this precipitation evenly over the tray (15 c:m2 effective surface) OH toensure complete precipitation of ferric hydroxide. using a glass rod with a fine tip. Dry the tray, and finally heat it over a bunsen to form the red oxide Fe203 before counting. Counting Procedure Count the tray '"background'" and sample each for one period of 8 hr in an a-scintillation counter. Calculating Maximum Permissive Level in Urine Maximum permigsive level in the body is 0.04 uc for Pu239 (solution), Excretion rate assumed is 0.01% per day. Corresponding Maximum Permissive Level in Urine is .. 4 puc With a method recovery of 90% and a counter efficiency of (say) 35%, the maximum permissive level in urine = 2.8 cpm above "background." 151 Reporting Results Results are reported in puc/24-hr sample in the following ranges: < 0.1 pyuc <1l >0.1uuc > 1 puc (exact figure reported with standard deviation). NOTE: Deviations from this report in steps 4, 7, and 8 above were made for reasons of economy. The use of smaller quantities of reagents were found not to affect the overall recovery. By using the amounts of HZSO4 and HNO3 quoted in step 11 above, a more rapid oxidation was achieved. 152 Procedure 20. Determination of Pu239 in Urine (Small Area Electrodeposition Procedure) R. W. Perkins (Ref. 316) QOutline of Method This procedure describes a method for the rapid separation of Pu239 from 200 ml (or smaller) urine samples, and the subsequent electrodeposition of the Pu239 on an E!—rnm2 area of a stainless steel disk. The yield for a set of five samples was 85.2 percent +3.6 percent standard deviation. Procedure 1. Place the urine sample (200 ml or less) in a 1-liter Erlenmeyer flagk, add 50 ml of concentrated HNOB, 40 mg of Pr carrier (Note (a)} and evaporate to about 20 ml. Add 20 ml of HZO and cool under running water, then transfer the solution to a 100-ml Lusteroid test tube (using about 20-30 ml of wash water) containing 5 ml concentrated HF and stir. 2. Allow the sample to stand 30 min, centrifuge 2 min, discard the super- nate and dissolve the precipitate in 50 ml of 2 N I-1'NO3. Add 5 ml of concentrated HF and stir. Allow the sample to stand 5 min, centrifuge 2 min, discard the supernate and digsolve the precipitate in 5 ml of HZO and 20 ml of 2 MAI(NO3 3—0.5 N HN03. 3. Transfer the solution to 2 120-ml separatory funnel and shake 5 min (or until clear). Add 0.25 mlof 2 M Na.NO2 and shake 15 min. Add 10 ml of 0.45 M TTA (100 g/liter) in benzene and shake for 20 min. Discard the agueous phase and wash the organic phase with two 10-ml portions of 0.5 N HNOs, 5 min each. . 4. Add 10 ml of 8 N HCI and shake 15 min. Collect the aqueous layer in ~a 50-ml beaker. Add 5 ml of 8 N HCI to the organic phase and shake 5 min. Collect the aqueous phase. 3. Combine the aqueous layers, add 5 ml of concentrated HNO3, 3 ml of concentrated HC104, l1mlof 0.1 M KNO3 and evaporate to dryness. (Use low heat for final evaporation.) 6. Dissolve the regidue in 7 ml of 0.5 EHNO3 (Note 2). Rub sides of beaker with policeman to make sure all of the residue is in solution. Wash policeman with water, adding washings to the sample, then evaporate the solution to 3-4 ml. 7. Add 4 ml of electrolyte (0.26 M (NH4)2 C204), transferring the solution to an electrodeposition cell with an 8-mm? stainless steel cathode area (Note 3). B. Electrodeposit overnight at 110 mA. The electrodeposited sample may be counted directly on a low back- ground o counter, or exposed to a nuclear track film and the o tracks counted under a microscope* io provide a greater sensitivity. L. C. Schwendiman and J. W. Healy, Nucleonics 16, No. 6, 78, 80-82 (1958) June. 153 Notes The element praseodymium as purchased (from the Lindsey Chemical Division of the American Potash and Chemical Corporation, West Chicago, Illinois) could be used directly without causing 2 high back- ground; whereas, the use of lanthanum' as a carrier resulted in a high backgrbund. At this point, the sample can be evaporated on a counting dish for direct counting if small area deposition is not required. The eléctroly'tic cells consist of lucite cylinders which are threaded at one end for stainless steel caps which contact the stainless steel cathode plating surfaces. A beveled lucite disk fits between the cap and cylinder and-defines the electrodeposition area. 154 Procedure 21, Determination of Plutonium in Urine R. J. Everett et a1.125 Outline of Method Micro amounts of Pu are isolated by lanthanum fluoride coprecipitation, thenoyltrifluoroacetone (TTA) extraction, and electrodeposition. The a activity is measured by proportional counting or by autoradiography. Evaporation and Electrodeposition Reagents and equipment. Electrodeposition apparatus and cells, Stainless steel disks, 0.5-in. diam X 0.005-in. thick, polished stain- lesa steel. Aluminum nitrate solution — Dissolve 378 g Al(NOB)a- 9H20 in 800 ml distilled water; add 23 ml conc. HNO:3 and dilute to 1 liter with distilled water. Conc. ammonium hydroxide — NH4OH(30% NH3). Ammonium hydroxide, 10% golution— Dilute 10 ml conc. NH4CH to 100 ml with distilled water. Conc. hydrochloric acid, 36% HCI. Conc. hydrofluoric acid, 48% HF. Conc. nitric acid, 70% HNO3 Conc. phosphoric acid, 85% H PO4 1 N nitric acid — Dilute 63 ml conc. HNO3 to 1 liter w1th distilled water. _ 2 N nitric acid — Dilute 125 ml conc. HNO3 to 1 liter with distilled water. 8 N hydrochloric acid — Dilute 667 ml conc. HCI to 1 liter with dis- tilled water. . 8 N potassium hydroxide — Dissolve 112 g KOH in 250 ml distilled water. 2 N potassium hydroxide — Diggolve 28 g KOH in 250 ml distilled water. Sodium hypochlorite — 5% solution NaOCl. Sodium nitrite solution — Dissolve 1.2 g NaNO, in 10 ml distilled water. Prepare fresh imrnediately before use. Hydroxyldamine hydrochloride — NH20H- HCI. Lanthanum nitrate solution — Dissolve 6.2 g La(N03)3- 6H,0 in 100 ml 1N HNOS. 1 ml = 20 mg La. Thenoyltrifluoroacetone solution — Disgolve 5 g thenoyltrifluoroacetone (TTA) in 100 ml benzene. Procedure 1. To 1 liter urine in a 2-liter beaker, add 20 ml conc. HN03, 5 ml conc. H3PO4, and heat to 85°C., 2. While stirring, add conc. NH4OH until precipitation occurs. Add 10 ml excess and continue heat and stirring for 1 hr. 155 10. 11. 12. 13. 14, 15. 16. 17. 18. 19. 20. 21. 22, 23. Cover the beaker and let settle overnight. Decant the supernate, being careful not to disturb the precipitate. Filter the precipitate onto Whatman No. 50 filter paper. Wash the precipitate with 10% NH4OH. Discard the filtrate. Place filter and precipitate in 50~ml Vycor crucible and ignite at 800°C for 1 hr. Cool residue and add 25 ml 2N HNO,. Transfer to centrifuge tube with 2N HNO3 wash, and keep volume Warm to dissolve residue. less than 50 ml. Cool to room temperature and add 1 g NH,OH- HCL. Stir until it disgolves. Add 1 ml LEL(NO3 )3 golution and adjust volume to 75 ml with 2N HNOgj. Stir and add 7 ml conc. HF. Let stand 2 min, then remove stirring rods. Let stand 3 min more, then centrifuge and carefully discard the supernate. To residue, add a few ml 25\1_ HNO3 and stir vigorously. Add 2§ I-INO‘.3 in portions, while stirring, until volume is 75 ml. Repeat LaF3 precipitation by adding 7 ml conc. HF as in step 9, then let stand for 3 min. Centrifuge, and discard the supernate. Break up precipitate with stirring rod and add 2 ml Al(N03)3 solution. Stir vigorously and add 38 ml more Al(N03)3. Transfer the solution to a separatory funnel. Add 5 drops NaNOQ, solution and mix. Let stand 15 min. Add 10 m]l TTA solution and extract 20 min. Let phases separate and discard aqueous layer. Note: For a rapid analysis, the TTA can be evaporated on a planchet for counting. Otherwise, proceed to step 17. Add 20 ml distilled water and extract 5 min. Let phases separate and digcard aqueous layer. Add 10 ml distilled water and repeat. Add10ml 8N HCl and extract 20 min. Let phases separate and drain HCI layer into 50-ml beaker. Repeat extraction. Carefully evaporate the two HC1 extracts to 1 ml. Do not boil or let go dry. Cool and add 8N KOH by drops until a pale reddish-brown color appears. Add 5 ml 2N KOH and 2 ml 5% NaOCl solution. Evaporate carefully to one-half original volume. Transfer to electrodeposition cell, washing the beaker once with 1 ml NaQOCl solution and three times with distilled water. , Connect cell to electroplater and electrolyze 5 hr at 80 mA. Remove cell without interrupting current. Discard solution. Remove disk from cell and wash with distilled water. Let dry and flame lightly. The disk can now be ¢-counted or autoradiographed.- 156 Autoradiography Reagents and equipment. Developer, Kodak D-19. Fixer, Kodak F-5 Nuclear-track alpha (NTA) plates — 1-in. X 3-in. glass slide with 25-u emulsion. NTA exposure camera. Microprojector — arc illuminated, with 21X objective and 20X ocular. Chromic acid solution — Dissolve 0.2 g CrO3 in 1 liter distilled water. Plate preparation 1. Fill staining dish two-thirds full of CrO3 solution. 2. In darkroom with red safe light, remove slides from box and place in staining-dish rack. Immerse rack and slides in CrO3 solution for 4 min. Let drain 5 sec. Turn off red safe light and wash in ringe tank 20 min. 3. Remove rack from wash tank and let slides dry. Autoradiographic procedure 1. In darkroom with Series AO light filter, load NTA plate in slide depression of camera. Place disk positioner over NTA plates, and drop disks face-down into holes of positioner. 2. Fit top securely on camera, and place camera in dark box. Expose for 1 week. ) 3. After exposure, develop NTA plates 10 min in D-19 developer at 68°F. Rinse in distilled water and fix 20 min in F-5 fixer. Wash plates for 1 hr and let dry. Count the ¢ tracks with the microprojector- Each projection covers an area of 0.1409 mmz, which is called one field. The total area of the exposed NTA plate is 38.82 mm?> or 277 fields. Tracks are counted on a predetermined number of fields on each plate. "Tracks found are compared with a standard curve prepared from urine spiked with known amounts of Pu. Calculation Since 1 liter urine sample was used, dpm Pu/liter urine = dpm from standard curve. References S. M. Sanders, Determination of Plutonium in Urine, DP-146, March 1956. .. C. Schwendiman and J. W. Healy, '"Nuclear-Track Technique for Low-Level Plutonium in Urine," Nucleonics 16, 78 (1958). 157 Procedure 22. Determination of Americium in Urine in the Presence of Plutonium D. L. Bowkowski (Ref. 53). Outline of Method The Pu is co-precipitated with BiPO4 from acidified urine, the BiPO4 is wet-ashed with HNOB, and the Pu is co-precipitated with LaF3 from an HCl solution. The LaF3 co-precipitation is repeated and the fluoride is metathesized with KOH. Puis extracted into di(2-ethylhexyl)phosphoric acid from a 2 M HNO3 solution, and the aqueous phase i8 mounted for counting. This procedure is included to illusirate the extraction of Pu(IV} into acidic phosphate extractants. The procedure could presumably be used for a simultaneous determination of Pu and Am in urine, by back-extraction of the Pu either into strong acid or a reducing solution. Reagents Bromthymol blue indicator solution — Dissolve one g of reagent grade indicator in 500 ml of distilled water made alkaline with one pellet of sodium hydroxide. 3)3- 5H20-AR] in 660 ml of concentrated HNOB.and dilute to one liter with distilled water. This Bismuth nitrate solution — Dissolve 231.2 g of bismuth nitrate [Bi(NO solution contains 0.1 g of Bi per ml. 4 N HCl — Add 344 ml of conc. HCI to approximately 500 ml of digstilled water in a volumetric flask and make up to 1 liter with distilled water. 6 N HCl — Dilute 510 ml of conc. HCI to 1 liter in a volumetric flask. 8 N HC1 — Dilute 688 ml of conc. HCI to 1 liter in a volumetric flask. Lanthanum nitrate solution — La(NO3)3' as received from the Lindsey Chemical Company, West Chicago, Illinois, is freed from actinum o-emitting impurities on a * Dowex 50X12 cation exchange resin column by the method of Farabee. The lanthanum nitrate stock solution obtained is used to prepare working solutions containing 25 mg of La+++/ +++ are used. ml. Only solutions containing 0.05 d/min or less of ¢ activity per mg of La 2 M Hydroxylamine hydrochloride — Dissolve 139.0 g of C. P, grade hydroxylamine hydrochloride and dilute to one liter. Store in brown bottle. 2 N Sodium nitrite solution — Dissolve 13.8 g of sodium nitrite (NaNO,-AR) in distilled water in a 100-ml volumetric flagk and make to volume with distilled water. Prepare fresh.before use. 0.1 M DZ2EHPA — Add 32.3 g of di(2-ethylhexyl)phosphoric acid (Union Carbide Chemical Company) to chloroform-AR in a 1-liter volumetric flask and make to volume with chloroform. 8 N KOH — Dissolve 65.3 g of potassium hydroxide (KOH 86%-AR) in distilled water and dilute to 1 liter, All other chemicals are either of reagent or C. P. quality. *L. B. Farabee, 5th Ann. Meeting-Bioassay and Analyt. Chem. Grp., Oct. 1-2, 1959 (USAEC Report TID-7591 Nov. 1960 p. 78). 158 Sample Pretireatment The volume of a "24-hr equivalent' urine sample (two morning and two evening voidings) is measured and the sample transferred to a 2-liter beaker. The volurne and the liquid level are denoted on the beaker with a china-marking pencil or marking pen. Several glass beads, 1 ml of octyl alcohol and 200 ml of concentrated nitric acid are added. The beaker is covered with 2 Speede-Vap and placed over an asbestos pad on a hot plate at high heat. The sample is digested by gentle boiling until it attains a clear appearance. BiPO 4 Coprecipitation A stirring bar is added to the cooled solution and rapid stirring initiated over a magnetic stirring motor. Approximately 130 ml of concentrated ammoniumn hydroxide are added cautiously, followed by 1 ml of bromthymol blue indicator solution. Neutralization is completed by addition of concentrated ammonium hydroxide to the yellow-green endpoint. If necessary, the sample volume is readjusted to its oi'iginal value with distilled water. Concentrated nitric acid is added to make the solution 0.15 M in HNO, (Table VIII-1). 500 mg of hydroxylamine hydrochloride are added to the solution and the beaker placed in a steam bath heated to 80 +5°C. Concentrated phosphoric acid is then added to a concentration of approximately 0.09 M (Table VI‘I_‘[-l)I. An amount of bismuth nitrate solution, equivalent to 60 mg bismuth per 100 ml, is "added dropwise to the heated, stirred solution. . | The precipitate is digested by an BigéBL}iEe‘figi;tfiiiluuon Requirements for additional hour of stirring at 80 + 5°C. 4 . The sample beaker is removed from the TUrine Conc. HNO3 solume Tor 6.15 M H,PO, Bi(NO,), water bath and allowed to stand un- (m1l) (ml) (ml) soln, (ml) . disturbed for a minimum of 3 hr. The 500 4.8 3.0 3.0 supernatant solution is carefully 600 5.9 3.8 ‘3.6 . . . . .. 700 68 4.9 4.9 agpirated off (avoid disturbing precipitate) 800 7.2 4.8 4.8 and the precipitate transferred to a 90- 900 8.7 5.4 5.4 . . . ml Pyrex centrifuge tube with a distilled i?gg 1gg gg gg water rinse. The precipitate is cen- 1200 11.6 7.2 7.2 trifuged for 5 min at 2000 rpm and the 300 7 g ' 1480 iggg 8.2 gg supernate carefully discarded. The 1500 14.4 9.0 9.0 sample beaker walls are then rinsed down 1600 15.0 9.6 9.6 with 4 N HCI from a wash bottle and the iggg igg 1328 133 ringe transferred to the 90-ml tube. The 1900 18.5 11.4 11.4 final volume in the tube should be approxi- 2000 19.2 12.0 12.0 mately 50 ml. Wet-ashing of Bismuth Phosphate Several drops of coctyl alcohol are added to the HC1 solution in the 90-ml tube; it is placed in an aluminum block af approximately 100°C, and the solution taken to dryness. The dried sample is then repeatedly wet-ashed with several drops of 159 concentrated nitric acid in a block heated to 350°C. After the sample has ashed to whiteness, itis evaporated twice with 8 N HCI. Lanthanum Fluoride Coprecipitation The bismuth chloride ash is dissolved in 8 ml of 8 N HCI and the solution is transferred to a 25-ml conical centrifuge tube. The walls of the 90-ml tube are rinsed with an additional 2 ml of 4 N HCI and the ringe added to the centrifuge cone. After addition of 0.1 ml of La(N'O3)3 solution, the tube contents are mixed thoroughly. Two ml of concentrated hydrofluoric acid (27 M) are then added, and the solution stirred with a Pt stirrer. The tube is allowed to stand for 5 min and then centrifuged at 2000 rpm for 3 min. The supernatant is carefully aspirated and the precipitate dis- solved in 2 ml of concentrated HCI. Following the addition of 2 ml of distilled water, L:-LF3 is reprecipitated by addition of 2 ml of 27 M HF. The preceding digestion and centrifugation steps are repeated. Five ml of 8 N potassium hydroxide are added to the precipitate and care- fully heated to boiling. After cooling the mixture is centrifuged for three minutes and the supernate carefully drawn off. D2EHPA Extraction Following solution of the precipitate in 6 ml of 2 N HNOS, one ml of 2 M hydroxylamine hydrochloride is added, and the sample is heated in a water bath at 70°C for 5 min. The tube is then removed from the water bath and 2 ml of 2 M sodium nitrite solution are added with swirling. When bubble evolution ceases, the solution is transferred to a 30-ml separatory funnel. The centrifuge tube is rinsed once with 3 ml of 2N nitric acid and the rinse added to the separatory funnel. The aqueous layer is then extracted thrice with 5-ml portions of 0.1 M D2EHPA in chloroform for 5-min periods. The chloroform extracts are removed and the aqueous layer is shaken for 3 min with a 5-ml portion of toluene. The aqueous portion is then withdrawn through the funnel stem into another 25-ml conical centrifuge tube. Lanthanum fluoride is pre- cipitated by addition of 2 ml of 27 M HF. The solution is allowed to stand 5 min centrifuged at 2000 rpm for 3 min and the supernatant drawn off and discarded. Shake the precipitate with 10-15 ml of 1:100 hydrofluoric acid wash solution and centrifuge at 2000 rpm for 5 min. Sample Planchetting Aspirate the supernatant and invert the centrifuge cone quickly over ab- sorbent tissue. Drain 15 min. Slurry the precipitate with distilled water and transfer to a stainless steel planchet with a disposable capillary pipette. Dry the disk under an infrared lamp and flame the dried planchet to red heat. The o activity is then counted with a low-background proportional counter for 150 min. 160 Procedure 23. Determination of Plutonium in Urine by Anion Exchange E. D. Campbell and W. D. Moss (Ref. 74) Outline of Method Pu is concentrated from urine by co-precipitation with alkaline earth phosphates. The precipitate is dissolved in 7.5 N nitric acid and the Pu absorbed from that solution onto Dowex 1 X 2 anion exchange resin. Interfering anions ab- sorbed on the column are removed with 12 N HC1l. The Pu is eluted from the column with specially prepared hydrochloric and hydriodic acids, and the o activity determined by direct planchetting or by electrodeposition of the eluate, followed by standard a- counting techniques. Equipm ent Ion exchange column. The ion exchange column container consists of a glass reservoir, 2-5/8 in. long by 1-3/32 in, i.d., capacity 40 ml, on a chromato- graphic column tube 3 in. long by 5/16 in. i.d., constricted at the tip. Solutions Hydriodic acid stock solution. Prepared by distilling hydriodic acid (analytical reagent grade, 5.5 M in hydriodic acid, 1.5% hypophosphorous acid pre- servative)under nitrogen. The hypophosphorous acid preservative interferes with the electrodeposition step and also with the preparation of satisfactory planchetted samples. Oxidation of the prepared hydriodic acid solution is inhibited by adding enough hydrazine (up to 20% by volume of 64% to 84% hydrazine in water) to decolorize the hydriodic acid solution. Hydrochloric acid-hydriodic acid elutriant. Prepared by mixing 1 ml of hydriodic acid stock solution with 9 ml of concentrated hydrochloric acid. The pre-~ cipitate formed by hydrazine is removed by centrifuging; the supernatant then is saturated with gaseous hydrogen chloride. The reagent must be prepared every few days because it decomposes easily. Reagents All other reagents used in the procedure are prepared from analytical grade chemicals. Preparation of Ion Exchange Column A glass wool pledget in the tube supports the resin. The tube is filled with from 2-1/2 to 3 in. of a distilled water slurry of Dowex AG1-X2. chloride form, 50 to 80 mesh, anion exchange resin (Bio-Rad Laboratories, 32nd and Griffin, Richmond, Calif.). The resin in the column is converted to the nitrate form by washing with at least two 5 ml portions of 7.5 N nitric acid before adding the sample gsolution. The resulting column flow rate is 1 ml/min. 161 Preparation of Sample The 24-hr or equivalent urine sample is transferred to a 2-liter graduated cylinder with concentrated nitric acid (50 ml of acid per liter). The cylinder is heated in a steam bath at 75 to 80°C, and stirred with a magnetic stirrer, for 30 min. One ml of phosphoric acid is added to the sample, then enough concentrated ammonium hydroxide to form a copious precipitate, and the sample is digested, with continuous stirring, for 1 hr. After 30 min of digestion the stirrer is stopped, the precipitate is allowed to settle for several minutes, and the clear supernatant is treated with several ml of ammonium hydroxide to be sure precipitation is complete. Should more precipitate form, an excess of ammonium hydroxide is added, and the stirring is continued for the remaining 30 min. After the cylinder is removed from the wadter bath and the stirring bar from the cylinder, the sample is allowed to remain undisturbed overnight at room temperature,. . The following morning the supernatant is aspirated from the precipitate and dis- carded. The alkaline earth phosphate precipitate is transferfed to a 90-ml centrifuge tube with distilled water and centrifuged. The supernatant is discarded, the cylinder is washed with dilute (20%) nitric acid, and the'v;fashings are combined with the pre- cipitate in the tube. The material in the tube then is evapprated to dryness in an aluminum heating block at 85 to 90°C, and the residue finally. is -whitened with con- centrated nitric acid at approxiinately 300°C, Ion Exchange. Isolation of the Pu The ashed residue from the alkaline earth phosphate precipitfite is dis- solved in 25 ml of 7.5 N nitric acid. The residue may be t:iissolved with heat if necessary, but will dissolve easily at room temperature ovérnight (preferred method). .The acid solution is transferréd to the reservoir of a prépared ion exchange column and allowed to drain completely. The centrifuge tube is rinséd with three 5-ml portions of 7.5 N nitric acid,. each rinse being allowed to drain through the column before the next is added. The column reservoir then is washed down with 5 ml of 7.5 N nitric acid, which is allowed to drain'through the column completely.. Three ml of concen- trated hydrochloric acid are added carefully to the top of the resin without disturbing the resin, keeping dilution from the 7.5 N nitric acid to a minimum, and allowing the hydrochloric acid to drain completely.” All effluents from the absorptlion and washing steps are discarded. One to twe ml of 0.5 N HCI are added to the top of the column, the first several drops discarded, and the remaining eluate retained in a 15-ml centrifuge tube. The column then is eluted with two 5 ml portions of 0.5 N HCI and allowed to drain completely into the ceritrifuge tube. Finally, several crystals of hydroxylamine hydrochloride are added to the top of the resin and 2 ml of h'ydribdic—hydrochloric_acid solution drained through the column and collected. | _ - NOTE: The hydroxylamine hydrochl'oride is e_ldded to the column to prevent immediate oxidation of the hydriodic acid. An excess of hydriodic-hydrochloric acid 162 golution should not be used because of possible interference in the electrodeposition step. The eluate in the tube then is evaporated to approximately 1 ml in an aluminum heating block at 75°C. Electrodeposition The residue from the vaporation is neutralized with 8 N potassium hydroxide using phenolphthalein as indicator. When the solution is neutral, 2 ml of sodiurmn hypochlorite and 5 ml of 2 N potassium hydroxide are added to the tube, and the contents of the tube transferred to an electrodeposition cell with distilled water, (The final concentration of the alkali is 1 N.) The Pu is electrodeposited on 1/2 in. polished stainless steel disks at 200 mA for 5 hr. The apparatus and techniques for K the electrodeposition of Pu are described by Schwendiman et al. Determination of Alpha Activity The o activity on the stainless steel plates can be determined either by’ the NTA (Nuclear Track Alpha) emulsion method or by the standard electronic counting method. The background of the NTA method is 0.007 dpm, with an accuracy of 1.6 dpm. A method of choice for more rapid evaluation of results is the electronic determination of the ¢ activity by the phosphor-coated mylar method described by Hallden and Harley.** The phosphor method uses a 1-in. photomultiplier tube and an all-transistorized amplifier and counter system designed by P-1 (the Electronics Group of the Los Alamos Scientific Labhoratory's Physicg Division), similar to that described by Graveson et al.”> The background of this system is 0.015 cpm when adjusted to an optimum efficiency of 45%. The precision of this counting is satis- factory for 0.1 dpm. *L. C. Schwendiman, J. W. Healy, D. L. Reid, and G. E. Hanford, HW-22680 (1951). : “*N. ‘A. Hallden and J. H. Harley, Analyt. Chem. 32, 1861 (1960). *SR. T. Graveson et al., AEC New York Operations Office, Rpt. NYO 1523 (1950). (TID ORE, Oak Ridge, Tenn.) 163 Procedure 24. Determination of Plutonium in Urine by Co-crystallization with Potassium Rhodizonate W. H. Shipman and H. V. Weiss (Ref. 374) Qutline of Method Pu is co-crystallized with potassium rhodizonate by adding an equal volume of ethyl alcohol to a pH 9 solution of the reagent in urine. The Pu is further purified by co-precipitation with LaF, and adsorption on an anion exchange resin. The Pu is eluted with 6 N HCL - 0.2 N HF, electrodeposited and a-counted. Reégents Potassium rhodizonate (Paul B. Elder Co., Bryan, Ohio). Dowex anion exchange resin AG1-X8 (Bio-Rad Laboratories, Richmond, Calif.). Lanthanum carrier solution. Lanthanuwn nitrate was dissolved in water and purified from interfering « activity be passage through the anion exchange column after adjusting the HCI content to 10 N. Excess HCl was removed by evaporation and the salt was dissolved in 2 N HNO, All other chemicals were either of reagent grade or C.P. quality. to a final concentration of 5 mg of La-!_H- per ml. Procedure Based upon the experimental results, the following analytical procedure was evolved: The procedure is described for a 500-ml sample volume. For a dif- ferent volume, reagents are used in proportionate amounts. Add 1 g of potassium rhodizonate to the sample. (If the urine is not fresh, solubilization of the reagent may be difficult. Under such circumstances acidification of the sample with HC1 to pH 2 to 3 effects rapid solution.) Adjust to pH 9 with 5§ N NaOH and crystallize the rhodizonate with 500 ml of absclute ethyl alcohol. Let stand for several minutes and isolate the crystals by centrifugation. Dissolve the crystals in 50 ml of 2 N HNOa. mg of La+++ per ml) and precipitate with 30 ml of 27 N HF. Centrifuge. Without Add 1 ml of lanthanum carrier (5 separating the precipitate from the liquid, add 0.5 ml of lanthanum carrier with stirring to the supernatant liquid and centrifuge. Discard the supernatant liquid. Dissolve the precipitate in 5 ml of saturated H3BO and 5 ml of concentrated 3 HCl. Add about 10 ml of distilled water and make alkaline with concentrated NH ,OH. Centrifuge. Without separating the precipitate from the liquid, add 0.5 ml of lan‘}thanum carrier with stirring to the supernatant liquid. Centrifuge. Discard the supernatant liquid. Dissolve the precipitate in a small volume of concentrated HNOS, add about 15 ml of water, and reprecipitate with concentrated NH4OH. Centrifuge. Without separating the precipitate from the ligquid, add 0.5 ml of lanthanum carrier with astirring to the supernatant liquid. Centrifuge. Discard the supernaiant liquid. Dissolve the precipitate in concentrated HNOg. Add about 3 ml of concentrated HZSO4 and heat to dryness. Dissolve the salts in 10 to 15 ml of 6 N HCl. Add 0.5 mlof 0.4 N NaNO2 and make 9 N with concentrated HCIl. Let stand 5 min. 164 Pour the solution through a Teflon column, 4 X 0.62 ¢m anion exchange resin AG 1-X8 (Cl: 0.297 to 0.144 mm) previously washed with 10 ml of 9 N HCl. Adjust the flow rate to 2 ml/min. Wash the column with 15 ml of 9 N HC!l. Elute with 30 ml of 6 N HC1-0.2 N HF. Collect the eluate in a Teflon beaker which contains 15 mg of NaCl. Evaporate to dryness. Dissolve the salt in concentrated HNO3 and transfer to glass. Add 3 ml of HClO4, 2 ml of H2504, and heat to dryness. Dissolve the salt in 1 ml of water and transfer to the electrodeposition cell fitted with a tantalum disk. Add 4 mlof 6 N NH4C1 golution and 2 drops of concentrated HC1. . Electrodeposit at 2.5 to 3.0 A for 20 min. Quench the cell with 1 ml of con- centrated NH4OH. Wash the solution from the cell with distilled water and dry the tantalum disk on a hot plate. Alpha count. 165 Procedure 25. Determination of Plutonium in Urine and Bone Ash by Extraction with Primary Amines F. W. Bruenger, B. J. Stover, and D. R. Atherton (Ref. 61) Qutline of Method Concentrated urine, or a solution of bone ash is made 1 M in H2504 and Pu is extracted by a mixture of highly branched primary alkyl amines. The Pu is then back-extracted with 8 M HCIl-and counted. Reagents and Equipment The o-detection instrument is a 27 proportional counter of conventional design capable of accepting 2-in. stainless steel planchettes; counter performance is checked with a U3OB standard supplied by the National Bureau of Standards. Primene JM-T, a mixture of tert-alkyl primary amines, 5% by volume in xylene, was purchased from Rohm and Haas, Philadelphia, Pa. The Primene solution is washed with half its volume of 1 M HZSO4 before use. Procedure Urine analysis. Urine is collected in polyethylene bottles over 10 ml of concentrated formic acid to avoid excessive hydrolysgis of urea, which would render the specimen basic and could result in loss of Pu by adsorption on the wall of the con- tainer. An aliquot of urine is transferred to a Kjeldahl flagk containing enough 5 M sto4 to attain an acid concentration of 2 M in the final sample. The solution is boiled without charring for about 1 hr. Thus far, volumes up to 500 ml have been extracted. For larger volumes, amounts of reagents are increased proportionally. The following amounts of reagents are used for 100-ml aliquots. The sample is filtered through borosilicate glass wool into a separatory funnel and is allowed to cool to room temperature, Twenty ml of a 5% solution of Primene JM-T in xylene is added to the sample and the mixture is8 shaken for 15 min. After separation of the two phases, the aqueous phase is put aside for a second extraction. The organic phase is waghed twice with 25 ml of 1 M H2804. Pu is removed from the organic phase with two 20-ml portions of 8 M HCl. The aqueous phase is again extracted with 20 ml of 5% Primene, and Pu is back-extracted from the Primene with 20 ml of 8 M HCL. The combined HCI fractions are dried under a heat lamp and then the organic contaminants are destroyed by heating over an open flame or in a furnace at 500°C. The Pu residue is dissolved in concentrated HNO, and transferred to a 2-in. -diameter stainless steel 3 planchette for ¢ counting. Bone analysis. Bone is ashed for 4 hr at 600°C and, after cooling, is dissolved in as little HNO3 as pogsible and diluted with H20 to a known volume, and a suitable aliquot of this solution is taken for analysis. The amount of bone ash should not exceed 250 mg for every 75-ml volume of the aqueous phase. The aliquots are evaporated to dryness under a heat lamp to minimize the amount of HNO3 and then put in solution with 4 ml of concentrated HCOOH, and a 60-ml portion of 2.5 M H,80, is added. This solution is heated in a water bath until it. is clear, and then transferred to a separatory funnel. Transfer is completed with a 10-ml rinse of distilled water. Any (33504 that forms does not interfere. Pu is extracted as described above. 166 Glossary A/CONF. 8/ Vols., 1-17 — Proceedings of the International Conference on Peace- ful Uses of Atomic Energy, held in Geneva, August 1955 (United Nations, New York, 1958). | A&CONF. 15/1 English Ed. Vols, 1-33 - Proceedings of the Second United Nations International Conference on Peaceful Uses of Atomic Energy, held in Geneva, September 1958 (United Nations, Geneva, 1958). AEC — Atomic Energy Commission AEC ~ Manhattan District and later Washington, D.C, AEC declassified Teports. ' ' MDDS—Manhattan District, Oak Ridge, Tenn. TID — Technical Information Division, Oak Ridge, Tenn. AECL - Atomic Energy of Canada, Ltd,, Chalk River, Ontario. (also CEI- and CRDC- prefixes followed by number.) ANL - Argonne National Laboratory, Illinois. CEA — France. Commissariat a 1'Energie Atomique, Paris. CEA-TR — Series assigned by the AEC to translations received from CEA. DP — E, I. du Pont de Nemours and Co., Savannah River Laboratory, Aiken, So, Carolina. EURAEC — United States — Euratom Joint Research and Development Program., HW — General Electric Co., Hanford Atomic Products Operation, Richland, Wagh. , JENER - Joint Establishment for Nuclear Energy Research, Kjeller, Norway. KAPL — Knolls Atomic Power Laboratory, Schnectady, New York. LASL — Los Alamos Scientific Liaboratory, New Mexico, (LA-, LAMS-, and LADC- prefixes followed by number, ) ORNL — QOak Ridge National Laboratory, Tennessee, USNRDL - U.S. Naval Radiclogical Defense Laboratory, San Francisco, Calif. UKAEA -~ United Kingdom Atomic Energy Authority. ' AEEW — Research Group, Atomic Energy Establishment, Win.t‘rith; Dorset. AERE — Atomic Energy Research Establishment, Harwell, Berks. AHSB(RP) — Health and Safety Branch, Radiological Protection Div., Harwell, Berks, AWRE ~ Great Britain Atomic Weapons Research Establishment, Aldermaston, Berks. 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Department of Com- merce, Springfield, Va. 22151 Aluminum and Gallium, NAS-NS-3032, $0.50 Amerncium and Curium, NAS-NS-3006, $0.75 - Antimony, NAS-NS-3033, $0.50 Arsenic, NAS-NS-3002, (Rev.)1965 $1.00 Astatine, NAS-NS-3012, $0.50 Barium, Calcium, and Strontium, NAS-NS- 3010, $1.25 Beryllium, NAS-NS-3013, $0.75 Cadmium, NAS-NS-3001, $0.75 Carbon, Nitrogen, and Oxygen, NAS-NS- 3019, $0.50 Cesium, NAS-NS-3035, $0.75 Chromium, NAS-NS-3007, (Rev.}1964 $0.75 Cobalt, NAS-NS-3041, $1.00 Copper, NAS-NS-3027, $0.75 Fluorine, Chlorine, Bromine, and Icdine, NAS-NS-3005, $0.50 Francium, NAS-NS-3003, $0.50 Germanium, NAS-NS-3043, $0.50 Gold, NAS-NS-3036, $0.50 Indium, NAS-NS-3014, $0.50 Iridium, NAS-NS-3045, $0.50 Iron, NAS-NS-3017, $0.50 Lead, NAS-NS-3040, $1.75 Magnesium, NAS-NS-3024, $0.50 Manganese, NAS-NS-3018, $0.50 Mercury, NAS-NS-3026, $0.50 Molybdenum, NAS-NS-3009, $0.50 Nickel, NAS-NS-3051, $0.50 Niobium and Tantalum, NAS-NS-3039, $0.75 Osmium, NAS-NS-3046, $0.50 Palladium, NAS-NS-3052, $0.75 Phosphorus, NAS-NS-3056, $0,50 Platinum, NAS-NS-3044, $0.50 Plutonium, NAS-NS-3058, $2.00 Polonium, NAS-NS-3037, $0.75 Potassium, NAS-NS-3048, $0.50 Protactinium, NAS-NS-3016, $1.00 - Radium, NAS-NS-30567, $2.25 Rare Earths— Scandium, Yttrium, and Ac- tinium, NAS-NS-3020, $3.00 Rare Gases, NAS-NS-3025, $0.75 Rhenium, NAS-NS-3028, $0.50 Rhodium, NAS-NS-3008, (Rev.)1965 $1.00 Rubidium, NAS-NS-3053, $0.50 Ruthenium, NAS-NS-3029, $1.00 Selenium, NAS-NS-3030, (Rev.)1965 $1.00 Silicon, NAS-NS-3049, $0.50 Silver, NAS-NS-3047, $0.,75 Sodium, NAS-NS-3055, $0.50 Sulfur, NAS-N8-3054, $0.50 Technetium, NAS-NS-3021, $0.50 Tellurium, NAS-NS-3038, $0.50 Thorium, NAS-NS-3004, $0.75 Tin, NAS-NS-3023, $0.75 Titanium, NAS-NS-3034, $0.50 Transcurium Elements, NAS-NS-3031, $0.50 Tungsten, NAS-NS-3042, $0.50 Uranium, NAS-NS-3050, $3.50 Vanadium, NAS-NS-3022, $0.75 Zinc, NAS-NS-3015, $0.75 Zirconium and Hafnium, NAS-NS-3011, $0.50 - Activation Analysis with Charged Particles, NAS -NS -3110, $1.00 Applications of Computers to Nuclear and Radiochemistry, NAS-NS-3107, $2.50 - Application of Distillation Techniques to Radiochemical Separations, NAS-NS- 3108, $0.50 Detection and Measurement of Nuclear Ra- diation, NAS-NS-3105, $1.50 Liquid-liguid Extraction with High- molecular-weight Amines, NAS-NS- 3101, $1.00 : Low-level Radiochemical Separations, NAS- NS-3103, $0.50 Paper Chromatographic and Electromigra- tion Techniques in Radiochemistry, NAS- NS-23106, $0.50 Processing of Counting Data, NAS-NS- 3109, $1.75 Rapid Radiochemical Separations, NAS-NS- 3104, $1.25 Separations by Solvent Extraction with Tri- n-octylphosphine Oxide, NAS-NS-3102, $0.75