- ~ OAK RIDGE NATIONAL LABORATORY operated by UNION CARBIDE CORPORATION for the U.S. ATOMIC ENERGY COMMISSION ORNL- TM-458 copyno. - ¥/ DATE - Dec. 1k, 1962 SOME CHEMICAL ASPECTS OF MOLTEN-SALT REACTOR SAFETY: (1) DISSOLUTION OF COOLANT AND FUEL MIXTURES IN H-O, (2) A PORTION OF THE SYSTEM LiF-BeFo-Ho0 AT 25, 60 AND NEAR 100°C Ruth Slusher, H. F. McDuffie, and W. L. Marshall Abstract In connection with safety aspects of the ORNL Molten-Salt Reactor Program, the solubilities of MSRE fuel and coolsnt were determined in Ho0 solution at” 259C and at higher temperatures. In a separate study, portions of the system LiF-BeFo-Ho0 were investigated et temperatures of 25, 60 and near 100°C. Under conditions of the experiments, the results showed that (1) from the MSRE fuel, uranium dissolved to the extent of at least 0.010 molal--probably due to oxidation of U(IV) to U(VI)--and (2) IiF and an unidentified salt or salts of ILiF and BeF, were found to exist in the system IiF-BeFp-HO0. i NOTICE This report contains patentable, preliminary, unverified, or erroneous information. For one or more of these reasons the author or issuing installation and responsible office have limited its distribution to Governmental agencies and their contractors as authorized by AEC Manual Chapter 3202-062. A formal report will be published at a later date when the data is complete enough to warrant publi- cation, NOTICE This document contains information of a preliminary nature and was prepared primarily for internal use at the Oak Ridge National Laboratory. It is subject to revision or correction and therefore does not represent a final report, The information is not to be abstracted, reprinted or otherwise given public dis- semination without the approval of the ORNL patent branch, Legal and Infor- mation Control Department. 94 " LEGAL NOTICE This report was prepared as an account of Government sponsored work. Neither the United States, nor the Commission, nor any person acting on behalf of the Commission: A. Makes ony warranty or representation, expressed or implied, with respect to the accuracy, completeness, or usefulness of the information contained in this report, or that the use of any information, apparatus, method, or process disclosed in this report may net infringe privately owned rights; or B. Assumes any liabilities with respect to the use of, or for damages resulting from the use of any information, apparatus, method, or process disclosed in this report, As used in the above, ''person acting on behalf of the Commission’ includes any employee or contractor of the Commission, or employee of such contractor, to the extent that such employee or contractor of the Commission, or employee of such contractor prepares, disseminates, or provides access to, any information pursuant to his employment or contract with the Commission, or his employment with such contractor. -3 1. INTRODUCTION Safety aspects of the ORNL Molten-Salt Reactor Program make it impor- tant to know the short- and long-term effects of a spill of molten reactor fuel or of reactor coolant into the water-sand mixture at the bottom of the containment shell. Since this shell is designed to withstand a maximum pressure of 5 atmospheres (approximstely equivalent to the vapor pressure of Hy0 at 150°C), the maximum temperature of interest, when considering long-term effects, would be 150°C. In this study, solubilities of reactor coolant (LizBeFy,) and fuel mixture (LiF-BeFp-ZrFy-ThF,-UF), T0-23-5-1-1 mole %) in water have been explored at 259C and at higher temperatures. In addition, investigations on the solubility of ILiF, and of a compound of LiF and BeF, of unspecified composition, in aqueous solutions varying from O to 50 wt % BeF» were carried out at 25, 60 and near 100°C. These latter studies are of further use in evaluating the behavior of molten- salt coolant in contact with water. 2. EXPERIMENTAL PROCEDURES Solid LigBeF) and MSRE (Molten-Selt Reactor Experiment) fuel mixture were obtained from the fluoride production facility of the Reactor Cremistry Division, ORNL.l The LijBeF) contained approximately 2 wt % excess IiF. Chemically pure LiF was obtained from Foote Mineral Company. A stock solution of concentrated BeF, was prepared by dissolving & weighed amount of BeFo solid, obtained from the Beryllium Corporation, in water soluticn. The mixture was refluxed at a little above 100°C for 24 hr in order to F. A. Doss, J. E. Eorgen and J. H. Shaffer, Reactor Chemistry Division Annusl Revort for Per. End. Jan. 31, 1962, ORNL-3262, » 27-30. e dissolve the BeFp. At lower temperatures the rate of dissolution was very slow. A radioactive tracer, Be-T7, was added to the stock solution, and portions of this solution were diluted with water to give a series of aqueous solutions of decreasing concentrations of BeFo. All solids were ground to fine powders (in a glove box for the beryllium-containing solids) and were added separately to flasks contain- ing water. In some experiments, LiF solid was added to flasks containing solutions of Bng in H2O. | The mixtures of MSRE fuel and of coolant were stirred at room temper- ature and at controlled temperatures up to 90°C. Separate mixtures of LiF and of LigBeF} in contact with BeFp solutions were rocked at controlied temperatures of 250 % 0.2° and 60° % 0.3°C and were refluxed at tempera- - tfires a little over 100°C. The latter temperatures were those at which the solutions bhoiled at atmospheric pressure. Samples of the solution phases were obtained ai%er:periods of time varying from 4 hours to 28 days. The concentrations of lithium fiere determined by flame photometry, and fluoride by pyrohydrolysis and sub- sequent acid-base titration of the distillate.? Zirconium, uranium, thorium, and beryllium were anaiyzed spectrophotometrically by the pyro- catechol violet metfiod, thiocyanate method, thoron procedure, anfi the differential p-nitrdbenzeneazp-orcinol method, respectively. Beryllium was determined also by counting of radioactive Be-T7 and compariéon of the number of counts with those from an aliquot portion of a standard solution containing Be-7. Selected solid phases were separated fram the gAll chemical analyses were performed by the Analytical Chemistry Division, ORNL. . _5- solution phases and dried between sheets of filter paper. These solids were examined by means of a petrographic micr03cope; LiF was identified through its x-ray diffraction pattern.3 3. DISSOLUTION OF LigBeF, in H20 The concentrations of 1i, Be, and F found in solution, when excess LijBeF, solid was mixed with H,0 &t 259C, are given in Fig. 1 as a func- tion of time. Based on the data for lithium and beryllium, it appeared that equilibrium was attained at least within six days and perhaps sooner. The changes in the compositions of the solutions (re#ealing a higher ratio of beryllium to lithium than that in the o:iginal solid) require the appearance of some solid which is richer in lithium than the starting material and fihich is presfimably IiF. The data suggest that an invariant point may have been established. DNevertheless, these results are in contradiétion to the solubilities of LiF and of LipBeFp in BeFp-Hp0 solu- tions given in the table and in Fig. 5. It is possible thgt, although equilibrium appeared to have been attained, a relatively inert coating of a new solid on the surface of the LipBeF, solid may have formed and prevented‘further'dissolution of Li,BeF,. | The concentrations of Li, Be, and F found in solution are given in Fig. 2 as a function of temperature. Included in Fig. 2 are some experi=- mental values by F. H. PerfECt4 which were ofitained Ey analyses of liquid phases after approximately 24 hours of mixing with solid. Perfect 3C. F. Weaver of the Reactor Chemistry Division, ORNL,. contrlbuted to this part of the study. 4F. H. Perfect, Proc. Penn. Acad. Sci. 26, 54 (1952). N © O ~ o000 — (moles/1000 g of SOLUTION) QO N SOLUTION CONCENTRATION O UNCLASSIFIED ORNL-LR-DWG 66933 . FI:UORIDE L e o { e (?) ! — — . BERYLLIUM . e LITHIUM ———— 0 5 {0 {5 20 TIME (days) Tig. 1. Effect of Time on Dissolution of LiaBth in HEO at 25°C. 25 —9— 7= Portions of System LiF-BeFp-H,0 at 25°, 60° ¢ and Temperatures of Boiling (at 1 atmosphere) dn Tdentified MWiXing pop. 1ip Identified ime®* D°F2 LAF Solid Time** 2 Solid (hr) (wt %) (vt %) Phases (hr) (wt' %) (wt %) Phases Temperature: 25°C, 600 5.05 1.13 Starting Materials: 600 9.50 2.07 BeF-H,0 Solutions 600 14.38 3.01 + IiF Solid 600 18.81 4,22 600 23.27 5.63 264 5.05 0.722 a, c* 600 26.88 6.03 264 9.67 1.41 \ 600 25.62 4,23 264 14.55 2.08 600 29.93 4,31 264 19.10 2.80 600 35.26 4,48 264 23,56 3.58 264 28.23 4,77 a, ¢ 672 4. 9% 1.10 a 264 32.42 5.73 a, ¢ 672 3.49 2.05 a 264 36,93 6,91 a, ¢ 672 14,32 2.93 a 264 40,93 6.61 a, b, ¢ 672 18.75 4,03 a 672 23,26 5.28 a, ¢ 360 4. 92 0.799 672 26,20 4,63 a, ¢ 360 9.70 1.49 672 24. 87 3.65 a, c 360 14,75 2.23 672 28.97 3.71 ¢ 360 18.95 2.9% 672 34,73 4,10 c 360 23.71 3.86 360 27.76 5.2 Temperature: 60°C, 360 32.29 6.41 Starting Materials: 360 36.22 6.65 BeF,-H,0 Solutions 360 39.70 6.26 + LIF Solid 504 4. 96 0. 811 4 5.03 1.13 504, 2.71 1.47 4 9.69 1.97 504 14.35 2.28 4 14.49 2. 96 504 19.01 3.04 4 18.9% 3.85 504 24,00 3.86 4 28.14 6.38 504 27.92 5.34 4 31.03 5.99 504 32.18 6.34 b 33.28 5.49 504 34.43 5.45 4 37.50 4 .90 504 37.82 5.10 % Key: & = LiF, Identified by petrography b = LiF, Identified by x-ray pattern ¢ = birefringent solid, Identified by petrography % - Cumulative time. B ounu Mixin ] Tdentified Mixin BeF Identified I § Bng IiF Solid T3 & > IiF Solid (hr) (wt %) (wt %)_ Phases (hr) (wt %) (wt %) Phases (continued) Temperature: Boiling, Temperature: 60°c, Starting Materials: Starting Materisls: BeF5-H50 Solutions Ber—H O Solutions * LisBeF, Solid 2 + IAF Solid 2 38.9% 6.67 27 4,98 1.04 27 2.64 2.01 60 42.07 6.79 27 14.25 2.92 27 18.62 4,10 84 42.15 7.02 27 _23.27 5.59 27 27.83 6.36 108 43,61 7.48 27 25.90 4.63 27 30.31 4.75 132 43.43 7.07 27 36.16 4,84 Temperature: 60°C, Temperature: Boiling, Starting Materials: Starting Materials: BeFo-Ho0 Solutions BeFo-H20 Solutions + LioBeF, Solid + LiF Solid 24 23,17 3.97 24 22,56 4.81 24 28.39 4.22 24 32.69 5.83 24 31.68 4. 54 24 37.65 6.44 24 37.40 4.70 24 45,75 7.42 24 42,24 5.02 48 22.69 4.88 48 22.68 3.86 48 33.36 6.06 “d 27.81 4,08 48 37.98 6.85 48 33.09 4. 34 48 49.74 7.89 48 38.29 4,60 48 42,98 4,83 Temperature: Boiling, Starting Materials: Hy0 + ILipBeF, Solid 2 2.01 1.15 48 2.18 1.18 * Cumulstive time. 3.0 2.0 moles /1000 g of SOLUTION o D moles/1000 g of SOLUTION o N 0 Fig. 2. Effect of Temperature on Dissolution of LiaBth in HEO. UNCLASSIFIED ORNL—LR—-DWG 66934 A [ | | l FLUORIDE PERFECT, PROC. PENN. ACAD. SCI. y 26, 54 (1952) ' I - -.-..--.........l = .f —hmmmnd | "'#"--... ‘ === ---"'---.,__ ' = e THESE DATA—" A - Be AI\IJD Li e Lo ___,__r____g__.._-.&____ ® Be ' A& Be (PERFECT’'S DATA) o Lj A 20 30 40 50 60 70 80 a0 TEMPERATURE (°C) {00 -10- commented that the results were not entirely satisfactory and may have been complicated by the appearance of two separate solubility curvege-- one for a hydrated salt LizBeF4-xH20 and one for an anhydrous salt. In a8 further comment, with reference to a patent,5 it was felt that the anhydrous salt either dissolved very slowly in cold weter, hed a low solubility, or had both a low rate of dissolution and low solubility. In our own experiments, mixtures of solution and LigBeF,, solid were equi- librated 4 hours to 3 days before taking samples of the solution phases for analyses. Also included are the data obtained at 25°¢ (from Fig. 1). 4. DISSOLUTTION OF MSRE FUEL MIXTURE The analytical results from the run with fuel mixture at 25°C as a function of time are shown in Fig. 3. As with the reactor coolant, equi- librium appeared to be attained within six dasys. Nevertheless, a consistent increase in concentration of lithium and uranium was noted. In this experiment it was presumed that tetravalent uranium from the solid phases had been converted to the hexavalent state in the solution phase6 by the action of oxygen from the air, and also that an inert coating may have hindered- further dissolution of the solid phase. In Fig. 4 are shown enalytical results fof solution concentrations of U, Ii, Th, Zr, and Be as a function of temperature. The time of equi- libration at each temperaiure before sampling was one day. Also included r~ - , ¢ is one value for uranium and one for lithium obtained previously. The 5H. C. Kawecki, U.S. Patent No. 2,490, 633 (to the Beryllium Corpora- tion), Dec. 6, 1949. 6H. C. Nikolaef and Yu. A. Luk'yanchef, Atomnaye Energ. 11 67 (1961). 7R. F. Apple, Analytical Chemistry Division, ORNL (1961). wll- - UNCLASSIFIED ORNL-LR-DWG 66935R 02 I f Be : l ¢ ® 0 f-_ S 2 oo L 0 0.08 T Zr i l ° 0.06 |- ) e & 004 I pa! - 0.004 O ® o 9 . Q 0.002 b ] g D 0 g 045 | - Li | l 0.35 e ? e 0.25 ] 0.004 Y _ o € — — ¢ ® 0.002 - 0 | . 0 { 2 3 4 5 6 7 8 9 10 TIME (days) Fig, 3. Effect of Time on Dissolution of MSRE Solid Fuel in H,0 at 25°C. -]12= UNCLASSIFIED ORNL~LR-DWG 66936R 0.3 | ll Be l 0.2 l - . T T — | ' el ————‘———,-———-_-—— 0.20 — J - - l ' Zr “ 0.16 - t/}/// ;/’// 0.12 w-fi";;74(’ ',/”; .0 / 0.08 -§"“/‘— & 5 0.04 3 1 l 5 0008 Th —— S <~ 3 O ——-——‘_J——/ 8 0004 “T—-—"-":—!———_—-_’ e et e e o g 5 e O T £ ' Li - ¢ ® - : / 0.5 . fi/ 0‘4 o K | B —e— | APPLE'S DATUM 0.3 1 | | 0012 _; - ; - l ——? U . / 0.008 _ ¢ / 0.004 b e L b * APP|LE'S DL}TUM 0 20 30 40 50 60 70 80 90 100 TEMPERATURE (°C) Fig. 4. Effect of Temperature on Dissolution of MSRE Solid Fuel in HEO. -13- analytical results from samples taken upon stepwise lowering of the tem- perature of the solution-solid mixture consistently gave higher values for the solution concéntrafions of the various components., It is believed that equilibrium either was not reached on cooling or had never been reached; In'view of the appreciable uranium concentration found in solution under these conditions, it has been recommended that neutron poisons be present in any water which could mix with the fuel in the event of a reactor accident. 5. A PORTION OF THE SYSTEM LiF-BeFp-H,0 AT 25, 60 AND NEAR 100°C Compositions of liquid phases of BeFp and H,O which were rocked or refluxed at several temperatures in contact separately with LiF and with LigBeF4 are given in the table. The initial reagents and times of rock- ing or refluxing are specified; also, some designations of solid phases are given, In all cases a solidflor solids were present. When these data are plotted as the composition of IiF vs that of BeFy (Fig. 5) and con- sideration is given to the times of mixing and tempera£ure cycling, then there appears to be metastability of LiF solid phase in equilibrium with solutiong gontaining high concentrations of Ber- We believe that the continuous curves which are drawn on Fig. 5 represent stable equilibria- V'and the dashed curves show the solvbility of a metastable solid. Deta which'fall between these two curves represent in-progress changes bet- ween metastable and stable conditions. The only salt defin;tely identi- fied by the k—ray diffraction method was LiF. Another salt, proposed to be some compound of IiF and BeF,, was not identified by optical' =lli- UNCLASSIFIED ORNL-LR-DWG 76255 8 7 - - - G b o o b L ~4 o . e e e e e e B - ' [ R a ¢ MIXING ° ! : /( W& v TIME (hr) 6 booo b _1_%___ WL L x=2a _ 0 =48 E9 ®=2-132 2 w 4 | 3 MIXING TIME (hr) 3 e i e @ = § ] A =27 UNSATURATED x =24 2 “=== SOLUTION e ofe 0= 48 ] { F h,z._‘.._______.‘x.. - med e /x‘fyf e 0 0+ \,I\Q e 3 e e = 5\" . = UNSATURATED x 9 2 2+ x - — Q - - o ] n SOLUTION S S - ® - o |l A 0 . =1 ] 2 LIQUID ey - (BeFglm SOV MIXING 3 (LiFn L TIME (hr) | [ T x = 264 —_ o = 360 &° FOR 600 AND 672 hr ® = 504 ) SAMPLES, THE TEMPER- — A = 600 — w ATURE WAS RAISED TO s =672 5 60°C, AND THEN LOWERED ‘ | __UNSATURATED _ TO 25°C FOR THE RUN | | SOLUTION - i | l T(°C)=25 | | , [ ] O i . i 0 5 10 15 20 25 30 35 40 45 50 BeFa (wt To) Fig. 5. Some Solubility Behavior in the System LiF-BeF -H 20, 25,100°C., 2 ~-15- petrography or x-ray diffraction. Since a solid which may have been present, other than LiF, could be formed only from LiF and BeF2-Ho0 solu- tion, it is possible that LisBeF,, in an amorphous, unidentifisble form, was present. By means of optical petrography, birefringent refraction lines were observed for the unknown solid.3 Similar lines are observed for Li,BeF, solid. A conventional, three-component phase diagram of a portion of the condensed system at 25, 60'and 1000C+ is shown in Flig. 6. The data are omitted; the curves are drawn to represent the solubilities for the stafiie solids to the continuous curves shown in Fig. 5. -16- UNCLASSIFIED ORNL-LR-DWG 76254 H,0 ISQTHERMAL INVARIANT POINTS Q . o~ \ \}db'(’ & Ve < S S w 9 COMPOUND OF \ LiF + BeF, PLUS LIQUID \ ”/ // \ SOLUBILITY AT 25°C \ OF BeF, IN H,0 P / P ~ rd -~ - / / T vie 2 \ N \/ \ \/ \ \ \/ BeF Fig. 6. Representation of a Portion of the System LiF-BeFE-Hao at 25,60, and Near 100°C. 30. 32-33. 3438, 39. 40. 41-55., -17 1 INTERNAL DISTRIBUTION MSRP Director's Qffice C. F. Baes S. E. Beall ¥. F. Blankenship E. G. Bohimann J. C. Griess W. R. Grimes R. B. Lindauer H. G. MacPherson W. L. Marshall W. B. McDonald H. F. McDuffie R. L. Moore D. Scott C. H. Secoy J. H. Shaffer M. J. Skinner Ruth Slusher I. Spiewak A. Taboada J. R. Tallackson R. E. Thoma C. F. Weaver Central Research Library ILaboratory Records Laboratory Records ORNL RC Y-12 Technical Library, Document Reference Section DTIE, AEC Division of Research and Development, ORO