MASTER ORNL-4415 UC-80 — Reactor Technology LIQUID-VAPOR EQUILIBRIA IN LiF-BeF2 AND LiF-Ber-ThF4 SYSTEMS F. J. Smith L. M. Ferris C. T. Thompson OAK RIDGE NATIONAL LABORATORY operated by UNION CARBIDE CORPORATION for the U.S. ATOMIC ENERGY COMMISSION DISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. DISCLAIMER Portions of this document may be illegible in electronic image products. Images are produced from the best available original document. ORNL-4415 Contract No. W=7405-eng-26 CHEMICAL TECHNOLOGY DIVISION Chemical Development Section B LIQUID-VAPOR EQUILIBRIA IN LiF--BeF2 AND LiF-~-BeF2--ThF4 SYSTEMS F. J. Smith L. M. Ferris C. T. Thompson LEGAL NOTICE This report was prepared as an account of Government sponsored werk. Neither the United States, nor the Commission, nor any person acting on behalf of the Commission: A. Makes any warranty or representation, expressed or implied, with respect to the acou- racy, 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 not 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®! inciudes any em- ployee 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. JUNE 1969 OAK RIDGE NATIONAL LABORATORY Qak Ridge, Tennessee operated by UNION CARBIDE CORPORATION for the U. S. ATOMIC ENERGY COMMISSION SLTRBUNON (4 1S GocuUM EMd B umtismy CONTENTS Page N 2 e =2 A ] I. Infroduchon . .. v i it i e e e e e e 1 2. Experimental . . .. .. e e 2 3. Results « o o v v i i i e e i e e i e e 6 3.1 Systems of Interest in Processing Two=Fluid MSBR Fuel . . ... .. .. .. 6 3.2 Systems of Interest in Processing Single~Fluid MSBR Fuels . ... ... .. 11 4, Conclusions . v v v v it it e e e e e e e e e e e 14 5. References-o-tao-nta---o..-o-w.ov.o.ucloouooo-oec-- ]5 LIQUID-VAPOR EQUILIBRIA IN LiF-BeF, AND LiF-Bef, -ThF, SYSTEMS F. J. Smith, L. M. Ferris, and C. T. Thompson ABSTRACT Liquid-vapor equilibrium data for several LiF-BeFs and LiF-BeFo- ThF, systems were obtained by the transpiration method over the tem- perature range of 900 to 1050°C. Relative volatilities, effective activity coefficients, and apparent partial pressures are tabulated for the maojor components, as well os for solutes such as UF4, ZrFy, CsF, RbF, and some rare-earth fluorides. The values are in reasonable a- greement with those reported in the literature. ~ Results of this study show that distillation may not be feasible as a primary separations method in the processing of single=fluid MSBR fuels. 1. INTRODUCTION To be an efficient breeder, a molten-salt reactor must be close-coupled to o chemical processing facility to provide for the continuous removal of protactinium, fission products, and corrosion products from the system. The initial molten-salt breeder reactor (MSBR) con'::ep’i“s-l'2 were based on the use of two fluids: a fuel salt composed of LiF-—BeF2 (66~34 mole %) containing about 0.3 mole % UF4, and a blanket salt having the approximate composition LiF-Ber-ThF4 (73-2-25 mole %). Recenfly,3 however, emphasis has been centered on a single-fluid MSBR that would utilize a salt such as LiF—BeFZ—ThF4-UF4 (72-16-12~0.3 mole %). Considerable effort was expended on the development of o fluorination-distillation mefhod4"7 for the processing of the fuel salt from a two-fluid MSBR. Fluorination wos selected as the method for removing the uranium from the salt as UFé, and distillation was proposed as the means for separating the rare-earth fission products from the bulk of the LiF- BeF2 carrier sc;lh Results of batch distillotion experiments by Kelly8 and experiments by Scott’ in asimple closed vessel with a "cold finger” to collect the vapor sample indicated that the rare-earth separation factors were about 100, . More recent experiments by Cantor, 10 who used the transpiration method, and by | nghfower cmd McNeese,” who Qsed an equahbrium shll demonsfrated fhcf.dls— D . - h!lahon is possnble and reporfed rare eqri'h sepamhon ‘Facfors of about 1000 Prior o to the presenf srudy, no exper:menfs were conduci‘ed w1fh LsF BeFQ-ThF4 sys*rems, B | '__hence, the apphcabth%y of d:shilcflon to the processmg of smgle-fluad MSBR ‘Fue!s - i Tcould not be properly assessed This reporf summcrlzes i'he results of experlmen?s in wh!ch fhe fransplroflon o ___method of obmmmg hqu:d vapor equallbmum da!‘c wcis Used in the temperai'ure mnge B R of 900 to IO50°C " These experiments had- i"hree oblechves (1) to corroborofe ddfa obtamed by fhe equ:hbrlum still techmque wnth Two-fiuud MSBR fuel salt, (2) to % 'cletermme reiaflve voichli’r;es of o’rher componenfs of mferesi" in fwo-flusd MSBR | processmg, and (3) i'o cbi-am suffucnen’r dcfa on LlF“BeF ThF4 sysfems fo a!low a "'3”___prel:mmary evaluahon of fhe GppIICCIblllfy of dtshllchon in fhe processmg of smgle~ = i ffiu.d MSBR 'Fuei Acknowiedgmenfs - The cuthrs cre mdebfed to i‘he Followmg members of i'he 'ORNL Ancrlyhcol Chemistry Dev:s:on fhe group of W. R Lamg for the color!mefr:c cnclyses For thor:um and uramum, Mcrlon Ferguson for fhe Flome—phofomei'rlc analyses | for |zthium and other alkali mei-qls, and C. A, Pritchard for the emlssmn-speci'rogrc:phlc ".onalyses for berylhum, %horaum, rare earfhs, and z:rcomum - Bulk quanhhes of .'-_LIF BeF2 and LJF BeF2 ThF of vorymg composmons were provnded by the group yof - J. H. ShQFFer of the ORNL Recci'or Chemlsfry Dw:snon We fhank J. F Land and c. E Schlilmg for further purlfymg i‘he smaH bofches oF salt used in i'he mdawducl - experimeflts 2. EXPERIMENTAL - :lh'using'%h'e 'ffchspiré%ién"-method WIfh molten sdlfs, dfi inerf '(c':.orrier) .'gcxts ‘i's' | -_pcsssed over a moi‘ren salt (becommg satumfed wsi‘h the vapor in equzi brlum wnth it), = fhrough a condenser where the saH' vapors are deposnfed and col!ected omd fmcslly, : fhrough a Wet Tesi' Mefer where the tofal voiume of inert gas usecl is defermn ned : -_'_'Afi*er th_e_vcxpo-rs have tr_qns_p:re_d for a .known.:per;od;.of.-_tame_ct a g;yen_fe_:mperq’r_u_re, . | the condenser is removed and the salt contained within is dissolved. Analyses of the solution, along with the pressure of the system and the volume of inert gas used, provide the information necessary for calculating apparent partial pressures of the components of the system. The transpiration apparatus, shown schematically in Fig. 1, closely resembles that used by Sense et al. 2 and Cantor. 13 The basic components consisted of a 36~in.-long alumina tube contained in a 1é-in.-long Marshall furnace. A nickel [iner was placed inside the alumina tube to protect the alumina from corrosion by the fluoride vapors and to help "flatten" the temperature profile. The temperature profile of the Marshall fumace was adjusted by the use of shunis until the hottest region of the furnace was located exactly in the center and the maximum temperature variation (at 1000°C) over the length of the nickel boat (used to contain the salt sample) was 5°C. The furnace temperature was conirolled by a Wheelco "Capacitrol” time- proportional controller and a Chromel-Alumel thermocouple. The temperatures of the melt and vapor were measured by means of Chromel-Alumel thermocouples and a Brown recorder. Salt samples (about 100 g) of the desired composition were initially treated, in graphite containers, with HF- H2 mixtures at 850 to 900°C to remove oxide im- purities; residual HF and H2 were stripped from the salt with high-purity argon. After being cooled to room temperafure, each salt ingot was transferred (under argon) to the nickel boat, which was placed in the center of the Marshall furnace. The transpiration apparatus was heated (with argon flowing slowly) to the desired tem- perature. Then a condenser was inserted into the system, and iranspired vapors were collected over a predetermined length of time. Each condenser (made of 1/4-in.-diam nickel tubing) had a 1/32-in.~diam hole in the end that was in contact with the vapor phase above the salt sample. The carrier gas was high=purity argon that had been further purified by passage through a Molecular Sieve trap to remove water and through a heated (450°C) trap filled with metallic copper to remove oxygen. Removal and replacement of the condensers could be accomplished while the system remained at temperature; thus duplicate NICKEL HEAT SHIELDS HIGH~-TEMPERATURE ALUMINA TUBE (36 in. LONG) Wiz MAF\‘SHALL FURNACE (16in. LONG) ORNL-DWG 68— 2181 NIGKEL | HEAT SHIELDS § - 5 ARGON INLET = THERMOCOUPLE FOR VAPOR TEMPERATURE THERMOCOUPLE FOR © SALT TEMPERATURE —== 12 | L [ -——-——b. ARGON TO WET TEST METER N CONDENSER z oy . _ N, [~ NICKEL LINER (18 in. LONG)/ Systems. \ NICKEL BOAT “(5in. LONG) Fig. 1. Cross Section of Transpiration Apparatus Used to Determine Relative Volatilities in Molten Salt 5 samples at a given fempercffire and/or a series of samples at different temperatures could be obtained using a single batch of salt. After a condenser was removed, its exterior was polished to remove surface contamination. The condenser waos then cut into sections, and the salt contained within was recovered by leaching the sections with T N H2504. Aliquots of the leachate were submitted for the desired analyses. Apparent partial pressures were calculated from the following expression: N, P PA N+Né o N +M 7 A B T n where PA = the apparent partial pressure of species A, P = the total pressure of the vaporized salt and carrier gos, NA = total moles of species A collected in the condenser, and M = total moles of carrier gas passed through the sysiem. This expression was derived by assuming that the behavior of each gos wos ideal and that Dalton's law of partial pressures wos applicable. The franspiration method gives no direct information about the molecular for- mulas of the vapor species or about the total vapor pressure of the system. Therefore, it was assumed that each species existed as the monomer in the vapor phase. In using this method, the gas flow rate must be carefully controlled. If it is too high (i.e., greater than the rate at which evaporation occurs at the liquid surface), the carrier gas will not become saturated with vapor and the measured value of the vapor pressure will be low. [f it is too low, thermal diffusion effects in the vapor phase will make the calculated value of P, too large. For the experimental ap- paratus described above, the measured vapAér pressure of a typical salt was found to be independent of the argon flow rate in the range of 15 to 50 cc (STP)/min. There- fore, no correction was needed for diffusion or kinetic effects. Under the conditions used, no change in the composition of the liquid phase was detected during the course of an experiment. 3. RESULTS 3 1 Sysi'ems of lnferesf in Processmg Two Fluad MSBR Fuel Doi‘o ob‘romed for LIF BeFZ oncl LIF Ber—metol fluorade sysfems are given in Toble 1. In the absence oF omy mformohon regordmg compiex molecu!es in fhe | 'fvopor phose, the porha! pressures of LiF, BeF o ond soiute fluorades were colculai‘ed N by ossummg ihof on!y monomers exnsi'ed m the vopor In eoch experu menf, fhe o | opporenf portlol pressures, P, ; -rog-e*-f(mm '_o‘f_,H_g) - % _b/T(‘?K)_i ;o | _".m whlch o ond b were. constonfs over fhe %'empero'l'ure rcmge mveshgafed 900 to . e = -1050°C Typlcoi piofs of log F’ vs 1/T are shown in Fugs 2 ond 3 | cher workers have expressed fhear vopor-!zqu:d equ:hbr;um doi’o in ferms of relohve voloh!:‘ry, whlch is defmed by . yA/yB .where a,, is the reloflve voloh[ify of componenf A wath respect to. componen’r B AB Ly is fhe mole frocflon of the desngnoi'ed componenf in fhe vopor phase, and x is the .mole Frochon in the quund phose The relohve volohlmes of BeF (wuth respec'r to | _'_LlF) obfomed in our experlmenis with LiF- BeF bmc:ry sysfems ore in reosonoble - F ogreemen? with i'hose repori‘ed by Ccnfor,]q_-]_ For example, :Con‘!'or obi'omed voiues of 4. 28 for LnF BeF (85~ -15 mole %) at 'iOOO"C who olso used the fronspzmhon me’rhod | _--ond 3. 75 for L:F- BeF (90*]0 mole %), the corresponding vaiues From the present | 3 si‘udy were obouf 3. 8 ond 3. 77 (Toble 'E) Our volue obfomed wa%h LsF BeF (90- 10 : mole %) is somewhot lower fhon fhe overoge vo!ue of 4 71 reporfed by Highfower and Mc:Neese,,H who used on equnllbrlum shH me'i‘hod onc! is higher fhon our volues _obi'olned when fhe sali' confoanecl smoli amounfs of RbF CsF Z;r‘F‘4 (Tob!e 1) Thls 'scofl'er in vo!ues is not surprfsmg, however, becouse smoli var:oflons in the composmon | fof the quUId ond/or vapor couse Iorge chcmges in fhe reiohve voio’ralfiy volue For | ) could be descrlbed odequofely by fhe imeor expressmn e Table 1. Apparent Portial Pressures, Relative Volatilities, and Effective Activity Coefficients in LiF=BeF ,~Metal Fluoride Systems 2 Apparent Partial Pressure, * log P (mm) = . .. . ‘e Effective Activity Relative Volatility 0, - [+] I Salt Composition (mole %) a = b/T (°K) Coefficient at With Respect fo LiF, LiF BeFs Third Component Species a b 100C°C af 1000°C 86 14 LiF 8.497 11,055 1.60 BeF,) 7.983 10,665 4.42 % 1072 3.82 90 10 Lif 7.604 10,070 1.30 BeF, 8707 11,884 3.55 x 1072 3.77 95 5 LiF 8.804 11,505 1.30 BeF, 11510 15,303 4.33x 1072 4.60 90 10 UF,: 0.02 LiF 9.481 12,386 1.33 BeF 9.339 12,411 596 x 1072 6.19 UF, 4.361 12,481 7.36x 1073 2.9 x 1072 89.6 9.9 UE,: 0.5 LiF 8.384 10,987 1.34 BeF, 7.421 10,112 4.65x 1072 478 UF, 6.686 13,443 1.09 x 1072 4.2x 1072 86.4 9.6 UF,: 4.0 LiF 10,790 13,992 1.55 BeF, 10.177 13,726 3.84x 1072 3.42 UF, 10272 16,786 1.25x 1072 4.2 x 1072 90 10 RbE: 0.09 LiF 8.286 10,811 1.47 BeF, 6596 10,552 3.11x 1072 2.93 RbF 5.187 8,907 2.19 24.7 89.9 10 CsF: 0.03 LiF 0.654 13,459 1.99 BeF, 8310 11,313 4.07 x 1072 2.82 CsF 0.819 3,375 1.17 95.1 90 10 ZrFy: 0.083 LiF 7.915 10,358 1.41 BeF, 7.167 10,070 2.83x 1072 2.77 ZiF, 13.095 20,382 3.05 x 1074 2.19 *Temperature range: 900 to 1050°C. It wos assumed that LiF, BeFZ, and the solute fluorides existed only as monomers in the vapor. APPARENT PARTIAL PRESSURE (mm Hg) oo 1 ORNL—~DWG 68-9482 10 _ ? O G, 107 e g —~ 4 40_4 4 — \fiw \o“a.h S : . _ | .'fi A.,,_ I 4072 T~ (- 0 \ \ ) 0 \!.__‘ 0 D ~~—g 1073 \b\ o \ \f: o LiF, Zrf, EXPT 6 ® LiF, RbF EXPT \ A BeF,, ZrF, EXPT N 4 BeF,, RbF EXPT O ZrF, { VG5 f RbF 7.6 7.8 8.0 8.2 8.4 8.6 4o,ooo/r(°K) Fig. 2. Apparent Partial Pressure-Temperature Curves for the Sysfems LiF-BeFy-RbF (90-10.0-0.09 mole %) and LiF-~BeFy-ZrF, (90-10.0-0.083 mole %). . ORNL-DWG 68-9483 TEMPERATURE (°C) 1050 1000 950 900 To} [ | | | | e LiF o 4 BeF2 h ® UF Q‘ \ T \\ £ A A \‘ £ o' ™~ g \A' \g g \ Ll .~ o y Y & 2 éf’ 10 e N g \g = ™ &, -3 \\ < 10 N a < \ \ I\ 6% \\ NS Toke 7.6 7.8 8.0 8.2 8.4 8.6 10,000/ o0+ Fig. 3. Apparent Partial Pressure=Temperature Curves for the System LiF-BeF,-UF 2 4 (86.4-9.6-4.0 mole %). excmple, it hcrs been repori'ed thcf LrF—BeF (66—34 mole %) is rhe vcpor in. " | equrhbrrum wrrh LIF BeF (90 'IO mole %) ar 'EOOO"C Thrs gsves a vaiue for rhe | | relotrve vo!cti'lhfy of BeF2 34/66 o S - g Anofher source has repor'red i-hc:i- fhe composmon oF fhe vapor in equ:i brrum wrrh o LlFr.-.BeF (88—-12 mole %) is LaF BeF (67-—33 rnole %), correspondrng i-o 2788 B Our pcrrhal pressure dam for LIF BeF2 sysi'ems are rncompcmble w;rh seme oF '. ; _fhe fotal pressure c!c:te presenred by Canror 1_3 He has reporfed rhe rorcl pressure . of LiF- -BeF, (90-10 mole %) to be 1. 8 mm Hg ot 1000°c, For the same sysi'em at i 'IOO‘G"C we obrcmed the qpproxrmcsre vcriues P..=0. 55 cnd P, e 0.23 mm Hg, s LiET BeF correspondmg to o roml pressure of 0.78 mm Hg (assummg fhaf no drssoc:rcmon or . association occurred in rhe vqpor phose) The rorai pressure colculcrred from our _. rrcnsplmhon dcri'cs should hove been h:gher rhan the actual rofql pressure because .essocsohon in rhe vapor phase undoubted!y occurs. Association in the vcapors obove pure LiF has been nored 5 “and compiexarron has been observed (by mass specrro- 'merry) in i'he vcpors cbove LIF BeF2 solutrons 1e 3 'Effechye achv_r ry ceeffic_sen_t_s, YA’ were caiculefe_d for each c'oriz:pdn'enr_ of the - 'LiFf BeFé's_ysrems (Table 1). The quiyiry”co_e‘ffic.ieni' for .c_ompenehr:_A“i_s given by: Where X, is i-he mole Fracfron oF A in i'he solu’non, A A : sure of A, and P is rhe vapor pressure of pure A. The ccrrv:ry coeffrcrenrs ob’ramed_ - §or BeF are in good ogreemenr w;rh rhose reporfed by Keiiy,,8 who used drsta”chon | 11 dafa cnd crssumed rhe cscr:vsfy for LrF to be umi'y Hugh’rower and McNeese _. nored rhqr fhe re!crhve ve!ohhhes obrqrned experamenfa”y for severe! rare earirhs were P is rhe eppcrenf pcarhol pres- 11 very close to those calculated by assuming ideal solution behavior (Raoult's law; Y = 1). The resulis of the study presented in this report show that RbF and CsF also behave almost ideally; their activity coefficients are near unity (Table 1). Uranium tetrafluoride and ZrF4, on the other hand, do not behave ideally in solution; activity 2 coefficients for these solutes were only 10 to 10 (Table 1). The vapor pressures, at 1000°C, of the pure fluorides of interest are given in the following table: Vapor Pressure af 1000°C Component (mm Hg) Reference LiF 0.47 17 BeF2 é5. 18 ZrFy 4770 19 UF,, 2.4 20 RbF 7.8 17 CsF 76 17 ThF4 0.0668 21 3.2 Systems of Interest in Processing Single-Fluid MSBR Fuels Liquid-vapor equilibrium studies of several L'i'F“-Ber-'ThF‘4 systems have been made to determine the feasibility of using certain distillation steps in the processing of single-fluid MSBR fuels. The data are summarized in Table 2. A typical partial- pressure=-temperature plot is shown in Fig. 4. The partial pressures and the predicted total pressures were calculated assuming that only monomers existed in the vapor. Corrections for association in the vapor (known to occur in the vapor above pure LiF and F.iF--BeF2 systems) would cause both the calculated partial pressures and the predicted total pressures to be lower. In addition to the systems shown in Table 2, a limited amount of data was ob- tained with LiF-Ber-ThF4 LiF~BeF2—ThF -Lch3 (36.6-1.0-59.6-2.8 mole %) gave the following relative -solute fluoride systems. Results obtained for the system 4 12 Table 2. Apparent Partial Pressures, Relative Volatilities, and Effective Activity Coefficients in LiF- Ber-ThF4 Systems Predicred Apparent Effective Total Salt Composition Vapor Composition at Partial Pressure e . " {mole %) 1000°C {mole %) ' log P{mm) = A - B/T Activity Relative Pressure : g Coefficient Volafility ot 1000°C LiF__ BeFp ThFy LIF BeFp ThFy Species A B ot 1000°C ot 1000°C (mm Hg) 468 20_ 12 29 71 0.07 LiF 7.806 © 10,070 - 2.44 - 2.7 BeF 9.194 11,349 0.146 8.27 ThF c c ~0.25 ~0.014 70.5 7.5 22 36.7 631 0.2 LiF 8.510 11,352 1.19 - 1.1 BeF, 7801 - 10,112 . 0.4 16.2 ThF4 4,360 8,935 0.15 0.018 75.4 3.{) 21 43.2 55.6 _ 1.1 LiF 8.548 10,112 0.98 - 0.81 | o BeF, 7.480 9,984 0.19 27.1 ThF4 2.879 6,233 0.61 0.088 53.5 1.5 45 i6.5 815 2.1 LiF 8,446 12,285 0.25 - 0.38 BeFy d d ~032 ~177 ThF4 10.575 16,1446 0.27 0.15 45 0.06 55 75.1 12 12.7 LiF 8.611 11,826 0.23 - 0.06 BeFs d d ~0.20 ~120 ThF4 10.314 16,459 0.23 0.14 34 . 1.0 65 9.9 85.2 4.8 LiF 10.314 12,129 0.13 - 0.21 BeF, d d ~028 ~293 ThF4 11.539 17,232 - 0.24 0.26 GTempercfure range: 950 to 1050°C. It was assumed that no association occurred in the vapor. Calculated on the assumption that no association occurred in the vapor. Association, which undoubtedly occurs, would make the actual total pressure less than the value predicted here. : “The scatter in data points was too great for determination of these values. d'fl"\e BeF, concentrafion in the liquid phase decreased too rapidly to allow determination of these values, APPARENT PARTIAL PRESSURE (mm Hg) 13 ORNL-DWG 689184 TEMPERATURE (°C) q {050 1000 950 O LiF A BeF, FA \\:\\ — S Toka Q..\ O .\D\\D 1073 O O g 76 7.8 8.0 8.2 8.4 10,000/, Fig. 4. Apparent Partial Pressure-Temperature Curves for the System LiF--Ber-'ThF4 (70.5-7.5-22 mole %}. 14 ~volatilities (with respect to LiF) af 1000°C: Ber, 37; ThF ,, 0.25; and LaFg, 1.5x 10™°. Data for the system LiF-BeF, ~ThF ,~CsF-RbF (33.0-0.66-63.1-1.36~ L 98 mole %) yielded relative volahhhes of about 100, 0.65, 3 7, cnd 1.0 for BeF ThF4, CsF, and RbF, respec’rwely, at 1000°C. The tofcl pressure predicted ~ for fhis sysi‘em ot 1000°C is Iess than 0. 05 mm Hg In contrast to the observahon | made wsfh LIF BeF2 sysfems, fhe behcvmr of CsF and RbF was Far from :deal The o effechve achvfi'y coeff:cneni‘s 'For fhese fwo solutes were 3 X 10 cmd 8 X 10 3 respec’rwely This marked depari'ure from ndeahfy is probably due to complexahon of i'he alkoll—metal fluorldes wri-h ThF4 (Nofe that fhe ThF /LIF mole ratio in this salt was rather hlgh ) In anofher expenmeni' at 1000°C with LaF BeF ThF CsF-RbF (68—20-]2 -0.13- 0 08 mole %), a saii‘ havn ng a much lower ThF /L:F mole | ratio, both CsF and RbF behaved much more :deally, the effective activity coef- ficuenfs were 1.6 and- 17 respeci'svely The _c_orrespondl_ng relchve volatilities (w:i'h respect to LlF) were 107 and 119. Data from d run with LiF- BeF2 ThF4 EUF3 (42 4-0 06~ 51 8-5 8 mole %) ylelded a relahve volc:hhi'y of about 9 x 1073 for | EuF3 at 1000°C 4., CONCLUSIONS .Mecsuren;jents made with three different _LiF-__BeFQ solutions indicated that a melt having the appg’oximqi’e composii‘ion LEF—Ber (90-10 mole %) will, ot 1000°C, be ~in equilibri.um with vapor having the composition Li_F—BeF2 (66-34 mole %). The latter composition is that desired for the fuel salt for o two-fluid MSBR. The re- ' and most of the LiF and BeF_ from _ _ 4 7 T2 the fuel salt of a two-fluid MSBR, leaving fission products such as the rare earths sults of this study show that recovery of the UF in the still-pot bottoms, is not possible in a single-stage distillation system because the vo!diil.ii'y’ of the UF4'is too low. '-The fluorides of the fission products cesium, zsrcomum, and rubldzum have high relahve volatilities, cmd would therefore con- centrate in fhe distillate wui'h the LiF and BeF Aithough i'he relative volatilities 2 of the various componenfs are dlfferen? a comphcated mulhs’roge dsshilcmon system would be required to effect the desired separahons “Thus, these resuifs suppori' the 15 4 original conclusion™ that distillation is best applied to the processing of two-fluid MSBR fuel salt after the uranium has been removed by fluorination. The few results obtained with LEF—Ber-ThF4 systems showed that the volatilities of both the rare-earth fluorides and ThF4 are low, even at 1000°C. 1t is possible that the rare-earth-thorium separation required in the processing of single-fluid MSBR fuels could be achieved by distillation; however, the results of this work indicate that the temperature required to achieve adequate distillation rates would have to be at least 1200°C. Thus, determination of relative volatilities for the rare-earth fluorides and ThF4 at temperatures above 1000°C will be required in order to assess the feasibility of utilizing distillation in the processing of single-fluid MSBR fuels. 5. REFERENCES 1. J. A. Lane, H. G. MacPherson, and F. Maslan, eds. Fluid Fuel Reactors, pp. 567-697, Addison-Wesley, Reading, Mass., 1958. 2. P.R. Kasten ef al., Design Studies of 1000-Mw(e) Molten Salt Breeder Reactors, ORNL=-3996 (August 1966). 3. M. W. Rosenthal, MSR Program Semiann. Progr. Rept. Feb. 29, 1968, ORNL-4254 (August 1968). 4. C.D. Scott and W. L. Carter, Preliminary Design Study of a Continuous Fluorination-Vacuum Distillation System for Regenerating Fuel and Fertile Streams in a Molten Salt Breeder Reactor, ORNL=-3721 (January 1966). 5. D. E. Ferguson, Chem. Technol. Div. Ann. Progr. Rept., May 31, 1967, ORNL-4145 (October 1967). 6. D. E. Ferguson, Chem. Technol. Div. Ann. Progr. Rept., May 31, 1968, ORNL-4272 (September 1968). 7. L. E. McNeese, Considerations of Low Pressure Distillation and lts Application to Processing of Molten-Salt Breeder Reactor Fuels, ORNL-TM=-1730 (March 1967). 10. 1. 12. 13. 14, .]5. 16, 17. 18 19. 20. 21. 16 W. R. Grimes, Reactor Chem. Div. Ann. Progr. Rept. Dec. 31, 1965, ORNL-3913 {March 1966), p. 37. D. E. Ferguson, Chem. Technol. Div. Ann. Progr. Rept. May 31, 1965, ORNL-3830 (November 1965), p- 301 W. R. Gnmes, Reaci’or Chem Div. Ann. Progr Rept Dec. 31, 1966, ORNL-4076 (March ‘1967), p 26. | J- R. nghfower cnd L E. Mc:Neese, Measurement of the Reichve Voiahhhes of Fluorides of Ce, Lq, Pr, Nd Sm, ‘Eu, Ba, Sr, Y, cmd Zr m Mleures of LiF and BeF2 ORNL TM-~2058 (Jonucry 1968) | K. A. Sense, M. J. Snyder, and J. W. Slegg, J. Phys. Chem. 58, 223 (1954). W R. Gr'imes, ORNL 3913 op- cit. cfl' p. 24' R. B. Brsggs, MSR Progrcm Semlann Progr. Rept Feb 28, 1966, ORNL-393%6 (June 1966), p 128. R. S. Scheffee and J. L. Margrave, J. Chem. Phys. 31, 1682 (1959). W. R. Grimes, ORNL~-4076, op. cit., p. 27. D.R. Stull, Ind. Eng. Chem. 39, 517 (1947). _J H. Si’mons, Fluorine Chemisfiy, Vol. V, Academic, New York, 1964, p. 20. K. A. Sense M. J. Snyder, and R. B. Filbert, Jr,J Phys Chem. 58, 995 (1954). S. Langer and F. F. Blankenship, J. Inorg. Nucl. Chem. 14, 26 (1960). A. J. Damell anc!. F. J. Keneshea, Jr., chor Pressure of Thorilufh Tefmfluofide, 'NAA-SR-2710 (1958). ORNL-4415 UC-80 — Reactor Technology INTERNAL DISTRIBUTION 1. Biology Library 76. C. E. Larson 2~4. Central Research Library 77. J. J. Lawrance 5-6. ORNL =~ Y-12 Technical Library 78, M. S. Lin Document Reference Section 79. M, I. Lundin 7-41. Laboratory Records Department 80. H. G. MacPherson 42 . Laboratory Records, ORNL R.C. 81, J. C. Mailen 43, J. L. Anderson 82. H. McClain 44, C. F. Baes 83. H. E. McCoy 45, E. S. Bettis 84. L. E. McNeese 46. R. E. Blanco 85, A. S. Meyer 47. F. F. Blankenship 86. R. E. Moore 48. C. M. Blood 87. R. L. Moore 49. E. G. Bohlmann 88. D. M. Moulton 50. G. 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