ORNL-4415.txt

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
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necessarily constitute or imply its endorsement, recommendation, or
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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. E. Boyd 89. E. L. Nicholson
51. R. B. Briggs 90. A. M. Perry
52. H. R. Bronstein 91. J. T. Roberts
53. R. E. Brooksbank 92-93. M. W. Rosenthal
54. S. Cantor 94, C. E. Schilling
55, W. L. Carter 95, Dunlap Scott
56. L. T. Corbin 96. J. H. Shaffer
57. S. J. Cromer (K-25) 97. M. J. Skinner
58. D. J. Crouse 98-102. F¥. J. Smith
59, F. L. Culler 103, D. A. Sundberg
60. M. D. Danford 104. J. R. Tallackson
61. S. J. Ditto 105. R. E. Thoma
62. W. P. Eatherly 106. C. T. Thompson
63. D. E. Ferguson 107. W. E. Unger
64. L. M, Ferris 108. A. M. Weinberg
65. S. H. Freid 109, J. R. Weir
66. H. A. Friedman 110. M. E. Whatley
67. J. H Frye, Jr. 111. J. C. White
68. W. R. Grimes 112. R. G. Wymer
69. A. G. Grindell 113. Gale Young
70. W. 0. Harms 114, E. L. Youngblood
71. P. N. Haubenreich 115, P. H. Emmett {(consultant)
72. J. R, Hightower 116, J. J. Katz {(comnsultant)
73. H. W. Hoffman 117. J. L. Margrave (consultant)
74. P. R. Kasten 118. E. A. Mason (consultant)
75. M. E. Lackey 119. R. B. Richards (consultant)
EXTERNAL DISTRIBUTION
1206. C. B. Deering, U.S. Atomic Energy Commission, RDT Site Office, ORNL
121. A, Giambusso, U.S. Atomic Energy Commission, Washington
122-123. T. W. McIntosh, U.S. Atomic Energy Commission, Washington
124, H. M. Roth, U.S. Atomic Energy Commission, AEC, ORO
125,

126,
127.

128,
130,

'-3_131
132.
133-348.

o }8} _ o

M. Shaw, U S Atomlc Energy Comm1351on, Washlngton

W. L. Smalley, U.S. Atomic Energy Comm1581on, ORO

W. H. McVey, U.S. Atomic Energy ‘Commission, Washlngton
‘Roth, U.S. Atomlc Energy Comm1551on, Washington.

0. .
H. Schneider, U.S. Atomic Energy: Commission, Washlngton "
W.

"H. ‘Regan, U.S. Atomic Energy. Comm1351on Washlngton
L. J. Colby, Jr., U.S. Atomic Energy Comm1851on, Washlngton
J. A. Swartout, Union Carbide Corporation, New York, N.Y.
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