ORNL-TM-2058.txt

 

JAN 2 6 1968

MASTE:

OAK RIDGE NATIONAL LABORATORY
operated by

 

UNION CARBIDE CORPORATION
NUCLEAR DlVIS'ON CARBIDE
for the

U.S. ATOMIC ENERGY COMMISSION
ORNL - TM- 2058

&6

 

MEASUREMENT OF THE RELATIVE VOLATILITIES OF FLUORIDES
OF Ce, La, Pr, Nd, Sm, Eu, Ba, Sr, Y and Zr
IN MIXTURES OF LiF AND BeF2

J. R. Hightower, Jr.
L. E. McNeese

NOTICE This document contains information of a preliminary nature
and was prepared primarily for internal use ot the Oak Ridge National
Loboratory. It is subject to revision or correction and therefore does

not represent a final report.
SIGTRIBUTION OF THis DOCURERT 15 INRAUTED
 

 

 

LEGAL NOTICE

This report was prepared os an account of Government sponsored work. Neither the United States,

nor the Commission, nor any person acting on behalf of the Commission:

A. Makes any warranty or representation, expressed or impliad, 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 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’’ 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 occess to, any information pursuant to his employment or contraect with the Commission,

or his employment with such contractor.

 

 

 

 

 

 
:

ORNL-TM-2058

Contract No. W-TMOS-eng—26

CHEMICAL TECHNOLOGY DIVISION

MEASUREMENT OF THE RELATIVE VOLATILITLES OF FLUORIDES
OF Ce, La, Pr, Nd, Sm, Eu, Ba, Sr, ¥ AND Zr
IN MIXTURES OF LiF AND BeFo

J. R. Hightower, Jr.
.. E. McNeese

LEGAL NOTICE

Thie report was prepared as an account of Government sponsored work. Neither the United
States, nor the Commissicn, nor any person acting on behalf of the Commiaaion:

A. Makes any warranty or representation, expressed or implied, with respect to the accu-
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’ includes any em-
ployee or contractor of the Commisasion, or employee of such contracior, to the extent that
such employee or contractor of the Commission, or employee of such contractor prepares,
digseminates, or provides accesa to, any information pursuant to his empioyment or contract
Wwith the Commission, or his employment with such contractor,

JANUARY 1968

OAK RIDGE NATIONAL LABORATORY
Qak Ridge, Tennessee
operated by
UNION CARBIDE CORPORATION
for the
U.S. ATOMIC ENERGY COMMISSION

SYCTIRY I
Ty b by TR
ot °

\“fibi
"
-
iii

CONTENTS
ABSTRACT .
1. INTRODUCTION .
2. PREVIOUS STUDIES ON VAPORIZATION OF MOLTEN SALT MIXTURES
5. EXPERIMENTAL EQULPMENT .
L. MATERIALS
EXPERIMENTAL PROCEDURES
6. DISCUSSION OF RESULTS
T. ESTIMATION OF ERRORS IN RESULTS
7.1 Nonuniform Liquid Phase Concentration .
T.2 Diffusion of Vaporized Materials Between Vaporization
and Condensation Surfaces .
7.3 Inaccuracies in Analyses of Salt Samples
7.4 Holdup of Condensate in the Condenser .
8. CONCLUSIONS
REFERENCES .
APPENDIXES .
Appendix A .
Appendix B . .
Appendix C .
Appendix D .
Appendix E .

10
12
15
16

16
16

N
19

20
21

55

37
Lo
{\
MEASUREMENT OF THE RELATIVE VOLATILITIES OF FLUORIDES
OF Ce, la, Pr, Nd, Sm, Eu, Ba, Sr, Y AND Zr
IN MIXTURES OF LiF AND BeF-
J. R. Hightower, Jr.
L. E. McNeese

ABSTRACT

One step in processing the fuel stream of a molten
salt breeder reactor is removal of rare earth fission
product fluorides from the LiF-BeFs carrier salt by low
pressure distillation. For designing the distillation
system we have measured relative volatilities of the
fluorides of Ce, La, Pr, Nd, Sm, Eu, Ba, Sr, Y, and Zr
with respect to LiF, the major component. The measure-
ments were made using a recirculating equilibrium still
operated at 1000°C and at pressures from 0.5 to 1.5
mm Hg. Errors from several sources were estimated and
shown to be small.

1. INTRODUCTION

The molten-salt breeder reactor (MSBR) is a reactor concept
having the possibilities of economic nuclear power production and
simultaneous breeding of fissile material using the thorium-uranium
fuel cycle.l The reactor is fueled with a mixture of molten fluoride
salts which circulate continuously through the reactor core where
fission occurs and through a heat exchanger where most of the fission
energy is removed. The reactor also uses a blanket of molten fluorides
containing a fertile material (thorium) in order to increase the
neutron economy of the system by the conversion of thorium to fissile
uranium-23%33. A close-coupled processing facility for removal of
fission products, corrosion products, and fissile materials from
these fused fluoride mixtures will be an integral part of the reactor

system.

During one step of a proposed method for processing the fuel

stream, LiF and BeF, are separated from less volatile fission
product fluorides by low pressure distillation. Important fission
products having fluorides less volatile than LiF include Ba, Sr, Y,
and rare earths which have significant fission yields. Design of
distillation systems and evaluation of distillation as a processing
step require data on the relative volatilities of the fluorides of
these materials. The purpose of this report is to summarize the
results of an experimental program designed to yield the needed

relative volatility data.

2. PREVIOUS STUDIES ON VAPORIZATION
OF MOLTEN SALT MIXTURES

Very little information has been reported on distillation of
molten salts or on vapor-liquid equilibria involving fluorides of

interest.

Singh, Ross, and Thoma2 have shown vacuum distillation to be
an effective method for removal of cationic impurities such as Na,
Ca, Mg, and Mn from LiF on a small scale. The use of distillation
for removal of rare earth fission products from MSBR fuel salt was

5

suggested by Kelly” on the basis of estimated vapor pressures of the
rare earth fluorides. Kelly's experiments on batch distillation
using salt similar to the fuel salt from the Molten Salt Reactor
Experiment demonstrated that distillation was possible and yielded
average relative volatilities of 0.05 and 0.02 for LaFs and SmFs,

respectively.

Relative volatility is a useful technique for representing
vapor~liquid equilibrium data and the relative volatility of

component A referred to component B, QAB’ is defined as

B Y p/ XA

o, =
AB yB;XB

where Yo, g = vapor phase mole fraction of components A and B
2

respectively. ~—
Xy g = liquid phase mole fraction of components A and B
2

respectively.

ScottlL measured relative volatilities of six rare earth tri-
fluorides at temperatures from 900°C to 1050°C in a simple closed
vessel with a cold surface in the vapor space on which a vapor
sample condensed. His results showed that the average relative
volatilities of the trivalent rare earth fluorides in LiF varied
from 0.01 and 0.05.

Cantor reported5 measurements made by the transpiration method

5

which indicated relative volatilities for LaFs of 1.4 x 10~ and

1.1 x 10™ at 1000°C and 1028°C, respectively.
3. EXPERIMENTAL EQUIPMENT

A diagram of the equilibrium still used in this study is shown
in Fig. 3.1 The vaporizing section was a 16-in. length of 1 l/2—in.
diam sched 40 nickel pipe. The condensing section was made from
l-in.-diam sched 40 nickel pipe wrapped with cooling coils of 1/&-
in. nickel tubing. Condensate collected in a trap below the condenser
and overflowed a weir before returning to the still pot. The
condensate trap (diagrammed in Fig. 3.2) was designed to provide
flow of condensate through all regions in order to collect a
representative condensate sample. A vacuum pump was connected near
the bottom of the condenser. A photograph of a typical still is

shown in Fig. 3.5.

A diagram of the pressure control system is shown in Fig. 3.L.
Pressure was measured at a point near the condenser in the line
connecting the still and the pump. As there was little or no gas
flow from the still, the measured pressure should have been equal to
the condenser pressure. Pressure was controlled by varying an argon
flow to the vacuum pump inlet which changed the pump inlet pressure.
The pressuré was sensed by a Taylor absolute transducer with a range

of O to 6 mm Hg abs. The signal from the transducer was fed to a
1-1/2 -in.
NICKEL PIPE —_|

VAPORIZING
LIQUID

 

   

THERMOWELL

s

 

ORNL DWG 66-8393

 

 

 

  
 
 
 
   

1-in.
NICKEL
PIPE
,/’——“““——.'
q s TO VACUUM
PUMP
q/////’ ,
D
q/ l
)
c’////
)
<’////
)
<’////
<’////
<”////
CONDENSED
SAMPLE

 

AIR-WATER
MIXTURE

NICKEL TUBING

Fig. 3.1 Molten Salt Still Used for Relative Volatility

Measurements.
ORNL DWG 67-6890

-~ 1-1/16" ———= WELDED TO

CONDENSER
|
: | + HERE

 

N
1 %

| N}

LIQUID RETURN /.._3/3"-—
LINE CONNECTED
HERE @_

Fig. 3.2 C(Cross Section View of Condensate Trap Used in Molten
Salt Equilibrium Still.

 

 

i

   

 

 

 

 

 

 

 
 

 

 

PHOTO 87396

 

 

 

 

s
’\

T

 
ORNL DWG 67-11662

ABSOLUTE PRESSURE
McLEOD PRESSURE RECORDER ARGON
GAUGE TRANSDUCER CONTROLLER

?:? O_—GXCONTROL
VALVE

VACUUM

LIQUID PUMP
TRAP

 

 

 

1
|
I
I
I
I
|
-

 

|
EQUILIBRIUM
I TUSTILL !

Fig. 3.4 Molten Salt Equilibrium Still Pressure Control.
Foxboro recorder -controller which in turn operated an air-driven
control valve to vary the argon flow. The pressure at the measuring
point was also read with a tilting McLeod gauge and with an

ionization guage.

L. MATERIALS

The rare earths and yttrium were obtained from commercial
sources as oxides with a minimum purity of 99.9% and were converted
to the trifluorides by fusion with ammonium bifluoride as described
in appendix E. The LiF, BaFs, SrFs, and ZrF, were commercial c.p.
grade material. The source of BeFz for these experiments was 2 LiF
BeF- which was obtained from Reactor Chemistry Division's Molten
Salt preparation facility. The most troublesome impurities in
these chemicals were thought to be oxides or oxyfluorides. However,
analyses indicated oxygen corcentrations to be low, as shown in

Table 4.1.

Table 4.1 Oxygen Analyses of Chemicals Used
in Equilibrium Still Experiments

 

 

Material wt % Os
CeFq 0.05
NdF, 0.018
PrFq < 0.01
LaFs < 0.01
SmFq .05
EuFg C.12
YF4 0.05
BaF= .31
SrF- 1.09
Zr¥, 0.8
LiF 0.27
2 LiF - BeFs 0.46

 

 
5. EXPERIMENTAL PROCEDURES

The salt charge for an experiment was prepared by melting in
a graphite-lined crucible sufficient quantities of LiF, 2 LiF-BeFs,
and the fluorides of interest to yield a mixture having the desired
composition and weighing 90 gms. The salt was blanketed with argon
during all operations and after melting the mixture, it was sparged
with argon for approximately 1/2 hr at 800° to 850°C. The mixture
was then allowed to solidify and the resulting salt ingot was loaded
into the still with little danger of transferring finely divided
salt into the condensate trap which could result in substantial
error in relative volatility. The threaded cap on the still was
then backwelded to produce a leak-tight system, the condenser section
of the still was insulated, and the still was suspended in the
furnace. After leak-checking the system, it was repeatedly evacuated
and brought to 1 atm pressure with argon in order to rid the system
of oxygen. The pressure was set at that desired for the run, the
furnace temperature was raised to 1000°C, and the condenser tempera-
ture was set at the desired value. During runs with fluorides
dissolved in LiF, the operating pressure was 0.5 mm Hg and the
condenser outlet temperature was 855° to 875°C; during runs with
the LiF-BeF, mixture, the pressure was 1.5 mm Hg and the condenser

outlet temperature was 675° to TOO°C.

An experiment was continued for approximately 30 hrs after
which the system was cooled to room temperature and the still was
cut open to remove the salt samples from the still pot and condensate
trap. These samples were then analyzed for all components used in

the experiment.

Since beryllium compounds are toxic when inhaled or ingested,
special precautions were taken during runs using BeF, to prevent

exposure of operating personnel.
10

6. DISCUSSION OF RESULTS

Experimentally determined relative volatilities of six rare
earth trifluorides, YF5, BaF», SrF,, BeFs, and ZrF,, with respect to
LiF (measured at 1000°C and 1.5 mm Hg in a termary liquid having a
molar ratio of LiF to BeF» of approximately 8.5) are given in Table
6.1. The mole fraction of the component of interest varied from
0.01 to 0.05. It should be noted that the relative volatilities of
the fluorides of the rare earths, Ba, Sr, and Y are lower than 2 x
10_u with the exception of Pr and Eu which have relative volatilities
of 1.9 x 10-3 and 1.1 x 10-5, respectively. The relative volatility
of ZrF, was found to vary between .76 and l.4 as the ZrF, concentra-
tion was increased from 0.03 mole % to 1.0 mole %. The average
relative volatility of BeF» was found to be 4.73 which indicates that
vapor having the MSBR fuel carrier salt composition (66 mole % Lif-3L
mole % BeFs) will be in equilibrium with liquid having the composition

91.2 mole % LiF-9.8 mole % BeFs.

Relative volatilities with respect to LiF are also given for
five rare earth trifluorides in a binary mixture of rare earth
fluoride and LiF. These measurements were made at 1000°C and 0.5 mm
Heg using mixtures having rare earth fluoride concentrations of 2 to
5 mole %. Except for PrF5 the relative volatilities for the rare

earth fluorides are slightly lower where BeF- is present.

It is interesting to compare the measured relative volatilities
to values predicted via Raoult's Law where the pertinent data are
available. For mixtures which obey Raocult's Law (ideal solutions),
the relative volatility of component A with respect to component B
is equal to the ratio of the wvapor pressure of compenent A to that
of component B. Relative volatilities were calculated for fluorides
for which sublimation pressure data are availab1e6 and are compared
with experimentally determined values in Table 6.2. The ideal
relative volatilities were calculated using sublimation pressures of
the rare earth fluorides at 1000°C. The deviation between measured

and predicted relative volatilities is within the probable error in
11

Table 6.1 Relative Volatilities of Rare Earth Trifluorides,
YFs, BaFp, ZrF,, and BeFs at 1000°C with Respect to LiF

 

Relative Volatility in

Relative Volatility in

 

Compound LiF-BeFo-REF Mixture® LiF-REF Mixture
CeFs 1.8 x 107 b2 x 107
LaFs 1.4 x 107 3 x 10
NdFq 1.4 x 107 6x 107"
PrFs 1.9 x 107 6.3 x 107
SmF 8.1 x 107 b5 x 107
EuFa 1.1 x 107 -

YF4 3.4 x 1077 .-
BaFyo 1.1 x 107 -—-
STF» 5.0 x 107 -—-
ZrF, L.k, 0.76° -—-
BeFo h.T}d -

 

 

®pressure was 1.5 mm Hg; lig. composition was ~85-10~5 mole % LilF-

Be F2 -REF .

bPressure was 0.5 mm Hg; liq. composition was ~95-5 mole % LiF-REF.

©Two widely different liquid compositions used. See Table 6.3.

dAverage of 18 values.

e , .
One value from two experiments reported; other value was questionable.,
12

Table 6.2 Measured and Predicted Relative Volatilities
with Respect to LiF at 1000°C

 

Measured Value

 

Component Binary System? Ternary Systemb Predicted Value
NdFs 6 x 1o’LL 1.h x 1o'LL 3 x 1o"LL
CeFs L2 x 107 3.3 x 1o~ 2.5 x 1o'LL
LaFs 3 x 107 1.h x 107 0.41 x 107
YF5 - 0.33 x T 0.59 x 10'h
BaFs .- 1.1 % 107 1.6 x 10'1L
SrFs --- 0.5 x 1o’LL 0.07 x 10')‘L

 

 

%3 .5 mole % of component shown in LiF.

b
3-5 mole % of component shown in mixture of 8.5 moles LiF per mole
BeFs.

measurements of the sublimation pressures and the relative volatilities
for fluorides of Ba, Y, and the rare earths. The somewhat larger

discrepancy for strontium is unexplained.

Table 6.3 and 6.4 summarize all the experiments. Numbers in the
"Material Balance" columns of Table 6.3 give an indication of the
consistency of each analysis. Since the concentration of each
material was determined independently in these experiments, a large
deviation of these numbers from unity indicates a poor analysis. Not
all concentrations were determined in the experiments listed in

Table 6.4; hence, there is no "Material Balance" column.
T. ESTIMATION OF ERRORS IN RESULTS

The recirculating still used for measurement of relative
volatilities operated under conditions such that the composition of
the condensate collected below the condenser was not necessarily

that of vapor in equilibrium with the bulk of the liquid in the
 

 

 

Table £.3
Summary of Experiments with Ternary Salt Systems
Mole Fraction in Liquid Mole Fraction in Vapor Relative
Volatility Relative
Run No. LiF BeF» 5rd Material LiF BeFz 3rd Material of 3rd Volatility Remarks
Componernt Balance Component Balance Component of BeFo
Be -1SM-1 0.848 0.103 SmFg: 0.049 All analyses 0.669 0.330 Contaminated Not L.os
were not sample applicable
independent
Be~25M-2 0.8L46 0.104 SmFs: 0.05 0.962 0.653  0.347 4.65 x 1078 0.948 1.2 x 1074 h.=22
Be-1Zr -3 0.893 0.097 ZrF,: 0.0096 0.970 0.667 0.323 0.010 _ 0.999 1.4 L.L6
Be -1Nd -4 0.840 0.101 NdFgz: 0.060 0.93% 0.636  0.364 2.51 x 108 0.922 6.14 x 1078 h.76
Be -2Nd -5 0.849 0.098 NdFz: 0.053 0.968 0.624  0.376 7.8 x 1077 0.900 2.09 x 10°5 5.22
Be -1Pr -6 0.836 0.110 PrFg: 0.056 1.00 0.651 0.3Lg 9.59 x 103 0.985 2.56 x 103 L.ot
Be -2Pr -7 0.842 0.104T  PrFgz: 0.055 0.985 0.625  0.375 5.26 x 10°° 0.912 1.30 x 1073 L.81
Be-lLa-8 0.802 0.102 LaFs: 0.096 0.967 0.605  0.3%95 1.03 x 1074 0.98G 1.h2 x 10°3 5.1k
Be -2Zt -9 0.878 0.120 ZrFy: 0.000% 1.060 0.602  0.396 1.6 x 10_* 0.959 0.763 L.50
Be=1Cc-=10 0.836 0.112 CeFz: C.053 1.00 C.605  0£.392 1.2 x 10° 1.019 3.11 x 105 L.81
Be-2La=11 0.845 0.1035 LaFa: 0.051 1.066 C.625  0.375% 5.1 x 1076 0.9k2 1.36 = 10 4 4.90
Be-2Ce-12 0.843 0.107 CeFg: 0.051 1.036 0.625  0.375 1.26 x 10 ° 0.961 3.33 x 10 * h.o71
Be-1Y-13 0.865 0.1002  YF5: 0.0357 0.957 0.643  0.357 9.1 x 107 0.967 3.43 x 103 4.80
Be-2Y-14 0.865 0.105 YFg: 0.0298 0.963 0.602  0.%98 h.51 x 1076 1.004 2.18 x 10 ¢ 5.44  Trouble during
run; results
questionable
Be-1U-15 0.892  0.0991 UF,: 0.010 1.0k 0.663  0.337 2.0l x 10 * 1.04 2.59 x 107 k.58
Be-1Eu-16 0.862 0.0884  EuFs: 0.050 1.011 0.654h  0.34T b.3% x 10 > 1.012 1.1h x 10 3 5.18 Questionable
Be-2Eu-17 0.870 0.100 EuFq: 0.029 1.001 0.625  0.378 1.61 x 10 ° 1.06 7.7 x 10 = 5.26 Questionable
Be «3Eu-18 0.896 0.0774  EuFs: 0.026 1.05 0.6%2  0.368 1.25 x 10 * 1.07 6.8 x 102 _ 6.7 Questionable
Be~1BaSr-19  0.81k4 0.156 BaFn: 0.01k 1.052 0.699  0.301 BaFo: 2.3 x 108 1.012 BaFs: 2 x 10 % 2.24  Difficulty with
SrFs: 0.016 SrFs: 1.46 x 10 8 SrFs: 1.1 x 10°% Analyses; results
questionable
Be ~1Y¥La ~20 0.830 0.1086 YF3: C.03%0 0.990 0.649  0.351 YFz: 7.3 x 1076 1.011 YFq: 3.17 x 107° 4.05
LaF5: 0.033 LaFs: < h.7 x 1075 LaFs: < 1.85 x 1074
Be -35m-21 0.870 0.086 SmFa: C.Okk 1.066 0.646  0.354 1.55 x 108 1.006 Yot x 1078 ) 5.57
Be-2BaSr-22  (.883 0.096 BaF,: C.0L03 1.012 0.702  0.298 BRaFs: $.33 x 1077 0.981 BaFo: 1.14 x 104 3,89
SrFz: 0.0093 SrFa: 3.66 x 1077 STrFsz: 5.0 x 10°°

 

 

¢1
Table 6.4 Summary of Experiments With Binary Salt Systems

 

 

Mole Percent Mole Percent Relative
Run Rare . . ‘o
Farth in in Volatility
Fluoride Still Pot Condensate With Respect
(%) (%) To LiF
MSES -3 -2 CeFq 0.82 0.037 0.0L45
MSES -3 -3 CeFq 0.90 0.1% 0.1k
MSES -3 -4 CeFq 1.07 0.009% 0.0087
MSES -3 -5 CeFx 0.90 £.019 0.021
MSES -3 -7 CeFq 1.05 < 0.0018 < 0.0017
MSES -3 -7 NdF5 0.62 0.0009 0.00014
MSES =% -8 CeFq 0.98 0.0030 0.0030
MSES -3 -9 CeFs 2.01 < 0.0018 < 0.00084
MSES -3 -9 LaFg 1.87 0.0003% 0.00017
MSES -% -9 NdF 5 2.00 < 0.0009 < 0.000L2
MSES -4 -1 LaF5 2.02 0.0006 0.00028
MSES -4 -1 NdFq4 2.05 < 0.0018 < 0.00084
MSES -4 -2 LaFs 2.0kL 0.0019 0.00089
MSES -4 -2 NdF5 2.01 0.0018 0.00086
MSES -4 -4 SmFq L.72 0.0087 0.0018
MSES =L -5 NdFq4 5.77 0.00%6 0.00059
MSES =4 -6 SmF 5 5.04 0.0012 0.0002%
MSES -4 -7 SmFq .88 0.00%5 0.00068
MSES -L -8 PrF, 5.54 0.0037 0.00063
MSES -4 -9 CeFq 5.7k 0.0026 0.00043
MSES -5-1 PrF, 5.52 < 0.00092 < 0.00016

71

 

 
15

vaporizing section. Factors which could cause error in the relative
volatilities include (1) a nonuniform concentration in the liquid

in the still pot, (2) unequal rates of diffusion of vaporized materials
between the vaporization and condensation surfaces, (3) holdup of
condensate on the walls of the condenser and the random manner in
which condensate flowed into the condensate trap, and (4) inaccuracies
in chemical analyses of the salt samples. Errors arising from these
factors will be discussed and estimates of the order of magnitude

of the error will be made.

7.1 Nonuniform Liquid Phase Concentration

As LiF and BeF vaporize from the salt surface in the still pot,
materials less volatile than LiF and BeF, tend to remain in the
vicinity of the vaporization surface and the surface concentration
of these materials will be greater than their average concentration
in the still pot. Under these conditions, the vapor phase concen-
tration of a material of low volatility will be greater than the
concentration in equilibrium with the bulk of the salt. Since surface
concentrations are difficult to measure (segregation occurs when
the salt freezes), the average concentration in the still pot is
used in calculating the relative volatility; the relative wvolatility
thus calculated will be in error by a factor equal to the ratio of
the surface concentration to the average concentration for the
material considered. A relation was derived for the wvariation in
concentration of materials of low volatility (Appendix A) in the
still pot in order to estimate the order of magnitude of the error

arising from this effect.

It was concluded that the measured relative volatilities are
in error by no more than a factor of 5 as a result of a nonuniform
liquid concentration and that the likely error is a factor of 2 or

less.
16

7.2 Diffusion of Vaporized Materials
Between Vaporization and Condensation Surfaces

The still used in the study was operated at a pressure near
the vapor pressure of the salt so that the recirculation rate (equal
to the vaporization rate) was set by the rate at which salt vapor
diffused through stationary argon in the passage between the vapori-
zation and condensation surfaces. An error in the measured relative
volatilities could arise because of differences in the rates of
diffusion of LiF vapor and the vapor of the material being considered.
The general case of two gases diffusing through a third stationary
component was solved (Appendix B) and conditions were noted under
which no error would occur in relative volatility from this effect.
The contribution to error in measured relative volatilities was

shown to be approximately 1% for typical operating conditions.
T.3 1Inaccuracies in Analyses of Salt Samples

Analyses for LiF in the salt samples had a reported precision
of i_}% and analyses for other materials in the samples had a
reported precision of + 15%. The maximum error in relative
volatilities due to inaccuracies in analyses were shown (Appendix C)

to be 36%.
7.4 Holdup of Condensate in the Condenser

The combination of differential condensation and irregular
condensate drainage in the condenser is another source of error in
the measured relative volatilities. Condensation of the wvapor is
not instantaneous and since the components of the wvapor have different
vapor pressures, materials of low volatility (such as rare earth
fluorides) tend to condense near the top of the condenser, LiF tends
to condense farther down the condenser, and is followed by BeFo.

If condensate does not drain from the condenser at a rate equal to
L7

the condensation rate, the composition of material entering the
condensate trap will not be that of the condensing vapor. If the
drainage of condensate from the top of the condenser is irregular,

the concentration of materials of low volatility in the stream entering
the condensate trap will fall below the concentration in the vapor
during the time that this material is held up and will rise above

the average value in the vapor when drainage is faster than the
condensation rate at the top of the condenser. The concentration of
materials of low volatility in the condensate trap will thus depend

on when the still is sampled and the concentration can be greater

or less than that in the wvapor.

Several factors tend to minimize the differences between the
composition of material in the condensate trap and the initial vapor
composition. Two of these are (1) the condensate trap has a finite
volume, which tends to average out variations in inlet concentration,
and (2) inherent variations in condenser temperature alter the
location where the major components condense, which promotes drainage

of materials of low volatility from the condenser.

Observed holdup of condensate near the top of the condenser has
been of the order of 0.5-1.0 g and the rare earth fluoride concen-
tration in this material was higher than the concentration in the
condensate trap by a factor of 10. An estimate of the maximum error
due to this effect is made in Appendix D where it is shown that the
observed relative volatility is within a factor of 2 of the actual

relative volatility.

8. CONCLUSIONS

Relative volatilities of six rare earth fluorides, YFs, BaFo,
SrFs, ZrF,, and BeF, have been measured with respect to LiF at 1000°C.
These values are such that the rare earth trifluorides (except EuFg
possibly), YF5, BaFs, and SrFs can be removed adequately in a still
of simple design with no rectification. Zirconium will not be

removed by the still.
18

Estimates of the errors incurred in measuring the relative
volatilities show that the measured numbers are probably within a

factor of 5 of the true equilibrium values.
19

REFERENCES

Kasten, P. R., et al., Design Studies of 1000-Mw(e) Molten-Salt
Breeder Reactors, USAEC Report ORNL-3996, Oak Ridge National
Laboratory, August 1966.

 

Singh, A. J. et al., "Vacuum Distillation of LiF," J. Appl. Phys.
36, 1367 (1965). |

Kelly, M. J., "Recovery of Carrier Salt by Distillation," Reactor
Chemistry Division Annual Progress Report, USAEC Report ORNL-3789,
Oak Ridge National Laboratory, Jan. 31, 1965, p. 86.

Ferguson, D. E., Chemical Technology Division Annual Progress
Report, USAEC Report ORNL-3830, Qak Ridge National Laboratory,
May 31, 1965.

Cantor, S., MSRP Semiannual Progress Report, USAEC Report ORNL-
4037, Oak Ridge National Laboratory, August 31, 1966, p. 140.

Kent, R. A., et al., Sublimation Pressures of Refractory Fluorides
NASA Report NASA-CR-T700L, 1966.

R. B. Bird, W. E. Stewart, E, N. Lightfoot, Transport Phenomena,
lst ed., John Wilery and Sons, New York, p. 502 (1960).

Rosenthal, M. W., et al., MSRP Semiannual Progress Report, USAEC
Report ORNL-4119, Oak Ridge National Laboratory, February 28, 1967,
p. 206.

R. B. Bird, W. E. Stewart, E. N. Lightfoot, Transport Phenomena,
lst ed., John Wiley and Sons, New York, New York, p. 560 (1960).

 
20

APPENDIXES
21

APPENDIX A

Nonuniform Liquid Phase Concentratioeff“flflfi_‘f7

Consider the equilibrium still shown in Fig. A.l, which is to be
used for measuring the relative volatility of material R with respect
to LiF. A dilute mixture of component R in LiF recirculates with
velocity V in this still because of vaporization and condensation of
salt vapor. 1In the model to be used, vapor leaves at the top of
the still, is condensed and returns instantaneously to the bottom of
the still. The initial concentration of material R in the liquid is
uniform. The concentration of material R at any time t and at any

level Z in the still pot is determined by the relation

Xy Ny,
"'——'—-at = = "'"_—"'_az (A']')
where
CR = molar concentration of material R
Npy = molar flux of material R in Z direction.
The flux of material R, Npyo is related to the concentration of
material R by the following:T
Xy
Npz = ¥g(Npg * Npz) - oD —7 (4-2)
where 7
NLZ = molar flux of LiF in the Z direction,
XR = mole fraction of material R,

p = molar density of the solution,
D = effective diffusivity coefficient.

Eq. (A.2) is true only for a binary mixture of R and LiF, although

this equation will also be used for estimating errors when three
22

ORNL DWG 67-6911-RI

VAPOR CONCENTRATION
OF R 1S oCR(L,fl

SURFACE

 

 

 

 

CONCENTRATION
OF R IS CR (L ,t) —fanannaraan ZsL
VAP O RIZING
LIQUID ONDENSER
SECTION [CONSISTS
OF R AND
LIF L
Z
BOTTOM
CONCENTRATION VEL\?CITY] }
OF R IS CQr(0,t)—s \ Z=0

 

 

 

 

Fig. A.1 Schematic Diagram of a Recirculating Equilibrium Still.
23

components (LiF, BeF- and material R) are present in the still. 1In
this case NLZ will represent the combined flux of LiF and BeF-. The
error in relative volatility in the ternary system should not differ

greatly from that in the binary system.

By substituting Eq. (A.2) into Eq. (A.1) and dividing by p, the

molar density (assumed to be constant), yields

2
Ky, TR (A.3)
where
N + N
V = "RZ - Lz _ liquid velocity in the still pot.

Equation (A.3) must be solved with the following boundary conditions:

rt
f

oF XR(Z, 0) = X, constant initial composition,

Il

% [XR(O: t) - XR(L: t)] (A,h)

7 = Li e =5 (1 -a)x (L, t)
z7=1

=
o<

where & = relative volatility of material R with respect to LiF. The

following approximation, valid for small & and small XR’ will be used:

aR-L = YR/XR . (A’5)

Eq. (A.3) and boundary conditions (A.4t) can be put in a more convenient

form for solution by introducing the following dimensionless variables:

X, - X,
o = X 2
i

0 = L&
With these substitutions Eqs. (A.3) and (A.L) become

%%-: %E-%gg - gg- (A.6)
8@ =0: o, 0) =0
£ = 0 %figlgz - Pe [0(0, 6) - a(l, ©) + (1 - )] (A7)
£ = 1; %g]§=1 = Pe (1 - a)[o(l, ©) + 1]

By taking the Laplace transform of Eqs. (A.5) and (A.T) with
respect to @ and solving the resulting ordinary differential equation,
the Laplace transform of the variation of surface concentration with
time can be obtained. The transform is very complicated but can be
inverted numerically to yield accurate values for the surface
concentration of material R as a function of time. Since vapor
removed at the top of the still is instantly fed back to the bottom
of the still, the average concentration of rare earth fluoride in

the still is Xi at any time.

Using the approximation in Eq. (A.5) we define the observed

relative as

Qg = YR/Xi (A.8)

where YR is the vapor phase mole fraction of R and Xi is the average

liquid concentration of R; this is the quantity measured in experi-

ments. The actual relative volatility is given by

Odactua]_ = YR/XR(L, t) = YR/Xi [U(l} Q) + l:t . (Asg)
25

and the ratio of observed relative volatility to actual volatility is

therefore

O:obs
=o(l, 8) + 1 . (A.10)

actual i

Variation of the ratio of the observed relative volatility to
the actual relative volatility is shown in Fig. A.2 as a function
of dimensionless time, Vt/L, for several values of the dimensionless

group VL/D.

In other studies,8 Hightower has shown the vaporization rate
in the still to be approximately %.% x lO_5 g/cm? - sec. The
density of LiF at 1000°C is 1.7 g/cm?. The effective diffusivity
of a typical fluoride in molten LiF in the still is not known
accurately because of natural convection in the still pot, but

L

probably has a value between 1O-5 and 10 cmg/sec. Since the
liquid depth in the still pot was approximately 2.5 cm for most

runs, the group VL/D varies between 0.5 and 5.0.

The usual operating time for the still was 30 hrs which yields
a value of Vt/L of 0.83. Thus, the measured relative volatilities
are in error by no more than a factor of 5 as a result of a nonuniform

liquid concentration and the likely error is a factor of 2 or less.
26

ORNL DWG 67-6910

 

 

 

 

 

 

 

10
To 91— | ! YL .10 —
g D
< |5
= 8 ]
S
—-— 7 I —
K
Q-
=
z & |
O
prd
S
5 — _
%g vLi
& D
Ll
Z 41— —
o
vbh _
% —-D~—-366
=
= 31— —
l.._.
=
L
QO
=
O
QO
E oo —
2
)
LT
O
O L
— vL _
& o !
] | | l | | |
0 0.2 04 06 08 1.0 1.2 14
DIMENSIONLESS TIME (1'_'-)

Fig. A.2 Buildup of Surface Concentration of a Slightly Volatile
Solute in a Recirculating Equilibrium Still with a Uniform Initial
Concentration (Valid for o <2 x 10 ).
o7

APPENDIX B

Simultaneous Diffusion of Two Gases
Through a Stationary Gas

It has been shown8 that under the operating conditions of the
equilibrium still the vapérization rate is controlled by the rate
of diffusion of LiF through stationary argon in the passage between
the vaporization and condensation surfaces. 1In a system containing
both LiF and a second volatile fluoride, the condensate composition
will be influenced by the relative rates of diffusion of LiF and
the second fluoride through stationary argon. For this reason, it
is of interest to determine the conditions under which relative
volatilities measured by this method represent equilibrium data and
to assess the contribution to error in measured relative volatilities

which can be ascribed to this effect.

Consider the simultaneous diffusion of gases 1 and 2 through
a third stationary gas 3. From the equation of continuity9 of 1, 2,

and 3

dw, - - -
i . : ‘
p'afE—+'O Tw o= -V - jj » 1= 1, 2, 3 (Bal)

where

p = density of gas mixture,
W, = mass fraction of component i,

= time

—_

t
—_
V = local mass-average fluid velocity,
-
j; = mass flux of i relative to the mass-average velocity v.

If the mixture of gases is ideal,

3
LM, Mj Dij ij ,i=1,2,3 (B.2)
28

where

- . . .
ji = mass flux of i relative to the mass-average velocity,
C = molar density of gas mixture,

p = density of gas mixture,

 

 

Mi = diffusivity of the pair i-j in the multicomponent mixture,
xj = mole fraction of component j in the gas mixture.
Equation (B.2) has been rearranged by Curtiss and Hirshfelder to
yield
=2 3
1 =
‘7xi = I = (xi fi; - Xy Ni) (B.3)
_‘]=l 1]
which can be written as
S 3 1 -
Ve, = I g (¢ N, -c N, ) (B.L)
j=1 "7ij
where
D,y = binary diffusion coefficient, i.e., diffusivity of
component i in component j,
fi; = molar flux of component i with respect to stationary
coordinates,
Ci = molar density of component 1i.

. . . = .
Since component 3 is assumed stationary, Ny = O and since D21 = D12’
the concentration profiles for the three components are defined by

the three relations

CDij (Ci Nj - Cj Ni)’ i=1,273 (35)
29

where

z = distance,
Ni = molar flux of component i in z direction

By noting that C = C, + C. + C these relations can be written as

17 e T b

 

 

 

 

dC1 . N2 . Nl c . N1 N1 . N1 (B 6)
T = — — S—— - Tm——— s -
dz CD12 CDl5 1 CD15 CD12 2 D15
Co | % c. + N + 2 c. -Ny (B.7)
= 5 *
dz CD25 CD12 1 CD12 CD25 2 5——
23
dc N, N
diz - C—.—Dl + C----D2 c; - (B.8)
13 03

Only two of these relations are independent, and solutions of two
of these equations or equations derived from them will define the
concentrations of the three components in the system. Equation

(B.8) has the boundary conditions

C. =2C at z
3 3z

il

z (Condensation surface)

C3 = C30 at z

0 (Vaporization surface)

and has the solution

N N C
o the tr Mo (8-9)
13 e3 30

Equations (B.6) and (B.7) can be combined to yield the exact

differential equation
30

 

 

 

 

 

 

 

 

1 1 1 € 1 a1 [
Ny, |8, "Cp, | @ N, oo, O |T
1 Ny N 1. 1 o STt 1 |,
G, N, e, T |2 S P R
+ 51— - 51- . (B.10)
13 o3
which can be written as
11
Ny # N3 [Dyp Dyz lac. -|M1 * Mo lac
2 1
N 1 1 N
2 ST 1
P12 D3 .
—1 1 -
D D N, + N
N+ N (212 13 fe, 471 T 2 c
S 1 1 N,
2 P12 P13
(N, + N,) dz
L =5 2 (B.11)
12

which has the boundary conditions

C; =Cio at z = 0 (vaporization surface)
2 = %20
C, = Cyz at z = z (condensation surface)
C, = Cez

and has the solution
31

 

 

 

 

 

 

 

 

 

LS ml 1T
Ny "Mt Pip Dys 16, v+ 3] ¢, Jo D3
N, R e N, | T T 1
i LD Dos - Do Dox]
1 _ _1- - -1 1 4
N, +N, | Do D |c N, + N, |C .- "D
1 M| Pi2 P15 %0 (Mt MalCo JPis Pos
N 1 1 | N, | T 1 1
-
Dy Dozl Do Dozl
(N, +N,) z
1 "N
oo (B.12)
12

Equation (B.9) and (B.12) represent two equations in the two

unknowns N, and N, for specified values of the concentration of

1 2
components 1, 2, and 3 at the end points of the system. For the

condition

Dl3 = ])23

these relations reduce to the relations

z(N, + N.)
1 2 D In C
————E—-—: 25 n )Z 3 (B-].B)
<20
N
Efi; Cop = €12
)
M N) P B (3.13)
¢ Lo ¢
N, ‘20 ~ “10

which can be combined to yield the relation
32

 

C z 23" 12 _ EEE
Ny €20 ¢ C10
N o, °© N (.15)
2 710 Elz_ 23/ 712 _.C..?.E
€30 €10
1f “12 denotes the actual relative volatility of component 1 with
respect to component 2, 032 is defined as
X y - X, C
o, =(;%) ( 3-})= 2 10 (B.16)
1 2 1 720
and if a12* denotes the observed relative volatility based on N1
and Ny,
o, =2 Z_l_) =% N (sar)
X1 Y2/ observed *1 NQ
where

X, = liquid phase mole fraction of i,
y; = vapor phase mole fraction of 1.

Thus, the ratio of the observed and actual relative volatilities is

*
2 N a0 (B.18)
%o Fy Gy

which is given by Equation (B.15). Conditions sufficient that alE*
m O

12 8Te
(1) constant temperature and pressure throughout system.

(2) gas mixture behaves as ideal gas,
(3) D13 = DEB,
(4) component 3 has negligible solubility in the liquid,
55

(5) Cp Cp

'C—"'":

10 20

 

O

Condition (5) can be met by having a sufficiently low condenser
temperature or by the condition that the heats of vaporization of

components 1 and 2 are equal.

If component 1 denotes a rare earth fluoride REF, component 2
denotes LiF, and component 3 denotes argon, conditions (3) and (5)

are not fulfilled, however, the error in for typical

OfREF--Li.]E‘
operating conditions is only 1%. Fig. B.l shows a solution of Eq.
(B.12) for the system NdF5-LiF-Ar at 1000°C and at various total
pressures. The error due to unequal diffusion rates partially

offsets the error due to the liquid concentration gradient.
3l

ORNL DWG 67-11663

 

 

 

 

 

 

o 1 T I
SYSTEM LiF'NdF3'Ar AT i1000°C
P=0.540mm Hg (VAPOR PRESSURE OF SALT)
1.O —
T
i
|
- ¢
>
= »
Ol m
<] O
- o1 L
S~ B
.0l 1 I 1 —
.01 Ol 1.0 10.0 100.0 1000
ProTr - P
P

Fig. B.1 Effect of Total Pressure on Relative
in NdF5-LiF-Ar System.

Volatility Error
55

APPENDIX C

Inaccuracies in Analyses of Samples

Analyses for the rare earths, alkaline earths, and zirconium,
were done by emission spectroscopy. Analyses for lithium was done
by flame photometry. Lithium analyses had an estimated precision
of i_}%, while the analyses done by emission spectroscopy had a
reported precision of i'15%- The weight per cent of the metal of
interest (li, Be, or lanthanide) is reported in early sample. The
relative volatility of the rare earth with respect to LiF can be

expressed in terms of the weight fractions of the metals

v L
o _YRE i
REF-LiF ~ _ L _ v (c.1)
RE Li

Q = relative volatility,

v - . . *
W, = weight fraction of metal i in vapor,
wiL = weight fraction of metal i in liquid.
The error in O due to errors in the analyses will be

REF-LiF
estimated as follows. Taking the natural logarithm of both sides of

Eq. (C.l) yields

v L L v
ln(OiEF-LiF) = ln(wRE ) - ln(wRE ) + 11:1(wL_:L ) --ln(wLi ) . (c.2)
Taking the differential of both sides of Eq. (C.2) results in

v
dorr-rir  “RE dwpE dwp g dwp 4 ,
= + . (C.3)
akEF-LiF W v W L w L W v
RE RE Li Li

 

 

 

 

This equation represents the fractional deviation of from

OtREF-LiF
36

the true value due to fractional errors in the measured weight
fractions. The signs of the deviations dwi are not known, but the

maxXimum error can be estimated since

 

 

 

v L L v

4O EF-LiF dwpp dupk duwp 4 dwp 4
_REF-LiF | _ s JLi_ |, . (C.h)

REp-Lir | ~ | w..’ w. P w. 2 w. v

RE RE Li Li

Substituting the reported precisions gives the following estimate

of the maximum error in aREF due to chemical analysis errors:

~LiF

A0 EF -LiF

= < 15% + 15% + 3% + 3% = 36%.
REF-LiF
.a7

APPENDIX D

Estimation of Errors Due to Differential Condensation
and Unsteady Condensate Drainage

As discussed in section 7.4 the measured relative volatility
can be either higher or lower than the true value because of
condensation and drainage effects in the condenser. The extreme
values of the observed relative volatility can be estimated with
the help of the following model. Assuming (1) steady state operation,
and (2) that a known fraction of the total vapor flow condenses at
a constant rate at one point at the top of the condenser but does
not drain to the condensate trap, the minimum value of the observed
relative volatility can be estimated. 1If it is assumed that the
material, which has been held up on the condenser wall drains
suddenly into the condensate trap and mixes with its contents, the
maximum value of the observed relative volatility results. The

true relative volatility lies between these extreme values.

For the first calculation (the minimum value) we assume that
the mole fraction of the rare earth fluoride is small compared to
1 and that the average molecular weight of the three vapor streams
in question are the same. Analyses of pertipent salt samples have
shown that these approximations are fairly good. A material balance
results in the following equation relating the concentration of the

three streams:

WYy = 9 Vg T (W mw) vy (p-1)
where
w = total mass flow rate of salt vapor,
wy, = mass rate of condensation of salt at the top of the
condenser,
Y10 = mole fraction of rare earth fluoride in the vapor in

equilibirum with the still pot liquid,
38

Yip = mole fraction of rare earth fluoride in the condensate at the
| top of the condenser,
Yi1 = mole fraction of rare earth fluoride in the condensate trap.

Given the results of an experiment, the observed relative volatility

is calculated by

y X
Fobs = Xl1 = (p-2)
1 e
where
X1 is the liquid phase mole fraction of rare earth fluoride,

X, is the liquid phase mole fraction of LiF,
Yo is the vapor phase mole fraction of LiF and is assumed to
have the same value in each of the three salt streams considered.

The actual relative volatility is given by the following equation

-—

T B

— (D.3)
5 Y

The ratio of the observed to the actual relative volatility then is

y
/a - _.......11 . (Dhr}

x =
obs Y10

This ratio can be obtained from Eq. (D.1) and is found to be

1

 

o
obs

1 - {1+ (1/f -1)(;-1-1—
s ) = (D.5)

 

where f = wl/w.
29

Observed values of Wy have been of the order of 0.5 g per 30 hr,

and measured values of w at the operating conditions of the still
were 3.8 x 10-h g/sec;8 A value of Wy of 1.0 g per 30 hr (allowing
a safety factor) results in a value of f of 0.02L4. Measured values
of (yll/y12) were 0.1. Using these values in Eq. (D.5), Obbs/a,ls

found to be 0.82.

If the 1 g of salt having a rare earth fluoride composition
1o suddenly mixes with the salt in the condensate trap (about 5 g

capacity) of composition Y11 the average composition is given by

avg

The ratio of the observed relative volatility to the true relative

volatility is given by

& y

obs  “av ) .
- = —53,10 (D.7)

Using Eqs. (D.1) and (D.6) this is shown to be

y
1/6 + 5/6 (3-}-]--
obs B 12 ) (D.8)
711
f+ (1-£)(—
Y12

 

Using observed values for (yll/y12) and f, Eq. (D.8) yields a value
of 2.1 for O%bs/a.,
o
obs

 

The extreme values for the error are then 0.82 < < 2.1.
It is unlikely that the extreme conditions depicted in this model
would actually be realized s6 that the observed relative volatility

would be less than a factor of 2 of the actual relative volatility.
Lo

APPENDIX E

Conversion of Rare Earth Oxides to Fluorides

The rare earths anpd yttrium were obtained from commercial
sources as the sesquioxides M-05, where M is la, Nd, Pr, Eu, Sm, or
Y. The cerium was obtained as CeO. The oxides were converted to
the trifluorides by reaction with ammonium bifluoride. The exact

reaction is not known but is approximately
M=0s + 4NH,F « HF —» 2MF3 + 2NH4F + 3H0 + 2NHs.

The eqfiipment used to carry out the reaction is shown in Fig. E.1l.
Approximately 1/2 1b of the rare earth oxide and 1 1lb of ammonium
bifluoride were mixed in the graphite liner. This was placed in

the flanged reaction vessel and heated to 110°C at which temperature
the NH,F - HF is molten. The mixture was allowed to remain at this
temperature for 16-L0 hrs to insure complete conversion of the

oxide to the trifluoride. At the end of the reaction period the
reaction vessel was heated to about 230°C to drive off reaction
products and unreacted NH,F * HF. The resulting vapor was contacted
with a spray of water at 100°C to condense and dissolve the NH,F - HF.
After driving off the bulk of the excess fluorinating agent the rare
earth trifluoride was heated to 500°C to dissociate any complexes

formed during the previous steps.
DRY
NITROGEN— —————

b1

ORNL DWG 67-11664

/—3/8" OFF - GAS LINE

 

 

 

 

 

 

 

  
  
 
 
  

4" DIAMETER
NICKEL k
VESSEL

GRAPHITE
LINER

 

el el el el et

 

n,fJHERMOWELL

 

<«———HOT WATER

 

 

 

 

 

I" DIAMETER
CONDENSER

AND

SCRUBBER

TO DRAIN

Fig. E.1 Equipment for Converting Rare Earth Oxides to Fluorides

with Ammonium Bifluoride.
:;?cfdw_uww?ggmfiwmwzgzmmzomuwwmmn

43

ORNL-TM-2058
INTERNAL DISTRIBUTION

MSRP Director's Office 32. H. T. Kerrx

Bldg. 920L4-1, Rm. 325 33, S. S. Rirslis
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F. Blankenship 37. H. E. McCoy
E. Blanco 38. H. F. McDuffie
0. Blomeke 39. L. E. McNeese
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B. Briggs W3, L. C. Oakes
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