ORNL-4434.txt

 

 

ORNL 4434
UC 80 Reactor Technology

 

 

£ e Low- PRESSURE DISTILLATION OF MOLTEN 1l
e T _"_';"'FLUORIDE MIXTURES NONRADIOACTIVE TESTS |
e e e FOR THE MSRE DISTILLATION EXPERIMENT |

J R nghtower, J; AR 7_.  , 4 1

 

 

 

 

 

L e g ZiOAK RIDGE NATIONAI. I.ABORA'I'ORY

' ~ 2 .. TR operate d by : |

A T T e T T e UNION CARB!DE CORPORATION

ST e for Ihe ' e
u s ATOMIC ENERGY comwsstou

 

 

' BISTRIBUTION OF THIS DOCUMENT IS UNLIMITED -

 

 

 
 

 

 

S Prmted in " the Umted States of 'America. Ava:!able from R
: : ‘Nationa! Techmcal ‘Information Service U
US Department of Commerce, Sprmgf:e!d Vlrgsma 22151

' - “Price: Printed Copy $300 Microfiche $0.65 -

 

 

 

 

reprESents that ItS ‘use would not mfr:nge prwately owned nghts

_Thrs report was prepared as-an. account of work sponsored by the Umted‘
‘States Government Neither - the Unlted States nor. the United States Atomic |
Energy. Commlss:on nor any of their emplovees nor’ any of therr contractors, A
subcontractors, or their emplovees makes any- warranty, express or implied, or | -
assumes any legal liability or responsabmty for ‘the .accuracy, completeness orf' e
"usefufness of any enformatlon apparatus, product or “ process d:scfosed or_ e

 

 

 

 

 

3
[

“haal

 
 

W ORNL-4434

Contract No. W-7405-eng-26

¥)

 

CHEMICAL TECHNOLOGY DIVISION
UNIT OPERATIONS SECTION

LOW-PRESSURE DISTILLATION OF MOLTEN FLUORIDE MIXTURES:
NONRADIOACTIVE TESTS FOR THE MSRE DISTILLATION EXPERIMENT

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

 

- —————————LEGAL NOTICE

, This report was prepared as an account of work

, sponsored by the United States Government. Neither

the United States nor the United States Atomic Energy

= Cor_nmission, nor any of their employees, nor any of
. their contractors, subcontractors, or their employees,

| makes any warranty, express of implied, or assumes any

L legal liability or responsibility for the accuracy, com-

| pleteness or usefulness of any information, apparatus,

! product or process disclosed, or represents that its use

|

1

|

 

 

would not infringe privately owned rights.

 

JANUARY 1971

OAK RIDGE NATIONAL LABORATORY
/ Oak Ridge, Tennessee
- operated by

B UNION CARBIDE CORPORATION
- for the
- U. S. ATOMIC ENERGY COMMISSION

DISTRIBUTION OF THIS DOCUMENT IS

 
 

 

 

 

 

 

 

 

 

-
-

 
 

+)

3)
(=)}
.

 

iii
CONTENTS

ABSTMCT - o - - . e - * - * * * » * * . » - . . . . . -
INTRODUCTION « o . ¢« » ¢ o ® s 8 e « & s e * + o . .

EXPERIMENTAL EQUIPMENT . . . « ¢ « o ¢ o o « & &

2.1 Process Equipment . . . « « ¢« &+ ¢ ¢ o s o o s o @

2.2 Instrumentation . « ¢ « ¢ ¢ « o & o o .« ..
2.2.1 Measurement and Control of Temperature .
2.2.2 Measurement and Control of Pressure . . .
2.2.3 Measurement and Control of Liquid Level. .

OPERATING PROCEDURE. . ¢ & & ¢ « o o o ¢ o » o o s &

EXP ERIMNTAIJ RES ULT S - - 2 . a 2 [ ] - - * - - 2 .
4.1 Measurement of Distillation Rates . . + . « « «

4.2 Measurement of the Degree of Separation of NdF3 from

LiF-Ber"ZI‘FZI_ Carrier Saltu e o 8 s o @ . . e
4 . 3 Difficulties - * » * - . . - . . L . - - » . . . . »

CORROSION TESTS. & « v & & ¢ &+ o o o o o o o o o o o o
POSTOPERATIONAL INSPECTION . . « « & & ¢ « o o o &
CONCLUSIONS. « &+ o &+ o o o o o o o o ¢ o s s o
ACKNOWLEDGMENTS. « « ¢ ¢ o« « o « o & o o o o &
REFERENCES +« « ¢ ¢ ¢ ¢ ¢ ¢ ¢ o ¢ o s o s o s o o o

A.PPENDIXES . . . . . . . . e . . e . . . . . . . . . . -

10.1 Appendix A. Derivation and Solution of Equations
Describing Concentration Polarization. . . . . . .

10.2 Appendix B. Drawings Showing Postoperational Wall-
Thickness and Dimensional Measurements . . . . . .

oI N N

10

12
15

21
29

30
34
35
36
37

38

39
46
 

 

 

 
 

 

)

LOW-PRESSURE DISTILLATION OF MOLTEN FLUORIDE MIXTURES:
NONRADIOACTIVE TESTS FOR THE MSRE DISTILLATION EXPERIMENT

 

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

ABSTRACT

Equipment was designed and built to demonstrate the
low-pressure distillation of a 48-liter batch of irra-
diated fuel salt from the Molten Salt Reactor Experiment.
The equipment consisted of a 48-liter feed tank, a 12-
liter, one-stage still reservoir, a condenser, and a 48-
liter condensate receiver. The equipment was tested by
processing six 48-liter batches of nonradioactive LiF-
BeFZ-ZrF4—NdF3 (65-30-5-0.3 mole %) at a temperature of
1000°cC.

A distillation rate of 1.5 ft3 of salt per day per
square foot of vaporization surface was achieved in the
nonradioactive tests. Evidences of concentration polari-
zation and/or entrainment were noted in some runs but
not in others. Automatic operation was easily maintained
in each run, although certain deficiencies in the liquid-
level measuring devices were noted. Condensation of
volatile salt components in the vacuum lines and metal
deposition in the feed line to the still pot are problems
needing further attention. Since a postoperational
inspection of the equipment showed essentially no dimen-
sional changes, the equipment was judged to be satis-
factory for use with radioactive material.

The results of these nonradioactive tests indicate
that the application of distillation to MSBR fuel salt
processing is feasible. |

- 1. INTRODUCTION

Low-pressure distillation hés_potential application in the proc-
essing of salt from molten salt breeder reactors (MSBR's). —Ifi the single-~
fluid MSBR concept, disfiliation éouid be used to adjust the-composi—
tion of the fuel salt for optimum removal of'thé'lanthanides by reduc-
tive extraction or for partial fecovery of valuable COmpbnents from

salt streams that are to be-discarded. In the two—fluid MSBR concept,
 

 

 

distillation could be used to separate the slightly volatile lanthanide
fluorides from the other'componéntS‘of the fuel carrier salt. A program
to establish the feasibility of distillation‘of highly radiocactive salt
mixtures from molten salt reactors has been under way for about three
years. The work has included the measurement of relative volatilities,
with respect to LiF, of a number of components of interest,l’2 as well
as the operation of a relatively large, semicontinuous still with non-
radioactive LiF—Ber-ZrFA-NdF3 (65-30-5-0.3 mole %). The results
obtained during the nonradioactive testing of the still are presented

in this report.

The objectives of thé nonradioactive tests described in this report
were: (1) to test the distillation equipment to determine whether it
would be suitable for use with radioactive salt, (2) to gain ekperience
in the operation of large, low-pressure, high~temperature stills and to
uncover unexpected areas of difficulty, (3) to measure distillation
rates attainable in large equipment, and (4) to determine the extent to

which concentration polarization and entrainment occur in this type of

operation.
2. EXPERIMENTAL EQUIPMENT

2.1 Process Equipment

The equipment used in the nonradioactive tests included a 48-liter
feed tank containing the salt to be distilled, a 12-liter still from
which the salt was vaporized, a 10-in.-diam by 51-in.-long condenser,
and a 48-liter condensate receiver. This equipment is described only

briefly here; a complete description is available elsewhere.3

The feed tank, shown in Fig. 1, was a 15-1/2-in.-diam by 26-in.-tall
right circular cylinder'made from 1/4-in.-thick Hastelloy N. It was

designed to withstand,an external pressure of 15 psi at 600°C.

The condensate receiver, shown in Fig. 2, was a l6-in.-~diam by

16-1/2-in.-tall right circular cylinder having sides of 1/4~in.-thick
 

ORNL DWG. 88-10983

 

@—VENT

1* SCH. 40 PIPE

Np INLET
4 0.D.x19GA. TUBE

 

 

FEED INLET

   

 

26

 

 

 

§oo0.x150A. TUBE

 

    
  

 

 

e e ——— T o — e ]

 

 

1
183 0.0,

 

 

 

 

- . — — — —— A — o — . — — . ———— —
—
-

 

 

 

o T o e ain m mw. e . m wm rrer emi oe ,  s S e AAR,  S t t  s  s il

 

 

 

 

)
h
I
I
l
i
{
i
I
|
!
15 1D, : | 'I 72° TYR
—~i |
8e | I | |
| I | |
| ' l !
| b ! !
| I ! :
i i I |
: o
i ! l
| \ |
i ! |
| W\ ‘
= fe- % {- \» THERMOCOUPLE WELL
|| i 2 0.D.x19 GA. TUBE
=S FEED OUTLET ——
30.0.x15 oA TUBE
PLAN VIEW
el

 

 

 

 

 

 

 

 

 

 

 

Fig. 1. Molten-Salt Distillation Experiment: Schematic Diagram
of the Feed Tank. Dimensions are given in inches.

 
 

ORNL DWG. 66-10984

 

VACUUM LINE

1" SCH. 40 PIPE

 

3

-4
ol
w
x
w
-
4
=2
o
o
o
=
@
w
X
-

©

E

THERMOCOUPLE WELL

0.0.x.042 WALL Tus

0.D.x.042 WALL TUBE

 

THERMOCOUPLE WELL

30.0.£.042 WALL TUBE

LEVEL PROBE TuBt

w

a

&

o

<

k<

. ©

0

(®)

z
a

w
B
2~
s 4
W o
zZx
iy
g°
o‘
!
a2
5 0O
u. e

 

 

©.D.

=

 

Schematic Diagram

 

 

 

4

e

g

o

X7 5
s

- /.l/fil E
imm— oo a
~ o
:.fl...r IIIIIIIIIIIIIIIIII ————— ]| o
e e e e = e e — — —— e = e = ——— i ——— - — - t

v}

v

— - —— . 1

o

i

e e e — - 0
T T oL LT T > ord
= e A

oo b

i | a - -
AL S| o
< 2% )
AN nkl |
|||||||||||||||| — ———— — oa - m

2 T4

3

=

291 -— ¢ -— - ™

X

- — - —_— e — - mnm —_— > o

 

 

 

 

 

 

 

 

 

 

 

 

in inches.

s are given in

imension

D

of the Condensate Receiver.

 
 

 

Hastelloy N and a bottom of 3/8-in.-thick Hastelloy N. It was designed

to withstand an external pressure of 15 psi at 600°C.

The still and condenser are shown in Fig. 3. The still pot con-
sisted of an annular volume between the vapor line and the outer wall,
and had a working volume of about 10 liters of salt. Both the still
and the condenser were made of 3/8-in.-thick Hastelloy N and were
designed for pressures as low as 0.05 to 1.5 térr*. The design tempera-

ture for the still pot and for the condenser was 982°C.

All valves and piping that did not contact the fluoride salts were
made of stainless steel and were housed in a sealed steel cubicle which
contained pressure transmitters and vacuum pumps. All other parts of
the system were made of Hastelloy N. All-welded connections were used
in the portion of the piping that was operated below atmospheric

pressure.

2.2 Instrumentation

Correct operation of the molten salt distillation equipment depended
entirely on measurements of temperature, pressure, and liquid level.
The instrumentation used in making these measurements is discussed

below.

2.2.1 Measurement and Control of Temperature

 

Temperatures were measured and controlled over  two ranges: 500-
600°C for the feed tank and condensate receiver, and 800-1000°C for . the
still and condenser. Platinum vs platinum-10% rhodium thermocouples
were used for the high—temperature meaéurements,_whereas less expensive
Chromel-Alumel thermocouples were used on the feéd tank, condensate
receiver, and salt transfer lines. Each of the thermocofiples (total,

48) wés enclosed in a 1/8-in.-diam stainless steel sheath, and insulated
junctions were used. Four 12-point recorders were available for readout:
two fqr the Pt vs Pt-107% Rh thermotouples, and two for the Chromel-

Alumel thermocouples.

 

*
1 torr is 1/760 of a standard atmosphere.
 

 

s3

 

   

 

 

 

14 0-

   

41

 

 

 

 

   
    

 

 

 

LEVEL PROBE
1} scu. 40 pipe

HANGER
BRACKET

SAMPLE TuSE
1} scH. 40 PIPE

 

Fig. 3.

 

 

. l
¥ i
SAMPLE ntszavom—/L_ 10 2.0

 

sy

 

Molten-Salt Distillation Experiment:

 

 

ORNL DWG. 88-10088

THERMOCOUPLE WELL
\ 1/2°0.0. TUeE mug

FEED LINE
3/4"00.x.072 WALL

    
   
 
  

 

 

LEVEL PROBE
I3 SCH. 40 PIPE

DRAIN & SPECIMEN HOLDER

THERMOCOUPLE WELL  ,5%0 p TUBE x19 GA.

172"0.0. TUBExI® GA.

VIEW AwA

Schematic Diagram

of the Vacuum Still and the Condenser. Dimensions are given in inches.

 
 

 

 

There were nine individually heated zones on the feed tank, still,
condenser, and receiver. Heaters on each of these zones were inde-
pendently controlled by a Pyrovane "on-off" controller, and the voltage
to heaters in each zone was controlled by Variacs. Heaters on seven

lines were manually controlled by "on-off" switches and Variacs.

2.2.2 Measurement and Control of Pressure

Pressure measurements over three ranges were required: 0-15 psia
for monitoring the system pumpdown at the start of a run and for
monitoring the system repressurization at the end of a run; 0-10 torr
for suppressing vaporization while the salt was held at operating

temperatures in the still; and 0-0.1 torr during distillation.

Absolute-pressure transducers (Foxboro D/P cells with one ieg
evacuated) covering the 0- to 15-psi range were used to measure the
pressure in the feed tank and in the still-condenser-receiver complex.
An MKS Baratron pressure measuring device with ranges of 0-0.003,

0-0.01, 0-0.03, 0-0.1, 0-0.3, 0-1, 0-3, and 0-10 torr was used to measure

very low pressure in the condensate receiver.

The system pressure was controlled in the 0.1-10 torr range by
feeding argon to the inlet of the vacuum pump. The Baratron unit pro-
duced the signal required for regulating the argon flow. Pressure was
not controlled in the 0-0.1 torr rénge; insteéd, the argon flow to the
vacuum pfimp inlet was stopped and the pump developed as low a pressure

as possible (usually 0.05 to 0.1 torr).

| It was neceséary to ensure that an excessive internal pressure did
not develbp in the system since, at operating temperature, pressures

in excess 6f'2‘a£m would have been unsafe. This was éécomplished by
usifig an absolute4preésure transmitter in the condenser off-gas line to
‘monitor the system'pressure.‘ Wheh the pressure_éxéeeded 15 psia, the

argon supply was shut off autdmatically.
 

 

 

 

 

2.2.3 Measurement and Control of Liquid Level

The -pressure differential between the outlet of an argon-purged dip
tube extending to the bottom of the vessel and the gas space above the
salt was used to measure the salt level in the feed tank and in the

condensate receiver.

Two conductivity-type level probes were used in the still for
measuring and controlling the liquid level. These probes essentially
measured the total condfictance'between the metal probes (that extended
into the molten salt) and the wall of the still; the total conductance

was a function of the immersed surface area of the probe.4

The conductivity probes (see Fig. 4) were similar to the single-
point level probes that were used in the MSRE drain tanks. Tests have
shown that the range of fhis type of instrument is limited to approxi-
matel& 30% of the length of the signal generating section because the
signal, which is nonlinear, becomes extremely insensitive to changes'in
molten-salt level outside this range. A 6-in. sensing probe was used
to control the liquid level between points that were 1 in. and 3 in.
beléw the still pot overflow; a longer sensing probe was used to measure

very low liquid levels in the still pot.

Metal disks were welded to the level probes to aid in their cali-
bration. These disks provided abrupt changes in the immersed surfacé
area of each probe at known liquid levels. 1In operation, the signal
from a probe changed abruptly when the salt level reached one of the
disks.

The still-pot liquid-level controller was a Foxboro Dynalog circular
chart recorder-controller, which consists of a 1-kHz ac bridge-type
measuring device using variable capacitance for rebalance. The proper
control action (see Sect. 3) was accomplished by héving a variable dead
zone imposed on the set-point adjustment mechanism. With the controller
set for the desired average liquid lefiél, the argon supply valve to the
feed tank was opened when the level indicator dropped 3% below the set
point and was closed when the level indicator rose 37 above the set

point.
 

 

EXCITATION
SOURCE

ORNL-DWG 67-4776R{

SIGNAL AMPLIFIER AND
LEVEL INDICATOR

 

 

 

 

 

 

 

SIGNAL LEADS

HEAD COVER

FOLDED EXCITATION
SECTION

CONTAINMENT VESSEL

 

CUTAWAY SIDE VIEW

 

 

 

 

1

P
K TS TR T T s
)

 

(XY

‘;0‘.““\“‘\“““\“‘ P S A S s N N S S S N O S A S R LS T e T T T e S oo s
S

 

P

/‘SiGNAL GENERATING SECTION

DISKS TO AID

CALIBRATION

Fig. 4. 'Simplified Schematic of Conductivity-Type Liquid-Level

Probe Used to Measure Salt Level in the Still Pot.
 

 

 

10

3. OPERATING PROCEDURE | &-J

The following sequence of operations was followed during the dis-
tillation of a 48-liter batch of salt. First, the salt was charged to

the feed tank from a delivery vessel through a temporary heated line.

| (This line was later disconnected, and the opening was sealed.) Then

the still pot was heated to 900°C, and the system was evacuated to 5
torr. Subsequently, the valve between the feed tank and the vacuum

pump was closed (see Fig. 5), and argon was introduced into the feed

tank in order to increase the pressure to about 0.5 atm; this forced

the salt to flow frofi the feed tank into the still pot. The condenser
pressure was then reduced to 0.05-0.1 torr in order to initiate wvapori-
zation at an appreciable rate. At this point, control of the liquid
level in the still pot was switched to the automatic mode. In this mode,
salt was fed to the still pot at a rate slightly greater than the vapori-
zation rate. The argon feed valve to the feed tank remained open
(forcing more salt into the still pot) until the liquid level in the
still rose to a given point; the valve then closed and remained in this .
position until the liquid level decreased to another set point. In

this manner, the wvolume in the still pot was maintained at 8.5 to 9.5

liters.

As the salt vapor flowed through the condenser, heat was removed
from the vapor by conduction through the condenser walls and the insula-
tion, and by convection to the air. The condenser was divided into three
heated zones, the temperature of which could be controlled separately
when condensation was not occurring. Sharp temperature increases above
the set points near the condenser entrance, and gradual increases near
the end of the condenser, accompanied the beginning of distillation as
the condenser pressure was decreased. Operation of heaters to keep the
temperature of the condenser above the condensate liquidus température

was not necessary during condensation.

The salt condensate drained through a sample cup at the end
of the condenser (see Fig. 3) and flowed into the condensate receiver.

Samples of condensate (10 g) were taken periodically by using a windlass - (sj
i

 

 

11

ORNL DWG 70~20

 

LEVEL
MEASUREMENT

| r_-- T CONTROL
| .
|
|

 

 

 

 

 

 

    
    

  

 

 

 

 

 

 

 

 

 

 

 

 

 

 

| ];Ei
¢
STILL |
POT :
! .
CAPILLARY
FLOW PRESSURE VACUUM
CONTROL MEASUREMENT PUMP
CONTROL
CONDENSER
B
o FEED " ' CONDENSATE
| ' ~ TRECEIVER

Fig. 5. Flow Diagram of Molten-Salt Distillation-Experiment.
 

 

 

12

to lower a small copper ladle (i.e., the type used for the MSRE) through
a 1-1/2-in. pipe into the sample cup. Figure 6 shows the sampler assembly
that was installed directly above the sample cup at the condenser outlet.
During sampling, the sample ladle was lowered into the sample cup filled
with molten salt, and retracted into position above the flange. After

the sample had cooled, it was removed for analysis by closing the lower

"valve and opening the flange.

After operation had proceeded for approximately 4 hr at 900°C, the
temperature of the still pot was increased to 1000°C. Then di#tillation
was continued until about 10 liters of salt remained in the feed tank.
At this}time, the condenser pressure was increased to 5 mm Hg, which
reduced the distillation rate to a negligible value. The salt remaining

in the feed tank was then transferred to the still pot, causing some of

the material already present in the still pot to overflow into the con-

denser. The resulting mixture in the still pot had a sufficiently low
liquidus temperature that the still-pot temperature could be lowered

to about 700°C without freezing the 4-liter salt 'heel" remaining in

the still pot (after most of the still-pot contents had been transferred
to the feed tank).

Finally, the system pressure was increased to 1 atm. At this point,

the run was complete.
4. EXPERIMENTAL RESULTS

The distillation experiments were performed in Bldg. 3541, which

is specially equipped for containing experiments that involve large

‘quantities of beryllium. 1Installation of the equipment was started on

September 1, 1967, and the first 48-liter batch of salt was introduced
into the.system on December 14, 1967. During the approximate 6-month
period from the date of salt introduction until June 18, 1968, when the
experimental work was complete, six batches of salt were proceSsed in

the equipment. Results from the six runs are summarized in Table 1.
 

 

 

 

 

 

 

 

 

 

Fig. 6.

13

 

 

 

 

 

 

 

 

 

 

 

 

Photograph of Condensate Sampler Assembly.
Table 1.

 

Summary of Nonradicactive Experiments with Molten-Salt Still

 

 

 

Run Conditions Volume of Time
Still Condenser Salt
(Mggl) Dates Temp. Pressure Feed Mate:ial Distilled Re%;i§ed Purpose Remarks
{°C) (torr) (liters)
c-1 2/5/68- 990 0.06-0.5 LiF-BeF,-2rF, 35 83 To gain operating expe-
2/9/68 (65-30-5 mole %) rience and to determine
effect of condenser pres-
sure on vaporization rate.
c-2 2/26/68- 1005 0.07 LiF-BeF,-ZrF, 32 40 Same as MSS-C-1. Metallic deposit
2/28/68 {65-30-5 mole %) restricted salt
feed line.
c-3 3/26/68- 1004 0.075 LiF-BeFy-ZrF,;-NdF, 26.4 31 To investigate polari-
3/27/68 (65-30-5-0.3 mole %) zation and entrainment.
C-4 4/8/68- 980-1020 0.065 Distilled salt from 28 45 To determine the effect ZrF; condensa-
4/10/68 MSS-C-1 of temperature on vapor-  tion in vacuum
ization rate. line resulted in
abnormally low
‘ rates.
c-5 5/27/68~ 950-1025 0.06 LiF-BeFy-ZrF;-NdF3 32 41 To determine the effect
5/28/68 (65-30-5-0.3 mole %) of temperature on vapor-
ization rate.
c-6 6/11/68- 1000 0.07 LiF-BeFy-ZrF,~NdFq 32 53 To determine whether

6/13/68

{65-30-5-0.3 mole %)

polarization becomes
evident after long
operating times.

ZrFA condensation
in vacuum line
stopped distilla-
tion. Heating the
line to 950-1050°C
removed the ob-
struction.

 

71

 
 

 

15

During the period of operation, the feed tank, the receiver, and
the lower zones of the condenser were maintained at temperatures of
550 to 600°C for 185 days. A summary of the times during which the
still pot was maintained at various temperatures ranging from 25 to 1025°C

is given below:

25°C 12 days

500-650°C 56 days

750-875°C 110 days
900-1000°C 100 hr
1000-1005°C 160 hr
1005-1025°C 45 hr

In general, the performance of the equipment was satisfactory and
all design criteria were met or surpassed. Distillation rates were
higher than expected; automatic operation of the equipment was easily
maintained in spite of certain difficulties with the still-pot level
probes. These difficulties are discussed in Sect. 4.3. Air inleakage
during normal operation was insignificant. All of the pneumatic
components of the instrumentation system performed reliably, although

the electronic components presented some problems.

4.1 Measurement of Distillation Rates

Distillation rates were determined by observing the rate of rise of
liquid level in the condensate receiver. The measured rates and the
operating conditions under which they were observed are summarized in

Table 2.

The distillation rate is limited by friction losses in the passage-
way bétween the vaporizétion and condensation'surfaces. The force that
drives the vapor through this path is-thé-difference between the vapor
pressure of the'liqdid'in the still pot and the pressure at the con-

. denser outlet. 'Thus,‘the'distillation rate can be increased either by
increasing the temperature of the still pot (which, in turn, increases

the salt vapor pressure) or by decreasing the condenser pressure since,
 

 

 

16

Table 2. Summary of Distillation Rate Measurements

 

 

Run - Still-Pot Condenser Distillation

No. Temperature Pressure ' Rate
(MSS-) (°C) (torr) (ft3/£t2- day)

c-1 | 990 0.5 | 1.15

c-1 990 0.3 1.20

c~1 990 0.055 | 1.25

C~2 1005 0.07 1.50

c-3 1004 - 0.075 1.56

C-4 1020 0.065% 1.63

C-5 950 0.08 | 0.66

C-5 1000 0.08 S 1.21

Cc-5 1025 0.08 1.95

C-6 1000 0.08 1.40

 

3This may not be the actual condenser pressure since a ZrF4 Plug formed
in the vacuum line during this run.

in each case, the driving force for the vapor flow has been increased.

If the condenser pressure is very low with-respect to the vapor pressure
of the salt, the distillation rate should reflect the variation of salt
vapor pressure with still-pot temperature. Figure 7 shows the effect

of still-pot temperature on distillation rate for the runs in which the
condenser pressure was.below 0.1 torr. The distillation rate is expressed
as cubic feet of salt distilled per day per square foot of vaporization

surface.

A more useful correlation of distillation rate is one involving the
condenser pressure and the vapor pressure of the salt, since this type of
correlation could be used to estimate the performance of the still with
other salt systems. Such a correlation is shown in Fig. 8. The vapor
pressure of the salt (pl) was assumed to be the vapor pressure of 90-7.5-
2.5 mole Z LiF-BeF —ZrFa, which is given in ref. 5. A mixture of this

2
composition produces a vapor having a composition that is approximately
 

 

17

ORNL DWG 68-944| RI

TEMPERATURE, °C

 

 

 

 

1040 1030 1020 1010 1000 990 980 970 960 950
4.0 —r 1. 11Tt vt 7T T 1"
3.0 —
’N
ol
nm g’f 2.0 \. -
E o
. ® . -
229
E . InR= |8.3336--T—,?K—°-
« . o
=z
o
2 LOF -
| = -
=
E 0.8 |-
o - -
@
0.6 r -
0.4 : L ] I i |
7.6 7.7 7.8 7.9 8.0 8.1l 8.2
041K

Fig. 7. Effect of Still-Pot Temperature on Distillation Rate for
Runs in Which the Condenser Pressure Was Below 0.1 torr.
 

 

VAPORIZATION RATE, ft° salt/day-ft2

 

18

ORNL DWG 70-21

 

03—
0.25

0.5

 

 

| 11 b b1l | 1 |

 

Fig.

Pressure

015 02 03 04 0506 08 10 1§ 2 25
(pf—pf),[torr ]2

8. Dependence of Distillation Rate on Estimated Still-Pot
(pl) and Pressure at End of Condenser (pz).

 
19

./ 65-30-5 mole % LiF-BeF,~ZrF, and hence should approximate the composi-
2 tion of the material in the still pot at steady state.

The correlation in Fig. 8 was thought to be applicable because a
steady~-state mechanical energy balance for the isothermal flow of an
ideal gas through a conduit of constant cross section shows that the
flow of gas is a function of the difference between the squares of the
upstream and downstream pressures. This can be seen from the following
development. A steady-state mechanical energy balance for a flowing

fluid yields:

2 v2f

D

 

vdv+-p]:dp+ az = 0 , (1)
where v = velocity of fluid,

= density,

= pressure,

Fanning friction factor,

= diameter of duct,

v
N O M T T
0

= distance along duct.

By assuming that the fluid is an ideal gas, that is,

 

 

p = pM/RT , ' (2)
where T = absolute temperature,
M = molecular weight of the gas,
R = gas constant,

and by using the macroscopic mass balance equation which requires that

ov = (p; v{) » (3)

‘where the subscript 1 refers to the entrance to the duct, Eq. (1) becomes:

—%dp+%—1’——Ld 7 +————2fDdz= 0. (4)
(py vy)
 

 

 

20

Since the friction factor, f, depends only upon the Reynolds number

(which would be constant for an ideal gas at constant temperature),

Eq. (4) can be integrated between the entrance to the duct (point 1)
and the end of the duct (point 2) to yield:

 

=0, ()

_}:_1_{

RT + 2fL
My 2 D
1

where L is the length of duct. By solving Eq. (5) for vy and multiplying

it by Py> the following expression for the mass flow rate is obtained:

c = \/;1RTT V (plz - Pzz}
/5 -l

1

 

(6)

This expression shows the dependence of mass flow rate on the difference

between the squares of the upstream and downstream pressures.

Although the temperature was not constant and the cross section of
flow was not uniform in the runs made to measure distillation rates
(Table 2), a fair correlation of all the data was obtained (see Fig. 8).
The calculated vapor pressure of the salt, Py> ranged from 0.70 to 1.28
torr, and the measured condenser pressure, Pys ranged from 0.055 to 0.5
torr. The results suggested that an exponent of 0.41 might fit the
expression for mass flow rate somewhat better than the value of 0.5
suggested by Eq. (6); this discrepancy is proEably the result of not

including the logarithmic term in the correlation.
 

 

 

21

4.2 Measurement of the Degree of Separation

of NdF3 from LiF—Ber-ZrF4 Carrier Salt

In three runs (MSS-C-3, -5, and -6), a number of condensate samples

were taken and were analyzed for all salt components to determine the

effectiveness of the still for separating LiF-Ber-ZrF4 carrier salt

from NdF3, which is representative of the lanthanide fission products.
The ease with which NdF3 can be separated from the carrier salt is

conveniently expressed in terms of the relative volatility of NdF3 with

respect to the least volatile carrier salt component, LiF. The relative

volatility of NdF., with respect to LiF is defined as:

3

* / *
INaF..  *NdF

3 3
¢ = S (7)

Yrir/ *LiF

* *
where YNdF and YiiF are the mole fractions of NdF, and LiF, in vapor

which is in equilibrium with liquid containing x;d;3 and x;iF mole
fractions of NdF3 and LiF, respectively. The asterisks emphasize that
the concentrations are to be measured under equilibrium conditions.
Relative volatilities for the other components of the system are defined
similarly. Separation of a component from LiF by distillation is possi-
ble if the relative volatility of the component with respect to LiF is
not equal to 1l; the separation becomes easier as the deviation of the
relative volatility from 1 increases. The relative volatility of NdF3
with respect to LiF has a value of 1.4 x 10_4,'which indicates that
these -two components Eould be separated easily in a still that is
equivalent'to a single equilibrium stége. In practice, a single physical
stage (such as the still which Wasioperated in this study) may not be
equivalent to an equilibrium stage because of entraimment, concentration

polarization, or other factors.

In assessing the effectiveness of a still, it is convenient to
define an effective relative volatility that reflects nonequilibrium

conditions present during the still operation,as follows:
 

 

22

yNdF3/deF3(avg)

o = ’ (8)
OBS yLiF/xLiF(avg)

 

where the y's are mole fractions determined from condensate analyses
and the x's are mole fractions in the still pot averaged over the
entire still-pot volume. The performance of the still can be judged
by the ratio of the effective relative volatility (aOBS) to the relative
volatility (o), which will be denoted as R. Then the deviation of R
from 1 is a measure of the deviation from equilibrium conditions in

the still.

The quantity R may deviate from 1 because of several reasons,
including: (1) concentration gradients in the still-pot liquid (concen-
tration polarization), (2) entrainment of droplets of still-pot liquid
into the vapor leaving the still pot, or (3) contamination of the con-

densate samples by small amounts of material having high NdF, concen-

trations. These possibilities are discussed below. ’
Entrainment of small amounts of still-pot liquid into the wvapor

leaving the still pot would cause the observed concentration of NdF3 in

the vapor to be much higher than the equilibrium concentration. This,

in turn, would cause the value of R to be greater than 1. In the absence

of concentration polarization or other effects, a material balance gives

the following relationship between the value of R and the fraction of

the condensate that is entrained liquid:

1+.g(.jfi.§
R = = , (9
1+f(_r=i:r:)
TLiF
where f = moles of entrained liquid per mole of vaporized material,
xLiF = mole fraction of LiF in the liquid,
Yiip mole fraction of LiF in the vapor,

R
0

relative volatility of NdFB, with respect to LiF, at
equilibrium, as given by Eq. (7).
 

 

 

23

For the present system, the value of the X1 o ratio is about 1.6.

/Yisp
With this value for the ratio, entrainment of only 0.001 mole of liquid

per mole of vapor would result in a value of about 12 for R.

Concentration polarization would also cause R to have a value greater
than 1. This can be explained as follows. As the more-volatile materials
are vaporized from the surface, the NdF3, which is only slightly wvolatile,
is left behind. Thus, the NdF3 will have a higher concentration at the
surface than in the bulk of the liquid. In turn, the concentration of the
slightly volatile NdF3

vaporization occurs from liquid with successively higher NdF

will gradually increase in the vapor since further
3 concentra-

tions. Hence, the concentration of NdF, in the vapor will be higher than

3
would be the case under equilibrium conditions, and R will have a value

greater than 1.

The extent to which R deviates from 1 because of concentration polari-
zation depends on the dimensionless group D/vL, which qualitatively repre-

sents the ratio of the rate of diffusion of slightly volatile NdF., away

3
from the liquid-vapor interface to the rate at which this material is
transferred to the interface by convection. 1In the dimensionless group,

D is the effective diffusivity of NdF, in the liquid and is a measure of

the amount of mixing in the liquid, VBiS the average velocity of the
liquid moving toward the interface, and L is the distance between the
vaporization surface and the point at which feed is introduced. As the
value of this group increases, the value of R will approach 1, as shown
in Fig. 9. The method for calculating these curves is given in Appendix

Al

Contamination of the condensate samples by small amounts of material
containing high concentrations of NdF3 could also result in R values
greater than 1. Contamination of the samples during analysis is not
considered likely. However, it is possible that salt‘having a high
liquidus temperature and é high NdF3 concentration could have remained
on the condenser wall after the still-pot flushing operation (see Sect. 3)
at thé end of runs MSS-C-3 through MSS-C-6. If this had been the case,
the material would have been washed from the condenser walls during

the following run and would have contaminated the condensate samples.
 

 

 

DISTILLATION RATE, liters/hr

24

ORNL-DWG-70- 4566R!

 

14 I T T | . T I

 

 

 

35

 

|lo

0.286

-

v

R’Qoas/fl

 

 

| | | I | |

 

 

o 05 1.0 15 20 25 30

V, NO. OF STILL POT VOLUMES OF CONDENSATE COLLECTED

35

Fig. 9. Distillation Rate and Ratio of the Observed Relative

Volatility to the Actual Relative Volatility of NdF

LiF, as Measured in Run MSS-C-3. 3

with Respect to
 

 

25

Experimental values for NdF3 concentrations in the condensate do
not enable one to distinguish unambiguously between concentration polari-
zation and entrainment; however, they do allow assessment of the importance

of these effects if the level of condensate contamination is not too great.

Figures 9 through 11 show calculated R values for runs MSS-C-3, -C-5,
and ~C~6, respectively. 1In calculating R, the values of dypg Vere calcu-
lated from Eq. (7), using analyses of the condensate samples. The values

for y were measured values; the values for x were calculated from

"NdF_ (avg)
a material balance on NdF3 in the still pot in Wwhich it was assumed that a
negligible amount of NdF3 was removed in the vaPor. The value of xLiF(avg)
was estimated by calculating the liquid composition in equilibrium with
the measured vapor compositions, assuming that the relative volatilities
(with respect to LiF) of BeF2 and ZrF4 were 4.7 and 10.9, respectively.
.The relative volatility for BeF2 was ob;ained from measurements made in
small recirculating equilibrium stills. The relative volatility for ZrF4
was measured in run MSS-C-1 and is probably only wvalid for a still-pot
composition of 65-30-5 mole % LiF—Ber-Zth. Also shown in these figures
is the variation of distillation rate with time during each of the three

runs.

Values of the group D/vL which best represented the calculated R
values from each of the runs (Figs. 9-11) were chosen by trial and error
by assufiing that any deviation of R from 1 was caused entirely by concen-
tration polarization. As seen in Fig. 9, a value of 0.286 for D/vl was
found to generate a smooth curve that best represented the measured R
values in run MSS-C-3. Contamination of the condensate was not possible
in this run since no NdF3 had been used in the previous run. In run
MSS-C~5, the increase in the R values when the distillation rate was
suddenly increased was most closely represented by the assumption that
D/vL changed from 0.227 to 0.0215 when the rate increased. The ldw
initial R values indicate that contamination of the condensate from

material on the condenser walls was not important during this rum.

.In_run MSS-C-6, the last six'expefimental points correspond to a value
of 0.051 for D/vL. There appears to be no straight-forward explanation
for the high values of R observed in the first four samples taken during
 

 

26

ORNL DWG 70 4563RI|

 

| | I T T T

DISTILLATION RATE, Iiters/hr

 

 

 

 

90
80}
70l , -
60| .
sol- —

a0} -

 

30

20

H O O JODYWO

L1 1]

]

l

o

 

 

 

1ol | ] 1 | 1 1
' 05 10 15 20 25 30 35

V, NO. OF STILL-POT VOLUMES OF CONDENSATE COLLECTED

Fig. 10. Distillation Rate and Ratio of the Observed.Relative
Volatility to the Actual Relative Volatility of NdF3 with Respect to
LiF, as Measured in Run MSS~C-5.
 

27

ORNL - DWG - 70 -4564RI
| I I I I

 

\iters / hr

DISTILLATION RATE,

 

 

 

 

 

1000 *

I TTir
L1141l

|
1

100

®
Lol

T TUENT
®

1
1

D
L + 0.051

I
®
o

1

 

 

 

ob——— 1 1 L L
Yo 10 20 30 a0 50
V, NO. OF STILL- POT VOLUMES OF CONDENSATE COLLECTED

 

 

Fig. 11. Distillation Rate and Ratio of the Obsefved Re1ative
Volatility to the Actual Relative Volatility Of'--NdF'3 with Respect to
LiF, as Measured in Run MSS-C~-6. -
 

 

 

28

this run. The value of R was about 1000 in the first sample (0.8 still-
pot volume distilled) and decreased thereafter. The vaporization rate
was very high initially and may have caused both concentration polariza-
tion and entrainment. If we assume that the high R value in the first
sample was the result of concentration polarization only, the effective
difquiVity in the still-pot liquid would be 3.4 x 10-6 cm2/sec, which
is an order of magnitude lower than reported values6 of molecular
diffusivities in molten salt at temperatures less than 750°C. Thus,
concentration polarization alone cannot account for the high R values
observed. Of course, it is possible that these high values resulted
from contamination of the condensate. If salt with a high liquidus
temperature and a high NdF3 concentration had remained on the condenser
walls after the contents of the still pot were flushed out at the end
of run MSS-C-5, this material would have been washed into the sample

reservoir early in run MSS-C-6.

Values were calculated for the effective diffusivity in the still-
pot liquid by using values of the group D/vL given above and values for
v and L. Values for the average velocity (v) were determined from dis-
tillation rates, whereas those for the distance (L) between the feed
inlet and the liquid surface in the still pot were known. The range of
4 -4

to 16 x 10

one to two orders of magnitude greater than reported values of molecular

diffusivity values was 1.4 x 10 cmzlsec; these values are
diffusivities in molten salts and are equivalent to those which would be

expected if convective mixing were occurring in the still pot.

It is considered likely that concentration polarization and/or
entrainment effects were observed during the operation of the still,
although contamination of the samples with NdF3 from the condenser walls
prevents one from drawing firm conclusions. There were some periods of
operation in the experiments described here in which these effects were
within tolerable limits (in run MSS-C-3, R was never higher than 5, and.
in the early part of the run MSS-C-5, R was also below 5); thus there is
evidence that, by careful equipment design and proper choice of operating
conditions, concentration polarization and entrainment can be held to
acceptable levels. Further investigation would be required to determine

the proper operating conditions and equipment design.
 

 

 

29

4.3 Difficulties

Surprisingly few operational problems were experienced during the
experimental program. However, certain significant difficulties were

encountered, as discussed below.

The condensation of ZrF, and unidentified molybdenum compounds

obstructed the vacuum line oi two occasions. The first restriction
occurred during the fourth run and was removed by cutting into the
vacuum line; the second restriction occurred during the last run and

was removed by heating the vacuum line to 950-1050°C, thereby redistrib-
uting the material. Analysis of the material from the first deposit
showed it to contain 39.4% zirconium and 11.6% molybdenum, with fluoride

and oxide being the major anions.

During the second run, the salt feed line to the still became
obstructed. After the run had been completéd, the line was cut and a
5- to 10-g metallic deposit, consisting mainly of nickel and iron, was
found at the point where the feed line entered the still. This line was
replaced, and the still was operated for four additional runs. At the
end of the series of experiments, the feed line was again removed and
another metallic deposit was found at the same point. The composition and
the appearénce of the second deposit were similar to those of the first;
however, the open cross-sectional area at the point of the second deposit

was still about 507 of that of the unobstructed tubing.

The cause for the metal depbsition in the feed line is not known.
Two possible sources of the deposited material are: (1) suspended metals
and/or dissolved fluorides introduced with the feed salt, and (2) corrosion

products.
The possibility that corrosion of‘the system components may have been

a factor is suggested by the composition of the deposits [approximately
0.9 wt % cobalt and 0.7 to 2 wt % molybdenum (both elements appear in
 

 

 

30

Hastelloy N)1, and of the plug in the vacuum line (high molybdenum con-
tent). The extent of corrosion that would be necessary in order to pro-
duce such deposits would not have been detected by wall thickness measure-

ments (see Sect. 6) if the corrosion were general in nature. A possible

method for reducing and depositing dissolved fluorides is based on the

observation that higher-valence fluorides are, in general, more volatile
than 1owgr—vélente fluorides of the same element. This condition could
cause the still pot to be reducing with respect to the feed salt and,
in turn, to.promote reduction and depositiom of\felatively noble metals

at the entrance to the still pot.

‘Because the level probes were unexpectedly sensitive to changes in
salt temperature and still-pot pressure, they could not be calibrated for
exact still-pot conditions. To ensure that the still pot did not over-
flow during the filling operation, we added salt until the level reached
one of the calibration disks and a discontinuity in the recorder signal
was noted. This provided a definite measurement of the saltllevel, al-
though it was lower than the nominal operating level. Satisfactory
automatic operation in the vicinity of this signal discontinuity was

then possible.

5. CORROSION TESTS

Corrosion specimens of Alloy 82, Hastelloy N, TZM, Haynes Alloy No.
25, and Grade AXF-5QBG graphite (see nominal compositions in Table 3),
supplied by the Metals and Ceramics Division, were suspended in the wvapor
and in the 1iquid in the still pot during the six runs. The specimens,
1/16 in. thick x 3/8 in. wide x 3/4 to 2-1/2 in. long, were arranged in

two stringers mounted on a Hastelloy N support fixture that was tack-

‘welded to the Hastelloy N dip line of the still pot. The arrangement

and position of each stringer were such that specimens of each material
were eXpoéed to both vapor and liquid; a Hastelloy N specimen was centered
at the vapor-liquid interface. Figure 12 shows the two stringers on
removal from the still pot after the nonradioactive tests. An unexposed

stringer is also shown for comparison.
 

Table 3. Nominal Compositions of the Corrosion Specimens
Exposed in the MSRE Vacuum Distillation Experiment

 

 

 

, Element
- Material
Co Ni Mo Cr W Fe Ti Zr C Mn

Alloy 82 - Bal. 18 0.05 - — - - - 0.2
Hastelloy N ‘Trace 72 16 7 - 5 - - 0.06 -

TZM | - - Bal. - ~—— - 0.5 0.1 0.01 —

Haynes Alloy No. 25 Bal. 10 — 20 15 3 — -- 0.10 1.5
Grade AXF-5QBG - - - - -— == - - 100 -

isotropic graphite

 

1€

 
 

 

32

- ORNL DWG 69-98

 

 

 

 

   

 

 

Botfom 1 Deswgn' Liquid
' Interfoce
Legend A and B —Tested specimens as removed from the support.

C—-Untested specimens lighted to accentucte the machmmg paiterns
B2~ Alloy 82 (Ni-18 Mo-0.2 Mn-0.05 Cr)

N- Hastelloy N (72 Ni-16 Mo-7 Cr-5 Fe~0.06 C)

25-Haynes Alloy No. 25 (Co-20 Cr-15 W-10 N|-3 Fe-1.5 Mn-0. 10 C)
TZM-TZM (Mo-0.5 Ti-0.1 Zr- 0.01 C) -

G -Grade AXF-5QBG graphite

Fig. 12. Corrosion Specimens Removed from Still Pot in MSRE
Distillation Experiment. Unexposed specimens are shown for comparison.

   

-Vapor _ . op
 

 

 

33

At the conclusion of the nonradioactive tests, the specimens were
returned to the Metals and Ceramics Division for examination.7 The
resistance of the metals to attack in both the vapor and the liquid
zones was found to be in the following order: Alloy 82 > Hastelloy N >
TZM > Haynes Alloy No. 25 > Grade AXF-5QBG graphite. The specimens
exposed in the liquid zone appeared to have been attacked more severely
than those located in the vapor zone. The Alloy 82, Hastelloy N, and
TZM specimens appeared to be essentially unchanged. These observations
are only qualitative because (1) they are based only on visual examina-
tion, and (2) oxygen in the system (introduced as a result of a heater

failure described below) probably modified some of the corrosion results.

The following observations were made regarding the materials located
in the liquid zone. Some reaction between the salt and the Alloy 82
and Hastelloy N specimens is suggested because their surfaces were
sufficiently etched to make the grain structure clearly visible. The
Haynes Alloy No. 25 appeared to be severely cracked, and it broke easily.
The graphite specimens in the liquid zone were missing. Crystal-like
metallic deposits appeared to be clinging to the joining wires in this

region.

The presence of air, which was introduced into the system when a
tubular heater failed (in such a manner that a hole was melted in an argon
dip line while the system was at low pressure), accounts for the poor
performance of the graphite. The air that was introduced while the
system was pressurized remained in the system for about 500 hr; the still-
pot temperature during this period was near 700°C. (No other air was
introduced during this period.) The attack on the graphite specimens is
probably the result of oxidation during this period. The loss of the
graphite specimens in the liquid zone (but not in the vapor zone) is
probably_due to a '"washing effect" of the molten salt on the damaged
specimens as the still was filled and emptied. Although the Hastelloy
N specimens at the design vapor-liquid interface had gray matte surfaces,
no changes in the appearances of the specimens were clearly attributable

to the presence of a wvapor-liquid interface.
 

 

 

34

6. POSTOPERATIONAL INSPECTION

Since the equipment employed in the nonradioactive tests described
in this report was to be used later with radioactive materials, it was
inspected thoroughly after completion of the tests. Radiographic and
ultrasonic measurements of wall thickness were made at 225 points on
the vessel surface. In addition, length and diameter measurements
were made between selected locations. (Center-punched tabs at these
locations were provided for these measurements.) The postoperational
measurements wére compared with similar measurements made on the equip-
ment before operation. Measurements were concentrated in regions where

the highest stresses were expected.

Drawings M-12173-CD-019D, M-12173-Cp-020D, and M-12173-CD-021D
(Appendix B) show the 1ocations,pf the 225 points where wall thickness
measurements were made, as well as the locations of points between
which length and diameter measurements were made. "Also shown are the
pre— and postoperational measuiements. A comparison of the two sets
of thickness measurements showed an average decrease of 1.6 mils in wall
thickness, with both positive and negative deviations from the original
thickness. The largest differences were +9 mils and -8 mils. The change
in distance between two points about 50 in. apart was 0.026 in., which
is not considered significant. There was some indication that the still
pot had dropped to a slightly lower position, although the rotation of
lines between points on opposite ends of the condenser was less than

0.5°.

Visual inspection of the inside of the still pot showed the metal
to be in good condition; the walls were shiny, and no pitting or cracking

was evident. Radiography also showed no evidence of physical change.

We concluded that the equipment was in satisfactory condition for

use with radioactive materials.
 

 

 

35

7. CONCLUSIONS

The following conclusions have been drawn as a result of the experi-

mental work discussed above:

(1)

(2)

(3)

(4)

(5)

(6)

A relatively large molten-salt distillation system
has been operated successfully. Although some
problems must be solved before a distillation unit
can be incorporated into an MSBR processing plant,
the distillation of irradiated mixtures of molten
fluorides has been demonstrated to be feasible.

The measured distillation rates are adequate to per-
mit the use of distillation as a process step. For
operation under conditions in which the vapor pressure
of the still-pot material is 1 mm Hg or greater,
distillation rates of at least 1.5 ft3 of salt per
day per square foot of vaporization surface can be
obtained. The distillation rate was limited by
frictional losses in the vapor passageway; there-
fore, higher rates might be attainable under the
same operating conditions by careful design of the
salt vapor flow path.

Evidences of concentration polarization and/or
entrainment were seen during some runs in these
experiments. The fact that they were not seen in
all runs indicates that further investigation could
disclose the conditions under which a still could
be operated with concentration polarization and
entrainment held to acceptable levels.

A postoperational inspection of the still showed

only minor changes as the result of operation and
indicated that the equipment was in satisfactory

condition for use with radioactive materials.

The cause of repeated metallic deposits in the salt
feed line must be determined since such depositions
would disrupt the long-term operation of distillation
systems. : .

The condensation of volatile salt components and
corrosion products in the vacuum lines must be
prevented if long-term operation is to be feasible.
 

 

36

(7) More-reliable level-measuring devices for controlling
the still-pot liquid level should be provided. A
method more desirable than the one used for this
experiment would consist of several probes (of
the type described in this report) used at various
salt depths giving a control signal which would
change stepwise rather than smoothly. A number of
such probes, located at closely spaced intervals,
would permit sufficiently accurate measurement and
control of liquid level to make operation of a
stil]l feasible.

8. ACKNOWLEDGMENTS

The authors gratefully acknowledge the assistance of the following
individuals, whose help in operation of the equipment and interpretation
of the observations were indispensable: B. G. Eads and B. C. Duggins,
Instrumentation and Controls Division, for consultation about and repair
of liquid-level and pressure instrumentation; Anna M. Yoakum, Analytical
Chemistry Division, for analysis of the condensate samples; W. H. Cook,
Metals and Ceramics Division, for examination of corrosion specimens
and interpretation of results; B. A. Hannaford for advice and assistance
in photographing the results of the experiment; H. D. Cochran for assist-
ance in calculations and interpretation of measurements; V. L. Fowler,
R. 0. Payne, and J. Beams, technicians in the Unit Operations Section of
the Chemical Technology Division, for operation of the distillation
equipment; D. M. Haseltine, co-op student from the University of
Missouri, for assistance during equipment installation; and J. L. Wade,
pipefitter assigned to Bldg. 3541, for his diligence and ingenuity in

keeping the equipment in excellent operating condition.
 

 

«

1.

10.

 

37

9. REFERENCES

J. R. Hightower, Jr., and L. E. McNeese, Measurement of the Relative
Volatilities of Fluorides of Ce, La, Pr, Nd, Sm, Eu, Ba, Sr, Y, and
Zr in Mixtures of LiF and BeFZ, ORNL-TM-2058 (January 1968).

 

 

F. J. Smith, L. M. Ferris, and C. T. Thompson, Liquid-Vapor Equilibria
in LiF-BeF, and LiF-BeF,~ThF, Systems, ORNL-4415 (June 1969).

 

 

W. L. Carter, R. B. Lindauer, and L. E. McNeese, Design of an
Engineering—-Scale, Vacuum Distillation Experiment for Molten Salt

Reactor Fuel, 0RNL-TM—2213 (November 1968).

M. W. Rosenthal, MSR Program Semiann. Progr. Rept. Feb. 28, 1967,
ORNL_ll'llg, p- 76'

 

R. B. Briggs, MSR Program Semiann. Progr. Rept. Aug. 31, 1965,
ORNL-3872, p. 126.

 

Milton Blander (ed.), Molten Salt Chemistry, p. 592, Wiley, New York,
1964,

 

M. W. Rosenthal, MSR Program Semiann. Progr. Rept. Aug. 31, 1968,
ORNL-4344, p. 282.

 

R. B. Bird, W. E. Stewart, and E. N. Lightfoot, Transport Phenomena,
1st ed., p. 502, Wiley, New York, 1960.

 

R. V. Churchill, Operational Mathematics, 2nd ed., p; 183, McGraw-
Hill, New York, 1950.

 

L. A. Schmittroth, Communications of the ACM 3, 171 (March 1960).
 

38

 

APPENDIXES

10.
 

 

 

i

39

10.1 Appendix A. Derivation and Solution of
Equations Describing Concentration Polarization

As a salt mixture is vaporized from the surface of the still-pot
liquid, the concentration of the less-volatile component (e.g. NdF3) at
the interface will increase above its average concentration in the still

pot. Therefore, the effectiveness of a still for separating NdF3 from

a feed salt will gradually decrease, since the concentration of NdF3 in

the vapor will increase as the concentration of-NdF3 at the surface
increases. Relationships defining the extent of separation to be
expected with concentration polarization have been derived, and a method

for calculating R, the ratio of the concentration of NdF, in the vapor

3
to that in the liquid, is explained.

We will assume that the salt mixture in the still pot is composed
of only LiF and NdF3.
about 90% LiF, with the remainder being BeFZ, ZrF4, and NdF3.) Calcula-

(Actually, the steady-state composition will be

tions are simplified considerably for this assumed binary mixture.

Figure A-1 is a schematic diagram of the model used for estimating
the effect of concentration polarization. At any level, z, in the still

pot, the concentration of NdF_ is determined by the following equation:

3

. dc oN

_R _ __Rz , (10)
ot dz
where g = molar concentra;ion of NdF3:
N, = molar flux of NdF, in the z direction,
t = time. |
The_flux of NdFB, NRz’ is related to the concentration of NdF3 by the

following equation:

9X

R
Np, = XR(NRz + NLz) cD == (11)
 

 

 

 

40

ORNL DWG 67-11699

Vopor removal stream

. moles
Xg (1,0) =mole froctio! F —sec '
of rare-ecorth fluorid ot Xr (1,8) =mole fraction of

 

 

 

 

 

 

 

 

 

at liquid surface rare - earth fluoride
_\ ) in vapor ,
AAAAAAALLA z=L, g:l
L
2+ §
- 20, §=0

X (0,06) =mole fraction oi’X
rare-earth fluoride

moles
F sec

Xj=mole fraction of
rare~- ecrth flvoride
in feed siream

Fig. A-1. Diagram of Model Used for Estimating Effect of Concen-
tration Polarization. ,
 

 

&

 

41

where NLz = molar flux of LiF in the z direction,
Xp = mole fraction of NdF3,
¢ = molar density of mixture,
D = effective diffusivity of NdF, in an LiF-NdF, mixture.

3 3
Substituting Eq. (11) into Eq. (10) and dividing by the molar density,

¢, which is assumed to be constant, yields:

 

ox X 3 x
R _ _ . _R R
3t = v 3z + D 2 ’ (12)
3z
NRz + NRL :
where v = — < the velocity of salt mixture in the still pot.

Equation (12) must be solved with the following boundary conditions:
(1) At t =20, Xp = X = the initial NdF3 concentration, which
is equal to the feed composition.

(2) At z = 0, an NdF, balance over the boundary between the

_ 3
feed stream and the still pot gives:

ax

32 |,e0

v
= 2 [x (0, ©) —x,1 . (13)

(3) At z = L, an NdF, balance over the vapor-liquid interface

3

gives:

' v
wl_, T A ¥ x (L, t) , (14)

where a = the relative volatility of NdF3

with respect to LiF.

In deriving the third boundary condition, the following approximation

is used:
 

 

42

where YR is the mole fraction of NdF3 in the vapor phase.

This approximation is valid for a binary system in which the low-

volatility component is present at low concentrations.

Equation (12) and its associated boundary conditions can be put in

dimensionless form by making the following substitutions:

| Xp T X,
o = — = dimensionless NdF3 concentration,
i
g = g%- = dimensionless time, which is also equal to the number

of volumes processed by the still in time t (to see
this, multiply numerator and denominator by Ac’ the
cross section of the still),

Z . .
; £ = I = dimensionless distance.

With these substitutions, the differential equation and its boundary

conditions become:

oq d g o0
aa - 8 7o T TF (15)
] 352 £
6 =0: o=20, | (15a)
£ = 0: —3—% = bo (0, 6) , (15b)
leco
a0
£ = 1: e = ¢[o(l, 8) + 1] , - (15¢)
g=1
where a = ‘é%
b = 1/a,

c = (1—o)b.

¢
 

*

 

43

With the substitutions shown above, the quantity R described in Sect.

4.2 is given by:

 

 

 

 

OBS® "ACTUAL yR/XR(L, t) XR(avg) 1 L
= x (z, t) dz
L R
0
or
. xi[o(l, 8) + 1] [o(L, 8) + 1]
R=—"n =) (16)
X, I [o(g, 6) + 11dt avg
0
where
1
e = -
cavg( ) Jo o(g, 6) d§
Method of Solving Equations. — For the solution of Eq. (15), with
Egqs. [15(a)-15(c)] as boundary conditions, the parameters a, b, and c

are assumed to be constant.
By taking the Lapléce transform of Eqs. (15), and Egqs. [15(a)-15(c)],

the following ordinary differential equation and boundary conditions are

obtained:

 

2— -
d c(&é s) __ddég, s) —'s 0(E, ) =0 (17
dg
%2' = b 5(0, s) (17a)
| -
do T
a—g—_- = C O'(l, VS) + s °* (17b)
 

/

44

where o (£, s) = f;’ o(E, e)e'Se

and s = the Laplace transform variable. Equation (17) has the solution:

do, the Laplace transform of o(, 8),

oc(E, s) = Ae + Be , (18)
where
_ 1+ Y1l + 4as
51 2a »
_ 1 - V1 + 4as
Yo 2a *

When Eq. (18) is substituted into Eqs. [l17(a)] and [17(b)], the constants
A and B can be determined; then EYE, s) is found to be:

Yo8 Y,&
el(vy; —ble > = (v, —b)e = ]

o(E, s) = — . a9

Yo 1
S[(Yl - b)(wr2 —c)e " — (YZ —b)(v; — cle 7]

 

Since we also desire oavg (8) = 4} oc(t, 0) dg, we can find the Laplace
transform of this quantity by integrating Eq. (19) with respect to E.
This integration yields:
Y Y
2
21 = (1,2 = bre = D)

Yo Yy . (20)
SYlYZ[(Yl —b)(y, — ce " — (v, — b)(wr1 — c)e 7]

C[(le — by,)(e

 

E;vg(s) =

The quantity cavg(fl) is obtained from Eq. (20) by performing the following

integration in the complex plane:

1 et+ie 8
Uavg(e) = "2—“'{[ o (s)e

avg ds , (21)

€=

"
 

 

 

45

where i = v¥~1, and € > 0 and constant.

Equation (21) can be written in the following equivalent form by recog-

nizing that s = ¢ + iw and ds = idw:

ed [ |
oavg(e) 35;-I‘m Oan(E + iw)[cos (w8) + i sin (wbd)] dw . (22)

Because the integral in Eq. (22) converges to zero when 6 < 0 (ref. 9),

10

it can be shown™ that cavg(e) is given by a pair of equations:

 

 

0
_ 2e — .
cavg(e) == I: —Im[cavg(e + iw)] sin (w8) dw (23a)
9 £0 o _
oavg(e) = i_ IO Re[oavg(s + iw)] cos (wh) dw , (23b)

where
Im[gévg(e + iw)] = the imaginary part of the function o (e + iw),
Re[E- (e + iw)] = the real part of the function o (e + iw).
avg avg

Equation [23(a)] was chosen for evaluating cavg(e). The integral in this
equation was computed numerically by using the CDC 1604—A computer to
evaluate.Im[Eévg(e + iw)]. The details of the numerical integration can

be found in ref. 10.

The quantitj R is calculated by finding o(l, 6) and cavg(e) for the
~same value of 06 and substituting into Eq. (16). The quantity o(l, 8) is
found by inverting the transform givén by Eq. (19) with £ = 1, and the
quantity o avg (6) is found by inverting the transform given by Eq. (20).

The described inversion technique is requlred for both transforms.
 

 

46

10.2 Appendix B. Drawings Showing Poétoperational
Wall-Thickness and Dimensional Measurements

The drawings included in this appendix contain a complete tabulation
of the wall-thickness and dimensional measurements made immediately after
the still assembly was constructed and after the nonradioactive testing

of the equipment.was concluded.
47 :

 

 

SRaw 'D‘,- t-.u- e )
PL‘\N RU\NS " “l'.n P-.-Q—llnl-.-so &-T.

 

 

PLAN
S..
. ~ Ny
ax +— $us %

7\/\'!.1& \xu / o~
30° g
ot 4 <3°' ?‘E}_t/’( w

\ Yoo

"< PLAN Row "

*d3
Ry ~

]\‘ /
F K e ‘ML
T N Lo
L Loy + o AW s
. : ‘ +
\Kl o Ma
K2 l _
PLAN . ROW “BbAS

Row “A”" & Paiars & 45°
I Awamy On 2" Rap,Miasumen
Hosutouyauyt Frea Couan Of Huan
Rew “B" 12 Powrs @ %0°
APARY Om 4" RaD, MirtoniG
Horizoutarwy Fasw Coutea OF vdas

   
  
 
 
  
  

Row "¢~ & Points Asg

Srswn @AB® Ol &7 Rmo, i
Mueasunin HorizonTauly Faema :
Cantan’ O Hano !

 

PLANM OF STiILL HEAD

 

 

 

 

 

 

  

 

   
 
      
 
   
   
 

A
< X
— _'_x e Rl

PLA ROW “y "

_ +x1"f

30*

s d

 

 

  

 

 

 

 

ot
\l\( Ax 3°
9 N . \/
X3 8~—+ X6

PLAN ROWS “v" B "Z"

 

 

 

 

 

 

 

 

 

 

 

 

YA
’J\wl 10°*
;'m
WA
" wfl
i F
o~
n wy _4$
h '
o~
Axs 4 ~ 1% Pamore  Eauauiy Seazed |
1 $ ~ ALong Cirtumrgnanct OF
b ~ Rivipsa,,
4 T 3 ™~ Cimcum  * 33,933 10,
ve V1 r ~ Drvisens 5 Z.B2TS .
cq_) (uy L 24 3 ~ \ .
z1 2% B \
N\
~
~
N \
»
Arter,  FasmicaTion |u Commite \ \.\/+ ,_9\
[RAabiogrAPH Tris Seomam| Or ST . X
ok Waw. ANt HEAD Wirn Sursicieuy \ / \:/
Exrosvnge To Aotguatary MaP Cuting 5‘ .
Suaeace, Burwuen Weao Aun Seyvem .
Or Comican Biction, Access Far Rapio- \ /
AETIVE Sounce Can Be Maoe Tueu Newa'fF’. \ ) .
AT S O NeuRACIOACTIVE TAPERIMEWTS o4 X -
RapeaT Tue Racwcharuy Discrinso Ated. ““--.___ml_ \ / /
. \ Xa,
NOTES 5 .’,\ /
1. Dumise Fasmeantion Mawg Dm“Lva‘KN‘“ MEASUME M ENT S AN - X\,
A% Powte Denanaten By "X In Uvrem Lgry Connen, OF . ) '}i\_._q-," \
2 ‘;D\QIZ'(F\M\TM\." C.:‘\.-UMHN.\ o N N
RN ABRICAT IO AWK EAGUREMENT & TRASouICALLY T .
Foates OXsiznaTan |u Thg TAmuwatens On Dwes. MI2LT73-£D-026D PLAN  Rowd "' e, “y*
Ao MILITHE0-0TI0 Cravrert Trose Mamxad ''Na Myasoagraants
Recomns RosuuTs ln ArPpetriats Llowvmn,
3. Pomts AT WwicH MuAsuasmuni (s Ard Mave ARC IDENTICED
Bv A Latren (A0, -, 2) To Iumeate Tan Rew . Ann A Nowaan Tambriation - Deimoons, G Rame sasruions Meawammats MIZITI-CO~ OO
(\ T,o-2 2 Te Snow Positions On Thig Roiv, L - N Tans o - o« o
4. bewiielcations ta  Pamiwtuesis [ eq. (P12), C@%); Ere. J Inoicate scavien -Luenr Merwaenants f Tamnamies Oam
Tuar Pewt |s Dimgeyuy Crrosite Tua Duspiaves &mnr. REFERENCE DRAWINGS NO.
Deverer UvtnAsorne Tuicuness Measvmameny Procgours During
FAmmicaTs Wiien Wice Protues T Samd  Thickuits MeasomiwiaTs 0AK RIDGE NATIONAL LABORATORY
Ae Tuose Feuwt Dimdctuy AT PoinTs DengnATEd , NorTk | Amevt, OPERATER BY
Recwono Proctoure Precisauy.
€. Avtei NenmADIOACTIVE EXPERMENTS, Maxe UnTangems Thickuass UNION CARBIDE NUCLEAR COMPANY
MuArume merats As tn Kot 2 Ameva Aun Rzcons Resucts in, DIVISION OF UNION CARBIDE CORPORATION
Avrrorratre Cowumn, . OAK IDGE, TENNESSEE
T STATE Twicknois Moadunrusuts n Diomacs . STATe Aw OTnem
MEAWREMEITS W lucnuss Anos Fracmiows, . agal
8 Artcr FApmcames, Raowosmatn Whiw Surmciguy Exnpsgurxs To l#l“m;‘e DIMENSIONS UNLESS | jqmE DASTILLATION EXPERIMENT ufl%‘ & 71509
CarmapileTuy  MAR 'V:fl-.\-é Wate Batwadn W=\£ \.\utc‘\‘\ Serress SPECIFED: .
Or Lnigaw SEctien OF Tt Aun Rew " G ConbEneaN. FRACTIONS + Locationss OF Poisxs Fom Duisuiiaiar Aus
Apqar MonmaowAGIVE Sxraruaints, Rinrtar Tar Racwocmacuy, _— Raoiocmaprie Medtwnamants, On, St Awe
DECIMALS £ e Covnansenm Astemeiy
ANGLES £ | e . LAPF
ScuLE: Nons MIZI73

 

 

 

 

 

 

 

 

APRTYEL EQR CONSTRGETON '

 

 

 
 

48

WALL THICKNESS AND ORSERVATIONS ‘ WALL MEASUREMENTS AND ‘ WALL THICKNESS MEASUREMENTS AND OBSERVATIONS .

LOr | ma | nmac Peanct | MTCAND s o O™ | INaL | iimac | orerations | Cmaiae AND REMARKS OO N | et | maL]on Do L | RADIOGEARNY, QMEAVATIONS,
MEASUREMENT | (inches) (Inches) Gnches) MEASLIREMENT | (lnchei) | (nches) |~ (nches) | (inches ~
i . -, - NR -
Al G . . —_
A G38 P2 —
At - ‘ P2 -
B 10 P
8 1l Ps
B3 2 P&
B4 - al . ‘ Pt
8§ Ht P8
: H3 : : 7o
B? . 4 ‘ ' Pl
8 us ;
Hé
H1
He
HS

OAK RIDGE NATIONAL LABORATORY
OPERATED &Y
UnioN CARBIDE NUCLEAR COMPANY
DIVISION OF UNION CARBIDE CORPORATION
OAK TENNESSEE

BLDG.
MSIRE  DISTILLATION EXPERIMEWT 0. B Yoo

Tagueafiow OF Data Frev Dimtwsaoad
AN Rasioararmi, MeAsuRemiEnts ON- ST
Anp ConbBEnscr Asttmiuy : .

LILLTS FMENSIONS

MTIAL DIMENSIONS MIZI73 020 -

 

 

 

g ey i e g,

 

 

 
'“]

 

 

LOCATION
OF

13

DIRECY
HNITIAL

CHANGE

WALL THICKNESS MEASUREMENTS AND OBSERVATIONS

RADIOGRAPHY, OBSERVATIONS,
~ AND REMARKS

LOCATION
OF

YIZ
Tl
e
i3

T5
6

WALL THICKNESS MEASUREMENTS

‘DIRECT
INITIAL | INITIAL | OPERATION

 

 

 

 

 

 

DIMENSIONAL
CHANGE
(Inches)

1

1

OBSERVATIONS

RADIOGRAPHY,

AND RE|

4 Byrjens @ Ea. Peritien
Seazad 90° Awany

OBSERVATIONS,
MARKS

 

 

 

 

LENGTH AND "MEASUREMENTS
Caimeas, | post
o | ASBUILT | OPERATION
LENGTH | LENGTH REMARKS

Firk Cmowns Fuat Te
APPROKMATIN " D,
Awn  CouterPuncw

A
Maxe Bugyews By FOSIYING (Wu.puug)
Hast eaney X Weup Matar Ow Surraces,
FAyues 28 Wao R 14 Aw AcsiPganLc
SUBSTITVTE .

»Dimengova. &

. “

Measuagrad iy >

" = pleD
NO.

REFERENCE DRAWINGS

y

OAX RIDGE NATIONAL LABORATORY

TED BY
UNION CARBIDE NUCLEAR COMPANY
DIVISION OF UNION CARBIDE CORPORATION
0AK TENNESSEE
) 1541
MIRE  DHATILATION  EXPRERIMENT o %1504
LacaTiem OF Porys Fom LimZAMm MEASURIMEINTS

Ane Tagunatiers Or Dagxa Fom Stw Conosustf=
Recewna  Assumuny

12\

 

 
 

)

-

 

 

 

 
 

 

 

 

 

51

ORNL-4434
UC-80 - Reactor Technology

INTERNAL DISTRIBUTION

1-3., Central Research Library 83. R. H. Guymon
4. ORNL — Y-12 Technical Library 84. B. A. Hannaford
Document Reference Section 85. P. H. Harley
5-39. Laboratory Records Department 86. P. N. Haubenreich
40. Laboratory Records, ORNL R.C. 87. R. F. Hibbs
41-42, MSRP Director's Office 88-89. J. R. Hightower
Bldg. 9201-3 Rm. 109 90. H. W. Hoffman
43, R. K. Adams 91. R. W. Horton
44, G. M. Adamson 92. W. H. Jordan
45. J. L. Anderson 93. P. R. Kasten
46. C. F. Baes 94. C. W. Kee
47. C. E. Bamberger 95. M. J. Kelly
48. C. J. Barton 96. S. S. Kirslis
49. H. F. Bauman 97. J. W. Koger
50. S. E. Beall 98. R. B. Korsmeyer
51. M. J. Bell 99. A. I. Krakoviak
52. E. S. Bettis 100. T. S. Kress
53. R. E. Blanco 101. C. E. Lamb
54. F. F. Blankenship 102, J. A. Lane
55. J. 0. Blomeke : 103. J. J. Lawrence
56. R. Blumberg 104. M. S. Lin
57. E. G. Bohlmann 105. R. B. Lindauer
58. G. E. Boyd 106. A. P. Litman
59. J. Braunstein 107. M. I. Lundin
60. M. A, Bredig 108. H. G. MacPherson
61. R. B. Briggs 109. R. E. MacPherson
62. S. Cantor 110. J. C. Mailen
63. W. L. Carter 111. H. E. McCoy
64. G. I. Cathers 112, L. E. McNeese
65. J. M. Chandler 113. A. S. Meyer
66. H. D. Cochran _ 114. R. L. Moore
67. E. L. Compere 115. D. M. Moulton
68. W. H. Cook 116. J. P. Nichols
69. B. Cox 117. E. L. Nicholson
70. C. W. Craven 118. A. M. Perry
71. F. L. Culler ‘ 119, J. L. Redford
72. J. H. DeVan 120. G. D. Robbins
73. S. J. Ditto 121. K. A. Romberger
74. W, P. Eatherly 122, W. F. Schaffer
75. J. R. Engel 123, C. E. Schilling
76. D. E. Ferguson 124, Dunlap Scott
77. L. M. Ferris 125. J. H. Shaffer
78. A. P. Fraas 126. M. J. Skinner
79. H. A, Friedman 127. A. N. Smith
80. J. H. Gibbons 128, F. J. Smith
8l. W. R. Grimes 129. D. A. Sundberg
82. A. G. Grindell 130. R. E. Thoma
 

 

131.
132.
133.
134,
135.
136.
137.
138,

146.
147,
148.
149-150.
151.
152,
153.
154,
155-374.

C.

2HRARZ>

J.

52

-~

P. Tung 139. Gale Young

E. Unger 140. E. L. Youngblood

M. Watson 141. P. H. Emmett (consultant)
S. Watson 142, J. J. Katz (consultant)

M. Weinberg 143. J. L. Margrave (consultant)
R. Weir 144, E. A. Mason (consultant)

E. Whatley 145. R. B. Richards (consultant)
C. White

EXTERNAL DISTRIBUTION

Giambusso, Atomic Energy Commission, Washington, D.C.
Haberman, Atomic Energy Commission, Washington, D.C.

0. Laughon, RDT Site Office, Oak Ridge National Laboratory
W. McIntosh, Atomic Energy Commission, Washington, D.C.
Shaw, Atomic Energy Commission, Washington, D.C.

A. Swartout, Union Carbide Corporation, New York 10017

Patent Office, Atomic Energy Commission, ORO
Laboratory and University Division, AEC, ORO

Given distribution as shown in TID-4500 under Reactor Technology

category (25 copies — NTIS)