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LAMS-2832

LOS ALAMOS SCIENTIFIC LABORATORY

OF THEUNIVERSITYOF CALIFORNIAo LOSALAMOS NEW MEXICO

THE VOLUBILITY OF SELECTED ELEMENTS

IN LIQUID PLUTONIUM

I. CARBON

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LAMS-2832

UC -4, CHEMISTRY

TID-4500 (18th Ed. )

LOS ALAMOS SCIENTIFIC LABORATORY

OF THE UNIVERSITYOF CALIFORNIA LOS ALAMOS NEW MEXICO

REPORT WRITTEN: December 18, 1962

REPORT DISTRIBUTED: February 19, 1963

THE VOLUBILITY OF SELECTED ELEMENTS

IN LIQUID PLUTONIUM

I. CARBON

by

D. F. Bowersox

J. A. Leary

Contract W-7405-E NG. 36 with the U. S. Atomic Energy Commission

All JAMS reports are informal documents, usually prepared for a special purpose and primarily prepared for use within the Labmatory rather than for

general distribution. This report hae net been edited, reviewed, or vertfIed

for accuracy. All LAMS reports express the views of the authore ae of the

time they were written and do nat necesearlly reflect the opinions of the Los

Alamos Scientific Laboratory or the final opinion of the autbora on the aubj ect.

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ABSTRACT

The volubility of carbon in liquid plutonium has been measured over

the temperature range 700°-9500C. The volubility increases from 690 ppm

(by weight) c at 700° to 2350 ppm C at 950”C. The data fit the empericsl

equation

log Nc = 0.50-2.30 X 103 T-=,

where Nc is the mole fraction of C and T is the temperature in degrees

Kelvin.

ACKNOWLEDGW~S

The authors wish to thank A. E. Ogard for furnishing the PuC used

in this study. We are slso indebted for the chemical analyses which

were done by the Analytical Chemistry Group under C. F. Metz.
INTRODUCTION

The solubilities of sparingly-soluble elements in liquid plutonium

generally have not been measured. In order to make meaningful measurements, the liquid plutonium must be free from impurities that interact

in solution with the impurity element. Now that high purity plutonium

has become available in quantity, such measurements are possible.

Experiments are programmed to determine the solubilities of selected

solid elements and compounds in liquid plutonium over the temperature

range of 650 to approximately KXIOoC. ‘JTELSreport summarizes the results obtained with carbon.

ExP~

Materials

Electrorefined Puwas used in sXl experiments. The procedure for

preparing this materisl has been described.(1) Analysis of the I?uis

shown in Table 1. Type AUC graphite was used for the crucible and the

3
stopper rod. Plutonium monocarbide was

of the elements in an arc furnace.(2)

Table 1

prepared by direct combination

-Sis of Electrorefined Pu

Spectrochemical

Element

Li

Be

Na

m

Ca

Al

La

Si

Pb

Cu

Cr

Mn

Sn

Bi

co

Y

<0.2

<0.1

ao

<5

ao

<5

ao

40

<2

ao

ao

<2

<1

<1

ao

<5

(1)Typical analysis

for these elements.

of electrorefined

Procedure

chemical

Element

Am 15

Fe <20

JAI 99.91?$

B < 0.5

Ni <20

u <30

Th <15

cl- <10

Ta <30

I’/ 15*5

Mo

c(l)

~(l)

=(1)

0(1)

<5

<10

5~3

5*5

20-50

Pu. This sample was not analyzed

The reaction vessel and equipment utilized in this study are

similsr to others used in quenching experiments. (3) This apparatus was

4
designed so that Pu could be contacted with C in a graphite crucible

for a selected time and then quenched by pouring the melt into a cold

casting block under vacuum or in an inert atmosphere. Typical.experiments were made by the following procedure: the apparatus, with no Pu

in it, was outgassed for 1 hr under vacuum at 500”C and cooled to room

temperature. The tapered end of the graphite stopper rod was then

inserted in the casting hole in the graphite reaction crucible and 50 g

of Pu were placed in the crucible. The apparatus was re-assenibledand

evacuated to less than 0.2v pressure. The tube was heated to the

selected temperature emd maintained at temperature for the desired ttie.

The tube was shaken at 10-15 min intervals at temperature to agitate

the liquid.

Argon gas was then introduced and the stopper rod was raised.

Liquid Pu poured rapidly through the casting hole into the magnesia

pour’crucible end into the cold Cu casting mold. The vessel was cooled

to rocmltemperature under vacuum and then disassembled.

In most cases castings were fox?nedboth in the Cumold and in the

pour crucible. The compositions of these castings were identical and

homogeneous. samples were broken from the centers of both of the

castings under a He atmosphere and submitted for C analysis. Volubility

measurements were based on results of analysis of two semples fran each

quenching experiment. The agreement was well.within the limits of error

of the method of analysis.

The castings, si’tersampling, were re-used in the next equilibration.
The estimated standard deviation of the C analysis is t 10 relative

percent}’) In this study variations were, in general.,small. Errors

due to temperature deviations during quenching were estimated as less

than 2 percent in the volubility determination. There was no evidence

of inclusion of C particles in the castings after 1 hr of equilibration.

RESULTS

Several series of tests were made to demonstrate that equilibrium

conditions were met between the liquid and solid phases. Time-dependence

tests were made at each temperature. Those at 800” and 850”c, which

were typicsl, are summa—ized in Table 2. As shown, the volubility of

C in Puwas independent of time after 1.5 hr at 800”c and after 1.0 hr

at 850°c.

Table 2

The Solubili@ of C in Pu as a Function of Time

Temperature, Time at Temperature,

‘c hr

800 O*5

1.0

1.5

850

2.0

2.5

3.0

1.0

2.5

3.5

4.0

Volubility,

Pm c

Segregated

965

11oo

SL50

11oo

1150

1400

1300

1400

1400
Equilibrium conditions were

temperatures, and no significant

For exsmple, equilibrations were

approached from both higher and lower

change in volubility was indicated.

made at 700°C by approaching this

temperature from lower temperatures. In addition, eqtililmations were

made by first equilibrating for 2.0 hr at 8000C, then cooling to 700°C

and

the

was

re-equilibrating for 3.0 hr prior to qyenching. In both experiments

volubility vslue was well.within

0.7$.

the experimental error; the difference

Another approach to equilibrium that was employed was to contact

an excess of C as solid PuC with liquid Pu in a MgO crucible and with a

MgO stopper rod. At 8000C after

quenching, the C content was the

a 2.5 hr period of contact prior to

same as when liquid Fu was contacted

with graphite. There was no reaction between the FuC-PU and the MgO

crucibles after 2.5 hr at 8000C.

Volubility Measurements

The results of the volubility experiments are shown in Table 3.

These measurements were made after equilibrating frm 1.5 to ~.O hr at

temperature prior to quenching. Measurements at 640”c, in which

equilibrium conditions might not be met (m. pt. Pu is 639°C) averaged

385 ppm, which is in agreement with the other data.

A solid phase formed upon-the inside walls of the graphite crucible

during these Pu contacts. Samples of this phase contained 94 * 1% Pu

and 3.1-4.3? C by chemical analysis. ltromthe Pu-C binary phase

~wm}5) this solid probably was hypostoichiometric PuC.
Table 3

The Volubility of C in I% as a Function of Temperature

Temperature,

“c Experiment No.

700

750

800

850

900

950

1

2

3

Ave.

1

2

3

Ave.

1

2

3

4

5

Ave.

1

2

3

4

Ave.

1

2

3

Ave.

1

2

Ave.

Solub“1“ty,

?i Pm 1

690

715

“665

690

835

795

830

82o

11.oo

1300

U50

11.oo

23.50

u60

1400

1300

1400

1400

1375

1900

1750

1900

1850

2200

2500

2350

Cs2%on

Mole Fraction

Nc X 103

13.6

14.0

13.1

13.6

16.4

15.6

16.3

16,1

21.4

25.2

22.4.

21.4

22.4

22.6

27.1

25.2

27.1

27.1

26.7

36.5

33.7

36.5

35.7

42.0

47.4

44.7

(d Parts per million parts Pu, by weight.

8
DISCUSSION

From the phase diagrsm,(5) the volubility of C in liquid Pu

throughout this temperature range probably corresponds to the equilibrium:

lhC ( solid) = PuC (saturated solution in Pu). (1)

At constant pressure it can be shown that, by thermodynamic considerations,

a plot of log NC vs l/T should be linem? if AH is constant over this

temperature range. The aversge volubility data from Table 3 are plotted

as a function of l/T in Fig. 1. The data fit the empirical equation

log NC = B + JW-l, (d

where Nc is the volubility of hypostoichiometric PuC expressed as the

mole fraction in solution snd T is in degrees Kelvin. l?romleast

squsres fit, this equation is

log Nc = 0.50-2.30 x 103 ‘r-=.

The standard error of estimate is 0.1

(3)

9
100

80

60

40

20

m

+

Z“

10

6

4

2

I

●

✎✌

I

0.8 0.9 1.0 1.1

I/T X 103 (0 K-’)

Fig. 1. Plot of log NC vs l/T

10
IiEFEmNcEs

1. L. J. MuDins, J. A. Leary, A. N. Morgan, and W. J. Maraman,

“plutonium Electrorefining,” LA-2666 (1962).

2. A. E. Og~d, C. C. Land, and J. A. Leary, “The Thermal Expsnsion of

PuC and PuC-UC Solid Solution,” LA-2768 (October 1962).

3. L. J. Mullins, J. A. Leary, amd K.W.R. Johnson, “Remmml of Fission

Product Elements from Plutonium by Liquation” from Extractive and

Physical Metallurgy of Plutonium and its Alloys, W. D. Wilkinson, cd.,

Interscience, N.Y. (1960) p. 101.

4. W. G. Smiley, “A New Micro Combustion Method for Carbon in Plutonium,”

IA-IJ28 (1950).

5. R.N.R. Mulford, F. H. ElLinger, G. S. Hendrix, andE. D. A1.brecht,

“The Plutonium-Carbon System,” from Plutonium 1960; E. Grison, W.H.B.

Lord and R. D. Fowler, editors, Cleaver-Hume Press Ltd., London (1960)

p. 301.

u.