LAMS-2952

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CIG14 REPORT (XX1ECTION

FIEPF?oE’mYrK)N

COPY

LOS ALAMOS SCIENTIFIC LABORATORY

OF THEUNIVERSITYOF CALIFORNIAo LOSALAMOS NEW MEXICO

THE VOLUBILITY OF SELECTED ELEMENTS

IN LIQUID PLUTONIUM

IL TANTALUM

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LEGAL NOTICE

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LAMs-2952

UC -4, CHEMISTRY

TID-4500 (21st Ed.)

LOS ALAMOS SCIENTIFIC LABORATORY

OFTHEUNIVERSITYOFCALIFORNIALOSALAMOS NEWMEXICO

REPORT WRITTEN: July 18, 1963

REPORT DISTRIBUTED: September 27, 1963

THE VOLUBILITY OF SELECTED ELEMENTS

IN LIQUID PLUTONIUM

n. TANTALUM

by

D. F. Bowersox

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F— for accuracy. Aii LAMS reports exprese the views of tbe authors as of the

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a time they were written end do not necessarily reflect the opinions of tbe Los

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Alamos Scientific Laboratory or the ffnai opinion of the authors on the subject.

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1

I
Abstract

The volubility of tantalum in liquid plutonium has been

measured over the

increases from 45

1000°c. The data

temperature range 700° to 1000°C. The volubility

ppm (by weight) Ta at 750° to 1070 ppm Ta at

fit the emperical equation

log Nm =3.06 - 7.50 X103 T-Z,

‘here‘Ta is the volubility of Ta expressed as the mole fraction and

T is the temperature in degrees Kelvin.

Acknowledgements

The author is indebted to the Analytical.Chemistry Group under C. F.

Metz for the chanicsl snslysis as we13.as to J. A. Leary for suggesting

the problem and helpful.discussions during the course oi’the work.

2
The solubilities of the

INTRODUCTION

slightly soluble elements,

approximately 1 per cent by weight, in liquid plutonium

studied in the laboratory.(1) The availability of high

has made possible measurements that are not sffectedby

impurity elements.

up to

are being

purity plutonium

interaction with

This report summarizes the investigation of the volubility of

tantalum over the temperature range 700° to 1000”C. Jones, Ofte, Rohr

and Wittenber$2) reported no evidence of Ta volubility over the temperature range 645° to 950”C. during a study of the viscosity and density of

Pu in this temperature range. ( Schonfeld 3), however, has predicted

that Ta should be appreciably soluble in this range. This study

demonstratedthat Ta is, indeed, sparingly soluble in liquid Pu.
Electrorefined plutonium (4)

was used throughout this investigation.

Analysis

tantalum

of the plutonium is shown in Table 1. The amilysis of the

that was employed for this investigation is given in Table 2.

In both cases the impurities

metals are essentially pure.

are minor or not detectable; hence the

Table 1

Analysis of Electrorefined Pu

Spectrochemical Chemical

Element E3_ement

Li < 0.2 Am

Be < 0.1 Fe

Na <10 l%

m <5

Ca <10 B

Al <5 Ni

La <10 u

Si <10 Th

l% <2 clCu <10 Ta

Cr <10

Mn <2 w

Sn <1 140

Bi <1 ~a

co <10 I@

Y <5 *

Oa

15

<20

99.9@

< 0.5

<20

< 30

<15

<10

<30

1525

<5

<10

5*3

555

5-20

%ieti - ys.1s of electrorefined l%. This

sample was not analyzed for these elements.

4
Table 2

Anslysis of Ta

Be ND Mn

Na ND Fe

m <10 Ce

Al ND Ni

Si <10 Cu

K ND Zn

Ca ND Sr

Ti ND Zr

v ND m

<10

d-oo

ND

aoo

aoo

ND

ND

aoo

aoo

Element

Mo

&

Cd

Sn

Ba

Hf

Ta

w

l%

Bi

2!.

ND

ND

ND

ND

ND

Major

ND

ND

ND

% is not detected.

The reaction vessels and enclosing furnace tubes were similar to

those commonly employed in quenching studies(5). In several experiments a stainless steel furnace tube with either a quartz or tantalum

liner was used. Pu was contacted at a selected temperature for a

given time interval with a coupon of Ta in a Mg casting crucible, and

then quenched by pouring the melt into a cold casting block. In some

experiments, the liquid Pu wascontactedtitha Ta cont~nercrucible

and then rapidly cooled to room temperature.

Typicsl experiments were made by the following procedure.

Initislly the apparatus, complete except that no Pu was in the reaction

crucible, was outgassed under vacuum at 900°C. until the pressure was

less than 4 X 10-5 Torr. Then, titer cooling, approximately 50~. of

I?uwas placed in the reaction crucible and the apparatus was evacuated

and heated to the selected temperature. During the timed interval at

this temperature the entire furnace tube was shaken by means of an

external vibrator in order to agitate the liquid FL

5
Ssmples were broken from the cooled castings (or melts) and

submitted for analysis. These were homogeneous, and the two methods

appeared to give equivalent results. The castings (or melts) were

reused in subsequent volubility measurements.

RESULTS AND CONCLUSIONS

Experiments were made to determine the time required to reach

equilibrium between the solid (Ta) phase and the liquid (Pu) phase at

each temperature. It was found that Ta was not detected in the castings

for intervals of up to 20 hours, and that this time interval decreased

with increased temperature. The time dependence experiments at 850°c.,

which were typics3 of tbe study, are summarized in Table 3. In this

case no Ta was detected at 22.0 hr. or less at temperature. The

volubility was independent of time after 44.0 hr. at temperature.

Table 3

The Volubility of Ta in Pu as a Function of Time at 850”c.

Totsl Time at 850”,

hours

1.0

2::

16.0

22.0

44.0

Volubility,

PPm Ta

< 50

< 35

< 35

< 35

< 50

220

66.0 210

88.0 215

Kl_2.o 195

158.0 205

187.0 ZL5

6
Volubility measurements were made by several.

to check that equilibrium criteria had been met.

direct approach from lower temperatures, castings

approaches in order

In additionto the

were reused after

quenching from a higher temperature. In other cases a melt washeld

up to 24 hr. at a higher temperature and then cooled to the temperature

selected for study. These approaches caused no significant changes

in the measured volubility vslues at these temperatures.

The vslues obtained from these volubility measurements are shown

in tabular form in Table 4. These measurements were made with several

different castings of Pu, but each casting was from the same lot that

had been analyzed (see Table 1). The average solubil.ityvalue at each

temperature is we12 within the range that would be expected due to

the analytical and experimental errors inherent in this system.

The average volubility data from Table 4 are plotted, as the mole

fraction, as a function of l/T in Fig. 1. The data fit the emperic&l

eqmtion

log NTa = B i-~-1, (1)

‘fhere‘Ta is the volubility of Ta expressed as the mole fraction and T

is the temperature in degrees Kelvin. From least squares treatient,

this equation can be expressed as

log ~JTa= 3.06 - 7.50 X 10s T-l.

These data fit this equation qtite well.
Table 4

The Volubility of Ta in Pu as a Function of Temperature

Temperature, Hours at Solubil”t ,

tY

Mole Ihction T+

‘c. Temperature ppm Ta a ‘Ta x 104

700 97.0 < 35 ----

750 24.0 45 0.59

800 15.5 85 l.lz?

18.0 85 1.12

65.5 80 1.06

A@. 83 1.10

850 44.0 220 2.90

66.0 ao 2.77

88.0 23.5 2.84

IJ2.O 195 2.57

158.0 205 2.70

215.0 215 ,2.84

Avg. 210 2.77

16.0 375 4.95

385 5.o8

$:: 385 5.08

88.0 380 5.01

Avg. 381 5.03

950 16.0 520 6.86

40.0 620 8.19

72.0 520 6.86

Avg. 550 7.26

1000 68.0 1070 14.1.1

(a) Parts per million parts Pu, by weight.
I0:

I02

I

—

—

—

—

0.8 i.0 LI

1/;:103 (“K-’)

Fig. 1. Plot of log NTA vs. l/T.
References

1. D. F. Bowersox and J. A. Leary, “The Volubility of Selected Elements

in Liquid Plutonium I. Carbon”, LAMS-2832 (1963).

2. L. V. Jones, D. Ofte, W. G. Rohr, and L. J. Wittenberg, Trans. of

the ASM, ~, 819-825 (1962).

3. F. W. Schonfeld, “Plutonium Phase Diagrams Studied at Los Alsmos”,

from The Metsl Plutonium, ed. by A. S. Coffinberry and W. N. Miner, .—

University of Chicago, Chicago, Illinois, 1961, pp 240-254.

J. L. J. Mullins, J. A. Leary, A. N. Morgan andW. J. Ikmman, “Plutonium

Electrorefining”, LA-2666 (1962).

5* L. J. 14uUins, J. A. Leayy and K. W. R. Johnson, “Removal of Fission

Product Elements from Plutonium by Liquation”, from Extractive and

QllYQ@ ~~t~”= .of Plutonium —and —its Alloys, W. D. Wilkinson,

ed.,Interscience, N. Y. (1960), pp. 101.

XL