UNCLASSIFIED. ' LAMS-UWO

LOS ALAMOS SCIENTIFIC LABORATORY

of

THE UNIVERSITY OF CALIFORNIA

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25, D. C.

March 15, 1950

^ S S S S S U i

OF SOME PLUTONIUM-ALUMINUM ALLOYS

* g g jC flB I IB Rogort wrlttin by:

Robert B. Gitaey Robert B. Gibney

Thomas A. Sandenaw

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UNCLASSIFIED

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ABSTRACT

The thermal and electrical conductivities of a 

• • r ite of Pu Al alloy* have been determined in the 

ran«e O^U atomic percent Pu. The conductivities 

are approximately proportional to the volume of free 

aluminum.

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M n AN 1 1957 (%

For 1H* Atomic E’w g j C*mmt»»ion

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ae eee e • • i ; < i ? i > 2 -
PRELIMINARY REPORT ON THERMAL AND ELECTRICAL CONDUCTIVTnEl 

OP SOME PLUTONIUM •ALUMINUM ALLOYS

INTRODUCTION

Since t knowledge of Uw thermal conductivity of plutonium-aluminum alloys, in 

the low-plutonium end of the system, has become desirable, t simple apparatus has 

been built for the measurement of thermal conductivity of rods 0.24 Inch la diameter 

aad approximately 4 Inches loaf. A lack of homogeneity in the extruded specimens 

has prompted the measurement of electrical conductivity of short intervals of Uw rode, 

so that Uw nonhomoftneous parts could be definitely located. Chemical analyses have 

been made of the various portions of each specimen.

4

METHOD

The electrical conductivity was measured by mean* of a precision Kelvin bridge. 

The potential probes were scalpel blades accurately positioned 1.00-cm apart.

These could be moved along the rod so that the resistance of a one-cm length could 

be determined at intervals. The diameter of the rod via determined at Uw center 

of each Interval.

The thermal conductivity was determined by measuring the thsrmnl gradient of 

two Intervals, 1 Inch and LS inches, respectively, in the middle of the 4-lnch specimens while one end was kept at 0°C and the other was heated by a direct-current 

heater to about 25° -30°C. The electrical power was measured by a Type K-S 

potentiometer.

Surrounding the rod was a 1.5-inch diameter stainless steel tube with heaters 

top and bottom. This was soldered to the same heat sink, a copper block cooled by 

Rowing water from a 0°C bath. Three thermocouples on this shield, with Uw two 

hesters, enabled matching of the temperature gradient in Uw shield to that of Uw 

rod, so that no heat was lost by radiation. The top of the stainless steel tube ended 

In a flange connection to a vacuum system, and all measurements were mads at t 

pressure of about one micron.

The top flange and the copper tube leading to the vacuum system were wound 

with real stance wire no that they could be kept at the same temperature as Uw heater 

cap for the rod; thus all of the energy put into Uw heater vent down Uw rod.

The specimen made contact with the heater cap and Uw heat sink by means of 

tapered ends fitting Into tapered holes. The measuring thermocouples were soldered 

through Kovar-glass seals, soldered Into the stainless steel tube. Thermal contact 

was made by pulling the hot Junction ’bend against the specimen and soldering Uw leads 

Into the Kovar tubes. Chromel P and aiumel wires 0.005 inch in diameter were used.

DISCUSSION O F RESULTS

The nominal 10 atomic percent plutonium rod, vhich was cast 1/2 inch in diameter and machined to 0.357 inch diameter, was very nonuniform. This inhomogeneity was checked both electrically by probing, and thermally by reversing Uw rod, 

end-for-end, in subsequent experiments. Also a radiograph showed these inhomogeneltles. Figure 1 shows the radiograph of this specimen with locations of analytical 

samples. Also Is plotted the electrical conductivity of 1.00 cm lengths against the 

midpoint of each Interval. The average thermal conductivity for two sections la 

indicated.

The nominal 5 atomic percent plutonium rod was extruded. This had a region 

of high electrical resistance, but very little of this region fell inside the region

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surveyed (or thermal conductivity ( mm Fig. I ). The radiograph of this rod Is also 

given la fig . 2.

The nominal l.l atomic percent plutonium rod, alao extruded, « u quite uniform In electrical and thermal conductivities (Fig. 2). The extruded pure aluminum 

rod (99.99 ♦ % Al) wax alao quite uniform. However, one regftoa wax scored badly 

In extruding, and it was difficult to get good thermal contact to the thermocouple 

Junction at this point.

A plot of thermal conductivity kgalnst electrical conductivity gives a straight 

line, within the limits of error of the experiments, with the same slope aa the line

K • 5.01 o T s 10® ♦ 0.03

where

K • thermal conductivity cal/em °C sec ,

9 m electrical conductivity ( ohm*1 cm’*) ,

T • absolute temperature ,

which was used by C. 8. Smith to define the relationship between electrical and thermal 

conductivities for a large number of aluminum alloys ( Fig. 4). The data would ba 

fitted somewhat better by a change of the Intercept to 0.08, making the equation

K . 5.02 oTxlO’9 4 0.08

The radiograpos alao verify the results found for electrical and thermal conductivity. The darkest sections In the radiograph Indicate highest plutonium content, and 

these sections of the rod also show the lowest electrical (and therm al) conductivity.

Figure 6 is a plot of thermal conductivity vs. atomic percent plutonium. The 

last two points are both from the 10 atomic percent rod. The analytical results from 

locations Nos. 2 and 3 were used with the two different therm al conductivities found 

for those same areas.

These alloys were preptred tor us by F. W. Schonfeld and bis group. The radiograph was taken by 0 . H. Tenney.

CONCLUSIONS

The thermal and electrical conductivities of some plutonium-aluminum alloy a, 

up to 10 atomic percent plutonium, have been determined. Assuming that the compound PuAlj is a nonconductor, the conductivity la roughly proportional to the amount 

of residual aluminum. The ratio of thermal conductivity to electrical conductivity la 

approximately constant over the range of compositions studied.

TABUS 1

THERMAL CONDUCTIVITY

Nominal

Atomic Percent Pu

Avg. Atomic Percent 

Measured

K

( cal/cm °C sec)

0 0 0.88

1.8 1.39 0.83

8.0 8.42 0.47

10.0 10.96 0.21-0.38

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5? 9 f -

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TABLE 0

ELECTRICAL CONDUCTIVITY

N om inal

A tom ic P t r c e n t Pu

Location oI C e n ttv o f I n U r n i 

(cm)

m i o ’

(o h m )

• *

(ohm*1 cm ' )

0 1.0 01.0 3 34

2.21 90.0 3.61

3.54 89.0 3 00

4 .0 1 90.0 3.57

0.04 •6.6 2.63

7 0 S 66.6 3.61

• 01 66.6 M O

3.60 at* .

L I 1.00 90.3 3.23

3. IT 90.9 3.23

4.44 92.4 3.22

3.71 91.1 3.21

0.08 90.3 3.24

0.13 90.0 3.33

0.51 90.0 3.16

3.23 avg.

5 .0 1.77 110.3 2.73

3.04 117.6 1.74

4.31 117.0 3.76

3.58 116.1 3.79

6.01 116.2 1.74

0.12 136.0 2.38

0 4 9 136.0 2.03

10.06 130.0 2.12

10 0.03 402.0 0.74

'.00 260.2 1.11

3. IT 245.0 1.22

4.44 260 1.11

3.71 232 1.30

6.06 176 1.71

6.33 183 1.63

TABLE m

THEIIMAL CONDUCTIVITY-ELECTRICAL CONDUCTIVITY

Specimen

9 X 19** 

(ohm*1 cm*1)

K

( cal/cm °C me)

Aluminum 3.60 0.36

1.39 Atomic Pu (Avg.) 3.22 0.33

3.18 Atomic Pu (Avg.) 2.77 0.47

10.36 Atomic Pu 1.46 0.26

1L92 Atomic Pu 1.16 0.31

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SAMP LX COMPOSITION (MATERIAL DISSOLVED 

AND ALIQUOT TAKEN PON ANALYSIS)

SotapU

Num Ui

Plutonium W«lgM 

P t r e t N

Plutonium Atom ic 

P o rte n t

Avtr&fe Atomic 

Percent

1 I I I 10.71

1 M l tt.ll 10. M

1 •O S to. SI

4 P U • OS

1 IA S S.S4 M l

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ELECTRICAL CONDUCTIVITY

i w in +*mmm

4 5 6

DISTANCE (cm from m o i k t d e n d )

Fig. 1. Rndtofraph of 10 atomic percent Pw rod and electrical and 

thermal conductmtl** u function of location.

3 .0

A

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_ J _ 1 1 1 L1 1 1

I 2 5 4 5 6 7 8 9 10 II 12

DISTANCE (cm from m orkad ond)

rtf. 1. Radiograph of ft atonic percent of Pvi rod and electrical conductivity aa function of location.

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Fig. 9. Electrical conductivity a t a function of location on 

the rod for pur? Al and 1.5 atomic percent Pu.

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THERMAL CONDUCTIVITY (c o l/W M K #C)

f t f . 4. Electrical conduct!* ttj a* (Unction ol thermal conductivity for 

Pu-AI alloys.

ATOMIC PERCENT f>u

F l|. ft. Thermal conductivity as a function of atomic percent Pu 

In Pu-AI alloys.

S ’ *1