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IRRADIATION SWELLING OF URANIUM AND URANIUM ALLOYS

Technical Report ·
OSTI ID:4833528

A study of irradiation data on uranium and uranium alloys was made to determine some of the parameters which affect the swelling of metal fuels during high temperature irradiation. The swelling of uranium measured at various intervals to 0.1 at.% burnup appears to increase linearly with burnup at constant temperature in the SRE. On this basis, the fuel is assumed to have a constant swelling rate at a constant burnup rate up to 0.1 at.% burunup. Irradiation data on uranium from the SRE were compared to MTR data. The total fuel swelling for a given temperature and burnup is about the same in both reactors above 500 deg C. Since the burnup rate is much higher in the MTR, the calculated swelling rate is also much higher. It was concluded that irradiation affects the swelling rate by increasing the mobility and/or the number of dislocations. On the basis of SRE and MTR results, variations in thermal cycling and thermal stress in uranium slugs during irradiation have a relatively small effect on the swelling. The creep strength of the unirradiated fuels was measured, and the creep strength of the fuels during irradiation was calculated at 485 deg C. They do not agree at this temperature, but they do agree if the measured creep strength of the unirradinted fuel at 600 deg C is compared to the creep strength calculated for the fuel under irradiation at about 500 deg C. This difference, about 100 deg C, indicates that a decrease in fuel strength may be caused by irradiation. Anisotropic irradiation growth is negligible in the uranium alloy fuels between 350 and 500 deg C and in uranium above 500 deg C. The data indicate that anisotropic irradiation growth is appreciable in alpha -rolled and beta - quenched uranium up to 500 deg C. (auth)

Research Organization:
Atomics International. Div. of North American Aviation, Inc., Canoga Park, Calif.
DOE Contract Number:
AT(11-1)-GEN-8
NSA Number:
NSA-15-031266
OSTI ID:
4833528
Report Number(s):
NAA-SR-4893
Country of Publication:
United States
Language:
English