Pu-238 Oxide Fuel Fracture Behavior as a Function of Age

Fracture behavior as a function of age in fuels consisting of plutonium-238 oxide is likely to change as a function of fuel age, but definitive evidence of changes in fracture behavior as a function of age has not been reported. New impact test results are compared to each other and to historical impact test data, and historical data is reanalyzed to reveal the magnitude of the change with age. Particle sizes generated on impact are measured for each set of fuel, to characterize fuel pellet strength. Characterizing changes with age facilitates interpretation of variations in the somewhat stochastic results of fracture events. Where unit-to-unit variation is limited, the effect of aging can be discerned in impact tests. Methods of reducing the particle size distribution data to a single figure of merit are described. The magnitude of the variation attributable to age can be less than variation in the initial condition of units, confirming that phenomena arising from aging processes in the oxide are not contributing beyond the narrow range of fracture behaviors established during testing of normally varying plutonium oxide fuel.