Modeling of Equiaxed Grain Growth in Uranium Dioxide Fuels

Grain size is one of the most important parameters affecting fission gas release and swelling of nuclear fuels. On the other hand, fission gas bubbles in previously irradiated fuel interact with moving grain boundaries and affect subsequent grain growth. Equations are developed that describe equiaxed grain growth in oxide fuel that has undergone previous irradiation (burnup) at temperatures too low to promote grain growth. The resulting expressions relate the grain growth rate at the new high temperature to the percent burnup (or fission gas content) experienced during the prior low-temperature period.