Three Dimensional Coupled Simulation of Plutonium, Oxygen and Heat Diffusion in Mixed Oxide (U, Pu)O2 Fast Reactor Fuel

Plutonium and oxygen diffusion with the high temperature gradient is one of the important fuel performance concerns in fast reactor (U, Pu)O2 fuel during irradiation, and will affect nuclear fuel materials properties, power distribution and overall performance of the fuel pin. This paper focuses on the plutonium, oxygen and heat diffusion within (U, Pu)O2 fast reactor fuel pellets. In this study, the correlations from the literature are used for thermal conductivity, specific heat, density, plutonium diffusion and oxygen diffusion. Three dimensional burnup dependent oxygen diffusion, plutonium diffusion and heat diffusion models are fully-coupled in steady states and transients to account for the effects on each other. The models are implemented into COMSOL Multiphysics to perform this analysis.