Evaluation of the effective thermal conductivity of UO2 fuel by combining Potts model and finite difference method

Abstract This paper evaluated the effects of porosity on the effective thermal conductivity of UO2 fuel by combining the Potts model and the finite difference method (FDM). Two types of microstructures representing irradiated UO2 microstructures were simulated by the Potts model in the three dimensional cubic system. One represented very small intragranular bubbles and a few intergranular bubbles under a low temperature condition. The other represented large intergranular bubbles under a high temperature or annealing condition. For the simulated microstructures, the effective thermal conductivities were determined by FDM calculation of the temperature distributions under steady state condition. They were compared with an experimental equation and the effect of bubble morphology was investigated by fitting a porosity shape factor in the Maxwell–Eucken equation. The simulation results showed a good agreement with an experimental equation and demonstrated the capability of the Potts model to provide information on microstructure for calculating the effective thermal conductivity of UO2 fuel.