The Influence of Microstructures on the Thermal Conductivity of Polycrystalline UO₂

The thermal conductivity is one of the most important properties for UO₂. The influences of microstructure are especially important for UO₂ due to the severe structural changes under irradiation conditions. In this study, we have investigated the thermal conductivity of UO₂ with different microstructures using Finite Element Method. The thermal conductivity increases with increasing grain size. The grain size distribution has obvious influence on the thermal conductivity especially when there are pores in the polycrystal. The influences of porosity and pore size are very sensitive to the position of the pores. The results obtained in this study are useful for prediction of property changes of UO₂ fuel in pile and important to gain some design guidance to tune the properties through the control of the microstructure.