FEM modeling of UO2-BeO composite fuel thermal conductivity

Commercial light-water reactors currently use UO₂ as a nuclear fuel, which has demonstrated several desirable characteristics. However, UO₂ has a low thermal conductivity that leads to the development of a large temperature gradient across the fuel pellet. This temperature gradient contributes to limits in the operational performance of the reactor due to effects that include thermal stresses causing pellet cladding interaction and the release of fission product gases. A ceramic-ceramic composite nuclear fuel has an increased effective thermal conductivity due to adding a second compatible and high thermal conductivity ceramic to UO₂. SiC and BeO are two materials that demonstrate compatibility with UO₂ and have a high thermal conductivity. The development of ceramic-ceramic composite nuclear fuels benefits from thermal modeling by providing an understanding on how fabrication variables, such as phase fractions, densities, and geometry, effective thermal conductivity. FEM 2D and 3D programs were used to predict the thermal conductivity of composite UO2-BeO materials. The FEM modeling results were compared to the measured UO₂-BeO fuel sample thermal conductivities. The comparison showed that the thermal modeling was in agreement with the measured values. These benchmarking cases with the FEM thermal modeling method successfully demonstrated the potential of the models to accurately predict the effective thermal conductivity of an enhanced thermal conductivity oxide nuclear fuel.