Microstructurally explicit study of transport phenomena in uranium oxide

Transport mechanisms, such as mass and heat transfer, are critical to the efficiency and the reliability of nuclear fuels such as uranium oxide. These properties can be significantly affected by the microstructure of materials. This paper looks into the effects of grain boundary (GB) Kapitza resistance on the overall thermal conductivity and fission gas transport of UO₂ using a 3-D finite element model with microstructurally explicit information. The model developed is created with a reconstruction of the microstructure of depleted uranium samples performed using serial sectioning techniques with Focused Ion Beam (FIB) and Electron Backscattering Diffraction (EBSD). The properties of these microstructural entities are characterized by misorientation angles and Coincident Site Lattice (CSL) models, which provide a framework to assign spatially dependent thermal and mass transfer properties based on the location and connectivity of these entities in actual microstructures. The key feature of this model is the coupling between heat transfer and mass transfer of fission products which makes it a multi-physics model capable of following the evolution of thermal performance as fission products are produced.