Atomic-scale insights into the microstructure of reactor-irradiated advanced Cr-doped UO2 nuclear fuel

Abstract Chromia-doped UO 2 fuel (DF) is advanced nuclear fuel and one of the potential candidates to fulfill the accident tolerant fuel applications. During the irradiation process, the in-reactor performance of nuclear fuel is closely related to the change in fuel microstructure as the burnup proceeds. Here, we report a number of important findings from synchrotron-based X-ray diffraction experiment on the atomic-scale microstructural evolution in high burnup DF considering the effects caused by the chromium dopant and chemically active various fission product elements. The results presented are UO 2 lattice parameter evolution for different levels of fuel burnup, a microscale insight into the distributions of lattice strain development in irradiated fuel materials and quantitatively estimated geometrically necessary dislocation densities developed progressively with burnup in high burnup spent fuels. We also present a direct comparison study for the irradiated doped and undoped UO 2 materials. By analyzing the microstructural features of standard and doped UO 2 fuels, a comprehensive and comparative overview of the structural changes in high burnup UO 2 crystallites is provided which furnish valuable information for safe and continued use of these materials, in particular chromia-doped UO 2 as an accident tolerant fuel option in combination with suitable cladding materials, for nuclear energy generation.