Structural Changes in Uranium Dioxide Induced by Chromia Doping

Description

Abstract (English)

Uranium dioxide (UO2) has served as the primary nuclear fuel material throughout the history of the nuclear industry. One approach to enhance its performance is by promoting larger grain growth, which improves fission gas retention and thermal conductivity. Chromia (CrOx) doping has become a key method for promoting grain growth in UO2, leading to the commercial development of products like 'ADOPT' and 'PROtect.' Chromia features a complex phase diagram, making it intriguing to study how factors such as valence state and local structure influence its incorporation into UO2. In this research, both Cr K-edge and U L3-edge XAFS were obtained to investigate the valence state and local structure of Cr and U in Cr doped UO₂, which was prepared in a synthetic condition that permitted the liquid-phase sintering of CrO. We compared the local structures of Cr and U in this doped UO2 to those in samples prepared below the eutectic temperature of CrO. These findings provide new insights into the fundamental behaviors governing species diffusion, which in turn affects grain growth in Cr-doped UO2. This understanding is crucial for enhancing fuel performance and advancing the development of next-generation nuclear fuels.