Oxidation mechanism and mechanical property of SiC coating in tristructural isotropic fuels under steam contained environments

The oxidation performance of silicon carbide (SiC) coating on nuclear fuel particle and the subsequent effect on the mechanical integrity was investigated. The effects of steam content on the phase composition and microstructure of the SiC layer at different temperatures were discussed. Reaction rates of steam with the SiC layer were found to obey the liner-parabolic oxidation law. The fracture strength of SiC shell was evaluated, which was dominated by the thickness variation of the SiC. Furthermore, finite element analysis was performed to simulate the stress distribution in the SiC shell during the crush test. The results revealed the SiC shell of reduced thickness caused by oxidation had higher stress concentration at the inner surface and resulted in a lower fracture strength value. (author)