Ionization-induced defect annealing by fission product ions in SiC and its implication for UO2-SiC composite fuels

Based on molecular dynamics simulations on damage production and accumulation, and ionization-induced annealing of defects, a kinetic model on defect evolution has been developed for silicon carbide, and has been applied to investigate the effects of ionization-induced defect annealing by fission products on the evolution of radiation damage in the SiC of UO2-SiC composite fuels. The simulations indicate that fission product (FP) ions can induce defect recovery in pre-existing displacement cascades in SiC, the extent of which seems relevant to the spatial correlation of primary damage. The model predicts that the defect annealing by FP ions can suppress defect accumulation in the SiC of UO2-SiC composite fuels, which helps to improve the thermal conductivity of the composite fuels under irradiation, and the effect decreases with the distance from the UO2 matrix. The results indicate that defect annealing by FP ions plays an important role in the defect evolution in the SiC of UO2-SiC composites, and should be considered in evaluating the performance of UO2-SiC composite fuels under irradiation and in the design of composite fuels.