Influence of thermal effect on dislocation loop evolution in Fe+-irradiated CeO2 during in-situ annealing

Abstract

Cerium dioxide (CeO2) is widely used as a surrogate fuel for uranium dioxide (UO2) because of their same cubic fluorite crystal structure, nearly identical lattice parameters and similar physical properties. The degree of irradiation damage is related not only to the irradiation dose but also to the thermal effect. The influence of the thermal effect on the microstructure of Fe+-irradiated CeO2 was investigated using in-situ transmission electron microscopy analysis during annealing. Shrinkage of the dislocation loops was observed for the first time in the irradiated CeO2 foil. The threshold size determining whether the dislocation loop shrank was found to be approximately 19 nm through experimental measurements. When the loop size was less than this value, the dislocation loop shrank or even disappeared as the annealing time increased. Moreover, the smaller the loop size, the larger the shrinkage. The shrinkage rate measured in the in-situ annealing experiment was approximately 0.08 nm/s, which was almost consistent with the theoretical calculation (about 0.11 nm/s). However, when the loop size was larger than 19 nm, the loop grew rapidly at the beginning of annealing and then remained stable.