Annealing of the defects observed by Raman spectroscopy in UO2 irradiated by 25 MeV He2+ ions

Understanding the effect of irradiation in UO2 is a major issue for nuclear industry and for the design of irradiation resistant materials. We have previously evidenced irradiation induced defects in UO2 that can be characterized by Raman spectroscopy. Here we present the Raman characterization of these defects as a function of temperature. UO2 samples were irradiated with 25 MeV He2+ ions at room temperature and then heated at different temperature without irradiation. Some samples were also irradiated at high temperature. Heat treatment after irradiation evidenced one annealing temperature on Raman spectra. This annealing temperature is shifted to higher values when the samples are simultaneously heat treated and irradiated. It is compared to the annealing temperatures that are reported in literature on irradiated UO2. This indicates that Raman observed defects would be point defects on uranium sublattice. This attribution is consistent with the one we previously proposed.