Defect formation and accumulation in CeO2 irradiated with swift heavy ions

We have investigated microstructure evolution in CeO2 irradiated with 210 MeV Xe ions by using transmission electron microscopy to gain the fundamental knowledge on radiation damage induced by fission fragments in nuclear fuel and transmutation target. Analysis on the accumulation of ion tracks has revealed an influence region to recover pre-existing core damage regions of ion tracks to be 8.4 nm in radius. Cross section observations showed that high-density electronic excitation induces both ion tracks and dislocation loops. At high fluences of 1.5 × 1019 and 1 × 1020 ions m−2, depth-dependent microstructure was developed with radiation-induced defects of ion tracks, dislocation loops (dot-contrast) and line dislocations. Formation of sub-divided small grains was found at shallow depth at a fluence of 1 × 1020 ions m−2. The microstructure evolution was discussed in terms of the accumulation of interstitials due to significant overlap of high density electronic excitation.