Irradiation induced lattice defects in UO2

Two kinds of sintered UO2 having 2.5 and 5 μm grain sizes were irradiated below 150°C to fission doses between 1.14 × 1014 and 2.92 × 1018 fissions/cm3. The changes of lattice parameter and lattice strain with fission dose were studied. Three stages appeared in the dose dependence of lattice parameter and lattice strain which depended on grain size. In the beginning of the first stage the lattice strain decreased to some extent. The recovery of the lattice parameter within each stage was studied and defects produced in each stage were also discussed. The effective volumes per fission event were calculated at each stage based on kinetic consideration of defects.