Thermal recovery and lattice expansion of self-irradiated U0.80Am0.20O2−x, an in situ high temperature x-ray diffraction study

Abstract The thermal recovery of self-irradiated and damaged U 0.80 Am 0.20 O 2− x solid solution has been studied in situ using high-temperature x-ray diffraction between 25 °C and 1300 °C. The cumulative α decay dose of the damaged material was equal to 2.2 displacements per atom, leading to a lattice expansion of 0.31%. This value is close to the saturated lattice expansion of self-irradiated polycrystalline UO 2 and AmO 2 . The thermal recovery process is characterized by three stages, as revealed by the temperature derivative of the lattice parameter showing two maxima at 600 °C and 1000 °C. The thermal recovery is completed at about 1200 °C. These data are compared with existing studies on other oxide fuels. In addition, the lattice expansion of the damaged U 0.80 Am 0.20 O 2− x sample is also discussed and compared to that of defect free UO 2 , NpO 2 and AmO 2 materials. The thermal energy necessary to initiate the annealing of the defects is reached at about 400 °C, whilst at 1100 °C, a defect free U 0.80 Am 0.20 O 2− x sample is obtained.