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

The thermal recovery of self-irradiated and damaged U0.80Am0.20O2−x solid solution has been studied in situ using high-temperature x-ray diffraction between 25 °C and 1300 °C. The cumulative αα 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 UO2 and AmO2. 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 U0.80Am0.20O2−x sample is also discussed and compared to that of defect free UO2, NpO2 and AmO2 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 U0.80Am0.20O2−x sample is obtained.