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 was studied in situ using high-temperature x-ray diffraction between 25◦C and 1300◦C. The cumulative α decay doses 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 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 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.JRC.E.6-Actinide researc