An Annealing Study of Alpha-Decay Damage in Natural UO2 and ThO2

Abstract

AbstractIsochronal annealing (100°–1200°C) of alpha-decay damage was performed on UO2 and ThO2 and isothermal annealing (400°C and 750°C) of UO2 was done to determine the change in unit cell parameter (UO2: ao = 5.501Å to 5.458Å ± 0.001; ThO2: ao = 5.548Å to 5.523Å ± 0.001), strain, and crystallite size (data inconclusive). Two recovery stages (UO2: Stage I at ≈225°C, Stage II at ≈675°C; ThO2: Stage I at ≈250°C, Stage II at ≈550°C) were observed for each. Strain decreased with temperature for both, but never completely recovered in either (UO2 final value: ≈2.37 × 10−3; ThO2 final value: ≈2.06 × 10−3).