Primary radiation damage on displacement cascades in UO2, ThO2 and (U0.5Th0.5)O2

Primary radiation damage in UO2, ThO2 and (U0.5Th0.5)O2 has been investigated as function of temperature (300 to 1500 K) using classical molecular dynamics (MD) simulations. Displacement cascades of 5 keV are used for defect production. The number of defects produced from the cascade events in UO2 is higher than that in ThO2 at all temperatures. Our results indicate that the defect production in (U0.5Th0.5)O2 is different from that in the pure oxides. The number of residual defects in the mixed oxide fuel is considerably higher than in UO2 or ThO2. In all three systems studied, the fraction of anion defects is much higher than that of cations, in line with higher defect energies of the U sublattice compared to the O sublattice. It is also reported that for increasing temperature peak damage increases, while residual damage decreases. This is indicative of the greater recombination of defects due to enhanced mobility at high temperatures. All systems studied exhibit clustering in the residual damage with interstitial clusters tending to be smaller than voids.