AbstractUsing natural ThO2 and UO2 in which radiation damage has accumulated over geologic periods, we have measured the relative in dissolution rates bicarbonate-carbonate solutions of the actinide isotopes 238U, 234U, 232Th, 230Th, and 228Th. An enhanced dissolution by a factor of 2 to 7 of the short lived (1.9 yr) 228Th relative to that of its structurally incorporated primary isotope 232Th indicates the presence of severe localized atomic displacement damage created by alpha-recoil atoms. In contrast, the relatively small (<20%) isotopic fractionation between the radiogenic 8.0 × 104 yr- 230Th isotope and 232Th, and between the radiogenic 2.5 × 105 yr- 234U isotope and its primary structurally incorporated isotope 238U, suggests the nearly complete annealing of the alpha-recoil damage during a period of less than 105 yr. An estimate of the mean fading time for the leachable damage is 15,000 yr.
Modelling radiation damage at grain boundaries in fcc Nickel and Ni-based alloy using Long Time Scale Dynamics Techniques
