Point defects and irradiation-enhanced densification

Abstract

Analytical expressions are obtained for the time-dependent vacancy and interstitial concentrations at short irradiation times before equilibrium levels are established. During this period some shrinkage of initial porosity can arise through the net absorption of interstitials, the vacancies having insufficient time to reach fixed sinks. The maximum amount of void shrinkage occurring during this transient is calculated, together with the extent of the accompanying densification. Applied to UO₂ irradiated at 900 K at thermal reactor ratings it is concluded that the effects are negligible, in contrast to the previous assertion by MacEwen and Hastings (1975).