A generalized model for radiation-induced amorphization and crystallization of U 3Si and U 3Si 2 and recrystallization of UO 2

Abstract

A rate-theory model of radiation-induced amorphization and crystallization of U 3Si during ion irradiation has been generalized to include U 3Si 2 and UO 2. The generalized model has been applied to ion-irradiation and in-reactor experiments on U 3Si and U 3Si 2 and provides an interpretation for the amorphization curve (dose required to amorphize the material as a function of temperature), for the ion-radiation-induced nanoscale polycrystallization of these materials at temperatures above the critical temperature for amorphization, as well as for the role of the small crystallites in retarding amorphization. An alternative mechanism for the evolution of recrystallization nuclei is described for a model of irradiation-induced recrystallization of UO 2 wherein the stored energy in the UO 2 is concentrated in a network of sinklike nuclei that diminish with dose due to interaction with radiation-produced defects. The sinklike nuclei are identified as cellular dislocation structures that evolve relatively early in the irradiation period. The complicated kinetics involved in the formation of a cellular dislocation network are approximated by the formation and growth of subgrains due to the interaction of shock waves produced by fission-induced damage to the UO 2.