A molecular dynamics study of radiation induced diffusion in uranium dioxide
Résumé
The nuclear oxide fuels are submitted ‘in-pile’ to strong structural and chemical modifications due to the
fissions and temperature. The diffusion of species is notably the result of a thermal activation and of radiation
induced diffusion. This study proposes to estimate to what extent the radiation induced diffusion
contributes to the diffusion of lattice atoms in UO2. Irradiations are simulated using molecular dynamics
simulation by displacement cascades induced by uranium primary knock-on atoms between 1 and
80 keV. As atoms are easier to displace when their vibration amplitude increases, the temperature range
which have been investigated is 300–1400 K. Cascade overlaps were also simulated. The material is
shown to melt at the end of cascades, yielding a reduced threshold energy displacement. The nuclear contribution
to the radiation induced diffusion is compared to thermally activated diffusion under in-reactor
and long-term storage conditions.