Interaction between 1/2 110 {001} dislocations and {110} prismatic loops in uranium dioxide: Implications for strain-hardening under irradiation

Plasticity of irradiated UO2 is of major interest to improve the risk assessment of the nuclear fuel cladding failure in the case of design basis accidents. In this study, we investigate the main irradiation-hardening processes induced by {110} irradiation loops interacting with glissile dislocations of the primary slip system, 1/2<110>{001}, of UO2. The interactions are simulated at two scales using molecular dynamics and discrete dislocation dynamics, to characterise local interactions and identify strengthening configurations as a function of the dislocation-irradiation loop geometry. In particular, we show that 1/2<110>{001} screw dislocations can be strongly pinned by helical turn configurations. Statistical large-scale discrete dislocation simulations are performed to investigate the collective behaviour of a large density of irradiation defects and quantify irradiation hardening. Several microstructural processes including loop drag and shovelling are observed and their involvement in clear band formation and hardening of UO2 fuel at high temperature is discussed.

Automated summary

In this study, the plasticity of irradiated UO2 is investigated using molecular dynamics and discrete dislocation dynamics simulations. The interactions between irradiation loops and glissile dislocations are studied, and the effects of these interactions on the strengthening of UO2 are characterized. The collective behavior of irradiation defects and the formation of clear bands in UO2 fuel at high temperature are also discussed.