Interaction between Voids and Grain Boundaries in UO₂ By Molecular-Dynamics Simulation

This work uses atomic-level simulations to analyze the interactions of voids with a grain boundary (GB) in UO2, the ubiquitous fuel material for light water reactors. Specifically, the high-temperature interactions of a (3 1 0) Σ5 tilt GB structure with voids of diameter 1.8 nm are analyzed. We find that the GB tends to move towards the void when they are within a few nm of each other. With increasing temperature, GB migration from greater distances toward to the void is predicted to take place. Both GB pinning to the void and void dissolution at the GB take place. The atomic-level mechanisms and the energetics associated with these processes are characterized