Predicted mechanisms for radiation enhanced helium resolution in uranium dioxide

Classical molecular dynamics has been performed to predict the behaviour of helium gas bubbles in uranium dioxide, UO2, when subjected to displacement cascades that mimic the effects of self-irradiation damage. The models presented here examine bubble sizes of 2 and 4 nm with several different gas densities and displacement cascades with energies of up to 50 keV. Of particular interest are the mechanisms by which helium atoms can be returned to solution in the lattice through interaction with displacement cascades. This occurs both via ballistic recoil from high-energy ion fragments traversing the bubble and also a damage assisted resolution whereby the high-pressure gas intermixes into the disordered cascade regions formed adjacent to the surface of the bubble.