A first-principles study of damage induced by gaseous species He, Kr, and Xe on the structure of nuclear fuel, U3Si

Abstract

A first-principles approach is employed to study the damage caused by gaseous species, He, Kr, and Xe atoms, on the structures of nuclear fuel U3Si. Formation energies suggest that a U vacancy is more readily generated than is an Si vacancy, and that gaseous atoms, He, Kr, and Xe, favor residing in vacancies compared with interstitial sites. By combining the trapping energies and formation energies of secondary vacancy defects, it can be determined that the number capacity of one U or Si vacancy to trap He atoms in U3Si is two or three, while it is only one with respect to Kr and Xe. When the number of trapped He (Kr and Xe) atoms is increased to four (two), the production of a secondary U vacancy is energetically favorable, and the formation of He (Kr and Xe) bubbles can be initiated. Additionally, when an Xe atom is trapped in an Si vacancy of β-U3Si, Xe bubble evolution is predominantly controlled by diffusion. From this work, one may gain new insight into the mechanism behind bubble formation in uranium silicide fuels.