LAUSR

Abstract The formation and binding energetics that control the nucleation behavior of Xe-vacancy defect clusters in uranium monocarbide (UC) is investigated via density functional theory (DFT) calculations. Based on previous work, assumptions on the effective formation energy of U and C vacancies are made, and the substitutional defect Xe U is considered as the most stable Xe defect under carbon-rich conditions. The DFT calculations for the binding energy indicate that, depending on the non-equilibrium vacancy concentration under the specific irradiation conditions, clusters can grow by absorbing uranium vacancies, while a saturation effect exists for the absorption of carbon vacancies. It is also found that, depending on the supersaturation and correspondingly, the effective formation energy of Xe U under irradiation, the stable nucleus for a Xe bubble consists of a small cluster of 2 or 3 Xe atoms.