Tritium Diffusion Pathways in γ-LiAlO2 Pellets Used in TPBAR: A First-Principles Density Functional Theory Investigation

Abstract

With superior thermophysical and thermochemical properties, γ-LiAlO2 has high compatibility with other blanket materials and is used in the form of an annular pellet in tritium-producing burnable absorber rods (TPBARs) to produce tritium by thermal neutron irradiation of 6Li. In radiation damaged γ-LiAlO2, different types of vacancies, defects of its constituent elements, and other trapping sites hinder the diffusion process of tritium. In this study, the first-principles density functional theory approach is used to study the diffusion mechanisms of tritium defect and its species, such as interstitial and substitutional tritium defects, oxygen–tritium vacancy defects, and interaction of tritium with oxygen vacancies in defective and nondefective γ-LiAlO2. The obtained results provide an understanding of how such defects hamper the diffusivity and solubility of tritium. By calculating several different diffusion pathways, our results show that the smallest activation energy barrier is 0.63 eV for substitu...