First-principles study of Xe behavior in δ-UZr2

Abstract

The main problem hindering the application of uranium-zirconium (U-Zr) fuel is the swelling caused by the generation of fission gas. In this study, investigating the behavior of fission gas xenon (Xe) in δ-UZr2 using the first-principles method is the focus. The formation energies of substitutional and interstitial Xe atoms are significantly dependent on the local atomic environment. According to the present study, the Xe formation energy increases as the number of coordinated U atoms increases. δ-UZr2 exhibits a more remarkable ability to capture Xe than α-U due to the lower Xe formation energies. In addition, the interstitial Xe energetically prefers to occupy octahedral sites or form a dumbbell with a metallic atom at the 2d site along the 〈0001〉 direction. The diffusion of interstitial Xe also relies on the local environment, while Zr-rich conditions can enhance it. Compared with α-U, Xe atoms energetically preferers to form clusters in δ-UZr2