What is the Role of Nb on Preferential Hydriding of Double-Phased Uranium, Stabilizing γ-U, or Avoiding Hydrogen Aggregation?
Xinxin Wang, Hefei Ji, Zi Li, Lijun Zhu, Xianglin Chen, Xiaoyong Yang, Ping Zhang, Peng Shi, Xiaolin Wang, Yu Yang, Wenhui Duan
Abstract
Uranium as the heaviest naturally occurring element plays important roles in nuclear industries. Hydrogen-caused corrosions and irradiation-caused structural damages are two critical degradations that threaten the safe storage and practical applications of uranium. Through alloying with transition metals like Nb, the γ-phase of U can be stabilized at room temperature, which shows better performance against hydrogen-caused corrosions than the ground-state α-U. The underlying mechanisms have not been fully understood yet. To explain the preferential hydriding phenomenon observed on a specially fabricated double-phase U-2.5 wt % Nb alloy, we perform multiscale ab initio calculations and kinetic Monte Carlo (KMC) simulations. We find that because of different diffusion mechanisms, intrinsic α-U and γ-U already show different hydrogen accumulation behaviors. The existence of random Nb atoms further inhibits hydrogen accumulation in γ-U. Our work declares its contribution by pointing out the important role of crystal lattice architectures on hydrogen accumulations in metals.