Pitting corrosion simulation from UH3 expansion in uranium hydrogen environment with a validation through existing experimental data

Abstract

The radioactive nature of uranium and the flammability of uranium hydride make it difficult to monitor and characterize its corrosion state in real time, limiting the study of the corrosion behavior of uranium in a hydrogen environment. In this work, a three-dimensional transient corrosion model of uranium metal material in hydrogen environment is established based on the finite element method, which intuitively reveals the corrosion behavior and corrosion mechanism of the hydride incubation, nucleation and growth process of uranium in hydrogen environment. The formation of hydride process of uranium undergoes three stages: the incubation stage, the nucleation stage, and the acceleration stage. The corrosion primarily manifests as pitting corrosion, progressing in a spherical morphology. The uranium-hydrogen reaction incubation stage arises mainly from the process of hydrogen diffusion. The strong stress accumulation and damage to the matrix induced by the volume expansion of hydride is the root origin of the formation of hydrogen pits. The accelerating effect of temperature on the reaction rate of uranium-hydrogen mainly results from the increase in the reaction rate constant and the significant increase in the diffusion rate. The magnitude of the elastic modulus and Poisson's ratio of uranium is positively correlated with the stress accumulation caused by hydride growth and the degree of damage to the uranium matrix. The findings provide a basis for designing new corrosion-resistant uranium alloys through numerical simulation. This work offers valuable insights into the prediction of damage caused by hydride formation in hydrogen-containing environment.