Molecular reactions and oxidation corrosion on UN (001) surface under exposure to environment gases: A DFT study
Abstract
Density functional theory calculations were performed to study reactions on uranium mononitride (UN) surface when it is in contact with environment gases such as O2, H2O, N2, H2. The chemical adsorption of O2 on UN surface is much more active than other surface reactions. Microkinetic analysis shows that the UN surface is mainly adsorbed by N2 at room temperature, suggesting nitrogen molecules in the air can protect UN from being oxidized. When temperature is above 350 K, the rate of surface oxidation speeds up significantly with the full O-adsorption on UN occurring within a relatively short time. Ab initio thermodynamic calculations display that the UN surface undergoes atomic rearrangements upon oxygen adsorption, which leads to the expansion of crystal lattice and opens the pathways for O diffusion into the sub-surface. Our work constitutes the first ab initio-based kinetic study of surface reactions on UN and contributes to the understanding of oxidation corrosion of this promising nuclear fuel at atomic scales.
- Publication:
-
Journal of Nuclear Materials
- Pub Date:
- May 2020
- DOI:
- 10.1016/j.jnucmat.2020.152095
- Bibcode:
- 2020JNuM..53352095C
- Keywords:
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- Uranium mononitride;
- Density functional theory;
- Surface reactions;
- Microkinetic analysis;
- Oxidation