Abstract Nitriding treatments have been adopted as an effective way to enhance the anticorrosion properties of uranium metal in ambient conditions but the mechanism remains unclear. We tackle this issue through first principles studies for the geometric, magnetic, electronic and vacancy properties of bulk α-U 2 N 3 , as well as its reaction with oxygen. The formation of N (U) single vacancy in α-U 2 N 3 is almost spontaneous under U-rich (O-rich) conditions. The adsorption of oxygen up to 300% of U contents, both on vacancy sites and in interstitial sites, may further gain energy by forming α-U 2 N 3 O x and UO 3 frameworks. Energy barriers for oxygen diffusion through α-U 2 N 3 layers are larger than 1.5 eV, and hence the thin U 2 N 3 layer prevents the oxidation in deep uranium layers. The structure of α-U 2 N 3 O 3 is chemically disordered and the final oxidization products are most likely N 2 and UO 3. Our theoretical studies provide useful information to understand the oxidation process of α-U 2 N 3 , and also give insights in the further development of surface treatment technologies for uranium. [ABSTRACT FROM AUTHOR]