| 초록 |
An accurate understanding of structural integrity and chemical reactivity of UO2 disposed in deep underground sites is of importance. Owing to the specific condition of the site, UO2 have different properties from the conventional prediction. In this study, we demonstrate that the oxidation resistivity of UO2 is modified by gadolinium (Gd), which is the byproduct of nuclear decay of radioactive U-235. Using first-principles calculations, we investigate how the oxidation mechanism of UO2 changes with incorporation of Gd. Our study indicates that Gd enhances the thermodynamic stability of UO2 against surface oxidation via three underlying mechanisms: (i) weakens the chemical bonding of adsorbed oxygen atom (O) with U, (ii) reduces active sites (U) for O adsorption, and (iii) suppresses the subsurface diffusion of adsorbed O delaying the growth of the oxide layers on the UO2. Electronic and lattice structure analyses for Gd-doped UO2 indicate that charge transfer from U to O is reduced and the lattice of the UO2 is contracted. Our results provide useful information for understanding long-term stability and improving the structural integrity of UO2 through chemical doping. |
