| 학회 | 한국재료학회 |
| 학술대회 | 2021년 봄 (05/12 ~ 05/14, 광주 김대중컨벤션센터) |
| 권호 | 27권 1호 |
| 발표분야 | E. 환경/센서 재료 분과 |
| 제목 | The Influence of Gd doping on Oxidation Resistivity of UO2 |
| 초록 | UO2 is of interest material particularly regarding with their long-term structural integrity at deep underground as disposed spent nuclear fuel. Gd-doped UO2 (Gd-UO2) is one of its derivatives forming via nuclear fission of U-235. In spite of experimental reports on influence of Gd dopant on UO2 oxidation its underlying mechanism is not clearly known. In this study, we utilize first-principles density functional theory (DFT) calculations to elucidate how the oxidation behaviors of a pure UO2 change with substitutional doping of Gd for U element. The oxidation of UO2 and Gd-UO2 is modelled as two-step process: (i) adsorption of O atoms on the surface. (ii) diffusion of adsorbed O into interstitial sites of UO2 subsurface. Adsorption energy of O in (111) surfaces of UO2 and Gd-UO2 with varying coverage are calculated. Our results indicate that the doped Gd atoms weaken the O adsorption regardless of the surface coverages less than 1 monolayer. Electronic structure calculations shows that the UO bond strength is weaker in Gd-UO2 than in pure UO2 due to less charge transfer from U to O. Moreover, the doped Gd atoms do not adsorb O, indicating they effectively reduce adsorption sites of O. These two facts consistently poise that Gd doping can enhance the structural integrity of UO2 due to preventing the surface oxidation. Our DFT calculations also indicate that Gd doping suppresses surface diffusion of O via lattice contraction of UO2. In summary, the oxidation of Gd-UO2 is thermodynamically less favorable than pure UO2. Our results can guide for post-process to enhance the safety for spent nuclear fuel disposed in deep underground. |
| 저자 | 홍민준, 권초아, 한병찬 |
| 소속 | 연세대 |
| 키워드 | <P>first principles; Gd doped UO<SUB>2</SUB>; oxidation resistivity; adsorption energy; Mulliken population analysis; electron localization function; </P> |
