Oxygen diffusion in the fluorite-type oxides CeO, ThO, UO, PuO, and (U, Pu)O

加藤 正人; 渡部 雅; 廣岡 瞬; Vauchy, R.

Frontiers in Nuclear Engineering (Internet), 1, p.1081473_1 - 1081473_10, 2023/01

https://doi.org/10.3389/fnuen.2022.1081473

This study evaluates oxygen self-diffusion and chemical diffusion coefficients of fluorite-type oxides CeO, ThO, UO, PuO, and (U, Pu) O using point defect concentration, oxygen vacancies, and interstitial oxygen. The self-diffusion coefficient changed in proportion to the 1/n power of oxygen partial pressure, which is similar to the oxygen partial pressure dependence of the defect concentration. All parameters used to represent the diffusion coefficients were determined, and the experimental data were accurately stated. The chemical diffusion coefficient was much higher at O/M = 2.00 than in low O/M oxides. In the reduction process, the chemical diffusion control rate was dominant, and a new phase with O/M = 2.00 was formed, and it expanded from the surface in the oxidation process from a low O/M ratio to O/M = 2.00.