Low-temperature sintering mechanism on uranium dioxide

Based on a point defect model, the mechanism of low-temperature sintering of uranium dioxide was studied in this paper. The diffusion coefficient of uranium in UO2 + x, sintering temperature and densification equation in low-temperature sintering were analyzed by both the point defect model and low-temperature sintering experiments. The results showed that the diffusion activation energy of uranium in over-stoichiometric UO2 + x was lowered by 3.0 ev than that in stoichiometric UO2. And the diffusion coefficient of uranium in UO2 + x was proportional to x2. In addition, the theoretical low temperature sintering temperature was calculated to be in the range of 1089–1151 C, which indicated that it was necessary to maintain proper over-stoichiometric oxygen for low-temperature sintering process. Moreover, the calculation results by the point defect model matched perfectly with the experiment results, PDM might be a good model to describe the relationships between defects concentration and atmosphere composition.