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 x(2). In addition, the theoretical low temperature sintering temperature was calculated to be in the range of 1089-1151 degrees 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.