Preparation of UO₂ Pellets with Large Grain Containing Chromium

The UO₂ pellets with large grain and high thermal conductivity is an ideal nuclear fuel pellets with high burnup. According to the design requirements, trace substances Al₂O₃ and Cr₂O₃ should be added in UO₂ powder and then the fuel pellet is prepared in a powder metallurgy manner so as to ensure that the grain size is over 30μm and the density is 96.5% ~ 97%T.D. At the same time, the residual amount of Cr in the pellet should be 0.06 wt% ~ 0.1wt% in order to improve the thermal conductivity of the pellet. In the preparation process, the optimal addition amount of the two substances is determined by single addition method, and then the appropriate powder pretreatment technology is selected for the mixed addition test. The results show that by adding 0.008wt% ~ 0.01wt% Al₂O₃ powder and 0.2wt% ~ 0.3wt% Cr₂O₃ powder respectively, and using the method of coating Cr₂O₃ with the pelletizing powder, the UO₂ pellets with large grain containing chromium can be obtained, whose grain size can reach 43.3 μm, the density is 96.8% T. D, and the residual amount of Cr is 0.0864wt%.