Dong-Joo Kim

Improvement of UO2 Pellet Properties by Controlling the Powder Morphology of Recycled U3O8 Powder

Powder morphology evolution of recycled U3O8 according to the thermal treatments has been studied. The defective UO2 pellets are oxidized to U3O8 powders at a conventional temperature of 350 or 450°C in air. Those powders are pressed into green pellets and then sintered at 1,500 and 1,730°C in H2 gas flow. Final reoxidized U3O8 powers are obtained by reoxidizing those sintered pellets at 450°C in air. This paper shows that the reoxidized U3O8 powder morphology and the BET surface areas are greatly dependent on the density of sintered UO2 pellets before reoxidation. Reoxidized U3O8 powders are added to virgin UO2 powders to fabricate UO2 pellets and the effect of such addition on the UO2 pellet properties is investigated. The reoxidized U3O8 powders having a certain range of BET surface area significantly promote the grain growth of UO2 pellets.