Dopant-assisted preparation of large-grain UO 2 pellets for high-burnup fuels

Large-grain UO 2 pellets are a key focus in high-burnup fuel research. In this study, large-grained UO 2 pellets were fabricated by adding various dopants to UO 2 powder and sintering in a wet-hydrogen atmosphere. The effects of sintering atmosphere and individual or combined additives such as Cr 2 O 3 , SiO 2 , and Al 2 O 3 on the grain size of UO 2 pellets were systematically investigated. The results show that using a wet-hydrogen sintering atmosphere together with Cr 2 O 3 and other dopants can produce UO 2 pellets with grain sizes on the order of 50 μm. Grain size is primarily governed by Cr 2 O 3 and, to a lesser extent, Al 2 O 3 , whereas the addition of SiO 2 tends to suppress grain growth. Building on previous work, this study verifies the synergistic effects of Cr 2 O 3 , Al 2 O 3 , and SiO 2 —both individually and in combination—on UO 2 grain growth. By optimizing actual process parameters, UO 2 pellets with grain sizes of 50∼70 μm were successfully fabricated. The investigation further clarifies the correlation between dopant mechanisms and the operational process window, providing an essential foundation for the engineering application of high-burnup fuels.