Effect of Multiple Sintering Additives on Microstructure of Gd_2O_3-UO_2 Pellets

Gd2O3-UO2 is widely used as burnable absorber in nuclear power plants in recent years. It was investigated that multiple sintering additives which included respectively 150μg/g Al2O3, TiO2, V2O5 effected on the microstructure of Gd2O3-UO2 pellets in the report. It was shown that multiple sintering additives decreased the sintering temperature of Gd2O3-UO2 pellets, and the pellet density reached ~97%TD after sintering in hydrogen atmosphere at 1500℃ for 4 hours. The close pores of pellets always reduced during 1400～1750℃, and the total number of close pores of the pellets sintered at 1750℃ were less than that at 1650℃. However, the volume of single pore increased, and the main mechanism may be the small pores amalgamation. The grain growth rate became differences between different grains during 1400℃～1600℃. Some grain developed rapidly and there were double peaks in the distribution of grain size. The double peaks were disappeared when the sintering temperature reached 1750℃, and the average grain size was about 25μm.