Fabrication of oxide pellets containing lumped Gd2O3 using Y2O3-stabilized ZrO2 for burnable absorber fuel applications

In this paper, the fabrication of novel burnable absorber fuel concepts with oxide pellets, containing either a lumped Gd2O3 rod, a mini-pellet, or a spherical particle in the centerline of the oxide pellet, is investigated to propose the lumped Gd2O3 burnable absorber fuel concept to improve nuclear fuel performance with longer fuel cycle lengths and better fuel utilization. The unique characteristic of the lumped Gd2O3 burnable absorber fuel is its high spatial self-shielding factor that reduces its burnout rate and, therefore, improves the reactivity control. Oxide pellets containing lumped Gd2O3 were fabricated by using a combination of cold isostatic pressing and microwave sintering at 1500 degrees C to understand the potential technical issues in the fabrication of duplex burnable absorber fuel. The effect of the sintering temperature on the densification and phase transformation of 8wt.% yttria-stabilized zirconia, a surrogate for UO2, was investigated. Spherical Gd2O3 particles were fabricated by the drip casting of a Gd2O3-based Na alginate solution. The fabrication of duplex oxide pellets by using presintered Gd2O3 mini-pellets resulted in internal cracks at the interface between the Gd2O3 and 8wt.% yttria-stabilized zirconia layers because of the mismatch of their densification. However, the formation of interfacial cracks was eliminated by controlling the initial sintered density of the lumped Gd2O3.