Finite-Element Simulation of Residual Stresses During the Processing of Lumped Burnable Absorber Fuel

UO 2 –Gd 2 O 3 fuel is mostly used as a burnable absorber fuel in the form of a homogenous mixture of Gd 2 O 3 and UO 2 . More effective reactivity control can be achieved by lumping Gd 2 O 3 within the UO 2 because this enhances the spatial self-shielding factor of the burnable absorber fuel. The fabrication of lumped burnable absorber fuel containing lumped Gd 2 O 3 spherical particles or compacts has been experimentally demonstrated using yttrium-stabilized zirconia (YSZ) as a UO 2 fuel surrogate. Interfacial cracks or gaps forming under the interfacial stress that develops during the fabrication of the fuel can be eliminated by controlling the initial density of the lumped Gd 2 O 3 . In this study, this interfacial stress during the fabrication process was simulated using finite element methods. The effect of the size, shape, and initial density of the lumped Gd 2 O 3 on the distribution and magnitude of the interfacial stress was investigated. The addition of Gd 2 O 3 spherical particles resulted in a lower and more uniform interfacial stress distribution than the addition of cylindrical Gd 2 O 3 compacts. The interfacial stress was increased with increasing Gd 2 O 3 size and initial density. The calculated interfacial stress was compared with experimental results to estimate the threshold stress for crack development in a lumped burnable absorber fuel.