Finite element simulation for microstructural evolution in U-Mo/al dispersion fuel

U-Mo alloy dispersion fuel in an Al matrix in a plate geometry irradiated to high burnup at high power (that is, high fission rate) exhibited microstructural changes including deformation of the fuel particles, pore growth, and rupture of the Al matrix. The driving force for these microstructural changes was the swelling of fueled zone, called fuel meat, resulting from a combination of fuel particle swelling and interaction layer (IL) growth. In some cases, pore growth in the interaction layers also contributed to the fuel zone swelling. The main objective of this work was to determine the stress distribution within the fuel meat that caused these phenomena. A mechanical equilibrium between the stress generated by fuel meat swelling and the stress relieved by fission-induced creep in the meat constituents (U-Mo particles, Al matrix, and IL) was considered. Test plates with well-recorded fabrication data and irradiation conditions were adopted. Finite element analysis (FEA) utilizing an ABAQUS simulation package was performed to simulate the microstructural evolution. The simulation results allowed for the determination of hydrostatic stress exerted on the meat constituents. The effects of fabrication and irradiation variables on the stress distribution that drives microstructural evolutions, such as pore growth in the IL and Al matrix rupture, were investigated. (author)