Effect of stress evolution on microstructural behavior in U-Mo/Al dispersion fuel

Abstract

U-Mo/Al dispersion fuel irradiated to high burnup at high power (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 meat swelling 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 meat 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 used, and their post-irradiation examination (PIE) data was obtained. ABAQUS finite element analysis (FEA) was utilized to simulate the microstructural evolution of the plates. The simulation results allowed for the determination of the shear stress, effective stress, and 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.

Mechanical Properties and Deformation Mechanisms of Nanocrystalline U-10Mo Alloys by Molecular Dynamics Simulation

“…Higher fuel density is required at lower uranium enrichment levels to keep reactors performing. The most potential candidate for high-density fuels is considered to be U-Mo alloy [ 5 , 6 , 7 , 8 , 9 , 10 ], which exhibits much higher uranium density and thermal conductivity than traditional fuels used in reactors, as well as lower neutron capture cross-section, better irradiation behavior and tolerable swelling reaction. Adding molybdenum (Mo) stabilizes the high-temperature cubic γ-U phase, which enhances its irradiation behavior, such as dimensional stability [ 11 ].…”