An initial assessment of a mechanistic model, GRASS-SST, in U-Pu-Zr metallic alloy fuel fission-gas behavior simulations

► Fission gas behavior in irradiated U-Pu-Zr metallic alloy fuels was studied. ► Key materials properties of each phasal zones were predicted. ► Fission gas release and gas bubble size distributions were used for the benchmarking. ► Parametric studies revealed impacts of materials properties on fission gas behaviors.