Kinetic parameters of a material test research reactor fueled with various low enriched uranium dispersion fuels

Abstract

The effects of using different low enriched uranium fuels, having same uranium density, on the kinetic parameters of a material test research reactor were studied. For this purpose, the original aluminide fuel (UAl x –Al) containing 4.40 gU/cm 3 of an MTR was replaced with silicide (U 3Si–Al and U 3Si 2–Al) and oxide (U 3O 8–Al) dispersion fuels having the same uranium density as of the original fuel. Simulations were carried out to calculate prompt neutron generation time, effective delayed-neutron fraction, core excess reactivity and neutron flux spectrum. Nuclear reactor analysis codes including WIMS-D4 and CITATION were used to carry out these calculations. It was observed that both the silicide fuels had the same prompt neutron generation time 0.02% more than that of the original aluminide fuel, while the oxide fuel had a prompt neutron generation time 0.05% less than that of the original aluminide fuel. The effective delayed-neutron fraction decreased for all the fuels; the decrease was maximum at 0.06% for U 3Si 2–Al followed by 0.03% for U 3Si–Al, and 0.01% for U 3O 8–Al fuel. The U 3O 8–Al fueled reactor gave the maximum ρ excess at BOL which was 21.67% more than the original fuel followed by U 3Si–Al which was 2.55% more, while that of U 3Si 2–Al was 2.50% more than the original UAl x –Al fuel. The neutron flux of all the fuels was more thermalized, than in the original fuel, in the active fuel region of the core. The thermalization was maximum for U 3O 8–Al followed by U 3Si–Al and then U 3Si 2–Al fuel.