Distribution of heating in an LVRF bundle due to dysprosium in the central element

The computer code MCNP was used to establish the effect of adding dysprosium to the central pin of the proposed BRUCE-B CANFLEX® Low-Void-Reactivity Fuel (LVRF) on the heat load of the central pin and the heat balance inside the fuel bundle. The Dy generates heat through radiative capture of thermal neutrons, as well as through beta decay of ¹⁶⁵Dy to ¹⁶⁵Ho. We conclude that for fresh fuel, the presence of Dy contributes 26% of the overall heat to the central pin, and 0.5% to the whole fuel bundle. These percentages decrease to 11% and 0.5% at the end-of-life burnup condition. A second, operational quantity is the HPFP ratio (heating-power to fission-power ratio). This ratio is 1.63 for fresh fuel and decreases to 1.19 for fuel at the end-of-life burnup condition.