Gadolinium oxide (Gd2O3) is the most widely used nuclear fuel burnable absorber, used to enable higher enrichment fuel loading in reactor cores and to efficiently control reactivity. However, the use of gadolinium oxide in solid solution with UO2 requires some amount of uranium to be displaced, limiting its advantages, and also reducing the fuel’s thermal conductivity. Moreover, some isotopes of Gd2O3 can cause residual reactivity suppression in the fuel, again limiting their benefits. In this study, the changes in reactivity have been revealed by comparing natural Gd isotope compositions with Gd enriched with Gd-157 in Gd2O3 in solid solution within the UO2. A Monte Carlo particle transfer method (with Serpent software) revealed a number of mechanisms by which the enriched Gd2O3 enables higher reactivity late in the fuel’s lifecycle. This was mainly through eliminating the residual reactivity formed in the fuel enabling a higher amount of UO2 loading by opening the way for a lower rate of burnable absorber loading. In addition, an economic evaluation of the use of enriched Gd2O3 as a burnable absorber has been made.
Event Timeslots (1)
Wednesday – 15th September 2021