Neutronic performance of ²⁰⁸Pb-Bi eutectic-cooled fast reactor with uranium nitride fuel (enriched ¹⁵N)

Fast reactors (FRs) require more uranium enrichment than LWRs and fuel reprocessing. The solution proposed to address these issues is to use the modified CANDLE burnup scheme on the reactor core. The use of uranium nitride (UN) as fuel was proposed because the UN fuel has several advantages, such as high melting point, high heavy metal density, and large thermal conductivity. However, using UN as a fuel can produce the radioactive isotope 14 C via the reaction 14 N (n, p) 14 C. Therefore, in this study, a neutronic analysis was performed in a modified CANDLE fast reactor employing UN and UN (enriched 15 N) as fuel using SRAC. The modified CANDLE fast reactor fuelled with UN (99% 15 N) has a higher k eff than the UN-fuelled reactor with similar parameters. Similarly, the atomic density of fissile nuclides and power density are higher because the 15 N isotope has a smaller neutron capture cross-section than the 14 N isotope.