Shifting to a 36-month fuel cycle with advanced moderating burnable absorbers enabling high assay low enriched uranium (HALEU)

Meeting the increasing demand for energy requires more efficient and economical use of resources. Thus, extending the fuel cycle of nuclear reactors that commonly operate on 18-month cycles has become an important area of research both academically and industrially. However, longer fuel cycles necessitate higher fuel enrichment, which poses a greater challenge in terms of reactivity control. In this study, the operation and safety of nuclear power plants in 36-month fuel cycles using High Assay Low Enriched Uranium (HALEU) enriched up to 7.00 wt% were assessed. Moderated Discrete Burnable Absorber Pins (MDBAPs), containing ZrB2 and UB2 have the potential to improve fuel efficiency and fuel economy in long cycles, were introduced as a new burnable absorber solution. Comprehensive evaluations of MDBAPs were undertaken using fuel cycle analyses with the advanced Studsvik CASMO-4/SIMULATE-3 code system. This assessment focuses on understanding the impact of MDBAPs on several key aspects: reactivity feedback parameters, peaking factors, power distribution profiles, and shutdown margin. The results indicate that MDBAPs are a promising burnable absorber option for fuel enriched up to 7.00 wt% (HALEU), demonstrating substantial promise for supporting a 36-month fuel cycle while complying with those operational safety standards and limits.