Role of Fast Neutrons in Minor Actinide Transmutation and Long-Lived Radioactive Waste Reduction in Lead Cooled Fast Reactor: A Systematic Review

The long-term sustainability of nuclear energy relies on the safe management of minor actinides (MAs) and long-lived fission products (LLFPs). The present work aims at systematically evaluating the role of the fast neutron spectrum in the nuclear transmutation of these isotopes in the Lead-cooled Fast Reactors (LFRs) to support the realization of a closed fuel cycle. The present work was performed as a systematic review following PRISMA 2020 guidelines and summarized data from 24 peer-reviewed sources to compare transmutation efficiency and neutronic features. The results indicate that the fast neutrons spectrum in LFRs is a very efficient environment for the actinide destruction by increasing the probability of the fission with respect to the neutron capture. In contrast to thermal reactors, which have positive D-factors and a tendency to accumulate heavier actinides, LFRs have negative D-factors that lead to waste destruction. In particular, an optimal loading of 1.5 wt% MAs provides annual transmutation rates of 15.18% for Am-241 and 13.07% for Np-237 with support ratios larger than one. This configuration is stable for core criticality and neutron flux distribution, but technical challenges remain, including accumulation of Curium isotopes (Cm-244 and Cm-245) and nearly 50% reduction in the effective delayed neutron fraction, affecting safety margins. In conclusion, LFR technology provides clear neutronic benefits for waste reduction over thermal systems but operational strategies should be optimized for curium management and reactor safety to allow evidence-based development of Generation IV reactors for sustainable waste management.