Research on Core Design and Neutronics Characteristics of Inverted Fuel Lead-Cooled Fast Reactor

To meet the continuous power supply demands of remote areas or islands, this paper proposes a core design scheme for a 5 MW thermal inverted fuel lead-cooled fast reactor and systematically analyzes its neutronics performance. The core adopts an inverted fuel assembly structure, where the coolant flows inside the tubes, significantly enhancing thermal-hydraulic performance and safety. Neutronics calculations performed with the SARAX code demonstrate that the core can operate for 5 effective full-power years without refueling, with the effective multiplication factor keff remaining above criticality throughout its lifetime. The burnup reactivity swing is small, and the power distribution remains uniform, with a power peaking factor below 1.5. All reactivity coefficients are negative, indicating excellent inherent safety. The control system, featuring grouped control assemblies, meets the requirements for redundant shutdown. This design demonstrates outstanding performance in safety, long operational lifetime, and compactness, making it highly suitable for small modular power systems in remote areas.