Design and safety analysis of a lead-cooled research reactor

This compilation thesis presents work focused on the design and safety analysis of the small lead-cooled research and demonstration reactor SUNRISE-LFR–the first step toward the construction of a next-generation reactor in Sweden. Two versions of SUNRISE-LFR are introduced—the second necessitated by the lack of access to uranium enriched above 10 wt.% 235U/U. Neutronic characterization is performed using the Monte Carlo code Serpent 2, while the reactors’ behaviours during design extension conditions (DECs) are analysed using the in-house developed code BELLA and an established fast reactor safety code, SAS4A/SASSYS-1. An analytical method for designing a passively safe lead-cooled reactor is derived and used to propose the core configuration of SUNRISE-LFR. This method is subsequently expanded into a semi-analytical framework for designing the Reactor Vessel Auxiliary Cooling System (RVACS), aimed at ensuring fuel cladding survivability during unprotected station blackout (USBO) transients. The model is further extended to evaluate the impact on system temperatures during USBO transients when using nuclear fuel with different actinide compositions. It is shown that actinide compositions with low concentrations of americium and the plutonium isotope 241Pu are beneficial for cladding integrity. Finally, the thesis assesses the impact of coolant circulation on the total neutron activation of the lead coolant over the reactor’s operational lifetime. It is demonstrated that a sufficiently pure lead vector—particularly one with low silver content—could allow the coolant to be exempted from radiological control within a reasonable time frame, thereby avoiding the need for disposal in a final repository. This thesis serves as both a foundation and a stepping stone for the continued development, licensing, and eventual construction of a lead-cooled reactor in Sweden.