System Design and Analysis of a 900-MW(thermal) Lead-Cooled Fast Reactor

The conceptual design of a 900-MW(thermal) lead-cooled fast reactor (LFR) system for transuranic element (TRU) burning is developed and analyzed using TRU-U-Zr metallic alloy fuel. The design and analysis areas covered are neutronics design, thermal-hydraulic analysis, thermal system design, system mechanical design and analysis, system arrangement, passive decay heat removal system evaluation, and safety analysis for anticipated transient without scram (ATWS) events. Design challenges, solutions, and further research and development items during the conceptual design are described in this paper. Large burnup reactivity swing inherent in the transmutation reactor and irradiation damage to the cladding by high fast neutron fluence are overcome by filling in boron carbide within the tie rods with axial cutbacks. The lead coolant in the reactor pool was estimated to lead to a maximum stress of 125 MPa in the containment vessel. For the long-term cooling behavior upon the concurrent occurrences of a loss of heat sink and a loss of flow, the hot pool temperature is maintained below the design limit of 650°C, which is achieved by an improved decay heat removal design with heat transfer enhancement mechanisms. Analyses of the ATWSs in the investigated core do not reveal any problem from the viewpoints of fuel temperature, cladding temperature, and hot pool temperature. In conclusion, the 900-MW(thermal) LFR system in this study does not pose any significant design-related concerns except for a marginal seismic loading due to the large coolant mass and a verification of the newly introduced design resolutions for long-term decay heat removal.