Tritium production in a fusion reactor is essential for a deuterium-tritium burning plasma source, and designing a lithium-containing breeder blanket is crucial for a closed fuel cycle in an electricity-to-grid power plant. Tritium is a rare resource, currently produced only in a limited number of fission reactors and other low-output facilities. Due to the lack of experimental data in this area, neutronics calculations will guide the design of the first-generation fusion blankets tasked with tritium fuel production as without maximised breeding potential, reactor startup times may need to be postponed due to a low global inventory. This paper describes an optimisation workflow that segments a DEMO-style blanket to allow flexibility in material allocation, along with the necessary validation steps for repeatable results. The developed blanket is tested within the neutronics code OpenMC to evaluate the performance of a hybrid liquid metal–molten salt breeder. FLiBe is found to be an efficient neutron reflector, showing performance increases of 7%, resulting in an overall tritium breeding ratio (TBR) of 1.11, even with a natural abundance of 7.5 % lithium-6. Analysis of the neutron spectral profile indicates a shift towards thermal neutrons when reflected from FLiBe placed at the rear of the design. The use of molten salt as a reflector is novel as a result of its ability to breed tritium and provide a secondary increase in TBR through the reflection of neutrons. A dual system would require more complex engineering, but may offer a solution for compact reactors and/or systems with low lithium enrichment.
This paper explores an optimisation workflow for designing fusion reactor breeder blankets to maximise tritium production. It investigates using the molten salt FLiBe as a neutron reflector, which can increase the tritium breeding ratio by 7%, even with natural lithium-6 abundance. The analysis shows FLiBe's ability to shift the neutron spectrum towards thermal energies, improving tritium breeding.