Tritium Breeder Materials for Nuclear Fusion Reactors: Current Status and Future Directions

Nuclear fusion energy, as well as nuclear fission energy, is considered as a clean energy with regar to its $C{O_2}$ emissions. Compare with fission energy, fusion energy has higher energy density and no spent fuel is discharged. A fusion reactor needs operate under the conditions of high temperature, high pressure, and tight sealing, and the excellent physical and mechanical performances of the structural materials in the reactor are required. The tritium breeding zone is a key component in a fusion reactor acts as the production of tritium, breeding of neutron, and transferring of heat. The lithium-based alloys, which have high tritium breeding ratio, are usually selected as the materials in this zone. In this paper, the development of various liquid and solid lithium materials is introduced. Liquid lithium materials mainly include liquid lithium, molten lithium compounds, and liquid lithium-lead alloy. Solid lithium materials cover lithium-based ceramics oxides, and lithium-lead alloy with high melting points. The tritium breeding ability, the durance characteristics, and the compatibility of these materials are comprehensively compared and analyzed. Among these materials, solid lithium-lead alloy, although in the stage of theoretic studies, is still considered to be a very promising material used as the tritium breeding agent. This paper will provide the insights into the further development of tritium breeding materials with better performances in the future.