Fluoride-salt-cooled high-temperature reactors: Review of historical milestones, research status, challenges, and outlook

The fluoride-salt-cooled high-temperature reactor (FHR) is a Generation IV nuclear energy system with huge potential for further development. Owing to its unique advantages, such as inherent safety, high economical potential, small modular design, environmental adaptability, and nonproliferation, FHRs have been the focus of considerable attention. In this study, the history and characteristics of FHR are reviewed first, including the concept initiation and active exploration stages. Then, the research status of FHR is introduced, which is about the state of the art in primary coolant systems, structural materials, key equipment, energy conversion systems, direct reactor auxiliary cooling systems, nuclear fuel, tritium control strategies, and experimental studies. Furthermore, the challenges faced by FHR technology are summarized, including corrosion of structural materials, optimization of energy conversion systems, solidification of fluoride salts, control of tritium, control of beryllium contamination, enrichment of lithium fluoride-beryllium fluoride salt, design of core refueling, and operation and control of pebble bed reactor. Based on the above, the focuses of research on FHR design are discussed, and areas of study for future development of FHR technology are recommended. This paper aims to provide a reference for the research and development of FHR in the future.