Chemical behavior of Li2BeF4 molten salt as a liquid tritium breeder

Research results on chemical behavior of Flibe (LiF–BeF2 molten salt) are reviewed, being focused on tritium release and corrosion against structural materials. Tritium release behavior depended on the REDOX potential in the system. The chemical form changed from TF to HT or T2 with increasing H2 partial pressure of the purge gas, and tritium release rate increased also with that, which can be explained well by a tritium release model with an isotopic exchange reaction in the salt. As for the corrosion behavior, a thermodynamic analysis and static experiment were carried out. It was suggested that some kinds of oxide layers can work as a protective scale for ferritic steel, while for V-based alloys, no stable oxide film can exist in the presence of Flibe. REDOX control and/or corrosion-resistant coating should be developed for the corrosion problem. It is concluded that the REDOX control is a key issue for Flibe blanket systems, and future R&D items are pointed out.