Reaction rate of beryllium with fluorine ion for Flibe redox control

An experimental effort to apply Flibe (a mixed molten salt of 2LiF + BeF₂) to a self-cooled liquid blanket of a fusion reactor was carried out under a Japan-US collaboration called JUPITER-II. Maintaining Flibe under a reducing atmosphere is a key issue to transform TF to T₂ with a faster reaction rate compared with the residence time in blanket. One of the tasks was to clarify whether or not the redox control of Flibe can be achieved with Be. The dissolution rate of a Be rod and the reaction rate of Be + 2HF = BeF₂ + H₂ in Flibe were experimentally determined. Sufficiently fast rates of the Be dissolution and the reduction reaction of HF to H₂ were clarified by our redox control experiment. Close agreement was obtained between experiments and our simplified complete-mixing model. In particular, the reaction between Be and a F^- ion immediately after their contact was found to be limited by diffusion of the F^- ion.