Abstract The application of Flibe (2LiF + BeF 2 mixed molten salt) to a blanket material of force-free helical reactor (FFHR-2) was discussed based on our recent experiments on redox control of Flibe by Be and on hydrogen permeation through Flinak (0.465LiF + 0.115NaF + 0.42 KF mixed molten salt) as a fluid simulant of Flibe. The two experimental works were carried out under the collaboration work of JUPITER-II. To maintain Flibe in the blanket loop under reduction condition is a key issue to transform TF to T 2 with a fast reaction rate. In order to achieve that, proper rates of Be dissolution and reduction reaction of TF to T 2 in Flibe have to be established in the self-cooled blanket. The overall material balance of tritium in the FFHR-2 system was discussed in terms of the tritium permeation through Flibe and the tritium recovery rate.