Process optimization of a closed-chamber distillation system for the recovery of FLiNaK molten salt

Low-pressure distillation has been proposed as a suitable technique for the recovery of carrier salt from molten salt reactor spent fuel. A closed-chamber distillation system, in which the pump is stopped and pressure-induced salt distillation is performed, was arranged for fluoride salt treatment. A stair-step optimization process was demonstrated to improve the recovery efficiency by up to 99%. The pressure change curve was feasible for estimating the distillation process, and a method for displaying the pressure value online in order to determine the end-point was also developed. The decontamination factor of Nd in the condensate salt was deduced to be greater than 100 with 1 wt% NdF3–FLiNaK distillation. The optimal conditions developed in this study showed a high recovery ratio for the fluoride carrier salt and a high separation efficiency for rare earth products.