Deuterium/tritium behavior in Flibe and Flibe-facing materials

Experimental studies to investigate the behavior of deuterium and tritium in the molten salt Flibe (2LiF·BeF2), have been conducted as part of the Japan–US joint research program (JUPITER-II). Measurements of deuterium transport were made in a cylindrically symmetric, dual permeation probe assembly containing 400 cc of Flibe. An exact analytical transport solution in cylindrical coordinates was fit to the measured permeation data, and this analysis derived deuterium diffusion and solubility coefficients of 8.0×10−10 m2/s and 3.1×10−4 mol/m3Pa at 600 °C, respectively, and 3.0×10−9 m2/s and 1.0×10−4 mol/m3Pa at 650 °C. The diffusion coefficients were about a factor of two less than previous results derived from capillary-reservoir diffusion measurements with tritium. Solubility results were significantly greater than previously measured for D2 but they were comparable to those for DF in Flibe. The results suggest that the dominant deuterium transport species in Flibe was D+F− for these experiments.