Permeability of hydrogen in molten salt FLiNaK(LiF-NaF-KF)

Background: Molten salt FLiNaK(LiF-NaF-KF) has potential to be used as heat-transfer fluid of molten salt nuclear reactor, because of its high chemical stability, moderate specific heat and sufficient thermal conductivity. One adverse characteristic was that tritium was produced at relatively high rates in such reactors, which could diffuse through metals at high temperature and thus required to evaluate the behavior of tritium in FLiNaK. Purpose: This study aims to the permeation behavior of hydrogen in molten salt FLiNaK, providing the basis for tritium permeation behavior in molten salt. Methods: Plentiful experiments were conducted in a testing system for permeation and diffusion characteristics of hydrogen isotope in molten salt. Numerical fitting method of experimental results was performed to obtain the hydrogen permeation characteristics in molten salt FLiNaK. Results: The results showed that hydrogen was diffusing as H⁺ species in molten salt FLiNaK. The diffusion coefficients and solubility constants of hydrogen in molten salt FLiNaK can be correlated to D_FLiNaK-H = 1.12 × 10^-4exp(-66.40 × 10³/R_gT) (m²·s^-1) and K_FLiNaK-H = 2.1 × 10^-5exp(-0.94 × 10³/R_gT) (mol·m^-3·Pa^-1/2). Conclusion: The diffusion coefficients and solubility constants of hydrogen in molten salt FLiNaK were derived from the experimental results. (authors)