Analysis of diffusion and dissolution of two-component hydrogen (H + D) in lead lithium

A lead–lithium eutectic alloy (Pb–Li) is one of the most promising candidate materials for the liquid blanket of an advanced fusion reactor. We have experimentally determined mass-transfer properties by an unsteady permeation method, which data are necessary to design a system to recover tritium (T) from a Pb–Li blanket. An experiment of simultaneous H and D permeation through Li17Pb83 is performed to clarify interactions between atoms in the two-component permeation process. The experimental results are analyzed by a model of one-dimensional or two-dimensional permeation through Li17Pb83. The major permeation proceeds in the longitudinal direction of the present system, and the ratio of hydrogen leak in the radial direction is evaluated using the simulation. As a result, it was found that H and D atoms permeate independently regardless of the H/D component ratio within the present experimental conditions. The permeability and diffusivity of H are 1.4 times higher than that of D. The solubility of H is close to that of D. The isotope effect in diffusivity is in proportion to the square root of the mass ratio of D to H. When these data can be extended to the case of T, T permeability and diffusivity is predicted as 1/1.7 times lower than that of H in the temperature range from 773 K to 973 K.

► We perform one-dimensional and two-dimensional permeation analysis through Li–Pb.
► We obtain diffusivity and solubility in two component H + D permeation through Li–Pb.
► H and D permeate independently regardless of the H/D component ratio.
► Isotope effect between H and D is diffusion through Li–Pb in permeation process.
► The obtained data can be extended to the tritium case from 773 K to 973 K.