Permeation of Two-Component Hydrogen Isotopes in Lithium-Lead Eutectic Alloy

We performed an experiment of H and D permeation through Li₁₇Pb₈₃ in the two-component (H+D) system by an unsteady permeation method to clarify interactions between H and D atoms. It was found that H and D permeate independently regardless of the H/D composition ratio in the upstream gas. Dissolution of H and D atoms into Li₁₇Pb₈₃ follows the Sieverts' law in the two-component system in a similar way to the single one. Diffusion of H and D in Li₁₇Pb₈₃ was the rate-determining step in the overall permeation process. An isotope effect of permeability between H and D was around 1.4 in the temperature range from 400°C to 700°C. The ratio of the isotope effect was in proportion to the square root of mass ratio of D to H. Tritium permeation can be estimated in a similar way.