National Research and Development Institute for Cryogenics and Isotopic Technologies – ICSI Rm. Valcea, Code 240050, Uzinei Street no. 4, P.O. Box Râureni 7, Valcea, Romania

ABSTRACT

The interest about hydrogen permeation through metals is very old, and scientific literature regarding the transport parameters of hydrogen through various materials is relatively abundant. However, there are still unresolved aspects related to the modelling of synergistic isotopic effects observed experimentally in the case of multi-isotope permeation (H, D, T) through metals. These effects in permeation of competing species, by which an isotope influences the permeation of another isotope, can be of great interest in the problem of minimizing the tritium permeation through the structural and functional materials of the fusion reactors, an extremely important issue at least in terms of radiological safety (in operation, and for population and environment), because the public acceptance and the safety of fusion-based energy can be strongly dependent on the ability to control the permeation of tritium. For a reactor based on deuterium-tritium fusion, isotopic effects should be considered because both isotopes are fuel constituents. The purpose of this paper is to analyse the modelling approaches proposed so far in the study of the permeation of hydrogen and its isotopes and to highlight the unresolved issues related to the synergistic isotopic effects in the case of competing permeation of the multi-isotope systems. We will also talk about the goals we have set out regarding our own approaches to investigate these effects in a new research project that we have committed to.

Keywords: hydrogen isotope, deuterium, tritium, isotope effect, permeation, diffusion, solubility, membrane, recombination, fusion.