Tritium release and trapping in austenitic stainless steels: Role of microstructure and desorption anneal

The behavior of hydrogen and its isotopes in materials is a major concern in future nuclear systems both for the predictive analysis of the role of H, D, T in the environmental degradation of structural materials, for the confinement and inventory of tritium, and for the management of tritiated wastes. This study is focused on the characterization of the effect of the alloy microstructure, of desorption anneal and of oxide films on the tritium behavior (desorption kinetics, trapping, residual concentration) in various austenitic stainless steels. Different techniques (high temperature extraction of hydrogen, beta counting of tritium in massive samples) were used to study: the tritium absorption and desorption in several stainless steels, the role of the annealing conditions (temperature/time) on the tritium residual concentration and desorption flow, and the role of microstructural defects and of oxide films on the diffusion and trapping of tritium. (authors)