Removal of tritium from 316 stainless steel (4) : Modeling of hydrogen trapping and release in chemically etched surface of tritium occluded stainless steel sample

When a stainless-steel sample occluded with tritium was dissolved the thickness a few 10 μm chemically, it was observed by a coauthor, Murata that tritium concentration at the newly formed top surface increased with time, while tritium release occurred from the surface to the gas phase. In this paper, a model to explain tritium accumulation and release at the etched surface is described. For the modeling, it was assumed that some of the segregated tritium atoms from the bulk to the surface are trapped on adsorption sites and become immobile, and that some of them are released from the top surface to the gas phase. By solving a one-dimensional diffusion equation, the rates of accumulation and release of tritium were estimated, and compared with experimental results. The comparison showed good agreement between experimental result and theoretical calculation