Surface effects on hydrogen permeation through fusion reactor materials

A new analytical model has been developed to analyze the kinetics of hydrogen permeation through a membrane. Hydrogen permeation problem is important in the R and D of fusion reactors. This model takes into account the surface impurity and roughness effects in addition to migration and diffusion in the bulk. The steady state permeation rate, the transient response and their pressure dependences can be analyzed with the present model. The experimental results of the hydrogen permeation through vanadium were analyzed with this model and the rate-determining step was evaluated to be the combination of the surface adsorption-desorption and the bulk diffusion where the former being the dominant process. The steady state permeation rate, the transient response, their pressure dependences and the effects of sputtering of either specimen surface upon these were reasonably analyzed and explained with the present model. The effectiveness and the limit of this model are discussed. (author)