Diffusion, trapping and release process in the first-wall of thermonuclear fusion reactor

Diffusion, trapping and release processes which occur during the operation of a thermonuclear fusion reactor may affect the plasma performances. A theoretical study, coupled with large-scale experimental research, was carried out in order to learn diffusion, trapping and desorption characteristics under the relevant conditions. The results of both theoretical and experimental studies show that a large quantity of hydrogen isotopes atoms will be accommodated in trapping sites at relatively high binding energy. It is also shown that thermal cycling can affect trapping and release characteristics. The results indicate that trapping and release processes might drastically affect fuel, i.e., hydrogen isotopes, balance during the operation of a fusion reactor. An enhanced helium release due to hydrogen introduction was observed. This release probably occurs due to blister formation, growth and exfoliation, as was observed by scanning electron microscopy. The effect of hydrogen on blister formation and growth can be explained by several mechanisms, such as hydrogen-induced interbubble fracture. This phenomenon can be referred to as hydrogen enhanced helium release (HEHR).