DIFFUSION, TRAPPING AND RELEASE PROCESS IN THE FIRST-WALL OF THERMONUCLEAR FUSION-REACTOR

Diffusion, trapping and release processes which occur during the opera tion of a thermonuclear fusion reactor may affect the plasma performan ces. A theoretical study, coupled with large-scale experimental resear ch, was carried out in order to learn diffusion, trapping and desorpti on characteristics under the relevant conditions. The results of both theoretical and experimental studies show that a large quantity of hyd rogen isotopes atoms will be accommodated in trapping sites at relativ ely high binding energy. It is also shown that thermal cycling can aff ect trapping and release characteristics. The results indicate that tr apping and release processes might drastically affect fuel, i.e., hydr ogen isotopes, balance during the operation of a fusion reactor. An en hanced helium release due to hydrogen introduction was observed. This release probably occurs due to blister formation, growth and exfoliati on, as was observed by scanning electron microscopy. The effect of hyd rogen on blister formation and growth can be explained by several mech anisms, such as hydrogen-induced interbubble fracture. This phenomenon can be referred to as hydrogen enhanced helium release (HEHR).