Function of water molecule for tritium behavior on the water-metal boundary

Hayashi, Takumi; Nakamura, Hirofumi; Isobe, Kanetsugu; Kobayashi, Kazuhiro; Oyaizu, Makoto; Yamanishi, Toshihiko; Ishikawa, Hirotada*; Oya, Yasuhisa*; Okuno, Kenji*

How to confine tritium within high temperature breeding blanket is the key issue for safety and fuel economy of the fusion reactor. Specially, tritium permeation into cooling water is very important, however, there is little report of the systematic experiment comparing with that into gaseous coolant. In our recent report, a series of tritium transportation experiments into water was performed through pure iron piping samples, which contained more than 1 kPa of pure tritium gas and fixed inside the water jacket under controlled temperature and pressure. Chemical species of tritium in water were measured during the experiment until reaching enough stable permeation, and tritium distribution/situation on the metal surface layer was also measured using autoradiography etc. after the experiment. The results showed clearly that tritium permeated constantly even after growth of magnetite layer with more than 1 micro-meter, though chemical species drastically changed from HT to HTO. In order to discuss more detail of tritium behavior on the water-metal boundary, a series of tritium transportation experiments into humid atmosphere was performed through pure iron piping using same set of previous one for cooling water. In this paper, tritium behavior on the boundary surface and the function of water molecule for the tritium behavior are discussed.