Speaker
Prof.
Mizuki Sakamoto
(Plasma Research Center, JpUTsukuba)
Description
Tungsten is a candidate material for plasma facing components of DEMO as well as divertor plates of ITER, because it has favorable properties such as a very low solubility for hydrogen isotopes. However, surface condition of the plasma facing material is certainly changed by plasma-wall interaction (PWI). Such a surface modification could affect a property of H isotope retention which is a key concern for safety hazards as well as particle control. It is important to investigate relation between change in microstructure due to PWI and H isotope retention but such studies are few. In this paper, two kinds of experiments have been carried out to study H isotope retention in surface-modified W taking microstructure of the surface modification into account using a compact PWI simulator APSEDAS. One is damage level dependence for W irradiated by 2.4 MeV Cu^2+ ions as surrogate of neutron irradiation. The other is D fluence dependence for W with a He bubble layer, W with a W deposited layer and pure W.
Hydrogen isotope retention in W irradiated by 2.4 MeV Cu^2+ ions as surrogate of neutron irradiation increased significantly with the damage level up to 0.4 dpa and then saturated. A new desorption peak appeared at ~840 K in a thermal desorption spectra due to the heavy ion irradiation, which is attributed to nano-voids and vacancy clusters. On the other hand, the D retention in W with He bubbles became saturated for fluence over 1 x 10^25 D m^-2, although retention in pure W increased with square-root dependence of the fluence. Retention in W with a W deposited layer with the thickness of ~30 nm was ~5 times lower than that of pure W. The surface modifications of He bubbles and W deposition seem to play a role of diffusion barrier for the mobile D atoms.
| Country or International Organization | Japan |
|---|---|
| Paper Number | MPT/P5-14 |
Primary author
Prof.
Mizuki Sakamoto
(Plasma Research Center, JpUTsukuba)
Co-authors
Mr
Akihiro Terakado
(Plasma Research Center, JpUTsukuba)
Dr
Hideo Watanabe
(Research Institute for Applied Mechanics, Kyushu University)
Mr
Hiroki Tanaka
(Plasma Research Center, JpUTsukuba)
Dr
Masayuki TOKITANI
(National Institute for Fusion Science)
Prof.
Naoaki Yoshida
(Research Institute for Applied Mechanics, Kyushu University)
Dr
Naomichi Ezumi
(Plasma Research Center, JpUTsukuba)
Mr
Shuntaro Ino
(Plasma Research Center, JpUTsukuba)
Prof.
Yousuke Nakashima
(Plasma Research Center, University of Tsukuba)
