Speaker
Koki Yakusiji
(Osaka university)
Description
The use of bare Reduced Activation Ferritic Martensitic (RAFM) steels has been proposed for the first wall in a reactor [1]. Thus, it is necessary to understand the performance of RAFM steels under fusion-relevant condition. To date, the effects of simultaneous irradiation of hydrogen isotopes and He in F82H haven’t been examined in detail. We previously examined hydrogen retention properties, and reported systematic reduction due to simultaneous D+He irradiation [2]. In this contribution, we report on the sputtering behavior and accompanying surface morphology changes.
Experiments were performed over the temperature range of 500-1000 K, consistent with the anticipated operating temperatures of the blanket region. Simultaneous H+He or H-only irradiation was performed with 1 kV extraction voltage. The irradiation fluence was 1×102424 H/m22. He % in the ion beam was 0.5 %. Mass loss was measured before and after irradiation to determine erosion. Surface morphology changes were observed by SEM/FIB. RBS was used to quantify the near surface W concentration at NIFS.
From SEM images, surface roughening was observed at T > 750 K in both H-only and H+He irradiations. The effect of He was minor. At 865 K, the roughness increases dramatically with the peak to peak differences in the order of ~μm, which is much greater than the ion implantation zone ( <10 nm). Correspondingly, the sputtering yield of F82H increases with increased surface roughening. However, the sputtering yield for H+He irradiation was systematically higher compared to H-only irradiation. This is attributed to lower W surface enrichment at the surface as confirmed from RBS measurements.
This work is performed with the support and under the auspices of the NIFS Collaboration Research Program (NIFS**15KEMF072**)
[1] D. Maisonnier et al., Fusion Engineering and Design 75-79 (2005) 1173-1179
[2] K. Yakushiji et al., Physica Scripta T167 (2016) 014067
Co-authors
Akio Sagara
(NIFS, Gifu, Japan)
Heun Tae Lee
(Osaka university, Osaka, Japan)
Kenzo Ibano
(Osaka university, Osaka, Japan)
Koki Yakusiji
(Osaka university, Osaka, Japan)
Makoto Oya
(Osaka university, Osaka, Japan)
Masayuki Tokitani
(NIFS, Gifu, Japan)
Yoshio Ueda
(Osaka university, Osaka, Japan)
Yukinori Hamaji
(NIFS, Gifu, Japan)
