Papers by Author: Yuji Yamauchi

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Authors: Tomoaki Hino, Yuji Yamauchi, Kiyohiko Nishimura, Yoshio Ueda
Abstract: In-vessel tritium inventory in fusion reactors has to be reduced from a view point of safety in fusion reactors. It is required to evaluate the amount of tritium retained in tungsten plasma facing walls. The plasma discharge with hydrogen isotope (deuterium) was conducted to evaluate the tritium retention in tungsten. The glow discharges using helium, neon and argon were performed after the deuterium discharge to reduce the deuterium retention. The use of inert gas discharge little reduced the deuterium retention. Namely, the inert gas glow discharge is not useful to reduce the tritium inventory. The deuterium glow discharge significantly replaced the hydrogen in the tungsten wall into the deuterium. Thus, the deuterium glow discharge is quite useful to reduce the tritium inventory through the hydrogen isotope exchange. The use of neon or argon glow discharge followed by deuterium discharge can more reduce the tritium inventory. In addition, the tritium inventory can be easily reduced if the wall baking with a temperature of 700-800K is conducted.
Authors: Akira Yamauchi, Yuji Yamauchi, Yuko Hirohata, Tomoaki Hino, Kazuya Kurokawa
Abstract: Hydrogen dissolved in the Cr2O3 scale formed on the stainless steel in the H2O-containing atmospheres is observed by TDS (thermal desorption spectroscopy) measurements. The amount of dissolved hydrogen in the Cr2O3 scale reaches a maximum about 0.32 mol% when the H2O concentration in the gas reaches 20%. It was found from GDS (glow discharge spectroscopy) measurements that hydrogen may exist at the oxide scale / substrate interface or in Cr2O3 scale bounded that interface. However, results from the Vickers hardness and the observation of scale morphology by SEM (scanning electron microscopy), hydrogen dissolved in the Cr2O3 scale would have little effect on a decrease in the mechanical property of the Cr2O3 scale. Therefore, hydrogen dissolved in the Cr2O3 scale may not be main factor of the deterioration of the Cr2O3 scale.
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