To consider carbon balance and hydrogen isotope balance in the fuel cycle system and tritium safety management of a fusion reactor, the evaluation of carbon and hydrogen isotope accumulation not only in the vacuum vessel but also in the exhaust system is necessary. In the present work, type 316 stainless steel substrates were installed at 4 locations in the exhaust duct of the Large Helical Device (LHD) during the 13th experimental campaign. By using the combustion method, the amount of carbon slightly adhering to the substrates, which cannot be measured by electric microbalances, was successfully quantified to be 2 μg/cm2. The hydrogen release behavior from the substrate was consistent with that from carbon deposition layer formed by hydrogen plasma sputtering. H/C ratio on the substrate was estimated to be about 1-1.5. Hydrogen incorporated into the metal deposit formed from type 316 stainless steel in the sputtering-deposition device in the laboratory can remain in the deposit even under high vacuum condition in the exhaust duct for a long period.
All Science Journal Classification (ASJC) codes
- Condensed Matter Physics