Analysis of exhausted gas in JT-60 deuterium operation

In a nuclear fusion reactor with carbon-based plasma facing material, tritium inventory inside the vacuum vessel is one of the critical problems because the reactor operation may be restricted by the tritium which piles up in the carbon tile. From this point of view, exhaust gas analysis was conducted in JT-60 operation and it was successfully demonstrated. Tritium was measured with an ion chamber and water bubbler. Exhausting gas composition and chemical form was measured with a micro gas-chromatograph and a residual gas analyzer. Initial results were obtained for deuterium plasma discharges, helium Taylor discharges and helium glow discharges. Removed tritium from the vacuum vessel in an operating day corresponded to about 8% of the generated tritium during the tokamak discharges in the day. The chemical forms of the removed tritium mainly consisted of elemental gas. Tritium removal rates were compared for glow discharges using H₂, He and Ar gases. Effectiveness of wall conditioning with H₂ was confirmed.