Development of a compact real-time process gas analysis system for tritium accountancy for a DEMO fusion reactor by an application of laser Raman spectroscopy

•A compact real-time gas analysis system for tritium accountancy using laser Raman system for a DEMO is developed.•Preliminary test results of the proto-type of the system showed the feasibility for remote hydrogen isotope gas analysis.•A trial of tracking ability for accountancy under variations of concentration under a constant flow was well demonstrated. In the fuel cycle of ITER and the future DEMO fusion reactors, which has many processes of tritium provision/ consumption/recovery/loss, such as, fueling, DT burning, vacuum pumping, purification, isotope separation and storage, detritiation, etc., tritium accountancy control will be required in its operation and safety management. In contrast to ITER, which will have frequent intervals between operations, a DEMO fusion reactor generating electricity must be operated continuously for long periods. This requires a dynamic tritium accountancy control, especially at the mass balance area boundary of the Tokamak including the vacuum vessel. To make a dynamic tritium accountancy system for a DEMO fusion reactor, based on our past work carried out during the ITER EDA, we are developing a new compact hydrogen isotope gas analysis system by the application of laser Raman spectroscopy advanced by technological progress in laser and detection systems. A prototype system has been made at TPL using a semiconductor laser with a Peltier-cooled CCD detector, with a simple optical system. Results of some preliminary tests being conducted to confirm sensitivity and accuracy under static and dynamic conditions are presented.