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Description
The European Spallation Source (ESS), currently under construction in Lund, Sweden, is a multidisciplinary research facility built around the world’s most powerful neutron source. One of the key operational systems in the Target Station is the Radiolysis Gas Treatment System (RGTS), which is designed to control the accumulation of radiolysis and spallation gases generated in the Target Station cooling water. Under irradiation, water radiolysis is the dominant process, producing hydrogen and oxygen, while additional gaseous species may arise from the spallation of water molecules and corrosion products.
The RGTS mitigates associated safety risks by recombining hydrogen and oxygen to form water vapour, which is subsequently condensed and returned to the liquid phase. In the implemented design, the gas phases of three gas–liquid separation tanks are connected in series, forming a closed gas phase circulation system. This configuration enables effective dilution of hydrogen to concentrations well below the lower flammability limit (LFL) and dilution of oxygen to levels well below the limiting oxygen concentration for combustion (LOC). Hydrogen–oxygen recombination is achieved using an OxiGone® 130 Deoxo catalyst supplied by Research Catalysts Inc., which constitutes a key functional component of the system.
Gas concentrations are monitored using an in-line Raman process analyser, with measurements taken upstream and downstream of the catalyst vessel. The system design is tailored to the specific requirements of the ESS Target Station, as it handles activated substances that must remain confined. Accordingly, discharge of gases to the atmosphere is strictly controlled, and sufficient retention time is provided within the system to allow radioactive decay prior to any release.
This paper presents the results of system tests conducted using controlled injections of hydrogen followed by oxygen, together with the corresponding system response measured by the in-line Raman process analyser. The results demonstrate the performance and safety benefits of the RGTS design in meeting the operational requirements of a high power neutron spallation source.