First experimental results of HYDREX operation in hydrogen removal from helium for fusion applications

The tritium removal from gaseous effluents represents a key issue for the deployment of future fusion power plants even more when tritium is present in the order of parts per million. A promising system derives from the fission experience, where oxidizing beds combined with Zeolite Molecular Sieve (ZMS) beds are adopted to purify helium coolant and cover gas. In this work, an integral helium purification process involving these technologies is studied in the Hydrogen Extraction (HYDREX) experimental facility assuming boundary conditions relevant for the Coolant Purification System of the EU-DEMO Helium Cooled Pebble Bed Breeding Blanket. The experimental campaign demonstrates the efficient purification performance allowing the removal of 96 % of the hydrogen. Then, a proper regeneration procedure is experimentally investigated providing a satisfactory restoring of the adsorption capability of the zeolite material. Some open aspects are individuated, mainly related to the uneven distribution of the flow through the ZMS bed causing an earlier saturation of the bed and a not completed regeneration of the zeolite material. Furthermore, a huge release of hydrogen in the first minutes of the regeneration is experienced due to the not completed oxidation. The results obtained in this work are relevant for the definition of further experimental investigations and as guidelines for the design of gas detritiation systems.