Helium leak and chemical impurities control technology in HTTR

Tochio, Daisuke ; Shimizu, Atsushi ; Hamamoto, Shimpei  ; Sakaba, Nariaki 

Japan Atomic Energy Agency (JAEA) has designed and developed High Temperature Gas-cooled Reactor (HTGR) hydrogen cogeneration system named GTHTR300C. The helium gas is used as the primary coolant in HTGR. The helium gas is easy to leak, and the primary helium leakage should be controlled tightly from the viewpoint of preventing the release of radioactive materials to the environment. Moreover from the viewpoint of preventing the oxidization of graphite and metallic material, the helium coolant chemistry should be controlled tightly. The primary helium leakage and the helium coolant chemistry during the operation is the major factor in the HTGR for commercialization of HTGR system. This paper shows the design concept and the obtained operational experience on the primary helium leakage control and primary helium impurity control in the HTTR. Moreover the future plan to obtain the operational experience on these controls for commercialization of HTGR system is shown.