Conceptual core design study of the Very High Temperature gas-cooled Reactor (VHTR); Upgrading the core performance by using multihole-type fuel

Ohashi, Kazutaka; Nishihara, Tetsuo ; Kunitomi, Kazuhiko ; Nakano, Masaaki*; Tazawa, Yujiro*; Okamoto, Futoshi*

Interests on the development of the Very High-Temperature Gas-Cooled Reactor (VHTR), of which the reactor outlet temperature is 950C or much higher, are recently increasing world-widely and it was selected as one of the candidate reactor types of the GIF. Japan Atomic Energy Agency has already initiated R&D efforts on the electricity and hydrogen co-generation plant with VHTR system, GTHTR300C. Although technical feasibility of its VHTR reactor using Pin-in-block fuel, which has experience to be already used in the HTTR, has been shown fundamentally, more improvements of the core performances, such as decrease of the occupational exposure doses during the plant maintenance, are desired. This report presents the results of the conceptual core design study using Multi-hole type fuel and the study on the occupational exposure doses. The latter results shows much better plant maintainability compared to the previous results of the GTHTR-300.