Conceptual Core Design Study of the Very High Temperature Gas-Cooled Reactor (VHTR) Upgrading the Core Performance by Using Multihole-Type Fuel

Interest on the development of the Very High Temperature Gas-Cooled Reactor (VHTR), of which the reactor outlet temperature is 950°C or much higher, has recently been increasing worldwide, and it was selected as one of the candidate reactor types in the Generation IV Reactor System International Forum. The Japan Atomic Energy Agency (JAEA) has already initiated R&D efforts on the electricity and hydrogen cogeneration plant with the VHTR system, GTHTR300C. Although the technical feasibility of the VHTR using pin-in-block fuel, which has already been used in the High-Temperature Engineering Test Reactor (HTTR), has been shown fundamentally, more improvements in core performances, such as a decrease in the occupational exposure doses during plant maintenance, are desired. This report presents the results of the conceptual core design study using multihole-type fuel and the study on the occupational exposure doses. The latter results show much better plant maintainability compared with the previous results on the GTHTR300.