SAFETY ISSUES OF REDUCED-MODERATION WATER REACTOR AND HIGH TEMPERATURE GAS-COOLED REACTOR DEVELOPED AT JAERI

摘要

As advanced reactors, reduced-moderation water reactor (RMWR) and high temperature gas-cooled reactor (HTGR) are being developed at the Japan Atomic Energy Research Institute (JAERI). RMWR aims at achievement of a high conversion ratio and negative void reactivity coefficients with MOX fuels, based on well-experienced water-cooled reactor technology. Safety issues important for RMWR are thermal hydraulic safety on the tight-lattice core including stability, highly enriched MOX fuel behaviors at high burn-up, and plant system safety including passive components. Related experiments and analysis have been conducted to obtain information required for the design optimization and safety confirmation. Based on the experiences of design, construction and operation of High Temperature Engineering Test Reactor (HTTR), design study on the Gas Turbine High Temperature Reactor 300 (GTHTR 300) has been conducted, with greatly simplified system, including safety systems due to its inherent safety. As major safety issues, severe accident free and demonstrable safety are proposed. This new safety philosophy is to avoid most accidents and to greatly reduce the probability of severe accidents compared with that of current power reactors.