Development of the package-reactor (1) -reactor for pioneering new nuclear markets-

A new small reactor concept named Package-Reactor has been developed through a joint research of Mitsubishi Heavy Industries, Ltd. and Hitachi, Ltd. Several key designs have been investigated, taking into account both PWR and BWR technologies. The Package-Reactor is designed to attain high reliability, high safety, good maintainability, good operability and low construction cost. To achieve the aims, its nuclear steam supply system adopts the natural-circulation core cooling system, and the reactivity-control-free system, under normal operation. The core assembly is composed of several sub-cores. Each sub-core is housed in a pressure tube called “cassette”. The cycle length is five years, by using UO₂ fuel with 5wt% enrichment. The containment vessel is small and the nuclear steam supply system can be constructed through ground transportation.