Development of the package-reactor (2) -core characteristics-

A new small reactor concept named the Package-Reactor has been jointly developed by Hitachi, Ltd. and Mitsubishi Heavy Industries, Ltd. The reactor technology was built from that of conventional LWRs. The reactor core consists of 12 cassettes containing fuel rods with a similar design to that of PWR fuel rods. Each cassette has about a 0.4 m outer diameter and they are fixed with about 0.5 m pitch to each other in the atmospheric pressure condition. A tube-type control cluster was developed. It can decrease the rise of reactivity for the one-rod-stuck condition. An advanced cassette design was studied in which the down-comer is placed at the center of the fuel region. This concept, which improves neutron economics and the cold shutdown margin, will increase the marketability of the Package-Reactor. An operation period of more than 8 years can be achieved with UO2 fuel enrichment of 5.0wt%.