Hitachi, Ltd.

Toru Fukui

Shigeo Hatamiya

Yoshiyuki Kataoka

Hiroaki Suzuki

Masataka Hidaka

Michio Murase

Masanori Naitoh

Ryuhei Kawabe

Terufumi Kawasaki

A reactor containment vessel comprises typically a reactor pressure vessel housed in a dry well of the reactor containment vessel, a vent passage through which steam in the dry well is introduced into coolant accommodated in a pressure suppression chamber of the reactor containment vessel, a closed space formed at a position lower than the level of the normal liquid surface of the coolant, a first passage having an inlet opened into the pressure suppression chamber at a level higher than that of the normal liquid surface of the coolant and an outlet opened into the closed space, and a second passage communicating between the closed space and the dry well through a counter flow preventing arrangement for checking the flow directed toward the closed space, and therefore, noncondensable gas and liquid accumulated in the pressure suppression chamber are discharged into the dry well the pressure in which is higher than that in the pressure suppression chamber by making use of a difference in water head increased due to increase of the liquid while allowing fluid to be condensed to newly flow into the pressure suppression chamber from the dry well so as to be condensed, over a long cooling period after the occurrence of an accident of piping fracture in the reactor containment vessel. Owing to condensation, the pressure in the reactor containment vessel can be reduced, and moreover, fluid can make a natural circulation in a closed circuit passing through the dry well, the pressure suppression chamber and the closed space in order without flowing outside the circuit.

Reactor containment vessel

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Hitachi, Japan

Toru Fukui