Hitachi, Ltd.

Hitoshi Tate

Kenji Tominaga

Kumiaki Moriya

Tadashi Fujii

Fumio Totsuka

Tetuo Horiuchi

Nuclear reactor and nuclear reactor cooling facilities, and also a nuclear power generation plant and a method of its operation are disclosed. The reliability of cooling function at the time of anticipated accidents is substantially improved through enhancing a cooling efficiency of the gas in the reactor container without resorting to any particular active means. Guide structure is provided for circulating the gas present in the reactor container so as to accelerate heat removal therefrom to the outside through the surface of the reactor container. The arrangement includes an internal structure for retaining a coolant in the reactor container; and upper space portion disposed over the internal structure; a first gas flow passage for directing downward the gas present in the above upper space portion; and a second gas flow passage connecting the first gas flow passage with the upper space portion. Further, circulation structure is provided for circulating the gas in the above reactor container through utilization of the decay heat of the core. By means of the natural circulation through the wet well vapor phase including the upper space portion, with nitrogen gas (N.sub.2) rendered ubiquitous in the wet well vapor phase portion thereby the gas temperature being evenly distributed, it is possible to substantially improve the core decay heat removal efficiency in the reactor container by air cooling.

Nuclear reactor with cooling apparatus and method

The invention is directed to a natural circulation reactor having a reactor pressure vessel with a core housed therein, the core being disposed in such a location that a top portion of the core is submerged under coolant even in the event that any pipe connected to the reactor pressure vessel is broken and then a coolant level in the reactor pressure vessel is lowered due to flushing. This permits the reactor core to be submerged under coolant even in the event of breakage of any pipe connected to the reactor pressure vessel, ensuring to eliminate a possibility that the top portion of the reactor core is exposed temporarily during an intermediate period before actuation of an accumulated coolant injection system to start injecting of the coolant into the reactor pressure vessel after the end of flushing.

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Hitachi, Japan

Hitoshi Tate