Patent Number: 
Section: claims

1. A nuclear power plant comprising:a first reactor containment vessel internally having a dry well and a pressure suppression chamber mutually isolated, said pressure suppression chamber forming a suppression pool being filled with cooling water;a reactor pressure vessel disposed in said dry well in said first reactor containment vessel;a second reactor containment vessel surrounding said first reactor containment vessel and forming a cooling water pool being filled with cooling water at a bottom, said cooling water pool in said second reactor containment vessel adjoining said suppression pool with said first reactor containment vessel intervening between these pools;a steam discharge apparatus; anda reactor cooling apparatus,wherein said steam discharge apparatus has a steam discharge pipe connected to said reactor pressure vessel and immersed in said cooling water in said suppression pool, and a first open/close valve installed in said steam discharge pipe;wherein the reactor cooling apparatus has an evaporator installed in said reactor pressure vessel for evaporating a cooling medium, a condenser disposed in an inner space delimited by said first reactor containment vessel and said second reactor containment vessel above said cooling water pool for condensing steam of said cooling medium generated in said evaporator, a first pipe path connected to said evaporator and said condenser by passing through a side wall of said reactor pressure vessel and a side wall of said first reactor containment vessel, said first pipe path introducing said steam of said cooling medium generated in said evaporator, a second pipe path connected to said condenser and said evaporator by passing through said side wall of said reactor pressure vessel and said side wall of said first reactor containment vessel, said second pipe path introducing a liquid of said cooling medium generated in said condenser to said evaporator, and a second open/close valve installed in either said first pipe path or said second pipe path;wherein said evaporator is disposed above a regular water level in said reactor pressure vessel;wherein said inner space in which said condenser is disposed is communicated with an air discharge portion attached to a ceiling of said second reactor containment vessel, said air discharge portion being disposed above said evaporator, and said inner space is communicated with an air supply portion attached to a side wall of said second reactor containment vessel above a liquid surface of said cooling water pool and below said condenser, said inner space introducing air for removing decay heat generated in fuel assemblies in a core disposed in said reactor pressure vessel,wherein said condenser is a condenser condensing said steam of said cooling medium by said air ascending in said inner space from said air supply portion toward said air discharge portion; andwherein said inner space is configured to provide continuous air flow between the cooling water pool and the air discharge portion. 2. The nuclear power plant according to claim 1, wherein said second pipe path is disposed in said cooling water pool and said suppression pool. 3. The nuclear power plant according to claim 2, wherein a compressor is installed in said first pipe path, and a turbo-motor rotating with steam in said reactor pressure vessel being supplied is connected to said compressor, and said second open/close valve installed in said second pipe path is an expansion valve. 4. The nuclear power plant according to claim 3, wherein a third open/close valve is installed on a steam pipe connected to said reactor pressure vessel and said turbo-motor; and a battery is connected to said third open/close valve. 5. The nuclear power plant according to claim 1, wherein a compressor is installed in said first pipe path, and a turbo-motor rotating with steam in said reactor pressure vessel being supplied is connected to said compressor, and said second open/close valve installed in said second pipe path is an expansion valve. 6. The nuclear power plant according to claim 5, wherein a third open/close valve is installed on a steam pipe connected to said reactor pressure vessel and said turbo-motor; and a battery is connected to said third open/close valve. 7. The nuclear power plant according to claim 1,wherein said air discharge portion includes an air discharge pipe provided with a third open/close valve, and said air supply portion includes an air supply pipe provided with a fourth open/close valve, andwherein a first battery is connected to said third open/close valve and a second battery is connected to said fourth open/close valve.