Patent Number: 
Section: claims

1. A nuclear power plant comprising:a core;a reactor pressure vessel that houses the core;a containment vessel that houses the reactor pressure vessel;a containment vessel head of the containment vessel;a reactor building that surrounds at least part of the containment vessel;a sidewall that surrounds a periphery of the containment vessel head and extends upward;a bottom portion that is connected to a lower end of the sidewall and is connected to the containment vessel;a reactor well that is formed by the containment vessel head, the sidewall, and the bottom portion;a reactor well upper lid that is provided in an upper portion of the reactor well;an operation floor that is joined to an upper end of the sidewall and is provided on a periphery of the sidewall;an operation floor area wall that surrounds a periphery and upper portion of the operation floor to form an operation floor area and is part of the reactor building;a standby gas treatment system including:a suction pipe to take in gas inside the reactor building;an exhaust fan to chive the gas that the suction pipe takes in;a standby gas treatment system exhaust pipe to release the gas that the suction pipe takes in to an environment outside the reactor building via the exhaust fan;a heater that is disposed between the suction pipe and the standby gas treatment system exhaust pipe and uses electric power to heat the gas that the suction pipe takes in; anda filter to filter the gas heated by the heater and to send the gas to the standby gas treatment system exhaust pipe; anda reactor well exhaust section to release the gas inside the reactor well to the environment without releasing the gas into the operation floor area in an event of a predetermined accident. 2. The nuclear power plant according to claim 1, whereinthe reactor well exhaust section includes:a reactor well exhaust pipe having a first end that is opened inside the reactor well and a second end that is opened in the environment, the reactor well exhaust pipe passing through the sidewall; anda reactor well exhaust pipe isolation valve that is provided on the reactor well exhaust pipe. 3. The nuclear power plant according to claim 1, whereinthe reactor well exhaust section includes:a reactor well exhaust pipe having a first end that is opened inside the reactor well and a second end that is opened in the environment, the reactor well exhaust pipe passing through the reactor well upper lid;a reactor well exhaust pipe isolation valve that is provided on the reactor well exhaust pipe; anda flange that is provided on the reactor well exhaust pipe. 4. The nuclear power plant according to claim 1, whereinthe reactor well exhaust section includes:a reactor well exhaust pipe having a first end that is opened inside the reactor well and a second end that is connected to the standby gas treatment system exhaust pipe, the reactor well exhaust pipe passing through the reactor well upper lid;a reactor well exhaust pipe isolation valve that is provided on the reactor well exhaust pipe; anda flange that is provided on the reactor well exhaust pipe. 5. The nuclear power plant according to claim 1, further comprisinga stack that surrounds an outer periphery of the standby gas treatment system exhaust pipe and extends in an up-down direction, with an upper end thereof being opened, whereinthe reactor well exhaust section includes:a reactor well exhaust pipe having a first end that is opened inside the reactor well and a second end that is opened inside the stack and outside the standby gas treatment system exhaust pipe, the reactor well exhaust pipe passing through the reactor well upper lid;a reactor well exhaust pipe isolation valve that is provided on the reactor well exhaust pipe; anda flange that is provided on the reactor well exhaust pipe in such a way as to connect parts of the reactor well exhaust pipe together in a detachable manner. 6. The nuclear power plant according to claim 1, wherein:outside the sidewall, a passive cooling system pool is formed in such a way that a pool water surface is formed inside and an area above the pool water surface is opened to the environment; andthe reactor well exhaust section includes a reactor well exhaust pipe having a first end that is opened inside the reactor well and a second end that is opened above the pool water surface, the reactor well exhaust pipe passing through the sidewall. 7. The nuclear power plant according to claim 6, further comprisinga reactor well exhaust pipe isolation valve that is provided on the reactor well exhaust pipe. 8. The nuclear power plant according to claim 1, wherein:outside the sidewall, a passive cooling system pool is formed in such a way that a pool water surface is formed inside and an area above the pool water surface is opened to the environment; andthe reactor well exhaust section includesa reactor well exhaust pipe having a first end that is opened inside the reactor well and a second end that is opened above the pool water surface, the reactor well exhaust pipe passing through the reactor well upper lid;a reactor well exhaust pipe isolation valve that is provided on the reactor well exhaust pipe; anda flange that is provided on the reactor well exhaust pipe in such a way as to connect parts of the reactor well exhaust pipe together in a detachable manner. 9. The nuclear power plant according to claim 1, whereinthe suction pipe has an operation floor area upper opening to take in gas in an upper portion of the operation floor area. 10. The nuclear power plant according to claim 1, further comprising:a penetrating pipe that passes through the containment vessel and the reactor building;two penetrating pipe isolation valves that are provided on the penetrating pipe and outside the containment vessel and inside the reactor building in such a way as to be connected to each other in series; anda leakage control pipe that branches from the penetrating pipe and between the two penetrating pipe isolation valves and is connected to the suction pipe. 11. The nuclear power plant according to claim 10, further comprisinga leakage control fan that is provided on the leakage control pipe to promote a flow of gas from a side of the penetrating pipe to a side of the suction pipe. 12. The nuclear power plant according to claim 1, further comprisinga alternate power source that supplies electric power to the standby gas treatment system in the event of a predetermined accident.