Passive safety systems cool reactors using surrounding ground as a heat sink. A coolant flow channel may loop around the reactor and then pass outside, potentially through a containment building, into surrounding ground. No active components need be used in example embodiment safety systems, which may be driven entirely by gravity-based natural circulation. The coolant loop may be air-tight and seismically-hardened and filled with any coolant such as water, air, nitrogen, a noble gas, a refrigerant, etc. The ground may include a soil of grey limestone, soft grey fine sandy clay, grey slightly silty sandy gravel, etc. or any other fill with desired heat-transfer characteristics. Coolant fins and/or jackets with secondary coolants may be used on the coolant loop. The coolant loop may be buried at any constant or variable depth, and the reactor and containment may also be buried in the ground.

A generator is installed on and provides electrical power from a turbine by converting the turbine's mechanical energy to electricity. The generated electrical power is used to power controls of the turbine so that the turbine can remain in use through its own energy. The turbine can be a safety-related turbine in a nuclear power plant, such that, through the generator, loss of plant power will not result in loss of use of the turbine and safety-related functions powered by the same. Appropriate circuitry and electrical connections condition the generator to work in tandem with any other power sources present, while providing electrical power with properties required to safely power the controls.

A passive safety system comprises a heat exchanger, a thermoelectric element, and a fan unit. The heat exchanger is located inside a containment. The heat exchanger allows for temperature of atmosphere in the containment to be reduced. The thermoelectric element is disposed within the heat exchanger. The thermoelectric element is configured to generate electricity due to a temperature difference. The fan unit receives electricity generated by the thermoelectric element. The fan unit is configured to increase flow rate of fluid inside the containment. A nuclear power plant can include the passive safety system.

A nuclear reactor includes a nuclear reactor core comprising fissile material disposed in a reactor pressure vessel having vessel penetrations that exclusively carry flow into the nuclear reactor and at least one vessel penetration that carries flow out of the nuclear reactor. An integral isolation valve (IIV) system includes passive IIVs each comprising a check valve built into a forged flange and not including an actuator, and one or more active IIVs each comprising an active valve built into a forged flange and including an actuator. Each vessel penetration exclusively carrying flow into the nuclear reactor is protected by a passive IIV whose forged flange is directly connected to the vessel penetration. Each vessel penetration carrying flow out of the nuclear reactor is protected by an active IIV whose forged flange is directly connected to the vessel penetration. Each active valve may be a normally closed valve.

A passive containment heat removal system and a control method thereof are provided. The system includes an outer containment an inner containment disposed in the outer containment, an air duct formed between the inner containment and the outer containment having an air inlet and an air outlet; a spraying assembly disposed outside the inner containment and configured to passively spray cooling water to an outer wall of the inner containment to cool the inner containment; a built-in heat exchanger disposed in the inner containment; an air cooling channel having an air inlet of the air cooling channel and an air outlet of the air cooling channel; an external air cooler disposed in the air cooling channel with an inlet connected with an outlet of the built-in heat exchanger via a first communicating pipe and an outlet connected with an inlet of the built-in heat exchanger via a second communicating pipe.

Disclosed is a reactor thermal management system. A molten salt reactor vessel and a second component (e.g., a drain tank) fluidly coupled with the molten salt reactor vessel are configured to receive a flow of a molten salt therewith. The reactor thermal management system includes an internal shield or vessel encompassing the molten salt reactor vessel and the second component, the internal shield or vessel defining a first thermally insulative region therein. The internal shield or vessel is configured to maintain the first thermally insulated region above a melting temperature of the molten salt during operation of the molten salt reactor vessel.

Acquiring sets of test data on amounts of foreign matter passed through a recirculation sump screen when different amounts of foreign matter are input; forming a passed foreign matter amount approximate line that approximates the amounts of passed foreign matter with respect to the amounts of input foreign matter on the basis of the sets of test data on the amounts of passed foreign matter; forming a passed foreign matter amount envelope tangent to the passed foreign matter amount approximate line; and estimating a total passed foreign matter amount with respect to the amounts of input foreign matter on the basis of the passed foreign matter amount envelope to evaluate the recirculation sump screen are provided.

The present invention relates to a nuclear power plant having improved cooling performance and a method for operating the same. The nuclear power plant having improved cooling performance according to the present invention comprises: a reactor vessel including a reactor core; a hot-leg and a cold-leg extending from the reactor vessel; a hybrid safety injection tank which contains coolant, is connected to the cold-leg and the reactor vessel, and is positioned higher than the reactor core; a coolant tank connected to the reactor vessel and positioned higher than the reactor core; and a pressure reducing valve connected to the hot-leg.

To more reliably supply cooling water to a reactor pressure vessel and a reactor containment vessel using a back-up building if a severe accident should occur, a boiling water type nuclear power plant includes a nuclear reactor building including a reactor containment vessel, and an external building, which is installed independently outside the nuclear reactor building and which has an anti-hazard property. The external building has a power source and an operating panel independent of the nuclear reactor building. The boiling water type nuclear power plant includes a water injection pump installed inside the external building, an alternative water injection pipe performing water injection at least on a reactor pressure vessel or the reactor containment vessel in the nuclear reactor building from the water injection pump, and a valve connected to the alternative water injection pipe, making it possible to perform alternative water injection if a severe accident occurs.

A method and system for external alternate suppression pool cooling for a Boiling Water Nuclear Reactor (BWR) that does not breach the Mark I primary containment. The external cooling system may include a heat sink fluidly coupled to cooling coils surrounding the suppression pool. Cool water may be pumped through the cooling coils without the need for normal plant electrical power, which is ideal during a plant emergency. The cooling system may also be operated and controlled from a remote location to protect the safety of plant personnel.