CROSS-REFERENCE TO RELATED APPLICATION

This application is the National Stage filing under 35 U.S.C. 371 of International Application No. PCT/KR2018/010118, filed on Aug. 31, 2018, which claims the benefit of earlier filing date and right of priority to Korean Application No. 10-2018-0001370, filed on Jan. 4, 2018, the contents of which are all hereby incorporated by reference herein in their entirety.

BACKGROUND

1. Technical Field

The present disclosure relates to a safety injection device for securing stability of a nuclear power plant, and particularly, to a safety injection device for injecting safety injection water in the event of a nuclear accident.

2. Description of the Related Art

A nuclear reactor is divided into a loop type reactor (e.g., commercial reactor: Korea) in which major equipment (steam generator, pressurizer, pump, etc.) is installed outside a reactor vessel and an integral reactor (e.g., SMART reactor: Korea) in which major equipment is installed inside a reactor vessel depending on an installation position.

Also, a nuclear reactor is divided into an active reactor and a passive reactor depending on an implementation scheme of a safety system. An active reactor is a reactor which uses an active device such as a pump operated by electric power of an emergency generator, or the like, to drive a safety system. A passive reactor is a reactor which uses a passive device operated by passive power such as gravity or gas pressure to drive a safety system. In a passive reactor, a passive safety system is a system which safely maintains a reactor even only with natural force installed in the system without an operator action or AC power of a safety class such as a diesel generator for more than a time (72 hours) required in regulatory requirements in an accident, and after 72 hours, the safety system may receive help of the operator action or a non-safety system.

Producing thermal output from a reactor is similar to a boiler. Heat produced by nuclear fission in a core of a pressurized water reactor is transferred to a reactor coolant (water) and the reactor coolant is forcibly circulated by a reactor coolant pump and supplied to a primary flow path of a steam generator. The reactor coolant increases a temperature of feedwater supplied to the secondary flow path of the steam generator through non-contact heat transfer to produce steam, and the produced steam drives a turbine to produce electricity, and the reactor coolant is supplied again to the core and recirculates.

Meanwhile, even when the reactor core is stopped, residual heat is generated in the core for a considerable period of time, and thus, the residual heat must be removed to keep the core safely. The residual heat of the reactor core has a characteristic of decreasing with time after the reactor core is stopped.

In detail, a control rod is inserted to suppress reactivity of the reactor core in the event of an accident, and borated water may be injected to additionally suppress the reactivity. Also, in order to keep the core safe, a coolant must be appropriately supplied so that the core may not be exposed to the outside of a water level. The borated water (cooling water) injection function is performed by a safety injection system.

The safety injection system may supply safety injection water (borated water) to a reactor in various manners in case of a nuclear accident. In a conventional loop type pressurized light water reactor, which is commonly used internationally, a large pipe may be damaged to cause a large break loss of coolant accident (LBLOCA) that a large amount of reactor coolant is discharged. In case of a large break loss of coolant accident of the commercial loop type pressurized light water reactor, a nitrogen-pressurized safety injection tank (or accumulator) is used to rapidly supply safety injection water (borated water) to the reactor. In addition, a low pressure safety injection pump and a high pressure safety injection pump are used. In another example, in a passive loop type pressurized reactor such as AP600, AP1000, or the like, developed by Westinghouse USA, a core makeup tank (CMT) which injects the safety injection water (borated water) using a gravity water head after pressure between the reactor and the tank is balanced under a high pressure condition is used in addition to the nitrogen-pressurized safety injection tank, and a refueling cavity (or in-containment refueling water storage tank (IRWST)) in a containment injected by gravity after the reactor is depressurized is used.

Meanwhile, unlike the loop type reactor, the integral reactor is formed to include a steam generator, a pressurizer, and a reactor coolant pump inside a reactor vessel, so that a large pipe may be excluded. Therefore, a large break loss of coolant accident is excluded in the integral reactor, and since many reactor coolants are retained in the reactor vessel, even when the loss of coolant accident (pipe damage) occurs, a pressure and water level of the reactor are slowly reduced, as compared with the loop type reactor.

Therefore, SMART (Korea development) implements a safety injection system by applying the core makeup tank and pressure balance type safety injection tank. The core makeup tank is in standby in a state in which a pressure balance line is open and pressure between the reactor and the tank is balanced. The pressure balance type safety injection tank is designed to have pressure lower than the core makeup tank and the both tanks are configured to inject the safety injection water (borated water) using gravity water head after the pressure balance valve is opened and pressure between the reactor and the tank is balanced in the event of an accident. Low-enriched borated water (about 4000 ppm or more) is stored in the core makeup tank and the safety injection tank.

A passive nuclear power plant has characteristics of using gravity in case of an accident. However, when a large water tank such as an in-containment refueling water storage tank is installed in a position higher than a reactor vessel, a load applied to a containment building is increased due to the water tank, and since the in-containment refueling water storage tank is installed in space for maintenance, a work space inside the containment building is narrowed, degrading economical efficiency of the nuclear power plant due to an increase in size of the containment building to additionally secure an adequate maintenance space.

Therefore, the present invention provides a safety injection device capable of supplying a coolant stored in the in-containment refueling water storage tank capable of accommodating a large amount of coolant without a limitation in location where the in-containment refueling water storage tank, as a safety injection water to the inside of a nuclear reactor for a long time, in case of an accident and a nuclear power plant having the safety injection device.

SUMMARY

Therefore, an object of the present invention is to provide a safety injection device with improved safety, which is capable of continuously supply safety injection water to cool a core inside a reactor coolant system in the event of an accident in which a nuclear reactor coolant leaks from a nuclear power plant.

Another object of the present invention is to propose a safety injection device which may operate for a long time in the event of an accident in which a reactor coolant leaks from a nuclear power plant even when a passive safety injection system is installed in the nuclear power plant.

Another object of the present invention is to propose a nuclear power plant which may secure a maintenance space inside a containment building by efficiently constructing a space inside the containment building and which may improve economical efficiency of power plant construction by preventing an increase in size of a containment building.

To achieve these and other advantages and in accordance with the purpose of this specification, as embodied and broadly described herein, a safety injection device includes: a containment building; a reactor coolant system provided inside the containment building and accommodating a reactor coolant formed to carry heat energy generated according to fission of fuel; a cooling water storage section accommodating cooling water injected into the reactor coolant system; a power producing section producing power with steam discharged from the reactor coolant system in case of an accident; a steam supply pipe transmitting steam discharged from the reactor coolant system to the power producing section; a steam discharge pipe discharging steam drove the power producing section; and a safety injection line supplying cooling water accommodated in the cooling water storage section to the inside of the reactor coolant system. In addition, cooling water accommodated in the cooling water storage section is supplied to the inside of the reactor coolant system on the basis of driving power produced by the power producing section through a cooling water inlet pipe connecting the cooling water storage section and the power producing section, a cooling water discharge pipe connecting the power producing section and the safety injection line, and the safety injection line.

In an embodiment, an integral reactor including a steam generator, a pressurizer, and a reactor coolant pump may be provided inside the reactor coolant system.

In an embodiment, the cooling water storage section may be provided at a position lower than the reactor coolant system.

In an embodiment, the power producing section may include a turbine and a pump.

In an embodiment, the turbine and the pump may be driven by the same shaft.

In an embodiment, the turbine and the pump may be driven by different shafts, and the turbine may further include a power transmission device to transmit rotational power to the pump.

In an embodiment, the turbine may further include a magnetic unit to transmit rotational power to the pump.

In an embodiment, the turbine may be an axial flow type turbine, a diagonal flow type turbine, a centrifugal turbine, a rotary type turbine or a mixed type turbine.

In an embodiment, the pump may be an axial flow type pump, a diagonal flow type pump, a centrifugal pump, a rotary type pump or a mixed type pump.

In an embodiment, the power producing section includes a jet pump.

In an embodiment, the steam supply pipe may supply steam discharged from the reactor coolant system to the power producing section.

In an embodiment, the steam supply pipe may supply steam discharged from the steam generator inside the reactor coolant system to the power producing section.

In an embodiment, a connection pipe may be provided to supply cooling water accommodated in the cooling water storage section to the steam generator.

In an embodiment, steam discharged through the steam discharge pipe may discharge into cooling water accommodated in the cooling water storage section.

In an embodiment, a sparger may be further provided at the end of the steam discharge pipe.

In an embodiment, the safety injection device may further include: a safety injection section accommodating cooling water between the power producing section and the safety injection line.

In an embodiment, the safety injection section may receive cooling water from the cooling water storage section on the basis of driving power produced by the power producing section.

In an embodiment, the safety injection section may be a gas pressured-driven type tank or a gravity-driven type tank.

In an embodiment, the safety injection section may be opened in space inside the containment building.

In an embodiment, the safety injection section may further include a pressure balance line.

In an embodiment, the safety injection device may further include a makeup tank connected to the power producing section and supplementing cooling water.

In another aspect, a nuclear power plant including the safety injection device may be provided.

According to the safety injection device of the present invention, when an accident occurs in which a reactor coolant leaks from a nuclear power plant, cooling water stored in the cooling water storage section is continuously supplied as safety injection water to the reactor coolant system by a driving force generated by steam emitted from the reactor coolant system in the power producing section, and thus, safety of the nuclear power plant may be improved.

In addition, since the safety injection device according to the present invention further includes a makeup tank connected to the power producing section to supplement cooling water, the passive safety injection system may be operated for a long time when an accident occurs in which the reactor coolant leaks.

In addition, the cooling water storage section of the safety injection device according to the present invention is disposed at a position lower than the reactor coolant system to reduce a load applied to the containment building due to the cooling water storage section, and since the space inside the containment building is effectively constructed to secure a space for maintenance to prevent an increase in size of the containment building, economical efficiency of nuclear power plant may be improved.

