KR20220123907A - Passive auxiliary feedwater supply system of nuclear power plant using overcooling prevention apparatus - Google Patents

Abstract

The present invention relates to a passive auxiliary water supply system of a nuclear power plant using a supercooling prevention device. The passive auxiliary water supply system includes: a steam generator for generating steam; a main engine for supplying steam from the steam generator to the turbine side; a heat exchanger for condensing the steam while exchanging heat with cooling water from the steam passing through the turbine; a main water supply pipe for recovering water condensed in the heat exchanger to the steam generator; a steam supply pipe branching from the chief complaint engine; a passive condensation tank connected to the steam supply pipe and capable of condensing steam into water through heat exchange of a condenser; a water supply pipe connecting the passive condensation tank and the main water supply pipe and moving the water condensed in the passive condensation tank to the main water supply pipe; and an auxiliary water supply start valve capable of opening and closing the water supply pipe. The auxiliary water supply start valve may include a low flow start valve and a high flow start valve. The supercooling can be prevented.

Description

Passive auxiliary feedwater supply system of nuclear power plant using overcooling prevention apparatus

The present invention relates to a passive auxiliary water supply system system of a nuclear power plant using an overcooling prevention device, and more particularly, the auxiliary water supply starting valve is separated into a low flow rate starting valve and a high flow rate starting valve. It relates to a passive auxiliary water supply system of a nuclear power plant using an overcooling prevention device that can prevent the reactor coolant system from being overcooled by excessive supply of low temperature feedwater to a steam generator.

The auxiliary water supply system of a nuclear power plant serves to cool the reactor coolant system to a safe stop state after the reactor is stopped when the main water supply system is not available in the event of an accident.

The auxiliary water supply system of a conventional nuclear power plant used an active type. However, in order to prevent operator error and malfunction of the pump that may be caused by the active type, the design of the passive type is recently changed.

The passive auxiliary water supply system does not have a separate active means such as a pump, but condenses the steam generated from the steam generator by the natural convection method in the condenser and then returns it to the steam generator to cool the reactor. There is an advantage in that it can prevent overheating of the nuclear reactor without taking any action.

However, such a passive auxiliary water supply system has the following problems. During normal operation of a nuclear power plant, the passive auxiliary water supply system maintains the auxiliary water start valve closed, so the water condensed between the heat exchanger and the valve is exposed to the atmosphere.

As the condensed water is exposed to the atmosphere, the temperature is relatively low, and since the length of the pipe is long, high flow rate of water can be supplied to the steam generator at once. If low-temperature, high-flow water supply is supplied to the steam generator at once at the beginning of opening the auxiliary water supply start valve of the passive auxiliary water supply system, overcooling may occur in the reactor coolant system, which causes unnecessary safety injection.

The present invention is to solve the above problems, and more specifically, as the auxiliary water supply starting valve is separated into a low flow rate starting valve and a high flow rate starting valve, low temperature water supply is excessive to the steam generator at the initial stage of opening of the auxiliary water supply starting valve. It relates to a passive auxiliary water supply system system of a nuclear power plant using a supercooling prevention device that can be supplied to prevent overcooling of the reactor coolant system.

A passive auxiliary water supply system system of a nuclear power plant using the overcooling prevention device of the present invention for solving the above-described problems includes: a steam generator for generating steam; a chief complaint engine for supplying the steam of the steam generator to the turbine side; a heat exchanger condensing the steam while exchanging the steam passing through the turbine with cooling water; a main water supply pipe for recovering water condensed in the heat exchanger to the steam generator; a steam supply pipe branching from the chief complaint engine; a passive condensation tank connected to the steam supply pipe and capable of condensing steam into water through heat exchange of a condenser; a water supply pipe connecting the passive condensing tank and the main water supply pipe and moving the water condensed in the passive condensing tank to the main water supply pipe; and an auxiliary water supply starting valve capable of opening and closing the water supply pipe, wherein the auxiliary water supply starting valve includes a low flow rate starting valve and a high flow rate starting valve.

The low-flow starting valve of the passive auxiliary water supply system of a nuclear power plant using the overcooling prevention device of the present invention for solving the above-described problems is installed closer to the main water supply pipe than the high-flow starting valve, and the low flow starting valve After is opened, the high flow start valve may be opened.

The capacity at which the flow rate is stored between the low flow rate starting valve and the high flow rate starting valve of the passive auxiliary water supply system of a nuclear power plant using the overcooling prevention device of the present invention for solving the above problems is the high flow rate starting valve And the flow rate between the passive condensation tank may be 20 to 30% of the storage capacity.

The low-flow starting valve and the high-flow starting valve of the passive auxiliary water supply system of a nuclear power plant using the overcooling prevention device of the present invention for solving the above problems are installed in parallel, and after the low-flow starting valve is opened , the high flow starting valve may be opened.

The flow coefficient (Cv) value of the low-flow starting valve of the passive auxiliary water supply system of a nuclear power plant using the overcooling prevention device of the present invention for solving the above-mentioned problems is the flow coefficient of the high-flow starting valve (Cv: Flow Coefficient) may be 20 to 30% of the value.

The passive auxiliary water supply system system of a nuclear power plant using the overcooling prevention device of the present invention for solving the above problems further comprises a time delay unit for controlling the opening and closing of the high flow rate starting valve and the low flow rate starting valve, the time The delay unit may open the high flow rate starting valve after a specified time after opening the low flow rate starting valve.

The passive auxiliary water supply system system of a nuclear power plant using the overcooling prevention device of the present invention for solving the above-described problems includes a water level sensor for detecting the water level of the steam generator, and the water level of the steam generator sensed by the water level sensor and a water level comparator for transmitting an operation signal to the low flow rate start valve by comparing the water level with a predetermined level.

The water supply pipe of the passive auxiliary water supply system of a nuclear power plant using the overcooling prevention device of the present invention for solving the above-described problems may be provided with a backflow prevention unit capable of preventing the backflow of condensed water.

The present invention relates to a passive auxiliary water supply system system of a nuclear power plant using an overcooling prevention device, wherein the auxiliary water supply start valve is separated into a low flow rate start valve and a high flow rate start valve, and the time delay after opening the low flow rate start valve As the high-flow start valve is opened after a specified time through the section, there is an advantage in that it can prevent the reactor coolant system from being overcooled by excessive supply of low-temperature feed water to the steam generator at the initial stage of opening of the auxiliary feed water start valve.

The present invention can prevent unnecessary safety injection by preventing the reactor coolant system from being overcooled, thereby maintaining the device integrity of the reactor coolant system.

1 is a view showing a method for preventing overcooling of an active auxiliary water supply system.
2 is a diagram illustrating movement of steam and condensed water during normal operation of a nuclear reactor according to an embodiment of the present invention.
3 is a view showing the movement of steam and condensed water when the operation of a nuclear reactor is stopped according to an embodiment of the present invention.
4 is a view showing that a low flow rate start valve and a high flow rate start valve are arranged in parallel according to another embodiment of the present invention.
5 is a view showing that the high flow rate start valve is opened after a specified time after the low flow rate start valve is opened through the time delay unit according to an embodiment of the present invention.

This specification clarifies the scope of the present invention, explains the principles of the present invention, and discloses embodiments so that those of ordinary skill in the art to which the present invention pertains can practice the present invention. The disclosed embodiments may be implemented in various forms.

Expressions such as “comprises” or “may include” that may be used in various embodiments of the present invention indicate the existence of a corresponding disclosed function, operation, or component, and may include one or more additional functions, operations, or components, etc. are not limited. In addition, in various embodiments of the present invention, terms such as "comprise" or "have" are intended to designate that a feature, number, step, action, component, part, or combination thereof described in the specification is present, It should be understood that it does not preclude the possibility of addition or existence of one or more other features or numbers, steps, operations, components, parts, or combinations thereof.

When a component is referred to as being “connected to and coupled to” another component, the component may be directly connected or coupled to the other component, but between the component and the other component. It should be understood that there may be other new components in the On the other hand, when it is said that an element is "directly connected" or "directly coupled" to another element, it will be understood that no new element exists between the element and the other element. should be able to

The terms first, second, etc. used herein may be used to describe various elements, but the elements should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another.

The present invention relates to a passive auxiliary water supply system system of a nuclear power plant using an overcooling prevention device. By separating the auxiliary water supply start valve into a low flow rate start valve and a high flow rate start valve, low-temperature water is supplied at the initial stage of opening of the auxiliary water start valve. It relates to a passive auxiliary water supply system of a nuclear power plant using an overcooling prevention device that can prevent the reactor coolant system from being overcooled by excessive supply to the steam generator. Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 shows an active auxiliary water supply system. Referring to FIG. 1 , the active auxiliary water supply system detects the water level of the steam generator by the water level sensing unit 10 , and generates an auxiliary water supply operation signal by the power plant protection system when the water level is reached through the water level comparison unit 20 . make it

Specifically, the water level sensing unit 10 detects the water level of the steam generator, and the water level comparator 20 compares the low-low water level setting value (about 25%) of the steam generator and when it is lower than the set value, the auxiliary water supply control valve ( 30) to transmit an operation signal. When an operation signal is generated from the steam generator water level comparator 20, the auxiliary water supply control valve operating unit controls the auxiliary water supply control valve 30 to control the water level of the steam generator to about 30%.

The high level comparator 40 receives the steam generator water level signal from the water level detection unit 10, and generates an operation signal when the water level of the steam generator is higher than the specified water level (about 40% or more) through the auxiliary water supply isolation valve operating unit. The auxiliary water supply isolation valve 50 is closed.

In this way, the active auxiliary water supply system can prevent overcooling from occurring in the steam generator, but in the passive auxiliary water supply system, the low-temperature water supply is excessively supplied to the steam generator at the beginning of the auxiliary water supply start valve opening, causing the reactor coolant system to malfunction. There is a problem in that it is difficult to prevent overcooling.

The passive auxiliary water supply system of a nuclear power plant using the overcooling prevention device according to an embodiment of the present invention was created to solve this problem, and the steam generator 110, the chief complaint engine 120, the heat exchanger 122, and the main water supply pipe 130 , a steam supply pipe 140 , a passive condensation tank 150 , a water supply pipe 160 , and an auxiliary water supply start valve 170 .

The steam generator 110 generates steam by the heat of the nuclear reactor, and the steam generated in the steam generator 110 may be supplied to the turbine 121 . The chief complaint engine 120 may be a pipe for supplying the steam of the steam generator 110 to the turbine 121, and the steam of the steam generator 110 passes through the chief complaint engine 120 to the turbine 121. is moved

The heat exchanger 122 condenses the steam while exchanging the steam passing through the turbine 121 with cooling water. Water condensed in the heat exchanger 122 may be recovered to the steam generator 110 through the main water supply pipe 130 .

Referring to FIG. 2 , during normal operation of the nuclear reactor, the steam generated in the steam generator 110 and the water condensed in the heat exchanger 122 are the steam generator 110 - the chief complaint engine 120 - the turbine. (121)-the heat exchanger 122-the main water supply pipe 130-the steam generator 110 moves in the order.

However, when the reactor operation is stopped, the steam supply from the chief complaint engine 120 to the turbine 121 may be blocked.

The steam supply pipe 140 is a pipe branching from the chief complaint engine 120 , and the steam generated from the steam generator 110 is supplied to the passive condensation tank 150 through the steam supply pipe 140 .

The passive condensation tank 150 is connected to the steam supply pipe 140, and can condense steam into water through heat exchange of the condenser. The water condensed in the passive condensing tank 150 is returned to the steam generator 110 while being merged into the main water supply pipe 130 through the auxiliary water supply start valve 170 and the water supply pipe 160 .

The water supply pipe 160 is a pipe connecting the passive condensation tank 150 and the main water supply pipe 130, and the water condensed in the passive condensation tank through the water supply pipe 160 is the main water supply pipe 130. is moved to

The auxiliary water supply starting valve 170 is provided to move water to the water supply pipe 160, and as the auxiliary water supply starting valve 170 is opened and closed, water can be moved to the water supply pipe 160. have. As the auxiliary water supply start valve 170 is opened and closed, the water condensed in the passive condensation tank 150 may pass through the water supply pipe 160 and move to the main water supply pipe 130 .

More specifically, as shown in FIG. 2 , during normal operation of the reactor, the auxiliary water supply start valve 170 is closed, the reactor operation is stopped as shown in FIG. 3 , and the water level of the steam generator 110 is set at the auxiliary water supply set value (about 25 %) or less, the auxiliary water supply start valve 170 is opened, and the water condensed in the passive condensation tank 150 is supplied to the main water supply pipe 130 through the water supply pipe 160 . The condensed water supplied to the main water supply pipe 130 is recovered to the steam generator 110 .

As described above, the passive auxiliary water supply system according to the embodiment of the present invention does not include a separate active means such as a pump and converts the steam generated in the steam generator 110 by a natural convection method into the passive condensation tank 150. After being condensed in the condenser, it is recovered by the steam generator 110 to cool the nuclear reactor, thereby preventing overheating of the nuclear reactor without action by the power source and the operator in the event of an accident in the nuclear power plant.

However, since the auxiliary water supply starting valve 170 is maintained in a closed state during normal operation of the nuclear power plant, the water condensed between the passive condensation tank 150 and the auxiliary water supply starting valve 170 is exposed to the atmosphere, so that the temperature is relatively to be lowered to

In addition, since the length of the pipe between the passive condensation tank 150 and the auxiliary water supply starting valve 170 is long, when the auxiliary water supply starting valve 170 is opened, the main water supply pipe 130 and the steam generator ( 110) may be supplied with low-temperature, high-flow water supply.

When the low-temperature, high-flow water supply is supplied to the steam generator 110 at the initial stage of opening the auxiliary water supply start valve 170, unnecessary safety injection may occur due to supercooling of the reactor coolant system. Therefore, in order to prevent overcooling of the reactor coolant system, it is necessary to limit the initial water supply flow rate supplied from the passive auxiliary water supply system.

The passive auxiliary water supply system system of a nuclear power plant using the overcooling prevention device according to an embodiment of the present invention was created to prevent the safety injection system from operating according to the overcooling of the reactor coolant system due to an oversupply of auxiliary water supply. . (Here, the safety injection system prevents exposure of the reactor core in the event of a reactor coolant loss accident, controls the reactivity of the reactor by injection of boric acid water, and directly cools the heat generated in the reactor due to the accident.)

The passive auxiliary water supply system of a nuclear power plant using the overcooling prevention device according to an embodiment of the present invention may use a low flow rate start valve 171 and a high flow rate start valve 172 to solve this problem. Specifically, the auxiliary water supply start valve 170 may include the low flow rate start valve 171 and the high flow rate start valve 172 .

The low flow starting valve 171 is installed closer to the main water supply pipe 130 than the high flow starting valve 172, and after the low flow starting valve 171 is opened, the high flow starting valve 172 will open

Specifically, in the passive auxiliary water supply system system of a nuclear power plant using the overcooling prevention device according to an embodiment of the present invention, the time delay for controlling the opening and closing of the high flow rate start valve 172 and the low flow rate start valve 171 It further includes a unit 180, and after opening the low flow rate starting valve 171 through the time delay unit 180, it is possible to open the high flow rate starting valve 172 after a specified time.

As such, when the low flow rate starting valve 171 is opened first, the low temperature initial water supply flow rate supplied to the main water supply pipe 130 and the steam generator 110 by the auxiliary water supply starting valve 170 can be limited. there will be

That is, in the passive auxiliary water supply system system of a nuclear power plant using the overcooling prevention device according to an embodiment of the present invention, the auxiliary water supply starting valve 170 is connected to the low flow rate starting valve 171 and the high flow rate starting valve 172. It is possible to limit the initial water supply flow rate by separating two units. When the steam generator 110 reaches the low-low water level set value, the low flow rate start valve 171 is first opened, and after the delay time elapses, the The high flow start valve 172 is opened.

Through this, the passive auxiliary water supply system system of a nuclear power plant using the overcooling prevention device according to an embodiment of the present invention can prevent overcooling of the reactor coolant system.

According to an embodiment of the present invention, the capacity at which the flow rate is stored between the low flow rate starting valve 171 and the high flow rate starting valve 172 is the high flow rate starting valve 172 and the passive condensation tank 150 . The flow rate may be between 20 and 30% of the stored capacity.

When the water level of the steam generator 110 reaches the low-low water level set point, the low flow rate starting valve 171 is opened, and the flow rate stored between the low flow rate starting valve 171 and the high flow starting valve 172 is opened. This can be supplied.

That is, the flow rate stored between the low flow rate starting valve 171 and the high flow rate starting valve 172 may be the initial water supply flow rate. At this time, if the flow rate stored between the low flow rate start valve 171 and the high flow rate start valve 172 is higher than the flow rate between the high flow rate start valve 172 and the passive condensation tank 150 (more than 30%) high), and there is a problem in that it is difficult to prevent overcooling of the reactor coolant system.

Conversely, when the flow rate stored between the low flow rate start valve 171 and the high flow rate start valve 172 is lower than the flow rate between the high flow rate start valve 172 and the passive condensation tank 150 (20%) lower), the effect of watering may be negligible.

Therefore, the capacity for storing the flow rate between the low flow rate starting valve 171 and the high flow rate starting valve 172 is that the flow rate is stored between the high flow rate starting valve 172 and the driven condensation tank 150 . It is preferably 20 to 30% of the dose.

However, the present invention is not limited thereto, and the capacity for storing the flow rate between the low flow rate starting valve 171 and the high flow rate starting valve 172 and between the high flow rate starting valve 172 and the passive condensing tank 150 is not limited thereto. The storage capacity of the flow rate can be determined according to the delay time at which safety injection does not occur.

In general, the capacity of the low-flow starting valve 171 is determined according to a delay time in which safety injection does not occur within 30 minutes, which is the operator action time in case of a design-based accident, and as the delay time becomes longer, the capacity of the low-flow starting valve 171 decreases. The smaller it is, the more time the safety injection system is injected is delayed.

According to another embodiment of the present invention, the low flow rate starting valve 171 and the high flow rate starting valve 172 may be installed in parallel. Referring to FIG. 4 , while the low flow rate start valve 171 and the high flow rate start valve 172 are installed in parallel, after the low flow rate start valve 171 is opened, the high flow rate start valve 172 is may be open

Even when the low flow rate start valve 171 and the high flow rate start valve 172 are installed in parallel, after the low flow rate start valve 171 is opened through the time delay unit 180, after a specified time It is possible to open the high flow valve 172 .

As such, when the low flow rate starting valve 171 is opened first, the low temperature initial water supply flow rate supplied to the main water supply pipe 130 and the steam generator 110 by the auxiliary water supply starting valve 170 can be limited. there will be

That is, in the passive auxiliary water supply system of a nuclear power plant according to an embodiment of the present invention, the auxiliary water supply start valve 170 is separated into the low flow rate start valve 171 and the high flow rate start valve 172 in parallel. As a result, the initial water supply flow rate can be limited. When the steam generator 110 reaches the low-low water level set value, the low flow rate start valve 171 is first opened, and the high flow rate is started after the delay time has elapsed. The valve 172 is opened.

Through this, the passive auxiliary water supply system of a nuclear power plant according to an embodiment of the present invention can prevent overcooling of the reactor coolant system.

According to an embodiment of the present invention, the flow coefficient (Cv: Flow Coefficient) value of the low flow rate starting valve 171 is 20 to 30 of the flow coefficient (Cv: Flow Coefficient) value of the high flow rate starting valve 172 . % can be

When the water level of the steam generator 110 reaches a low-low water level set value, a flow rate may be supplied through the low flow rate start valve 171 , and the flow rate supplied through the low flow rate start valve 171 is initially It could be the water supply.

If the initial water supply flow rate supplied through the low flow rate start valve 171 is too high compared to the flow rate supplied through the high flow rate start valve 172, it is difficult to prevent overcooling of the reactor coolant system. Conversely, if the initial water supply flow rate supplied through the low flow rate start valve 171 is too low for the flow rate supplied through the high flow rate start valve 172, the effect of water supply may become insignificant.

Therefore, it is preferable that the flow coefficient (Cv: Flow Coefficient) value of the low flow rate starting valve 171 is 20 to 30% of the flow coefficient (Cv: Flow coefficient) value of the high flow rate starting valve 172 .

However, the present invention is not limited thereto, and the flow coefficient of the low flow rate start valve 171 and the flow rate coefficient of the high flow rate start valve 172 may be determined according to a delay time during which safety injection does not occur.

In general, the low flow rate start valve 171 flow coefficient is determined according to a delay time in which safety injection does not occur within 30 minutes, which is the operator action time in case of a design standard accident, and as the delay time increases, the low flow rate start valve 171 flow coefficient increases. The smaller it is, the more time the safety injection system is injected is delayed.

Referring to FIG. 5 , the passive auxiliary water supply system of a nuclear power plant using the overcooling prevention device according to an embodiment of the present invention may further include a water level detecting unit 191 and a water level comparing unit 192 . The water level detection unit 191 detects the water level of the steam generator 110 .

The water level comparator 192 compares the water level of the steam generator 110 sensed by the water level detection unit 191 with a predetermined water level, and transmits an operation signal to the low flow rate start valve 171 .

When the water level sensor 191 receives the water level signal of the steam generator 110 and the water level of the steam generator 110 is lower than the low-low water level setting value (about 25%), the water level comparison unit 192 ) transmits a signal to the low flow rate starting valve 171 and the time delay unit 180 .

When the signal is transmitted, the low flow rate start valve 171 is opened and the water supply flow rate is supplied to the steam generator 110 . The time delay unit 180 delays the opening of the high flow rate start valve 172 for a specified time after the low flow rate start valve 171 is opened, so that supercooling occurs in the reactor coolant system. will prevent

Specifically, when a signal is generated from the water level comparator 192, the time delay unit 180 provides a closing signal (Off signal) to the high-flow valve 172 for a predetermined time, and the predetermined delay time After elapse of time, an open signal (On signal) may be provided to open the high flow valve 172 . When a predetermined delay time elapses, the high flow rate start valve 172 starts to open, and supplies water to the steam generator 110 together with the low flow rate start valve 171 .

As described above, after the water level of the steam generator 110 reaches the low-low water level set value, the high flow rate start valve 172 is closed for a predetermined delay time, and the low flow rate start valve 171 supplies only water supply. It is possible to prevent overcooling of the system.

The water supply pipe 160 according to an embodiment of the present invention may be provided with a backflow prevention unit capable of preventing a backflow of condensed water. The backflow prevention unit prevents the condensed water from flowing backward without being supplied to the main water supply pipe 130 .

The passive auxiliary water supply system of a nuclear power plant using the overcooling prevention device according to the embodiment of the present invention described above has the following effects.

The passive auxiliary water supply system system of a nuclear power plant using the overcooling prevention device according to an embodiment of the present invention separates the auxiliary water supply start valve into a low flow rate start valve and a high flow rate start valve, and after opening the low flow rate start valve, time As the high-flow start valve is opened after a specified time through the delay unit, there is an advantage in that it can prevent the reactor coolant system from being overcooled by excessive supply of low-temperature feed water to the steam generator at the initial stage of opening of the auxiliary feed water start valve.

The passive auxiliary water supply system of a nuclear power plant using the overcooling prevention device according to an embodiment of the present invention prevents the reactor coolant system from being overcooled, thereby preventing unnecessary safety injection, and through this, the reactor coolant system equipment It has the advantage of maintaining soundness.

As described above, the present invention has been described with reference to one embodiment shown in the drawings, but it will be understood that this is merely exemplary and that various modifications and variations of embodiments are possible therefrom by those skilled in the art. . Therefore, the true technical protection scope of the present invention should be determined by the technical spirit of the appended claims.

110...steam generator 120...main complaint organ
121...Turbine 122...Heat exchanger
130...Main water supply line 140...Steam supply line
150...Passive condensing tank 160...Water supply pipe
170...Auxiliary water start valve 171...Low flow start valve
172...High flow start valve 180...Time delay part
191...water level detection unit 192...water level comparison unit

Claims (8)

In the passive auxiliary water supply system system of a nuclear power plant using an overcooling prevention device,
a steam generator for generating steam;
a chief complaint engine for supplying the steam of the steam generator to the turbine side;
a heat exchanger condensing the steam while exchanging the steam passing through the turbine with cooling water;
a main water supply pipe for recovering water condensed in the heat exchanger to the steam generator;
a steam supply pipe branching from the chief complaint engine;
a passive condensation tank connected to the steam supply pipe and capable of condensing steam into water through heat exchange of a condenser;
a water supply pipe connecting the passive condensing tank and the main water supply pipe and moving the water condensed in the passive condensing tank to the main water supply pipe;
It includes; an auxiliary water supply start valve capable of opening and closing the water supply pipe;
The auxiliary water supply starting valve is a passive type auxiliary water supply system of a nuclear power plant using an overcooling prevention device, characterized in that it includes a low flow rate starting valve and a high flow rate starting valve. The method of claim 1,
The low-flow starting valve is installed closer to the main water supply pipe than the high-flow starting valve,
A passive auxiliary water supply system of a nuclear power plant using an overcooling prevention device, characterized in that after the low flow rate start valve is opened, the high flow rate start valve is opened. 3. The method of claim 2,
The capacity in which the flow rate is stored between the low flow rate starting valve and the high flow rate starting valve is,
A passive auxiliary water supply system of a nuclear power plant using an overcooling prevention device, characterized in that 20 to 30% of the storage capacity between the high flow rate starting valve and the passive condensing tank. The method of claim 1,
The low flow starting valve and the high flow starting valve are installed in parallel,
A passive auxiliary water supply system of a nuclear power plant using an overcooling prevention device, characterized in that after the low flow rate start valve is opened, the high flow rate start valve is opened. 5. The method of claim 4,
A nuclear power plant using an overcooling prevention device, characterized in that the flow coefficient (Cv) value of the low flow valve is 20 to 30% of the flow coefficient (Cv) value of the high flow valve. of passive auxiliary water supply system. 5. The method of claim 2 or 4,
Further comprising a time delay unit for controlling the opening and closing of the high flow rate starting valve and the low flow rate starting valve,
The time delay unit, after opening the low flow rate starting valve, a passive type auxiliary water supply system of a nuclear power plant using an overcooling prevention device, characterized in that it opens the high flow rate starting valve after a specified time. 5. The method of claim 2 or 4,
a water level sensing unit for detecting the water level of the steam generator;
The passive type of a nuclear power plant using an overcooling prevention device, characterized in that it includes a water level comparison unit that compares the water level of the steam generator sensed by the water level detection unit with a predetermined water level, and transmits an operation signal to the low flow rate start valve. Auxiliary water supply system. The method of claim 1,
A passive auxiliary water supply system of a nuclear power plant using an overcooling prevention device, characterized in that the water supply pipe is provided with a backflow prevention unit capable of preventing the backflow of condensed water.

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