Cooling water discharge device and method of operating a cooling water discharge device

Abstract

To enable appropriate discharge of cooling water from a branch pipe when a water discharge pipe is clogged while preventing unintended outflow of the cooling water.SOLUTION: A cooling water discharge device is provided, comprising a discharge pipe for discharging cooling water after cooling constituent equipment of a nuclear power plant, and a branch pipe branching from the discharge pipe. The branch pipe is provided with a rupture disc. A first orifice is provided in the discharge pipe on a side downstream of a branch point to the branch pipe.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] TECHNICAL FIELD The present disclosure relates to a cooling water discharge device and a method of operating a cooling water discharge device. [Background technology]

[0002] In nuclear power plants, cooling water such as seawater is used to cool components such as reactors, which emit large amounts of heat. The cooling water used to cool the components receives heat from the components, increasing its temperature, and is then discharged into a water discharge pit through a designated water discharge pipe. As such, the water discharge pipe has the function of discharging the cooling water, which contains the heat from the components, and is therefore important for maintaining cooling performance.

[0003] Meanwhile, nuclear power plants are required to maintain cooling performance even in emergencies, such as natural disasters such as earthquakes. Patent Document 1 discloses a technology that enables the cooling system to maintain its function by providing a branch pipe to a discharge pipe that normally discharges cooling water, so that cooling water can be discharged through the branch pipe even if the discharge pipe is clogged in an emergency. In this document, the branch pipe that functions in an emergency is positioned higher than the discharge pipe, preventing cooling water from flowing out of the branch pipe under normal conditions, while allowing the cooling water to be discharged to the outside from the branch pipe due to an increase in water pressure if the discharge pipe is clogged in an emergency. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 58-193492 Summary of the Invention [Problem to be solved by the invention]

[0005] When a branch pipe is added to a discharge pipe for discharging cooling water into a discharge pit as in Patent Document 1, depending on the position and shape of the added branch pipe, some of the cooling water flowing through the discharge pipe may be taken into the branch pipe, causing the cooling water to flow out of the branch pipe even under normal conditions. Conversely, air taken into the branch pipe from the outside may be released as a two-phase flow together with the cooling water in the discharge pipe.

[0006] In order to prevent cooling water from leaking from the branch pipe under normal conditions and ensure that cooling water is released from the branch pipe in an emergency, a rupture disk that can burst when a predetermined pressure is applied to the branch pipe can be considered. In this case, adjustments are required to keep the pressure acting on the rupture disk below the burst pressure under normal conditions to prevent unintended rupture of the rupture disk, and to ensure that the rupture disk can burst and release cooling water in place of a blocked discharge pipe in an emergency. It is also necessary to prevent unintended leakage of cooling water from the branch pipe when the rupture disk installed on the branch pipe is removed for maintenance.

[0007] At least one embodiment of the present disclosure has been made in consideration of the above-mentioned circumstances, and aims to provide a cooling water discharge device and a method of operating a cooling water discharge device that can accurately discharge cooling water from a branch pipe when a blockage occurs in the discharge pipe while avoiding unintended leakage of cooling water. [Means for solving the problem]

[0008] In order to solve the above problem, the cooling water discharge device according to at least one embodiment of the present disclosure includes: a discharge pipe for discharging cooling water that has cooled components of the nuclear plant; a branch pipe branching from the discharge pipe and communicating with the outside; a rupture disk provided in the branch pipe; a first orifice provided in the discharge pipe downstream of a branch point with the branch pipe; Equipped with.

[0009] In order to solve the above problem, a method for operating a cooling water discharge device according to at least one embodiment of the present disclosure includes: a discharge pipe for discharging cooling water that has cooled components of the nuclear plant; a pump for supplying the cooling water to the discharge pipe; a branch pipe branching from the discharge pipe and communicating with the outside; a rupture disk provided in the branch pipe; a first orifice provided in the discharge pipe downstream of a branch point with the branch pipe; A vent valve is provided in the branch pipe upstream of the rupture disk and capable of switching a communication state between the branch pipe and the outside; A method of operating a cooling water discharge device, comprising: opening the vent valve while the liquid level of the cooling water in the branch pipe is rising after the pump is started; closing the vent valve when the rise in the liquid level in the branch pipe stops; Equipped with. [Effects of the Invention]

[0010] According to at least one embodiment of the present disclosure, a cooling water discharge device and a method for operating a cooling water discharge device can be provided that can accurately discharge cooling water from a branch pipe when a blockage occurs in the discharge pipe while avoiding unintended leakage of cooling water. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic configuration diagram of a cooling system of a nuclear power plant according to an embodiment; [Figure 2] FIG. 2 is a schematic diagram showing the general configuration of the cooling water discharge device of FIG. [Figure 3] 3 is a comparative example of the cooling water discharge device shown in FIG. 2. [Figure 4] FIG. 2 is a schematic diagram showing the state when the rupture disk bursts. [Figure 5] 4 is a flowchart illustrating a method of operating a cooling water discharge device according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, several embodiments of the present invention will be described with reference to the accompanying drawings. However, the configurations described as the embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present invention.

[0013] FIG. 1 is a schematic diagram of a cooling system 1 of a nuclear power plant according to one embodiment, and FIG. 2 is a schematic diagram showing the schematic configuration of a cooling water discharge device 4 of FIG.

[0014] 1, a cooling system 1 of a nuclear power plant is configured to cool components (not shown) of the nuclear power plant by exchanging heat between the components and cooling water in a heat exchanger 3. The cooling system 1 includes a cooling water supply device 2 for supplying cooling water to the heat exchanger 3, and a cooling water discharge device 4 for discharging the cooling water that has completed heat exchange in the heat exchanger 3. The cooling water is, for example, seawater, but may be fresh water or pure water.

[0015] The cooling water supply device 2 takes in cooling water to be supplied to the heat exchanger 3 using a pump 6 provided at a cooling water intake source. The cooling water taken in by the pump 6 is supplied to the heat exchanger 3 via a water supply pipe 7. A strainer 10 is provided in the water supply pipe 7 to remove foreign matter and the like contained in the cooling water.

[0016] The cooling water discharge device 4 is a device for discharging the cooling water that has completed heat exchange in the heat exchanger 3 to the outside, and discharges the cooling water via a water discharge pipe 12 into a water discharge pit 16 that communicates with the water discharge port 14. The water discharge pipe 12 is a pipe member having a predetermined shape, and in this embodiment, the water discharge pipe 12 extends mainly in a substantially horizontal direction and is connected to the water discharge pit 16 on the downstream side.

[0017] 3 is a comparative example of the cooling water discharge device 4 shown in FIG. 2 (hereinafter, the cooling water discharge device according to the comparative example will be denoted by the reference symbol "4'"). The cooling water discharge device 4' according to the comparative example has a simple configuration in which the heat exchanger 3 is connected to the water discharge pit 16 via the water discharge pipe 12, so that all of the cooling water from the heat exchanger 3 is discharged into the water discharge pit 16.

[0018] The water discharge pipe 12 is provided with an orifice 18 for adjusting the flow rate of the cooling water in the water discharge pipe 12. In this embodiment, the orifices 18 are provided in four stages along the length of the water discharge pipe 12, but the number of stages and shape of the orifices 18 can be set appropriately to correspond to the set flow rate of the cooling water in the water discharge pipe 12. Furthermore, if the water discharge pipe 12 is designed so that the set flow rate of the cooling water is achieved by the shape of the water discharge pipe 12, the orifice 18 may be omitted.

[0019] In this type of cooling water discharge device 4', if a blockage C occurs in the discharge pipe 12 due to a natural disaster such as an earthquake, the supply of cooling water from the discharge pipe 12 to the discharge pit 16 will be hindered, making it impossible to discharge the cooling water to the outside. This situation may lead to a decrease or loss of cooling performance in the cooling system 1, but this can be suitably resolved by the cooling water discharge device 4 described below.

[0020] 1 and 2, in the cooling water discharge device 4 according to this embodiment, a branch pipe 20 is additionally provided to the discharge pipe 12. The branch pipe 20 branches off from the discharge pipe 12, and is configured to function as an alternative discharge path for the cooling water from the discharge pipe 12 even if a blockage C occurs in the discharge pipe 12.

[0021] The branch point 13 of the branch pipe 20 is provided downstream of the aforementioned orifice 18 (hereinafter referred to as the "second orifice 18" to distinguish it from the first orifice 24 described below) provided in the discharge pipe 12. Here, in the discharge pipe 12 to which the branch pipe 20 has been added, the flow resistance downstream of the branch point 13 is reduced by reducing the resistance of the second orifice 18 compared to the discharge pipe 12 to which the branch pipe 20 has not been added (see FIG. 3 ), so that the flow rate that normally flows through the branch pipe 20 will flow through the branch pipe 20 when a blockage C occurs in the discharge pipe 12. Therefore, if the branch pipe 20 were simply added to the comparative example shown in FIG. 3 , the flow rate to the discharge pit 16 under normal conditions (when no blockage C occurs in the discharge pipe 12) would increase. Therefore, in this embodiment, the first orifice 24 is provided downstream of the branch point 13 in the discharge pipe 12. This allows adjustment to increase the flow resistance of the discharge pipe 12 downstream of the branch point 13, and by offsetting the effect of the additional installation of the branch pipe 20, it is possible to suppress changes in the flow rate to the discharge pit 16 under normal conditions.

[0022] Incidentally, in order to suppress the change in the flow rate of the discharge pipe 12 due to the addition of such a branch pipe 20, it is also possible to reduce the pipe diameter of the discharge pipe 12 downstream of the branch point 13, but this would require relatively large-scale construction such as replacing a part of the discharge pipe 12. In contrast, in this embodiment, this is addressed by installing the first orifice 24 downstream of the branch point 13 in the discharge pipe 12, which can be achieved with smaller-scale construction.

[0023] The branch pipe 20 is composed of a pipe member having a predetermined diameter and length, and a rupture disk 26 is provided near the downstream opening 25. When pressure exceeding a threshold is applied, the rupture disk 26 bursts as shown in FIG. 4, allowing communication between the front and rear of the rupture disk 26. Under normal conditions, when no blockage C occurs in the discharge pipe 12, the pressure acting on the rupture disk 26 is below the threshold, so the downstream side of the branch pipe 20 is blocked by the rupture disk 26. On the other hand, in an emergency when blockage C occurs in the discharge pipe 12, cooling water from the discharge pipe 12 enters the branch pipe 20, increasing the pressure acting on the rupture disk 26. When the pressure acting on the rupture disk 26 reaches or exceeds the threshold, the rupture disk 26 bursts, and the cooling water from the discharge pipe 12 is discharged to the outside through the opening 25 via the branch pipe 20. In this way, even if a blockage C occurs in the discharge pipe 12, the cooling water discharge path is secured, and the cooling performance of the cooling system 1 is maintained in an appropriate manner.

[0024] A flow control valve 28 is provided in the branch pipe 20 between the branch point 13 and the rupture disk 26. The flow control valve 28 can adjust the ease with which the cooling water flows from the discharge pipe 12 into the branch pipe 20 by appropriately adjusting its opening.

[0025] The branch pipe 20 branches upward from the discharge pipe 12, which extends substantially horizontally. In this embodiment, the branch pipe 20 includes a first portion 20a that extends substantially vertically and a second portion 20b that extends substantially horizontally downstream of the first portion 20a. The flow rate adjustment valve 28 described above is provided in the first portion 20a, and the rupture disk 26 is provided in the second portion 20b. At least one of the discharge pipe 20 and the second portion 20b of the branch pipe 20 may be inclined.

[0026] The cooling water level H in the branch pipe 20 is determined by the balance between the head of the cooling water that has entered the first portion 20a and the pressure in the space V between the cooling water surface and the rupture disk 26. In this embodiment, the cooling water level H in the branch pipe 20 is adjusted to be in the first portion 20a of the branch pipe 20. If the cooling water level H in the branch pipe 20 reaches the second portion 20b, for example, when the rupture disk 26 is removed for maintenance, there is a risk of unintended cooling water outflow from the opening 25. Furthermore, if the cooling water does not enter the branch pipe 20 (i.e., if the cooling water level in the branch pipe 20 does not reach the first portion 20a), air in the branch pipe 20 will be mixed into the cooling water flowing through the discharge pipe 12 under normal conditions. Therefore, by adjusting the cooling water level H in the branch pipe 20 to be in the first portion 20a of the branch pipe 20, the cooling water discharge device 4 can be operated appropriately.

[0027] The head of the cooling water that has entered the first portion 20a is determined based on the shape (length and diameter) of the branch pipe 20, the flow rate of the cooling water in the discharge pipe 12, and the pressure in the space V. In this embodiment, since the first orifice 24 and the second orifice 18 are provided in the discharge pipe 12 as described above, the flow rate of the cooling water in the discharge pipe 12 can be adjusted by adjusting the diameters of these orifices.

[0028] A vent valve 30 is provided in the branch pipe 20 upstream of the rupture disk 26. In this embodiment, the vent valve 30 is provided in the second portion 20b of the branch pipe 20. The vent valve 30 can adjust the pressure in the space V by opening and closing the branch pipe 20 to switch the communication state between the branch pipe 20 and the outside. When the vent valve 30 is closed, the branch pipe 20 is isolated from the outside, and the space V between the cooling water surface in the branch pipe 20 and the rupture disk 26 is sealed. In this case, the pressure P in the space V is normally below the threshold value at which the rupture disk 26 ruptures. However, when a blockage C occurs in the discharge pipe 12, the cooling water level in the branch pipe 20 rises and reaches or exceeds the threshold value, causing the rupture disk 26 to rupture (at this time, the air present in the space V functions as a buffer that transmits pressure from the cooling water level to the rupture disk 26). When the vent valve 30 is opened, the space V communicates with the outside via the vent valve 30, and the space V is maintained at atmospheric pressure.

[0029] In the cooling water discharge device 4 configured as described above, the first orifice 24 is provided in the discharge pipe 12 downstream of the branch point 13 with the branch pipe 20, thereby making it possible to adjust the flow resistance in the discharge pipe 12 downstream of the branch point 13. As a result, by appropriately adjusting the water level H in the branch pipe 20 under normal conditions, it is possible to prevent unnecessary outflow of cooling water from the branch pipe 20 and the intrusion of air taken in from the branch pipe 20 into the discharge pipe 12 (see FIG. 2), while in an emergency in which a blockage C occurs, the rupture disk 26 is ruptured by the pressure increase in the branch pipe 20, thereby making it possible to reliably secure the discharge path (see FIG. 4).

[0030] The first orifice 24 provided in the discharge pipe 12 is configured so that a first flow rate R1 (see FIG. 2) of cooling water flowing through the discharge pipe 12 in normal times when the discharge pipe 12 is connected to the discharge pit 16 is approximately equal to a second flow rate R2 (see FIG. 4) of cooling water flowing through the discharge pipe 12 and the branch pipe 20 upstream of the branch point 13 when a blockage C occurs in the discharge pipe 12 downstream of the branch point 13. As a result, when a blockage C occurs in the discharge pipe 12, cooling water can be discharged from the branch pipe 20 at a flow rate approximately equal to that when no blockage C occurs in the discharge pipe 12, and cooling performance equivalent to that in normal times can be maintained even in an emergency.

[0031] Furthermore, when a second orifice 18 is provided in the water discharge pipe 12 upstream of the branch point 13, the water level H of the cooling water in the branch pipe 20 can be adjusted by balancing the first orifice 24 and the second orifice 18, thereby preventing unintended leakage of the cooling water and enabling the cooling water to be accurately released from the branch pipe 20 when a blockage C occurs in the water discharge pipe 12.

[0032] Next, a method for operating the cooling water discharge device 4 having the above configuration will be described. Fig. 5 is a flowchart showing a method for operating the cooling water discharge device 4 according to one embodiment. In the following description, it is assumed that the initial state is a state in which the cooling water discharge device 4 is stopped as a whole, and therefore no cooling water is present in the discharge pipe 12.

[0033] First, the user starts the pump 6 (see FIG. 1) to supply cooling water to the discharge pipe 12 (step S1). When the pump 6 is started, the cooling water supplied to the discharge pipe 12 gradually fills the discharge pipe 12, and some of the cooling water further flows into the branch pipe 20.

[0034] While the cooling water level H in the branch pipe 20 is rising, the user opens the vent valve 30 provided in the branch pipe 20 (step S2). As a result, the space V existing in the branch pipe 20 between the surface of the cooling water and the rupture disk 26 is maintained at atmospheric pressure by being connected to the outside (atmosphere) via the vent valve 30. When the pump 6 is started in this way to introduce cooling water into the discharge pipe 12, opening the vent valve 30 provided in the branch pipe 20 makes the space V in the branch pipe 20 atmospheric pressure, thereby reliably preventing unintended rupture of the rupture disk 26 provided in the branch pipe 20.

[0035] Next, the user determines whether the water level in the branch pipe 20 has stopped rising (step S3). The water level of the cooling water in the branch pipe 20 continues to rise until the water pressure of the cooling water and the atmospheric pressure are balanced. In this embodiment, as described above with reference to FIG. 2, the water level H of the cooling water is configured to rise to a position in the first portion 20a of the branch pipe 20.

[0036] When the water level in the branch pipe 20 stops rising in this way (step S3: YES), the user closes the vent valve 30 (step S4). This allows the cooling water to be maintained at a predetermined water level H in the branch pipe 20 without causing the rupture disk 26 to unintentionally burst. As a result, when the discharge pipe 12 is blocked, the water level H in the branch pipe 20 rises and the rupture disk 26 bursts, thereby securing a water discharge path.

[0037] The opening degree of the flow rate control valve 28 provided in the branch pipe 20 can be adjusted at any timing using the above-mentioned operating method (see FIG. 5). The opening degree of the flow rate control valve 28 is adjusted based on the results of calculation using the CV characteristics defined as the specifications of the flow rate control valve 28, so that the flow rate of the cooling water in the branch pipe 20 falls within a predetermined range, for example, if a blockage C occurs in the discharge pipe 12 downstream of the branch point 13, causing the cooling water flowing through the discharge pipe 12 to flow into the branch pipe 20. Such opening degree adjustment of the flow rate control valve 28 basically needs to be performed once for the cooling water discharge device 4, but may be performed multiple times as necessary, for example, when the configuration of the cooling water discharge device 4 is changed.

[0038] As described above, according to each of the above embodiments, it is possible to provide a cooling water discharge device 4 and a method of operating the cooling water discharge device 4 that can accurately discharge cooling water from the branch pipe 20 when a blockage C occurs in the discharge pipe 12 while avoiding unintended leakage of cooling water.

[0039] In addition, within the scope of the present disclosure, the components in the above-described embodiments may be replaced with well-known components as appropriate, and the above-described embodiments may be combined as appropriate.

[0040] The contents described in each of the above embodiments can be understood, for example, as follows.

[0041] (1) A cooling water discharge device (1) according to one embodiment includes: a discharge pipe (12) for discharging cooling water that has cooled components of the nuclear plant; a branch pipe (20) branching from the discharge pipe and communicating with the outside; a rupture disk (26) provided in the branch pipe; a first orifice (24) provided in the discharge pipe downstream of a branch point (13) where the discharge pipe branches off from the branch pipe; Equipped with.

[0042] According to the above aspect (1), a first orifice is provided in the discharge pipe downstream of the branch point where it branches off from the branch pipe. This allows the first orifice to adjust the flow resistance in the discharge pipe downstream of the branch point. As a result, by appropriately adjusting the water level in the branch pipe under normal conditions, it is possible to prevent unnecessary cooling water from flowing out of the branch pipe and prevent air taken in from the branch pipe from entering the discharge pipe, and in an emergency, a rupture disk is ruptured by a pressure increase in the branch pipe, thereby reliably securing a water discharge path.

[0043] (2) In another embodiment, in the above embodiment (1), The first orifice is configured so that a first flow rate (R1) of the cooling water flowing through the discharge pipe when the discharge pipe is connected to a water discharge pit is approximately equal to a second flow rate (R2) of the cooling water flowing through the discharge pipe when a blockage occurs in the discharge pipe downstream of the branch point.

[0044] According to the above aspect (2), the first orifice provided in the discharge pipe downstream of the branch point can adjust the flow rate of the cooling water in the discharge pipe when no blockage occurs in the discharge pipe, thereby making it possible to appropriately adjust the flow rate of the cooling water in the discharge pipe when no blockage occurs in the discharge pipe.

[0045] (3) In another aspect, in the above aspect (1) or (2), The discharge pipe further includes a second orifice (18) provided upstream of the branch point.

[0046] According to the above aspect (3), a second orifice is provided in the discharge pipe upstream of the branch point. The second orifice is installed in consideration of a balance with the first orifice provided in the branch pipe downstream of the branch point, thereby making it possible to accurately discharge cooling water from the branch pipe when a blockage occurs in the discharge pipe while avoiding unintended outflow of cooling water.

[0047] (4) In another embodiment, in any one of the above (1) to (3), The branch pipe further includes a flow rate adjusting valve (28) that is provided between the branch point and the rupture disk and has an adjustable opening.

[0048] According to the above aspect (4), a flow control valve is provided in the branch pipe between the branch point and the rupture disk. In this aspect, the flow resistance in the branch pipe can be varied by adjusting the opening of the flow control valve, and the flow rate of the fluid in the branch pipe can be appropriately adjusted when the discharge pipe is clogged.

[0049] (5) In another embodiment, in any one of the above (1) to (4), The branch pipe branches upward from the discharge pipe.

[0050] According to the above aspect (5), the branch pipe branches upward from the discharge pipe, whereby the level of the cooling water that has entered the branch pipe from the discharge pipe is appropriately adjusted by the flow resistance of the orifice in the discharge pipe and the water head.

[0051] (6) In another embodiment, in any one of the above (1) to (5), A vent valve (30) capable of switching a communication state between the branch pipe and the outside is provided on the branch pipe upstream of the rupture disk.

[0052] According to the above aspect (6), by providing a vent valve in the branch pipe, the pressure between the water surface of the cooling water in the branch pipe and the rupture disk can be adjusted by opening and closing the vent valve. By opening and closing such a vent valve at a predetermined timing, it is possible to accurately release the cooling water from the branch pipe when the discharge pipe is clogged, while avoiding unintended outflow of the cooling water.

[0053] (7) A method of operating a cooling water discharge device according to one aspect includes the steps of: a discharge pipe (12) for discharging cooling water that has cooled components of the nuclear plant; a pump (6) for supplying the cooling water to the discharge pipe; a branch pipe (20) branching from the discharge pipe and communicating with the outside; a rupture disk (26) provided in the branch pipe; a first orifice (24) provided in the discharge pipe downstream of a branch point (13) where the discharge pipe branches off from the branch pipe; a vent valve (30) provided in the branch pipe upstream of the rupture disk and capable of switching a communication state between the branch pipe and the outside; A method of operating a cooling water discharge device, comprising: opening the vent valve while the liquid level of the cooling water in the branch pipe is rising after the pump is started; closing the vent valve when the rise in the liquid level in the branch pipe stops; Equipped with.

[0054] According to the above aspect (7), when the pump is started to introduce cooling water into the discharge pipe, the vent valve installed in the branch pipe is opened. This allows the branch pipe to be at atmospheric pressure when cooling water is introduced into the discharge pipe, thereby reliably preventing unintended rupture of the rupture disk installed in the branch pipe. At this time, some of the cooling water introduced into the discharge pipe is guided into the branch pipe, causing the water level in the branch pipe to rise. Subsequently, when the rise in the water level in the branch pipe stops, the vent valve is closed. This prevents the rupture disk in the branch pipe from bursting, and the cooling water from the discharge pipe is maintained at a predetermined water level. Therefore, when the discharge pipe is blocked, the water level in the branch pipe rises, causing the rupture disk to burst, thereby securing a water discharge path. [Explanation of symbols]

[0055] 1 Cooling system 2 Cooling water supply device 3 Heat exchanger 4 Cooling water discharge device 6. Pump 7 Water supply pipe 10 strainer 12 Water pipe 13 Branching Point 14 Outlet 16 Water Discharge Pit 18 Second Orifice 20 Branch Pipe 20a Part 1 20b 2nd part 24 First Orifice 25 Opening 26 Rupture Disc 28 Flow control valve 30 Vent valve C occlusion V space

Claims

1. a discharge pipe for discharging cooling water that has cooled components of the nuclear plant; a branch pipe branching from the discharge pipe and communicating with the outside; a rupture disk provided in the branch pipe; a first orifice provided in the discharge pipe downstream of a branch point between the discharge pipe and the branch pipe; Equipped with The branch pipe branches upward from the discharge pipe.

2. 2. The cooling water discharge device of claim 1, wherein the first orifice is configured so that a first flow rate of the cooling water flowing through the discharge pipe when the discharge pipe is connected to a water discharge pit is approximately equal to a second flow rate of the cooling water flowing through the discharge pipe when a blockage occurs in the discharge pipe downstream of the branch point.

3. The cooling water discharge device according to claim 1 or 2, further comprising a second orifice provided in the discharge pipe upstream of the branch point.

4. The cooling water discharge device according to claim 1 or 2, further comprising a flow rate adjustment valve provided in the branch pipe between the branch point and the rupture disk, the flow rate adjustment valve being capable of adjusting its opening degree.

5. The cooling water discharge device according to claim 1 or 2, wherein a vent valve capable of switching a communication state between the branch pipe and the outside is provided in the branch pipe upstream of the rupture disk.

6. a discharge pipe for discharging cooling water that has cooled components of the nuclear plant; a pump for supplying the cooling water to the discharge pipe; a branch pipe branching from the discharge pipe and communicating with the outside; a rupture disk provided in the branch pipe; a first orifice provided in the discharge pipe downstream of a branch point between the discharge pipe and the branch pipe; A vent valve is provided in the branch pipe upstream of the rupture disk and capable of switching a communication state between the branch pipe and the outside; A method of operating a cooling water discharge device, comprising: opening the vent valve while the liquid level of the cooling water in the branch pipe is rising after the pump is started; closing the vent valve when the rise in the liquid level in the branch pipe stops; A method of operating a cooling water discharge device, comprising:

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