JP2002168984A - Suppression pool water draining system for nuclear power plant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a draining system for S/P water of a nuclear power plant and a water supply system for an auxiliary fuel pool with a simple system by sharing an SPCU system. SOLUTION: By installing a piping 6 communicating an F/D 3 downstream side of the SPCU system to an SAP waste water tank 4 or the auxiliary fuel pool 15, the S/P water passed from an S/P 1 to the F/D 3 by a pump 2 and purified can be transferred to the S/P waster water tank 4 or the auxiliary fuel pool 15 with maintained or improved water quality. By utilizing facilities of an existing SPCU system during the transfer, increase of costs can be minimized by a simple system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a suppression pool water drainage system that shares a suppression pool purification system of a nuclear power plant.

[0002]

2. Description of the Related Art In a nuclear power plant, a suppression pool (hereinafter, referred to as S / P) for condensing steam released from a reactor pressure vessel stored in a reactor containment vessel is provided.
Indicated as P. 1) is installed in the same containment vessel. S / P water is stored in the S / P 1 as a coolant that condenses steam.

[0003] The drainage of the S / P1 is caused by the inner wall of the S / P1 or the S / P.
It is carried out at the time of regular inspection about once every 10 years for the purpose of maintenance and inspection of valves and the like provided in the pipe connected to 1. When draining the S / P1 water, an S / P water drainage tank 4 for receiving the drained S / P1 water is installed outside the reactor containment vessel, and the S / P water is transferred to the S / P water drainage tank 4. Therefore, S / P water is temporarily stored.

After the S / P1 side maintenance inspection is completed,
By returning the water in the S / P water drainage tank 4 to the S / P1, maintenance and inspection of the S / P1 side is performed without wasting the S / P water. At this time, when transferring water to the S / P water drainage tank 4, as shown in FIG. 6, pumps 18, 19, and 20 of a residual heat removal system (hereinafter, referred to as RHR system).
A line 33 branching from the exit to the S / P water drainage tank 4,
S / P water was transferred by using the main lines 33, 34, and 35.

[0005] An S / P water purification system (hereinafter, referred to as a SPCU system) of a nuclear power plant will be described.
The SPCU system has a system configuration as shown in FIG.
The S / P water in the S / P 1 is passed through a filtration / desalination apparatus (hereinafter referred to as F / D) 3 using an SPCU-based pump 2,
/ P1 The system is installed as a system that purifies water and returns the purified S / P water to S / P1.

[0006] The presence of the SPCU system keeps the S / P water during normal operation at a good water quality, so that it is possible to use the S / P1 water for filling the reactor well during periodic inspections. .

[0007]

In the conventional nuclear power plant, the case where the SPCU system is not installed and the case where the SPCU system is installed
In some cases, a CU system is installed. In the latter case, S
The S / P water can be directly used for filling the reactor well without purifying the / P water in the rad facility of the nuclear power plant.

Also, when draining S / P water, there is no particular provision of a purification facility, and the wastewater is either returned to the S / P after purification treatment in a rad facility or returned to the S / P as it is. However, if the drainage of S / P water is outdoors,
Particularly when draining P water, it is desired to reduce pollutants by water purification. Further, in order to use the S / P water for filling the reactor well, it is desirable that the quality of the water returned to the S / P be maintained well.

On the other hand, since the rad facility does not have the ability to treat a large amount of water such as S / P water in a short time, it can be purified in a short time by another facility without using the rad facility. desired. On the other hand, nuclear power plants are required to be cost competitive with other power plants, and a significant increase in cost may lead to a decrease in competitiveness.

Accordingly, a main object of the present invention is to propose an S / P water drainage system while suppressing an increase in cost by utilizing existing facilities. Another object is to propose an S / P water drainage system for achieving maintenance / improvement of water quality at the time of S / P drainage in addition to the main purpose.

[0011]

SUMMARY OF THE INVENTION The present invention provides an S / P contained in a reactor containment vessel (hereinafter referred to as PCV).
And draining the S / P water in the S / P,
An S / P water storage tank having a function of storing P water, and S / P from the S / P via an S / P purification pump and F / D.
In the SPCU system having a line returning to / P, the SPC
U / S S / P purification pump or S / P from downstream of F / D
It is characterized in that a pipe communicating with the water storage tank is installed and S / P water is switched from the SPCU system to the S / P water storage tank for distribution.

With the above configuration, the S / P purification pump can be used to transfer the S / P water to the S / P water drainage tank 4.

In the case of passing through the F / D, the water passed through the F / D is transferred to the S / P water drainage tank 4, so that the S / P water is transmitted through the F / D. It is possible to provide a high-performance system capable of draining S / P water while purifying water.

As described above, the S / P water is transferred or purified using the existing SPCU-based pump or the pump and the F / D, so that the factor of cost increase is suppressed.

Further, in addition to the above configuration, the SPCU system F
/ D downstream from the S / P water storage tank by a piping arrangement that does not generate high points,
When the level of the S / P water drainage tank is set higher than the P water level, the S / P from the S / P water drainage tank is dropped by gravity.
Since it is possible to return the product, a return pump is not required, and a rational system can be provided.

In the above, even if the S / P water storage tank is replaced with an auxiliary fuel pool, the factor of cost increase is similarly suppressed.

Further, in a nuclear power plant in which an auxiliary fuel pool is also installed, the communication pipe is branched from a communication pipe to the S / P water drainage tank and provided with a communication pipe to the auxiliary fuel pool. By sharing a part, not only the drainage of S / P water to the S / P water drainage tank, but also the replenishment of S / P water to the auxiliary fuel pool, cost increase can be suppressed as much as possible, and F If the S / P water of good quality passed through / D can be supplied to the auxiliary fuel pool, a more rational and high-performance system can be provided.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings. In a nuclear power plant, an S / P 1 for condensing steam leaked from a reactor pressure vessel stored in a reactor containment vessel is provided in the same reactor containment vessel. S / P water is stored in the S / P 1 as a coolant that condenses steam.

The drainage of the S / P1 is caused by the inner wall of the S / P1 and the S / P.
It is carried out at the time of regular inspection about once every 10 years for the purpose of maintenance and inspection of valves and the like provided in the pipe connected to 1. At the time of discharging the S / P1 water, the S / P water drainage tank 4 for receiving the drained S / P1 water is installed either inside or outside the reactor containment vessel, and the S / P water drainage tank 4 is supplied to the S / P water drainage tank 4. And temporarily store the S / P water.

After the maintenance and inspection on the S / P1 side is completed,
By returning the water in the S / P water drainage tank 4 to the S / P1, maintenance and inspection of the S / P1 side is performed without wasting the S / P water. At this time, when transferring the water to the S / P water drainage tank 4, the S / P water was transferred by using the SPCU pump 2 as shown in FIG.

The SPCU system employs a system configuration as shown in FIG.
The S / P water in 1 is passed through a filtration and desalination device (hereinafter referred to as F / D) 3 to purify the S / P1 water, and the S / P1 is purified.
It is installed as a system to return the S / P water after purification.

The presence of the SPCU system keeps the S / P water during the normal operation at a good quality, so that the S / P1 water can be used for filling the reactor well at the time of the periodic inspection. .

As shown in FIG. 1, a suppression pool water drainage system (hereinafter referred to as SPH system) is connected to the SPCU system. The range enclosed by the dashed line in FIG. 1 is the SPCU system, and the thick solid line is the SPH system.
In FIG. 1, the SPCU system is installed in a PCV near S / P1 for the purpose of purifying S / P water of S / P1.

The SPCU system has the following components from upstream to downstream, and each component is connected by a process pipe 7. That is, a pump 2 of the SPCU system from the upstream side, a flow meter 5 for measuring the flow rate of water passing from the pump 2,
A valve 10 provided with a valve 8, an F / D 3, a valve 9 and a valve 11, and provided in the middle of a process pipe connecting the process pipe between the flow meter 5 and the valve 8 and the process pipe between the valve 9 and the valve 11 S / P water is sucked from the S / P 1 into the SPCU system by the pump 2 and the flow rate of the S / P water measured by the flow meter 5 is F /
Filtered at D3 and pumped back to S / P1.

When such purification is performed, as shown in FIG. 7, the pumps 8, 9, and 11 are opened and the pump 2 is driven while the valve 10 is closed, so that the S / P in the S / P 1 is opened. The S / P water purification function is exhibited by circulating water while passing it through the F / D3. This SPCU system is operated when the conductivity of the S / P water in the S / P1 increases during normal operation or during periodic inspection, so that the S / P in the S / P1 is increased.
The quality of the P water is well maintained.

On the other hand, the S / P water drainage tank 4 is arranged at a position distant from the S / P 1 due to tank space. During the periodic inspection, the S / P water drainage tank 4
It is installed for the purpose of temporarily storing S / P water in S / P1 when performing maintenance and inspection of P1.

The transfer of the S / P water to the S / P water drainage tank 4 was carried out by diverting some SPCU system equipment. For this purpose, the SPCU system is connected to the SPH system as shown in FIG. The SPH system includes a pipe 6, valves 41 and 42 provided in the middle of the pipe 6, and a pump 43 provided in the pipe 6 in parallel with the valve 42. One end of the pipe 6 is connected to the process pipe 7 between the SPCU valve 9 and the valve 11, and the other end is connected to the S / P water drainage tank 4.

In order to transfer the S / P water in the S / P 1 to the S / P water drainage tank 4, as shown in FIG. 1, the SPCU valves 8 and 9 are opened, and the valves 10 and 11 are closed. And pump 2
And the valves 41 and 42 in the SPH system
Achieved by opening.

According to the opening / closing state of each valve, the S / P water in the S / P 1 sucked by the pump 2 is measured by the flow meter 5 and then passed through the F / D 3 to the F / D 3. The S / P water purified in / D3 is transferred to the S / P water drain tank 4 through the pipe 6, and the purified S / P water is drained to the S / P water drain tank 4, where it is drained. Water is temporarily stored until maintenance and inspection of S / P1 is completed.

On the other hand, the rated flow rate of the SPCU system is equivalent to the system flow rate required by the SPH system, and there is no difference in drainage time. As a result, the existing facilities can be used effectively and the S / P
It can be said that a system capable of improving water quality can be provided.

However, in order to use the SPCU system pump 2 without any change from the prior art, it is necessary to raise the pump 2 head when the elevation difference between the pump 2 and the S / P water drainage tank 4 and the pressure loss due to the SPH system are rated. (Pressing force).

After the maintenance and inspection of the S / P 1 is completed, the valve 4
With the valve 1 and the valve 11 opened and the valve 42 and the valves 8, 9 and 10 closed, the pump 43 is driven to return the S / P water in the S / P water drainage tank 4 to the S / P1. Since the S / P water in the S / P water drainage tank 4 has been purified, the water is quickly returned without being passed through the purification facility when the water is returned.

The second embodiment of the present invention shown in FIG. 2 does not make a high point on the route of the pipe 6 from the SPCU system of the first embodiment shown in FIG. 1 to the S / P water drainage tank 4, ie, This is a pipe configuration in which the route of the pipe 6 is not arranged above the drain tank. Thus, when the water is returned from the S / P water drain tank 4 to the S / P 1, it is not necessary to use the pump 43 and the valve 42 in the first embodiment.

That is, from the S / P water drainage tank 4 to the S / P1
To return the water to the valve, the valves 41 and 11 are opened, and the valves 8 and
9 and 10 are closed. In such a state, the S / P water in the S / P water drainage tank 4 is returned to the S / P 1 through the pipe 6 by gravity.

The purging of the S / P water in the S / P 1 by the SPCU system is performed by closing the SPH system valve 41 and the SPCU system valve 10.
This is performed by driving the pump 2 with the PCU valves 8, 9, 11 open. Other configurations and operations are the same as those of the first embodiment.

According to the second embodiment, the facility for returning the S / P water in the S / P water drainage tank 4 to the S / P 1 through the pipe 6 is simplified, and the amount of equipment and labor for installation are reduced. The effect that can be obtained is obtained.

In the third embodiment of the present invention shown in FIG. 3, the SPCU system described in the first embodiment and the auxiliary fuel pool 13 of the nuclear power plant are connected to each other by a route which does not cause a high point with respect to the auxiliary fuel pool 13. 13 and a valve 14 is provided in the middle of the pipe 13. The piping 1
3 and the valve 14 constitute a makeup water system. In the third embodiment, the connection destination of the pipe 13 to the SPCU system is in the process pipe 7 between the flow meter 5 and the valve 8.

In FIG. 3, the SPCU valves 10, 1
After closing 1 and opening the valve 14 of the makeup water system,
When the pump 2 is driven, S / P water in the S / P 1 is sucked out by the pump 2 and the flow rate measured by the flow meter 5 is changed to F / D 3
The fuel is quickly supplied to the auxiliary fuel pool 15 through the pipe 13 without being subjected to the purifying action of the fuel. Therefore, it can respond to a rapid demand for make-up water. The S / P water once supplied as supplementary water into the auxiliary fuel pool 15 is S / P
Normally, it is not returned into the S / P 1, but if it is desired to return it, the valve 14 is opened and the water is returned into the S / P 1 via the pipe 13 via the pump 2 by using gravity. After that, the pump 2 is driven while the valve 14 is closed and the valves 8, 9, and 11 are opened to purify the S / P water in the S / P1 by the F / D3.

S in S / P1 by SPCU system at normal time
/ P water purification is performed by SPH valve 14 and SPCU valve 1
0 is closed, and the pump 2 is driven with the SPCU valves 8, 9, 11 open. Other configurations and operations are the same as those of the first embodiment.

The fourth embodiment shown in FIG. 4 is different from the third embodiment shown in FIG. 3 in that the connection of the supply water system pipe 13 to the SPCU system is on the downstream side of the F / D 3 and the valves 9 and The process pipe 7 between 10 is provided.

In the fourth embodiment, the normal SP
To purify the S / P water in the S / P 1 by the CU system, the pump 2 is driven with the valve 14 of the makeup water system and the valve 10 of the SPCU system closed, and the valves 8, 9, and 11 of the SPCU system open. Done by

S / S is supplied into the auxiliary fuel pool 15 as makeup water.
When supplying P water, the pump 2 is driven after closing the valves 10 and 11 of the SPCU system and opening the valve 14 of the makeup water system. When the pump 2 is driven, S / P water in the S / P 1 is sucked out by the pump 2, and the flow rate measured by the flow meter 5 is subjected to the purifying action by the F / D 3, passes through the pipe 13, and passes through the auxiliary fuel. It is supplied into the pool 15.

Therefore, the make-up water into the auxiliary fuel pool 15 is high-quality make-up water which has been subjected to the purifying action by the F / D 3. Normally, the S / P water once supplied as supplementary water into the auxiliary fuel pool 15 is not returned to the S / P 1, but if it is desired to return, the valve 11,
14 is opened, valves 8, 9 and 10 are closed, and
1 and returned into the S / P1 by gravity. Thereafter, if necessary, the valve 14 is closed and the valves 8, 9, and 11 are opened, and the pump 2 is driven to carefully purify the S / P water in the S / P1 again by the F / D3. Other configurations and operations are the same as those of the first embodiment.

The auxiliary fuel pool 15 shown in FIGS.
Is a new pool that is set up so that fuel can be stored separately from the conventional fuel pool. Therefore, as in the case of the conventional fuel pool, it is necessary to replenish the fuel pool water in the event that the fuel pool water amount drops. The replenishment of the fuel pool water can be carried out by the RHR system.
The CU system has a function of replenishing the auxiliary fuel pool 15.

Thus, when the SPCU system is installed closer to the auxiliary fuel pool 15 than the RHR system, the supply pipe length can be reduced as compared with the supply of make-up water by the RHR system. Therefore, it is possible to provide a system that can be expected to reduce costs.

Further, by providing a branch point of the pipe 13 to the auxiliary fuel pool 15 on the further downstream side of the flow meter installed on the downstream side of the SPCU pump 2, it is possible to measure the flow rate using existing equipment. Therefore, it is possible to provide a system that is comparable in terms of functions such as monitoring of the amount of makeup water. In addition, as shown in FIG.
By providing a branch point of the pipe 13 to the auxiliary fuel pool 15 on the downstream side of / D3, it is possible to simultaneously purify make-up water to the auxiliary fuel pool 15.

The fifth embodiment shown in FIG. 5 is a combination of the SPCU system and the SPH system described in the second embodiment and a makeup water system for the auxiliary fuel pool 15 described in the fourth embodiment. Having. That is, as in the second embodiment, SPCU
One end of the SPH system pipe 6 is connected to the process pipe 7 between the system valves 9 and 11.

The other end of the pipe 6 is the S / P water drain tank 4
Through a valve 41. The SPH system includes the pipe 6 and the valve 41. One end of the branch pipe 16 is connected to a portion of the pipe 6 closer to the SPCU system than the valve 41. The other end of the branch pipe 16 is connected to the auxiliary fuel pool 1 via the valve 14.
5 is connected. Routing is performed so that a high point higher than the S / P water drainage tank 4 and the auxiliary fuel pool 15 is not generated in any of the pipe routes of the pipes 6 and 16.

S in S / P1 by SPCU system at normal time
The / P water purification is performed in the same manner as in the first embodiment by driving the pump 2 with the valves 14, 41 and the SPCU-based valve 10 closed and the SPCU-based valves 8, 9, 11 open. I can do it.

S / S as supplement water into the auxiliary fuel pool 15
When supplying P water, the pump 2 is driven after closing the valves 10 and 11 of the SPCU system and opening the valve 14 of the makeup water system. When the pump 2 is driven, S / P water in the S / P 1 is sucked out by the pump 2, and the flow rate measured by the flow meter 5 is subjected to a purifying action by the F / D 3, and the pipe 6 is connected to the pipe 16 and the valve. The fuel is supplied into the auxiliary fuel pool 15 through the fuel tank 14.

Therefore, the make-up water into the auxiliary fuel pool 15 is a good-quality make-up water which has been subjected to the purifying action by the F / D 3. Normally, the S / P water once supplied as supplementary water into the auxiliary fuel pool 15 is not returned to the S / P 1, but if it is desired to return, the valve 11,
14 is opened, valves 8, 9, 10 are closed, and valve 14 and piping 16
And the pipe 6 and the valve 11 are sequentially returned into the S / P 1 by gravity. Thereafter, the valve 14 is closed as necessary,
With the valves 8, 9, 11 opened, the pump 2 is driven to
The S / P water in P1 is carefully purified again by F / D3.

When the S / P water in the S / P 1 is temporarily drained and stored in the S / P water drainage tank 4 during maintenance and inspection in the S / P 1, the SPCU type valves 10 and 11 are used. The pump 2 is driven after the valve 14 of the makeup water system is closed and the valve 41 of the SPH system is opened. When the pump 2 is driven, S / P water in the S / P 1 is sucked out by the pump 2,
The flow rate measured by the flow meter 5 is subjected to the purifying action by the F / D 3 and is discharged from the pipe 6 through the valve 41 into the S / P water drainage tank 4, where it is stored.

After the maintenance inspection in S / P1 is completed, S / P1
When returning the S / P water in the S / P water drainage tank 4 to the inside, the valves 41 and 11 are opened, and the valves 8, 9, 10, and 14 are opened.
Is closed. In such a state, the S / P water in the S / P water drainage tank 4 is returned to the S / P 1 through the valve 14 and the pipe 6 due to gravity. Since the returned S / P water has been subjected to the purifying action by the F / D3 in advance, the purifying action is not required during the returning, and quick returning is possible.

As shown in FIG. 5, when the auxiliary fuel pool 15 and the S / P water drainage tank 4 are arranged in the same direction,
S / P water drainage tank 4 downstream of SPCU F / D3
And a branch pipe 16 to the auxiliary fuel pool 15 is provided in the middle of the pipe 6. Accordingly, in addition to the simple configuration in which the pipe 6 is not equipped with a pump, the auxiliary fuel pool 15 and the S / P water
Since a part of the piping constituting the flow path to the P water drainage tank 4 can be used, the amount of piping can be reduced.

As described above, according to the first embodiment, SP
By installing a pipe from the CU system downstream of the F / D to the S / P water drainage tank, the water that has passed through the F / D can be sent to the S / P.
Since the water is transferred to the water drainage tank 4, the S / P water passing through the SPH system is purified using the SPCU system F / D, and the S / P water can be drained. The advantage is that it is possible to provide a simple and high-performance system capable of appropriately maintaining or improving the system.

According to the second embodiment, the SPC of the first embodiment
By changing to a piping configuration that does not create a high point in the piping line from the U system to the S / P water drainage tank 4,
The return of water from the / P water drainage tank 4 to the S / P can be performed by gravity, and in addition to the effects of the first embodiment, the amount of equipment and the like can be reduced.

According to the third embodiment, by providing the SPCU system with a function of replenishing the auxiliary fuel pool, the length of the supply pipe can be shortened as compared with the related art, and the SPCU system can be used.
By providing a branch line to the auxiliary fuel pool further downstream of the flow meter installed on the downstream side of the CU pump, the flow rate can be measured.

According to the fourth embodiment, in addition to the effect of the third embodiment, by providing a branch line to the auxiliary fuel pool downstream of the SPCU system F / D, the water supply to the auxiliary fuel pool is provided. Purification can be performed at the same time.

According to the fifth embodiment, in addition to the effect of each embodiment, a part of the pipe for supplying the S / P water to the auxiliary fuel pool and the S / P water drainage tank 4 is shared. Therefore, a further reduction in the amount of piping can be expected.

[0060]

As described above, according to the present invention, the SPCU system configuration of a nuclear power plant can be shared with another system, and the other system can be completed as a simple system.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram of an SPH system / SPCU system in a nuclear power plant according to a first embodiment of the present invention.

FIG. 2 is a system configuration diagram of an SPH system / SPCU system in a nuclear power plant according to a second embodiment of the present invention.

FIG. 3 is a system configuration diagram of a water supply system / SPCU system for an auxiliary fuel pool in a nuclear power plant according to a third embodiment of the present invention.

FIG. 4 is a system configuration diagram of a water supply system / SPCU system for an auxiliary fuel pool in a nuclear power plant according to a fourth embodiment of the present invention.

FIG. 5 shows a water supply system / SPH system / SPC for an auxiliary fuel pool in a nuclear power plant according to a fifth embodiment of the present invention.
It is a system configuration | structure figure of U system.

FIG. 6 shows S in a nuclear power plant according to the prior art.
It is a system configuration | structure figure of PH system / RHR system.

FIG. 7 shows S in a nuclear power plant according to the prior art.
FIG. 3 is a system configuration diagram of a PCU system.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Suppression pool (S / P), 2,43 ... Pump, 3 ... Filtration and desalination apparatus (F / D), 4 ... S / P water drainage tank, 5 ... Flow meter, 6, 13 ... Piping, 8, 9,10,1
1, 14, 41, 42 ... valve, 16 ... branch pipe, 15 ... auxiliary fuel pool.

Continuation of the front page (72) Inventor Hiroshi Sasaki 3-2-1 Sachimachi, Hitachi-shi, Ibaraki F-term (reference) in Hitachi Engineering Co., Ltd. 2G002 AA01 DA06 EA10

Claims (5)

[Claims] 1. A distribution destination of suppression pool water can be switched between at least one of a suppression pool water drainage tank or an auxiliary fuel pool and a suppression pool from a downstream side of a suppression pool water purification system pump of a nuclear power plant. Suppression pool water drainage system of a nuclear power plant connected by piping. 2. The suppression pool water purification system according to claim 1, wherein a pipe connected to at least one of the suppression pool water drainage tank or the auxiliary fuel pool is connected to the suppression pool water purification system by filtration and desalination of the suppression pool water purification system. A suppression pool water drainage system for a nuclear power plant, which is located downstream of the device. 3. The suppression pool water purification system according to claim 1, wherein a pipe connected to at least one of the suppression pool water drainage tank and the auxiliary fuel pool is connected to the suppression pool water purification system by a flow meter of the suppression pool water purification system. The suppression pool water drainage system of a nuclear power plant, which is also downstream. 4. The pipe according to any one of claims 1 to 3, wherein the pipe is connected to both the suppression pool water drainage tank and the auxiliary fuel pool, and a part of the pipe in a connection route is provided. A suppression pool water drainage system for a nuclear power plant, wherein the common piping connects to both of the above. 5. The suppression pool water drainage tank or the auxiliary fuel pool according to claim 1, wherein a pipe connected to at least one of the suppression pool water drainage tank or the auxiliary fuel pool is provided. A water supply system for a suppression pool of a nuclear power plant, wherein the water system is disposed below.