JP2010085367A - Storage pool facility and method for preventing overflow stream in storage pool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide storage pool facility and an overflow stream prevention method which enables prevention of overflow stream in a storage pool without fail, without having to build banks or catch drains, surrounding the storage pool. <P>SOLUTION: The storage pool facility where members containing radioisotopes, such as, spent fuels discharged from nuclear power plants are immersed and stored in the storage pool 4 includes a water-level monitor means 36 for outputting an overrun signal of a critical water level, when it is determined that the water level of the storage pool 4 has exceeded or is about to exceed the critical water level due to the fluctuation of the water level and water-level regulating means (21 to 23) for lowering the water level of the storage pool 4, by enlarging a pool water filled area located below the normal water level of the storage pool, when an overrun signal of the critical water level is outputted from the water level monitoring means 36. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a storage pool facility for dipping and storing a member containing a radioisotope such as spent fuel discharged from a nuclear power plant in a storage pool, and a method for preventing overflow of the storage pool.

  Spent fuel in the reactor generates heat due to the decay of fission products, so it is temporarily stored in the storage pool until the radioactivity is weakened in the treatment and disposal process. Therefore, the pool water of this storage pool contains a radioisotope, and when the water level fluctuates during an earthquake, the pool water overflows outside the storage pool and there is a risk of contamination of the storage pool facilities.

  Conventionally, there has been a strong demand for storage pool equipment to prevent flooding, and overflow prevention techniques for storage pool equipment listed below have been proposed.

  (1) A horizontal flat plate that can be immersed in the vicinity of the water surface of the storage pool and that can be stored on the side wall of the storage pool is provided, and the horizontal flat plate is pulled out only when water level fluctuations occur in the storage pool. An overflow prevention technique that prevents the pool water from overflowing from the storage pool without impairing the workability of the facility (see, for example, Patent Document 1).

  (2) An embankment will be installed around the storage pool and a drainage channel from the storage pool's operation floor to the aquarium will be installed to prevent the pool water from overflowing from the storage pool and even when the pool water overflows. A storage pool facility that suppresses the pool water dissipation (see, for example, Patent Document 2).

(3) A storage pool facility for preventing the overflow of pool water from the storage pool by providing a bank around the storage pool and adjusting the height of the bank according to the rise of the water surface (for example, Patent Document 3) reference).
JP-A-8-101296 JP 2007-163204 A JP 2006-329799 A

  In the storage pool facility described in Patent Document 1, it is only possible to reduce the water surface fluctuation, and it is not possible to reliably prevent the storage pool from overflowing. In the storage pool facility described in Patent Document 2 and Patent Document 3, an embankment or the like is provided around the storage pool, so that overflow of the storage pool can be reliably prevented, but the operation floor is important in the storage pool facility. The workability in is impaired.

  The present invention has been made in view of the above circumstances, and provides a storage pool facility and a storage pool overflow prevention method that can reliably prevent the storage pool from overflowing without providing a bank or drainage ditch around the storage pool. With the goal.

  In order to achieve the above-described object, in the storage pool facility according to the present invention, in the storage pool facility for storing a member containing a radioisotope such as spent fuel discharged from a nuclear power plant in the storage pool, the storage is performed. When it is determined that the water level of the pool has exceeded or exceeded the limit water level due to fluctuations in the water level, a water level monitoring means for outputting a signal for exceeding the limit water level when it is determined to exceed, and a signal for exceeding the limit water level is output from the water level monitoring means. Sometimes, a water level adjusting means for expanding a pool water filling area located below the normal water level of the storage pool to lower the water level of the storage pool is provided.

  Moreover, in the overflow prevention method for a storage pool according to the present invention, an overflow prevention method for a storage pool facility for immersing and storing a member containing a radioactive isotope such as spent fuel discharged from a nuclear power plant in the storage pool. In this case, when there is a possibility of overflowing from the storage pool due to water level fluctuation, the pool water filling area located below the normal water level of the storage pool is expanded to lower the water level of the storage pool .

  ADVANTAGE OF THE INVENTION According to this invention, the overflow of a storage pool can be prevented reliably, without providing an embankment and a drain ditch around a storage pool.

  Embodiments of a storage pool facility and a storage pool overflow prevention method according to the present invention will be described with reference to the accompanying drawings.

[First embodiment]
1 and 2 are configuration diagrams showing a first embodiment of a storage pool facility according to the present invention. FIG. 1 is a longitudinal sectional view of the storage pool facility, and FIG. 2 is an overhead view of the storage pool facility.

  The storage pool facility 1 of the present embodiment is a storage pool facility that immerses and stores members containing radioisotopes such as spent fuel discharged from a nuclear power plant. As shown in FIGS. 1 and 2, the storage pool facility 1 includes water level adjusting means (21 to 23) and water level monitoring means (31 to 35). In FIG. 1, 4 is a storage pool, 41 is an inner wall surface of the storage pool, 42 is a bottom surface of the storage pool, 43 is an operation floor of the storage pool facility 1, and 51 is a normal water surface of the storage pool 4 (normal water level). ), 6 is spent fuel.

[Water level adjustment means]
The water level adjusting means (21 to 23) of the storage pool facility 1 is a pool located below the water surface 51 (normal water level) of the storage pool 4 when an excess signal of the limit water level is input from the water level monitoring means. The water filling area is expanded and the water level of the storage pool 4 is lowered. The critical water level is set in consideration of the possibility of overflow from the storage pool due to the earthquake. As shown in FIG. 1, the water level adjusting means includes an air bag 21, a supply / exhaust pipe 22, and a supply / exhaust device 23.

  As shown in FIGS. 1 and 2, the air bag 21 of the water level adjusting means is located below the water surface 51 (normal water level) of the storage pool 4 and has an inner wall surface 41 while securing the arrangement space for the spent fuel 6. A plurality are provided along. The shape of the air bladder 21 is not particularly limited and is set to a rectangular parallelepiped or a cylindrical shape.

  A radiation shield 24 is provided above the inside of the air bladder 21. The radiation shield 24 is provided so that a horizontally arranged metal flat plate and a vertically arranged metal flat plate are separated from each other to form an L-shape. On the other hand, a weight 25 whose weight is adjusted so that the air bag 21 is immersed in the storage pool 4 is provided below the air bag 21. Further, as shown in FIG. 2, an air supply / exhaust port 26 is provided at the top of the air bladder 21.

  The air supply / exhaust pipe 22 of the water level adjusting means is connected to the air supply / exhaust device 23 on one side and connected to the air supply / exhaust port 26 of each air bag 21 on the other side to supply air to the air bag 21 or exhaust air from the air bag 21. Served to do.

  The air supply / exhaust device 23 of the water level adjusting means is configured to have a compressor (not shown), and receives an operation by the operator of the storage pool facility 1 to pump air into the air bag 21 through the supply / exhaust piping 22. The air supply / exhaust device 23 is provided for each air bag 21. The air supply / exhaust device 23 exhausts air from the air bag 21 through the air supply / exhaust pipe 22 when receiving an input of an excess signal of a critical water level or an input of a water level lowering signal. More specifically, an electromagnetic valve (not shown) is provided inside the air supply / exhaust device 23, and the exhaust is performed by stopping the compressor and opening the electromagnetic valve. In this exhaust, an air suction device may be provided in the air supply / exhaust device 23 so as to increase the exhaust speed.

[Water level monitoring means]
The water level monitoring means 36 of the storage pool facility 1 gives an excess signal of the limit water level to the air supply / exhaust device 23 of the water level adjusting means when the water level of the storage pool 4 exceeds or exceeds the limit water level due to water level fluctuations. input. As shown in FIGS. 1 and 2, the water level monitoring unit 36 includes a water level meter 31, an accelerometer 32, a seismic intensity meter 33, a manual input unit 34, and a main body 35.

  The water level meter 31 of the water level monitoring means 36 measures the water level of the storage pool 4 and outputs water level data indicating the water level. The accelerometer 32 is installed in the vicinity of the storage pool 4 such as the operation floor 43 of the storage pool facility 1, measures the shaking acceleration around the storage pool 4 due to an earthquake or the like, and outputs acceleration data indicating the acceleration. The seismic intensity meter 33 is provided at a remote location of the storage pool facility 1, measures the seismic intensity at the remote location of the storage pool facility 1, and outputs seismic intensity data indicating the seismic intensity. Both measuring instruments are configured by a known technique. The manual input means 34 receives an operator's operation and outputs a water level drop signal. This water level lowering signal is a request signal for lowering the water level of the storage pool 4 with respect to the air supply / exhaust device 23 of the water level adjusting means, and plays the same role as the signal for exceeding the limit water level.

  FIG. 3 is a functional block diagram of the water level monitoring means in the storage pool facility 1. In FIG. 3, 31 is a water level meter, 32 is an accelerometer, 33 is a seismic intensity meter, 34 is a manual input means, and 35 is a main body.

  As shown in FIG. 3, the main body 35 of the water level monitoring unit 36 receives water level data, acceleration data, and seismic intensity data from a water level meter 31, an accelerometer 32, and a seismic intensity meter 33, respectively. And it is determined whether the received water level data, acceleration data, and seismic intensity data exceed predetermined values. When it is determined that at least one data exceeds a predetermined value, a limit water level excess signal is input to the air supply / exhaust device 23 of the water level adjusting means. When the water level lowering signal is input from the manual input means 34, the water level lowering signal is input to the air supply / exhaust device 23 of the water level adjusting means.

  Next, the operation of the storage pool facility 1 will be described.

  (Coexistence of workability and prevention of overflow) FIG. 4 is an operation explanatory view of the storage pool 4. Conventionally, in the storage pool equipment, the embankment and drainage ditch are built around the entire circumference of the storage pool to prevent overflow from the storage pool facility, and the workability deterioration in the operation floor of the storage pool equipment has been a problem. It was. On the other hand, in the storage pool facility 1, when there is a possibility that pool water overflows from the storage pool 4 due to water level fluctuations induced by an earthquake or the like, the pool water filling located below the normal water level of the storage pool 4 The area is expanded and the water level of the storage pool 4 drops. That is, in the storage pool facility 1, an immersion body such as an air bag 21 in which the pool water does not enter and the volume is variable is disposed in the pool water filling region of the storage pool 4, and the volume of the immersion body is reduced to reduce the pool. The water filling area is expanded and the water level of the storage pool 4 is lowered. In addition, the water level fluctuation is not simply reduced as in the conventional storage pool facility, but the overflow from the storage pool 4 is directly prevented. As a result, it is possible to reliably prevent overflow of the storage pool without adopting a conventional configuration in which a bank is provided around the storage pool 4.

  In addition, in the storage pool facility 1, a plurality of physical quantities that cause fluctuations in the water level of the storage pool 4 such as the water level of the storage pool 4, the acceleration around the storage pool 4, and the seismic intensity of the storage pool 4 can be overflowed. Used as a sex indicator. That is, when any one of the indexes exceeds a predetermined value, the pool water filling area of the storage pool 4 is expanded. Therefore, even if one of the measuring instruments fails and does not operate, the possibility of flooding is determined, and flooding can be prevented with high reliability. The storage pool facility 1 is configured so that the water level in the storage pool 4 can be lowered by manual operation by the operator. In addition to the purpose of preventing overflow, the water level in the storage pool 4 is lowered for work purposes. It can also be made.

  (Maintenance of radiation shielding) The pool water of the storage pool 4 has a function of shielding radiation such as neutron beams derived from spent fuel that is immersed and stored. When the immersion body (for example, the air bag 21) is submerged in the storage pool 4, a region where the pool water is not filled is formed inside the storage pool 4, and there is a concern about an increase in dose above the water surface of the storage pool 4. For this problem, in the storage pool facility 1, the water level is set so that a sufficient radiation shielding function is maintained even when the storage pool 4 is provided with an immersion body, and in addition, the immersion body is shielded against radiation. Radiation shielding measures such as body 24 are provided. For this reason, it becomes possible to achieve both workability and prevention of overflow while maintaining the radiation shielding function of the pool water.

  Next, the effect of the storage pool facility 1 will be described.

Storage pool facility 1
(1) When there is a possibility of overflowing from the storage pool 4 due to water level fluctuation, the pool water filling area located below the normal water level of the storage pool 4 is expanded to lower the water level of the storage pool Is done. For this reason, the overflow of a storage pool can be prevented reliably, without providing an embankment and a drain ditch around a storage pool.

  (2) If a pool water does not enter the pool water filling area and a variable volume immersion body is arranged and there is a possibility of overflow from the storage pool 4 due to water surface fluctuations, the volume of this immersion body is reduced. The pool water filling area is configured to be enlarged. For this reason, the effect of (1) can be obtained without impairing the expected function required for the existing storage pool 4.

  (3) Since a ray shielding measure is provided at least on the top of the immersion body, the effect (1) can be obtained without impairing the radiation shielding function of the pool water.

  (4) Plural kinds of physical quantities that cause fluctuations in the water level of the storage pool 4 are used as an index of the possibility of overflow of pool water, and when any index exceeds a predetermined value, the pool water filling area is expanded. Configured as follows. For this reason, the effect (1) can be obtained with high reliability.

[Second Embodiment]
5-7 is a block diagram which shows 2nd Embodiment of the storage pool equipment which concerns on this invention. FIG. 5 is a sectional view of the storage pool facility, and FIG. 6 is an overhead view of the storage pool facility. FIG. 7 is an enlarged view of a main part of the storage pool facility.

  2nd Embodiment is an example which changed the structure of the water level adjustment means in the storage pool equipment 1 of 1st Embodiment. In addition, the same structure as 1st Embodiment attaches | subjects the same code | symbol, abbreviate | omits description, The structure which changed the structure of 1st Embodiment or added newly adds "A" to the code | symbol end. explain.

  As shown in FIGS. 5 and 6, the storage pool facility 1 </ b> A of this embodiment includes water level adjusting means (26 </ b> A, 271 </ b> A to 273 </ b> A, 281 </ b> A to 283 </ b> A).

  Similar to the water level adjusting unit of the first embodiment, the water level adjusting unit of the present embodiment is positioned below the normal water level of the storage pool when receiving an input of the limit water level excess signal from the water level monitoring unit 36. Enlarge the pool water filling area to lower the water level of the storage pool. This water level adjusting means includes a storage tank 26A (see FIG. 5), shutter devices (271A to 273A) (see FIG. 7), and pool water reflux devices (281A to 283A) (see FIG. 5).

  As shown in FIG. 5, the storage tank 26 </ b> A of the water level adjusting means has a drainage channel 262 </ b> A in which a drainage port 261 </ b> A is set on the inner wall surface 41 located below the normal water level of the storage pool 4. The storage tank 26A communicates with the storage pool 4 through a drainage channel 262A, and is configured to guide the pool water. As shown in FIGS. 5 and 6, the storage tank 26 </ b> A is embedded in the operation floor 43 of the storage pool 4.

  The shutter device of the water level adjusting means normally closes the drainage channel 262A, but opens the drainage channel 262A when an excess signal of the limit water level is received. The excess signal of the critical water level is generated according to the same process as in the first embodiment. Further, after the drainage channel 262A is opened, the drainage channel 262A is closed in response to an operation by the operator. As shown in FIG. 7, the shutter device includes a shutter plate 271A, a wire 272A, and a shutter drive control unit 273A.

  As shown in FIG. 7, the shutter plate 271A of the shutter device has a wire 272A attached to the upper portion thereof, and is provided so as to open and close while sliding the drain port 261A by the vertical movement of the wire 272A. 7A is a diagram showing a state where the shutter plate 271A closes the drain port 261A, and FIG. 7B is a diagram showing a state where the shutter plate 271A opens the drain port 261A.

  The shutter drive control unit 273A of the shutter device winds up the wire 272A when receiving an excess signal of the limit water level, and unwinds the wire 272A in response to an operation by the operator. 7A in FIG. 7 is a stopper. The stopper 7 </ b> A is provided on the inner wall surface 41 of the storage pool facility 1 and is shaped in an L shape projecting from the inner wall surface 41 of the storage pool 4, and extends downward from the stopper 7 </ b> A and toward the inner side of the storage pool 4. The movement of the shutter plate 271A is stopped.

  As shown in FIGS. 5 and 6, the pool water recirculation device of the shutter device includes a drain device 281A, a suction side pipe 282A, and a discharge side pipe 283A. This pool water recirculation device receives the operation by the operator, pumps up the pool water guided to the storage tank 26A through the suction side pipe 282A, and returns the pumped pool water to the storage pool 4 through the discharge side pipe 283A. In the storage pool facility 1A, a mechanism can be provided in which the inside of the storage tank 26A is filled to suck up a gas containing a radioisotope derived from pool water and return it to the storage pool 4.

  Next, the operation of the storage pool facility 1A will be described.

  (Coexistence of workability and overflow prevention) FIG. 8 is an explanatory diagram of the operation of the storage pool facility 1A. In the storage pool facility 1A, when there is a possibility that pool water overflows from the storage pool 4 due to water level fluctuation induced by an earthquake or the like, the drain outlet 261A located below the water surface 51 (normal water level) Opened. Accordingly, the pool water is temporarily stored in the storage tank 26A through the drainage channel 262A, and the water level of the storage pool 4 drops. In FIG. 8, 52 is a water surface when pool water is drained. In addition, when there is no possibility that the storage pool 4 overflows after this drainage is performed, the pool water drained by the operation of the operator is returned to the storage pool 4. In the storage pool facility 1A, not only the water surface fluctuation is reduced as in the conventional storage pool facility, but also overflow from the storage pool 4 is directly prevented. As a result, it is possible to reliably prevent overflow of the storage pool without providing a bank or a drainage ditch around the storage pool 4. Since other operations are the same as those of the first embodiment, description thereof is omitted.

  (Securing storage space) The storage tank 26A of the storage pool facility 1A is buried under the operation floor 43 of the storage pool facility 1A. For this reason, unlike the overflow prevention method of the first embodiment, the immersion storage area of the spent fuel 6 is not eroded even if the overflow prevention is provided.

  Next, the effect of the storage pool facility 1A will be described.

In the storage pool 4, in addition to the effect (1) of the first embodiment,
(5) When a drainage channel 262A having a drainage port 261A is provided on the inner wall surface 41 located below the normal water level of the storage pool 4 and there is a possibility of overflowing from the storage pool, the drainage channel 262A The pool water is configured to be drained temporarily. For this reason, it is possible to reliably prevent overflow of the storage pool without providing an embankment or a drainage ditch around the storage pool and without impairing the immersion storage space for spent nuclear fuel or the like.

  As described above, the storage pool facility according to the present invention has been described based on the first embodiment and the second embodiment, but the specific configuration is not limited to these embodiments and departs from the gist of the present invention. Unless otherwise, design changes and additions are permitted.

  For example, when it is determined that the water level of the storage pool has exceeded the limit water level due to water level fluctuations, or when it is determined that the water level exceeds the limit water level, an alarm device for calling attention may be provided.

The longitudinal cross-sectional view of 1st Embodiment of the storage pool installation which concerns on this invention. The overhead view of 1st Embodiment of the storage pool installation which concerns on this invention. The functional block diagram of the water level monitoring means which determines the overflow possibility from a storage pool. Action | operation explanatory drawing of a storage pool facility. The longitudinal cross-sectional view of 2nd Embodiment of the storage pool installation which concerns on this invention. The overhead view of 2nd Embodiment of the storage pool installation which concerns on this invention. It is principal part explanatory drawing of 2nd Embodiment of the storage pool equipment which concerns on this invention, (a) is a principal part figure which shows the closed state of a shutter board | plate, (b) is a principal part figure which shows the open state of a shutter board | plate. Action | operation explanatory drawing of a storage pool facility.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1, 1A ... Storage pool equipment, 21-23 ... Water level adjustment means, 21 ... Air bag, 22 ... Supply / exhaust piping, 23 ... Supply / exhaust device, 24 ... Radiation shield, 25 ... Weight, 36 ... Water level monitoring means, 31 ... Water level meter, 32 ... Accelerometer, 33 ... Seismometer, 34 ... Manual input means, 35 ... Main body, 4 ... Storage pool, 41 ... Inner wall surface of storage pool, 42 ... Bottom surface of storage pool, 43 ... Storage pool equipment Operation floor 51: Water level of the storage pool (normal water level) 52: Water surface of the storage pool (water level when there is a possibility of overflow), 6 ... Spent fuel, 26A ... Storage tank, 261A ... Drain port, 262A ... Drainage channel, 27A ... Shutter device, 271A ... Shutter plate, 272A ... Wire, 273A ... Shutter drive control unit, 7A ... Stopper, 28A ... Pool water reflux device, 281A ... Drain device, 282A ... Suction side piping, 283 A ... discharge side piping, 29A ... exhaust system. Note that “A” at the end of the reference sign relates to the second embodiment.

Claims (14)

In a storage pool facility for immersing and storing a member containing a radioisotope in a storage pool,
A water level monitoring means for outputting an excess signal of a limit water level when it is determined that the water level of the storage pool has exceeded the limit water level due to water level fluctuation or when it is determined to exceed the limit water level;
A water level adjusting means for expanding the pool water filling area located below the normal water level of the storage pool and lowering the water level of the storage pool when an excess signal of the critical water level is output from the water level monitoring means;
A storage pool facility comprising: The water level adjusting means includes
An air bag provided along an inner surface located below the normal water level of the storage pool, and provided with an air supply / exhaust port;
An air supply / exhaust pipe connected to the air supply / exhaust port of the air bag to guide air exhausted from the air bag or supplied to the air bag;
An air supply / exhaust device for exhausting air from the air bag through the air supply / exhaust pipe when receiving an excess signal of the limit water level, and supplying air to the air bag through the air supply / exhaust pipe in response to the operation signal;
The storage pool facility according to claim 1, comprising:   3. The storage pool according to claim 2, wherein a radiation shield is provided at least at the top of the air bag, and a weight whose weight is adjusted so that the air bag is immersed in the storage pool is provided at the bottom of the air bag. Facility. The water level adjusting means includes
A storage tank in which a drainage port is set on the inner wall surface located below the normal water level of the storage pool, and the pool water is guided by the drainage channel in communication with the storage pool;
A shutter device that is provided to close the drainage channel and opens the drainage channel when an excess signal of the limit water level is received;
A pool water return device that pumps pool water guided to the storage tank by the drainage channel and returns it to the storage pool;
The storage pool facility according to claim 1, comprising: The shutter device includes:
A shutter plate capable of opening and closing the opening surface of the drain port by sliding, a wire attached to the shutter plate,
A shutter drive controller that winds up the wire when an excess signal of the limit water level is received;
A stopper that holds the shutter plate in a state where the shutter plate closes the drain port provided at the opening flange of the drain port;
The storage pool facility according to claim 4, wherein   The said water level monitoring means has a water level meter which measures the water level of a storage pool, and when it determines with the measured water level exceeding a predetermined value, it outputs the excess signal of a limit water level. The storage pool equipment according to any one of 5 to 5.   The water level monitoring means has an accelerometer that measures the acceleration of the operation floor of the storage pool facility, and outputs an excess signal of a critical water level when it is determined that the measured acceleration exceeds a predetermined value; The storage pool facility according to any one of claims 1 to 5.   The water level monitoring means has a seismometer that measures the seismic intensity at a position away from the storage pool facility, and outputs an excess signal of a critical water level when it is determined that the measured seismic intensity exceeds a predetermined value. The storage pool facility according to any one of claims 1 to 5. The water level monitoring means includes
A water level meter that measures the water level of the storage pool, an accelerometer that measures the acceleration of the operating floor of the storage pool facility, and a seismometer that measures the seismic intensity at a position away from the storage pool facility,
6. The excess signal of a critical water level is output when it is determined that at least one of the measured water level, acceleration, and seismic intensity exceeds a predetermined value. Storage pool equipment.   10. The alarm device according to claim 1, further comprising an alarm device for calling attention when it is determined that the water level of the storage pool has exceeded a limit water level due to a water level fluctuation or when it is determined that the water level exceeds the limit water level. The storage pool equipment according to claim 1. In the overflow prevention method for a storage pool facility for immersing and storing a member containing a radioisotope in the storage pool,
A storage pool characterized by expanding the pool water filling area located below the normal water level of the storage pool and lowering the water level of the storage pool when there is a possibility of overflow from the storage pool due to water level fluctuations How to prevent flooding.   In the case where there is a possibility of overflow of the storage pool, a pool water filling area is reduced by reducing the volume of the immersion body in the case where there is a possibility of overflow of the storage pool. 12. The storage pool overflow prevention method according to claim 11, wherein the storage pool overflows.   13. The storage pool overflow prevention method according to claim 12, wherein a radiation shielding measure is provided on at least the top of the immersion body. Provide a drainage channel with a drainage outlet on the inner wall located below the normal water level of the storage pool,
When there is a possibility of overflowing the storage pool due to water level fluctuations, the pool water is temporarily drained from this drainage channel,
12. The method for preventing overflow of a storage pool according to claim 11, wherein when the possibility of overflow of the storage pool disappears after the drainage, the drained pool water is returned to the storage pool.

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