JPH0452888B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a leakage detection device for lined containers that eliminates the problem of false leakage in lined containers that are frequently used in nuclear power plants and the like.

[Technical background of the invention and its problems] In a nuclear power plant, a fuel pool,
Lined containers with concrete walls lined with lining plates are used as containers for storing radioactive materials, such as equipment storage pits and waste liquid storage pools.

This lined container is equipped with a leak detection device, and is configured to issue an alarm if a leak occurs in the lined container.

Fig. 1 shows an example of a conventional lined container and its leakage detection device.A lined container 1 used as a fuel pool, equipment storage pit, and waste liquid storage pool has a concrete wall 2 made of metal such as an austenitic stainless steel plate. Lining board 3
The lining container 1 is connected to an inflow pipe 1A and an outflow pipe 1B. A plurality of embedded fittings 4 made of angle material or the like are embedded in the concrete wall 2 flush with the inner surface of the concrete wall 2.

A plurality of anchors (not shown) are welded to the back side of these embedded metal fittings 4, and the embedded metal fittings 4 are firmly fixed to the concrete wall 2.

A gap 5 of about 5 mm is formed between the concrete wall 2 of the lining container 1 and the lining plate 3, and a leak detection device 6 is installed in this gap 5 to detect leaked liquid. There is.

This leak detection device 6 includes a plurality of leak detection pipes 7 that communicate with the gap 5, a main pipe 8 that collects leaked liquid flowing into these leak detection pipes, and this main pipe 8.
A drain tank 10 is connected to the drain tank 10 via piping 9.

The drain tank 10 includes the drain tank 10.
a liquid level detector 11 that detects the liquid level of leaked liquid accumulated in the interior; and an alarm device 1 that displays an alarm when the liquid level detector 11 detects a preset high liquid level.
2 are connected.

A drain pipe 13 equipped with a normally closed valve 13A is connected to the drain tank 10, and an overflow pipe 14 is connected between the pipe 9 and the drain pipe 13 to bypass the drain tank 10 and the normally closed valve 13A. There is.

In the leak detection device for a lined container having such a configuration, when a leak occurs from a welded part of the lining plate 3, the liquid leaked into the gap 5 between the lining plate 3 and the concrete wall 2 is transferred to the leak detection pipe 7. , drain tank 1 via main pipe 8 and piping 9
Collected to 0.

As a result, when the liquid level detector 11 detects a preset high liquid level, it is determined that a leak has occurred, and the alarm 12
An alert will be displayed. By the way, when the air in the gap 5 between the concrete wall 2 and the lining plate 3 cools, condensation occurs, and as in the case of condensed water leaking, the leakage detection piping 7 and main pipe 8 that communicate with the gap 5
The water is collected in a drain tank 10 via piping 9. As a result, when the liquid level in the drain tank 10 reaches a preset high liquid level, an alarm will be displayed by the alarm device 12 even though no leakage has occurred.

Once an alarm is generated due to such a pseudo-leakage, the plant operation will be in an emergency state, and the effluent will be analyzed and investigated to determine whether it is a real leak or a pseudo-leakage. .

Thereafter, necessary processing is performed based on the determination result, but if the water stored in the lining container has the same quality as the pseudo-leak water, it cannot be determined. In this case, the container should be inspected as a true leak. Further, even if water quality analysis determines that the leak is a pseudo-leakage, the impact on plant operations during that time can be significant.

Next, the results of an investigation into the occurrence of dew condensation in lined containers will be explained.

Concrete wall 2 lined with lining board 3
When high-temperature air enters between the concrete wall 2 and the lining plate 3 from the structural gaps of various piping and wiring that penetrate the
, and a so-called descending air flow is generated.

In other words, the air pressure between each room in a nuclear power plant is usually controlled by ventilation and air conditioning equipment to prevent the spread of radioactive materials, and the air pressure between each room usually has a pressure difference of several millimeters in the water column. It is being This pressure difference causes extremely small (several mm/second to several mm/second to several
cm/sec) air flow is occurring. The amount and direction of this air flow will vary for each container.

Further, the temperature of the liquid stored in the lining container 1 is often higher than the ambient temperature. In this case, the flowing air is warmed by the high temperature liquid stored in the lining container 1 via the lining plate 3, and descends while increasing in temperature and humidity.
After that, it is cooled and condensed, and the condensed water flows down.

However, this downward airflow is caused by the fact that the inside of the funnel where the end of the leakage detection system is open is connected to a concrete wall.
This occurs when the air pressure is lower than the air pressure between the The difference between the air pressure between the two and the air pressure inside the funnel is not constant, and the pressure difference may be strong or weak or reversed depending on the operating conditions of ventilation air conditioning equipment, weather conditions, and the opening and closing of the door. There is. This variation in differential pressure relationship is the reason why there are lined containers that generate dew condensation and lined containers that do not.

In addition, the air between the concrete wall 2 and the lining plate 3 is not the same due to the structure of the various piping and wiring that penetrate the concrete wall 2, even between the leak detection sections of one lining container. , temperature, and humidity are also not the same. Therefore, even between the leakage detection sections of the same lined container, there are cases where dew condensation occurs and cases where no condensation occurs.

It was confirmed that no condensation occurs when the air flow is completely stopped or when the air flow is upward.

However, in rare cases, condensation may occur even in lined containers that prevent air flow. This is because when the air in the stopped state is hot and humid, when the liquid level in the lining container decreases, the temperature of the air that has been warmed by the high temperature liquid via the lining plate 3 decreases and condensation occurs. Especially when discharging a large amount of high-temperature liquid that has been stored for a long time, there is a lot of condensation water.

Therefore, as a result of investigation, it has been found that blocking the air circulation path is the most effective means for preventing the occurrence of condensation. It was also discovered that when there is a large amount of dew condensation from stationary air, it cannot be dealt with by blocking the air circulation path, so it is necessary to generate an upward airflow.

As mentioned above, in general, in a nuclear power plant, there are lined containers that generate dew condensation and lined containers that do not generate dew condensation. Also,
Even in lined containers that generate condensation, there are leak detection sections that generate condensation and leak detection sections that do not. Moreover, the occurrence of dew condensation is also affected by the weather conditions at the location where the nuclear power plant is installed.
For example, they tend to occur relatively frequently during periods of high humidity or high temperature and humidity, and are also affected by the installation location of the lining container and leak detection device within the nuclear power plant, as well as the ventilation conditions there.

[Object of the Invention] The present invention was made in view of the above-mentioned investigation results, and an object of the present invention is to provide a highly reliable leak detection device for lined containers that prevents the occurrence of false leaks.

[Summary of the Invention] That is, the leak detection device for a lined container of the present invention comprises: a leak detection pipe communicating between the gaps of a lined container formed by lining a concrete frame with a lining plate spaced apart; a drain tank that accommodates leaked liquid flowing into the service piping;
The leak detection device consists of a drain pipe that connects the drain tank and the funnel, and a level switch that activates and issues an alarm when the liquid level in the drain tank rises above a set value. The present invention is characterized in that a pipe opening/closing mechanism is installed in the overflow pipe that opens at the top of the drain tank, which blocks the air circulation path from the pipe to the funnel and allows leaked liquid to overflow from the drain tank.

[Embodiments of the Invention] Hereinafter, embodiments of the present invention will be described with reference to FIGS. 2 to 4. In these figures, the same members as in FIG. 1 and each figure are given the same reference numerals.

FIG. 2 shows an embodiment of the present invention in which a pipe opening/closing mechanism is provided in the overflow pipe of the drain tank.

In the leak detection device 6 of this embodiment, an air supply branch pipe 20 is connected to a pipe 9 that guides the leaked liquid.
A level switch 21 is attached to the drain tank 10, and an overflow pipe 14 equipped with a solenoid valve 14A is disposed above the detection level. A normally closed valve 1 is installed at the bottom of the drain tank 10.
A drain pipe 13 with a diameter of 3A is provided to lead water to the funnel 22. Reference numeral 23 is a viewing box for visually observing leakage water flowing from the leakage detection piping 7 to the piping 9, and is made entirely or partially of a transparent material.

The effect when leaked liquid flows into the device of the present invention having such a configuration will be explained.

When a leak occurs in the lining plate 3, the leaked liquid is
It flows into the drain tank 10 from the pipe 9 via the leak detection pipe 7 and the viewing box 23. When the inflow continues and the liquid level rises and reaches the detection level of the level switch 21, the level switch 21
is activated to issue an alarm to the central control room, and the solenoid valve 14A is activated to open the pipeline, allowing the water in the drain tank 10 to overflow. As the inflow continues, the liquid level rises and reaches the overflow level, after which the inflow amount overflows, so the liquid level becomes stable and the overflow continues. The liquid in the drain tank 10 is drained by artificially opening the normally closed valve 13A as part of post-leakage treatment.

Next, the pseudo-leakage prevention effect in this device will be explained.

By providing the solenoid valve 14A as a pipe opening/closing mechanism in the overflow pipe 14, the air that reaches the funnel 22 from the gap 5 through the leak detection pipe 7, the viewing box 23, the pipe 9, the drain tank 10, and the overflow pipe 14 Distribution channels will be cut off. Therefore, the air flow in interval 5 is stopped,
This prevents the air that transports moisture from flowing into the space 5 between the concrete wall 2 and the lining plate 3, preventing moisture from being supplied from the outside and causing condensation due to increased moisture. Therefore, no condensed water flows into the drain tank 10.
At this time, there is a possibility that a small amount of moisture in the stationary air will condense, but the amount is very small and it is unlikely that it will flow down as dew water.

However, in rare cases, even a lined container that prevents air flow may generate enough condensation to flow down. This is because when the air in a stationary state is hot and humid, if the liquid level in the lined container falls, the high temperature liquid will cause condensation to flow down. As a result, the temperature of the air that has been heated through the lining plate 3 drops and condensation occurs, especially when a large amount of high-temperature liquid that has been stored for a long period of time is discharged, resulting in a large amount of condensed water. If there is a large amount of dew condensation from the stopped air in this way, simply blocking the air circulation path will not have sufficient pseudo-leakage prevention ability.
Air is supplied from the pipe 9 to the pipe 9. For example, viewing box 2
3 to check whether there is condensed water at the tip of the leakage detection piping 7, and if water droplets are found at the tip, air is supplied through the air supply branch pipe 20. The supplied air is transferred to the funnel 22 by the solenoid valve 14A.
Since the flow path to the side is blocked, the leaked liquid moves backward through the path, becomes an upward flow, and flows through the gap 5. This dries and eliminates condensation, which is the biggest cause of false leaks.

The embodiment shown in FIG. 3 shows an example in which a float type opening/closing device 30 is inserted into the lower bent portion of the overflow pipe 14 instead of the electromagnetic valve 14 shown in FIG. 2 as a conduit opening/closing mechanism.

Further, in this embodiment, the air supply branch pipe 20 opens into the viewing box 23.

As shown in FIG. 4, the float-type opening/closing device 30 has overflow pipes 1 on the upper side wall and on the bottom surface, respectively.
4, a lid 41 that airtightly closes the upper end of the outer cylinder, and a float 42 that is housed in the outer cylinder 40 so as to be able to move up and down. The float 42 has a built-in weight 44 with an appropriate weight so that it floats when the liquid level of the leaked liquid 3 in the outer cylinder 40 reaches a predetermined level. An O-ring 45 is attached that closes the inlet of the overflow pipe 14 that opens to the inside.

In the embodiment shown in FIGS. 3 and 4, when a leak occurs in the lining plate 3, the leaked liquid flows into the drain tank 5, passes through the leak detection pipe 7, the visual box 23, and the pipe 9, and then passes through the drain tank. 10. When the liquid level in the drain tank 10 rises due to this inflow and reaches the set level, the level switch 21 is activated to issue an alarm to the central control room.

When the liquid level in the drain tank 10 rises further and reaches the overflow level, the leaked liquid flows through the overflow pipe 14 to the float type opening/closing container 30.
The water flows into the outer cylinder 40 of. The bottom surface of the outer cylinder 40 is normally closed by the O-ring 45 of the float 42, but when the liquid level inside the outer cylinder rises to a predetermined level, the float 42 floats up and the O-ring 45 closes the outer cylinder 40.
Since the leakage liquid in the outer cylinder 40 passes through the overflow pipe 14 again and enters the funnel 2.
Flows into 2.

As mentioned above, in the embodiment shown in FIG. 3, a float type opening/closing device 30 is inserted into the overflow pipe 14 as a pipe opening/closing mechanism, and the float 42 of this opening/closing device normally lands on the bottom surface of the outer cylinder. Since the overflow pipe 14 is closed by the O-ring 45,
Leakage detection piping 7 from the gap 5 of the lining plate 3;
The air flow path leading to the funnel 22 via the viewing box 23, piping 9, drain tank 10, and overflow pipe 14 is blocked. Therefore, the air flow in the air circulation path is stopped, and as a result, the air that transports moisture cannot flow into the gap 5 between the concrete wall 2 and the lining plate 3, and the outside Since moisture is not supplied from
Condensed water does not flow into the drain tank 10. At this time, there is a possibility that a small amount of moisture in the stationary air will condense, but the amount is extremely small and will rarely flow down as dew condensation water.

However, as mentioned above, if there is a large amount of dew condensation from the stopped air, if air is supplied from the air supply branch pipe 20 to the viewing box 23, as in the case of FIG.
The air moves backwards along the path of the leaking liquid and becomes an upward flow.
Since the water flows through the gap 5, the condensation is dried and disappears.

As described above, in the leak detection device for a lined container of the present invention, the overflow pipe is equipped with a solenoid valve that is automatically opened in the event of an overflow by a level switch, or a pipe that includes a float-type opening/closing device that is operated by the buoyancy of overflowing liquid. By installing a channel opening/closing mechanism, air flow between the concrete wall and the lining plate in the lined container is blocked, thereby suppressing the occurrence of condensation, which is the biggest cause of false leaks, and preventing false leaks. It has the effect of

In addition, even if condensation occurs, the condensation can be dried by supplying air from the piping above the drain tank or the air supply branch pipe installed in the viewing box, completely preventing pseudo-leakage. can be prevented.

Furthermore, when a viewing box is installed, the tips of the leak detection piping are differentiated for each piping and introduced into the viewing box, so leaks can be confirmed visually through the viewing box. Furthermore, when a solenoid valve is used as the conduit opening/closing mechanism, the conduit can be opened and closed reliably and quickly.

[Effects of the Invention] As is clear from the above description, according to the present invention, it is possible to prevent a downward air flow from occurring between the concrete wall and the lining plate in a lined container, and thereby The occurrence of dew condensation between the two ends can be suppressed as much as possible. Therefore, it is possible to provide a leak detection device for a lined container that eliminates the problem of false leakage, and has very large effects such as being able to significantly improve plant safety and reliability.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a lined container and a conventional leak detection device for a lined container, Figs. 2 and 3 are block diagrams showing an embodiment of the present invention, respectively, and Fig. 4 is a float type opening/closing diagram in Fig. 3. FIG. 3 is a longitudinal cross-sectional view of the device. 1... Lining container, 2... Concrete wall, 3... Lining board, 4... Embedded metal fittings, 5...
...= Between, 6... Leak detection device, 7... Leak detection piping, 8... Main pipe, 9... Piping, 10... Drain tank, 11... Liquid level detector, 12... Alarm,
13...Drain piping, 13A...Normally closed valve, 14...
...Overflow pipe, 14A...Solenoid valve, 20...
Air supply branch pipe, 21...Level switch, 22...
... Funnel, 23 ... Viewing box, 30 ... Float type opening/closing device, 40 ... Outer cylinder, 41 ... Lid, 42 ...
Float, 43... Leakage liquid, 44... Weight, 45...
O-ring.

Claims (1)

[Claims] 1. A leak detection pipe that communicates between the two spaces of a lined container formed by lining a concrete frame with lining plates spaced apart from each other, a drain tank that accommodates leaked liquid flowing into this leak detection pipe, and this drain. In a leak detection device consisting of a drain pipe that communicates between a tank and a funnel, and a level switch that activates and issues an alarm when the liquid level in the drain tank rises above a set value, the leak detection device is A pipe opening/closing mechanism is installed in the overflow pipe that opens at the top of the drain tank, which blocks the air circulation path from the pipe to the funnel and allows the leaked liquid to overflow from the drain tank. Leak detection device for lined containers.