JPH0431796A - Ventilation of vertically placed tanks for nuclear power facility during its maintenance - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a ventilation method during maintenance of a tank whose inner surface is contaminated with harmful substances such as radioactive substances.

[Conventional technology]

In general, vertical tanks installed in nuclear power facilities such as nuclear power plants, especially tanks that contain radioactive materials, have manholes (11 ) (13) are installed on the side walls and the roof, and nozzles (12) for pressure adjustment, etc. are installed on the roof, respectively.

Since such vertical tanks are contaminated with radioactive materials, sufficient ventilation is required throughout maintenance, especially to reduce radiation exposure to workers and prevent the spread of radioactive materials. Here, conventional ventilation during maintenance uses manholes (11) and (13) installed on the side wall and roof of the tank (1) as air supply and exhaust ports, as shown in FIG. That is, specifically, the ducts (21
) (31) are inserted into the respective manholes (11) and (13) for ventilation.

However, tanks for personnel and materials needed during maintenance (
1) When going in and out, please use the manhole (1) as mentioned above.
1) Attach the duct (2) of the air supply and exhaust system (2) (3) to (13).
1) (31) had been inserted, so it had to be pulled out, and ventilation was, of course, temporarily stopped. This was a problem in terms of safety and radiation control, and stopping the exhaust was extremely problematic, especially from the perspective of ventilating radioactive contamination.

By the way, in order to solve this problem, it is sufficient to provide one of the tanks (1) with a dedicated supply and exhaust port for ventilation. ), as shown in Figure 3, temporarily construct a large construction opening (14) in the side plate of the tank (1) and supply and exhaust air from there to ensure sufficient ventilation throughout. I have to.

[Problem that the invention seeks to solve]

However, although the above-mentioned ventilation method solves the safety management problem, it also has the above-mentioned drawbacks.

■ When performing maintenance on a vertical tank, it is necessary to temporarily construct a construction opening in the main body.

■ When maintenance is completed, welding and other work openings must be closed, and if anti-corrosion paint is applied inside the tank, it will also be necessary to repair it.

■ After closing the construction opening, it is necessary to inspect it for quality control reasons.

Therefore, with the ventilation method that provides a construction entrance, the processes before and after maintenance are more complicated than with the conventional ventilation method that does not have a construction entrance, and the construction period is also longer, reducing overall work efficiency. There was a problem.

The present invention was devised in view of the above-mentioned problems, and allows sufficient ventilation without providing any ventilation openings.
The purpose is to provide a ventilation method during maintenance of vertical tanks for nuclear facilities.

[Means for solving problems]

Therefore, in the method for ventilating a vertical tank for a nuclear facility according to the present invention, when the inside of the vertical tank is ventilated by an air supply device and an exhaust device, air is supplied or exhausted from a manhole installed in the vertical tank. At the same time, one of the above is performed, and the air supplied to the manhole is exhausted from a roof nozzle installed on the roof of the vertically installed tank, or the air is supplied to the exhaust from the manhole, and the tank is installed vertically. The basic feature is to create a negative pressure inside the tank.

〔Example〕

Hereinafter, specific embodiments of the present invention will be described based on FIG. In the figure, (1) is a vertical tank, (2) is an air supply system, (3) is an exhaust system, (11) is a roof manhole,
(12) is a roof nozzle, and (13) is a side manhole.

In this embodiment, the air supply system M (2) and the exhaust system (3)
is installed outside the vertical tank (1), and either one is installed!
(2) and (3) are also composed of the main body and ducts (21) and (31).

The air supply duct (21) of the air supply system W (2) is inserted through the roof manhole (11). This air supply duct (21)
The structure may be such that the manhole is inserted through the side manhole (13), but at least one of the two manholes needs to be opened for the entry and exit of workers and materials.

Therefore, in this embodiment, the side manhole (13) has an open configuration.

The exhaust duct (31) of the exhaust system (3) is connected to each of the roof nozzles (12) installed at two locations on the roof of the vertical tank (1). Normally, a vacuum relief valve, vent, pressure relief valve, etc. are attached to the roof nozzle (12) to adjust the pressure inside the tank, but these devices must be removed when connecting to the exhaust duct (31). . Also, although the number of roof nozzles (12) differs depending on the tank, all nozzles (12)
) It is not necessary to connect the exhaust duct (31) to the exhaust duct (31), and it goes without saying that it should be connected according to the displacement. For example, the main body of (3) is an air filter (32)
(so-called HEPA filter, etc.) and exhaust fan (33)
A device with the following is used.

As described above, in this embodiment, the roof manhole (1
1) is used as an air supply port and the roof nozzle (12) is used as an exhaust port, but this is the opposite configuration, that is, the roof manhole (11) is used as an exhaust port and the roof nozzle (12) is used as an air supply port. It may be any configuration you use. In either configuration, the exhaust volume should be at least larger than the supply air volume, and the tank (
1) Create negative pressure inside.

This is to prevent internal air from flowing out through the open side manhole (13) and other openings, and to prevent harmful substances within the tank (1) from diffusing to the outside.

With this configuration, vertical tanks (
The internal state of 1) is as follows.

First, the dirty air in the tank (1) is drained from the roof nozzle (
12), passes through the exhaust duct (31), and connects to the exhaust system (3).
The body removes harmful substances such as radioactive substances and exhausts them. On the other hand, fresh outside air passes through the air supply duct (21) and is supplied into the tank (1) via the roof manhole (11) due to the air supply amount W(2). At this time, since the ventilation exhaust volume is always greater than the supply air volume, the tank (1
) The inside is under negative pressure.

As mentioned above, the side manhole (13) is open for the entry and exit of personnel necessary for maintenance of the tank (1) and the transportation of materials. In addition, if there is a large amount of material and it is not enough to take it in and out only through the side manhole (13), you can also pull out the air supply duct (11) inserted into the roof manhole (13) for a short time. In this case, the air supply is temporarily stopped, but in this embodiment, exhaust from the roof nozzle (12) can continue, so there is no problem in terms of safety management, at least for a short time.

In this way, in this embodiment, when maintaining the tank (1), the roof manhole (11) is connected to the air supply port and the roof nozzle (
12) is used as the exhaust port, and the side manhole (13) is used as the entrance and exit for people and materials, so the ventilation port and the entrance and exit for materials are separate, so materials can be brought in and out without having to temporarily stop ventilation. It can be done.

〔Effect of the invention〕

As described in detail above, according to the present invention, sufficient ventilation can be achieved without providing any work openings during maintenance of a vertical tank.

Furthermore, since there is no need to provide a construction opening, maintenance can be carried out at low cost and in a short period of time, and overall work efficiency does not decrease.

[Brief explanation of the drawings] Fig. 1 is a block diagram of an embodiment of the present invention, Fig. 2 is a block diagram of a conventional ventilation method during tank maintenance, and Fig. 3 is a temporary construction of a construction opening in the tank side plate. It is a block diagram of a ventilation method. In the figure, (1) is a vertical tank, and (2) is an air supply device. (3) is an exhaust system, (11) is a roof manhole, (12)
) is the roof nozzle, (13) is the side manhole, (14) is the construction opening, (21) is the air supply duct, (31) is the exhaust duct, (32) is the air filter, and (33) is the exhaust fan. show.

Claims (1)

[Scope of Claims] When ventilating the inside of a vertical tank for a nuclear facility using an air supply device and an exhaust device, one of air supply or exhaust is performed from a manhole installed in the vertical tank, and the Exhausting the air supplied to the manhole from a roof nozzle installed on the roof of the vertical tank, or supplying air to the exhaust air from the manhole, and bringing the inside of the vertical tank into a negative pressure state. Features: Ventilation method for vertical tanks for nuclear facilities.