JPH03179298A - Decontaminating apparatus for radioactively contaminated machinery and apparatus - Google Patents

Abstract

PURPOSE:To reduce not only the amount of a decontamination solution but also the amount of waste fluid and to enhance decontamination effect by performing decontamination by utilizing inert gas bubbles having the decontamination solution bonded to the surfaces thereof. CONSTITUTION:A decontamination solution is injected in a container 1 from a decontamination solution tank 5 so as to reach the lower part of the porous plate 4 of the container 1. After the injection of the decontamination solution is completed, inert gas is injected in the decontamination solution stored in the lower part of the container 1 through piping 12 and bubbled. After bubbling, the decontamination solution in the container 1 is drained to a decontamination solution tank 5. Since this drain operation is performed within a short time after the decontamination solution is injected in the container 1, almost no radioactive substance is contained in the drained decontamination solution. The gas bubbles covering radioactively contaminated apparatus 3 have the decontamination solution bonded to the surfaces thereof and the radioactively contaminated apparatus 3 is decontamined by the gas bubbles.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a decontamination device for equipment contaminated with radioactive substances, such as nuclear reactor cooling system equipment.

[Conventional technology]

The cleaning and decontamination method for the reactor cooling system circulation pump will be explained as an example. FIG. 5 shows an example of cleaning the Na pump. The Na pump 4 is placed in the cleaning tank 1 and is fixed to the flange 11 at the top of the cleaning tank 1 by the flange 13 at the top. Flange 1
1 is also for fixing the cleaning tank 1 to the pedestal 3. The upper part of the Na pump is covered with a cover 2.

There is also a flange 12 at the lower end of the cover 2, which is attached to the flange 1 of the cleaning tank 1. By connecting flanges 1 and 2 in this manner, the Na pump 4 is completely covered by the cleaning tank 1 and cover 2. Cleaning tank 1
At the bottom, there is a stop valve 7 that supplies wet nitrogen 5 into the cleaning tank 1.
There is a pipe 6 having a. Moisture in the wet nitrogen 5 supplied to the cleaning tank 1 reacts with Na attached to the Na pump 4 to become sodium hydroxide (NaOH), which becomes liquid and accumulates at the bottom of the cleaning tank 1. The accumulated NaOH is removed from the stop valve 7c.
The NaOH liquid 9 is produced from the drain pipe 10 having the same diameter and is stored in a storage container. On the other hand, the nitrogen 8 from which moisture has been removed above the cleaning tank is led to the gas treatment device through a pipe 9 having a stop valve 7b. The reaction between the moisture in the wet nitrogen 5 in the cleaning tank 1 and the Na attached to the Na pump 4 is monitored with a hydrogen meter, etc. (not shown) installed in the cleaning tank 1. Almost no reaction between the two is observed. When the water is no longer available, distilled water is supplied from the pipe 6 to the cleaning tank 1, reacts with Na remaining in the gap of the Na pump 4, and is recovered from the drain pipe 10 as waste liquid.

Next, the radioactively contaminated equipment in the decontamination container is immersed in the decontamination solution using a slightly acidic decontamination solution, which shows an outline of chemical decontamination that is generally used, and the surface of the equipment is dissolved. The device decontaminates the area by scraping it off, and drains the decontamination solution after a certain period of time. Monitor by dose rate measurement and repeat the above steps if necessary. After decontamination, the equipment is immersed in an alkaline solution to neutralize it, then washed with water and dried.

[Problem to be solved by the invention]

The conventional cleaning method described above is effective in removing radioactive substances attached to the surface of a piece of equipment, but has little effect in removing radioactive substances that have spread and deposited inside the equipment. In addition, the conventional decontamination method described above has a problem in that the amount of waste liquid (decontamination liquid containing radioactive substances) increases after decontamination.

An object of the present invention is to provide radioactively contaminated equipment that can improve the effectiveness of removing radioactive substances and reduce the amount of waste liquid.

[Means to solve the problem]

The above object is achieved by generating bubbles of inert gas with a decontamination liquid attached to the surface inside and outside of a container containing radioactively contaminated equipment, and by covering the equipment with the bubbles and decontaminating the equipment.

That is, the present invention provides a method for removing radioactively contaminated equipment, which is equipped with a container for storing radioactively contaminated equipment, and an internal bubble generating means for generating bubbles of inert gas with a decontamination liquid adhered to the surface within the container. It is a dyeing device.

The present invention also provides a container for storing radioactively contaminated equipment, a porous pedestal provided near the vertical center of the container to support a decontamination device for the radioactively contaminated equipment, and a porous pedestal provided in the lower part of the porous pedestal of the container. a decontamination liquid supply and recovery means for supplying and recovering a decontamination liquid; an inert gas supply means for supplying an inert gas into the decontamination liquid supplied in the container; and a waste liquid communicated with the lower part of the container. This is a decontamination device for radioactively contaminated equipment that is equipped with a recovery tank.

The present invention also provides a container for storing radioactively contaminated equipment, an external bubble generating means for generating bubbles of an inert gas having a decontamination liquid adhered to the surface outside the container, and This is a decontamination device for radioactively contaminated equipment, which is equipped with a line for introducing into the

a container for storing radioactively contaminated equipment; an internal bubble generating means for generating bubbles of inert gas with a decontamination liquid adhered to the surface within the container; external bubble generating means for generating bubbles of active gas;
This decontamination apparatus for radioactively contaminated equipment is equipped with a line for introducing bubbles generated by the external bubble generating means into the container.

Here, the bubbles generated by the internal bubble generating means come into contact with the radioactively contaminated equipment while rising inside the container, and the air bubbles supplied from the external bubble means are blown onto the radioactively contaminated equipment from above and come into contact with the radioactively contaminated equipment. Good.

The present invention also provides a container for storing radioactively contaminated equipment, a porous pedestal provided near the vertical center of the container to support the radioactively contaminated equipment, and a decontamination solution supplied into the lower container of the porous pedestal. This is a decontamination device for radioactively contaminated equipment, which is equipped with a decontamination liquid supply means for supplying a decontamination liquid, and a closed-loop decontamination liquid piping that communicates with the inside of a lower container of a porous pedestal.

[Effect]

Decontamination using inert gas bubbles with decontamination liquid attached to the surface can reduce the amount of waste liquid because a small amount of decontamination liquid is used and a large surface area can be obtained.

Furthermore, by using N2 gas as an inert gas, for example, the oxygen concentration in the decontamination container can be lowered, thereby reducing the formation of an oxide film during decontamination, thereby improving the decontamination effect. .

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

(Example 1) Figure 1 shows an example in which bubbles of inert gas are generated in a container containing radioactively contaminated equipment with decontamination liquid attached to the surface, and the equipment is covered with the bubbles and decontaminated. .

In FIG. 1, a radioactively contaminated device 3 is installed on a pedestal 2 within a container 1. The pedestal 2 has a gap, and a porous plate 4 is provided at the bottom of the gap. The container 1 includes a valve 6 for guiding the decontamination liquid from the decontamination liquid tank 5, a pipe 8 equipped with a pump 7, a pipe 10 equipped with a valve 9 for draining the decontamination liquid,
a pipe 12 equipped with a valve for injecting inert gas;
plumber 4 with a valve 13 for discharging inert gas;
A pipe 17 equipped with a valve 16 for guiding waste liquid after decontamination to a waste liquid recovery tank 15 is connected. Further, the container 1 is provided with a liquid level needle 18, a dissolved oxygen concentration meter 19, and a thermometer 20 as measuring instruments.

In the above configuration, the decontamination liquid is poured from the decontamination liquid tank 5 to the lower part of the porous plate 4 of the container 1. After the injection of the decontamination liquid is completed, an inert gas is injected into the decontamination liquid stored in the lower part of the container 1 through the pipe 12 and is bubbled. The size of the bubbles is adjusted by the porous plate 4, and the radioactively contaminated equipment 3 is immediately covered with the bubbles. After a certain amount of time has passed, stop bubbling with inert gas. Thereafter, the decontamination liquid in the container 1 is drained into the decontamination liquid tank 5. Since this draining operation is performed within a complicated time period for pouring the decontamination liquid into the container 1, the drained decontamination liquid contains almost no radioactive substances. The air bubbles covering the radioactively contaminated equipment 3 have decontamination liquid attached to their surfaces.

As a result, the radioactively contaminated equipment 3 is decontaminated. This decontamination involves removing dirt remaining in the gaps on the equipment surface, as well as Co and Mn that have spread and deposited inside the equipment surface.
This also includes removing radioactive substances such as by dissolving the surface with a decontamination solution and scraping it off. That is, the bubbles collapse and the waste liquid containing the radioactive substance accumulates at the bottom of the container 1.

This waste liquid is collected in the waste liquid recovery tank 15 as radioactive waste.

The above-described operations are repeated as necessary.

Note that the decontamination time varies depending on the shape and size of the target equipment, but it is usually sufficient to expect about 50 to 100 hours.

(Example 2) Figure 2 shows an example in which bubbles of inert gas with decontamination liquid attached to the surface are generated outside a container containing radioactively contaminated equipment, and the equipment is covered with these bubbles for decontamination. .

As shown in FIG. 2, bubbling with an inert gas is carried out in a decontamination liquid tank 5.The size of the bubbles is adjusted by a porous plate 4 provided in the decontamination liquid tank 5, and the bubbles are removed. It is led to the container l through the pipe 8. A plurality of spray nozzles 21 are provided at the tip of the pipe 8, and inert gas with a decontamination liquid attached to the surface is blown out from the nozzles to cover the radioactively contaminated equipment 3 and decontaminate it. In this case, the draining operation of the decontamination liquid shown in Example 1 is not necessary, and only the collection of the waste liquid into the waste liquid recovery tank 15 after decontamination is required.

(Example 3) FIG. 3 is an example in which the above-described Example 1 and Example 2 are combined. That is, this is an embodiment in which bubbles of inert gas are generated inside and outside of a container containing radioactively contaminated equipment, and the surface of the container is covered with a decontamination liquid, and the equipment is covered with the bubbles to decontaminate the equipment.

As shown in FIG.
One side contains the decontamination liquid, piping 8, etc. for sending the decontamination liquid to the container 1, and the other side has the decontamination liquid and the porous pipe for sending the inert gas bubbles to the container 1. Board 4
, an inert gas pipe 12', and a pipe 8'. This embodiment is suitable when the radioactively contaminated equipment 3 has a complicated shape.

(Example 4) In the case of the above-mentioned Examples to Example 3, the injection and discharge of the decontamination liquid into the container was a one-time system, but this was changed to a recirculation system as shown in Figure 4. This is an example.

As shown in FIG. 4, the piping 25 for injecting and discharging the decontamination liquid into the container 1 constitutes a closed loop.

The recirculation system piping 25 is connected to a piping 8 for replenishing decontamination liquid and a piping F for recovering waste liquid. Normally, valve 6 and valve 16 are operated in a closed state.

This embodiment is a modification of the first embodiment described above, but the second and third embodiments described above can also be modified in the same way.

〔Effect of the invention〕

According to the present invention, since decontamination is carried out using inert gas bubbles to which a decontamination liquid is attached to the surface, a small amount of decontamination liquid is required and a large surface area can be obtained, which has the effect of reducing the amount of waste liquid. In addition, as an inert gas, for example.

By using N2 gas, the oxygen concentration in the decontamination container can be lowered, so the decontamination effect can be improved.

For example, decontamination solution 1% oxalic acid + citric acid, decontamination solution temperature 7
When bubbling with N2 gas is performed at 0° C. and for a decontamination time of 100 hours, the decontamination effect is approximately twice as high as when no bubbling is performed.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view of a decontamination device for radioactively contaminated equipment that generates inert gas bubbles in a decontamination container in one embodiment of the present invention, and FIG. FIG. 3 is a vertical cross-sectional view of a decontamination device for radioactively contaminated equipment that generates inert gas bubbles outside a certain decontamination container, and FIG. FIG. 4 is a longitudinal sectional view of a decontamination apparatus for radioactively contaminated equipment, which is a partially modified version of the embodiment described above, and FIG. 5 shows an embodiment of the prior art. l... Container, 2... Frame, 3... Radioactively contaminated equipment, 4... Porous plate, 5... Decontamination liquid tank, 12.1
2', 14...Inert gas piping, 15... Waste liquid recovery tank.

Claims (1)

[Scope of Claims] 1. Radioactively contaminated equipment comprising a container for housing the radioactively contaminated equipment, and internal bubble generating means for generating bubbles of inert gas with a decontamination liquid adhered to the surface within the container. decontamination equipment. 2. A container for storing radioactively contaminated equipment, a porous pedestal installed near the vertical center of the container to support a decontamination device for the radioactively contaminated equipment, and a decontamination liquid in the lower part of the porous pedestal of the container. a decontamination liquid supply and recovery means for supplying and recovering;
A decontamination device for radioactively contaminated equipment, comprising an inert gas supply means for supplying an inert gas into a decontamination liquid supplied in the container, and a waste liquid recovery tank communicated with a lower part of the container. 3. A container for storing radioactively contaminated equipment, an external bubble generating means for generating bubbles of inert gas with a decontamination liquid attached to the surface outside the container, and a line for introducing the bubbles into the container; Decontamination equipment for radioactively contaminated equipment. 4. A container for storing radioactively contaminated equipment, an internal bubble generating means for generating bubbles of inert gas with a decontamination liquid attached to the surface within the container, and a container for causing the decontamination liquid to be attached to the surface outside the container. A decontamination device for radioactively contaminated equipment, comprising an external bubble generating means for generating bubbles of an inert gas, and a line for introducing the bubbles generated by the external bubble generating means into the container. 5. In claim 4, the bubbles generated by the internal bubble generating means come into contact with the radioactively contaminated equipment while rising within the container, and the air bubbles supplied from the external bubble means are blown from above and come into contact with the radioactively contaminated equipment. Decontamination equipment for radioactively contaminated equipment. 6. A container for storing radioactively contaminated equipment, a porous pedestal provided near the vertical center of the container to support the radioactively contaminated equipment, and a decontamination solution for supplying decontaminating fluid into the lower container of the porous pedestal. A decontamination device for radioactively contaminated equipment, comprising a supply means and a closed loop decontamination liquid piping communicating with the inside of a lower container of a porous mount.