JP2876230B2 - Decontamination equipment for radioactive contamination equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a decontamination apparatus for equipment contaminated with radioactive materials such as reactor cooling equipment.

[Conventional technology]

The cleaning and decontamination method of the circulating pump of the reactor cooling system will be described as an example. Fig. 5 shows an example of cleaning the Na pump.
Is placed in the cleaning tank 1 and fixed to the flange 11 on the upper part of the cleaning tank 1 by the flange 13 on the upper part. The flange 11 is for fixing the washing tank 1 to the gantry 3. Na
The upper part of the pump is covered with a cover 2. A flange 12 is also provided at the lower end of the cover 2, and is attached to the flange 11 of the cleaning tank 1. By connecting the flanges 11 and 12 in this manner, the Na pump 4 is completely covered with the washing tank 1 and the cover 2. A pipe 6 having a stop valve 7a for supplying wet nitrogen 5 into the cleaning tank 1 is provided below the cleaning tank 1.
The water in the wet nitrogen 5 supplied to the cleaning tank 1 reacts with Na adhering to the Na pump 4 to become sodium hydroxide (NaOH), becomes a liquid, and accumulates at the lower part of the cleaning tank 1. Accumulated NaOH
Becomes NaOH solution 9 from a drain pipe 10 having a stop valve 7c and is stored in a storage container. On the other hand, the nitrogen 8 from which moisture has been removed in the cleaning tank 1 is guided to a gas processing device from a pipe 9 having a stop valve 7b. Moisture and Na in wet nitrogen 5 in cleaning tank 1
The reaction with Na attached to the pump 4 is monitored by a hydrogen meter or the like (not shown) attached to the washing tank 1. When almost no reaction is observed between the two, distilled water is supplied from the pipe 6 to the washing tank 1 to react with Na remaining in the gap of the Na pump 4 and collected from the drain pipe 10 as waste liquid.

Next, the outline of chemical decontamination generally used for the decontamination method will be described. A weakly acidic decontamination solution is used to immerse the radioactively contaminated equipment in the decontamination container in the decontamination liquid, dissolve the surface of this equipment and remove it, and drain the decontamination liquid after a certain period of time. Monitor by dose rate measurement and repeat the above operation if necessary. After decontamination, the device is immersed in an alkaline solution to neutralize, and then washed with water and dried.

[Problems to be solved by the invention]

The above-described conventional cleaning method is effective for removing radioactive substances adhering to the surface of the device, but has almost no effect on radioactive materials diffused and deposited inside the device. In addition, there is a problem that the amount of waste liquid (decontamination liquid containing a radioactive substance) after the decontamination increases in the decontamination method of the related art.

An object of the present invention is to provide a decontamination apparatus for a radioactively polluted device, which can improve the effect of removing radioactive substances and reduce the amount of waste liquid.

[Means for solving the problem]

The above object is achieved by generating air bubbles of an inert gas having a decontamination liquid adhered to the surface inside and outside of a container accommodating radioactive contaminated equipment, and covering the equipment with the air bubbles for decontamination.

That is, the present invention provides a method for removing a radioactively contaminated device comprising: a container for accommodating the radioactively contaminated device; and an internal bubble generating means for generating a bubble of an inert gas having a decontamination liquid adhered to the surface in the container. It is a dyeing device.

Also, the present invention provides a container for storing radioactive contamination equipment,
A perforated pedestal provided near the center in the vertical direction in the container to support the decontamination device of the radioactively contaminated device, and a decontaminated liquid supply / recovery means for supplying and recovering the decontaminated liquid into the lower part of the perforated pedestal of the container And an inert gas supply means for supplying an inert gas into the decontamination liquid supplied to the container, and a waste liquid recovery tank communicated with the lower part of the container. is there.

Also, the present invention provides a container for storing radioactive contamination equipment,
A decontamination apparatus for radioactive contamination equipment comprising: an external bubble generating means for generating bubbles of an inert gas having a decontamination liquid adhered to the surface outside the container; and a line for introducing the bubbles into the container. is there.

Also, the present invention provides a container for storing radioactive contamination equipment,
Internal air bubble generating means for generating air bubbles of an inert gas having a decontamination liquid adhered to the surface thereof inside the container, and external air bubbles for generating air bubbles of an inert gas having a decontamination liquid adhered to the surface outside the container A decontamination apparatus for a radioactively polluted device, comprising: a generation unit; and a line for introducing bubbles generated by the external bubble generation unit into the container. Here, the air bubbles generated by the internal air bubble generating means come into contact with the radioactively contaminated device while ascending in the container, and the air bubbles supplied from the external air bubble generating means are blown into contact with the radioactively contaminated device from above. Is good.

Also, the present invention provides a container for storing radioactive contamination equipment,
A perforated pedestal provided near the center in the vertical direction in the container and supporting the radioactively contaminated device, a decontamination liquid supply means for supplying a decontamination liquid into a lower container of the perforated gantry, and a lower container of the perforated pedestal A decontamination apparatus for radioactive contamination equipment, comprising:

[Action]

Performing decontamination with bubbles of an inert gas having a decontamination liquid adhered to the surface can reduce the amount of waste liquid because the decontamination liquid is small and the surface area is large.

Further, for example, by using an N ₂ gas as an inert gas to reduce the oxygen concentration in the decontamination container, it is possible to reduce the formation of an oxide film during decontamination, thereby improving the decontamination effect. it can.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Example 1) Fig. 1 shows the generation of an inert gas bubble having a decontamination liquid attached to the surface thereof in a container containing radioactive contamination equipment.
This is an example of covering and decontaminating the device with these bubbles.

In FIG. 1, a radioactive contamination device 3 is installed on a gantry 2 in a container 1. The gantry 2 has a gap, and a porous plate 4 is provided below the gap. The container 1 has a valve 6 for guiding the decontamination liquid from the decontamination liquid tank 5, a pipe 8 having a pump 7, a pipe 10 having a valve 9 for draining the decontamination liquid,
A pipe 12 provided with a valve 11 for injecting an inert gas, a pipe 14 provided with a valve 13 for discharging an inert gas, and a valve 16 for guiding waste liquid after decontamination to a waste liquid recovery tank 15 are provided. The pipe 17 is connected. The container 1 is provided with a liquid level meter 18, a dissolved oxygen concentration meter 19, and a thermometer 20 as measuring devices.

In the above configuration, the decontamination liquid is injected 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 bubbled. The size of the bubbles is adjusted by the porous plate 4, and the radioactive contamination device 3 is immediately covered with the bubbles. After a certain period of time, stop bubbling with an inert gas. Thereafter, the decontamination liquid in the container 1 is drained into the decontamination liquid tank 5. This draining operation is performed within a short time after the decontamination liquid is poured into the container 1, so that the drained decontamination liquid hardly contains a radioactive substance. The air bubbles covering the radioactively contaminated device 3 have a decontamination liquid attached to the surface, whereby the radioactively contaminated device 3 is decontaminated. This decontamination involves removing dirt remaining in gaps on the equipment surface, and also dissolving radioactive substances such as Co and Mn that have diffused and deposited inside the equipment surface with the decontamination liquid. And removal by scraping. That is, the bubbles collapse and the waste liquid containing the radioactive substance accumulates in the lower part of the container 1. This waste liquid is collected in the waste liquid recovery tank 15 as radioactive waste.

The above operation is repeated as necessary. still,
The decontamination time varies depending on the shape and size of the target equipment, but 50
Expecting ~ 100 hours is usually sufficient.

(Example 2) Fig. 2 shows the generation of an inert gas bubble having a decontamination liquid attached to the surface outside a container containing radioactive contamination equipment.
This is an example of covering and decontaminating the device with these bubbles.

As shown in FIG. 2, bubbling with an inert gas
This is performed in the decontamination liquid tank 5. The size of the bubbles is adjusted by the porous plate 4 provided in the decontamination liquid tank 5, and the bubbles are guided to the container 1 through the pipe 8. A plurality of spray nozzles 21 are provided at the tip of the pipe 8, and an inert gas having a decontamination liquid adhered to the surface from the nozzles blows out to cover the radioactive contaminated device 3 for decontamination. In this case, the draining operation of the decontamination liquid shown in the first embodiment is unnecessary, and only the recovery of the waste liquid in the waste liquid recovery tank 15 after decontamination is required.

(Embodiment 3) FIG. 3 shows an embodiment in which Embodiments 1 and 2 are used in combination. That is, in this embodiment, air bubbles of an inert gas having a decontamination liquid adhered to the surface thereof are generated inside and outside a container storing radioactive contamination equipment, and the equipment is covered with the air bubbles and decontamination is performed.

As shown in FIG. 3, the interior of the decontamination liquid tank 5 is
One is a decontamination solution for sending out the decontamination solution to the container 1, the piping 8, and the other is a decontamination solution for sending out bubbles of the inert gas to the container 1, and a porous material. It comprises a plate 4, an inert gas pipe 12 'and a pipe 8'. This embodiment is suitable when the radioactive contamination device 3 has a complicated shape.

(Example 4) In the case of Examples 1 to 3 described above, the decontamination solution was injected and discharged into the container by a one-through method, but this was changed to a recirculation method as shown in FIG. It is an example.

As shown in FIG. 4, a pipe 25 for injecting and discharging the decontamination liquid into the container 1 forms a closed loop. A pipe 8 for replenishing the decontamination liquid and a pipe 17 for collecting waste liquid are connected to the recirculation system pipe 25. Normally, valve 6 and valve 16
Is operated in a closed state.

Note that the present embodiment is a modification of the first embodiment, but the same can be applied to the second and third embodiments.

〔The invention's effect〕

ADVANTAGE OF THE INVENTION According to this invention, since it decontaminates by the bubble of the inert gas which made the decontamination liquid adhere to the surface, the decontamination liquid has a small amount and a large surface area, and has the effect of reducing the amount of waste liquid. Further, for example, by using N ₂ gas as the inert gas, the oxygen concentration in the decontamination container can be reduced, so that the decontamination effect can be improved.

For example, decontamination solution 1% oxalic acid + citric acid, decontamination solution temperature
When bubbling with N ₂ gas was performed at 70 ° C. and decontamination time was 100 h, it was about 2
Double the decontamination effect.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a decontamination apparatus of a radioactive contamination device for generating an inert gas bubble in a decontamination container of one embodiment of the present invention, and FIG. 2 is another embodiment of the present invention. FIG. 3 is a vertical cross-sectional view of a decontamination apparatus of a radioactive contaminated device that generates an inert gas bubble outside a certain decontamination container, and FIG. 3 is a vertical cross section of a decontamination device of the radioactive contaminated device using the two embodiments in combination. FIG. 4 is a longitudinal sectional view of a decontamination apparatus for a radioactive contamination device in which a part of the above embodiment is modified, and FIG. 5 shows an embodiment of the prior art. DESCRIPTION OF SYMBOLS 1 ... Container, 2 ... Stand, 3 ... Radioactive contamination equipment, 4 ... Porous plate, 5 ... Decontamination liquid tank, 12, 12 ', 14 ... Inert gas piping,
15… Waste liquid recovery tank.

──────────────────────────────────────────────────続 き Continued on the front page (72) Shigehiro Shimoyashiki, 1168 Moriyamacho, Hitachi City, Ibaraki Prefecture Inside Energy Laboratory, Hitachi, Ltd. (72) Inventor Takayoshi Hikichi 1168 Moriyamamachi, Hitachi City, Ibaraki Prefecture Energy, Hitachi (56) References JP-A-60-256100 (JP, A) JP-A-62-91900 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G21F 9/28

Claims (2)

(57) [Claims] 1. A container for accommodating a radioactively polluted device, a perforated pedestal provided near the center in the up-down direction of the container to support a decontamination device for the radioactively contaminated device, and A decontamination liquid supply / recovery means for supplying and recovering the liquor, an inert gas supply means for supplying an inert gas into the decontamination liquid supplied into the container, and a waste liquid recovery communicated with a lower part of the container A decontamination device for radioactive contamination equipment, comprising: a tank; 2. A container for accommodating a radioactively contaminated device, a perforated pedestal provided near the center of the container in the up-down direction to support the radioactively contaminated device, and a decontamination liquid supplied to a lower container of the perforated pedestal. A decontamination apparatus for radioactive contamination equipment, comprising: a decontamination liquid supply means; and a closed-loop decontamination liquid pipe communicating with the inside of the lower container of the porous frame.