JPH05150094A - Decontamination method for radioactive contaminated object with methylenechloride and device thereof - Google Patents

Abstract

PURPOSE:To improve a decontamination method for a radioactive contaminated object using hydrocarbonfluoride/perchloroethylene, and provide a decontamination method and the device for a radioactive contaminated object of which decontaminating effect is excellent, environmental pollution is little, consumed electric power for decontamination of decontamination agent itself is very small, and possibility of deterioration of the agent on the cotamination process is little. CONSTITUTION:Methylenechloride liquid 7 is ejected against a radioactive contaminated object, or attachment (usually coating layer of epoxy resin paint) is previously impregnated and swelled by methylenechloride liquid 7 and the liquid 7 is ejected against it. Thereafter, the liquid is separated from the attachment by means of a filter 13, then the methylenechloride liquid 7 itself is decontaminated by distillation, and the decontaminated liquid is used for ejection against a contaminated object. As for the device, a decontamination chamber 1, a filter 13, a distillation device 18, a pump 17, and the like. and further perfluoroelastomer packing between respective pipings, are provided.

Description

Detailed Description of the Invention

[0001]

This invention relates to decontamination of radioactive contaminants contaminated with radioactivity such as nuclear reactor equipment used in nuclear power plants, peripheral equipment, piping, tools used, etc. with methylene chloride. The present invention relates to a method and a decontamination device.

[0002]

2. Description of the Related Art Conventionally, in a nuclear power plant or the like, radioactive pollutants are generated with the progress of its operation. It occurs when parts of various facilities such as the power plant are replaced or overhauled, and they are usually stored as they are or cut and stored in drums, and stored in abandoned mines and the like. However, in this case, the storage amount increases year by year, and the storage space will soon become insufficient only with the abandoned mine, etc. Therefore, a storage facility is usually created in a region remote from the city and where there are few inhabitants, and the pollutants are stored there. However, doing so often causes an opposition movement by the residents of the area where the storage facility is installed, causing social problems. A number of inventions have been made to solve such problems, all of which attempt to decontaminate radioactive contaminants to reduce the amount of the contaminants stored.

As an example of such prior art, Japanese Examined Patent Publication No.
The invention described in Japanese Patent Publication No. 9-36240 may be mentioned. This invention contains fluorocarbons, perchlorethylene, etc. in a container, warms them, and vibrates them using an ultrasonic vibration device, and puts radioactively contaminated objects in these solutions. , Is to be decontaminated.

[0004]

However, the above-mentioned conventional methods have the following drawbacks. First, the fluorohydrocarbon and perchlorethylene both have low radioactive decontamination ability. This low decontamination ability is extremely low, as will be apparent from the results of experiments for comparison with the present invention described later. Second, the fluorohydrocarbon and perchlorethylene both cause pollution. As is well known about the pollution caused by fluorohydrocarbons, it destroys the ozone layer surrounding the earth and forms ozone holes, so that the absorption of solar ultraviolet rays by ozone is extinguished, thereby increasing the number of cancer patients worldwide. Has been banned for use by the United Nations, and the manufacture and use of the products are prohibited by the end of this century under the Montreal Protocol by UN member states. Also, perchlorethylene has carcinogenicity, and when it is released into the air, it causes poisoning due to contact with skin and ingestion from the mouth and causes pollution. Permissible concentration of perchlorethylene in air is 100ppm
Is. Perchlorethylene is 19 in the United States.
Manufacture and use are banned in 1996.

Next, in the process of decontaminating radioactive pollutants, the above-mentioned perchlorethylene decontaminates perchlorethylene itself which is a decontaminating agent, that is, decontamination of perchlorethylene itself by distillation. At the time of this decontamination, the high boiling point (boiling point 121,2 ° C) consumes a large amount of power and inefficiency is inevitable. In addition, the above-mentioned perchlorethylene is added with an appropriate organic substance as a stabilizer, but as described above, the amount of the stabilizer becomes small at the time of decontamination of perchlorethylene itself, and if it is used as it is, the metal is damaged. It has a drawback. Further, the above-mentioned perchlorethylene is generally inferior in stability to electromagnetic waves. Perchlorethylene is oxidized by ultraviolet rays and transformed into trichloroacetyl chloride. Even if it is exposed to sunlight for a long time, it is hydrolyzed and converted into trichloroacetic acid and hydrochloric acid.
Therefore, there is a risk of being changed by α rays, β rays, γ rays, etc. emitted from radioactive contaminants. The present invention has been made to solve various problems as described above,
The purpose is that the decontamination ability of radioactive is much higher than the decontamination method of the prior art, does not cause significant pollution, and also in the case of decontamination of the decontamination agent itself during the decontamination process, the power consumption is The decontamination agent itself is much less efficient than the prior art, and therefore has no obstacle to decontamination of the decontamination agent itself, and it is relatively stable to decontamination against radiation generated from radioactive contaminants. A method and apparatus for decontaminating radioactive pollutants.

[0006]

The present invention which achieves the above object is described as follows. The radioactive contaminants are washed with a methylene chloride solution to remove the deposits on the surface of the radioactive contaminants for decontamination, The decontaminated radioactive contaminants are further decontaminated with a chelate solution, while the methylene chloride solution containing the deposits is filtered to remove the deposits, and the filtered methylene chloride solution is distilled and Decontamination of the methylene chloride solution itself by separating the adhering substances contained in the solution, and using the decontaminated methylene chloride solution for washing radioactive contaminants. Decontamination of radioactive contaminants with methylene chloride. Is the way.

Further, radioactive contaminants are contained in a methylene chloride solution, the methylene chloride solution is impregnated into the deposits on the surface of the contaminants, the contaminants are washed with methylene chloride, and the washed contaminants Is further decontaminated with a chelate solution, while the methylene chloride solution containing the deposits is filtered to remove the deposits, the filtered methylene chloride solution is distilled, and the deposits dissolved to contain the deposits are removed. A method for decontaminating radioactive contaminants with methylene chloride, characterized in that the methylene chloride solution itself is separated and decontaminated, and the decontaminated methylene chloride solution is used for washing radioactive contaminants. Further, the washing is a decontamination method using methylene chloride for the radioactive contaminant, which is an impact with methylene chloride. The bombardment may be carried out in air or in a solution of methylene chloride. The radioactive contaminant is a method for decontaminating radioactive contaminants with methylene chloride, which has been previously sandblasted or shot blasted. Next, a decontamination apparatus using methylene chloride of the present invention will be described. It is the same as a distillation apparatus between a decontamination chamber and a pipe connected to the decontamination chamber, between a filter and a pipe connected to the filter. A decontamination device using methylene chloride for radioactive contaminants, characterized in that a packing formed of perfluoroelastomer is provided between the pipe connected to the distillation device and the pipe connected to the pump. is there.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, reference numeral 1 is a decontamination chamber, in which a nozzle 2 is provided in a closed chamber, and the nozzle 2 is provided toward a radioactive contaminant 3. Radioactive pollutant 3
Generally speaking, many devices in a nuclear power plant are usually coated with a paint using an epoxy resin, and the contaminant 3 shown in the figure is a layer of the epoxy resin paint deposited on the metal 4 as the deposit 5. The case is shown. Reference numeral 6 denotes a support member for the contaminant 3 provided in the decontamination chamber 1. Further, 7 is a methylene chloride solution jetted from the nozzle 2, 8 is a communicating passage, 9 is a high pressure pump, and 10 is an opening / closing device. Further, 11 is a passage leading to the adsorption device 12 using activated carbon, and 13 is a filter, which is the decontamination chamber 1
The tank 1 is connected to the bottom and has an outlet 14 for deposits.
It is connected to 5.

The decontamination chamber 1 may be formed as shown in FIG. In the apparatus shown in FIG. 3, the nozzle is provided in the methylene chloride solution 7, and the impact of the methylene chloride solution 7 on the contaminant 3 is performed in the solution of the methylene chloride solution 7. Figure 1
In the case of the decontamination chamber 1 shown in (1), the impact with the methylene chloride solution 7 is performed in the air. Next, in the present invention, the methylene chloride solution may be immediately bombarded with the contaminant 3 as described above, but it is normally carried out as follows. That is, FIG.
As shown in, the radioactive contaminant 3 is previously dipped in the methylene chloride solution 7 in the container 16.

Then, the deposit 5 is impregnated and swells in the case of a paint using an epoxy resin. In this state in which the deposit 5 is swollen and easily peeled off, the contaminant 3 is supported by the support member 6, and the methylene chloride solution 7 is impacted by the nozzle 2. Next, 13 is a filter as described above, which filters the methylene chloride solution 7 containing the deposit 5 and separates the deposit 5 from the outlet 14 into the tank 15. ing. Reference numeral 17 indicates a pump. Next, 18 is a distillation apparatus for distilling the methylene chloride solution 7 filtered by the filter 13. The methylene chloride solution 7 is distilled in the distillation apparatus 18 to decontaminate the methylene chloride solution 7 itself. 19 is a distillation chamber, 20 is a heater, 21 is a cooling device,
22 is a fin, 23 is a drip collecting plate, and 24 is a second tank. A cooler 25 cools the adsorber 12 when adsorbing the gas.

Although the adsorption device 12 is heated at the time of desorption, the heater used therefor is not shown. At that time, a carrier air heated by a device (not shown) is supplied and desorbed, and the carrier air is liquefied by cooling to a temperature below the boiling point of the gas in the liquefying device 26,
Be recovered. As such an apparatus, as an example, the adsorption apparatus of the invention (Patent application No. 76089 of 1991) previously filed and disclosed by the applicant of the present invention was used. At the time of the liquefaction, a part of the gas that has escaped the liquefaction is cooled to a temperature below the freezing point of the gas by a device (not shown) to be solidified, and the solidified gas is heated and liquefied and recovered. In this way, the gas is completely recovered. Then, as described above, the methylene chloride solution recovered by using an apparatus not shown together is also decontaminated by the distillation apparatus 18,
A high pressure pump 9 is used to feed the second tank 24 to the nozzle 2 of the decontamination chamber 1. Reference numeral 27 is a blower, and 28 is a discharge passage for clean air.

Next, the apparatus 29 shown in FIG. 4 is a decontamination apparatus using a chelate solution 30, and the contaminant 3 decontaminated in the decontamination chamber 1 is further decontaminated by using this decontamination apparatus 29. To dye. Reference numeral 31 denotes an inlet of the chelate solution, and 32 denotes an outlet thereof, so that the chelate solution 30 can be constantly circulated. Reference numeral 33 denotes an ultrasonic vibrating device, by which the chelate liquid 30 can be vibrated. The method of this embodiment using the above apparatus will be described. First, the radioactively contaminated object 3 is immersed in a methylene chloride solution 7 as shown in FIG. This object 3 is measured by a Geiger counter as an example, and is 2000C.
It was PM (Count Per Minute). This contaminant 3
As described above, the paint layer using the epoxy resin is the attached matter 5
As a result, the deposit 5 was impregnated and swollen into the shape of a jellyfish due to the immersion. The immersion time is, for example, about 20 minutes. Next, this contaminant 3 was taken out and washed by impacting it with a jet of methylene chloride solution 7 in the decontamination chamber 1 as shown in FIG. The impact may be, for example, about 5 minutes, and the coating layer swollen by the impact was peeled off. It should be noted that such an operation has substantially the same effect even if it is carried out in the methylene chloride solution 7 as shown in FIG. The radioactivity of the contaminant 3 after the washing was 50 CPM. The radioactive contaminants may be previously sandblasted or shot blasted before being washed with methylene chloride.

Next, the above-mentioned object is the chelate solution 3 shown in FIG.
Ultrasonic cleaning was performed with 0. The chelate solution 30
Was washed by adding a surfactant and circulating it to a tank (not shown). After this cleaning, rinse with fresh water was performed. After the cleaning, the contaminant 3 was measured and found to be 0 CPM. On the other hand, in the methylene chloride solution 7 discharged from the decontamination chamber 1, the deposits 5 are separated by filtration in the filter 13, pass through the tank 15 and the distillation apparatus 1
8, and the methylene chloride solution 7 itself is decontaminated by this, and the methylene chloride solution 7 itself is decontaminated to 0 CPM, which is supplied to the nozzle 2 via the second tank 24 and the high-pressure pump 9, and the following operations are repeated.

Next, using the fluorohydrocarbon, perchlorethylene and other chlorine-based solvents shown in the above-mentioned conventional example, and the methylene chloride solution 7 of the present invention, impregnation, swelling and swelling of the deposit 5 as described above are carried out. When the decontamination effects of decontamination in the decontamination room 1 were compared, the results are shown in Table 1 below.

[Table 1]

As shown in Table 1 above, methylene chloride has a far superior decontamination effect against the above-mentioned conventional fluorocarbons, perchlorethylene, and other chlorine-based solvents. It is clear. The toxicity of methylene chloride is the lowest in chlorine-based solvents, and the permissible concentration in air is 500 ppm, which is five times that of perchlorethylene. Further, methylene chloride has a boiling point of 40 ° C. and 4 ° C., which is extremely low. Therefore, power consumption during decontamination of the solvent itself by distillation can be extremely low. Further, methylene chloride has the most stable molecular structure in a chlorine-based solvent, and therefore, there is no fear of alteration of perchlorethylene due to heating and cooling during distillation.
Further, since there is no risk of deterioration such as perchlorethylene caused by ultraviolet rays and sun rays, it can be expected that there is no fear of deterioration due to radiation emitted by contaminants.

Next, in general, it has been practically difficult to use a methylene chloride solution as a decontamination device. The reason is that there was no packing that was insoluble in the methylene chloride solution and had little loss of elasticity upon irradiation with radiation. Therefore, the inventor of the present invention found a special packing satisfying the above condition and solved it by using it. It is a packing formed of perfluoroelastomer, and is an elastomer manufactured and sold by DuPont in the United States and having a trade name of Kalrez. By using a packing made of this perfluoroelastomer and also for a valve of a pump or the like, methylene chloride can be used, whereby an excellent decontamination device can be obtained. In FIG. 1, reference numeral 34 denotes packing made of the above-mentioned perfluoroelastomer, as shown in the drawing, between the decontamination chamber 1 and the pipe 35, the filter 13 and the pipe 3.
5, between the tank 15 and the pipe 35, the distillation device 18
And the pipe 35, between the second tank 24 and the pipe 35,
And between the pump 9 and the pipe 35. Although not shown, the valve of the pump 9 and the like are also provided. By forming in this way, various devices can be connected to the pipe 35.
The interior of these pipes 35 can be easily decontaminated. The perfluoroelastomer is practically insoluble in methylene chloride and has no change in elasticity. Further, as shown in FIG. 5, the retention of stretchability against radiation is excellent. Figure 5
The ones shown in Figure 2 show the results of experiments conducted with gamma rays, which are far superior to those of Viton.

[0017]

As described above, the present invention can provide a decontamination method and a decontamination apparatus having a decontamination ability far superior to those of the prior art methods. Further, it does not cause significant pollution as in the method using fluorinated hydrocarbon, perchlorethylene or the like. Further, decontamination of the decontamination agent itself can be performed with much lower power consumption than that of the above-mentioned prior art, and high efficiency can be brought about. Further, the molecular structure is much more stable and does not change with respect to heating and cooling during the decontamination of the decontaminating agent itself, as compared with the above-mentioned prior art perchlorethylene. Further, since there is very little risk of deterioration due to ultraviolet rays such as perchlorethylene, sunlight, etc., it can be expected that there is little risk of deterioration due to the radiation caused by the contaminants. Also, by using a device formed of perfluoroelastomer, which is provided with a packing which does not dissolve in methylene chloride and whose loss of elasticity by radiation is small,
For the first time, methylene chloride can be used for decontamination of radioactivity. Further, since the perfluoroelastomer has high durability against radiation as described above, maintenance of the device can be facilitated.

[Brief description of drawings]

FIG. 1 is a view showing an example of the present invention and schematically showing an apparatus used in a method for decontaminating radioactive contaminants with methylene chloride.

FIG. 2 is a diagram showing a step before the step shown in FIG.

FIG. 3 is a diagram showing another embodiment of a part of the apparatus shown in FIG.

FIG. 4 is a diagram showing a step that follows the step performed by the apparatus shown in FIG.

FIG. 5 shows a perfluoroelastomer used in the present invention,
It is a graph which shows the elongation retention rate with respect to a radiation.

[Explanation of symbols]

 1 Decontamination room 2 Nozzle 3 Radioactive contaminants 7 Methylene chloride solution 13 Filter 18 Distiller 30 Chelate solution

Claims (9)

[Claims] 1. The radioactive contaminants are washed with a methylene chloride solution to remove the debris on the surface of the radioactive contaminants for decontamination, and the methylene chloride solution containing the debris is filtered to remove the deposits. The methylene chloride solution that has been removed and filtered is distilled, the deposits dissolved and contained by the distillation are separated to decontaminate the methylene chloride solution itself, and the decontaminated methylene chloride solution is washed with radioactive contaminants. A method for decontaminating radioactive pollutants with methylene chloride, which is used for. 2. A radioactive contaminant is washed with a methylene chloride solution to remove decontamination by removing deposits on the surface of the radioactive contaminant, and the decontaminated radioactive contaminant is further decontaminated with a chelate solution. The methylene chloride solution containing the deposits is filtered to remove the deposits, the filtered methylene chloride solution is distilled, and the deposits dissolved and contained by the distillation are separated to remove the methylene chloride solution itself. A method for decontaminating radioactive contaminants with methylene chloride, which comprises using the dyed and decontaminated methylene chloride solution for washing radioactive contaminants. 3. A radioactive contaminant is contained in a methylene chloride solution, the methylene chloride solution is impregnated into the deposit on the surface of the contaminant, and the contaminant is washed with the methylene chloride solution to obtain the radioactive contaminant. Decontamination is performed by removing the deposits on the surface of the above, the methylene chloride solution containing the deposits is filtered to remove the deposits, and the filtered methylene chloride solution is distilled and dissolved by the distillation. A method for decontaminating radioactive contaminants with methylene chloride, characterized in that the deposits are separated to decontaminate the methylene chloride solution itself, and the decontaminated methylene chloride solution is used for washing radioactive contaminants. 4. A radioactive contaminant is contained in a methylene chloride solution, the methylene chloride solution is impregnated into the deposit on the surface of the contaminant, and the contaminant is washed with the methylene chloride solution, and the washed contaminant is obtained. The product is further decontaminated with a chelate solution, while the methylene chloride solution containing the deposit is filtered to remove the deposit, the filtered methylene chloride solution is distilled, and the deposit is dissolved to contain the deposit. A method for decontaminating radioactive contaminants with methylene chloride, characterized in that the methylene chloride solution itself is decontaminated by separating the methylene chloride solution and the decontaminated methylene chloride solution is used for washing radioactive contaminants. 5. The method for decontaminating radioactive contaminants with methylene chloride according to claim 1, 2, 3 or 4, wherein the washing is impact with methylene chloride. 6. The method for decontaminating radioactive contaminants with methylene chloride according to claim 5, wherein the impact is performed in air. 7. The method for decontaminating radioactive contaminants with methylene chloride according to claim 5, wherein the impact is carried out in a methylene chloride solution. 8. The method for decontaminating radioactive contaminants with methylene chloride according to claim 1, 2, 3 or 4, wherein the radioactive contaminants have been previously sandblasted or shot blasted. 9. A decontamination chamber and a pipe connected to the decontamination chamber, a filter and a pipe connected to the filter, a distillation device and a pipe connected to the distillation device, and a pump and a pump. A decontamination device for radioactive contaminants using methylene chloride, characterized in that packings made of perfluoroelastomer are provided between the pump and a pipe connected to the pump.