JPH0434397A - Decontamination method and device for metal-made body contaminated by radioactivity and materials used for decontamination of contaminated body - Google Patents

Abstract

PURPOSE:To effectively decontaminate radioactivity by opposing an electrode to a metal-made body contaminated by the radioactivity through electrolyte to make currents flow between them so as to electrolyze. CONSTITUTION:A metal-made body 3 contaminated by radioactivity is disposed oppositely to an electrode 4 through an electrolyte 2, and the cathode of direct current power supply 5 or an electrode of alternating current power supply is connected to the metal-made body 3 to connect the cathode 6 of the direct current power supply 5 or the other electrode of the alternating power supply to the electrode 4. In addition, shot blast or sand blast is performed on the metal-made body 3 contaminated by the radioactivity to wash by the use of an organic solvent and the washed metal-made body 3 is disposed oppositely to the electrode 4 through the electrolyte 2. The cathode 6 of the direct current power supply 5 or the electrode of the alternating current power supply is connected to the metal-made body 3 and the cathode 6 of the direct current power supply 5 or the other electrode of the alternating current power supply is set on the electrode 4.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a decontamination method and a decontamination device for metal objects contaminated with radioactivity, which occur in nuclear power plants, etc. This article relates to a method and equipment for decontaminating materials used to decontaminate objects.

[Prior art] In the past, nuclear power plants, etc., were loaded with metal objects that were contaminated with radioactivity as the operation progressed! or its parts, etc.

These devices or parts are generated as devices or parts that are replaced or discarded during periodic inspections or overall maintenance of the devices.

Alternatively, the parts may not be replaced, but the surface of the device may need to be repainted.

The degree of contamination of these contaminated metal objects is often outside the range of safety regulations regarding radioactivity, in which case large objects are cut into pieces, and small objects are left in place. It is stored in a drum can in the shape of , and is usually stored in a waste metal or the like, or it is stored in a storage facility located in an area far away from the committee and where there are no residents nearby, and is stored or disposed of.

Note that in this invention, the above-mentioned storage and disposal are unified into "disposal" for convenience of explanation.

[Problem to be solved by the invention]

However, the number of metal objects contaminated with radioactivity as described above increases over the years due to the operation of nuclear power plants, etc., and the number of objects gradually increases.Therefore, there is a shortage of places to dispose of them, and as a result, new disposal sites are required. When a new disposal site is selected, a protest movement occurs from the local residents of that location, causing social problems.This invention was made to solve these problems, and its purpose is to solve the above problems. Metal objects contaminated with radioactivity, such as metal objects, can be decontaminated to levels below the safety regulations, and therefore can be handled in the same way as general industrial waste, reducing the area of the disposal site. To provide a decontamination method and decontamination device for metal objects contaminated with radioactivity, which can greatly reduce the amount of metal objects contaminated with radioactivity, and for the same purpose, to decontaminate objects contaminated with radioactivity. The object of the present invention is to provide a decontamination method and decontamination equipment for materials used in

It should be noted that the present invention has the above-mentioned purpose, but is not capable of removing radioactivity from objects such as all equipment parts in nuclear power generation equipment, etc. Even the material itself is radioactive. Without this, decontamination of radioactivity is impossible. However, the filling equipment and equipment parts outside the reactor body are different from this, and most of them can be decontaminated.

As mentioned above, during overhauls or periodic inspections of the filling equipment, most of the equipment, parts, etc. that are discarded are located outside the reactor body and can be decontaminated.

Therefore, decontaminating such equipment, parts, etc. helps to greatly reduce the area of the disposal site.

[Means for Solving the Problems] Regarding this invention which achieves the above object, first we will describe a method for decontaminating metal objects contaminated with radioactivity. The anode of the DC power supply or one pole of the AC power supply is connected to the nuclear metal object, and the cathode of the DC power supply or the fl! of the AC power supply is connected to the electrode. ! This is a method of decontaminating metal objects contaminated with radioactivity, which is characterized by connecting poles.

Also, shot blasting or sandblasting is applied to a metal object contaminated with radioactivity, and the shot blasted or sandblasted metal object is cleaned using an organic solvent, and the cleaned metal object is is positioned corresponding to the electrode via an electrolyte, the anode of the DC power supply or one pole of the AC power supply is connected to the metal object, and the @ pole of the DC power supply or the other pole of the AC power supply is connected to the electrode. This is a method of decontaminating metal objects contaminated with radioactivity, which is characterized by connecting the objects.

In addition, in the above method, cleaning of the metal object with an organic solvent is omitted, and after sandblasting or shot blasting, the metal object is placed in the electrolytic liquid bath,
The treatment may be performed as described above, and the present invention also includes such a P4 case.

Next, we will talk about decontamination equipment for metal objects.
A liquid tank containing an electrolytic solution: an electrode provided in the liquid tank; an electrolytic solution contained in the liquid tank; a DC or AC power source; and a radiation shielding wall provided outside the liquid tank. This is a decontamination device for metal objects contaminated with radioactivity.

Also, a liquid tank containing an electrolyte; an electrode provided in the liquid tank; an electrolyte contained in the liquid tank; a DC or AC power supply;
A decontamination device consisting of a radiation shielding wall provided outside the liquid tank; characterized in that it consists of a shot blasting device or a sandblasting device that is combined with the decontamination device and provided upstream of the decontamination device. This is a decontamination device for metal objects contaminated with radioactivity.

Next, we will discuss the method of decontaminating materials used in this invention to decontaminate objects contaminated with radioactivity.It is by using an electrolyte to remove the metal grid of shot blasting contaminated with radioactivity! Connect the anode of the DC power source or one pole of the AC power source to the metal grid.

A method for decontaminating materials used for decontaminating objects contaminated with radioactivity, characterized in that the cathode of the DC power supply or the other pole of the AC power supply is connected to the electrode. Regarding the device, it includes: a liquid tank containing an electrolytic solution; an electrode provided in the liquid tank; a member for holding a shot blast grid provided in a position corresponding to the electrode in the liquid tank;
This is a decontamination device for materials used in the decontamination of radioactively contaminated 11IJ body, characterized by comprising a DC or AC power supply; a radioactivity shielding wall provided outside the liquid tank.

[Example] In FIG. 1, 1 is a liquid tank, which is made of synthetic resin, for example. 2 is an electrolytic solution contained in the liquid f*1, which is formed, for example, from a saline solution.

It goes without saying that this electrolytic solution may be formed from any other suitable known electrolytic solution using an acid, an alkali, etc., and as another example, an aqueous solution of sulfuric acid was used.

Since this electrolytic solution is used to electrolyze metal contaminated with radioactivity, it is sufficient to use only one solution that can dissolve the metal.

3 is a metal object that has been contaminated by radioactivity and has been worn by a shopper. For example, the surface of an iron part is partially covered with dust [adhered to it by burnt oil, etc., and is strongly adhered to it]. It is something. Note that this does not cover the entire surface of the metal piece, but only partially adheres to it. Next, 4 is an electrode, for example a copper wire mesh was used. However, this may be a plate-shaped body. 5 is a DC tt source, and the shadow f! of this power source 5 is 5. 6 is @f! 4, positive 111i7 was connected to the radioactively contaminated metal object 3. Note that 8 is a radiation shielding wall, which is made of concrete, for example. 9 indicates a switch. Note that an AC power source may be used for the above [+5]. This is because electrolysis can also be performed using an AC power source.

The metal object 3 had a layer 1 of 800 C, P, M (count verminite) as measured by Geiger Calendar.

Describing the above device for use with cattle, first the switch 9 is closed in the same figure. Then, the metal object 3 becomes positive tW.
! Therefore, the electrode 4 becomes a negative electrode, and the surface of the metal object 3 is dissolved in the electrolytic solution 2. That is, electrolysis is performed.

As a result, the metal object 3 is contaminated with radioactivity on the surface,
Dust and the like that have been fixed by oil and the like are peeled off into the electrolytic solution 2 together with the metal.

Next, open the switch 9, remove the metal object 3 from the anode 7, take it out from the electrolytic solution 2, and wash it with water. After washing with water, the object 3 was measured with a Geiger counter.
, +4.

Note that when the power source 5 is an AC power source, OC, P, and M are obtained by electrolyzing the electrolytic solution using a sulfuric acid water temperature source, for example.

Object 3 was no longer within the range of safety regulations regarding radioactivity due to the decontamination, so it was taken outside the nuclear power plant, etc., and melted in an electric furnace like general industrial waste.
Recycled as a metal material.

In the apparatus shown in FIG. 1, the object 3 may be placed upwardly in the electrolytic solution 2, and the pole 4 may be placed downwardly in the electrolytic solution 2. By doing so, the electrolysis is further improved. done effectively.

This also applies to the electrolysis of shot gelatin grit, which will be described later. Although not shown in the drawings, the electrolytic solution used in these electrolysis was filtered and purified using an ion exchange resin.

Further, after electrolyzing the metal object 3 in the apparatus shown in FIG.
Brushing the surface allows for more effective decontamination.

Next, in FIG. 2, members having the same reference numerals as in FIG. 1 have the same names and perform the same functions.

10 is a holding member for the grid of shot blasting;
- As an example, a net made of synthetic resin was used. Although detailed illustration of this net is omitted, it is formed into a box shape as shown in the figure using a skeleton member made of synthetic resin. This box-shaped net holding member 10 houses an iron grid 33 that has been contaminated with radioactivity due to shot blasting as described below, and this grid 33 is made of a conductive material such as metal or carbon. 9a is connected.

The apparatus shown in FIG. 1 also operates in the same manner as the apparatus shown in FIG. The radioactive substance adhering to the surface of the electrolyte 33 is peeled off into the electrolytic solution 2.

Regarding the decontamination of the grid 33, shot blasting by the grid 33 and cleaning of the grid 33 will be performed, so the shot blasting and cleaning will be explained.
Decontamination of the grid 33 by electrolysis will be described later.

Next, what is shown in FIG. 3 is a shot blasting device that is used to blast metal objects contaminated with radioactivity.

This yacht blasting may also be performed using sandblasting.

However, when decontaminating the grid 33, shot blasting using a metal grid is performed.

The grid 33 is made of iron and has a hemispherical shape, for example. However, this may be a cut wire or the like.

In the figure, reference numeral 11 denotes an air compressor, and the compressed air produced here is stored in an air tank 12, and by opening the valve 13 of the air tank 12, the compressed air is
By opening the valve I5 of the grit 33, the nozzle 16
It is ejected from. 17 is a deletion chamber, and 18 is a communication pipe.

Reference numeral 19 denotes an ejector type negative pressure generating device, which is communicated with the air tank 12 and is activated by opening the valve 20. And this negative pressure generator f19
is connected to a suction port 23 via a filter chamber 21 and a separation device 22. 24 is a storage box for radioactively contaminated waste powder. The separating device 22 is composed of an upper cylinder 25, a middle cylinder 26, and a hopper 27.
8 is provided. 29 is a gap. 30 is a vibrating sieve, and 31 is an inlet for a new grid 33.

Further, the upper @ 25 is formed around the discharge tube 32, and its entrance is formed in the tangential direction, and the grid 33 and removed powder etc. sucked in by the suction port 23 are rotated to the middle 112.
6, the removed powder therein hits the reversing part 28, is reversed upward, exits from the discharge 11J32, enters the filter chamber 21, and is stored in the storage box 24. On the other hand, the grid 33 having a large mass rotates near the inner wall surface of the middle cylinder 26 due to centrifugal force.
It enters the hopper 27 through the gap 29 and is then sucked into the grid tank 14. 34 indicates a sub-filter chamber.

Reference numeral 35 denotes a metal object contaminated with radioactivity, whose posture is changed by a gripping device (not shown) so that its entire surface is exposed to the spray of the grid 33.

In this case, the object 35 is, for example, an iron part coated with anti-rust coating. In the rust preventive device, a top coat layer of epoxy resin paint is usually formed on a base coat layer of zinc oxide paint. Metal objects contaminated with radioactivity include external boilers, turbine blades, etc. that have been contaminated with limestone, and painted surging tanks installed for submersion in emergencies. The interior walls, etc. That is, in general, when paint, scale, dust mixed with oil, etc. are attached to the metal surface, it is difficult to decontaminate the metal by wiping it off.

The object 35 was 800 C, P, M as measured by a Geiger counter, as an example.

This same object 35 was exposed to the grid 33 sprayed from the nozzle 16 by the operation of the shot blasting device shown in FIG. 3, and the coating layer on its surface was removed. After the deletion, the radioactivity of object 35 was measured and found to be 120C, P, and H.

Next, this same object 35 is placed in the apparatus shown in FIG.
A metal object 3 was placed at position 1, connected to the anode 7 of the DC power source 5, and the cathode 6 connected to the electrode 4, and the switch 9 was closed to perform electrolysis. Note that the object 3 is a steel product, and the electrolyte 2
is a saline solution. After this electrolysis, the metal object 3 was taken out, washed with water, and dried. Measurements using a Geiger counter were OC, P, and M.

This washing water was purified using an ion exchange resin (not shown).

Next, what is shown in FIG. 4 is a cleaning device using an organic solvent. This apparatus is used when, after the shot blasting, the object is not immediately subjected to electrolysis as described above, but the object is washed with an organic solvent, and after this washing, electrolysis is performed.

This is done when there is strong adhesion of paint, etc.

In the figure, 37 is a cleaning tank, 38 is an ultrasonic vibration device,
35 is the metal object subjected to the shot blasting, 3
9 is an organic solvent - methylene chloride was used as an example. However, in addition to this, chlorine-based organic solvents such as trichloroethane, fluorocarbon-based solvents, and other general organic solvents may be used. The radioactivity of the object 35 was 26C,P,M.

In addition to using an ultrasonic cleaning device, the above self-cleaning device also used a method of cleaning with a rotating brush while spraying an organic solvent (for example, methyl erulgetone), although not shown.

Next, the cleaned metal object 35 was subjected to electrolysis as described above, and after the electrolysis, it was washed with water. The objects 35 after being washed with water were measured at locations OC, P, and M.

Next, what is shown in FIG. 5 is a device for decontaminating the grid 33 used for the decontamination, and in the figure, 381
For example, a screen drum 39 made of stainless steel is rotatably provided and connected to a drive device 40. 41 is the grid 33 used for decontamination
42 is a cleaning liquid injection device.

The cleaning device 38 is connected to an adsorption device 48 using activated carbon. Further, in the figure, 49 indicates a communicating pipe.

Further, 50 is a filtration device, and although detailed illustration is omitted,
- For example, the removal powder mixed with the cleaning liquid is sandwiched between two filter cloths and pressure is applied from the outside. Reference numeral 51 indicates a grid outlet, 52 indicates a discharge passage for removed powder, and 5
4 is an organic solvent as a cleaning liquid; methylene chloride was used as an example. In addition, the cleaning liquid 54 includes:
Similarly to the above, there is no problem in using fluorocarbon solvents, chlorine-based organic solvents, and other general organic solvents as appropriate.

Next, 55 is a tank, 56 is a pump, and 57 is a purification device.

The device 57 includes a heater 58, a cooling device 59, and a recovery passage 60.
The methylene chloride is heated, vaporized, brought into contact with a cooling device 59 to be liquefied, and dropped onto a recovery passageway 60 to be recovered in a tank 61. 62 is a refrigerator, and 63 is a pump.

Next, the adsorption device 48 will be described.
is a device using activated carbon, and a normal, known activated carbon adsorption device may be used as appropriate.
A gas adsorption device using activated carbon described in No. 6089) was used. To give an overview of this adsorption device, although detailed illustrations are omitted, the activated carbon in the activated carbon tank is cooled by a cooler 64 during gas adsorption, and methylene chloride gas is adsorbed in this state. When desorbing the gas, the activated carbon is heated by a heater (not shown), and in this state, heated carrier air is supplied, and the activated carbon is desorbed by the carrier air. The carrier air containing the gas is cooled to a temperature below the boiling point of the pre-E gas in a liquefaction device (not shown), liquefied, and recovered. Part of the gas that has escaped liquefaction in the forked stage is cooled below its freezing point and solidified. The solidified gas is heated, liquefied, and recovered. In this way, the gas is almost completely recovered. The methylene chloride recovered as described above is then refluxed to the purification device 57 by the pump 65. Note that 66 and 67 are blowers, and 68 is a clean air discharge passage.

Next, the operation of the apparatus shown in FIG. 5 will be described. The grid 33 on which the radioactively contaminated removal powder has adhered is supplied to the cleaning device 38 by the supply device 41, and is sprayed with methylene chloride from the spray device 42. , and is cleaned as the screen drum 39 rotates, and advances in the direction of arrow A3g in FIG. 3 while losing the removed powder. In this case, methylene chloride dissolves epoxy resin paints, zinc oxide paints, etc. well. The cleaning liquid discharged from the cleaning device 38 is filtered by the filtering device 50, separated from the removed powder, and enters the tank 55, and then sent to the purification device 57 to be purified. Ru. In this case, purification is performed using vaporization, and as a result, the slightly contained powder is completely removed. Therefore, the purified methylene chlorides were OC, P, and M. The purified methylene chloride is then sent to the cleaning device 38.

In this case, since the organic solvent has a low heat of vaporization, purification is extremely easy and effective.

In the case of cleaning the radioactively contaminated metal object with an organic solvent, the organic solvent used for cleaning was purified using the purification device 57 described above.

Next, the grid 33 that has passed through the cleaning device 38 is dried by a drying device (not shown), exits from the discharge port 51, and is stored in a tank (not shown).

Meanwhile, air containing gas is suctioned by a gas adsorption device 48 using activated carbon, which is provided in communication with the cleaning device 38, and the adsorbed gas is liquefied and sent to the purification device 5.
7 is refluxed. The grids accommodated in the tank were, for example, 30C, P, and M.

As described above, this grid is housed in the holding member 10 of the electrolytic cell shown in FIG. Electrolyzed in electrolyte 2. The grids 33 washed with water and dried after electrolysis were OC, P, and M.

The electrolytic solution used in this electrolysis was purified using an ion exchange resin (not shown) as described above.

[Effects of the Invention] The present invention is configured as described above, and effectively eliminates the radiation by connecting an electrode to a radioactively contaminated metal object via an electrolytic solution and electrolyzing the metal object by passing current between the two. It is possible to decontaminate the facility. In addition, by subjecting metal objects contaminated with radioactivity to shot blasting or sandblasting and then electrolyzing them, it is possible to effectively decontaminate them. Furthermore, an electrolytic cell with a shielding wall provided on the outside can safely decontaminate metal objects contaminated with radioactivity. In addition, by positioning an electrode on a radioactively contaminated metal grid of shot blasting through an electrolytic solution and electrolyzing the grid by supplying electricity to both, the grid can be effectively decontaminated. . Further, the electrolytic cell provided with the grid holding member can provide a device that can effectively decontaminate the grid.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention; FIG. 1 is an exploded perspective view of a decontamination device for metal objects contaminated with radioactivity, and FIG. 2 is an exploded perspective view of an apparatus for decontaminating metal objects contaminated with radioactivity. Figure 3 is an exploded perspective view of the decontamination equipment for radioactively contaminated metal objects, Figure 4 is a cross-section of the decontamination equipment different from Figure 3. FIG. 5 is a diagram schematically showing a material decontamination device used for radioactivity decontamination. 1...Liquid tank 2...Electrolyte 3...Metal object contaminated with radioactivity 4...Electrode 5...DC power source 6...Cathode 7...Anode 8... shielding wall

Claims (1)

[Claims] 1. A metal object contaminated with radioactivity is placed in correspondence with an electrode via an electrolyte, and the anode of a DC power source or one pole of an AC power source is connected to the metal object. A method for decontaminating a metal object contaminated with radioactivity, characterized in that the cathode of the DC power supply or the other pole of the AC power supply is connected to the electrode. 2. Shot blasting or sandblasting is performed on a metal object contaminated with radioactivity, and positioning the shot blasted or sandblasted metal object in correspondence with an electrode via an electrolyte, The anode of the DC power supply or one pole of the AC power supply is connected to the object made of metal, and the cathode of the DC power supply or the other pole of the AC power supply is connected to the electrode. How to decontaminate objects. 3. shot blasting or sandblasting a radioactively contaminated metal object, cleaning the shot blasted or sandblasted metal object using an organic solvent, and cleaning the cleaned metal object is positioned corresponding to the electrode via an electrolyte, the anode of the DC power supply or one pole of the AC power supply is connected to the metal object, and the cathode of the DC power supply or the other pole of the AC power supply is connected to the electrode. A method for decontaminating metal objects contaminated with radioactivity, characterized by: 4. A liquid tank containing an electrolytic solution; an electrode provided in the liquid tank; an electrolytic solution contained in the liquid tank; a DC or AC power supply;
A decontamination device for metal objects contaminated with radioactivity, comprising a radioactivity shielding wall provided outside the liquid tank. 5. A liquid tank containing an electrolyte; electrodes provided in the liquid tank; an electrolyte contained in the liquid tank; a DC or AC power supply;
A decontamination device consisting of a radioactivity shielding wall provided outside the liquid tank; and a shot blasting device or a sandblasting device provided upstream of the decontamination device in combination with the decontamination device. A decontamination device 6 for metal objects contaminated with radioactivity, a metal grid of a shot blast contaminated with radioactivity is positioned in correspondence with an electrode via an electrolyte,
Contaminated with radioactivity, characterized in that an anode of a DC power supply or one pole of an AC power supply is connected to the metal grid, and a cathode of the DC power supply or the other pole of the AC power supply is connected to the electrode. Methods for decontaminating materials used to decontaminate objects. 7. A liquid tank containing an electrolytic solution; an electrode provided in the liquid tank; a holding member for a shot blasting grid provided in a position corresponding to the electrode in the liquid tank; a DC or AC power source; A decontamination device for materials used for decontaminating objects contaminated with radioactivity, characterized by comprising a radioactivity shielding wall provided outside a liquid tank.