JPH05161885A - Apparatus for decontamination in pipe - Google Patents

Abstract

PURPOSE:To remove mechanically oxides adhered on the inner face of the primary pipeline of a nuclear power plant and to make the inner face of the pipeline smooth. CONSTITUTION:An apparatus removing mechanically oxides contg. radioactive substances adhered on the inner face of a primary pipeline 1 of a nuclear power plant consists of an abrasion mechanism part B having an abrasion part 5 which is brought into contact with the inner face of the pipeline and abrades the inner face and a driving part 6 rotating the abrasion part through an expansion arm 7, and a running mechanism part A having a rotating type nozzle 3 ejecting high pressure water backward, a flexible hose 4 feeding the high pressure water to the backward ejecting nozzle, wheels 8 being brought into contact with the inner face of the pipeline, an expansion arm 8a supporting the wheels and a motor part 9 rotating the wheels and moving the abrasion mechanism part and the backward ejecting nozzle to a position where contamination is to be removed. Therefore, removing of adhered oxides in the pipeline and smoothing of the inner face of the pipeline are efficiently performed and readhesion of oxides is suppressed and waste caused by decontamination is made as small as possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an object pipe having an oxide containing a radionuclide attached to an inner surface of a nuclear plant,
Efficiently removes the adhered oxide and smoothes the inner surface of the target pipe.Specifically speaking, the adhered oxide is removed by the rotation of the abrasive that is pressed against the inner surface of the pipe to remove the target surface. The present invention relates to a decontamination device that smoothes and reduces redeposition.

[0002]

2. Description of the Related Art In a nuclear power plant, oxides containing radioactive nuclides such as ⁶⁰ Co and ⁵⁴ Mn are formed in primary system pipes and equipment with the passage of operating time, and the dose rate of the pipes and equipment tends to increase. The figure shows that the dose equivalent received by workers during the operation of nuclear power plants and during regular inspection tends to increase. As one of the countermeasures, there is a decontamination technology that removes the oxide adhering to the inner surfaces of pipes and equipment. The decontamination techniques are classified according to the decontamination target and the purpose, and can be roughly classified into chemical decontamination, mechanical decontamination, and electrochemical decontamination.

For chemical decontamination, as typified by JP-A-53-731, chemicals containing an acid, a reducing agent and a complexing agent as main components are used to chemically dissolve oxides on the surface. To remove. Electrochemical decontamination includes an electrolytic polishing method, and there are the following two types.

One is to utilize the anodic oxidation method, which is to remove the surface oxide by dissolving the surface of the metal base material itself in an electrolyte solution. the other one is,
This is a method for facilitating dissolution of the surface oxide by utilizing cathode reduction.

Both the above chemical decontamination and electrochemical decontamination require the use of a decontamination waste liquid because chemicals are used, and a large amount of waste is generated.

On the other hand, the mechanical decontamination method represented by the high-pressure jet and brush method mechanically removes the adhered oxide, does not use chemicals in particular, is easy to dispose of waste, and produces a large amount. The high-pressure water jet method (Japanese Patent Laid-Open No. 53-122261), which has few advantages, is a general method because it decontaminates by removing the surface of the decontamination target with high-pressure water. Usually, it is carried out at a pressure of 100 to 300 kg / cm ² , but it is the current situation that a large decontamination effect is not obtained. The brush method is a method of rubbing the surface of an object to be decontaminated with a brush, but this method also has a low decontaminating effect because it is difficult to remove oxides adhering to the metal surface. In addition, since the brush method removes oxides with a brush, in order to improve the decontamination effect, it is necessary to replace and use the brush as appropriate, which requires time.

[0007]

The above-mentioned conventional chemical decontamination and electrochemical decontamination can obtain a higher decontamination effect than mechanical decontamination, but a large amount of chemical waste is generated. There's a problem. On the other hand, mechanical decontamination such as the high-pressure jet method and the brush method has no problem that chemical waste is generated, the waste treatment is easy, and the generated amount is small. However, a high decontamination effect has not been achieved yet, and it is necessary to improve the current technology to obtain a high decontamination effect.

[0008] None of the decontamination methods considers the point of reattachment after decontamination, and after decontamination, rapid adhesion and formation of oxides containing radionuclides occurs, and There was a problem that it returned to the dose rate or, depending on the decontamination method, in the worst case it was higher than the dose rate before decontamination. That is, in any decontamination, reattachment of radioactive substances after decontamination becomes a problem, and there is a tendency that the original state is restored within 1 to 2 years after decontamination. In some cases, a phenomenon in which reattachment occurs more rapidly than before decontamination and the amount of deposits increases is also observed. Although all of these phenomena differ depending on the surface condition of the decontaminated object after decontamination and the environment of the reactor water, rapid redeposition tends to occur if the object surface is rough after decontamination.

An object of the present invention is to provide a decontamination device for removing from the surface of an object an oxide containing a radionuclide attached / formed on a pipe in contact with primary cooling water of a nuclear power plant.
An object of the present invention is to provide a decontamination device capable of efficiently removing oxides, reducing the amount of waste, and suppressing reattachment.

[0010]

In order to achieve the above object, the pipe decontamination apparatus of the present invention is an apparatus for mechanically removing oxides containing radioactive substances adhering to the inner surface of the primary piping of a nuclear power plant. In, a polishing mechanism section having a polishing section that abuts the inner surface of the pipe and polishes the inner surface, and a drive section that rotates the polishing section through an expansion / contraction arm, a rotary high-pressure water rear jet nozzle, and the rear jet nozzle. A flexible hose for supplying high-pressure water to the pipe, a wheel in contact with the inner surface of the pipe, a telescopic arm that supports the wheel, and a motor unit that rotates the wheel, and moves the polishing mechanism unit and the rear injection nozzle to the decontamination site. It consists of a traveling mechanism section.

[0011]

According to the present invention, the decontamination device in a pipe is provided with a polishing mechanism part having a polishing part for abutting the inner surface of the pipe and polishing the inner surface, and a drive part for rotating the polishing part through an expanding and contracting arm.
A rotary type high-pressure water rear jet nozzle, a flexible hose for supplying high-pressure water to the rear jet nozzle, a wheel in contact with the inner surface of the pipe, a telescopic arm for supporting the wheel, and a motor unit for rotating the wheel, Since it consists of a polishing mechanism and a traveling mechanism that moves the rear injection nozzle to the decontamination site, it efficiently removes oxides on the inner surface of the pipe and polishes the inner surface of the pipe smoothly. Prevents redeposition of oxides after decontamination.

[0012]

1 and 2 show an embodiment of the pipe decontamination apparatus of the present invention. In these drawings, the pipe decontamination device is inserted into the decontamination target pipe 1 of the actual plant from the valve bonnet opening portion 2. The decontamination device includes a rotary high-pressure water rear injection nozzle 3 at the tip, a flexible hose 4 for supplying high-pressure water from the injection nozzle 3, a polishing mechanism section B for removing and polishing oxides on the inner surface of the target, and a rear side. It is composed of a spraying mechanism 3 and a traveling mechanism A for moving the polishing mechanism B to the decontamination site.

The polishing mechanism section B has a polishing section 5 for removing deposits such as oxides on the inner surface of the pipe 1 and polishing the inner surface. An abrasive is contained in a part or all of the polishing part 5. As the abrasive, silicon carbide, boron carbide, or hard paper in a spherical or flat plate shape is used. A material having a thickness of 3 μm or less is used. The polishing section 5 is supported by the drive section 6 of the polishing mechanism section B via a telescopic arm 7 containing a spring, pressure oil and the like. It is preferable to arrange a plurality of polishing parts 5 at equal intervals in the circumferential direction.
The drive unit 6 is composed of a fixed frame in which a motor is housed, and a rotary frame which is rotatable with respect to the fixed frame and is rotated by the motor. The rotary frame is connected to the polishing unit 5 via the telescopic arm 7. Tell the rotation. The traveling mechanism unit A has wheels 8 which are supported by a motor unit 9 via a telescopic arm 8 a and roll along the inner surface of the pipe 1. A plurality of wheels 8 are arranged at equal intervals in the circumferential direction, and the rotation of the motor 9 is appropriately transmitted via a transmission mechanism.

A valve 11, a high-pressure pump 12, and a flexible hose 4 are sequentially connected to the pure water system pipe 10, one end of the flexible hose 4 is connected to a hose winding device 13 so as to be able to be wound and unwound, and the other end is a motor. The rotating high-pressure water rear injection nozzle 3 via the portion 9 and the flexible connector 16.
However, it may be directly connected to the nozzle 3 without the motor unit 9 and the connecting tool 16.

A control operation panel 15 is connected to the traveling mechanism section A and the polishing mechanism section B via a control cable 14,
It is remotely operated by the control operation panel. Similarly to the control cable 14, the power line is also connected to the traveling mechanism unit A and the polishing mechanism unit B from outside the pipe. The drain pipe 17, the suction pump 18, and the filter 1 are provided in the pipe 1 for discharging the waste liquid.
9 and the pipe 20 are sequentially connected.

In the pipe decontamination device constructed as described above, the water in the pipe 1 is removed before use.
By inserting the valve bonnet opening part 2 into the pipe 1 and then rotating the polishing part 5 in contact with the inner surface of the pipe, the rotation of the polishing part and the effect of the high pressure water from the nozzle 3 are added, and the inner surface of the pipe is attached. The kimono is removed and the inner surface of the pipe is polished smoothly. At that time, high-pressure water is jetted from the rear jet nozzle 3, and the peeled oxide is transferred rearward in the decontamination proceeding direction. The high-pressure water is continuously or intermittently jetted from a nozzle installed at the tip of the decontamination device, and not only has the backward transfer of exfoliated oxides been carried out, but also has the effect of removing the oxides adhering to the inner surface of the pipes, and further high decontamination A dyeing effect can be obtained. The peeling deposits transferred to the rear, that is, peeling oxides, are drain pipe 1
7, guided to the filter 19 via the suction pump 18,
There, it is collected. The treated water that has passed through the filter is discharged to the drain system through the discharge pipe 20. Therefore, no decontamination waste liquid such as chemical decontamination is generated, and only a filter is generated as waste.

As described above, the inner surface of the pipe 1 is polished to have a surface roughness of 3 μm or less. The traveling mechanism unit A advances the nozzle 3 and the polishing mechanism unit B according to the polishing situation.
At this time, since the traveling mechanism section A and the polishing mechanism section B are connected by the flexible connection tool 16, the traveling mechanism section A and the polishing mechanism section B can easily pass through the bent portion or the like of the pipe 1. Further, by adopting the telescopic arms 7 and 8a, the traveling mechanism portion A and the polishing mechanism portion B can be inserted through an opening smaller than the target pipe, and the pipes having different inner diameters can be continuously decontaminated. can do.

In the above-mentioned embodiment, the high-pressure water rear jet nozzle 3 and the polishing mechanism section B are arranged in front of the traveling mechanism section A. However, such arrangement is not always necessary, and they are arranged behind the traveling mechanism section A. You can also do it.

Next, another embodiment of the present invention will be described with reference to FIG. In this embodiment, a small TV camera 21 and an illumination light 22 are mounted on a traveling mechanism section A similar to the traveling mechanism section. The traveling mechanism A, the TV camera 21, and the illumination light 22 are remotely operated from the operation panel 15.

By doing so, the small television camera 2
In No. 1, it is possible to confirm the decontamination state of the inner surface of the pipe at the time of decontamination or after decontamination and the misplacement of decontamination parts, etc., and the reliability of decontamination can be improved. In addition, in the traveling mechanism section A,
A surface roughness measuring device for measuring the inner surface roughness of the pipe can also be mounted, and the decontamination status and the smoothing status of the surface can be grasped.

A comparison of the re-deposition amount after decontamination due to the above decontamination effect and surface roughness is shown below.

FIG. 4 compares the decontamination effect of mechanical polishing according to the present invention with other decontamination techniques, and the decontamination effect of general jet cleaning (150 to 300 kg / cm ² ) is set to 1. It is expressed as a relative value. The decontamination effect was evaluated using a test piece collected from an actual machine. In the case of chemical decontamination, select a dilute decontamination solution that has less effect on the constituent materials and
The decontamination liquid A containing TA (complexing agent) as a main component was used, and the decontamination time was 15 hr and the liquid temperature was 90 ° C. In mechanical polishing, decontamination was performed using spherical silicon carbide as an abrasive.
As a result, with respect to the jet cleaning 1, the chemical decontamination was about 5, and the mechanical polishing was about 8, showing that the decontamination effect of the mechanical polishing is great.

FIG. 5 shows the influence of surface roughness on the adhesion of Co to stainless steel (SUS316). Test pieces with different surface roughness were placed in an autoclave under actual machine conditions, and the adhesion amount after 1000 hours was measured.
If the surface roughness is about 6 μm, the surface roughness is 1.5 μm
Also, as compared with the case of about 3 μm or less, the Co adhesion amount is large, and at 3 μm or less, a large difference is not seen in the Co adhesion amount. That is, after decontamination, the surface roughness should be 3μ.
When it is not more than m, the amount of Co deposited, in other words, the reattachment of radionuclide can be suppressed low, and the decontamination effect can be maintained for a long period of time. Meanwhile, conventional jet cleaning,
In chemical decontamination and the like, the present situation is that the reduction of redeposition after decontamination is not considered so much.

By applying the present invention described above to decontamination of pipes in a nuclear power plant, decontamination can be performed with high efficiency, and reattachment after decontamination can be mitigated, and repairs of equipment, piping, etc. The dose equivalent received by the worker at the time of inspection can be reduced.

[0025]

As described above, according to the present invention,
In an apparatus for mechanically removing oxides containing radioactive substances attached to the inner surface of a primary system piping of a nuclear power plant, a polishing unit that abuts the inner surface of the piping and polishes the inner surface, and the polishing unit is rotated through a telescopic arm. A polishing mechanism section having a drive section, a rotary high-pressure water rear jet nozzle, a flexible hose for supplying high-pressure water to the rear jet nozzle, a wheel in contact with the inner surface of the pipe, a telescopic arm supporting the wheel, and the wheel. Since it has a rotating motor unit and a traveling mechanism unit that moves the polishing mechanism unit and the rear injection nozzle to the decontamination site, it is possible to efficiently and easily remove oxides attached to the inner surface of the piping of the nuclear power plant. It can be removed and the surface of the decontamination object can be smoothed.

Further, when the plant operation is restarted after the decontamination as it is, rapid de-adhesion may occur on the decontamination object. In order to suppress this, there is a method of forming an oxide film on the surface after decontamination and before newly contacting the reactor water, but it is difficult to oxidize the actual equipment pipe in operation. On the other hand, in the present invention, it was found that similar redeposition can be suppressed by smoothing the surface. The present invention is characterized by having a function of smoothing the surface by polishing and having a surface roughness of 3 μm or less. In addition, equipment for inspecting the target system at the time of decontamination and after decontamination can be mounted, and the reliability of decontamination work can be increased. All the above decontamination can be performed by remote control, and the dose equivalent received during decontamination work can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic side view showing an embodiment of a decontamination device of the present invention.

FIG. 2 is a front view of the decontamination device shown in FIG.

FIG. 3 is a schematic side view showing another embodiment of the decontamination device of the present invention.

FIG. 4 is a comparison diagram of decontamination effects of the decontamination apparatus of the present invention for various decontamination techniques.

FIG. 5 is a diagram illustrating the effect of surface roughness on Co adhesion to stainless steel.

[Explanation of symbols]

A ... Traveling mechanism B ... Polishing mechanism 1 ... Piping 3 ... High pressure water rear injection nozzle 4 ... Flexible hose 5 ... Polishing part 6 ... Drive part 7, 8a ... Telescopic arm 8 ... Wheel part 9 ... Motor part 12 ... High pressure pump 13 ... Winding device 21 ... Small TV camera 22 ... Illumination light

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsumi Okazumi 3-1-1 Sachimachi, Hitachi City, Ibaraki Hitachi Ltd. Hitachi Factory (72) Inventor Takao Shimura 3-chome, Hitachi City, Hitachi, Ibaraki Prefecture No. 1 Hitachi Ltd., Hitachi Plant (72) Inventor Shinya Omori 3-1-1, Saiwaicho, Hitachi City, Ibaraki Hitachi Ltd., Hitachi Plant

Claims (4)

[Claims] 1. An apparatus for mechanically removing oxides containing a radioactive substance adhering to an inner surface of a primary system pipe of a nuclear power plant, a polishing unit for abutting the inner surface of the pipe and polishing the inner surface, and an elastic arm for the polishing unit. A polishing mechanism section having a drive section that rotates via a rotary rotary high pressure water rear injection nozzle,
A flexible hose for supplying high-pressure water to the rear injection nozzle, a wheel in contact with the inner surface of the pipe, a telescopic arm supporting the wheel, and a motor section for rotating the wheel, and decontaminating the polishing mechanism section and the rear injection nozzle. An in-pipe decontamination device comprising: a traveling mechanism section for moving to an area, removing oxides on the inner surface of the pipe and smoothing the inner surface of the pipe. 2. The polishing material of the polishing portion is made of one type of silicon carbide, boron carbide or hard paper in the shape of a sphere or a flat plate, and a plurality of polishing portions are arranged in the circumferential direction. The pipe decontamination device according to claim 1. 3. The traveling mechanism can be connected to a polishing mechanism and a rear injection nozzle in front of or behind the traveling mechanism, and a small TV camera for inspecting the decontamination condition and the surface roughness of the inner surface of the pipe are measured. A decontamination device for pipes according to claim 1, wherein a measuring instrument that can be installed can be mounted. 4. The in-pipe decontamination apparatus according to claim 1, wherein the abrasive is an abrasive having an inner surface roughness of the pipe after polishing of 3 μm or less.