JP7088492B2 - Laser decontamination equipment, laser decontamination system and laser decontamination method - Google Patents

Description

The present invention relates to a laser decontamination device, a laser decontamination system, and a laser decontamination method for removing a radioactively contaminated layer by irradiation with a laser beam.

As a field of application of laser, laser decontamination technology for separating and removing the radioactively contaminated layer from the main body, that is, the technology for peeling, melting and evaporating the radioactively contaminated layer by irradiation with a laser beam is known. Has been done. For example, in Patent Document 1, a radioactive substance that has penetrated inside the contaminant T by automatically adjusting the focal position (focal length) of the CW (Continuous Wave) laser beam L1 based on the scanner scanning by the measuring laser beam L2. RI can be removed. In Patent Document 2, the radioactive oxide layer adhering to and deposited on the inner peripheral surface of the pipe is irradiated with the laser light LB for removing the first contaminated layer to decontaminate, and then the laser light for forming the second modified layer is applied. By irradiating LA to form a surface-modified layer such as an oxide film, it is possible to promote the recycling of pipes and the like.

By the way, in recent years, in relation to the problem of restarting and decommissioning nuclear power plants, attention has been paid to decontamination treatment of radioactively contaminated facilities such as storage tanks for reactor cooling water. Such a tank is formed in a large-diameter cylindrical shape having a diameter of more than 10 m, and a paint (for example, tar epoxy resin paint) for enhancing rust-proof and corrosion-proof functions is specified on the inner peripheral wall surface made of stainless steel plate. It is applied in a thickness (for example, 0.1 to 0.2 mm). The surface layer portion of the coating film and the steel plate (for example, the surface thickness inside the coating film is 0.1 to 0.2 mm) becomes a radioactively contaminated layer contaminated with radioactivity due to storage of radioactive substances such as cooling water. Therefore, when decommissioning the reactor, it is necessary to dismantle the tank and remove the radioactive contaminated layer. In addition, when restarting, it may be necessary to remove the radioactive contaminated layer and reapply the paint (see Patent Document 2) in order to restore the rust-preventive and anticorrosive functions.

To remove the radioactively contaminated layer, which generally has a large surface area, a high laser power (eg, maximum power of 2 kW), a wide irradiation range (irradiation area; for example, maximum beam diameter of 50 mm) and a constant focal length (separation distance; for example, 300 mm) and further. It is necessary to secure a high moving speed (for example, 3 m / min) to improve efficiency. However, by adopting these high efficiency means, even with a CW laser with a relatively stable output (see Patent Document 1), the energy density in the beam tends to vary, and the radioactive contaminated layer is removed in a mottled pattern. , Undecontaminated parts may occur (that is, the decontamination accuracy may decrease). Further, in Patent Document 1, the focal length adjustment function based on scanner scanning tends to cause a control delay due to high-speed movement of the laser beam, and fluctuations in the focal length due to rust or corrosion on the coating surface cause variations in energy density in the beam. There is a risk that the decontamination accuracy will be further reduced.

As described above, when removing a radioactively contaminated layer having a large surface area such as a cooling water storage tank, it is difficult to decontaminate with high efficiency and high accuracy even if the techniques disclosed in Patent Documents 1 and 2 are applied. .. Therefore, for example, when the decontamination treatment described in Patent Document 1 is applied to the small pieces after dismantling / cutting the tank one by one, the decontamination treatment requires a long period of time (regeneration treatment is not possible), and the environment is affected. It may lead to adverse effects and an increase in processing costs.

Japanese Patent No. 5610356 Japanese Unexamined Patent Publication No. 8-110396

The subject of the present invention is high efficiency in the radioactively contaminated layer including the surface layer portion and the coating film of the substrate without disassembling and cutting the radioactively contaminated substrate (for example, a large-diameter tubular storage tank for reactor cooling water). It is an object of the present invention to provide a laser decontamination device, a laser decontamination system, and a laser decontamination method capable of decontaminating with high accuracy.

Means for Solving Problems and Effects of Invention

In order to solve the above problems, the laser decontamination apparatus of the present invention is used.
Laser removal that removes (that is, peels, melts, or evaporates) the radioactively contaminated layer that contains at least the coating film applied to the surface of the substrate and the surface layer of the substrate and is contaminated with radioactivity from the main body of the substrate by a laser beam. It ’s a dyeing device,
A laser oscillator that generates a laser beam and
The movable pedestal is arranged so as to be able to move forward and backward with respect to the radioactively contaminated layer, and the movable pedestal is urged toward the laser irradiation direction while maintaining a predetermined separation distance from the surface of the radioactively contaminated layer. With a follow-up movement mechanism that follows the surface of the radioactively contaminated layer,
A decontamination movement mechanism equipped with the follow-up movement mechanism and moving the movable pedestal in a decontamination direction intersecting the laser irradiation direction,
Laser irradiation that is mounted on the movable pedestal so that it can follow the laser irradiation direction and can move in the decontamination direction, and is connected to the laser oscillator via an optical fiber to irradiate the radioactively contaminated layer with a laser beam. Mechanism and
A control unit capable of adjusting at least the output (that is, intensity), focal length, and irradiation range of a laser beam generated by the laser oscillator and emitted from the laser irradiation mechanism is provided.
The control unit generates a CW laser for removing and roughening the radioactive contaminated layer with the laser oscillator and irradiates it from the laser irradiation mechanism, and a pulse for removing the rest of the radioactive contaminated layer. It is characterized by including a switching means for switching to a second mode in which a laser is generated by the laser oscillator and the laser irradiation mechanism irradiates the roughened radioactive contaminated layer.

Further, in order to solve the above problems, the laser decontamination apparatus of the present invention is used.
A radioactively contaminated layer containing at least the coating film applied to the inner peripheral wall surface of the steel sheet constituting the (upright) tubular tank and the surface layer portion of the steel sheet and contaminated with radioactivity is applied from the main body of the steel sheet by a laser beam. A laser decontamination device that removes (ie, peels, melts, or evaporates).
A laser oscillator that generates a laser beam and
The movable pedestal is arranged so as to be able to move forward and backward with respect to the radioactively contaminated layer, and the movable pedestal is urged toward the laser irradiation direction while maintaining a predetermined separation distance from the surface of the radioactively contaminated layer. With a follow-up movement mechanism that follows the surface of the radioactively contaminated layer,
A decontamination movement mechanism equipped with the follow-up movement mechanism and moving the movable pedestal in a decontamination direction intersecting the laser irradiation direction,
Laser irradiation that is mounted on the movable pedestal so that it can follow the laser irradiation direction and can move in the decontamination direction, and is connected to the laser oscillator via an optical fiber to irradiate the radioactively contaminated layer with a laser beam. Mechanism and
A control unit capable of adjusting at least the output (that is, intensity), focal length, and irradiation range of a laser beam generated by the laser oscillator and emitted from the laser irradiation mechanism is provided.
The control unit generates a CW laser for removing and roughening the radioactive contaminated layer with the laser oscillator and irradiates it from the laser irradiation mechanism, and a pulse for removing the rest of the radioactive contaminated layer. It is characterized by including a switching means for switching to a second mode in which a laser is generated by the laser oscillator and the laser irradiation mechanism irradiates the roughened radioactive contaminated layer.

According to these inventions, the movable pedestal sensitively follows the unevenness of the surface of the radioactively contaminated layer, and the switching means of the control unit accurately maintains the focal length (separation distance) and the irradiation range (irradiation area) of the CW laser. The first aspect and the second aspect of the pulse laser are switched. At that time, in the first embodiment, when the radioactive contaminated layer is roughened and removed by irradiating with a high-power CW laser (for example, a maximum power of 2 kW), that is, when the radioactively contaminated layer is peeled off into a mottled pattern and melted or evaporated (FIG. 14 (FIG. 14). Even in B)), in the second aspect, by irradiating with a high-power pulse laser (for example, maximum output 2 kW, frequency 10 Hz), the roughened portion which is the residual portion of the radioactive contaminated layer is removed and flattened. (See FIG. 14 (C)). Therefore, the radioactively contaminated layer can be decontaminated with high efficiency and high accuracy without disassembling and cutting the radioactively contaminated substrate (for example, a large-diameter tubular storage tank for reactor cooling water).

In the present invention, the "CW laser" is a laser that is continuously irradiated, and the "pulse laser" is a laser that is intermittently irradiated. The "switching means" may be either an artificially operated changeover switch or a control signal for instructing the changeover operation.

The laser irradiation mechanism is fixed to the movable pedestal so as to maintain a constant distance from the surface of the radioactively contaminated layer through the first and second aspects.

Even if the laser type is changed between the first aspect and the second aspect, the separation distance (focal length) of the laser irradiation mechanism is kept constant, so adjustments such as laser output, irradiation range, and moving speed are kept to a minimum. It is possible to efficiently decontaminate the radioactively contaminated layer.

The switching means of the control unit is
In the first aspect, while the laser irradiation mechanism irradiates the CW laser, the decontamination movement mechanism moves back and forth along a predetermined path in a predetermined direction along the decontamination direction.
In the second aspect, while the laser irradiation mechanism irradiates the pulse laser, the decontamination movement mechanism switches and controls the decontamination movement mechanism so as to reversely move in the same path along the decontamination direction.

In the first aspect, it moves forward (for example, forward rotation) in a predetermined direction while irradiating a CW laser, and in the second aspect, it moves backward (for example, reverse rotation) while irradiating a pulse laser. In this way, by linking the laser type and the moving direction and controlling the switching, the radioactive contaminated layer can be decontaminated more efficiently and in a short time.

A gas injection mechanism that is mounted on a movable pedestal adjacent to the laser irradiation mechanism and injects gas so as to keep radioactive dust such as fume and dust generated from the radioactive contaminated layer by irradiation of the laser beam away from the laser irradiation mechanism.
It is mounted on a movable pedestal facing the gas injection mechanism with the laser irradiation mechanism sandwiched between them, and is equipped with a dust suction mechanism that sucks radioactive dust generated from the radioactive contaminated layer together with the gas injected from the gas injection mechanism under negative pressure.
The movable pedestal moves in the decontamination direction together with the decontamination movement mechanism while following the surface of the radioactively contaminated layer, and the laser irradiation mechanism, gas injection mechanism and dust suction mechanism mounted on the movable pedestal maintain a predetermined positional relationship. In this state, the radioactive contaminated layer is removed and the radioactive dust is sucked and discharged by the irradiation of the laser beam.

Since the gas injection mechanism and the dust suction mechanism can move integrally with the laser irradiation mechanism, the radioactive dust generated by the irradiation of the laser beam can be stably sucked and discharged. Air is generally used as the gas injected from the gas injection mechanism, but an inert gas (that is, a rare gas (helium, neon, argon, krypton, xenon, radon) instead of air or in addition to air is used. ), Nitrogen gas, carbon dioxide gas, etc.) can also be used.

The gas injection mechanism is
A first injection port that opens near the surface of the radioactively contaminated layer and prevents the radioactive dust generated from the radioactive contaminated layer from reattaching to the radioactive contaminated layer due to the irradiation of the laser beam.
It is open near the tip of the laser irradiation mechanism and has a second injection port for avoiding collision of the laser irradiation mechanism with the tip lens system by the radioactive dust generated from the radioactive contaminated layer.

By providing the first and second injection ports, the reattachment of the radioactive dust to the radioactive contaminated layer can be suppressed, and at the same time, the collision with the advanced lens system of the laser irradiation mechanism can be suppressed, so that the long life of the laser irradiation mechanism can be suppressed. Can contribute to the conversion.

By the way, in order to solve the above problems, the laser decontamination system of the present invention is used.
With the laser decontamination device mentioned above,
It is connected to the dust suction mechanism via a flexible hose and has a built-in suction flow path for negative pressure suction of radioactive dust generated by irradiation of the laser beam, and also to capture the radioactive dust flowing through the suction flow path. Equipped with a dust collector equipped with an air filter
The air filter includes a main filter located upstream of the discharge port to the atmosphere arranged at the end of the suction flow path and composed of a high-performance air filter such as a HEPA filter and a ULPA filter, and the main filter. Further, it is characterized by including a prefilter located on the upstream side of the suction flow path and composed of an air filter for coarse dust.

The radioactive dust sucked and discharged by the dust suction mechanism is adsorbed (that is, captured) by at least two stages of filters (pre-filter and main filter), so dust treatment work can be performed safely and it is discharged into the atmosphere from the discharge port. Does not cause environmental damage such as air pollution due to exhaust gas.

The HEPA filter (high efficiency particulate air filter) has a particle collection rate of 99.97% or more for particles with a particle size of 0.3 μm at the rated flow rate, and the ULPA filter (ultra low penetration air filter) has the rated flow rate. It has a particle collection rate of 99.9995% or more with respect to particles having a particle size of 0.15 μm. In particular, a filter having a particle collection rate of 99.9999% or more is sometimes called a super ULPA filter. Further, the coarse particle air filter is mainly used for removing particles having a particle size larger than 5 μm. Further, between the main filter and the pre-filter, for example, a medium efficiency particulate air filter (that is, an air filter having a medium particle collection rate for particles having a particle size smaller than 5 μm) is configured. You may add an intermediate filter to be used. In addition, these air filters conform to JIS Z8122 "contamination control term".

The dust collector has a spray mechanism for applying a scattering inhibitor to a used main filter and pre-filter that have captured radioactive dust.

By applying (spraying) a scattering inhibitor by the spraying mechanism, it is possible to prevent the external diffusion of radioactive dust when collecting and disposing of the used filter, and it does not adversely affect the environment and the human body.

The above pre-filter is held in a rectangular frame and is also held.
Inside the dust collector, a pre-filter accommodating space that crosses the suction flow path and is formed in a straight line so as to communicate with a pair of through holes formed in the two facing side walls is arranged.
When replacing the prefilter, the side surface of the frame of the new prefilter inserted from the inlet side through hole of one of the pair of through holes is the side surface of the frame of the used prefilter housed in the prefilter storage space. By pushing, the used prefilter is extruded from the outlet side through hole of the other of the pair of through holes, and a new prefilter is set in the prefilter storage space of the dust collector so as to cross the suction flow path. To.

As a result, the operator can carry out the replacement / disposal work without touching the used pre-filter. Therefore, for the pre-filter located upstream of the suction flow path and having a high collection rate of coarse particles harmful to the human body. Work safety is ensured. Although there is no problem in safety even if the operator performs the extrusion operation of the used pre-filter, the safety is further improved by causing a manipulator such as a robot arm to execute the extrusion operation.

Then, in order to solve the above problems, the laser decontamination method of the present invention is used.
Laser removal that removes (that is, peels, melts, or evaporates) the radioactively contaminated layer that contains at least the coating film applied to the surface of the substrate and the surface layer of the substrate and is contaminated with radioactivity from the main body of the substrate by a laser beam. It ’s a dyeing method.
The first step of irradiating the CW laser for removing and roughening the radioactive contaminated layer from the surface side of the coating film, and the pulsed laser for removing the rest of the radioactive contaminated layer are roughened radioactive contaminated layer. It is characterized by performing a second step of irradiating.

Further, in order to solve the above problems, the laser decontamination method of the present invention is used.
A radioactively contaminated layer containing at least the coating film applied to the inner peripheral wall surface of the steel sheet constituting the (upright) tubular tank and the surface layer portion of the steel sheet and contaminated with radioactivity is applied from the main body of the steel sheet by a laser beam. A laser decontamination method that removes (ie, peels, melts, or evaporates).
The first step of irradiating the CW laser for removing and roughening the radioactive contaminated layer from the inner surface side of the coating film, and the pulsed laser for removing the rest of the radioactive contaminated layer are roughened radioactive contamination. It is characterized by performing a second step of irradiating the layer.

According to these inventions, when the radioactive contaminated layer is roughened and removed by irradiating with a high-power CW laser (for example, maximum power of 2 kW) in the first step, that is, when it is peeled off into a mottled pattern and melted or evaporated. Even in (see FIG. 14B), the roughened portion, which is the residual portion of the radioactive contaminated layer, is removed by irradiating with a high-power pulse laser (for example, maximum output 2 kW, frequency 10 Hz) in the second step. And flattened (see FIG. 14 (C)). Therefore, the radioactively contaminated layer can be decontaminated with high efficiency and high accuracy without disassembling and cutting the radioactively contaminated substrate (for example, a large-diameter tubular storage tank for reactor cooling water).

In the first step, while irradiating the CW laser, it moves back and forth in a predetermined direction along a predetermined path along a decontamination direction that intersects the laser irradiation direction.
In the second step, the same path is restored in the opposite direction along the decontamination direction while irradiating the pulse laser.

In the first step, it moves forward (for example, forward rotation) in a predetermined direction while irradiating it with a CW laser, and in the second step, it moves backward (for example, reverse rotation) while irradiating it with a pulse laser. In this way, by linking the laser type and the moving direction and controlling the switching, the radioactive contaminated layer can be decontaminated more efficiently and in a short time.

The perspective explanatory view which shows an example of the laser decontamination system which concerns on this invention partially broken. The perspective explanatory view which shows the fitting state of the rotation shaft and a boss of FIG. The perspective explanatory view which shows the main part of the laser decontamination apparatus of FIG. 1 in an enlarged manner. A front view schematically showing a part of FIG. 3 in an enlarged manner. FIG. 3 is a plan sectional view schematically showing the dust collector of FIG. Similarly, a front sectional view. Similarly, a side sectional view. Explanatory drawing of pre-filter replacement work. The explanatory view of the pre-filter replacement work following FIG. The explanatory view of the pre-filter replacement work following FIG. Explanatory drawing of main filter replacement work. The explanatory view of the main filter replacement work following FIG. The process explanatory drawing of the laser decontamination method which concerns on this invention. Explanatory drawing which shows the cross section after laser decontamination step by step.

Hereinafter, embodiments of the present invention will be described with reference to the examples shown in the drawings. FIG. 1 is a perspective explanatory view showing an example of the laser decontamination system according to the present invention partially broken. The laser decontamination system 400 shown in FIG. 1 is, for example, a laser decontamination device 200 which is arranged inside and outside an upright cylindrical tank 1 located in a nuclear power plant and for removing a radioactive contaminated layer described later by a laser beam. , A dust collector 300 (dust collector) for negative pressure suction and capture of radioactive dust generated by irradiation of a laser beam, and a negative pressure suction and capture of dust containing radioactive dust in a cylindrical tank 1. It is equipped with one or a plurality of (here, two) sub-dust collectors 300S (auxiliary dust collectors).

FIG. 3 is an enlarged perspective explanatory view showing the main part of the laser decontamination apparatus 200, and FIG. 4 is a front view schematically showing a part thereof enlarged. The peripheral wall 2 (base) of the cylindrical tank 1 is made of stainless steel plate (for example, 12 mm in thickness), and the inner peripheral wall surface thereof is coated with a coating film P (for example, thickness 0.1 to 1) in order to enhance rust prevention and corrosion prevention functions. 0.2 mm tar epoxy resin) is applied and formed. As shown in FIG. 14 (A), as a result of being used as a storage tank for reactor cooling water, the coating film P and the surface layer portion SUR (for example, thickness 0.1 to 0.2 mm) of the peripheral wall 2 are radioactive. It is a contaminated radioactive contaminated layer RCL. The main part of the laser decontamination device 200 is carried in from the equipment insertion port 3a (see FIG. 1) formed in the canopy 3 of the cylindrical tank 1 from which the cooling water has been drained, and as shown in FIGS. 14 (B) and 14 (C). In addition, the radioactive contaminated layer RCL is removed from the main body SUB of the peripheral wall 2 by a laser beam.

Returning to FIGS. 3 and 4, the laser decontamination apparatus 200 has a laser oscillator 10 (see FIG. 1) that generates a laser beam outside the tank and a slider 31 that is arranged so as to be able to advance and retreat with respect to the peripheral wall 2 (coating film P). A follow-up movement mechanism 30 having a (movable pedestal), a decontamination movement mechanism 40 equipped with a follow-up movement mechanism 30, a laser gun 20 (laser irradiation mechanism) mounted on a slider 31, a laser gun 20, and a follow-up movement mechanism 30. , The elevating mechanism 50 that can move the decontamination movement mechanism 40 up and down integrally, the gas injection mechanism 60 mounted on the slider 31 adjacent to the laser gun 20, and the gas injection mechanism 60 that sandwiches the laser gun 20. The dust suction mechanism 70 mounted on the slider 31, the sub suction mechanism 70S (see FIG. 1) for sucking dust in the cylindrical tank 1 under negative pressure, and the laser output, focal distance, and irradiation range outside the tank. It includes an adjustable controller 80 (control unit; see FIG. 1).

The follow-up movement mechanism 30 urges the slider 31 toward the radial direction of the tank, which is the laser irradiation direction, while maintaining a predetermined separation distance from the surface of the peripheral wall 2 (coating film P), thereby urging the slider 31 to the peripheral wall 2. It is moved to follow the surface of (coating film P). Specifically, the slider 31 is pressed and urged to the outside in the radial direction by the pressing spring 32 (the urging member), and the rotating roller 33 (contactor) is formed so as to project outward in the radial direction from the slider 31. Since the rotating roller 33 is always in contact with the surface of the peripheral wall 2 (coating film P) by the pressing spring 32 with a constant force, the slider 31 is held at a constant distance from the surface of the peripheral wall 2 (coating film P). On the other hand, the decontamination moving mechanism 40 moves the slider 31 in the decontamination direction (here, the circumferential direction of the tank) intersecting the laser irradiation direction (radial direction of the tank).

The follow-up movement mechanism 30, the decontamination movement mechanism 40, and the elevating mechanism 50 will be specifically described. The decontamination moving mechanism 40 is erected along the center of the cylindrical tank 1 over the entire height, and the lower end is supported by a magnet bearing 42 (magnet bearing) provided on the bottom surface of the cylindrical tank 1. Has a (spindle). The rotary shaft 41 swings forward and backward by the driving force of the rotary motor 140 (rotation drive source; see FIG. 1) arranged outside the tank overcomes the magnetic force of the magnet bearing 42, and when the rotary motor 140 stops. The stopped state is maintained by the magnetic force of the magnet bearing 42. The rotary motor 140 is fixed to a turret 4 assembled on the upper surface of the canopy 3 of the cylindrical tank 1 (see FIG. 1).

The elevating mechanism 50 includes a boss 51 (elevating member) that is slidable in the direction of the central axis with respect to the rotating shaft 41 and is integrally rotatable in the circumferential direction, a hook 51b fixed to the upper part of the boss 51, and the outside of the tank. It has a winch 53 (winder; see FIG. 1) arranged in the hook 51b and a chain 52 (hanging member) hung between the hook 51b and the winch 53. As specifically shown in FIG. 2, a protrusion 51a (convex portion) is formed on the inner peripheral surface of the tubular boss 51 in the central axis direction, and a groove formed in the central axis direction on the outer peripheral surface of the rotating shaft 41. It is engaged with 41a (recess). As shown in FIG. 1, the winch 53 is driven by an elevating motor 150 (elevating drive source) arranged outside the tank. The elevating motor 150 is fixed to the upper surface of the closing rotary lid 3b for rotatably closing the equipment insertion port 3a of the canopy 3. Therefore, the boss 51 is integrally rotated with the rotating shaft 41 by the rotating motor 140, and is moved up and down along the rotating shaft 41 by the elevating motor 150 and the winch 53.

Returning to FIGS. 3 and 4, the boss 51 is formed with a plurality of rotating arms 43 (here, two at 180 ° intervals) extending long in the horizontal radial direction. A slider 31 is mounted on each rotating arm 43 so as to be movable in the radial direction.

Since the laser gun 20 is fixed to the slider 31, it can follow and move in the radial direction (laser irradiation direction), and can further rotate in the circumferential direction (decontamination direction). The laser gun 20 is connected to the laser oscillator 10 (see FIG. 1) outside the tank via the optical fiber 21, and irradiates the radioactive contaminated layer RCL (see FIG. 14 (A)) with a laser beam.

The gas injection mechanism 60 injects air (gas) so as to keep radioactive dust such as fume and dust generated from the radioactive contaminated layer RCL (see FIG. 14A) away from the laser gun 20 by irradiation with a laser beam. The gas injection mechanism 60 includes a first air injection nozzle 61 (first injection port) that opens near the surface of the peripheral wall 2 (coating film P) and a second air injection nozzle 62 (first air injection nozzle) that opens near the tip of the laser gun 20. It has a second injection port). The first and second air injection nozzles 61 and 62 are connected to the air compressor 160 (gas supply source) via the air hose 161 (see FIG. 1).

The first air injection nozzle 61 prevents the radioactive dust generated from the radioactive contaminated layer RCL due to the irradiation of the laser beam from reattaching to the radioactive contaminated layer RCL. On the other hand, the second air injection nozzle 62 prevents the radioactive dust generated from the radioactive contamination layer RCL from colliding with the tip lens system of the laser gun 20. In particular, since the second air injection nozzle 62 suppresses the collision of radioactive dust with the tip lens system of the laser gun 20, the durability of the laser gun 20 is improved. Since the laser irradiation direction of the laser gun 20 has a downward inclination angle θ (for example, θ = 20 °) with respect to the horizon, the reflected light on the peripheral wall 2 (coating film P) is the tip lens system of the laser gun 20. The durability of the laser gun 20 is improved in this respect as well.

The dust suction mechanism 70 sucks the radioactive dust generated from the radioactive contaminated layer RCL together with the air jetted from the gas injection mechanism 60 under negative pressure. Specifically, the hood 72 is fixed to the slider 31, and the radioactive dust is sucked under negative pressure from the suction port 71 opened in the hood 72. A laser gun 20, first and second air injection nozzles 61, 62, and a dust suction mechanism 70 are fixedly arranged on the slider 31, and these are the radioactive contaminated layer RCL associated with the irradiation of the laser beam with the mutual positional relationship unchanged. Remove and suck and discharge radioactive dust. Since the gas injection mechanism 60 and the dust suction mechanism 70 can move integrally with the laser gun 20, the radioactive dust generated by the irradiation of the laser beam can be stably sucked and discharged.

As shown in FIG. 1, the sub suction mechanism 70S is provided on the peripheral wall 2 of the cylindrical tank 1. Specifically, the sub suction port 71S opens at the lower part of the peripheral wall 2 and sucks the dust in the cylindrical tank 1 under negative pressure. The sub suction port 71S is also used as an existing inspection port (manhole or the like).

The controller 80 transmits a signal for controlling the generator 5, the laser oscillator 10, the rotary motor 140, the elevating motor 150, the air compressor 160, the dust collector 300, the sub dust collector 300S, and the like. Further, the controller 80 includes a laser changeover switch 81 (switching means) for switching the laser beam generated by the laser oscillator 10 to a CW laser or a pulse laser, an elevating changeover switch 82 for switching the rotation direction of the elevating motor 150 (winch 53), and the like. Is provided. The generator 5 supplies electric power to the laser oscillator 10, the controller 80, the rotary motor 140, the elevating motor 150, the air compressor 160, the dust collector 300, the sub dust collector 300S, and the like.

The laser changeover switch 81 of the control unit 80 switches between a first mode (first step) in which the laser oscillator 10 generates a CW laser and a second mode (second step) in which the laser oscillator 10 generates a pulse laser. In the first aspect, a CW laser for removing the radioactive contaminated layer RCL and roughening the surface is generated by the laser oscillator 10 and irradiated from the laser gun 20. In the second aspect, a pulse laser for removing the remainder of the radioactively contaminated layer RCL is generated by the laser oscillator 10 and irradiated from the laser gun 20.

More specifically, in the first aspect of the laser changeover switch 81, the decontamination moving mechanism 40 (rotating arm 43) rotates counterclockwise while the laser gun 20 irradiates the CW laser, while the second In the embodiment, the decontamination moving mechanism 40 (rotating arm 43) is switched and controlled so as to rotate clockwise while the laser gun 20 irradiates the pulse laser.

In the first aspect, it rotates counterclockwise (for example, forward rotation) while irradiating the CW laser, and in the second aspect, it rotates backward (for example, reverse rotation) while irradiating the pulse laser. In this way, by linking the laser type and the moving direction and controlling the switching, the radioactive contaminated layer RCL can be decontaminated more efficiently and in a short time. Even if the laser type is changed between the first aspect and the second aspect, the separation distance (focal distance) of the laser gun 20 is kept constant (for example, 300 mm) from the radioactive contaminated layer RCL, so that the laser output (for example). The radioactive contaminated layer RCL can be efficiently decontaminated by minimizing adjustments such as (maximum 2 kW), irradiation range (irradiation area; for example, maximum beam diameter 50 mm), and moving speed (for example, maximum 3 m / min).

Next, FIG. 5 is a plan sectional view schematically showing the dust collector 300, FIG. 6 is a front sectional view, and FIG. 7 is a side sectional view. The dust collector 300 is connected to the dust suction mechanism 70 (see FIGS. 3 and 4) via the flexible hose 271. The dust collector 300 has a built-in suction flow path 272 for negative pressure suction of radioactive dust generated by irradiation with a laser beam. The dust collector 300 is provided with air filters 273 and 274 for capturing radioactive dust flowing through the suction flow path 272. A suction fan 270 (negative pressure generation source) such as a turbo fan is arranged in the suction flow path 272, and is driven by a fan motor 270a (negative pressure drive source).

The sub dust collector 300S is connected to the sub suction mechanism 70S (see FIG. 1) via the flexible hose 271S. The sub-dust collector 300S has a built-in suction flow path 272 for negative pressure suction of dust (including radioactive dust) in the cylindrical tank 1. The sub-dust collector 300S is also provided with air filters 273 and 274 for capturing dust flowing through the suction flow path 272. A suction fan 270 (negative pressure generation source) such as a turbo fan is also arranged in the suction flow path 272 of the sub dust collector 300S, and is driven by a fan motor 270a (negative pressure drive source). As described above, since the sub-dust collector 300S has the same structure as the dust collector 300, the following description covers only the dust collector 300.

The suction flow path 272 branches to the left and right on the way, and a discharge port 272a into the atmosphere is arranged at the end of each branch. A main filter 273 (air filter) composed of a HEPA filter is arranged in the suction flow path 272 on the upstream side of the discharge port 272a, and is further upstream of the suction flow path 272 than the main filter 273 and before branching. A pre-filter 274 (air filter) composed of an air filter for coarse dust is arranged at the position of. The radioactive dust sucked and discharged by the dust suction mechanism 70 (see FIGS. 3 and 4) is adsorbed (captured) in two stages by the pre-filter 274 and the main filter 273, so that the dust treatment work can be performed safely and the discharge port. Exhaust gas emitted from 272a into the atmosphere does not cause environmental damage such as air pollution.

The main filter 273 is inserted from the discharge port 272a, and the mounting frame 273a is fixed to the left and right side walls of the dust collector 300 by the stopper 273b so that the mounting frame 273a surrounds the discharge port 272a. When replacing the main filter 273, loosen the stopper 273b, remove the mounting frame 273a and the main filter 273 integrally to the side, and collect them in the main filter disposal box BM (see FIG. 12).

The pre-filter 274 is held in a rectangular (here, square) frame 274a. Inside the dust collector 300, a suction flow path 272 is crossed, an inlet side through hole 276 (through hole) formed in the front side wall, and an outlet side through hole 277 (through hole) formed in the rear side wall. A pre-filter accommodating space 275 formed in a straight line so as to communicate with each other is arranged. The inlet-side through hole 276 is closed by an inlet-side opening / closing door 276a and a stopper 276b that opens and closes on the outside, and the exit-side through-hole 277 is closed by an exit-side opening / closing door 277a and a stopper 277b that opens and closes on the outside.

When the pre-filter 274 is replaced, the side surface of the frame body 274a of the new pre-filter 274 inserted from the inlet side through hole 276 and the frame body 274a of the used pre-filter 274 housed in the pre-filter housing space portion 275 by the push rod B. Press the side of (see FIGS. 8 and 10). As a result, the used pre-filter 274 is extruded from the outlet-side through hole 277 and collected in the pre-filter waste box BP (see FIG. 10). A new pre-filter 274 is set in the pre-filter accommodating space 275 of the dust collector 300 so as to cross the suction flow path 272. Since the operator can carry out the replacement / disposal work without touching the used pre-filter 274, the pre-filter 274, which is located upstream of the suction flow path 272 and has a particularly high collection rate of coarse particles harmful to the human body, is used. Work safety is ensured.

The dust collector 300 applies a scattering inhibitor to the used pre-filter 274 and main filter 273 that have captured radioactive dust, so that a pair of upper and lower pre-filter spray nozzles 280 (spray mechanism) and a pair of left and right main filters are used. It has a spray nozzle 290 (spray mechanism). The pre-filter spray nozzle 280 is connected to the pre-filter spray pump 281 (spray supply source), and the pre-filter spray pump 281 is driven by the pre-filter pump motor 281a (spray drive source). The main filter spray nozzle 290 is connected to the main filter spray pump 291 (spray supply source), and the main filter spray pump 291 is driven by the main filter pump motor 291a (spray drive source). By applying (spraying) the scattering inhibitor by the spraying mechanisms 280 and 290, it is possible to prevent the external diffusion of radioactive dust when collecting and disposing of the used filters 274 and 273, and it does not adversely affect the environment and the human body.

Next, the laser decontamination method according to the present invention will be described with reference to the process explanatory diagram shown in FIG.

<Preparation process (see Fig. 1)>
In S0, the laser decontamination device 200, the dust collector 300, and the sub dust collector 300S are set. Specifically, the rotating arms 43, 43 of the laser decontamination device 200 are folded along the rotating shaft 41, carried in from the equipment insertion port 3a of the canopy 3, and then the rotating arms 43, 43 are opened in the radial direction. The flexible hose 271 of the dust collector 300, the optical fiber 21 of the laser oscillator 10, the air hose 161 of the air compressor 160, the chain 52 of the winch 53, and the like are set through the closed rotary lid 3b. The sub flexible hose 271S of the sub dust collector 300S is connected to the sub suction port 71S of the sub suction mechanism 70S. Connection tools such as universal joints and flexible joints are also used when piping and wiring flexible hoses 271, air hoses 161 and optical fibers 21.

<First step (see Fig. 1, Fig. 3, Fig. 4, Fig. 14 (B))>
In S1, the rotation motor 140 (rotation arm 43) rotates forward by 180 ° (half circumference) by the laser changeover switch 81, during which the laser gun 20 irradiates a CW laser (for example, output 2 kW), and the gas injection mechanism 60. , The dust suction mechanism 70 and the sub suction mechanism 70S operate. The radioactively contaminated layer RCL is subjected to the actions of peeling, melting and / or evaporation by irradiation with a CW laser, and when the cross section after the first step is seen, the radioactive contaminated layer RCL is roughened, that is, as shown in FIG. 14 (B). It has been removed in a mottled pattern.

<Second step (see Fig. 1, Fig. 3, Fig. 4, Fig. 14 (C))>
In S2, the rotation motor 140 (rotation arm 43) is reversed by 180 ° (half circumference) by the laser changeover switch 81, during which the laser gun 20 irradiates a pulse laser (for example, output 2 kW, frequency 10 Hz) with a gas. The injection mechanism 60, the dust suction mechanism 70, and the sub suction mechanism 70S operate. Looking at the cross section after the second step, as shown in FIG. 14C, the roughened portion which is the residual portion of the radioactively contaminated layer RCL is removed and flattened. In the second step S2, the focal length (separation distance) of the laser beam is maintained at the same level as in the first step S1. Further, the output of the laser beam, the irradiation range (irradiation area), and the moving speed may be the same as or the minimum adjustment as in the first step S1.

In S3, if the integrated operating time (for example, 10 hours) has elapsed (YES in S3), the pre-filter replacement step and the main filter replacement step (S4, S5) are executed, and then the process proceeds to the ascending step (S6). do. If the cumulative operating time has not elapsed (NO in S3), the process immediately proceeds to the ascending step (S6). The integrated operating time when replacing the pre-filter 274 and the integrated operating time when replacing the main filter 273 may be set separately.

<Pre-filter replacement process (see FIGS. 8 to 10)>
In S4, the entrance side opening / closing door 276a is opened, and the exit side opening / closing door 277a is closed. A new pre-filter 274 is inserted through the inlet-side through hole 276 and pushed in until the frame 274a of the used pre-filter 274 hits the exit-side opening / closing door 277a (FIG. 8). The scattering inhibitor is sprayed from the upper and lower pre-filter spray nozzles 280 to the used pre-filter 274 (FIG. 9). After the scattering inhibitor is dried and fixed, the outlet side opening / closing door 277a is opened, and the push rod B is inserted through the inlet side through hole 276. The used pre-filter 274 is extruded from the outlet-side through hole 277 via a new pre-filter 274 and collected in the pre-filter waste box BP (FIG. 10). The new pre-filter 274 is hooked by the push rod B, pulled back to the inlet side through hole 276 side, and set in a fixed position of the suction flow path 272 (see FIG. 7).

<Main filter replacement process (see FIGS. 11 and 12)>
In S5, the scattering inhibitor is sprayed from the left and right main filter spray nozzles 290 to the used main filter 273 (FIG. 11). After the scattering inhibitor is dried and fixed, the mounting frame 273a and the used main filter 273 are integrally removed laterally and collected in the main filter disposal box BM (FIG. 12). A new main filter 273 is inserted integrally with the mounting frame 273a from the discharge port 272a and mounted in place (see FIG. 6).

<Ascending process (see FIGS. 1 to 3)>
In S6, the elevating motor 150 (winch 53) is driven by the elevating changeover switch 82 to raise the boss 51 (rotating arm 43).

In S7, if the upper limit position is reached (YES in S7), the operation is stopped, and if the upper limit position is not reached (NO in S7), the operation proceeds to S1.

<Post-treatment process (not shown)>
In the case of decommissioning, the cylindrical tank 1 is disassembled and cut. In the case of restart processing, the rust-preventive / anti-corrosion paint application nozzle is held on the slider 31 instead of the laser gun 20, and the rust-preventive / anti-corrosion paint (for example, tar epoxy resin paint) is applied to the inner peripheral wall surface of the peripheral wall 2. ..

The present invention is not limited to the examples described above. For example, the following changes are possible.
(1) In FIG. 2, a protrusion may be formed on the rotating shaft 41 and a groove may be formed on the boss 51.
(2) In FIG. 3, the chain 52 may be changed to another hanging member such as a wire or a rope.
(3) In FIGS. 1 and 3, three or more rotating arms 43 (laser gun 20) may be provided. When the number of rotating arms 43 is n, the swing angle of each rotating arm 43 is 360 ° / n.

(4) In S1 and S2 of FIG. 13, the forward / reverse angle range may be set to any angle smaller or larger than 180 ° (half circumference).
(5) Regarding S4 and S5 in FIG. 13, the steps may be reversed or may proceed at the same time.
(6) Further, S4 may be changed to a spraying process and S5 may be changed to a replacement process. For example, it is also possible to execute the spraying work on the pre-filter and the spraying work on the main filter in S4, and perform the replacement work on the pre-filter and the replacement work on the main filter in S5.

In the embodiment, a rotation mechanism (decontamination movement mechanism) 40 of the boss 51 by the groove 41a and the protrusion 51a and an elevating mechanism 50 of the boss 51 by the winch 53 or the like are provided, but a ball screw is provided between the rotation shaft 41 and the boss 51. By providing the spline mechanism, the forward / reverse rotation / elevation of the boss 51 can be performed individually or simultaneously. The specific structure of the ball screw spline mechanism is described in, for example, Japanese Patent Publication No. 5-70744, Japanese Patent Application Laid-Open No. 7-9260, Japanese Patent Application Laid-Open No. 62-49070, and the like, and detailed description thereof will be omitted.

Further, the scope of application of the present invention, that is, the object to be decontaminated is not limited to the cylindrical tank made of stainless steel plate, but is a non-metal (for example, concrete) and non-cylindrical (for example, square cylinder) container (for example, radioactive material). It can be applied not only to a storage box) but also to a flat, curved or bent structure having a coating film (for example, a partition wall of a radioactive material storage facility).

1 Cylindrical tank 2 Peripheral wall (base)
3 Canopy 3a Equipment insertion slot 10 Laser oscillator 20 Laser gun (laser irradiation mechanism)
21 Optical fiber 30 Follow-up movement mechanism 31 Slider (movable pedestal)
32 Pressing spring (urging member)
33 Rotating roller (contactor)
40 Decontamination movement mechanism 41 Rotating shaft (main shaft)
41a groove (recess)
43 Rotating arm 50 Lifting mechanism 51 Boss (lifting member)
51a Protrusion (convex part)
53 Winch (winder)
60 Gas injection mechanism 61 First air injection nozzle (first injection port)
62 Second air injection nozzle (second injection port)
70 Dust suction mechanism 80 Controller (control unit)
81 Laser changeover switch (changeover means)
200 Laser decontamination device 271 Flexible hose 272 Suction flow path 273 Main filter (air filter)
274 pre-filter (air filter)
274a Frame 275 Pre-filter accommodation space 276 Inlet side through hole (through hole)
277 Exit side through hole (through hole)
280 Pre-filter spray nozzle (spray mechanism)
290 Main filter spray nozzle (spray mechanism)
300 Dust collector (dust collector)
400 Laser decontamination system P coating film Surface layer of SUR substrate Main body of SUB substrate RCL Radioactive contamination layer

Claims (12)

A laser decontamination device that uses a laser beam to remove a radioactively contaminated layer that includes at least the coating film applied to the surface of the substrate and the surface layer of the substrate and is contaminated with radioactivity.
A laser oscillator that generates a laser beam and
The movable pedestal is arranged so as to be able to move forward and backward with respect to the radioactively contaminated layer, and the movable pedestal is urged toward the laser irradiation direction while maintaining a predetermined separation distance from the surface of the radioactively contaminated layer. With a follow-up movement mechanism that follows the surface of the radioactively contaminated layer,
A decontamination movement mechanism equipped with the follow-up movement mechanism and moving the movable pedestal in a decontamination direction intersecting the laser irradiation direction,
Laser irradiation that is mounted on the movable pedestal so that it can follow the laser irradiation direction and can move in the decontamination direction, and is connected to the laser oscillator via an optical fiber to irradiate the radioactively contaminated layer with a laser beam. Mechanism and
It is provided with a control unit capable of adjusting at least the output, focal length and irradiation range of the laser beam generated by the laser oscillator and irradiated from the laser irradiation mechanism.
The control unit generates a CW laser for removing and roughening the radioactive contaminated layer with the laser oscillator and irradiates it from the laser irradiation mechanism, and a pulse for removing the rest of the radioactive contaminated layer. A laser decontamination apparatus comprising a switching means for switching between a second mode in which a laser is generated by the laser oscillator and the laser irradiation mechanism irradiates the roughened radioactive contaminated layer. Laser removal that removes the radioactively contaminated layer containing at least the coating film applied to the inner peripheral wall surface of the steel sheet constituting the tubular tank and the surface layer of the steel sheet and contaminated with radioactivity from the main body of the steel sheet by a laser beam. It ’s a dyeing device,
A laser oscillator that generates a laser beam and
The movable pedestal is arranged so as to be able to move forward and backward with respect to the radioactively contaminated layer, and the movable pedestal is urged toward the laser irradiation direction while maintaining a predetermined separation distance from the surface of the radioactively contaminated layer. With a follow-up movement mechanism that follows the surface of the radioactively contaminated layer,
A decontamination movement mechanism equipped with the follow-up movement mechanism and moving the movable pedestal in a decontamination direction intersecting the laser irradiation direction,
Laser irradiation that is mounted on the movable pedestal so that it can follow the laser irradiation direction and can move in the decontamination direction, and is connected to the laser oscillator via an optical fiber to irradiate the radioactively contaminated layer with a laser beam. Mechanism and
It is provided with a control unit capable of adjusting at least the output, focal length and irradiation range of the laser beam generated by the laser oscillator and irradiated from the laser irradiation mechanism.
The control unit generates a CW laser for removing and roughening the radioactive contaminated layer with the laser oscillator and irradiates it from the laser irradiation mechanism, and a pulse for removing the rest of the radioactive contaminated layer. A laser decontamination apparatus comprising a switching means for switching between a second mode in which a laser is generated by the laser oscillator and the laser irradiation mechanism irradiates the roughened radioactive contaminated layer. The laser irradiation mechanism according to claim 1 or 2, wherein the laser irradiation mechanism is fixed to the movable pedestal so as to maintain a certain distance from the surface of the radioactively contaminated layer through the first aspect and the second aspect. .. The switching means of the control unit is
In the first aspect, while the laser irradiation mechanism irradiates the CW laser, the decontamination movement mechanism moves back and forth along a predetermined path in a predetermined direction along a decontamination direction.
In the second aspect, claims 1 to claim 1 to claim, wherein the laser irradiation mechanism irradiates the pulse laser and the decontamination movement mechanism switches and controls the decontamination movement mechanism so as to reversely move the same path along the decontamination direction. The laser decontamination apparatus according to any one of 3. A gas injection mechanism mounted on the movable pedestal adjacent to the laser irradiation mechanism and injecting gas so as to keep radioactive dust generated from the radioactive contaminated layer by irradiation of the laser beam away from the laser irradiation mechanism.
It is equipped with a dust suction mechanism that is mounted on the movable pedestal facing the gas injection mechanism with the laser irradiation mechanism interposed therebetween and sucks radioactive dust generated from the radioactive contaminated layer together with the gas injected from the gas injection mechanism. ,
The movable pedestal moves in the decontamination direction together with the decontamination movement mechanism while following the surface of the radioactively contaminated layer, and the laser irradiation mechanism, the gas injection mechanism, and the dust suction mechanism mounted on the movable pedestal are The laser decontamination apparatus according to any one of claims 1 to 4, wherein the radioactive contaminated layer is removed by irradiation with a laser beam and the radioactive dust is sucked and discharged while maintaining a predetermined positional relationship. The gas injection mechanism is
A first injection port that opens near the surface of the radioactively contaminated layer and prevents the radioactive dust generated from the radioactive contaminated layer from reattaching to the radioactive contaminated layer due to the irradiation of the laser beam.
The fifth aspect of claim 5 has an opening near the tip of the laser irradiation mechanism and a second injection port for avoiding collision of the laser irradiation mechanism with the tip lens system by radioactive dust generated from the radioactive contaminated layer. Laser decontamination equipment. The laser decontamination apparatus according to claim 5 or 6.
It is connected to the dust suction mechanism via a flexible hose and has a built-in suction flow path for negative pressure suction of radioactive dust generated by irradiation of the laser beam, and also to capture the radioactive dust flowing through the suction flow path. Equipped with a dust collector equipped with an air filter
The air filter includes a main filter located upstream of the discharge port to the atmosphere arranged at the end of the suction flow path and composed of a high-performance air filter, and the suction flow path further than the main filter. A laser decontamination system characterized by including a prefilter located upstream of the air filter for coarse dust. The laser decontamination system according to claim 7, wherein the dust collector has a spray mechanism for applying a scattering inhibitor to a used main filter and pre-filter that have captured radioactive dust. The pre-filter is held in a rectangular frame and is also held.
Inside the dust collector, a pre-filter accommodating space portion that crosses the suction flow path and is formed in a straight line so as to communicate with a pair of through holes formed in two facing side walls is arranged. ,
When the pre-filter is replaced, the frame of the used pre-filter accommodated in the pre-filter accommodating space on the side surface of the frame of the new pre-filter inserted from the inlet-side through hole of one of the pair of through holes. By pushing the side surface of the dust collector, the used prefilter is extruded and discharged from the outlet side through hole of the other of the pair of through holes, and the new prefilter crosses the suction flow path. The laser decontamination system according to claim 7 or 8, which is set in the filter accommodating space. A laser decontamination method for removing a radioactively contaminated layer containing at least a coating film applied to the surface of a substrate and a surface layer portion of the substrate and contaminated with radioactivity from the main body portion of the substrate by a laser beam.
The first step of irradiating the CW laser for removing and roughening the radioactive contaminated layer from the surface side of the coating film, and the radioactive contaminated layer roughened with a pulse laser for removing the rest of the radioactive contaminated layer. A laser decontamination method characterized by performing a second step of irradiating. Laser removal that removes the radioactively contaminated layer containing at least the coating film applied to the inner peripheral wall surface of the steel sheet constituting the tubular tank and the surface layer of the steel sheet and contaminated with radioactivity from the main body of the steel sheet by a laser beam. It ’s a dyeing method.
The first step of irradiating the CW laser for removing and roughening the radioactive contaminated layer from the inner surface side of the coating film, and the pulsed laser for removing the rest of the radioactive contaminated layer are roughened radioactive contamination. A laser decontamination method characterized by performing a second step of irradiating the layer. In the first step, while irradiating the CW laser, it moves back and forth in a predetermined direction along a predetermined path along a decontamination direction intersecting the laser irradiation direction.
The laser decontamination method according to claim 10 or 11, wherein in the second step, the pulse laser is irradiated and the same path is restored in the opposite direction along the decontamination direction.

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