JP3461948B2 - Underwater laser processing method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to preventive maintenance and repair techniques in, for example, a nuclear power plant, and is particularly suitable for improving residual stress on the surface of metal structures, removing cracks, removing clad, etc. in cooling water. Underwater laser processing method
Concerned .

[0002]

2. Description of the Related Art For example, the internal structure of a light water reactor is made of a material having sufficient corrosion resistance and high temperature strength under a high temperature and high pressure environment.
For example, it is made of austenitic stainless steel or nickel-based alloy.

However, of the internal structures, which are difficult to replace, the members are exposed to a high temperature and high pressure environment for a long time due to long-term operation of the plant, and the core material such as the core shroud is irradiated with neutrons. Therefore, there is a concern about the problem of material deterioration caused by these problems.

Particularly in the vicinity of the welded portion of the internal structure of the furnace, there is a risk of potential stress corrosion cracking due to sensitization of the material due to welding heat input and residual tensile stress.

Recently, various material surface improvement techniques have been developed as preventive maintenance measures in response to the extended operation period of the plant. As part of that, measures to prevent stress corrosion cracking by studying the stress on the material surface from positive to positive are studied.
Techniques for improving surface material stress by methods such as shot peening or water jet peening have been developed.

Shot peening is 0.3 mm to 1.2 mm
This is a technique of accelerating a steel ball having a diameter of about a degree using high-pressure air or centrifugal force, and plastically deforming the surface of the working part by the kinetic energy of the steel ball, thereby forming a compressive residual stress on the surface.

Further, water jet peening is
Ultra high pressure water of about 1000 atm is jetted from the tip of the nozzle,
It is a technique of forming compressive stress on the surface by a shock wave when water hammer action and cavitation break. Both of these technologies have been proved to be effective against stress corrosion cracking by construction in water, and some have been put to practical use.

Further, the structure near the welded portion of the reactor internal structure or the structure in a vibrating environment is vulnerable to the generation and development of cracks due to stress corrosion cracking and fatigue fracture during long-term operation of the plant, and further to cracking due to them. There is a concern that the sensitivity will increase, and measures are being considered.

For example, when a crack is generated on the surface of a structure, a cracking portion is removed by electric discharge machining, and stress concentration of the structure material is relaxed to prevent the crack from developing. Electric discharge machining is a machining method in which a voltage is applied between an electrode and a material to be processed to generate electric discharge, and the material to be processed is melted and blown away, and this countermeasure method has also been partially put into practical use.

On the surface of the furnace internal structure, Fe, Cu,
It is known that a clad containing Ni or the like adheres. Since the clad traps radioactive materials, it may cause increased exposure of workers performing repairs and preventive maintenance. In particular, the clad adhering to the fuel element may hinder the cooling effect of the cooling water on the fuel element, accelerate oxidation, and even lead to fuel destruction.

Regarding the removal of the clad adhering to the surface of the reactor internal structure, a removal method using high-pressure water flow such as water jet peening is currently carried out irregularly. Further, a method of stripping the clad by electric discharge machining or irradiation of ultrasonic waves, and a method of applying the shot peening to weaken the impact force of the steel ball to remove the clad are also being studied.

[0012]

By the way, in the method using a steel ball such as shot peening, when processing a structure of a narrow space such as an annulus between the core shroud and the reactor pressure vessel, It is difficult to recover steel balls completely. Further, a high-pressure pipe for transporting the steel balls with high-pressure water or high-pressure air is required, which is difficult to say as a simple processing method. Further, when the construction is performed in the atmosphere, there is a problem that dust is generated.

In the method using high-pressure water such as water jet peening, the reaction force of the jet water imposes a heavy load on the peripheral equipment, and it is difficult to develop an automatic machine for performing precision machining by remote control in a narrow space. Is.

The electric discharge machining has a problem that the material to be machined is greatly affected by heat, and it is difficult to apply the ultrasonic method to a narrow portion where ultrasonic waves are hard to reach.

That is, all of the above processing methods have problems in terms of simplicity, applicability to narrow spaces, influence on peripheral equipment, quality, etc., and it cannot be said that all of them are satisfied. Further, it is also extremely difficult to apply it to all three types of techniques of surface stress improvement, crack removal, and clad removal related to preventive maintenance and repair.

The present invention has been made in view of the above circumstances, and an object thereof is to perform work such as surface stress improvement, crack removal, and clad removal related to preventive maintenance and repair of nuclear reactor internal structure in a simple and high-performance manner. An object of the present invention is to provide an underwater laser processing method that is of high quality and can be performed without adversely affecting peripheral equipment, and that is also excellent in applicability to narrow spaces.

[0017]

In order to achieve the above object, the invention of claim 1 provides a high-power, short-pulse laser beam having a visible wavelength on the surface of a structure immersed in cooling water. Irradiation with the underwater laser processing method to improve the residual stress of the material on the structure surface, remove cracks or remove clad
The material of the reactor internals filled with cooling water
Detects cracks on the surface,
Laser beam with a visible wavelength of less than 100 nsec
The peak output per pulse is 0.1 to 10 GW / cm ²
Under the conditions of
It is characterized by irradiating while nitrating and removing cracks
It

[0018]

[0019]

According to a second aspect of the present invention, after the cracks generated on the surface of the internal structure of the nuclear reactor are removed, the stress of the material surface after the cracks are removed is improved by applying the treatment of the first aspect. It is characterized by

The invention of claim 3 irradiates the underwater laser beam according to claim 1 to remove the clad accumulated on the surface of the internal structure of the nuclear reactor filled with the cooling water while removing the material. It is characterized in that surface stress is improved.

[0022] The invention according to claim 4, by irradiating a laser beam on the material surface of the internal structure filled with the cooling water nuclear reactor, the material surface stress improvement according to claims 1 to 3, cracks removed, Alternatively, when performing clad removal, the entire construction range, construction unit area, and construction conditions are automatically controlled according to a map created based on the flaw detection inspection and surface condition inspection performed in advance and the structure drawing. To do.

[0023]

[0024]

Since the laser beam having a visible wavelength has high permeability in water, it is possible to directly irradiate the work piece in water.
When the material surface of the reactor internals is irradiated with a laser beam having a visible wavelength and having a high power and a short pulse in the reactor water, the atoms on the material surface are instantaneously melted and evaporated to generate plasma.

The generated plasma has an extremely high pressure because volume expansion is suppressed by the inertial force of water, and as a result, the material surface is plastically deformed and compressive stress remains. The residual compressive stress on the material surface leads to the prevention of stress corrosion cracking and can improve the surface residual stress of the reactor internal structure.

When a crack occurs on the surface of the internal structure of the nuclear reactor, the cracked portion has a visible wavelength and is repeatedly irradiated with a high-power and short-pulse laser beam to gradually evaporate the material in this portion. The crack can be removed. By removing the cracks in this manner, stress concentration in the structural material can be relaxed and the development of cracks can be suppressed.

When a clad is accumulated on the surface of the reactor internal structure, the material surface on which the clad is accumulated is irradiated with a laser beam having a visible wavelength, high power and short pulse, as described above. High-pressure plasma is generated on the material surface, and the clad can be peeled off from the material surface by the impact force at this time.

Therefore, by using the above-described method, it is possible to improve the surface stress, remove cracks, and remove cladding from the internal reactor structure.

Further, in the processing method using the laser beam as described above, since high energy is transmitted through the optical fiber, unlike shot peening, a high-pressure pipe for conveying steel balls with high-pressure water or high-pressure air is used. It is easy to handle without the need for

Further, as described above, since the visible laser beam can be transmitted directly in water, it can be directly constructed in cooling water. Therefore, it is not necessary to drain the cooling water in the furnace before the work. Since water has a high radiation shielding effect,
It can be expected to reduce the radiation exposure of workers.

Moreover, in the case of laser beam irradiation, since there is no mechanical reaction force, the control of the device is easy, and highly accurate processing can be performed. Further, when the pulse width of the laser beam is shortened, it is possible to perform processing with a small thermal effect due to heat conduction to the material to be processed.

Further, the powder of the surface constituting material and the clad which are released from the material surface at the time of laser irradiation can be prevented from being adversely affected on the water quality by sucking the powder and the clad into the processing head and trapping them. The water flow generated by this suction or the water flow generated for the purpose of removing bubbles on the optical path of the laser beam is weak, and the influence on peripheral devices is small. If the laser beam is transmitted by an optical fiber, the processing head can be downsized and can be applied to narrow spaces.

Therefore, it is possible to provide an underwater processing method which is simple and of high quality, does not adversely affect peripheral equipment, and has good applicability to narrow spaces.

[0034]

Embodiments of the present invention will be described below with reference to the drawings.

Embodiment 1 (FIGS. 1 to 6) In this embodiment, one pulse of a laser beam having a visible wavelength and a pulse width of 100 nsec or less is applied to the material surface of the reactor internal structure filled with cooling water. Peak output per hit 0.1 to 1
The present invention relates to an underwater laser processing method for improving the residual stress on the surface of a structure to a compressive stress by irradiating the structure with 0 GW / cm ² and the irradiation beam superposition rate of 100% or more.

As shown in FIG. 1, the reactor pressure vessel 1 is filled with cooling water 2. A laser beam 3 is guided to the inside of this nuclear power plant by an optical fiber 4 to improve the residual stress on the surface of the reactor internal structure 5.

That is, a pulse laser device 6 is installed outside the reactor pressure vessel 1, and the pulse laser device 6 is a copper vapor laser or a YAG laser (for second harmonic generation).
In such a visible wavelength pulse laser device, the pulse width of the oscillating laser beam is 100 nsec or less.

The laser beam 3 passes through an incident lens 7 and an optical fiber 4 and is filled with cooling water 2 in a reactor pressure vessel 1
Is guided to the inside of the reactor and condensed by the condenser lens 8 into light having a peak output per pulse of 0.1 to 10 GW / cm ² (diameter d). Is irradiated to the material surface (especially the welding line part).

FIG. 2 shows the laser beam 3 in this embodiment.
It is a figure which shows the irradiation method of. That is, in the present embodiment, as shown in the figure, the laser beam 3 is continuously irradiated by scanning the surface of the reactor internal structure 5 so that the irradiation spots 10 of the laser beam 3 overlap each other.
At this time, the average superimposition ratio of the irradiation spot 10 of the laser beam 3 is set to 100% or more by not forming an unirradiated region of the laser beam 3 on the surface to be processed and changing the diameter of the irradiation spot 10 to perform irradiation. To do.

According to the method of the first embodiment, the following actions and effects can be obtained.

That is, it has a visible wavelength and a pulse width of 100 ns.
When the surface of the material of the reactor internal structure 5 is irradiated with the laser beam 3 having a peak output of 0.1 to 10 GW / cm ² at ec or less, atoms in the outermost layer of the material are instantaneously melted and evaporated, and plasma is generated. Occur. In the atmosphere of the cooling water 2, the generated plasma has volume expansion suppressed by the inertial force of the water and becomes extremely high pressure, reaching several hundred MPa to several tens GPa. The shocking high pressure plastically deforms the surface of the material, and compressive stress remains.

The reason for using the laser beam 3 having a visible wavelength is that it has good underwater permeability and is suitable for underwater processing. The reason for setting the pulse width to 100 nsec or less is 100 ns
This is because if it exceeds ec, the material may be affected by heat and the corrosion resistance of the material may be reduced. Peak output 0.1 to 10
The reason for the GW / cm ^2, in less than 0.1GW / cm ² was evaporated to melt the material surface layer of atoms, there is may not be enough to generate a plasma, 10 GW / cm ²
This is because in a super-high electric field, water is ionized due to a strong electric field, which may make it difficult to collect the laser beam 3.

By continuously irradiating the laser beam 3 by scanning and applying the laser beam 3 so that the irradiation spots 10 of the laser beam 3 overlap with each other, the compressive stress can efficiently and uniformly remain on the entire surface to be processed. . In addition,
In this embodiment, because it also has the effect of preventing rapid cooling of the irradiated part,
Cracking of the material to be processed due to rapid cooling is unlikely to occur.

In the processing using the laser as described above, since high energy is transmitted through the optical fiber 4,
Unlike shot peening, there is no need to use high-pressure piping for transporting steel balls with high-pressure water or high-pressure air, and handling is simple. Further, since the visible light laser can directly transmit in water, it can be directly installed in the cooling water 2.
Therefore, it is not necessary to drain the cooling water 2 in the furnace before the work.
Since water has a high radiation shielding effect, it can be expected to reduce the exposure of workers.

Moreover, in the case of laser irradiation, since there is no mechanical reaction force, the control of the device is easy and highly accurate processing is possible, and since the pulse width of the laser is short, heat conduction to the material to be processed is achieved. Processing that is less affected by heat can be performed. Further, since the laser beam 3 is transmitted by the optical fiber 4, the processing head can be downsized, and the work can be performed on the narrow space.

Therefore, according to the method of the first embodiment, processing such as preventive maintenance and repair of the structure in the nuclear reactor can be performed easily and with high quality, and with excellent applicability to narrow spaces. The effect is played.

Next, a first modification of the first embodiment will be described. In this modification, the diameter d of the irradiation spot 10 is
And a condition of the superimposition rate of the irradiation beam to arbitrarily control the residual stress value on the surface of the material and the depth of the residual compressive stress inside the material.

In the first modification, the diameter d of the irradiation spot 10 and the superimposition ratio of the irradiation beam are set for the purpose of arbitrarily controlling the depth of the residual stress value on the material surface and the residual compressive stress inside the material. Adjust.

When the laser beam 3 is focused and irradiated on the surface of the material, the area density of power per pulse (unit: GW / cm ² ) can be changed by changing the diameter d of the irradiation spot 10. . The residual stress value on the surface of the material and the depth of the residual compressive stress inside the material strongly depend on the areal density of the power per pulse. On the other hand, these two physical quantities also strongly depend on the superimposition ratio of the irradiation beam.

Therefore, by adjusting the two conditions of the diameter of the irradiation spot 10 and the superimposition ratio of the irradiation beam,
It is possible to arbitrarily control two values, that is, the residual stress value on the surface of the material and the depth to which the residual compressive stress inside the material reaches.

Next, a second modification of the first embodiment will be described with reference to FIGS. 3 and 4. This variation is
In the construction unit area 11 for irradiating the laser beam 3,
After irradiating a laser beam of a predetermined number of pulses in one row, when moving to the next row, by increasing the scanning speed of the beam so that the transition is completed between laser irradiation pulses, the beam irradiation is performed in only one direction. It relates to an underwater laser processing method.

FIG. 3 shows a typical irradiation method of the laser beam 3 known so far. First, after irradiating one row of the pulse laser beam at the scanning speed v, the irradiation proceeds to the next row while irradiating the pulse laser beam at the same scanning speed v, and again irradiates the pulse laser beam at one row at the scanning speed v. . Normally, since the laser pulse oscillates at a constant cycle, the pulsed laser beam is emitted during the transition to the next row.

On the other hand, FIG. 4 shows a method according to the second modification, in which the scanning speed v'during transition to the next row is set so that the transition is completed between laser irradiation pulses.
It is extremely fast.

According to the second modification as described above, in the typical laser beam 3 irradiation method shown in FIG. 3, there is a possibility that the distribution of the irradiation beam superimposition ratio may deviate at the turn-back portion of the scanning at the irradiation spot 10 position. On the other hand, as shown in FIG.
The scanning speed v ′ during the transition to the next row is made extremely high so that the transition is completed between the laser irradiation pulses, and the number of irradiations during the transition to the next row is set to 0, whereby the irradiation beam at the folded portion is changed. The uneven distribution of the superimposition ratio can be eliminated, and the nonuniformity of the irradiation beam superimposition ratio can be reduced.

As described above, in this modification, the nonuniformity of the superimposition ratio of the irradiation beam can be reduced, so that the compressive stress can be uniformly left on the surface to be processed.

Next, a third modification of the embodiment will be described with reference to FIGS. This modification relates to the underwater laser processing method for shaping the irradiation spot 10 of the laser beam 3 into an elliptical shape (FIG. 5) or a rectangular shape (FIG. 6).

That is, it is assumed that a strong tensile stress remains in the surface of the reactor internal structure 5, for example, in the y direction in the figure. In this case, the irradiation spot 10 is shaped into an ellipse having a long axis in the y direction or a rectangular shape having long sides in the y direction, and the irradiation position is scanned to continuously irradiate,
The shock wave generated by ablation can be made uniform in the y direction, a stronger compressive stress can be applied in the y direction than in the x direction, and the residual stress in the y direction can be changed from tensile to compressive. Therefore, according to this third modification,
Residual stress can be improved for certain directions.

Example 2 (FIG. 7) In this example, a crack generated on the surface of the internal structure of the reactor in the cooling water was detected, and a visible wavelength with a pulse width of 100 nsec or less was detected for this crack. Have 1 laser beam
The present invention relates to an underwater laser processing method for completely removing cracks by irradiating under conditions of peak output per pulse of 0.1 to 10 GW / cm ² while monitoring the acute angle or the state where cracks are ablated and removed. .

That is, as shown in FIG.
The surface of the reactor internal structure 5 is examined by the CCD camera 13 attached to the
If the crack is observed, the laser beam 3 is applied to the crack. The CCD camera 13 and the monitor TV 15 are connected by a signal cable 16. As the laser beam 3, a pulse width oscillated from a pulse laser device 6 such as a copper vapor laser or a YAG laser (for second harmonic generation) installed outside the reactor pressure vessel 1 is 100 nsec or less and a visible wavelength is emitted. Using the laser beam, the laser beam is guided to the inside of the reactor pressure vessel 1 filled with the cooling water 2 through the incident lens 7 and the optical fiber 4, and is condensed by the condenser lens 8 so that the peak output per pulse is 0.1. 10 GW / cm ²
The irradiation of the laser beam 3 is repeated while the CCD camera 13 attached to the processing head 12 monitors the ablation removal state of the crack 14 until the crack 14 is completely removed.

In the method of the second embodiment, the peak output is 0.1 with a visible wavelength and a pulse width of 100 nsec or less.
By irradiating the surface of the material of the reactor internal structure 5 with the laser beam 3 of 10 GW / cm ² in the atmosphere of the cooling water 2, the atoms of the extreme surface layer of the material are instantaneously melted and evaporated.
This phenomenon is called ablation. By repeatedly irradiating the crack portion with the laser beam 3, the material of the crack portion can be gradually removed by ablation, and finally the crack 14 can be completely removed.

The reason for using the laser beam 3 having a visible wavelength is that it has good permeability in water and is suitable for underwater processing. The reason for setting the above pulse width is that if it exceeds 100 nsec, the material may be thermally affected and the corrosion resistance of the material may be reduced.

The reason for setting the peak output to 0.1 to 10 GW / cm ² is that if it is less than 0.1 GW / cm ² , it may be insufficient to instantaneously melt and evaporate the atoms in the surface layer of the material. This is because if it exceeds 10 GW / cm ² , water may be ionized by a strong electric field and it may be difficult to collect the laser beam 3.

In the case of processing by laser irradiation as described above, since there is no mechanical reaction force, the control of the device is easy and highly accurate processing can be performed. Further, since the visible laser can directly transmit in water, it can be directly processed in cooling water, and it is not necessary to drain the cooling water 2 in the furnace before the work. Since water has a high radiation shielding effect, it can be expected to reduce the exposure of workers.

Moreover, since the pulse width of the laser is short,
The thermal effect of heat conduction on the material to be processed is small. Further, since the laser beam 3 is transmitted by using the optical fiber 4, the processing head 12 can be downsized and can be installed in a narrow space.

Therefore, according to the method of the second embodiment, high quality and applicability to a narrow space can be improved.

Example 3 This example relates to an underwater laser processing method in which a crack generated on the surface of a reactor internal structure is removed and then a residual stress improving process is performed on the material surface after the crack removal. .

That is, after the cracks 14 generated on the surface of the reactor internal structure 5 are completely removed by using the method of Example 2, the surface of the material after the cracks are removed by the method of Example 1 is removed. It improves the stress.

According to the method of Example 3, the cracks 14 are removed by applying the method of Example 1 to the cracked portion and then applying the method of Example 1, so that the stress concentration of the structural material is eliminated. Can be relaxed to suppress the development of cracks 14, and sufficient compressive stress can be left on the surface of the material after the cracks are removed to prevent stress corrosion cracking.

Example 4 (FIG. 8) In this example, as shown in FIG. 8, a visible wavelength of 100 nsec or less was applied to the surface of the reactor internal structure 5 filled with the cooling water 2 and accumulated in the cladding 17. Laser beam with
The peak output per pulse is 0.1 to 10 GW / cm ² ,
The present invention relates to an underwater laser processing method in which irradiation is performed under the condition that the weight ratio of the irradiation beam is 100% or more to remove the clad 17 accumulated on the material surface and at the same time improve residual stress on the material surface.

The laser beam 3 is guided to the inside of the reactor pressure vessel 1 by the optical fiber 4, and while monitoring, clad removal and residual stress improvement on the surface of the reactor internal structure 5 are performed.

In this case, the surface of the reactor internal structure 5 is inspected by the CCD camera 13 attached to the processing head 12, and if accumulation of the clad 17 is recognized, the clad accumulated portion is irradiated with the laser beam 3. The laser beam 3 is a laser pulse having a pulse width of 100 nsec or less and a visible wavelength oscillated from a pulse laser device 6 such as a copper vapor laser or a YAG laser (for second harmonic) installed outside the reactor pressure vessel 1. A reactor pressure vessel 1 filled with cooling water 2 through an incident lens 7 and an optical fiber 4.
It is guided to the inside and condensed by the condenser lens 8 to have a peak output per pulse of 0.1 to 10 GW / cm ² .

Also in the fourth embodiment, as in the first embodiment, the irradiation of the laser beam 3 is continuously performed by scanning, and the irradiation spots 10 of the laser beam 3 are overlapped. At this time, the laser beam 3 is applied to the surface to be processed.
The non-irradiated area is not formed and the diameter of the irradiation spot 10 is changed to make the average superimposition ratio of the irradiation beam 100% or more. During the beam irradiation, the removal status of the cladding 17 is monitored by the CCD camera 13.
After the irradiation of the unit irradiation area is completed, an inspection by the CCD camera 13 is performed. As a result, when the adhesion of the clad 17 is recognized, the irradiation of the unit irradiation area is performed until the clad 17 is completely removed. repeat.

According to the method of Example 4, the internal structure of the reactor in which the cladding 17 has accumulated the laser beam 3 having the visible wavelength and the pulse width of 100 nsec or less and the peak output of 0.1 to 10 GW / cm ^2. By irradiating the surface of the object 5, the atoms in the cladding 17 and the surface layer of the structure material are instantaneously melted and evaporated to generate plasma. In the atmosphere of the cooling water 2, the generated plasma is suppressed to a very high pressure by volume expansion due to the inertial force of the water, and becomes several hundred MPa to several tens G.
Reach Pa. Due to this impact force, the clad 17 is peeled off from the material surface and removed, and at the same time, the material surface is plastically deformed and compressive stress remains.

The reason why the visible wavelength laser beam 3 is used is that it is suitable for underwater processing because it has good underwater permeability. The reason for setting the above pulse width is that if it exceeds 100 nsec, the material may be thermally affected and the corrosion resistance of the material may be reduced. The reason for setting the peak output is 0.1 G
If it is less than W / cm ² , it may be insufficient to melt and evaporate the atoms on the surface layer of the material to generate plasma,
This is because if it exceeds 10 GW / cm ² , water may be ionized due to a strong electric field and it may be difficult to collect the laser beam 3.

Irradiation of the laser beam 3 is continuously performed by scanning, and the irradiation spots 10 of the laser beam 3 are applied so as to overlap each other, so that the removal of the clad from the entire surface to be processed and the improvement of the residual stress can be carried out efficiently and uniformly. Can be done. Note that, in this embodiment as well, there is an effect of preventing rapid cooling of the irradiated portion, so cracking of the material to be processed due to rapid cooling can also be prevented.

Further, in the processing using the laser beam as described above, it is necessary to use high pressure piping for transmitting high energy through the optical fiber 4 and carrying steel balls with high pressure water or high pressure air like shot peening. Easy to handle as there is no Further, since the visible light laser can directly transmit in water, it can be directly installed in the cooling water 2. Therefore, it is not necessary to drain the cooling water 2 in the furnace before the work. Since water has a high radiation shielding effect, it can be expected to reduce the exposure of workers.

Moreover, in the case of laser irradiation, since there is no mechanical reaction force, the control of the device is easy and highly accurate processing can be performed. Further, since the pulse width of the laser is short, it is possible to perform processing with a small thermal influence due to heat conduction to the material to be processed. Further, since the laser beam 3 is transmitted by using the optical fiber 4, the processing head 12 can be downsized, and the work can be performed on a narrow space.

Therefore, even by the above method,
It is possible to provide a processing method having high quality and good applicability to narrow spaces.

Example 5 (FIGS. 9 to 11) In this example, a reactor internal structure 5 filled with cooling water 2 was used.
When irradiating the surface with the laser beam 3 to improve the stress on the material surface, remove cracks, or remove clad, the entire range of construction, construction unit area 11, construction conditions, etc. are preliminarily tested for flaw detection and surface condition inspection. The present invention relates to an underwater laser processing method in which a map is created based on an internal structure drawing and a map, and a construction computer is programmed to carry out the construction automatically to perform construction control.

FIG. 9 is a flowchart showing the work procedure according to this embodiment.

First, a reactor internal structure drawing is input (step S101), and a flaw detection inspection and a surface condition inspection of the surface of the reactor internal structure 5 are carried out based on this drawing (step S102). The inspection result is determined (step S10).
3) If the result is good, the process ends. If it is judged as a result of the inspection that residual stress on the material surface needs to be improved, cracks removed, or clad removed (in the case of failure), the entire construction range and construction unit area 1 when performing these processings
1 and construction conditions are planned and a construction map is created (step 104).

Then, while automatically controlling by a computer programmed to execute the construction according to the construction map (step S105), the residual stress on the surface of the reactor internal structure 5 is improved, cracks are removed, or clad is removed (step S106). ). After that, a flaw detection inspection and a surface state inspection of the surface of the reactor internal structure 5 are performed again (step 10
2) Repeat this work routine until the inspection result is good.

According to the method of the fifth embodiment, as in the first, second and fourth embodiments, the high power and short pulse laser beam 3 having the visible wavelength is atomized in the atmosphere of the reactor water. By irradiating the surface of the reactor internal structure 5, the surface stress of the reactor internal structure 5 is improved, cracks are removed,
And clad removal can be performed.

By performing these processes in advance and inspecting the reactor internal structure 5 and constructing according to the map created based on the reactor internal structure drawing, the stress on the structure surface is improved with respect to the entire interior of the reactor. , Crack removal, and clad removal can be comprehensively and efficiently performed.

Further, when performing the construction according to the map, the construction can be controlled more efficiently by automatically controlling the construction using a computer. Also, by repeating the construction and inspection, highly reliable repair or preventive maintenance can be performed.

10 and 11 show a modification of the fifth embodiment. In this modification, the superimposition ratio of the irradiation beam in the vicinity of the boundary 11c between the two construction unit regions 11a and 11b is gradually reduced, and the construction is performed so that the boundary is overlapped, so that the entire construction part is made uniform. The present invention relates to an underwater laser processing method for obtaining a distribution of superposition ratios of irradiation beams.

According to the method of such a modification, the distribution of the superimposition ratio of the irradiation beam is uniform over the entire construction portion including the boundary portion 11c between the construction unit regions 11a and 11b, and therefore over the entire construction portion. Compressive stress can remain.

Embodiment 6 (FIGS. 12 to 25) This embodiment relates to the case where underwater laser processing is performed on the inner surface of the core shroud of the reactor pressure vessel.

That is, in this embodiment, a remote repair device having a laser irradiation device is provided at the tip of the link type arm, and this remote repair device is suspended from above in the reactor pressure vessel by a wire. Then, the remote repair device is installed on the core support plate by passing through the upper lattice plate opening in the center of the core, and the visible laser beam generated by the pulse laser device is applied to the core shroud at the laser irradiation position.

In this embodiment, a mechanism for adjusting the output per pulse is provided, and the laser beam is guided to the laser irradiation device at the tip of the link type arm through the optical fiber of the composite cable in which the power cable, the signal cable and the optical fiber are combined. . Then, the spot diameter of the irradiation laser is adjusted by the processing head of the laser irradiation device, the superimposition ratio of the irradiation laser beam is adjusted, and the laser beam is irradiated while performing oscillating scanning in a fixed range, and the inner surface of the core shroud is adjusted. It is for processing.

FIG. 12 schematically shows the structure and working state of the sixth embodiment.

That is, as shown in FIG. 12, a folding arm 24 is installed between the upper lattice plate 22 and the core support plate 22 installed in the core of the reactor pressure vessel 21, and the tip of this arm 24 is installed. A laser peening work unit 26 as a processing head is attached to the repair work unit attachment base 25.

In addition, a power cable for driving and controlling the folding arm 24 and the laser peening operation unit 26, a signal cable, and a composite cable 28 in which an optical fiber for transmitting a laser beam for performing a laser peening operation are bundled are controlled. It is guided from the chamber 29 to the upper end of the folding arm 24, and a part of it is extended to the laser peening working unit 26 and connected.

An operation panel 30, a pulse laser device 31, and a beam intensity adjusting device 32 are installed in the control room 29. In the operation panel 30, control of the pulse laser device 31,
It controls the laser peening operation unit 26 and the folding arm 24.

In FIG. 12, 33 is a jet pump, 34 is a core shroud, 35 is an annulus, and 36 is a lower chamber of the reactor vessel.

FIG. 13 and FIG. 14 show the folding arm 2
4 shows the configuration of No. 4, the installation state, and the attachment configuration of the associated jigs and tools. The foldable arm 24 is housed in a vertically integrated upper case 37 and a lower case 38 so as to be expandable.
7, 38 are suspended by an overhead crane (not shown) via a wire 39, penetrate through the opening 40 of the upper lattice plate 22 and the opening 41 of the core support plate 23, and a control rod drive device. It is installed in the housing 42 and then unfolded. An upper case guide device 43 and a lower case guide device 44 are attached to the upper part of the upper case 37. The lower case guide device 44 is fixed to the upper lattice plate 22 with fixing legs 45. The foldable arm 24 is configured to expand and contract the rod 69 by the air cylinder 46. Further, the folding arm 28 is connected to the balancer 49 by the wire 48 via the pulley 78a. In the figure,
Reference numeral 51 is a connecting rod, 66 and 71 are air cylinders, 74,
75 is a bearing.

A repair work unit mount 25 is attached to the tip of the folding arm 24. In addition, the repair work unit transfer device 50 is suspended by an overhead crane (not shown) by a wire 39, and the upper grid plate 2
It is adapted to be fixed to the upper surface of 2 by a fixing leg 45a. The repair work unit transport device 50 is equipped with a repair work unit 52.
Is transferred to the repair work unit mount 25 at the tip of the folding arm 24.

FIG. 15 shows the laser peening operation unit 26 and shows a state in which the wall 53 of the core shroud 34 is being repaired. Laser peening work unit 2
6 is fitted and mounted by a mounting device 54 to a repair work unit mounting base 70 at the tip of the folding arm 24.

The laser peening operation unit 26 includes:
An oscillating device 56 for guiding the composite cable 28 and oscillating the galvano mirror 55 inside, a spot diameter adjusting mechanism 57 for adjusting the irradiation laser spot diameter,
A CCD camera 58 for monitoring the laser irradiation surface and a motor 5 for driving the laser peening operation unit 26 in the longitudinal direction.
9 and an ultrasonic detector 60 are provided. A shutter 84 is attached in front of the CCD camera 58.

Further, the laser peening operation unit 26
A leg 61 protruding toward the wall 53 is attached to the, and the tip end of the leg 61 is in contact with the wall 53. In the leg 61,
An ultrasonic detector 60 is attached. In the figure, reference numeral 79
Is a signal cable.

In the underwater laser processing apparatus of the sixth embodiment having the above-described structure, when the light water cooled reactor is to be inspected or repaired, the lid of the reactor pressure vessel 21 is first removed and the reactor pit is removed. A remote reactor working device handling device (not shown) is installed on the floor surface of 62, and an upper part of the reactor pressure vessel 21 in which the folding arm 24 is housed is installed by a crane for checking and repairing devices (not shown). The case 37 and the lower case 38 connected to the lower end thereof are suspended.

Then, the openings 40 of the upper grid plate 22 and the openings 41 of the core support plate 23 are successively passed through, and the lower end of the lower case 38 is fitted into the control rod drive device housing 42, and the installation is completed.

In order for the upper case 37 and the lower case 38 to easily pass through the openings 40 of the upper lattice plate 22,
The upper case guide device 43 and the lower case guide installation device 44 are attached so as to be movable in the axial direction (vertical direction) of the upper case 37 and the lower case 38.
7 and the lower case 38 are the openings 40 of the upper lattice plate 22.
The rotation is aligned in the plane as it passes through. Continue to hang the lower case guide installation device 44 to the fixing leg 4
The lower case 38 is fixed to the upper grid plate 22 at 5, and the lower end of the lower case 38 is fitted into the control rod drive mechanism housing 42, and the installation is completed.

The foldable arm 24 is laterally developed from the upper case 37 in the lower lattice plate lower chamber 68, and the foldable arm 24 is inserted through the motor 63 and the gear assembly 64 provided in the upper case 37. The air cylinder 46 of the upper case 24 to which is attached is driven, the rod 69 is lifted to the vicinity of the upper lattice plate 22, and the air cylinder 46 is driven while rotating the upper case 37 around the vertical axis.
The rod 47 is moved in and out in the radial direction (lateral direction) of the core shroud 34, and the repair work unit mounting base 25 attached to the tip of the rod 47 is moved below a predetermined opening 40 of the upper lattice plate 22.

In a state where the repair work unit 52 is housed in the repair work unit transport device 50 to which the installation guide device 65 is attached, the repair work unit 52 is hoisted into the reactor pressure vessel 21 by an inspection and repair device hoisting crane (not shown), Upper lattice plate 2
It installs in the 2 predetermined opening part 40. Then, it is fixed to the upper grid plate 22 by the fixing legs 45 attached downward to the installation guide device 65.

The repair work unit 52 is pushed out below the repair work unit transport device 50 to remove the repair work unit 52.
The connecting member 67 and the repair work unit mount 25 at the tip of the rod 47 of the folding arm 24 are connected.

When the coupling is completed, the grip state of the repair work unit 52 by the repair work unit transfer device 50 is released. After this release is completed, the folding arm 24 is three-dimensionally moved within the lower lattice plate lower chamber 68, and the repair work unit 52 is moved to a predetermined position of the core shroud 34 to perform a collecting work.

The repair work unit 52 includes an inspection and inspection work unit, an arc welding work unit, an EDM.
A working unit, a grinder working unit, a laser cutting working unit, a laser welding working unit, a laser peening working unit, etc. are used.

In the sixth embodiment, the repair work unit 52
The surface of the welded portion of the core shroud 34 is modified from a tensile stress state to a compressive stress state by using the laser peening operation unit 26 or the like.

The surface modification method using the laser spot swing type laser peening operation unit 26 according to the sixth embodiment will be described below.

A connecting member 67 which is a fitting structure portion of the repair work unit mounting base 70 at the end of the rod 47 of the folding arm 122 and a fitting structure portion of the mounting device 54 of the laser spot rocking type laser peening work unit 26. And
Bind to each other.

The rod 69 is extended to the core shroud 34.
In places where tensile stress is generated on the surface due to the welding line of
The laser spot swing type laser peening operation unit 26 is moved so that the legs 155 move the wall 7 of the core shroud 34.
2 Stop the extension operation at the position where it is pressed against the surface. This completes the installation of the laser spot rocking type laser peening operation unit 26.

Next, referring to FIG. 15 and the like, a case where the surface of the weld line portion in the longitudinal direction of the core shroud 34 is modified will be described.

When the oscillating device 56 is driven, the galvanic mirror 55 oscillates, and the spot point 73 of the laser beam 72 scans for a certain width in the direction perpendicular to the paper surface of FIG. 15 (hereinafter, this is referred to as sweeping in the width direction).

The motor 63 mounted in the upper case 37 so that the contact welding portion is located within this scanning range.
The foldable arm 24 is rotated by the combined gear 64.

As the laser beam 72, the number of repetitions is 5K.
A Hz copper vapor laser is used. If the diameter is used an optical fiber of about 0.3 ^phi mm, by using a Atsumarihikarigumi lens 76, it is possible to narrow the laser beam 72 to a spot size of about 0.3 ^phi mm. The pulse width of the copper vapor laser is about 40 nsec, and the irradiation interval of the laser beam 72 is 2
The irradiation time is negligible compared to 00 μsec.

When sweeping in the width direction is performed without overlapping laser beam spots, it is necessary to set the sweep speed in the width direction to about 1.5 m / s.

Irradiation number n of the same point of the laser beam 72
In order to make the number of plural swings, the swinging device 56 is controlled so that the sweep speed in the width direction is set to about 1.5 m / s or moved by 0.3 mm at a speed of 1.5 m / s every 200 n (μsec). To do.

When the vertical scanning (longitudinal sweep) shown in FIG. 15 is performed in a state where the laser beam spots do not overlap each other, the number of irradiations N during the sweep in the width direction is multiplied by 200 μsec, and then 1.5 m is obtained. A sweep of 0.3 mm in the longitudinal direction is performed at a sweep speed of about / s.

When the laser beam spot is circular,
When 0.3 mm is swept in the longitudinal direction at a speed of about 1.5 m / s, a large non-uniformity occurs in the longitudinal direction every time the laser beam 72 is irradiated. In order to prevent the occurrence of this nonuniformity, the sweep speed is set to 1.5 m / s or less so that the laser beam spots 77 partially overlap each other in the longitudinal direction.

Ideally, if an optical system for making the beam cross-sectional shape of the laser beam 72 rectangular is placed at the exit of the optical fiber, and a laser beam spot with one side of 0.3 mm is formed, the laser beam spot of 1.5 m / s will be obtained. By sweeping in the longitudinal direction and the width direction, the laser beam 7 is swept in a certain width and length range.
2 can be irradiated multiple times.

By using such a laser beam 72 irradiating device, surface reforming and repairing in water (repairing from a tensile stress state to a compressive stress state) using a copper vapor laser with an output of about 500 W that is currently available. It can be performed.

When the surface modification work within a certain range is completed, the rod 69 is slightly contracted by the action of the air cylinder 46.
The driving device 78 is operated to operate the wire 48, and the arm rod is moved in the vertical direction along the welding line to move the laser spot swing type to a position where the surface modification work can be continued within the range where the surface modification is completed. A laser peening operation unit 26 is installed.

During this movement, the longitudinal drive motor 145
The laser peening work unit 26 housing 8
0 is moved to one end of the working unit connecting member 67.

Thereafter, the above work is repeated to perform surface modification of the weld line portion in the longitudinal direction of the core shroud 22. When the work is completed, the folding arm 24 is rotated around the horizontal fulcrum 24a via the motor 63 and the assembled gear 64 mounted in the upper case 37, and then the surface is modified in the vertical direction. The laser spot swing type laser peening operation unit 26 is moved to the welding line portion.

At that time, the drive device 78 mounted in the upper case 37 is operated to operate the wire 47,
The rod 69 is moved up and down. When the laser peening work unit 26 is set to the welding line portion in the vertical direction for performing work,
The surface modification work of the welded portion is performed in the same manner as above.

The irradiation of the laser beam 72 and the opening / closing of the shutter 84 are controlled so as to interlock with each other, and the shutter 84 is opened immediately after the irradiation of the pulsed laser beam is completed, and the image around the spot point 73 is displayed on the first reflecting mirror 86. And the second reflecting mirror 8
The images are sequentially taken through 7 and photographed by the CCD camera 58, and the surface modification work status is monitored.

When the laser beam 72 is irradiated, the ultrasonic wave generated at the spot point 73 is transmitted to the leg 61 via the shroud 34, and this is measured by the ultrasonic detector 60. If the amount of ultrasonic waves is out of the specified range, C
It is determined whether or not the spot diameter needs to be adjusted with reference to the observation result of the CD camera 58.

Next, the case where the surface of the weld line in the circumferential direction of the core shroud 34 is modified will be described. In this case, the laser peening operation unit 26 is fitted in the repair work unit attachment base 70 in a direction perpendicular to the paper surface such that the longitudinal direction of the attachment portion 54 in FIG. 15 is perpendicular to the paper surface.

When the oscillating device 56 is driven in this state, the galvanometer mirror 55 oscillates and the pulsed laser beam 7 is emitted.
The second spot point 73 scans for a certain width in the direction perpendicular to the paper surface of FIG. 15 (sweep in the width direction). The driving device 78 mounted in the upper case 37 is operated and the wire 48 is operated to move the rod 69 up and down so that the welded portion is within the scanning range.

Similar to the case of surface-modifying the weld line portion in the vertical direction, when the surface processing within a certain range is completed, the folding is performed via the motor 63 and the assembly gear 64 mounted in the upper case 37. The laser arm rocking type laser peening operation unit 26 is installed at a position where the surface modification work can be continued within the range where the surface modification is completed by rotating and moving the formula arm 24.

During this movement, the longitudinal drive motor 59 is operated to move the housing 80 along the screw screw 94 to the one end side of the working unit connecting member 67. After that, the above work is repeated to perform surface modification of the weld line portion in the circumferential direction of the core shroud 34.

When the work is completed, the drive device 78 mounted in the upper case 37 is operated, the wire 48 is operated to move the arm 47 up and down, and then the welding line portion in the circumferential direction for surface modification is formed. The laser spot swing type laser peening operation unit 26 is moved. When the laser peening operation unit 26 is set to the horizontal welding line portion where the work is performed, the surface modification work of the weld portion is performed in the same manner as described above.

According to the sixth embodiment described above, the following effects can be obtained.

That is, since the surface reforming repair (the repair changing from the tensile stress state to the compressive stress state) can be performed in water by using the copper vapor laser which is the visible light laser whose output is about 500 W, which is currently available, The work of changing the tensile stress state of the welding line and the surface of the core shroud 34 to the compressive stress state can be performed in water, and the water serves as a shielding material to reduce the exposure of the worker.

In particular, by using a laser beam, unlike the water jet peening, the reaction force generated during the surface modification work can be ignored, so that the remote handling device may have a simple structure.

Also, unlike shot blast peening, there is no generation of dust that needs to be collected. Since ultrasonic sound is generated during laser shot peening, it is possible to monitor the work status and evaluate the work results at the same time as the surface modification work. Therefore, it is not necessary to prepare a separate device for monitoring and measuring work efficiency. Can be improved.

Next, a first modification of the sixth embodiment will be described with reference to FIG.

In this modified example, a water flow 100 parallel to the emitting direction of the pulse laser beam 72 is formed in the emitting opening 99 from which the pulse laser beam 72 of the laser spot oscillation type laser peening working unit 26 is emitted. A nozzle 101 for doing so is attached and laser light is irradiated through the water flow 100 to process the inner surface of the shroud.

FIG. 16 shows a nozzle 101 for forming a water stream 100 parallel to the emission direction of the pulsed laser beam 72.
It is a figure which shows the structure of and the concept of a water flow system.

The longitudinal direction of the structure of the nozzle 101 is attached to the emission opening 99 in a direction perpendicular to the paper surface of FIG. The nozzle 1 is attached to the pump 103 installed in the control room 29 or the like.
01 is connected by a hose 105 in which a water stream 104 is created.

The hose 105 may be included in the composite cable 28. In addition, even when the hose 105 is attached to the nozzle 101, the tip of the hose 105 is inserted to the inside so that the opening portion faces the condenser lens 76. A method of setting the mounting position of the hose 105 to a position closest to the front surface of the condenser lens 76 is also possible.

The operation of the first modification is essentially the same as that of the sixth embodiment, except for the following points.

That is, the pump 1 installed in the control room 29 or the like.
The water pressurized by 03 flows through the hose 105 as a water stream 104, flows into the nozzle 101, and the condenser lens 76
Turn through the front of the. And water is the nozzle 10
1 is rectified and discharged from the rectangular opening 106 of No. 1, and is sprayed as a water stream 100 on the core shroud 116 (wall 176). The core shroud 34 is irradiated with the laser beam 72 while converging and swinging in the water stream 100. Hereinafter, the same sweeping operation as in Example 6 is performed to perform the surface modification work on the welded portion.

According to the first modified example as described above, basically the same effect as that of the sixth example is obtained, but when the surface of the core shroud 34 (wall 53) is further irradiated with the laser beam 72. Generate bubbles and fine particles of removed metal in water stream 10
By removing from the optical path of the laser beam 72 at 0,
It is possible to prevent the laser beam 72 from being absorbed or scattered by these and reducing or fluctuating the amount of light reaching the surface of the core shroud 34 (wall 53), which enables stable surface modification work and necessary laser equipment. Ability can be reduced.

Further, by blowing a new water stream onto the condenser lens assembly 76, it is possible to prevent the condenser lens assembly 76 from being thermally deformed by the laser beam 72, so that stable surface modification work can be performed for a long time. You will be able to do it.

Next, a second modification of the sixth embodiment will be described with reference to FIG. In this modification, another nozzle 111 for forming a water flow 112 perpendicular to the emission direction of the laser beam 72 is formed on a nozzle 101 for forming a water flow 100 parallel to the emission direction of the laser beam 72 of the sixth embodiment.
Is attached, and the inner surface of the shroud is processed by these.

FIG. 17 shows a nozzle 101 for forming a water flow 100 parallel to the emission direction of the laser beam 72 and another nozzle 111 for forming a water flow 112 perpendicular to the emission direction of the laser beam 72. It is a figure which shows the concept of a water flow system.

The nozzle 101 is attached to the emission opening 99 so that its longitudinal direction is perpendicular to the paper surface of FIG. Pump 1 installed in control room 29, etc.
03 and the nozzle 101 are connected by a hose 105,
The water stream 104 is made to flow in it. Each nozzle 10
The hole portions 106 and 109 of the holes 111 and 111 are opened so as to intersect each other vertically. Each hose 105, 108
May be included in the composite cable 28. Hose 10
Even when it is attached to the nozzle 101, the tip 5 is inserted into the inside so that the opening faces the direction of the collective lens 76. There is also a method in which the mounting position of the hose 105 is the position closest to the front surface of the condenser lens 76.

The operation of the second modification is essentially the same as that of the sixth embodiment, except for the following points.

That is, the pump 1 installed in the control room 29 or the like.
The water pressurized in 03 is branched and flows as a water flow 110 in the hose 108, flows into the nozzle 111, is rectified by the rectangular opening portion 109 of the nozzle 111, and the opening of the other nozzle 101 is performed. It flows out as a water flow 110 perpendicular to the water flow 100 flowing out of the section 106.

The flow velocity of one water flow 170 is set so that the core of the jet of the other water flow 100 reaches the surface of the core shroud 34 irradiated with the laser beam 72. The core beam is irradiated onto the core shroud 34 while the laser beam 72 is focused and swung in the water flow 100. Hereinafter, Example 6
The same sweeping operation as above is performed, and the surface modification work of the welded portion is performed.

According to the second modification described above, the same effect as that of the sixth embodiment can be obtained, and the core shroud 34 (wall 5) can be obtained.
By more reliably removing the bubbles and the removed metal fine particles generated when the surface of 3) is irradiated with the laser beam 72 from the optical path of the laser beam 72 by the water flow 112, the laser beam 72 is Core shroud 34 absorbed or scattered by air bubbles and removed metal particles
(Wall 53) Preventing reduction or fluctuation of the amount of light reaching the surface, stable surface modification work can be performed, and
The required laser equipment capacity can be reduced more reliably.

Next, a third modification of the sixth embodiment will be described with reference to FIG. In this modification, the water flow 100 parallel to the emission direction of the laser beam 72 shown in the second modification is used.
Laser beam 7 to the nozzle 101 for forming
Another nozzle 111 for forming a water flow 112 perpendicular to the emission direction of 2 is attached to form a suction water flow system.

FIG. 18 shows the concept of a water flow system and a nozzle 114 for forming a water flow 120 perpendicular to the emission direction of the laser beam 72 on a nozzle 101 for forming a water flow 100 parallel to the emission direction of the laser beam 72. FIG.

The longitudinal direction of the nozzle 101 is attached to the emission opening 99 in a direction perpendicular to the paper surface of FIG. The hose 105 connects the pump 103 installed in the control room 29 and the nozzle 101 with each other, and the water stream 104 flows through the hose 105. Suction device 113 installed in the control room 29 or the like
The nozzle 114 and the nozzle 114 are connected by a hose 115, and a water stream 116 flows through the hose 115. The hose 115 has a filter device 11
7 is attached. The filter device 117 may be attached to the outflow pipe portion from the suction device 113.

The opening portions 106 of the nozzles 101 and 114,
Each of 119 has a vertical hole. Each hose 1
05 and 108 may be included in the composite cable 28. Even when the hose 105 is attached to the nozzle 101, the tip of the hose 105 is inserted into the inside of the hose 105 so that the opening portion faces the condenser lens 76. Hose 105
The mounting position may be the position closest to the front surface of the condenser lens 76.

The operation of the third modification is essentially the same as that of the second modification, but is different in the following points.

That is, the suction device 113 installed in the control chamber 29 or the like is installed from the rectangular opening 119 of the nozzle 114 so that the water flow 119 is generated perpendicularly to the water flow 100 flowing out of the opening 106 of the nozzle 101. A suction water stream 116 is generated via a hose 115 coupled to the. The fine particles in the water stream 116 are removed by the filter device 117 installed in the middle of the hose 115. The core beam is irradiated onto the core shroud 34 while the laser beam 72 is focused and swung in the water flow 100. Thereafter, the same sweeping operation as in Example 6 is performed to perform the surface modification work on the welded portion.

According to the second modified example as described above, the same effect as that of the first modified example can be obtained, and in addition, the core shroud 34 can be obtained.
Bubbles generated when the surface of the (wall 53) is irradiated with the laser beam 72 and the removed metal fine particles are removed by the water stream 100.
Is removed from the optical path of the laser beam 72 with
2 is prevented from reducing or fluctuating the amount of light reaching the surface of the core shroud 34 (wall 53) by being absorbed or scattered by bubbles or removed metal fine particles, and stable surface modification work can be performed. It is possible to more reliably reduce the required laser equipment capacity. Further, by collecting the removed metal fine particles so as not to diffuse into the reactor pressure vessel, it is possible to prevent the reactor internal structure from being contaminated by the metal fine particles.

Next, a fourth modification of the sixth embodiment will be described with reference to FIG. In this modification, the light distributor 121 is provided at the exit of the beam intensity adjusting device 32 shown in the sixth embodiment.
The laser beam 72 and the plurality of laser beams 12
The optical fiber 123 is divided into two parts, each is guided to the optical fiber 123, and a plurality of optical fibers 123 are bundled and connected to the laser peening work unit 26 as an optical fiber bundle 124.

In the laser peening work unit 26,
The optical fibers 123 are arranged in a line and connected to the condensing box 125, and the laser beam 122 is condensed on the wall 53 by the lens system at the exit of the optical fiber 123 to form a spot line. By sweeping the focusing box 125 in the X- and Y-axis directions, a certain range is overlapped and laser light is emitted.

FIG. 19 is a conceptual diagram of the system of this modification. The light distributor 1 is provided at the exit of the beam intensity adjusting device 32.
21, the laser beam 72 is divided into a plurality of laser beams 122, each of which is guided to an optical fiber 123,
Optical fiber bundle 124 is formed by bundling a plurality of optical fibers 123.
The laser beam 122 is connected to the condensing box 125 of the laser peening work unit 26 to condense the laser beam 122 on the wall 53 to form a spot array to perform underwater laser repair of the inner surface of the shroud.

The laser beam 72 emitted from the beam intensity adjusting device 32 is split by the light splitting optical system to obtain a plurality of laser beams 12.
2 and each enters the optical fiber 123 via the optical system.

The optical fiber 123 is the optical fiber bundle 124.
Then, the laser peening operation unit 26 is moved to the light collecting box 125. The optical fibers 123 are arranged in a line and connected to the condensing box 125, and a condensing optical system is installed at the exit of each optical fiber 123.
22 focuses on the surface of wall 53 to form a row of laser spots 189.

The row direction of the laser spots 123 is the direction of the welding line, the amount of movement in the longitudinal direction in the embodiment is the laser spot 127 interval, and the focusing box 125 is swept in the longitudinal direction by using a screw screw and a motor. . In this case, the sweep in the width direction is not rocking, but the focusing box 1
25 is a sweep in the width direction using a screw screw and a motor.

The operation of the fourth embodiment is essentially the same as that of the sixth embodiment, but is different in the following points.

That is, since the row of laser spots 127 is formed in the direction of the welding line (longitudinal direction), the sweep range in the longitudinal direction is the distance between the laser spots 127, and the sweep in the width direction of the welding line is galvano. The difference is that instead of using a mirror, the light collecting box 125 is swept in the width direction using a screw screw, a motor, or the like. Hereinafter, the same sweeping operation as in Example 6 is performed, and the surface modification work of the welded portion is performed.

The effect similar to that of the sixth embodiment is also obtained by the fourth modification described above.

Next, a fifth modification of the sixth embodiment will be described with reference to FIG. In this modification, a condenser lens 128 is installed in the condenser box 125 shown in the sixth embodiment,
Multiple laser beams 1 emitted from the optical fiber 123
22 is formed on the surface of the wall 53 as one laser spot 188. By sweeping the light collecting box 130 in the X and Y axis directions, a certain range is weighted and the laser light is irradiated.

FIG. 20 is a conceptual diagram of the system of this modification, in which an optical distributor 121 is installed at the exit of the beam emphasis adjusting device 109, the laser beam 72 is divided into a plurality of laser beams 122, and each of them is divided into a plurality of laser beams 122. It leads to the optical fiber 123. In this case, a plurality of optical fibers 123 are bundled into an optical fiber bundle 124 to form the laser peening operation unit 2
6 to the light collecting box 130. Then, the plurality of laser beams 122 emitted from the optical fiber 123 are collected by the condenser lens 128 installed in the condenser box 130.
Is formed as one laser spot 129 on the surface of the wall 53, and underwater laser repair of the inner surface of the core shroud is performed.

The laser beam 72 emitted from the beam emphasis adjusting device 32 is split by the light splitting optical system into a plurality of laser beams 1.
22 and respectively enter the optical fiber 123 through the optical system. The optical fibers 123 are bundled and moved as an optical fiber bundle 124 to a light collecting box 130 of the laser peening operation unit 26. The optical fibers 123 are arranged in a line in the condensing box 130 and connected, and a condensing optical system is installed at the exit of each optical fiber 123.
A plurality of laser beams 122 emitted from the optical fiber 123
Is condensed at one point on the surface of the wall 53 by the condenser lens 128 to form a laser spot 127. The laser spot 127 is swept in the direction of the welding line, and the focusing box 130 is swept in the width direction using a screw and a motor.

The operation of the sixth modification is basically the same as that of the sixth embodiment, but is different in the following points.

That is, the laser spot 129 is irradiated a plurality of times, and the laser spot diameter (0.
3φmm) sweep across the width of the weld line. To provide a time delay between multiple irradiations, prepare optical fibers with different lengths. Sweep time in the width direction (200 μsec)
Since the laser irradiation time (40 nsec) can be neglected as compared with, the sweeping in the width direction is performed at a constant speed, and it is not necessary to consider the irradiation timing.

The sweeping in the direction of the welding line (longitudinal direction) is performed at a speed of 1.5 m / sec or less at a laser spot diameter (0.3 mm) or less for each sweep time interval in the width direction of the welding line. . These sweeps are performed by using a screw box, a motor, and the like for the light collecting box 186. Thereafter, the same sweeping operation as in Example 6 is performed to perform the surface modification work on the welded portion.

The same effects as those of the sixth embodiment are also obtained by the sixth modification described above.

Next, a seventh modified example of the sixth embodiment will be described. This modification is the same as the optical fiber 12 shown in the sixth embodiment.
A plurality of laser beams 122 emitted from the laser beam No. 3 are formed by the condenser lens 128 on the surface of the wall 53 so that all the laser spots are in linear contact (in the width direction of the welding line).
In this modification 7, unlike the sixth embodiment, the optical fiber 12
Three lengths are available. Then, in order to make the number of times of laser irradiation at one point plural, sweeping is performed in the width direction of the welding line by the laser spot diameter (0.3 mm) during the pulse interval.
By performing the sweeping in the direction of the welding line in the same manner as in the sixth modified example, a certain range is superimposed and the laser light is emitted.

The operation of the seventh modification is essentially the same as that of the sixth embodiment.

The same effects as those of the sixth embodiment are also obtained by this seventh modification.

Next, an eighth modification of the sixth embodiment will be described with reference to FIG. In this modification, a dichroic mirror 131 is installed at the exit of the pulse laser device 31 shown in the sixth embodiment, and two types of laser beams 132, 7 are used.
7 to the plurality of optical fibers 133 by the optical distributor 121,
Laser peening work unit 14 with optical fiber bundle
It is connected to the condenser box 135 of No. 4 and is formed as a single laser spot 138 on the surface of the wall 53 through the condenser lens 134. By sweeping the condensing box 135 in the X and Y axis directions, a certain range is overlapped and laser light is emitted.

FIG. 46 is a system conceptual diagram of the modified example 8. The dichroic mirror 131 is installed at the emission port of the pulse laser device 31, the laser beam 139 is divided into a plurality of laser beams 132 and 77, each of which is guided to the light distributor 121, and the beam is further divided into a plurality of optical fibers 133. Lead to. In this case, a plurality of optical fibers 13
3 are bundled into optical fiber bundles 136 and 137, and an optical fiber bundle for guiding a laser beam having a long wavelength is lengthened to collect the light in the focusing box 135 of the laser peening operation unit 26.
Connect to. Then, a plurality of laser beams 140 and 141 emitted from the optical fiber 133 are placed on the surface of the wall 53 by a condenser lens 134 installed in the condenser box 130.
A laser spot 138 of a point is formed, and underwater laser repair of the inner surface of the core shroud is performed.

The laser beam 139 emitted from the pulse laser device 31 is divided by the dichroic mirror 131 into laser beams 132 and 77, and the respective beams are guided to the light distributor 121. Further, each beam is divided and is incident on a plurality of optical fibers 133 via an optical system.

The optical fibers 133 are bundled into the optical fiber bundles 136 and 137, and the optical fiber bundle for guiding the laser light having a long wavelength is lengthened to make the laser peening operation unit 2
6 to the light collecting box 135.

The optical fibers 133 are arranged in a line in the condensing box 135 and connected, and a condensing optical system is installed at the exit of each optical fiber 133 to collect a plurality of laser beams 140 and 141 emitted from the optical fiber 133. Light lens 1
At 34, the laser spot 138 is focused on the surface of the wall 53 at one point.
To form. The laser spot 138 is swept in the direction of the welding line, and the focusing box 135 is swept in the width direction by using a screw screw, a motor and the like.

The operation of the eighth modification is essentially the same as that of the sixth embodiment, but is different in the following points.

That is, the laser spot 138 is irradiated a plurality of times, and the laser spot diameter (0.
3φmm) sweep across the width of the weld line. A laser beam having a short wavelength is first irradiated by a plurality of irradiations, and a laser beam having a long wavelength is irradiated after a predetermined time, so that a time delay is provided.

Therefore, an optical fiber having a long length is used for a laser beam having a long wavelength. In other words, a long optical fiber is used for delaying the irradiation time even with the same wavelength.

Since the laser irradiation time (40 nsec) can be ignored compared to the sweep time (200 μsec) in the width direction,
The sweep in the width direction is performed at a constant speed, and it is not necessary to consider the timing of irradiation. Direction of welding line (longitudinal direction)
Is the distance less than the laser spot diameter (0.3φmm) at 1.5m / sec for each sweep time interval in the width direction of the welding line.
Sweep at the following speeds.

These sweeps are carried out by using the condenser box 130 with a screw and a motor. Thereafter, the same sweeping operation as in Example 6 is performed to perform the surface modification work on the welded portion.

According to the eighth modified example described above, in addition to the same effects as in the sixth example, the laser beam utilization rate can be improved.
That is, a laser with a short wavelength has a higher light absorptivity than a laser with a longer wavelength, and the absorptivity of light increases as the temperature rises.Therefore, a laser with a short wavelength is irradiated first to raise the surface temperature, and then By irradiating a laser with a long wavelength,
The utilization effect of laser light can be improved, and the laser equipment capacity can be reduced.

Next, a ninth modification of the sixth embodiment will be described with reference to FIGS.
This will be described with reference to FIG. In this modification, a remote repair device having a link-type arm is suspended from above in a reactor pressure vessel with a wire, passed through an upper lattice plate opening in the center of the core, and installed on a core support plate. Then, the laser irradiation device attached to the tip of the link-type arm irradiates visible pulsed laser light while scanning the laser spot by using a polygon mirror in a fixed range to process the inner surface of the core shroud. To do.

FIG. 22 is a front view of a laser spot scanning type laser peening operation unit 142 using a polygon mirror. The laser peening work unit 143 is
The mounting structure 144 includes a rod 69 of the folding arm 24.
It is connected to the repair work unit mounting portion 70 at the tip.

Two end plate structures 145 arranged at intervals.
A mounting structure 144, a screw screw 146, and a slide rod 147 are coupled between the two. Slide bar 14
7 penetrates the moving plate 148, and the screw screw 14
6 are connected by a ball neck 149 of the moving plate 148.
The driving device 150 is operated to rotate the screw screw 146, and the moving plate 148 is slid using the slide rod 147 as a guide. The mount 151 is coupled to the moving plate 148 via a spring 151a.

The wheel type legs 152 attached to the attachment base 151 are pressed against the wall surface 153, and the laser peening operation unit 142 is installed. The laser light guided by the optical fiber 154 is converted into parallel rays by the combination lens 155, is guided to the polygon mirror 158 via the polarization mirrors 156 and 157, is reflected, and forms an image on the wall surface 153.

The polygon mirror 158 and the claws 159 are rotated by the actuator 160 so that each claw 1 of the cylinder 161 is rotated.
62, 159 are brought into contact with each other, and the cylinder 161 is moved against the elastic force of the spring 163 until the contact between the claws 162, 159 is released, and the irradiation of the laser beam 164 on the wall surface 153 is swept in the width direction. The sweeping in the longitudinal direction is performed by rotating the screw screw 146 with the driving device 150 and moving the moving plate 148 to rotate the leg 152 with wheels on the wall surface 153.

FIG. 23 is a side view of a laser spot scanning type laser peening operation unit 142 using a polygon mirror, and FIGS. 24 and 25 are detailed conceptual diagrams of a laser spot scanning mechanism section using a polygon mirror.

The polygon mirror 158 and the claw 159 are rotated by the actuator 160. With this rotation, the cylinder 161 is pulled up while the claws 159 and 162 are in contact with each other, and when the claws 159 and 162 are separated from each other, the cylinder 161 is returned to the original position by the spring 163.

On the other hand, the laser beam 164 has a structure in which irradiation can be switched ON / OFF by a Faraday rotator, a shutter or the like on the side of a light source (not shown), and the laser beam 164 has a polarization mirror 156, a mirror 157 and a polygon mirror 158. It is reflected by and is irradiated on the wall surface 153.

The laser beam 164 not reflected by the polarization mirror 156 is absorbed by the beam damper 165. Although not shown, the beam damper 165 is constantly cooled by a cooler.

The operation of the ninth modification is essentially the same as that of the sixth embodiment, but the polygon mirror of the polygon mirror is rotated at a constant angular velocity to perform saw-tooth sweeping, and the mirror 157 is synchronized. The difference is that a high-speed homing operation is performed.

According to the ninth modification described above, in addition to the same effect as that of the sixth embodiment, the sweep speed in the width direction of the welding line (the rotational angular speed of the polygon mirror is obtained by using the polygon mirror. ) Is constant, and surface modification can be performed by sweeping at a sweep speed along the weld line (sweep speed in the longitudinal direction) and irradiating the laser within a fixed range multiple times, so the control system is simple. Therefore, it is not necessary to cause a large moment change in the equipment, which is advantageous in terms of the strength of the equipment. In the above sweeping method, the row of laser irradiation points is inclined with respect to the welding line, but there is no problem in operation.

[0202]

As described in detail above, according to the present invention, the preventive maintenance and repair of the internal structure of the reactor can be achieved.
A processing method that can improve residual stress on the surface of structural materials, remove cracks, and remove clads, and is simple, high-quality, does not affect peripheral equipment, and has good applicability to narrow spaces.
Can be provided .

[Brief description of drawings]

FIG. 1 shows Example 1 of the present invention, and is a diagram in the case of irradiating a laser beam to improve residual stress.

FIG. 2 is a diagram showing a concept of a laser beam irradiation method in the embodiment.

FIG. 3 is a diagram showing a typical laser beam irradiation method.

FIG. 4 is a diagram showing an improved laser beam irradiation method.

FIG. 5 is a diagram showing an irradiation method when an irradiation spot shape is changed.

FIG. 6 is a diagram showing an irradiation method when an irradiation spot shape is changed.

FIG. 7 is a diagram showing Example 2 of the present invention, in which a laser is irradiated to remove cracks.

FIG. 8 is a diagram showing Example 4 of the present invention, in which a laser is irradiated to remove the clad.

FIG. 9 is a flowchart showing a work procedure in the fifth embodiment of the present invention.

FIG. 10 is a diagram showing a distribution of irradiation beam superimposition rates in the example.

FIG. 11 shows Example 6 of the present invention, and is a diagram showing a state where a shroud inner surface is repaired by laser irradiation.

FIG. 12 shows Example 6 of the present invention, and is a diagram showing a state of repairing the inner surface of the shroud by irradiating a laser.

FIG. 13 is a view showing a state in which jigs and tools are attached to the shroud inner surface repair robot according to the embodiment.

FIG. 14 is a diagram showing a shroud inner surface repair robot according to the embodiment.

FIG. 15 is a diagram showing a configuration of a laser peening operation unit according to the same embodiment.

FIG. 16 is a diagram showing how a water stream is generated in the laser light emitting direction according to the embodiment.

FIG. 17 is a diagram showing a state of water flow generation in the laser light emission direction and the vertical direction according to the example.

FIG. 18 is a view showing a method of water flow emission in the laser light emission direction and a water flow suction direction in the vertical direction according to the embodiment.

FIG. 19 is a view showing a simultaneous irradiation method of a plurality of laser spots according to the same embodiment.

FIG. 20 is a diagram showing a method of simultaneously irradiating a single point with a plurality of laser beams according to the same embodiment.

FIG. 21 is a diagram showing a method of simultaneously irradiating one point with a plurality of laser beams having different wavelengths according to the example.

FIG. 22 is a front view showing a laser peening operation unit using a polygon mirror according to the embodiment.

23 is a cross-sectional view taken along the line AA of FIG.

FIG. 24 is a diagram showing details of a laser spot scanning mechanism unit using a polygon mirror according to the same embodiment.

25 is a cross-sectional view taken along the line BB of FIG.

[Explanation of symbols]

1 Reactor pressure vessel 2 cooling water 3 laser beam 4 optical fiber 5 Reactor internals 6 pulse laser device 7 Incident lens 8 Condensing lens 9 reactor pit 10 irradiation spots 11 Construction unit area 12 Processing head 13 CCD camera 14 cracks 15 monitors 16 signal cable 17 Clad 21 Reactor pressure vessel 22 Upper lattice plate 23 Core Support Plate 24 foldable arm 26 Laser peening work unit 28 composite cable 29 Control room 30 control panel 31 pulse laser device 32 Beam intensity adjuster 33 Jet pump 34 Shroud 35 Annulus 36 Lower furnace chamber 37 Upper case 38 Lower case 39 wire 40 Opening 41 Hole 42 Control rod drive housing 43 Upper case guide device 44 Lower case guide device 45 fixing legs 46 air cylinder 48 wires 49 Balancer 50 Repair work unit transfer device 52 Repair work unit 53 walls 54 Attachment 55 galvano mirror 56 Rocking device 57 Spot diameter adjustment mechanism 58 CCD camera 59 Longitudinal drive motor 60 ultrasonic detector 61 legs 62 reactor pit 63 motor 64 sets of gears 65 Installation guide device 67 Connection member 68 Upper lattice plate lower chamber 69 arm 70 Repair work unit mount 72 laser light 73 spot points 76 Focusing lens 77 laser light 78 Pulley 79 signal cable 80 housing 84 shutter 86 1st reflector 87 Second reflector 94 screw screw 99 exit opening 100 water streams 101 nozzles 103 pump 104 water current 105 hose 106 hole 108 hose 109 hole 110 water flow 111 nozzles 112 water current 114 nozzles 115 hose 116 water flow 117 Filter device 119 hole 120 water flow 121 Optical distributor 122 laser light 123 optical fiber 124 Optical fiber bundle 125 light collection box 127 laser spot 128 condensing lens 129 laser spot 130 Focusing box 131 dichroic mirror 132 laser light 133 optical fiber 135 Focusing box 134 Condensing lens 136 optical fiber bundle 137 Optical fiber bundle 138 laser spot 139 laser light 140 laser light 141 laser light 153 wall 156 Polarizing mirror 157 mirror 158 polygon mirror 159 claws 160 actuator 161 cylinder 162 nails 163 spring 164 laser light 165 beam damper

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yuji Sano 8 Shinsita-cho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture Yokohama office (72) Inventor Naruhiko Mukai 8 Shinsita-cho, Isogo-ku, Yokohama-shi, Kanagawa Toshiba Corporation Inside the Yokohama Works (72) Inventor Nobutada Aoki 8 Shinsitata-cho, Isogo-ku, Yokohama-shi, Kanagawa Toshiba Corporation Inside the Yokohama Works (72) Inventor Main Tax 8 Shinsita-cho, Isogo-ku, Yokohama-shi, Kanagawa Toshiba Corporation Inside the Yokohama Works (72) Inventor Muneyoshi Kikunaga 66-2 Horikawa-cho, Sachi-ku, Kawasaki-shi, Kanagawa Toshiba Engineering Co., Ltd. (56) References JP-A-5-80187 (JP, A) JP-A-7-246483 (JP, A ) JP-A-7-248397 (JP, A) JP-B-1-45039 (JP, B2) JP-A-5-503738 (JP, A) (58)査the field (Int.Cl. ^7, DB name) B23K 26/00 - 26/42 G21C 19/02

Claims (4)

(57) [Claims] 1. A surface of a structure immersed in cooling water
Irradiates a high-power, short-pulse laser beam with a visible wavelength
To improve the residual stress of the material on the surface of the structure and to remove cracks.
Or an underwater laser processing method for removing the clad,
Detects cracks on the material surface of the internal structure of the reactor filled with cooling water, and the pulse width is 1 for this crack.
With a laser beam having a visible wavelength of less than 00 nsec, with a peak output per pulse of 0.1 to 10 GW / cm ² ,
An underwater laser processing method characterized by irradiating while observing a situation where a crack is removed by ablation to remove the crack. 2. The method according to claim 1, wherein after the cracks generated on the surface of the internal structure of the nuclear reactor are removed, the stress on the surface of the material after the cracks are removed is improved by performing the treatment according to claim 1. Underwater laser processing method. 3. The irradiation of the underwater laser beam according to claim 1 improves the stress on the material surface while removing the clad accumulated on the surface of the internal structure of the reactor filled with cooling water. An underwater laser processing method characterized by performing. 4. A laser beam irradiation on the surface of the material of the inner structure of the furnace was filled with coolant atoms, claims 1 to 3
When the material surface stress improvement, crack removal, or clad removal described above is performed, the overall construction range, construction unit area, and construction conditions are created based on the flaw detection inspection and surface condition inspection that were performed in advance, and the structural drawing. Underwater laser processing method characterized by automatically controlling according to the map.