JPH07280987A - Method and apparatus for preventing deterioration of multiplex metal pipe - Google Patents

Abstract

PURPOSE:To provide an apparatus for preventing deterioration of a multiplex metal pipe in which residual stress is relaxed at the welded parts of a nozzle having a thermal sleeve, the sleeve and a pipe, and the corrosive environment is improved by decontaminating the inner surface of an annular gap at a dead end. CONSTITUTION:An annular injection head 3 is fixed to a pipe 8 in furnace, and water 23 is jetted at a pressure as high as 40-1000MPa toward the rearmost part of an annular gap 12. When a cavitation bubble generated in the turbulence of jet water 23 collapses, collapsing pressure of about 1000MPa is produced to cause peening action and thereby the inner surface of the annular gap 12 is cleaned, the surface layer metal is machined plastically thus forming residual compressive stress. Since the residual stress and corrosive environment are improved simultaneously, stress corrosion cracking is prevented and radioactive cruds and contaminants are removed thus protecting an inspector against exposure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a deterioration preventive maintenance method and a deterioration preventive maintenance apparatus for multiple metal pipes such as nozzles, and in particular, it is attached to a pressure vessel of a boiling water reactor plant which has already started operation. The tensile residual stress existing on the inner surface side of the welded portion of the nozzle and the safe end with the thermal sleeve and the welded portion of the safe end with the thermal sleeve and the external piping is relaxed, and the double formed by the nozzle and the thermal sleeve. The present invention relates to a means for decontaminating the inside of a gap in a blind alley having a cylindrical structure.

[0002]

2. Description of the Related Art As a decontamination device for a double metal tube, there is, for example, the device described in JP-A-62-289800.
In this conventional technique, a circulation flow is formed in the annular space from a plurality of ejection nozzles of the ejection head, and the substances accumulated in the annular space are discharged by the circulation flow. More specifically, a method has been proposed in which the position of the injection nozzle is tilted in the exercise direction in order to avoid a dead water region where the flow of injected water is bad and pollutants do not stay in the dead water region and are not discharged. ing.

On the other hand, as a method for improving the residual stress of a double metal tube, there is, for example, the method described in JP-A-2-28428. In this prior art, while the cooling water is present inside the double metal pipe, the partial water flows are alternately jetted to the circumferentially separated positions of the annular space formed between the nozzle and the thermal sleeve. The nozzle surrounding the annular space was heated to give a temperature difference in the heat direction to the nozzle wall, and the compressive stress remained when completely cooled.

[0004]

In the boiling water reactor plant constructed at the beginning of nuclear power generation,
A safe end of a nozzle with a thermal sleeve made of SUS304 stainless steel was welded to a nozzle of low alloy steel and used. SUS304 stainless steel is sensitized by increasing the susceptibility to stress corrosion cracking due to welding heat.

When sensitization, residual tensile stress and corrosive environment overlap, stress corrosion cracking is more likely to occur. Further, since the annular gap formed by the thermal sleeve and the nozzle is a dead end, the reactor water here becomes stagnant water. Therefore, during long-term use, corrosion products and the like accumulate, and the environment becomes severe as a corrosive environment. As a result, there has been a problem that the stress corrosion cracking potential increases as the operating period becomes longer.

In the decontamination apparatus for a double metal tube proposed in JP-A-62-289800, the flow velocity of the jet flow from the jet nozzle is 7 m / s to 20 m / s at most.
Although the decontamination effect of pollutants, which become a corrosive environment, can be obtained for some time, it was necessary to re-work to improve the susceptibility to stress corrosion cracking.

In the method of improving the residual stress of a double metal pipe proposed in the above-mentioned Japanese Patent Laid-Open No. 2-28428, in order to avoid a stagnant region of the cooling water when heating from outside the double metal pipe by the heating means, Although partial water streams are jetted alternately at positions distant from each other in the circumferential direction of the space, means such as a heating coil for heating the double metal pipe from the outside is required, and it takes time to dispose the heating power source. I had to prepare.

An object of the present invention is to weld a nozzle formed on a side wall of a vessel such as a reactor pressure vessel and a safe end with at least one thermal sleeve, the innermost thermal sleeve of the safe end and the above-mentioned thermal sleeve. It includes a welded portion with a pipe in the container and a welded portion with the safe end and an external pipe, and forms a blind path between the nozzle and the safe end and the pipe in the container and / or the thermal sleeve. It is an object of the present invention to provide a deterioration preventive maintenance method and a deterioration preventive maintenance device which can simultaneously improve the susceptibility of stress corrosion cracking and decontaminate a pollutant which becomes a corrosive environment for a multi-metal tube having at least one annular gap.

[0009]

In order to achieve the above object, the present invention provides a welded portion between a nozzle formed on a side wall of a container and a safe end provided with at least one thermal sleeve, the innermost side of the safe end. At least including a weld between the thermal sleeve and the pipe in the container and a weld between the safe end and the external pipe, and forming a blind path between the nozzle and the safe end and the pipe and / or the thermal sleeve in the container. In a deterioration preventive maintenance method for a multi-metal pipe having one annular gap, at the deepest part of at least one annular gap forming a blind alley from a plurality of injection nozzles of an annular ejection head mounted so as to surround the pipe in the container. A high-pressure pure water jet with a pre-injection pressure of 40 MPa to 100 MPa is ejected toward the cavitation bubbles to form an annular gap. It proposes a degradation preventive maintenance method for multiplex metal tube to change the residual stress to the composition processing the surface layer metal of each weld compressive stress as well as decontaminating surfaces.

In the method for preventing and maintaining the deterioration of a multi-metal pipe, first, high-pressure pure water jets are jetted from all of the plurality of jet nozzles of the annular jet head, and then the number of jet nozzles that jet high-pressure pure water jets. It is desirable to repeat injection of the high-pressure pure water jet while gradually reducing

Also in the method of preventing and maintaining the deterioration of the multi-metal pipe, the water in the nozzle with the thermal sleeve is made to flow by the pump attached to the container, and high-frequency power is supplied to the heating coil installed on the outer periphery of the welded portion to supply the inner surface of the welded portion. Is heated until sufficient thermal strain occurs for tensile yielding, immediately stop heating, stop the pump after the weld is completely cooled,
After that, each of the above procedures may be executed.

In any of the multi-metal tube deterioration preventive maintenance methods, it is also possible to mix the polishing agent with pure water and then pressurize the high-pressure pure water.

In any of the multi-metal pipe deterioration preventive maintenance methods, actually, return water from at least one annular gap forming a blind alley is collected, and the collected return water is purified to obtain high-pressure pure water. Will be supplied again.

In order to achieve the above object, the present invention also provides a welded portion between a nozzle formed on a side wall of a container and a safe end provided with at least one thermal sleeve, and an innermost thermal sleeve of the safe end. At least one annular gap that includes a weld with a pipe in the container and a weld with a safe end and an external pipe, and forms a blind path between the nozzle and the safe end and the pipe and / or the thermal sleeve in the container. In a deterioration preventive maintenance device for a multi-metal tube having a pure water tank for storing pure water, a means for pressurizing pure water supplied from the pure water tank, and a plurality of jets mounted so as to surround the tube in the container. The pre-injection pressure supplied from the pressurizing means is 40MP toward the deepest part of at least one annular gap having a nozzle and forming a blind alley.
a Annular jet head for injecting high-pressure pure water jet of a to 100 MPa to generate cavitation bubbles, means for sucking and collecting return water from at least one annular gap forming a blind alley, and purifying the recovered return water The present invention proposes a deterioration preventive maintenance device for a multi-metal pipe, which is provided with a means for returning to a pure water tank.

In the multi-metal pipe deterioration preventive maintenance device, first, the high-pressure pure water jet is jetted from all of the plurality of jet nozzles of the annular jet head, and then the number of jet nozzles for jetting the high-pressure pure water jet is gradually reduced. Meanwhile, it is possible to provide a control means for controlling the ejection head so as to repeat the ejection of the high-pressure pure water jet.

In the deterioration preventive maintenance device for a multi-metal pipe, a heating coil is installed on the outer periphery of the welded portion and heats until the inner surface of the welded portion has sufficient thermal strain for tensile yielding.
A heating power supply for supplying high-frequency power to the heating coil, a pump attached to the container for flowing water in the nozzle with a thermal sleeve, and heated until the inner surface of the welded part has sufficient thermal strain to yield and yield. At this point, heating may be stopped immediately, and a control means for stopping the pump after the weld is completely cooled may be additionally installed.

In any multi-metal pipe deterioration preventive maintenance device, the means for sucking and collecting the return water is a suction head having a plurality of suction pipes mounted so as to surround the pipes in the container together with the jet head. A chamber is provided which is abutted against the inner wall of the container near the nozzle and has a closed space for suction on the nozzle side.

Further, any of the multi-metal pipe deterioration preventive maintenance devices can be provided with a means for mixing an abrasive into the pure water supplied from the pure water tank before pressurization.

[0019]

In the present invention, the pre-injection pressure is 40 MPa to 100 MPa from the plurality of injection nozzles of the annular injection head mounted so as to surround the pipe in the container toward the deepest part of at least one annular gap forming the blind alley. Inject high-pressure pure water jet of to generate cavitation bubbles,
Since the inner surface of the annular gap is decontaminated and the surface layer metal of each weld is processed to change the residual stress into a compressive stress, the high-pressure pure water jet not only reaches the inner part of the annular gap but also disturbs inside the gap. A flow is generated and turbulence-induced cavitation bubbles are generated. When the cavitation bubbles are destroyed, extremely high pressure is generated, so that the decontamination of the annular gap and the improvement of the residual stress of the welded portion are simultaneously achieved.

First, a high-pressure pure water jet is jetted from all of the plurality of jet nozzles of the annular jet head, and then,
Excessive cleaning can be prevented by repeating the injection of the high-pressure pure water jet while sequentially reducing the number of the injection nozzles for ejecting the high-pressure pure water jet. In other words, if a high-pressure pure water jet is suddenly sprayed onto a target area that is heavily contaminated with a small number of spray nozzles, the contaminants that have peeled off may act as abrasives and abrade the inner surface of the annular gap. When the number of jet nozzles for jetting the jets is gradually reduced, the separated contaminants are collected together with the return water in each cleaning step, and there is no concern that the pollutant may become an abrasive and adversely affect.

The water in the nozzle with the thermal sleeve is made to flow by the pump attached to the container, and high-frequency power is supplied to the heating coil installed on the outer periphery of the weld to generate thermal strain sufficient for tensile yielding of the inner surface of the weld. Heating, stop heating immediately, stop the pump after the weld is completely cooled, and then perform each of the above steps, the inner surface causes tensile yielding in the thickness direction of the inner and outer surfaces. A sufficient temperature difference occurs. After cooling completely, high-pressure pure water jet is injected again into the gap and cavitation bubble treatment is performed, so that compressive residual stress can be generated more reliably on the inner surface of the welded portion, and the residual stress is improved to improve the residual stress. The reliability can be further enhanced.

By mixing the polishing agent in pure water and then raising the pressure to the high-pressure pure water, various decontamination effects can be obtained by selecting the polishing agent.

When the return water from the annular gap forming the dead end is collected, the return water is purified and re-supplied as high-pressure pure water, an increase in the amount of contaminants is suppressed.

A pure water tank for storing pure water, a means for pressurizing the pure water supplied from the pure water tank, and a plurality of injection nozzles mounted so as to surround the pipe in the container form a dead end. The pre-injection pressure supplied from the pressurizing means toward the deepest part of at least one annular gap is 40 MPa to 10 MPa.
An annular jet head for injecting a high-pressure pure water jet of 0 MPa to generate cavitation bubbles, a means for sucking and collecting return water from at least one annular gap forming a blind alley, and purifying the recovered return water for purification. According to the deterioration preventive maintenance device for a multi-metal pipe equipped with means for returning to the water tank, the high-pressure pure water jet not only reaches the inner part of the annular gap, but also causes turbulence inside the gap, causing turbulence-induced cavitation. Generate bubbles. When the cavitation bubbles are destroyed, extremely high pressure is generated, so that the decontamination of the annular gap and the improvement of the residual stress of the welded portion are simultaneously achieved.

First, high-pressure pure water jets are jetted from all of the plurality of jet nozzles of the annular jet head, and then the jetting of high-pressure pure water jets is repeated while sequentially reducing the number of jet nozzles for jetting high-pressure pure water jets. When the control means for controlling the ejection head is provided, excessive cleaning can be prevented. In other words, when a high-pressure pure water jet is suddenly jetted to a target area that is heavily contaminated with a small number of jet nozzles,
There is a risk that the peeled contaminants will act as an abrasive and abrade the inner surface of the annular gap, but if the number of injection nozzles that eject high-pressure pure water jets is gradually reduced, the peeled contaminants will be removed in each cleaning step. Since it is collected together with the return water at, there is no concern that it will become an abrasive and adversely affect.

A heating coil installed on the outer periphery of the welded part and heating until the inner surface of the welded part is subjected to sufficient thermal strain for tensile yielding, and a heating power supply for supplying high-frequency power to the heating coil.
A pump that is attached to the container to flow the water in the nozzle with a thermal sleeve, and immediately stops heating when the inner surface of the welded part is heated until sufficient thermal strain occurs for tensile yielding, and the welded part is completely By additionally installing control means for cooling the pump and then stopping the pump, compressive residual stress can be generated more reliably on the inner surface of the welded portion, the residual stress can be improved, and the reliability of the welded portion can be further increased. .

As a means for sucking and collecting the return water, a suction head having a plurality of suction pipes attached so as to surround the pipe in the container together with the jet head may be included, or the suction head may be brought into contact with the inner wall of the container near the nozzle. If you include a chamber that is a closed space that should be sucked in, the return water from the annular gap that is a blind alley is collected, and the return water is purified,
It will be supplied again as high-pressure pure water, and an increase in the amount of contaminants will be suppressed. Especially when the chamber method is adopted,
It is possible to prevent contamination of the large amount of water already existing in the container with contaminants, and to significantly reduce the contamination of the large amount of water.

Further, if a means for mixing an abrasive with the pure water before being pressurized supplied from the pure water tank is provided, the abrasive-containing high pressure pure water jet exerts a grinding action on the inner surface of the multi-metal tube. , The decontamination effect is enhanced.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a preventive maintenance system for deterioration of a multi-metal pipe according to the present invention, in order to prevent deterioration of a double metal pipe provided in a pressure vessel of a nuclear power plant, that is, a nozzle with a sleeve, after the start of operation of the power plant. It is a system diagram which shows the whole structure to which one Example is applied. In FIG. 1, a shroud 34 surrounds the reactor core in the pressure vessel 1 of the reactor.
Are arranged and the reactor water 29 is filled to a predetermined height. Nozzle 6 targeted for deterioration preventive maintenance according to the present invention
Are formed so as to project from, for example, the lower side wall of the pressure vessel 1.

FIG. 2 is an enlarged partial sectional view showing the arrangement of parts and the flow of fluid of the deterioration preventive maintenance device around the nozzle with sleeve in the embodiment of FIG. In FIG.
The nozzle 6 has a sleeve 31a at the safe end 3
One end of 1 is fixed by a nozzle weld 7. The furnace tube 8 is fixed to the sleeve 31a by a sleeve welded portion 9. At the other end of the safe end 31, the pipe 10
Are fixed by the pipe weld 11.

Returning to FIG. 1, the return water from the jet head 3 of high-pressure pure water and the annular gap 12 formed between the sleeve 31a and the nozzle 6 is sucked around the furnace tube 8. The suction head 4 is attached. Annular gap 1
Details of 2 will be described later. The service platform 2 installed on the flange 1a of the pressure vessel 1 has a remote control device 5
Is placed. The remote control device 5 and the ejection head 3 are
The high pressure hose 17 is connected, and the remote control device 5 and the suction head 4 are connected by a suction hose 20.
The pure water from the pure water tank 18 shown on the left side of FIG. 1 has its flow rate adjusted by the high-pressure pure water injection device 32 controlled by the injection control device 19 and is pressurized by the high-pressure pump 15 to become high-pressure pure water 16. , And is supplied to the ejection head 3 via the remote control device 5. On the other hand, the return water 24 from the suction head 4
Is returned to the water treatment device 21 via the remote control device 5, and under the control of the water treatment control device 22, the water treatment device 2
It is reformed into pure water by 1 and returned to the pure water tank 18.
The high-pressure pump 15, the water treatment control device 22 and the like are integrally managed and controlled by the comprehensive control device 33.

In the embodiment of FIG. 1, the integrated control device 3
The heating control device 28 operating under the control of No. 3, the heating power source 27, and the heating coil 25 connected to the heating power source 27 by the cable 26 and arranged around the nozzle 6 are also shown. It is not always necessary to implement the invention. The reason will be described later.

FIG. 3 is a cross-sectional view showing a cross section perpendicular to the axis of the nozzle with sleeve which is the object of deterioration prevention in the embodiments of FIGS. 1 and 2. The annular gap 12 formed between the nozzle 6 and the furnace tube 8 and between the safe end 31 and the sleeve 31a has a blind passage on the pipe 10 side, and its cross section AA is shown in FIG. As such, it is annular. The ejection head 3 and the suction head 4 are installed so as to surround the furnace inner tube 8.

FIG. 4 is a diagram showing an example of the arrangement of the injection nozzle and the suction pipe of the deterioration preventive maintenance device as seen from the direction perpendicular to the axis of the sleeve-equipped nozzle which is the object of deterioration prevention in the embodiment of FIG. is there. The jet head 3 includes a jet nozzle 13
a, 13b, 13c, 13d, 13e, 13f are provided, and the suction head 4 has suction tubes 14a, 14b, 14
c, 14d, 14e and 14f are provided. High-pressure pure water 16 is sent to the jet head 3 from a high-pressure pump 15 via a high-pressure hose 17. Injection nozzle 13 and suction pipe 14
In the embodiment shown in FIG. 4, there are six, but the number is increased or decreased depending on the size of the annular gap 12.

In order to prevent deterioration of the sleeve-equipped nozzle, first, the cover of the pressure vessel, the steam dryer, and the steam separator (not shown) are removed. Next, the service platform 2 is placed on the flange 1a of the pressure vessel 1, and the remote operation device 5 in which the jet head 3 and the suction head 4 are suspended is installed on the service platform 2. FIG. 1 shows this state. The remote control device 5 may be installed on a refueling cart (not shown).

Pure water is supplied to the high pressure pump 15 from a pure water tank 18. At that time, the ejection head 3, the ejection nozzle 13, and the high-pressure pump 15 are controlled by the ejection control device 19. The water sucked from the suction pipe 14 and collected in the suction head 4 is sent to the water treatment device 21 via the suction hose 20 and separated into waste and pure water. The separated pure water is returned to the pure water tank 18, and the waste is sent to waste treatment. The suction head 4 and the water treatment device 21 are controlled by the water treatment control device 22.

For preventive maintenance of deterioration of the nozzle with sleeve, for example, 4 from all the injection nozzles 13a to 13f.
Very high pressure jet water 23 of about 0 to 100 MPa is jetted toward the deepest part of the annular gap 12. Such high-pressure pure water has a flow velocity at the time of injection of, for example, 20 m / s to 35 m / s.
It will be about. The return water 24 from the annular gap 12, which becomes sewage, is sucked into the suction pipe 14, is sent from the suction head 4 to the water treatment device 21 via the suction hose 20, and is treated. Injection and water treatment are continued until the return water 24 is no longer polluted.

When the return water 24 is not contaminated even if it is jetted from all the jet nozzles 13, next, the jet nozzles 13
Jet water 22 from a, 13c, 13e with annular gap 1
It jets toward the deepest part of 2 and continues until the return water 24 is no longer polluted.

Further, jet water 22 is jetted toward the deepest part of the annular gap 12 from the jet nozzle 13a and the jet nozzle 13d facing the jet nozzle 13a, and continues until the return water 24 is no longer polluted. Next, the jet water 23 is discharged from the jet nozzle 13b and the jet nozzle 13e facing the jet nozzle 13b.
Is injected toward the deepest part of the annular gap 12, and is continued until the return water 24 is no longer polluted. Finally, the injection nozzle 13
Jet water 23 is jetted toward the deepest part of the annular gap 12 from c and the jet nozzle 13f facing the jet nozzle 13f, and continues until the return water 24 is no longer polluted. The combination of the injection nozzles and the injection order are appropriately selected according to the arrangement of the injection nozzles 13, the clearance dimension of the annular clearance 12, and the depth dimension.

According to the embodiment shown in FIGS. 1 to 4, first, the jet water 23 jetted from all the jet nozzles 13 is discharged.
However, since it interferes with the return water 24 and the speed is reduced, the cleaning effect is weak and light dirt is cleaned. When the number of jet nozzles is gradually reduced, the interference between the jet water 23 and the return water 24 is reduced, the cleaning effect is enhanced, and cavitation bubbles are generated in the turbulent flow of the jet water 23. Since the collapse pressure when the bubbles collapse is about 1000 MPa, so-called peening action occurs, the inner surface of the annular gap 12 is washed, and the surface layer metal is plastically worked to form compressive residual stress. This compressive residual stress is
Not only the nozzle welded portion 7 and the pipe welded portion 11, which have high stress corrosion cracking susceptibility due to welding, but also the annular gap 12
Is generated over the entire inner surface of the side. Further, the inside of the annular gap 12 is cleaned to create a clean environment.

Generation of this compressive residual stress and improvement to a clean environment can prevent stress corrosion cracking. In addition, since radioactive contaminants are cleaned, it is also effective in reducing the exposure of inspectors during regular inspections. Further, when the jet water 23 is sequentially sprayed on the target portion that is heavily soiled as in the embodiment of FIG. 1, excessive cleaning can be prevented. That is, a small number of the injection nozzles 1 are attached to the target site that is heavily soiled.
When the jet water 23 is suddenly sprayed in No. 3, the exfoliated oxide may serve as an abrasive and abrade the inner surface of the annular gap 12, but in the embodiment of FIG. In this case, since it is collected together with the return water 24, there is no fear of becoming an abrasive and having an adverse effect.

FIG. 5 is a partial sectional view showing the arrangement of parts and the fluid flow of the deterioration preventive maintenance device around the sleeve nozzle in the embodiment of the deterioration preventive maintenance device for a multi-metal tube, that is, a nozzle having a plurality of sleeves according to the present invention. is there. Figure 1
The embodiment shown in FIG. 4 relates to a nozzle having a single sleeve, whereas the embodiment shown in FIG. 5 has a plurality of sleeves, that is, a sleeve 31a connected to the furnace tube 8 and a sleeve 31b having one opening. It is an example about the nozzle 6 provided with the double sleeve which consists of. In the embodiment of FIG. 5, since the sleeve is double, the annular gap is also double.
2a and 12b. Therefore, in the ejection head 3,
Injection nozzles 13a ₁ , 13a ₂ , 13 for the annular gap 12a
a _3, 13a _4, ... provided with a nozzle 13b ₁ of the annular gap _{12b, 13b 2, 13b 3,} 13b 4, ... a is provided.

The procedure for preventive maintenance of deterioration of the nozzle with sleeve is the same as that of the embodiment shown in FIGS. 1 to 4, and will not be repeated here.

In the embodiment of FIG. 5, the annular gap 12a
And 12b each have a dedicated injection nozzle 13a
And 13b are provided, it is possible to reliably inject high-pressure jet water into the annular gaps 12a and 12b and prevent stress corrosion cracking. In addition, since radioactive contaminants are thoroughly washed, it is also effective in reducing the exposure of inspectors during regular inspections.

FIG. 6 is a partial cross-sectional view showing the arrangement of parts and the fluid flow of the deterioration preventive maintenance device around the sleeve nozzle in the embodiment of the chamber type deterioration prevention maintenance device for the double metal pipe, that is, the sleeve nozzle according to the present invention. Is. In the embodiment of FIG. 6, the chamber 30 is installed so as to surround the furnace tube 8. A support 35 may be interposed between the shroud 34 and the chamber 30 in order to prevent the chamber 30 from moving during deterioration preventive maintenance of the sleeved nozzle.

In the embodiment of FIG. 6, since the chamber 30 is installed so as to surround the furnace tube 8 and a closed space is formed around the annular gap 12, the suction hose is drawn from the space inside the chamber 30. It suffices if the return water 24 is sucked by 20 and, unlike the embodiment of FIGS. 1 to 5, the plurality of suction pipes 14 are unnecessary.

The procedure for preventive maintenance of deterioration of the nozzle with sleeve is the same as that of the embodiment shown in FIGS. 1 to 4 and will not be repeated here.

In the embodiment of FIG. 6, the above-mentioned FIGS.
Similar to the example of 1, stress corrosion cracking can be prevented. Also,
Since radioactive contaminants are thoroughly washed, it is also effective in reducing the exposure of inspectors during regular inspections. In particular, while the structure of the return water suction side is simplified, the return water capturing efficiency is increased and the reactor water can be installed without being polluted.

In each of the above-mentioned embodiments, it is possible to put an abrasive in the jet water 23. When the abrasive is put into the jet water 23 as described above, the cleaning effect of the sleeve-equipped nozzle to which contaminants are firmly attached can be enhanced.

In each of the above embodiments, jet water 23
Since cavitation bubbles are generated in the turbulent flow and the collapse pressure when the bubbles collapse is about 1000 MPa, a so-called peening action occurs, the inner surface of the annular gap 12 is cleaned, and the surface layer metal is removed. It is plastically worked and a compressive residual stress is formed. Therefore, although the susceptibility to stress corrosion cracking is sufficiently suppressed only by the turbulent flow of the jet water 23, the heating coil 25 for high frequency induction heating is attached to the outer peripheral portions of the nozzle welded portion 7 and the pipe welded portion 11 for induction heating. When used together with the conventional maintenance method described above, the effect is further enhanced.

Next, referring again to FIGS. 1 and 2, an embodiment in which a heating coil 25 for high frequency induction heating is attached to the outer peripheral portions of the nozzle welded portion 7 and the pipe welded portion 11 will be described. The heating coil 25 is connected to a heating power supply 27 and a heating control device 28 via a cable 26.

With this system configuration, first, the reactor water 29 in the pipe 10 is circulated by a pump attached to the reactor (not shown). Next, high-pressure pure water 16 is guided to the jet head 4, and jet water 23 is jetted from the jet nozzle 13 toward the deepest part of the annular gap 12. Return water 24 from the annular gap 12 is sucked into the suction pipe 14, and is sucked from the suction head 4 to the suction hose 2
It is sent to the water treatment device 21 via 0 and treated. In parallel with the jetting of the jet water 23, high-frequency power is supplied to the heating coil 25, and the outer surface of the sleeve nozzle 6 is induction-heated. At this time, since the inside of the annular gap 12 is cooled by the jet water 23 and the inside of the pipe welded portion 11 is cooled by the circulating reactor water 29, a large temperature difference is easily generated on the inner and outer surfaces of the plate thickness. , Tensile stress is generated on the inner surface. The heating is stopped when the tensile stress exceeds the yield point. After that, when the temperature difference between the inner and outer surfaces is completely cooled, the circulation of the reactor water 29 and the jet of the jet water 23 from the jet nozzle 13 are stopped. At the time of complete cooling, contrary to the time of heating, compressive residual stress is generated on the inner surfaces of the nozzle welded portion 7 and the pipe welded portion 11 covered by the heating coil 25.

Thereafter, the deterioration preventive maintenance operation is carried out as in the embodiment of FIG.

According to this embodiment, the compressive residual stress can be generated more reliably on at least the inner surfaces of the nozzle welded portion 7 and the pipe welded portion 11, the residual stress can be improved, and the reliability of the welded portion can be further enhanced. .

The pressure of the jet water 23 jetted from the jet head 4 during the induction heating of the outer surface is 40 to 100M.
When the pressure is about Pa, the inner surface cooling and the peening action occur simultaneously, and cleaning and stress improvement can be achieved at the same time.

In each of the above-described embodiments, the deterioration of the sleeve-equipped nozzle provided in the pressure vessel of the nuclear power plant is preventively maintained after the start of operation of the power plant. It will be readily appreciated that the present invention may be applied prior to commissioning to more reliably generate compressive residual stresses on the inner surface, improve residual stresses and further enhance weld reliability.

[0057]

According to the present invention, the pre-injection pressure is increased from the plurality of injection nozzles of the annular injection head mounted so as to surround the pipe in the container toward the deepest part of at least one annular gap forming the blind alley. Since high pressure pure water jet of 40 MPa to 100 MPa is jetted to generate cavitation bubbles, the inner surface of the annular gap is decontaminated, and the surface layer metal of each weld is processed to change the residual stress into a compressive stress.
The high-pressure pure water jet not only reaches the inner part of the annular gap, but also causes turbulent flow inside the gap to generate turbulence-induced cavitation bubbles. When the cavitation bubbles are destroyed, extremely high pressure is generated, so that the decontamination of the annular gap and the improvement of the residual stress of the welded portion are simultaneously achieved.

First, high-pressure pure water jet is jetted from all of the plurality of jet nozzles of the annular jet head, and then,
Excessive cleaning can be prevented by repeating the injection of the high-pressure pure water jet while sequentially reducing the number of the injection nozzles for ejecting the high-pressure pure water jet. That is, when the number of spray nozzles for spraying the high-pressure pure water jet is successively reduced, the separated contaminants are collected together with the return water in each cleaning step, and there is no concern that they will become an abrasive and adversely affect.

Water in the nozzle with the thermal sleeve is made to flow by the pump attached to the container, high-frequency power is supplied to the heating coil installed on the outer periphery of the welded portion, and sufficient thermal strain is generated for the inner surface of the welded portion to yield and yield. Heating, stop heating immediately, stop the pump after the weld is completely cooled, and then perform each of the above steps, the inner surface causes tensile yielding in the thickness direction of the inner and outer surfaces. A sufficient temperature difference occurs. After cooling completely, high-pressure pure water jet is injected again into the gap and cavitation bubble treatment is performed, so that compressive residual stress can be generated more reliably on the inner surface of the welded portion, the residual stress is improved and the welded portion is improved. The reliability can be further enhanced.

Since the high-pressure pure water is pressurized after the polishing agent is mixed in the pure water, various decontamination effects can be obtained by selecting the polishing agent.

Since the return water is collected from the annular gap forming the blind alley, the return water is purified and re-supplied as high-pressure pure water, an increase in the amount of contaminants is suppressed.

[Brief description of drawings]

FIG. 1 is an overall view of an embodiment of a multi-metal pipe deterioration preventive maintenance device according to the present invention for preventive maintenance of deterioration of a sleeve nozzle provided in a pressure vessel of a nuclear power plant after the start of operation of the power plant. It is a system diagram which shows a structure.

FIG. 2 is a partial cross-sectional view showing, in an enlarged manner, a component arrangement and a fluid flow of a deterioration preventive maintenance device around a nozzle with a sleeve in the embodiment of FIG.

FIG. 3 is a cross-sectional view showing a transverse cross section perpendicular to the axis of the nozzle with sleeve which is the target of deterioration prevention in the embodiment of FIG.

FIG. 4 is a diagram showing an example of the arrangement of the injection nozzle and the suction pipe of the deterioration preventive maintenance device as seen from a direction perpendicular to the axis of the sleeve-equipped nozzle that is the object of deterioration prevention in the embodiment of FIG.

FIG. 5 is a partial cross-sectional view showing a component arrangement and a fluid flow of the deterioration preventive maintenance device around the sleeve nozzle in the embodiment of the deterioration preventive maintenance device for the multi-metal tube, that is, the nozzle with multiple sleeves according to the present invention.

FIG. 6 is a partial cross-sectional view showing the parts arrangement and fluid flow of the deterioration preventive maintenance device around the sleeve nozzle in the embodiment of the chamber type deterioration prevention maintenance device for the double metal pipe, that is, the sleeve nozzle according to the present invention.

[Explanation of symbols]

 1 Pressure Vessel 1a Flange 2 Service Platform 3 Injection Head 4 Suction Head 5 Remote Control Device 6 Nozzle 7 Nozzle Welding 8 Reactor Inner Tube 9 Sleeve Welding 10 Pipe 11 Pipe Welding 12 Annular Gap 13 Injection Nozzle 14 Suction Pipe 15 High Pressure Pump 16 high-pressure pure water 17 high-pressure hose 18 pure water tank 19 injection control device 20 suction hose 21 water treatment device 22 water treatment control device 23 jet water 24 return water 25 heating coil 26 cable 27 heating power supply 28 heating control device 29 reactor water 30 chamber 31 Safe End 31a Sleeve 32 High Pressure Pure Water Injection Device 33 General Control Device 34 Shroud

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI technical display location // C21D 7/04 Z 7217-4K (72) Inventor Masahiro Otaka 502 Kandachi-cho, Tsuchiura-shi, Ibaraki Prefecture Address In the Institute of Mechanical Research, Nitto Seisakusho Co., Ltd. (72) Masato Mochizuki, 502 Kintate-cho, Tsuchiura-shi, Ibaraki Prefecture In the Institute of Mechanical Research, Hitori Seisaku-sho, Ltd. (72) Shinji Sakata 502 Shintachi-cho, Tsuchiura, Ibaraki Prefecture Machinery Research Institute, Tate Works (72) Makoto Hayashi Makoto Hayashi, Tsuchiura-shi, Ibaraki Prefecture, 502 No. 1, Mechanical Research Laboratory, Hiritsu Works Co., Ltd. (72) Koichi Kurosawa, 1-1, Saiwai-cho, Hitachi City, Ibaraki Stock Company Hitachi, Ltd., Hitachi Plant (72) Inventor, Wataru Sagawa, 1-1, Saiwaicho, Hitachi City, Ibaraki Prefecture, Ltd. Hitachi, Ltd., Hitachi Plant, (72) Inventor, Yoshikubo Fujio 3-2, 3-chome, Saiwaicho, Hitachi City, Ibaraki Prefecture Hitachi Hitachi Engineering Co., Ltd.

Claims (11)

[Claims] 1. A weld between a nozzle formed on a side wall of a container and a safe end having at least one thermal sleeve, a weld between an innermost thermal sleeve of the safe end and a pipe in the container, and A multi-metal pipe including a welded portion of the safe end and an external pipe, and having at least one annular gap forming a blind path between the nozzle and the safe end and the pipe in the container and / or the thermal sleeve. In the deterioration preventive maintenance method, the pre-injection pressure is 40 from the plurality of injection nozzles of the annular injection head mounted so as to surround the tube in the container toward the deepest part of at least one annular gap that is the blind alley.
A high pressure pure water jet of MPa to 100 MPa is jetted to generate cavitation bubbles, the inner surface of the annular gap is decontaminated, and the surface layer metal of each of the welds is subjected to composition processing to change the residual stress into a compressive stress. Deterioration preventive maintenance method for multiple metal pipes. 2. The deterioration preventive maintenance method for a multi-metal pipe according to claim 1, wherein high-pressure pure water jets are first jetted from all of the plurality of jet nozzles of the annular jet head, and then high-pressure pure water jets are jetted. A method for preventing and preventing deterioration of a multi-metal pipe, characterized in that the injection of a high-pressure pure water jet is repeated while sequentially reducing the number of the injection nozzles. 3. The deterioration preventive maintenance method for a multi-metal pipe according to claim 1, wherein the water in the nozzle with the thermal sleeve is caused to flow by a pump attached to the container, and is installed on the outer periphery of the welded portion. High-frequency power is supplied to the heating coil, and the inner surface of the weld is heated until sufficient thermal strain occurs to yield tensilely, heating is immediately stopped, and the pump is stopped after the weld is completely cooled, After that, the deterioration preventive maintenance method of the multi-metal pipe, characterized in that the procedure according to claim 1 or 2 is executed respectively. 4. The deterioration preventive maintenance method for a multi-metal pipe according to claim 1, wherein an abrasive is mixed into the pure water and then the pressure is increased to the high-pressure pure water. Deterioration preventive maintenance method for multiple metal pipes. 5. The method for preventing and maintaining deterioration of a multi-metal pipe according to claim 1, wherein return water is collected from at least one annular gap forming the blind alley, and the collected return water is collected. A method for preventing and maintaining deterioration of a multi-metal tube, which comprises purifying water and re-supplying it as the high-pressure pure water. 6. A weld between a nozzle formed on the side wall of the container and a safe end having at least one thermal sleeve, a weld between the innermost thermal sleeve of the safe end and a pipe in the container, and A multi-metal pipe including a welded portion of the safe end and an external pipe, and having at least one annular gap forming a blind path between the nozzle and the safe end and the pipe in the container and / or the thermal sleeve. In the deterioration preventive maintenance device described above, a pure water tank for storing pure water, a means for pressurizing pure water supplied from the pure water tank, and a plurality of injection nozzles attached so as to surround the pipe in the container are provided. The pre-injection pressure supplied from the pressurizing means toward the deepest part of at least one annular gap forming the blind alley is 40 MPa to 100 M. An annular jet head for injecting a high-pressure pure water jet of Pa to generate cavitation bubbles, a means for sucking and collecting return water from at least one annular gap forming the blind alley, and purifying the recovered return water. A deterioration preventive maintenance device for a multi-metal pipe, comprising: means for returning to the pure water tank. 7. The deterioration preventive maintenance device for a multi-metal pipe according to claim 6, wherein high-pressure pure water jets are first jetted from all of the plurality of jet nozzles of the annular jet head, and then high-pressure pure water jets are jetted. An apparatus for preventing and preventing deterioration of a multi-metal pipe, comprising control means for controlling the jet head so as to repeat jetting of a high-pressure pure water jet while sequentially reducing the number of jet nozzles. 8. The deterioration preventive maintenance apparatus for a multi-metal pipe according to claim 6 or 7, wherein the multi-metal pipe is installed on the outer periphery of the welded portion and heated until the inner surface of the welded portion has sufficient thermal strain for tensile yielding. A heating coil, a heating power source that supplies high-frequency power to the heating coil, a pump that is attached to the container and causes water in the nozzle with the thermal sleeve to flow, and an inner surface of the welded portion sufficient for tensile yielding. Deterioration preventive maintenance of a multi-metal pipe characterized by additionally installing control means for stopping heating immediately after heating until heat distortion occurs and stopping the pump after the welded part has completely cooled apparatus. 9. The deterioration preventive maintenance apparatus for a multi-metal pipe according to claim 6, wherein the means for sucking and collecting the return water collects the pipe in the container together with the jet head. A deterioration preventive maintenance device for a multi-metal pipe, comprising a suction head having a plurality of suction pipes mounted so as to surround it. 10. The deterioration preventive maintenance device for a multi-metal pipe according to claim 6, wherein the means for sucking and collecting the return water is in contact with the inner wall of the container near the nozzle. A deterioration preventive maintenance device for a multi-metal pipe, comprising a chamber having a closed space on the nozzle side for suction. 11. The deterioration preventive maintenance device for a multi-metal tube according to claim 6, further comprising means for mixing an abrasive with pure water before pressurization supplied from the pure water tank. A multi-metal pipe deterioration preventive maintenance device characterized by being provided.