JP4892444B2 - Method for improving residual stress of structural members - Google Patents

Description

  The present invention relates to a method for improving the residual stress of a structural member, and more particularly to a method for improving the residual stress of a structural member suitable for application to an internal structure of a boiling water reactor.

  Water jet peening is known as a method for improving tensile residual stress generated in internal structures of a nuclear reactor such as a boiling water reactor and a pressurized water reactor into a compressive residual stress (Japanese Patent Laid-Open No. 6-47667). Gazette, JP-A-6-71564 and JP-A-2003-337192).

  The method for improving the residual stress of a structural member is, for example, by arranging a jet nozzle in cooling water in a reactor pressure vessel, directing the nozzle outlet toward an internal structure that performs water jet peening, and directing a high-speed jet flow to the internal structure. It spouts from a spout. A strong impact pressure is applied to a water jet peening construction target portion (hereinafter, simply referred to as a construction target portion) of the internal structure by cavitation caused by the collapse of bubbles (cavities) included in the jet flow. As a result, the tensile residual stress generated in the construction target part is improved to the compressive residual stress.

  In particular, Japanese Patent Laid-Open No. 6-47667 has a main jet outlet that ejects a high-speed jet stream at the center, and a plurality of peripheral jet nozzles that eject air (or air-saturated water) at a low speed around the main jet outlet. It is described that water jet peening is performed using a nozzle. These peripheral outlets are inclined so that the extension lines of the respective outlets intersect the extension lines of the main outlet. The nozzle described in Japanese Patent Application Laid-Open No. 6-47667 is used to induce cavitation by merging the air ejected from the surrounding ejection port with the high-speed jet stream ejected from the main ejection port. Thereby, an impact pressure is continuously applied to the construction target portion.

JP-A-6-47667 JP-A-6-71564 JP 2003-337192 A

  The impact pressure generated by cavitation is attenuated within a short distance from the nozzle when propagating through the surrounding cooling water. However, when there is another internal structure that does not perform water jet peening near the construction target part, the impact pressure may propagate to the other internal structure and vibration may occur in the other internal structure. The inventors have found that there is. In particular, when the frequency of the excitation force applied to the other internal structure other than the construction target portion due to the impact pressure matches the natural frequency of the other internal structure, resonance may occur.

  The objective of this invention is providing the residual-stress improvement method of the structural member which can suppress the vibration of the non-construction object part which does not construct water jet peening.

  A feature of the present invention that achieves the above-described object is a construction object that exists in water with an impact pressure that is generated when the first bubbles contained in a water jet ejected from a nozzle disposed in water disappear. By applying the first structural member to the first structural member, compressive residual stress is applied to the first structural member, and at least while the water jet is sprayed, the second structural member that is a non-construction target existing in water and the water jet. In addition, it is to form a bubble region where the second bubble different from the first bubble exists.

  Since a bubble region is formed between the jetted water jet and the second structural member, the impact pressure generated in the water jet is attenuated in the bubble region, so that the non-construction target part that does not perform water jet peening Propagation of impact pressure can be suppressed. For this reason, the vibration of the second structural member can be suppressed.

  ADVANTAGE OF THE INVENTION According to this invention, the vibration of the non-construction object part which does not construct water jet peening can be suppressed.

  Examples of the present invention will be described below.

  A method for improving the residual stress of a structural member, which is a preferred embodiment of the present invention, applied to a boiling water reactor (BWR) will be described below with reference to the drawings. First, a schematic structure of a BWR to which a method for improving a residual stress of a structural member is applied will be described with reference to FIGS. The BWR has a reactor pressure vessel (hereinafter referred to as RPV) 1 having a lid 11, and a steam dryer 2, a steam separator 3, a core shroud 5, a jet pump 7, an upper grid plate 15 and an RPV 1. A core support plate 16 and the like are arranged. The core shroud 5 is attached to the shroud support cylinder 4 via a shroud support ring 20. The shroud support cylinder 4 is installed at the bottom of the RPV 1 by a support leg 17. A shroud support baffle plate 6 is attached to the inner surface of the RPV 1 and the shroud support cylinder 4. A core support plate 16 is disposed in the core shroud 5 and installed in the core shroud 5. An upper lattice plate 15 disposed above the core support plate 16 is also installed in the core shroud 5. The steam separator 3 and the steam dryer 2 are installed above the upper grid plate 15. A plurality of jet pumps 7 are disposed in an annulus portion (downcomer) 8 formed between the RPV 1 and the core shroud 5, and are installed on the shroud support baffle plate 6.

  A plurality of fuel assemblies 12 are supported by the upper lattice plate 15 and the core support plate 16. A water supply sparger 10 is disposed in the RPV 1, and the water supply sparger 10 is connected to a water supply nozzle 14 provided in the RPV 1. A core spray pipe 9 is disposed between the core shroud 5 and the RPV 1.

  The method for improving the residual stress of the structural member of the present embodiment includes, for example, a welded portion 21 of the RPV 1 and the shroud support baffle plate 6, a welded portion 22 of the shroud support baffle plate 6 and the shroud support cylinder 4, and a shroud support cylinder. 4 and the shroud support ring 20, and the welded portion such as the welded portion 24 of the core shroud 5 and the shroud support ring 20. Each is applied to the ring 20.

  The method for improving the residual stress of the structural member of this embodiment is performed during the period of the BWR periodic inspection. In this periodic inspection, cooling water is filled into the reactor well 19 located above the RPV 1. Thereafter, the lid 11 of the RPV 1 is removed, and the steam dryer 2 and the steam / water separator 3 are taken out from the RPV 1. In the periodic inspection, the fuel assembly 12 is taken out of the RPV 1 as necessary, and the inspection from the inner and outer surfaces of the core shroud 5 and the water jet peening for the inner and outer surfaces are performed.

  The method for improving the residual stress of the structural member according to the present embodiment is implemented by, for example, inserting the preventive maintenance device 13 into the annulus portion 8 and positioning it near the welded portion (see FIG. 5). The preventive maintenance device 13 is lowered to the above position in the annulus portion 8 by remote control from a fuel changer or work carriage (not shown) traveling on the operation floor 18 through the access region 25 shown in FIG.

  A detailed configuration of the water jet peening apparatus 31 will be described with reference to FIG. The water jet peening apparatus 31 includes a preventive maintenance apparatus 13. The preventive maintenance device 13 includes a main nozzle 32 and an air nozzle 37. In addition to the preventive maintenance device 13, the water jet peening device 31 includes a high-pressure pump 33, a pump control device 34, an air supply machine (for example, an air compressor) 38, and an air supply machine control device 39. A high pressure hose 35 is connected to the main nozzle 32 and the high pressure pump 33. A control cable 36 connected to the pump control device 34 is connected to the high-pressure pump 33. The air nozzle 37 is connected to an air supply machine 38 by an air hose 40. A control cable 41 connected to the air supply control device 39 is connected to the air supply 38. The high pressure pump 33, the pump control device 34, the air supply device 38 and the air supply device control device 39 are installed on the operation floor 18. It is also possible to combine the pump control device 34 and the air supply device control device 39 into one control device. As described above, the preventive maintenance device 13 including the main nozzle 32 and the air nozzle 37 is disposed in the vicinity of the corresponding welded portion in the annulus portion 8 through the access region 25. In this state, the main nozzle 32 and the air nozzle 37 exist in the cooling water 46 in the RPV 1. The main nozzle 32 and the air nozzle 37 are moved together with the preventive maintenance device 13 in the vertical direction, the circumferential direction of the RPV1, and the radial direction of the RPV1. Thereby, the water jet peening along each of the welding parts 21, 22, 23, and 24 can be implemented.

  When the high-pressure pump 33 is driven, high-pressure water discharged from the high-pressure pump 33 is supplied to the main nozzle 32 through the high-pressure hose 35. The high-pressure water is jetted into the cooling water 46 from the jet nozzle (not shown) of the main nozzle 32 as a high-speed jet flow 42. The pump control device 34 controls the high-pressure pump 33 so that the high-speed jet stream 42 ejected from the main nozzle 32 has an optimum injection flow rate and injection pressure. The high-speed jet flow 42 is sequentially injected toward the shroud support cylinder 4, the core shroud 5, and the shroud support ring 20, which are construction target parts, centering on the welded parts 21, 22, 23, and 24. Air supplied from the air supply machine 38 is guided to the air nozzle 37 by the high-pressure hose 40. This air is injected into the cooling water 46 from an injection port (not shown) formed in the air nozzle 37 to form a bubble region (compressible fluid region) 45 in the cooling water 46. The air nozzle 37 is disposed between the main nozzle 32 and another structure (for example, the jet pump 7) other than the construction target part. From the air nozzle 37, nitrogen or argon may be injected instead of air. The bubble region 45 is formed in a range from the main nozzle 32 until the high-speed jet flow 42 reaches the work target portion, and is formed between the high-speed jet flow 42 and the jet pump 7.

  When a bubble (cavity) 43 contained in the high-speed jet flow 42 ejected from the main nozzle 32 collapses, an impact pressure (shock wave) 44 is generated. The impact pressure 44 is sequentially applied to the shroud support cylinder 4, the core shroud 5, and the shroud support ring 20 around the welds 21, 22, 23, and 24, respectively. For this reason, the tensile residual stress which has arisen in the shroud support cylinder 4, the core shroud 5, and the shroud support ring 20 is improved to the compressive residual stress. The tensile residual stress is generated in the shroud support cylinder 4, the core shroud 5, and the shroud support ring 20 by welding in the welded portions 23 and 24.

  The impact pressure 44 propagates through the cooling water 46 toward another structure that is not the construction target part, for example, the jet pump 7 that is the non-construction target part. However, in the present embodiment, the bubble region 45 is formed between the high-speed jet flow 42 and the jet pump 7 over the range from the main nozzle 32 until the high-speed jet flow 42 reaches the construction target part. Due to the bubble region 45, the impact pressure 44 propagated to the jet pump 7 is attenuated. For this reason, the vibration of the jet pump 7 caused by the impact pressure 44 is reduced. The stress generated in the jet pump 7 at this time is shown in FIG. 2 in comparison with the conventional method for improving the residual stress of the structural member. In this embodiment, the stress generated in the jet pump 7 is reduced more than that in the conventional example.

  The air supply control device 39 controls the air supply 38 so that the pressure of the air discharged from the air supply 38 becomes a set pressure determined based on the diameter and shape of the injection port of the air nozzle 37. As described above, the diameter of the bubbles in the bubble region 45 that are injected from the air nozzle 37 into the cooling water 46 is controlled. This control of the diameter of the bubbles changes the profile of the excitation frequency applied to the jet pump 7 due to the impact pressure 44 generated when the bubbles 43 included in the high-speed jet stream 42 ejected from the main nozzle 32 are crushed. be able to. For this reason, it can be avoided that the natural frequency of the jet pump 7 and the profile of the excitation frequency due to the impact pressure 44 match, and resonance of the jet pump 7 can be prevented.

  FIG. 3 shows frequency characteristics of vibrations generated in the jet pump 7 in the present embodiment and the conventional example. Specifically, FIG. 3A shows frequency characteristics of vibration generated in the jet pump 7 in the conventional example, and FIG. 3B shows frequency characteristics of vibration generated in the jet pump 7 in the present embodiment. . In the present embodiment, the frequency characteristics of vibration generated in the jet pump 7 due to the impact pressure 44 can be changed from FIG. 3A to FIG. 3B by injecting bubbles from the air nozzle 37. it can. For this reason, the frequency of the peak of the Fourier spectrum can be changed, and resonance of the jet pump 7 can be prevented.

  In addition, since the speed of sound in the bubble region 45 is changed by changing the type and temperature of the gas injected from the air nozzle 37, the profile of the excitation frequency caused by the impact pressure 44 can be controlled, and similar effects are obtained. Is obtained.

  In this embodiment, the impact pressure 44 generated when the bubbles 43 contained in the high-speed jet stream 42 injected from the main nozzle 32 are crushed is applied to the shroud support cylinder 4, the core shroud 5, and the shroud support ring 20 that are the construction target parts. Thus, the tensile residual stress generated in the construction target portion can be improved to the compressive residual stress. For this reason, generation | occurrence | production of the stress corrosion crack in a construction object part can be suppressed. In the present embodiment, the bubble region 45 containing bubbles ejected from the air nozzle 37 is formed between the high-speed jet flow 42 and the jet pump 7 that is a non-working target portion. It is attenuated and the impact pressure 44 is reflected at the bubble interface in the bubble region 45. For this reason, the vibration of the jet pump 7 that receives the impact pressure 44 is greatly reduced. Since the above-described effect can be obtained by ejecting a small amount of air from the air nozzle 37, a small air supply unit 38 can be used.

  In order to effectively generate a compressive residual stress in the construction target portion and effectively reduce vibration of the jet pump 7, the axis of the air injection port formed in the air nozzle 37 is formed in the main nozzle 32. Or substantially parallel to the axis of the injection port for injecting the high-speed jet flow 42, or arranged so that the axis of the former injection port faces outward with respect to the axis of the latter injection port. desirable.

  The impact pressure 44 generated in the high-speed jet flow 42 is generated at the moment when the bubbles (cavities) 43 contained in the high-speed jet flow 42 contract and disappear (the volume is zero). The nozzle described in FIG. 2 of Japanese Patent Application Laid-Open No. 6-47667 merges the air jetted from the surrounding jets with the high-speed jet flow jetted from the main jets, and generates impact pressure in the high-speed jets. This is to increase the number of bubbles that form the nucleus. Thereby, the strength of the impact pressure is increased.

  The inventors conducted a test under actual machine conditions in which air was ejected from the air nozzle 37 with the axis of the ejection port of the air nozzle 37 directed toward the axis of the ejection port of the main nozzle 32. As a result, it was confirmed that when the bubbles ejected from the air nozzle 37 were caught in the high-speed jet flow 42, the strength of the generated impact pressure was reduced. It is necessary to set the angle of the axis of the injection port of the air nozzle 37 with respect to the axis of the injection port of the main nozzle 32 so that the bubbles injected from the air nozzle 37 are not involved in the high-speed jet flow. Therefore, the axis of the injection port formed in the air nozzle 37 is substantially parallel to the axis of the injection port formed in the main nozzle 32, or the axis of the former injection port is set to the axis of the latter injection port. It is good to arrange | position so that it may face outside with respect to an axial center.

  In this embodiment, since the diameter of the bubbles ejected from the air nozzle 37 can be controlled by the air supply controller 39, the vibration applied to the jet pump (non-work target part) 7 due to the impact pressure 44. The frequency profile can be changed. For this reason, it can be avoided that the natural frequency of the jet pump 7 and the profile of the excitation frequency due to the impact pressure 44 match, and resonance of the jet pump 7 can be prevented.

  A method for improving the residual stress of the structural member of Example 2 which is another example of the present invention applied to BWR will be described below with reference to FIGS. In this embodiment, vibrations of the shroud support baffle plate 6 and the jet pump 7 that are non-working objects that receive the impact pressure 44 are suppressed when water jet peening is performed.

  A configuration of a water jet peening apparatus 31A used in the method for improving a residual stress of a structural member of the present embodiment will be described with reference to FIGS. The water jet peening apparatus 31A has a configuration in which the air nozzle 37 is replaced with air nozzles 37A and 37B in the water jet peening apparatus 31. The air nozzles 37 </ b> A and 37 </ b> B are connected to the air supply unit 38 by a branched air hose 40. The preventive maintenance device 13 of the water jet peening device 31A includes a main nozzle 32 and air nozzles 37A and 37B. Other configurations of the water jet peening apparatus 31A are the same as those of the water jet peening apparatus 31.

  A method for improving the residual stress of the structural member of this embodiment will be described. Similarly to the first embodiment, the preventive maintenance device 13 is moved into the annulus portion 8 through the access region 25, and is arranged so that the main nozzle 32 faces the construction target portion. In this state, the air nozzle 37 </ b> A is disposed between the main nozzle 32 and the jet pump 7, and the air nozzle 37 </ b> B is disposed between the main nozzle 32 and the shroud support baffle plate 6. The high-pressure pump 33 is driven to eject the high-speed jet stream 42 from the main nozzle 323 and the impact pressure 44 generated when the bubbles 43 are crushed is applied to the shroud support cylinder 4, the core shroud 5, and the shroud support ring 20 that are the construction target parts. Each added. The tensile compressive stress generated in these members is improved to the residual compressive stress.

  In the bubble region 45A formed by the air jetted from the air nozzle 37A, the high-speed jet flow 42 reaches the construction target portion from the main nozzle 32 between the high-speed jet flow 42 and the jet pump 7 which is the non-work target portion. It is formed in the range. The bubble region 45B formed by the air jetted from the air nozzle 37B is located between the high-speed jet flow 42 and the shroud support baffle plate 6 which is a non-working target portion, and the high-speed jet flow 42 from the main nozzle 32 to the construction target portion. It is formed in the range until it reaches. Since the impact pressure 44 propagated toward the jet pump 7 is attenuated by the bubble region 45A, the vibration of the jet pump 7 generated by the impact pressure 44 is greatly reduced. Furthermore, since the impact pressure 44 propagated toward the shroud support baffle plate 6 is attenuated by the bubble region 45B, the vibration of the shroud support baffle plate 6 generated by the impact pressure 44 is greatly reduced.

  Also in this embodiment, since the diameter of the bubbles ejected from the air nozzle 37A is controlled by the air supply controller 39, the resonance of the jet pump 7 can be prevented as in the first embodiment. Further, in the present embodiment, the diameter of bubbles injected from the air nozzle 37 </ b> B is controlled by the air supply controller 39, so that the additional force applied to the shroud support baffle plate (non-work target part) 6 due to the impact pressure 44. The oscillation frequency profile can be changed. For this reason, it can avoid that the natural frequency of the shroud support baffle plate 6 and the profile of the excitation frequency by the impact pressure 44 match, and the resonance of the shroud support baffle plate 6 can be prevented. The control of the bubble diameter ejected from the air nozzle 37B by the air supply controller 39 is the same as in the first embodiment.

  A method for improving the residual stress of the structural member of Example 3, which is another example of the present invention, applied to BWR will be described below with reference to FIGS. 11 and 12. A water jet peening apparatus 31B used in the method for improving the residual stress of the structural member of this embodiment is also shown in FIGS. The water jet peening apparatus 31B has a configuration in which the air nozzles 37A and 37B are replaced with annular air nozzles 37C in the water jet peening apparatus 31A. Other configurations of the water jet peening apparatus 31B are the same as those of the water jet peening apparatus 31A. The air nozzle 37C communicated with the air supply unit 38 surrounds the main nozzle 32 and has a large number of injection ports in the circumferential direction so as to form an annular bubble region 45C. Air (bubbles) is respectively ejected from these ejection ports. The bubble region 45C surrounds the high-speed jet flow 42. That is, the bubble region 45 </ b> C exists between the high speed jet flow 42 and the jet pump 7 and between the high speed jet flow 42 and the shroud support baffle plate 6.

  Therefore, as in the second embodiment, vibrations in each of the jet pump 7 and the shroud support baffle plate 6 are greatly reduced, and resonance in each of the jet pump 7 and the shroud support baffle plate 6 can be prevented. In the present embodiment, since the annular bubble region 45C is formed, vibration in each of the jet pump 7 and the shroud support baffle plate 6 can be reduced as compared with the second embodiment.

  A method for improving the residual stress of a structural member of Example 4 which is another example of the present invention applied to BWR will be described below with reference to FIG. A water jet peening apparatus 31C used in the structural member residual stress improvement method of this embodiment will be described with reference to FIG. The water jet peening apparatus 31C has a configuration in which an isolation wall (bubble mixing prevention member) 46 is provided in the water jet peening apparatus 31 used in the first embodiment. The isolation wall 46 is attached to the preventive maintenance device 13 including the main nozzle 32 and the air nozzle 37. In the water jet peening apparatus 31 </ b> C, two separation walls 46 are provided in parallel, and an air nozzle 37 is disposed between the two separation walls 46. These isolation walls 46 are disposed between the main nozzle 32 and the high-speed jet flow 42 and the shroud support baffle plate 6 which is a non-work object. The isolation wall 46 is arranged over a range from the main nozzle 32 until the high-speed jet flow 42 reaches the construction target part (the shroud support cylinder 4, the core shroud 5, and the shroud support ring 20).

  Two separation walls 46 may be disposed between the high-speed jet flow 42 and the jet pump 7, and the air nozzle 37 </ b> A illustrated in FIG. 10 may be disposed between the separation walls 46.

  When the bubbles 43 contained in the high-speed jet stream 42 ejected from the main nozzle 32 are crushed, an impact pressure 44 is generated, and the impact pressure 44 imparts a compressive residual stress to the work object. The impact pressure 44 propagating through the cooling water 46 is a wave (density wave) having a frequency characteristic close to white noise. In the present embodiment, the isolation wall 46 is disposed. However, the isolation wall 46 itself is vibrated by the impact pressure 44, and the impact pressure 44 is diffracted toward the rear side (non-work target side) of the isolation wall 46. It is difficult to attenuate the impact pressure 44 at the isolation wall 46 because it propagates and the impact pressure 44 having the same frequency component as the natural frequency of the isolation wall 46 passes through the isolation wall 46. For this reason, in this embodiment, the bubble region 45 is formed between the high-speed jet flow 42 and the non-work object (the shroud support baffle plate 6 and the jet pump 7).

  In this embodiment, since the bubble region 45 is formed, vibration in the shroud support baffle plate 6 (and the jet pump 7) is reduced, and resonance in the shroud support baffle plate 6 (and jet pump 7) can be prevented. . In the present embodiment, as in the first embodiment, the diameter of the bubbles ejected from the air nozzle 37 is controlled.

  In this embodiment, since the isolation wall 46 is provided, it is possible to prevent the bubbles ejected from the air nozzle 37 from being caught in the high-speed jet flow 42. For this reason, since the intensity | strength of the generated impact pressure 44 does not fall, it can prevent that the effect of the water jet peening with respect to a construction target object reduces.

  In this embodiment, since the air nozzle 37 is disposed between the two separation walls 46, the flow of bubbles in the bubble region 45 can be controlled, and the main nozzle 32 can be compared with the case where the single separation wall 46 is used. The bubble region 45 can be held without being diffused to a position far from the center. For this reason, the present embodiment can enhance the damping effect of the impact pressure 44 by the bubble region 45 as compared with the case where the single isolation wall 46 is used. The isolation wall 46 may be a single sheet. When the number of the isolation walls 46 is one, the single isolation wall is disposed between the bubble region 45 and the high-speed jet flow 42.

  A method for improving the residual stress of a structural member of Example 5 which is another example of the present invention applied to BWR will be described below with reference to FIG. A water jet peening apparatus 31D used in the method for improving the residual stress of the structural member of this embodiment will be described with reference to FIG. The water jet peening apparatus 31D includes a main nozzle 32 and an air nozzle 37, and also includes an isolation wall (isolation wall 46A) as in the fourth embodiment.

  In the method for improving the residual stress of the structural member of the present embodiment, the angle θ formed by the shaft center of the main nozzle 32 and the work object (the shroud support cylinder 4, the core shroud 5, and the shroud support ring 20) is an acute angle in the longitudinal section of the RPV 1. It is an example which implements water jet peening in a state. In the present embodiment, the main nozzle 32 is disposed in the annulus portion 8 with the axis thereof inclined at an angle θ, so the distance from the main nozzle 32 to the jet pump 7 that is a non-work target is the third embodiment. Longer than that distance. However, in the vicinity of the construction object, the jet pump 7 is located near the high-speed jet stream 42 ejected from the main nozzle 32. For this reason, the impact pressure 44 generated in the high-speed jet flow 42 is easily propagated to the jet pump 7.

  In the present embodiment, the isolation wall 46A is inclined and attached to the preventive maintenance device 13 of the water jet peening device 31D in the same manner as the main nozzle 32. The isolation wall 46 </ b> A is disposed between the jet pump 7 and the high speed jet stream 32 on the downstream side of the high speed jet stream 32. A bubble region 45 formed by bubbles ejected from the air nozzle 37 is formed between the isolation wall 46 </ b> A and the jet pump 7. The bubbles flow along the isolation wall 46A.

  In the present embodiment, similar to the fourth embodiment, it is possible to obtain effects such as application of compressive residual stress to the work object, significant vibration reduction of the jet pump 7, and prevention of resonance of the jet pump 7. Since the isolation wall 46A is used, it is possible to suppress the bubbles in the bubble region 45 from being entrained in the high-speed jet flow 42, and to prevent the impact pressure 44 from being lowered. For this reason, the application of the compressive residual stress to the construction target portion can be effectively performed.

  An isolation wall may be disposed between the high-speed jet flow 42 and the shroud support baffle plate 6, and the bubble region 45 may be formed between the isolation wall and the shroud support baffle plate 6.

  Instead of the bubble region 45, an elastic body (for example, a resin member that includes air) in which a gas (for example, air) is included can be used. This elastic body is disposed at the position where the isolation wall 46 is disposed in the fourth and fifth embodiments. By using this elastic body, the air nozzle 32, the air supply device 38, the air hose 40, the air supply device control device 39 and the isolation wall 46 are not required, and the water jet peening device can be made more compact. In Examples 1 to 3, the elastic body can be used instead of the bubble region.

  The method for improving the residual stress of the structural member described above can also be applied to the structural member in the reactor vessel of the pressurized water reactor.

It is a block diagram of the water jet peening apparatus used for the residual stress improvement method of the structural member of Example 1, which is a preferred embodiment of the present invention. It is a characteristic view which shows the relationship between the distance from the center of a high speed jet flow, and the stress which generate | occur | produces in a jet pump. The frequency characteristic of the vibration which generate | occur | produces in a jet pump is shown, (A) is explanatory drawing which shows the frequency characteristic in a prior art example, (B) It is explanatory drawing which shows the frequency characteristic in Example 1. FIG. It is a longitudinal cross-sectional view of BWR to which the residual stress improvement method for a structural member shown in FIG. 1 is applied. It is an enlarged view of the V section of FIG. It is VI-VI sectional drawing of FIG. It is VII-VII sectional drawing of FIG. It is a block diagram of the water jet peening apparatus used for the residual stress improvement method of the structural member of Example 2 which is another Example of this invention. It is IX-IX sectional drawing of FIG. It is XX sectional drawing of FIG. It is a block diagram of the water jet peening apparatus used for the residual stress improvement method of the structural member of Example 3 which is another Example of this invention. It is XII-XII sectional drawing of FIG. It is a block diagram of the water jet peening apparatus used for the residual stress improvement method of the structural member of Example 4 which is another Example of this invention. It is a block diagram of the water jet peening apparatus used for the residual stress improvement method of the structural member of Example 5 which is another Example of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Reactor pressure vessel, 4 ... Shroud support cylinder, 5 ... Core shroud, 6 ... Shroud support baffle plate, 7 ... Jet pump, 8 ... Annulus part, 13 ... Preventive maintenance device, 20 ... Shroud support ring, 21,22 , 23, 24 ... welds, 31, 31A, 31B, 31C, 31D ... water jet peening device, 32 ... main nozzle, 33 ... high pressure pump, 34 ... pump control device, 37, 37A, 37B ... air nozzle, 38 ... air Supply machine 39 ... Air supply machine control device 42 ... High speed jet flow 44 ... Impact pressure 45,45A, 45B ... Bubble area 46,46A ... Isolation wall.

Claims (9)

A water jet is ejected from a first nozzle arranged in the water,
The impact pressure generated when the first bubbles contained in the water jet disappear is applied to the first structural member, which is a construction object existing in the water, so that the compressive residual stress is applied to the first structural member. And grant
At least during the jet of the water jet, a second bubble different from the first bubble exists between the second structural member, which is a non-construction object existing in the water, and the water jet. A method for improving residual stress of a structural member, characterized by forming a bubble region.   The method for improving residual stress of a structural member according to claim 1, wherein the bubble region is formed by injecting a gas from a second nozzle disposed in the water.   The axis of the second injection port for injecting the gas formed in the second nozzle is substantially parallel to the axis of the first injection port for injecting the water jet formed in the first nozzle. The method for improving a residual stress of a structural member according to claim 2, wherein the method is arranged toward or outward.   The method for improving residual stress of a structural member according to any one of claims 1 to 3, wherein a bubble mixing prevention member is disposed between the water jet and the bubble region.   The method for improving residual stress of a structural member according to any one of claims 1 to 4, wherein the bubble region is formed in an annular shape so as to surround the water jet. A water jet is ejected from a first nozzle arranged in the water,
By applying the impact pressure generated when the bubbles contained in the water jet disappear to the first structural member, which is a construction target existing in the water, compressive residual stress is applied to the first structural member. And
At least while the water jet is being jetted, an impact pressure buffering member containing gas is disposed between the water jet and the second structural member that is a non-construction object existing in the water. A method for improving residual stress of a structural member. Immerse the first nozzle in the water in the reactor vessel,
A water jet is injected into the water from the first nozzle;
The impact pressure generated when the first bubbles contained in the water jet disappear is applied to the first structural member, which is a construction object existing in the water, in the reactor vessel. Apply compressive residual stress to structural members,
At least during the injection of the water jet, the second air bubble is different from the first bubble between the second structural member, which is a non-construction object existing in the water in the reactor vessel, and the water jet. A method for improving a residual stress of a structural member of a nuclear power plant, wherein a bubble region in which second bubbles are present is formed.   The said bubble area is a residual stress improvement method of the structural member of the nuclear power plant of Claim 7 formed by injecting gas from the 2nd nozzle immersed in the said water.   The method for improving residual stress of a structural member of a nuclear power plant according to claim 7 or 8, wherein the second structural member is a jet pump installed in the reactor vessel.

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