JPH10142376A - Replacement method of reactor core shroud - Google Patents

Abstract

PROBLEM TO BE SOLVED: To conduct the inspection technique, a prevention safety technique, and a repairing technique of a structure in the rector of a nuclear power plant inexpensively by performing machining for applying a compression stress to the welded part of any or all of the equipments such as a jet pump riser pipe in a process for replacing a shroud. SOLUTION: When a reactor core shroud is exchanged, shot peening machining is performed to the welded part of an old shroud and a new shroud 2 on a work bench 7 installed at the bottom of the reactor while water at a reactor bottom part is drained and a means for shielding radiation is provided and water is injected into an annulus part. A shot supply tank 8 and a high-voltage air source are installed outside a pressure vessel 1, a carrying hose is passed through a CRD housing 5 or an ICM housing, and a shot that is accelerated by a high-voltage air is carried to a shot-peening nozzle, that is retained by a worker 11a. A suction hole for collecting a projection shot is installed around a nozzle in the head for shot peening, and the sucked shot returns to a supply device via a same path as the supply line and is used again.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for replacing a core shroud of a reactor internal structure, and more particularly to a method for inspecting, preventing, and / or repairing in-core equipment when replacing a core shroud.

[0002]

2. Description of the Related Art With the long-term operation of a nuclear power plant, various preventive maintenance techniques, replacement techniques and repair techniques for each equipment have been developed for the purpose of improving the reliability and extending the life of furnace equipment. For example, it is planned to install automatic equipment in the furnace at the time of periodic inspection of the plant, access the equipment in the furnace, and implement various countermeasure methods. Above all, various techniques have been developed for countermeasures against stress corrosion cracking due to residual tensile stress remaining in the weld. Shot peening is effective as a countermeasure against stress corrosion cracking because it can form a compressive stress on the surface by projecting a shot of metal or ceramic onto the surface of the member. Polishing of the surface with a special tool, water jet pinning, hammer pinning, pulsed laser irradiation, and the like have been proposed as similar techniques.

[0003]

However, since all of these technologies need to be installed remotely underwater, it is necessary to develop a dedicated automatic device tailored to the target site. Similarly, inspection and repair techniques also require dedicated automatic equipment corresponding to each technique and target equipment, and thus require a long preparation period and development costs before construction.
Furthermore, when each technology is applied using a remote automatic device, there is a limit on the automatic device side such as positioning accuracy, so a problem arises from the point of reliability of the construction especially when applied to a narrow part. there is a possibility. Further, if the above-described countermeasure technology is implemented at the time of the periodic inspection, the regular inspection period is lengthened, the plant operation rate is reduced, and a problem arises in terms of economy.

[0004] The present invention is to solve or reduce these problems and to provide a method for reliably and at low cost the inspection technology, preventive maintenance technology, and repair technology for the internal structure of an existing nuclear power plant. is there.

[0005]

A method of replacing a core shroud according to the present invention is to remove a reactor pressure vessel upper lid, a shroud upper part and internal structures of a shroud, chemically decontaminate the inside of the furnace with a chemical, and provide a shroud support. After cutting the cylinder part, drain the reactor water, and in the core shroud replacement method of welding a new shroud, in the shroud replacement step, the jet pump riser pipe, the jet pump diffuser, the jet pump riser brace arm, the water level instrumentation nozzle, Recirculation nozzle, water supply nozzle, CRD stub tube, in-core monitor housing, shroud support, support leg, shroud head, steam dryer, core spray piping, baffle plate, upper grid plate, core support plate, etc. Compressed on all equipment welds And performing processing to impart a force.

In the method for exchanging a core shroud of the present invention, the reactor pressure vessel upper lid, the upper part of the shroud and the internal structure of the shroud are removed, and the inside of the furnace is chemically decontaminated using a chemical, and the shroud support cylinder is cut. In the replacement method of the core shroud for draining the reactor water and welding the new shroud, a process of applying compressive stress to the shroud support and the new shroud weld may be performed.
Alternatively, a process of applying a compressive stress to the new shroud weld may be performed in advance.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The core shroud is located closest to the core, so that it is exposed not only to high-temperature and high-pressure water but also to material deterioration due to neutron irradiation, and from the viewpoint of improving the reliability and extending the life of the plant, the core shroud is used. Replacement is desirable. In the replacement work, after decontaminating the inside of the furnace with chemicals,
In an aerial environment, an old shroud is cut off and a new shroud is welded, so that an environment in which a worker can work in a furnace is used for a short time. In addition, steam dryer, core spray line, shroud head,
Since the equipment such as the upper lattice plate is removed in advance and stored in the equipment storage pool, inspection, welding, repair, and replacement of welds can be performed in the storage pool.

In the manufacturing process, it is effective to perform a process of applying a compressive stress to the new shroud weld and convert the tensile residual stress generated in the weld into a compressive stress in advance. Shot peening, polishing, and hammer pinning are reliable and inexpensive construction methods. When shot peening is performed in the air, there are a type of conveying with high-pressure air and a type of using centrifugal force, and any method may be used. In addition, polishing is alumina,
By using a polishing tool made of resin or chemical fiber impregnated with a ceramic abrasive such as tungsten carbide, a compressive stress can be reliably formed on the surface. Hammer pinning is a technique in which a plurality of needles are reciprocated using high-pressure air or an ultrasonic vibrator as a power source, thereby plastically processing the material surface and forming a compressive stress on the surface.

Regarding the structure of the furnace bottom such as CRD stub tube weld, ICM housing weld, shroud support, support leg, etc.
Inspection, ultrasonic inspection, RT inspection, etc. are possible,
Further, as a stress improvement work, an operator can perform shot peening, hammer peening and polishing, or an automatic machine can be installed at the bottom of the furnace to perform the work. Repair and replacement work can be performed in a short time and reliably by using an operator or an automatic machine. In particular, since the internal structure of the automatic machine has been removed, dimensional restrictions, loading and installation conditions have been eased, and there is a design margin, so that a simple and inexpensive automatic machine can fully function. .

Further, when the furnace bottom work is performed, the space between the shroud and the pressure vessel is filled with water in order to keep the dose inside the furnace low, so that a water level instrumentation nozzle, a recirculation nozzle, a baffle plate The upper access hole cover, the baffle plate and the shroud, and the weld between the baffle plate and the pressure vessel are in an underwater environment, and in addition to shot pinning, pulsed laser irradiation and water jet pinning can be applied for stress improvement. is there. When shot peening is performed in water, a water transfer type is advantageous. Water jet pinning is a technique for forming a compressive stress on a surface by plastically deforming a material by the collapse pressure of cavitation generated when high-pressure water is injected into water. When a pulsed laser is irradiated, atoms on the surface are instantaneously turned into plasma, and a compressive stress can be formed in the material by the reaction force. Both technologies require that a head be installed on a remote automatic device to perform automatic construction.However, there are no obstacles such as sensing lines, and a large space above the jet pump is secured. The workability of installation and relocation has been improved. For the same reason, the inspection, repair, and replacement work of the above-mentioned parts can be performed in a shorter time and at lower cost than before by performing the work accompanying the replacement work of the core shroud.

After the jet pump inlet mixer is removed, a shielding lid is installed at the upper part of the riser pipe and the upper part of the diffuser so that water does not leak outside the furnace and to the bottom of the furnace. Access from the furnace bottom and outside the pressure vessel becomes possible. Therefore, inspection, compression stress applying processing, and repair of the welded portion can be performed in an aerial environment. As a processing method, in addition to shot pinning, polishing and hammer pinning are suitable. By installing an automatic device inside a riser pipe or a diffuser, the amount of exposure of an operator can be reduced.

As described above, according to the present invention, inspection of various internal structures, stress improvement work, and repair work can be carried out in conjunction with the core shroud replacement work carried out in the air. The reliability of the furnace internals can be further improved as compared with the shroud replacement method.

[0013]

Next, an embodiment of the present invention will be described with reference to the drawings.

(Embodiment 1) FIG. 1 shows a state in which water at the bottom of the furnace is drained at the time of replacement of the core shroud, and water is injected into the annulus part in order to shield radiation. 3 shows a conceptual diagram in the case where shot peening is performed on the welded portions of the old shroud and the new shroud 2. The shot supply tank 8 and the high-pressure air source are set outside the pressure vessel 1, and the shot accelerated by the high-pressure air is transferred to the shot pinning nozzle held by the worker 11a through the transfer hose through the CRD housing 5 or the ICM housing. I do. The shot pinning head is provided with suction holes for collecting projected shots around the nozzles, and the sucked shots are returned to the supply device along the same path as the supply line and reused. In addition, shots remaining partially in the furnace are collected by suction, and the CRD differs from the supply line.
It is transferred out of the pressure vessel via the housing or ICM housing and reused. In the figure, reference numeral 3 denotes a baffle plate, 4 denotes a shroud support leg, 6 denotes a jet pump diffuser, 11 denotes a shroud support cylinder, and 9 and 10 denote shot recovery bathskets.

Similar systems include a CRD housing / stub tube weld at the furnace bottom, a stub tube / lower mirror weld, an ICM housing / lower mirror weld, a shroud support leg / lower mirror weld, a baffle plate furnace bottom weld. It can also be applied to the shot pinning process.

A simulated test body simulating the lower mirror / stub tube / CRD housing was prepared, and shot peening was performed. The housing was made of SUS304, the stub tube was made of Inconel 600, the lower mirror overlay welding, the lower mirror / stub tube, and the welding between the stub tube and the housing were made of Inconel 182. The stub tube welding heat affected zone was shot at 0.3 mm in shot diameter and 5 shot pressure using a high pressure air transfer type device.
An operator performed shot peening under the condition of kgf / cm ² . The arc height value at that time was 0.33A.
FIG. 2 shows the surface residual stress distribution before and after the construction measured by the X-ray stress measurement method. From this figure, the construction range is 550-550
It can be seen that a high compressive stress of 650 MPa was formed.

(Embodiment 2) FIG. 3 shows a state in which water at the bottom of the furnace is drained when the core shroud is replaced, and the CRD stub tube 27 and the outer surface of the housing 26 are poured into the annulus as a radiation shielding measure. The example of a structure of the apparatus which performs a shot pinning process is shown. The shot peening nozzle 18 is driven by driving the CRD housing motor 13.
The swivel mechanism 12 that swivels along the outer surfaces of the housing 26 and the stub tube 27 is fixed to the upper portion of the housing via the base portion 14. A straight pipe part 25 is attached to the elevating shaft 15 fixed to the turning mechanism 12 by a rack and pinion mechanism 20 so as to be able to move up and down. A shot pinning nozzle 18 is attached to the lower end of the straight pipe section 25 via a tilt shaft 17, and the nozzle 18 and the straight pipe section 25 are connected by a flexible tube 19. The projection tube 22 is attached to the upper end of the straight pipe section 25. The shot pinning nozzle 18 attached to the tip of the straight pipe portion 25 extending downward from the turning mechanism 12 is positioned to the construction target portion by the rack and pinion mechanism 20, and is driven in the axial direction. The whole device is supported by wheels 23 installed inward from the ring 24 and is configured to be able to move along the outer surface of the housing. Here, 16 indicates a motor, and 21 indicates a cable. With this apparatus, it is possible to perform compressive stress applying processing on the welded portion between the reactor pressure vessel lower mirror and the stub tube and the welded portion between the housing and the stub tube. Further, by attaching an inspection tool such as VT and UT, a repair tool such as a welding torch, and a cutting tool such as an EDM electrode in place of the shot peening head, inspection, repair, and replacement work of a welded portion can be easily performed.

(Embodiment 3) FIG. 4 shows an example of the construction of a construction apparatus for performing shot peening on the outer surface of the welded portion between the shroud support cylinder 11 and the new shroud 2. At the time of manufacturing a new shroud, a guide rail 28 for running a shot peening head is installed on the outer surface, and a running vehicle 31 is run along the guide rail to perform shot peening on a welded portion. By moving the pinning head 32 up and down by the rack and pinion mechanism 29, accurate positioning is possible. Further, by attaching an inspection tool such as VT or UT instead of the shot pinning head, it is possible to inspect the welded portion. In FIG. 4, reference numeral 30 denotes a motor, 33 denotes a cable, and 34 denotes a projection tube.

SUS304 shroud support and S
Simulated specimen (1) simulating US316L new shroud weld
000 x 1000 x 38 tmm), and the residual stress distribution on the surface was measured in the as-welded state. A tensile stress field was present in a region 20 mm from the weld metal / base metal boundary, and the maximum stress value was 400 MPa. showed that. Shot diameter 0.3mm, projection pressure 5 using high pressure air transfer type device to weld
An operator performed shot peening under the condition of kgf / cm ² . The arc height value at that time was 0.35A.
FIG. 5 shows the surface residual stress distribution before and after the construction measured by the X-ray stress measurement method. From this figure, the construction range is 400 ~
It can be seen that a high compressive stress of 650 MPa was formed.

(Embodiment 4) FIG. 6 shows the baffle plate 3
2 shows a configuration example of a shot-peening application apparatus for a welded portion of a shroud support cylinder 11. After the existing shroud is cut and removed, the shot pinning device is caused to travel along the welded portion between the baffle plate 3 and the shroud support cylinder 11 by making the cut portion 43 function as a rail, thereby performing shot pinning. . This device comprises a traveling vehicle 35, turning axes 36, 37,
And an elevating shaft 39 for moving the head up and down.
Positioning is possible at any position. In the figure, 40 indicates a cable, and 41 indicates a projection tube.

The traveling vehicle 35 is fixed on the rails 43, and the baffle plate 3 and the jet pump diffuser 6 are welded to each other by the above-mentioned mechanism so that shot pinning can be performed. In addition, by installing an inspection tool such as VT and UT, a repair tool such as a welding torch, and a cutting tool such as an EDM electrode in place of the shot pinning head, inspection, repair, and replacement of a welded portion can be easily performed.

(Embodiment 5) FIG. 7 shows an inspection of the inside of the CRD housing 26 after the old core shroud is removed.
This shows a configuration of an in-furnace working device for performing repair and surface modification, and a case where a work tool is a shot peening nozzle 55 will be described. In the figure, the old core shroud (not shown in FIG. 7) has been cut and removed, and the inside of the reactor pressure vessel has been chemically decontaminated. On the CRD housing 26, a scaffold on which an operator can work is assembled. The in-furnace operation device includes a base portion 44 erected on the CRD housing 26 adjacent to the CRD housing 26 to be worked, an elevating shaft 56a that moves up and down with respect to the base portion 44, and an elevating shaft 56a. , And supported by bearings 53, and a spur gear 47
And a turning shaft 56b that turns around the vertical axis of the elevating shaft 56a. A shot peening nozzle 55 is attached to the tip of the turning shaft 56b toward the inner surface of the CRD housing 26. I have. Pivot axis 56
A projection tube 56 is attached to the upper end of b through a swivel joint 45. The elevating shaft 56a is
A linear motion screw 52 fixed to the nut, a nut 51 screwed to the screw, a motor 48 for rotating the nut, a timing belt 49, and the like perform a vertical movement.

In this embodiment, an inspection tool such as VT and UT is used instead of the shot pinning head 55.
By installing a repair tool such as a welding torch or a cutting tool such as an EDM electrode, inspection of welds,
Repair and replacement work can be easily performed.

(Embodiment 6) FIG. 8 shows a state in which water at the bottom of the furnace is drained and injected into the annulus as a measure for shielding radiation. 1 shows a configuration example of an apparatus for performing shot pinning. In this apparatus, as in the case of FIG. 1, an operator performs shot peening of the furnace bottom from the work base 7 at the furnace bottom, and is attached to the tip of an operation pole (not shown). , A means for facilitating management of construction conditions such as a projection distance and an angle of the shot 59, and a collection nozzle 58 for collecting a shot used for construction by suction. That is, the projection nozzle 57 is provided at the tip of the shot direct pipe 65, and the collection nozzle 58 is provided at the tip of the collection straight pipe 66. Further, wheels 60 supported by a combination of a spring 61 and a linear bush 67 so as to be able to move up and down linearly are provided at three points with respect to the construction surface, and stoppers 70 fixed to a support member that moves directly with each wheel 60 are provided. And the limit switch 62 can be input ON / OFF. In addition, above the stopper 70,
Similarly, a stopper 69 is provided on a shaft 68 supported by wheels 60 and linearly moved by a linear bush 67, and is connected via a shaft 72 movably disposed by a combination of a linear guide 71 and a spring 64. The set limit switch 63 can be turned ON / OFF by raising the stopper 69.

In FIG. 8, if the projection distance in the construction conditions is long, the signals of the limit switches 62 are all OF.
F, and if too close, one of the signals of the limit switch 63 is turned off. The projection angle in the construction conditions is set so that any signal of the limit switch 62 is turned off when the appropriate projection angle condition is not satisfied, centering on 90 degrees. Although not shown, the construction speed can be managed by detecting the rotational speed or the rotational position of the wheel 60. Further, even when the shot 59 projected during the construction stops in a narrow part, the shot can be sequentially collected by the collection nozzle 58.

As described above, since the work conditions can be managed to some extent in the same manner as the automatic machine even in the work by the worker, the work quality can be improved. In addition, since the shot collecting operation can be performed by using the idle time of the construction, the later shot collecting operation is facilitated, and the collecting nozzle 58 is efficiently applied to the shot stopping place to improve the collecting work efficiency. Can be achieved.

(Embodiment 7) FIG. 9 shows an example of the construction of an in-furnace working device 73 for inspecting, repairing, and modifying the surface of the jet pump diffuser 6 after the old core shroud is removed. Numeral 10 shows an enlarged part in the state of use.

In FIG. 9, the old core shroud is cut and removed, and the inside of the reactor pressure vessel 1 is chemically decontaminated. On the CRD housing 26, a scaffold (not shown) on which an operator can work is assembled. The in-furnace working device 73 includes a base 74 erected on the CRD housing 26, an elevating shaft 75 that moves up and down the base 74, and is disposed on the elevating shaft 75, and is driven around a vertical axis. A swing shaft 76, a swing shaft 77 attached to the swing shaft 76 via an arm link 83 a, and an elevating shaft 84 attached to the swing shaft 77 via an arm link 83 b. As shown in FIG. 10, wheels 78 are disposed on the outer surface of the elevating shaft 84 via a compliance mechanism 86 so as to guide along the reactor pressure vessel 1 and apply a load. A swivel shaft 79 is arranged in the elevating shaft 84 via a guide bush 89, and the swivel shaft 79 is moved up and down by an elevating mechanism composed of a motor 93 and a rack and pinion 92. On an outer surface of a portion to be inserted into the diffuser 6 above the turning shaft 79, wheels 80 are disposed on a circumference via a compliance mechanism 87. At the upper end of the turning shaft 79, a head portion 88 is arranged,
The lower end is inserted into the turning shaft 79 via the bearing 88a. A turning mechanism including a motor 90 and a spur gear 91 is arranged in the turning shaft 79.
Numeral 1 engages with a gear formed on the outer surface of the lower end of the head 88 to rotate the head 88. A tool 95 is provided at the upper end of the head 88 via a tilt shaft 81.

As shown in FIG. 10, when a shot peening head is used as a tool of the working device 73, a turning shaft 79 inserted into the jet pump diffuser 6 is used.
A seal member 100 is disposed on the inside of the diffuser 6 in close contact with the inside of the diffuser 6, and a suction nozzle 96 is disposed between the seal member 100 and the cylindrical portion 94. A suction tube 98 is routed below the suction nozzle 96 and is connected to a collection unit (not shown). A shot projection nozzle 95 connected to the tool tip via a flexible tube 102 on the way
Is disposed, and the inside of the turning shaft 79 is shot by the shot projection tube 9.
7 is provided via a swivel joint 101. The other end of the shot projection tube 97 is connected to a shot projection unit (not shown).

When the in-furnace working device 73 having such a configuration is used, as shown in FIG. 9, the base portion 74 is erected on the CRD housing 26, and the turning shaft 76 and the turning shaft 7 are arranged.
7, the diffuser 6 below the baffle plate 3
It is positioned so that the center of the turning shaft 79 coincides downward. At this time, the angle is also determined so that the wheel 78 comes into contact with the inner wall of the reactor pressure vessel 1 to partially support the overturning moment. Next, the lifting / lowering mechanisms 92 and 93 are operated to rotate the pivot shaft 7.
9, insert the tip into the diffuser 6,
The tip is raised with the wheel 80 disposed outside the pivot 79 protruding from the inner wall. Thus, the pivot 7
9, the elevation shaft 84 and the tilt shaft 81 are driven to set the position and orientation of the tool 95 at the tip and perform the work. When the tool is a shot peening head, after inserting the cylindrical portion 94 into the diffuser 6 until the sealing material 100 disposed on the cylindrical portion 94 comes into close contact with the inner wall of the diffuser 6 as described above, The peening projection nozzle 95 is positioned at a target construction site, and a shot 99 is projected.
At this time, the shot 9 accumulated on the upper surface of the sealing material 100
9 is collected through a suction nozzle 96 and a suction tube 98.

According to the present embodiment, it is possible to easily perform a surface modification treatment such as shot peening, inspection, and repair on the welding line 85 inside the jet pump diffuser 6, which was conventionally very difficult to access. Thus, the exposure of the workers can be reduced. Further, in the case of this construction method, the shots are constantly collected, so that the shot collecting and cleaning operation can be omitted, and the process can be shortened.

(Embodiment 8) FIG. 11 shows an example of the configuration of a shot pinning device for the inner surface of a jet pump diffuser 6. After cutting and removing the existing shroud, in an aerial environment from which the inlet mixer has been removed, a shot pinning device is inserted from above and an inner surface weld is constructed. The entire shot pinning device is an upper positioning mechanism 1
08 and the centering mechanism. This centering mechanism is composed of links 111, wheels attached to their ends, and a cylinder piston 114 for applying a leg opening force to each link. Further, the portion inserted into the diffuser 6 has a double pipe structure of a revolving member 109 and an elevating member 110, and a rail 1 is provided on the outer surface of the elevating member 110 on the outer tube side.
19, the motor 107 and the rack and pinion 1
06 allows the shot peening head to move up and down. Reference numeral 120 denotes a linear guide.

At the lower end of the turning member 109 on the inner tube side, a shot pinning head 113 is installed via a rotating shaft 115 and a cylinder piston 114 toward the inner surface of the tube. Wheels 112 are attached to the tips of the heads 113, and cooperate with cylinder pistons 114 to keep the distance between the shot pinning head 113 and the inner surface of the diffuser 6 constant. The turning member 109 is supported at both upper and lower ends by bearings 105 and 117, and is turned by a drive mechanism including a motor 121 and a gear 122. This allows the shot peening head 113 to move freely in the circumferential direction. The lower end of the shot projection tube 104 is connected to the shot pinning head 113 via a swivel joint 116. Reference numeral 103 denotes a hanging tool. The above-described lifting / lowering mechanism and the turning mechanism enable the shot peening head to be accurately positioned at an arbitrary position on the inner surface of the diffuser 6.

A similar mechanism can be applied to the inner surface of the jet pump riser tube. In addition, by installing an inspection tool such as VT and UT, a repair tool such as a welding torch, and a cutting tool such as an EDM electrode in place of the shot pinning head, inspection, repair, and replacement of a welded portion can be easily performed.

Example 9 A SUS316L shroud girth weld simulated test piece (500 × 1000 × 40 tmm) was prepared, and a welding wire was welded to the weld using a polishing tool in which an alumina abrasive was impregnated with resin. / An area of 40 mm from the base material boundary was overlapped five times to perform construction. FIG. 12 shows the results of measurement of the surface residual stress distribution before and after the construction measured by the X-ray stress measurement method. A tensile residual stress of up to 350 MPa is formed near the weld before the construction, but 300 to 4
It can be seen that a high compressive stress of 50 MPa was formed.

[0036]

According to the present invention, the inspection of the reactor internals, the preventive maintenance technology for converting the tensile residual stress of the welded portion to the compressive stress and the repair technology can be performed in a short time, at a low cost, and in a short time. It is possible to improve the reliability and extend the life of the nuclear co-plant.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a state in which a process of applying a compressive stress to a furnace bottom welded portion is being performed in the method of the present invention.

FIG. 2 is a graph showing an example of stress measurement before and after shot peening of a stub tube simulation specimen.

FIG. 3 is a schematic diagram illustrating a CRD stub tube outer surface application apparatus used in the method of the present invention.

FIG. 4 is a schematic diagram illustrating a new shroud / shroud support cylinder weld application system used in the method of the present invention.

FIG. 5 is a graph showing an example of stress measurement before and after shot peening of a new shroud / shroud support cylinder simulation specimen.

FIG. 6 is a schematic view illustrating a baffle plate welding part installation apparatus used in the method of the present invention.

FIG. 7 is a schematic view illustrating a CRD stub tube inner surface construction apparatus used in the method of the present invention.

FIG. 8 is a schematic diagram illustrating a furnace bottom construction apparatus used in the method of the present invention.

FIG. 9 is a schematic view illustrating a jet pump diffuser inner surface construction apparatus used in the method of the present invention.

FIG. 10 is a schematic diagram showing a use state of the device of FIG. 9;

FIG. 11 is a schematic view showing another example of the jet pump diffuser inner surface construction apparatus used in the method of the present invention.

FIG. 12 is a graph showing an example of stress measurement before and after polishing of a new shroud simulation sample.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Reactor pressure vessel 2 ... New shroud 3 ... Baffle plate 4 ... Shroud support leg 5 ... CRD housing 6 ... Jet pump diffuser 7 ... Work base
8: Shot supply device 11: Shroud support cylinder 12: Swivel mechanism
14 ... Base 15 ... Elevating shaft 18 ... Nozzle 25 ... Straight tube 26 ... Housing 27 ... Stub tube 28 ... Guide rail 31 ... Traveling car 32 ... Peening head 35 ... Traveling car 42 ... Arm
43 ... cut surface 44 ... base part 51 ... nut 52 ... direct acting screw 55 ...
Projection nozzle 56a ... Elevating shaft 56b ... Revolving shaft 57 ... Projection nozzle
58… Recovery nozzle 59… Shot 62, 63… Limit switch 65… Straight pipe for projection 66… Straight pipe for recovery 73… Working equipment in furnace 74… Base
75 ... Elevating shaft 76,77,79 ... Swivel shaft 81 ... Tilt shaft 85 ... Welding line 86,87 ... Compliance mechanism 92 ... Rack and pinion
95 ... Projection nozzle 96 ... Suction nozzle 100 ... Sealing material 108 ... Positioning guide 109 ... Revolving member 110 ... Elevating member 111 ... Centering mechanism (link mechanism) 114 ... Cylinder piston 119 ... Rail 120 ... Linear guide

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI G21C 19/02 G21F 9/28 525Z G21F 9/28 525 9/30 ZAB 9/30 ZAB 531E 531 G21C 17/00 E (72) Inventor Toru Otsubo 8 Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa Pref.

Claims (11)

[Claims] 1. The reactor pressure vessel upper lid, the upper part of the shroud and the internal structure of the shroud are removed, the inside of the reactor is chemically decontaminated using a chemical, the shroud support cylinder is cut, and the reactor water is drained. In the shroud replacement process, the jet pump riser pipe, jet pump diffuser, jet pump riser brace arm, water level instrumentation nozzle, recirculation nozzle, water supply nozzle, CRD stub tube, incore monitor housing , Shroud support, support leg, shroud head, steam dryer, core spray piping, baffle plate, upper grid plate, core support plate, etc. Core shroud characterized by performing How to replace 2. Inspection of a portion to be subjected to compressive stress before applying compressive stress, and further, when damage such as a defect is found, repairing by thermal means or mechanical means, or replacing the equipment. The method for exchanging a core shroud according to claim 1, wherein: 3. The inspection means includes: VT inspection, ultrasonic flaw detection, R
3. The method for exchanging a core shroud according to claim 2, wherein the method is one of a T inspection and an eddy current inspection. 4. A repair method using thermal means is any one of surface melting by laser irradiation, laser cladding, build-up welding by laser or TIG, and patch application welding, and the mechanical means is defect removal by grinding. 3. The method of claim 2, wherein the patch is bolted. 5. After cutting and removing the existing shroud from the shroud support, lowering the furnace water level below the baffle plate, compressing the welded portion of the jet pump riser pipe, the jet pump riser brace arm or the jet pump diffuser. The method for exchanging a core shroud according to claim 1, wherein processing for applying stress, repairing, or exchanging each part is performed. 6. Various operations inside the jet pump diffuser are performed by an ultrasonic probe, an eddy current probe, which is erected on a CRD housing in a reactor pressure vessel and is attached to a tip inside the reactor pressure vessel. TV camera, PT device, ED
Drive for positioning tools such as M electrode, grinder, welding head, polishing tool, hammer pinning head, shot pinning head, water jet pinning nozzle, and guide for guiding the tip along the reactor pressure vessel Wheels, a positioning mechanism for inserting the tip into the jet pump diffuser, a guide wheel whose tip is centered on the inner surface of the diffuser, and an in-furnace working device including a drive unit that positions a tool on the inner surface of the diffuser. 6. The method for exchanging a core shroud according to claim 5, wherein the method is performed using the core shroud. 7. Various operations inside a jet pump diffuser or a jet pump riser pipe are performed by removing an inlet mixer, and then installing an ultrasonic probe, an eddy current probe, a television camera, a PT device attached to a tip from an upper opening. , EDM electrode, grinder, welding head, polishing tool, hammer pinning head, shot pinning head, water jet pinning nozzle, etc., a drive unit to position tools, and a tip to be inserted into the jet pump diffuser Mechanism and diffuser,
The method according to claim 5, wherein the operation is performed using a guide wheel whose tip is centered on the inner surface of the riser tube, a diffuser, and an in-furnace working device including a driving unit that positions a tool on the inner surface of the riser tube. How to replace core shroud. 8. After sealing the outside of the new shroud, inject water into the downcomer, shield radiation from the jet pump and the pressure vessel, drain all reactor water from the furnace bottom, and apply compressive stress to the weld at the furnace bottom. 2. The method for exchanging a core shroud according to claim 1, wherein the applied, repaired or exchanged work is performed. 9. The reactor pressure vessel upper lid, the upper part of the shroud and the internal structure of the shroud are removed, the inside of the reactor is chemically decontaminated using chemicals, the shroud support cylinder is cut, the reactor water is drained, and a new shroud is welded. A method of exchanging a core shroud, comprising: performing a process of applying a compressive stress to a shroud support and a new shroud welded part. 10. The reactor pressure vessel upper lid, the upper part of the shroud and the internal structure of the shroud are removed, the inside of the reactor is chemically decontaminated using a chemical, the shroud support cylinder is cut, the reactor water is drained, and a new shroud is welded. A method of exchanging a core shroud, comprising: applying a compressive stress to a new shroud weld in advance. 11. A method for applying a compressive stress includes shot peening, pulsed laser irradiation, hammer peening,
The method for exchanging a core shroud according to any one of claims 1, 5, 8, 9, and 10, wherein the method is one of polishing and water jet pinning.