JPH09230086A - Apparatus and method for repairing in-core structure - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: It is possible to modify a stress state change on a metal surface without requiring collection of shot balls, preventing deterioration of working environment due to dust generation by shots, and requiring no reaction force compensation. An apparatus and method for repairing an internal structure of a furnace are provided. SOLUTION: An arm 2 is mounted on a pole 5 via a bracket 3.
And the rod peening device 1 is attached to the tip of this arm 2. The rod peening process is performed while moving the rod peening apparatus 1 on the surface to be repaired in predetermined ranges. The pole 5 is connected to a fuel exchanger above the reactor pressure vessel and is operated remotely. This rod peening apparatus 1 is formed by forming a spherical portion 37 at the tip of a large number of large diameter rods 35 via a flexible rod 36, and the spherical portion 37 violently reciprocates by alternately flowing high pressure gas. . When this spherical portion 37 is applied to the surface to be repaired, the reciprocating motion can modify, for example, the heat affected zone of the welding line from tensile stress to compressive stress.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and method for repairing an internal structure of a reactor installed in a reactor pressure vessel in a light water cooled reactor.

[0002]

2. Description of the Related Art The internal structure of a light water cooling type nuclear reactor is made of a material such as austenitic stainless steel or nickel base alloy which has sufficient corrosion resistance and high temperature strength under high temperature and high pressure water environment.

However, non-replaceable members are exposed to a high temperature and high pressure environment for a long period of time due to long-term operation of the plant, and the core materials such as shrouds are irradiated with neutrons, which causes them. There is concern about the problem of material deterioration that occurs. Particularly, in the vicinity of the welded portion of the in-core structure, there is a risk of potential stress corrosion cracking because the material becomes sensitized by welding heat input and tensile residual stress is formed.

Recently, various material surface modification suspicions have been developed as preventive maintenance technology measures in response to the extended operation period of the plant. As a result, a countermeasure method is being developed to prevent stress corrosion cracking by positively changing the surface residual stress from tensile to compression.

For example, a technique for improving surface residual stress by a method such as shot peening or water jet peening is being developed. Shot peening is a technology that accelerates a steel ball of about 0.3 to 1.2 mm using high pressure air or centrifugal force and plastically deforms the surface of the construction part by the kinetic energy of the steel ball to form a compressive residual stress on the surface. .

In addition, water jet peening requires 10
It is a technology that forms a compressive residual stress on the surface by jetting ultra-high pressure water of about 00 atm from the tip of the nozzle and by a shock wave when the water hammer action and cavitation break. Both of them have been proved to be effective against stress corrosion cracking by construction in water and have been partially put into practical use.

An underwater television camera was attached to the tip of the mast or rod to check the integrity of the equipment between the shroud and the reactor vessel installed in the reactor upper chamber of the light water cooled reactor and the surface of both. The device is used for visual inspection, but no work has been done to change the surface stress state of the structure.

Further, an underwater swimming type inspection robot for visual inspection having a higher degree of freedom is used. However, this is also for visual inspection, and work to change the surface stress state of the structure has not been performed.

[0009]

When using shot peening to improve the surface residual stress of a structure in a narrow part such as an annulus part between a shroud and a reactor pressure vessel, it is difficult to completely recover shot balls. Is. In addition, when the work is performed in the atmosphere, problems such as generation of dust occur, and there is a problem that the work becomes difficult.

When the work for changing the surface stress of a structure is performed by using water jet peening, a jet reaction force is generated. Therefore, an automated device for performing a work for changing a precise surface stress state by remote control in a narrow place is required. Developing is a daunting task.

The present invention has been made in order to solve the above-mentioned problems, and it is possible to perform a treatment equivalent to the shot peening treatment, and it is not necessary to collect shot balls during the shot peening treatment. Reactor internal structure that can prevent the deterioration of the work environment due to the generation, and can modify the stress state change of the metal surface that does not generate reaction force like water jet peening and does not require reaction force compensation An object of the present invention is to provide a repairing device and method.

[0012]

The invention according to claim 1 is directed to an arm that is vertically movable and rotatable so as to face a structure installed in a reactor pressure vessel, and a tip portion of the arm. Equipped with a rod peening device attached to
The rod peening device includes a body, a large number of large-diameter rods housed in the body to form flexible rods, a hard spherical portion formed on the flexible rod, and a reciprocating motion of high pressure gas to the spherical portion. And a high pressure hose attached to the body.

According to the present invention, the weld between the shroud and the upper lattice plate of the light water cooled reactor and its vicinity, between the core spray pipe and the shroud upper ring provided inside the shroud, and the lower part of the core support plate. A jet pump riser brace arm installed between the shroud and the lower ring of the shroud and its vicinity, between the shroud and the core support plate, between the reactor pressure vessel and the shroud,
Compress the tensile stress state in the narrow part of the internal structure such as riser pipe, jet pump diffuser surface, shroud inner and outer surfaces, shroud support inner and outer surfaces, reactor pressure vessel inner surface, control rod drive mechanism housing outer surface. It can be easily modified and its life can be extended without damaging the equipment.

According to a second aspect of the present invention, a fuel is provided in which the upper end of the arm is attached to a bracket, the bracket is connected to the lower end of a pole, and the upper end of the pole is installed above the reactor pressure vessel. Connected to the exchange, attached to the lower part of the bracket is a lower roller that travels on the upper surface of the upper lattice plate installed in the reactor pressure vessel, and projects a thin ring onto the shroud upper ring installed in the reactor pressure vessel. The upper roller that runs on the thin ring is attached to the upper end of the pole.

According to the present invention, the upper end of the pole is connected to the refueling machine, the bracket is connected to the lower end of the pole, and the rod peening device is attached to the bracket through the arm. Also, an upper roller is attached to the pole, the upper roller is placed on a thin ring above the shroud, a lower roller is attached to the lower portion of the bracket, and the lower roller is placed on the upper surface of the upper lattice plate.

When the pole is moved, the upper roller moves along the thin ring, so that the lower roller is also guided by the upper roller and moves on the upper lattice plate.
Along with this, the rod peening device also moves. When the rod peening device is run in a certain range and high-pressure gas is supplied, the spherical member reciprocates to peening the surface to be repaired.

According to a third aspect of the present invention, a vertically movable and rotatable arm is attached to face a structure installed in the reactor pressure vessel, and a rod peening device is attached to the tip of this arm. This rod peening device is made to run or rotate close to the narrow part of the internal structure, and a hard spherical part formed at the tip of the rod of the rod peening device gives a violent reciprocating motion to the narrow part. It is characterized by performing shot peening processing.

According to the present invention, since the spherical portion formed at the tip portion of the flexible rod is subjected to the peening process by the reciprocating motion, the spherical portion is not cut and scattered from the flexible rod. Therefore, unlike the shot peening process, it is not necessary to collect the shot balls, and it is possible to prevent the working environment from being deteriorated due to the generation of dust by the shot balls. Furthermore, the stress transformation of the metal surface can be modified without the need for reaction force compensation as in the water jet peening process.

According to a fourth aspect of the present invention, the narrow portion of the reactor internal structure is provided inside the shroud and a welded portion between the shroud installed in the reactor pressure vessel and the upper lattice plate. Between the core spray pipe and the shroud upper ring, the lower shroud below the core support plate installed in the reactor pressure vessel and the welded part of the shroud lower ring and its vicinity, the shroud and the core support plate Between the reactor pressure vessel and the shroud, the jet pump riser brace arm, the riser pipe, the surface of the jet pump diffuser, the inner and outer surfaces of the shroud, the inner and outer surfaces of the shroud support, and the inner surface of the reactor pressure vessel. , It is characterized in that it consists of the outer surface of the control rod drive mechanism housing.

According to the present invention, the rod peening apparatus can perform the peening treatment while traveling through the repaired portion of the narrow portion of the reactor internal structure in a predetermined range, so that the stress state of the metal surface can be improved to a predetermined value. Therefore, it is possible to prolong the life of the equipment without causing stress corrosion damage to the structural material.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment of an apparatus and method for repairing a reactor internal structure according to the present invention will be described with reference to FIGS. 1 to 3. FIG. 1 is a vertical cross-sectional view showing a repair device for repairing a narrow space between a shroud 9 and an upper lattice plate 19 in a reactor internal structure of the present embodiment and a partial side view for explaining the method. 2 is a plan view seen from the direction of arrow AA in FIG. 1, and FIG. 3 shows the rod peening apparatus 1 in FIG. 1 in an enlarged manner.

In the figure, reference numeral 1 is a rod peening device,
The rod peening apparatus 1 is connected to an arm 2, and the tip of the arm 2 is connected to a bracket 3 by a bolt 4. The bracket 3 is connected to the lower end of the pole 5. Although not shown, the upper end metal fitting 6 of the pole 5 is connected to a fuel exchanger installed above the reactor pressure vessel.

A roller mounting member 7 is attached to the upper portion of the pole 5, and an upper roller 8 is mounted on the roller mounting member 7. The upper roller 8 is mounted on and guided by a thin ring 11 projectingly mounted on the upper ring 10 of the shroud 9.

A plate 12 is attached to the upper portion of the bracket 3, and a terminal fitting 13 is fixed to the plate 12 by a nut 14, and a wire 15 is inserted into the terminal fitting 13. A rod 16 is attached to the lower portion of the bracket 3, a roller holder 17 is connected to the lower end of the rod 16, and a lower roller 18 is attached to the roller holder 17. The lower roller 18 contacts the upper surface of the upper lattice plate 19 and runs.

A high pressure gas hose 20 is connected to the rod peening apparatus 1, and an upper portion of the high pressure gas hose 20 is connected to a compressor (not shown) provided above the reactor pressure vessel. An upper lattice plate cradle 21 for holding the upper lattice plate 19 inside the shroud 9 is provided below the upper lattice plate 19.

A shroud pedestal 22 is provided in the lower portion of the shroud 9, and a cover 24 is formed by bridging the lower part of the intermediate ring 23 of the shroud 9 on which the shroud pedestal 22 is placed and the upper grid plate pedestal 21. Is attached. FIG.
Reference numeral 25 indicates a lug, and 26 indicates a core spray pipe.
The cover 24 is attached to an auxiliary work unit (not shown) from below the upper lattice plate 19 and moved to the relevant part.

In FIG. 2, reference numeral 27 is a plurality of seismic resistant blocks installed between the shroud 9 and the outer diameter 28 of the upper lattice plate, and the seismic resistant blocks 27 have the same shape as that of FIG. 4 described later. A wedge 29 and a wedge 33 are fixed to the lower surface of the upper lattice plate 19 by a plurality of pins 31.

The cover 24 has several hinges 30 incorporated therein and is foldable so that the cover 24 can be opened and used after being inserted from the lattice of the upper lattice plate 19. Reference numeral 32 is an eyebolt, and a plurality of eyebolts are attached to the upper surface of the upper lattice plate 19. The wedge 33 is inserted between the pedestal 21 of the upper lattice plate and the shroud 9 to prevent the upper lattice plate 19 from moving.

As shown in FIG. 3, the rod peening apparatus 1 has a large number of large-diameter rods 35 bundled and housed in a cylindrical body 34, and the distal end of the large-diameter rod 35 has a small-diameter flexible rod 36. The flexible rod 36 has a hard spherical portion 37 formed at its tip. The outside of the bundle of large-diameter rods 35 is surrounded by a guide 38 to limit the range, and the guide 38 is fixed to the body 34 by a set screw 39.

The high pressure gas hose 20 is connected to the lower end of the body 34 by a hose joint 40. When high pressure gas flows from the high pressure gas hose 20 into the body 34, the flexible rod
The portion 36 violently reciprocates, and the spherical portion 37 reciprocates accordingly. That is, the high-pressure gas (not shown) alternately flows into the body 34 through two holes, and the spherical portion 37 reciprocates. When the spherical portion 37 is brought into contact with the surface to be repaired, the portion is work hardened to be in a compressive stress state. The spherical portion 37 is formed in the same shape as the shot ball.

When a small force is applied to a tensile stressed member, the member is pulled. When a force is applied to a member with compressive stress, it returns to the original stress, when more force is applied it becomes tensile stress, and when more force is applied it is pulled, and by repeating this, it is possible to modify the tensile stress to a compressive stress state. it can.

In the first embodiment described above, the pole 5 is connected by the wire 15 from the upper part of the reactor pressure vessel (not shown).
The lower roller 18 is placed on the upper lattice plate 19 at the center of the hanging core (not shown). The rod peening device 1 attached to the tip of the arm 2 is oscillated and scanned by a predetermined range to perform rod peening processing on the welded portion of the shroud 9 and the intermediate ring 23. In this case, high-pressure gas flows from the high-pressure gas hose 20 into the body of the rod peening apparatus 1. The high-pressure gas is supplied from outside the furnace by remote control. The operation of the rod peening process is as described above.

As described above, according to the present embodiment, the narrow portion of the shroud 9 and the intermediate ring 23 can be performed by the rod peening process in the same manner as the shot peening process. The spherical portion 37 does not scatter because of the rod peening treatment by the spherical portion 37 formed on the flexible rod 36. Therefore, unlike the shot peening process, it is not necessary to collect the shot spheres, and because the shot spheres do not generate dust, it is possible to prevent the work environment from deteriorating. The stress transformation of the metal surface can be modified without the need for

Next, a second embodiment of the apparatus and method for repairing the internal structure of the reactor according to the present invention will be described with reference to FIGS. 4 and 5. 4 and 5, the same parts as those of FIGS. 1 to 3 are designated by the same reference numerals, and the description of the overlapping parts will be omitted.

The present embodiment is different from the first embodiment in that the rod peening apparatus 1 is moved to the narrow portion of the inner corner of the shroud 9 and the upper ring 10 to perform the rod peening treatment.

In FIGS. 4 and 5, a core spray pipe 26 is arranged inside the shroud 9, and a support plate 41 is partially installed to hold the core spray pipe 26. Therefore, the gap between the shroud 9 and the core spray pipe 26 is narrowed. Seismic block 27 and wedge between shroud 9 and upper lattice plate 19
29 is interposed, and the wedge 29 is fixed by a fixing member 42.

According to the present embodiment, the surface stress in the vicinity of the welded portion of the narrow portion between the shroud 9 and the upper ring 10 can be improved by using the rod peening apparatus 1. Other functions and effects are the same as those in the first embodiment, and therefore their explanations are omitted.

Next, referring to FIGS. 6 and 7, a third embodiment of the method for repairing the internal structure of the reactor according to the present invention will be described.
Note that FIG. 7 shows a plan view of FIG. The present embodiment is a welded portion of the narrow portion between the lower ring 43 and the lower shroud 44.
There is rod peening near 45.

In FIG. 6, a lower ring 43 is fixed to the lower end of the shroud 1, and a lower shroud 44 is connected to the lower surface of the lower ring 43 via a welded portion 45. A core support plate 46 is provided on the lower ring 43 via a tightening stud 47, and the upper end of the tightening stud 47 is fixed to the upper part of the core support plate 46 by a nut 49 via a spherical washer 48 and the lower end. The lower part of the core support plate 46 is fixed by a nut 51 via a spherical washer 50.

The rod peening apparatus 1 is arranged near the inside of the welded portion 45, and the underwater television camera 52 is arranged below the rod peening apparatus 1. The nut 49 on the upper portion of the tightening stud 47 is protected by the nut keeper 53. In FIG. 7, reference numeral 54 is a measurement pipe, 55 is an Inconia monitor guide pipe, and 56 is a control rod guide pipe insertion hole.

A core support plate 46 is placed on the lower ring 43, and is fixed to the shroud 9 by tightening studs 47. The tightening stud 47 has upper and lower spherical washers 48 and 50 incorporated therein and is tightened by nuts 49 and 51. A nut keeper 53 is attached to the upper nut 9.
The surface peening can be accurately performed while monitoring by the underwater television camera 52 using the rod peening device 1 capable of improving the surface stress even in the vicinity of the welded portion 45 in a narrow place below the core support plate 46. .

Next, the function and effect of the embodiment will be described.
The tip part of the rod peening connects the spherical part 37 of the hard steel ball to the flexible rod 36 or forms it, and reciprocates the spherical part 37 back and forth to perform surface modification repair in water (compressed from a tensile stress state. Repair work that changes to a stress state) can be performed. Therefore, the work of changing the tensile stress state of the welding line and the surface of the shroud 9 to the compressive stress state can be easily performed in a short period of time by remote operation in water.

Since the spherical portion 37 is formed in the middle of the tip portion of the large-diameter rod 35 via the flexible rod 36, the spherical portion 37 does not scatter. Therefore, unlike shot blast peening, the work of collecting shot balls is unnecessary. Further, rod peening is capable of continuously moving and scanning the surface using a remote device.

[0044]

According to the present invention, it is not necessary to collect shot balls, to prevent deterioration of the working environment due to dust generation due to shots, and to change the stress state of metal without requiring reaction force compensation. It can be performed.

Further, the stress state of the metal surface in the narrow portion of the reactor internal structure can be modified from the tensile stress to the compressive stress state, and the life of the reactor internal structure material can be extended without causing stress corrosion damage. You can

Moreover, the jet pump riser brace arm, the riser pipe, the surface of the jet pump diffuser, the surface of the shroud, the inner and outer surfaces of the shroud, and the shroud support are installed not only in the narrow part of the internal structure of the reactor but also between the shroud and the reactor pressure vessel. It is possible to easily surface-reform the stress state of the inner and outer surfaces of the reactor, the inner surface of the reactor pressure vessel, the outer surface of the control rod drive mechanism housing, etc.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing a part of a side view for explaining a first embodiment of an internal structure repairing apparatus and method according to the present invention.

FIG. 2 is a top view seen from the direction of arrow AA in FIG.

FIG. 3 is a side view showing the rod peening apparatus in FIG. 1 in a partial cross section.

FIG. 4 is a vertical cross-sectional view showing a second embodiment of a device for repairing internal reactor structure and a method therefor according to the present invention in a partial side view.

FIG. 5 is a plan view in FIG. 4;

FIG. 6 is a vertical cross-sectional view showing a third embodiment of a device for repairing internal reactor structure and a method therefor according to the present invention in a partial side view.

FIG. 7 is a plan view in FIG. 6;

[Explanation of symbols]

1 ... Rod peening device, 2 ... Arm, 3 ... Bracket, 4 ... Bottle, 5 ... Pole, 6 ... Upper end fitting, 7 ... Roller mounting fitting, 8 ... Upper roller, 9 ... Shroud, 10 ...
Upper ring, 11 ... Thin ring, 12 ... Plate, 13 ... End fitting, 14 ... Nut, 15 ... Wire, 16 ... Rod, 17 ... Roller holder, 18 ... Lower roller, 19 ... Upper lattice plate, 20 ... High pressure gas hose, 21 ... Upper lattice plate pedestal, 22 ... Shroud pedestal, 23 ... Intermediate ring, 24 ... Cover, 25 ... Lug, 26 ... Core spray piping, 27 ... Seismic block, 28 ... Upper lattice plate outer diameter, 29 ... Wedge , 30 ... Hinji, 31 ... Pin, 32 ... Eyebolt, 33 ... Wedge, 34 ... Body, 35 ... Large diameter rod, 36
… Flexible rod, 37… Ball, 38… Guide, 39…
Set screw, 40 ... Hose fitting, 41 ... Support spray, 42
... Fixing member, 43 ... Lower ring, 44 ... Lower shroud, 45
… Welds, 46… Core support plates, 47… Tightening studs, 48, 50
… Spherical washer, 49,51… Nut, 52… Underwater TV camera,
53 ... Nut keeper, 54 ... Measuring pipe, 55 ... In-core monitor guide pipe, 56 ... Control rod guide pipe insertion hole.

Claims (4)

[Claims] 1. A rod peening apparatus attached to a tip end of the arm, the arm being vertically movable and rotatable so as to face a structure installed in a reactor pressure vessel, and the rod. The peening device includes a body, a large number of large-diameter rods housed in the body and formed with flexible rods, a hard spherical portion formed on the flexible rod, and a reciprocating motion to the spherical portion by high-pressure gas. And a high-pressure hose attached to the body. 2. The upper end of the arm is attached to a bracket, the bracket is connected to a lower end of a pole, and the upper end of the pole is connected to a fuel exchanger installed above the reactor pressure vessel. A lower roller that runs on the upper surface of the upper lattice plate installed in the reactor pressure vessel is attached to the lower part of the reactor, and a thin ring is projected on the shroud upper ring installed in the reactor pressure vessel. The apparatus for repairing the internal structure of the reactor according to claim 1, wherein an upper roller that runs is attached to an upper end portion of the pole. 3. A vertically movable and rotatable arm is attached so as to face a structure installed in a reactor pressure vessel,
A rod peening device is attached to the tip of this arm, and this rod peening device is made to run or rotate close to the narrow part of the internal structure of the furnace, and the rod peening device has a hard spherical shape formed at the tip of the rod. A method for repairing an internal structure of a reactor, characterized in that a shot peening treatment is performed by violently reciprocating the narrow portion at the section. 4. A narrow portion of the internal structure is a welded portion between a shroud installed in the reactor pressure vessel and an upper lattice plate and its vicinity, a core spray pipe provided inside the shroud, and an upper portion of the shroud. A ring, a weld between a lower shroud of the core support plate installed in the reactor pressure vessel and the shroud lower ring and its vicinity, between the shroud and the core support plate, and a reactor pressure. Jet pump riser brace arm installed between vessel and shroud, riser pipe, surface of jet pump diffuser, inner and outer surfaces of shroud, inner and outer surface of shroud support, inner surface of reactor pressure vessel, control rod drive mechanism housing The method for repairing the internal structure of the reactor according to claim 3, wherein the method comprises repairing the internal surface.