JPH08146188A - Defect repairing method for nuclear reactor internal structure - Google Patents

Abstract

PURPOSE: To lengthen the life of a nuclear power plant by providing a repairing method for a nuclear reactor internal structure with high safety for the earthquake load with pitching. CONSTITUTION: A tapered pin 300 is fixed from the shroud outer surface part. The tapered pin 300 and a contact plate 200 are fixed to the shroud inner surface. After the contact plate 200 and a defective part 100 are fastened, a tap is set up from the shroud outer surface part to conduct an internal threading work by use of an internal thread cutting device which is suspended from a crane and can be remote-operated. A screw which fits the size of the female screw is fitted in a taper part from the shroud outer surface part by using a thread fastening device which is suspended from the crane and can be remote- operated. The tapered pin 300 and the contact plate 200 are fixed to a defective part 100.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure defect repairing method, and more particularly to a method suitable for repairing defects in a reactor internal structure.

[0002]

2. Description of the Related Art Reactor internals, such as shrouds, are made of metal plates. As the shroud is used, defects such as cracks may occur at the butt-welded portion of the metal plate, the heat-affected zone of the welding, and the metal plate itself. This is because defects are more likely to occur due to deterioration of the material due to neutron irradiation in the nuclear reactor, and also due to various conditions such as temperature and material used for welding. Conventionally, in these repair methods, first, the vicinity of a portion where a defect such as a crack has occurred is cleaned, the defective portion is scraped off, and then the removed portion is repair welded from the inner surface and the outer surface of the structure. The second repair method is to place a backing plate on top of a defect such as a crack and fasten it with bolts.

[0003]

SUMMARY OF THE INVENTION In the first repair method,
Since the welding work is performed from the inner surface and the outer surface of the structure, it takes a long time and requires skill. Furthermore, the parts and equipment that receive neutron irradiation in the reactor pressure vessel,
For example, in neutron-irradiated shrouds, the welding process causes damage to the shrouds. Also,
In the second repair method, when a force is applied in the direction perpendicular to the bolt axial direction, since there is originally a gap between the bolt and the backing plate or the defective portion, not only is the bolt further loosened, but there is a defect. In the case of a crack, it is difficult to completely suppress the crack opening, which influences the subsequent crack growth, and it is not possible to completely repair a defective structure. In other words, the reliability of seismic loads with vertical shaking may not be clear. In addition, when the backing plate is fastened using bolts, the number of parts is large and the number of working steps is also complicated.

An object of the present invention is to provide a method of repairing the internal structure of a nuclear reactor, which is highly safe and reliable even against seismic loads accompanied by vertical shaking.

[0005]

In order to achieve the above object, the present invention has the following means as a method for repairing defects in reactor internals.

[0006] A first means is to cover a defective portion of the reactor internal structure with a patch plate, temporarily fix the patch plate to the defective portion, and then taper the hole having the defect and the patch plate. , Or processing a groove with a taper, a hole with a taper,
Alternatively, a tapered pin that fits in the groove is inserted into the hole or the groove, and the tapered pin is fixed to fix and fasten the portion including the defective portion and the backing plate.

The second means is to form a tapered hole or a tapered groove in a portion including a defect in the reactor internal structure, and to form a tapered hole or a tapered groove for fitting into the groove. It is characterized in that the patch plate having the pin portion fixes and fastens the patch plate and the patch plate.

A third means is that after fitting the defective portion and the backing plate, by inserting a fixing screw into the tapered pin or the backing plate having the tapered pin portion from the outer surface of the defective portion, It is characterized by fixing the tapered pin and the backing plate.

According to a fourth means, after fitting the defective portion and the backing plate, a tapered pin for fastening the defective portion to the backing plate or a defective portion on the head of the backing plate having the tapered pin portion It is characterized in that the tapered pin and the contact plate are fixed by covering the head with a washer from the outer surface part and by performing overlay welding on the head with the tapered pin or the part of the contact plate having the tapered pin part.

A fifth means uses a tapered head bifurcated pin which has been preliminarily processed so that the pin head is bifurcated, and after fitting the defective portion and the backing plate, the head bifurcated part of the bifurcated pin is used. The taper pin and the contact plate are fixed by bending the.

[0011]

According to the above structure, by using the tapered pin and the contact plate having the tapered pin portion, a force is exerted in a direction parallel to the inner surface of the structure having a defective portion such as seismic load accompanied by vertical shaking. Even when it works, the contact plate is not loosened because the tapered pin and the hole having the taper are fitted together. Further, by fixing the tapered pin and the pin portion of the backing plate having the tapered pin portion from the outer surface of the defective portion, the backing plate is securely fixed, and the effect of suppressing the opening of defects by the backing plate is ensured. .

[0012]

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

A flow chart of a method 10 of the present invention for crack repair is shown in FIG. This method 10 is a method of repairing defects in the butt welded portion, the weld heat affected zone, and the wall surface metal portion on the wall portion of the shroud in the reactor by using the contact plate and the tapered pin. Method 10 has four stages. The first step 1 is to cover the crack with a cover plate and temporarily fix the cover plate. The second step 2 is to machine tapered holes in the patch and defect areas. The third step 3 is to insert a tapered pin into the tapered hole that fits into the tapered hole processed in the second step 2. The fourth step 4 is a method of fixing the tapered pin from the outer surface of the shroud with a machine screw or welding, or using a pin having a special shape as the tapered pin used in the third step 3.

An embodiment in which the method of accessing the defective portions of various devices * shown in FIG. 1 for carrying out the steps 1 to 4 is applied to a nuclear reactor will be described with reference to FIG. FIG. 2 is a cross-sectional view of a boiling water reactor. 600
Is a reactor vessel, 610 is a reactor pressure vessel, 611 is a control rod, 612 is a recirculation feed pump, 613 is a primary system pipe,
Reference numeral 614 is a reactor core, and 615 is reactor water. Primary containment vessel 6
Above the 00 is a crane 620. Crane 620
Various devices 630 that can be remotely controlled are suspended, and various devices are arranged on the inner wall of the reactor water 615 of the reactor pressure vessel 610. The various devices 630 are arranged outside the reactor containment vessel 600 by a cable 621, and the control device 70
It is connected to 0 etc. and operates by remote control.

The defect portion 100 having the crack surface 101 on the inner surface of the shroud is repaired.

As the first step 1, the patch plate fixing device 631 which is hung from a crane 620 and which can be remotely operated is used, and a patch plate 200 made of Inconel steel is used to cover the crack as shown in FIG. Cover. The length of the caul plate is about 100 mm in the vertical direction, the lateral length is approximately 1.0 to 1.2 times the crack length, and the thickness is approximately 0.8 to 1.1 times the shroud thickness. About 5 times is appropriate. At this time, the patch plate is provided with a coating 201 made of a noble metal such as platinum or gold on the surface in contact with the defective part to take measures against the crevice corrosion environment between the patch plate and the defective part. Then the crane 620
Spot welder 63 that can be operated from the water
2, the patch plate 200 is temporarily fixed to the defective portion 100 by spot welding or the like.

In the second stage 2, two or more tapered holes are drilled from the contact plate toward the outer surface of the shroud by electric discharge machining by an electric discharge machine 633 which is suspended from the crane 620 and which can be operated in water. The tapered hole may have a circular or polygonal cross-sectional shape, and the hole may be through or non-through. Further, the taper angle of the tapered hole is preferably 5 ° to 40 ° with respect to the crack surface.

As a third stage 3, after the taper hole drilling process,
Using the pin fixing device 634 that is hung from the crane 620 and can be operated remotely, the Inconel tapered pins 300 that fit into the tapered holes are inserted from the contact plate 200 on the inner surface of the shroud by the number of the tapered holes. Even for this tapered pin, as a measure against crevice corrosion environment,
Apply precious metal coating in advance. By these operations, the patch plate and the defective portion are fastened.

In the fourth stage 4, the tapered pin 300 is fixed from the outer surface of the shroud in order to prevent the tapered pin 300 and the contact plate 200 from dropping into the reactor during plant operation. A first example of fixing the tapered pin 300 and the backing plate 200 to the inner surface of the shroud is shown below. After fastening the patch plate 200 and the defective portion 100, as shown in FIG.
As described above, the tapping is performed from the outer surface portion of the shroud to perform the female thread cutting work by using the female thread cutting device 635 which is hung from the crane 620 and which can be remotely operated. However, considering the complexity of the work, the finishing accuracy, etc., it is better to perform this female thread cutting work at the stage of bringing the tapered pin 301 into the reactor. After turning the female thread, using a remotely operable screw tightening device 636 suspended from the crane 620,
As shown in FIGS. 3 and 4, the tapered pin 300 and the contact plate 200 are fixed to the defective portion 100 by fitting a screw 400 adapted to the internal thread size from the outer surface of the shroud into the tapered portion. As a result, the tapered pin 301 and the contact plate 200 do not drop into the reactor.

An embodiment of a method for repairing defects existing on the inner surface of the shroud using the contact plate 202 having tapered pins will be described. As the pad plate 202 having the tapered pin, a pad plate 203 having tapered polygonal portions or convex portions as shown in FIG. 9 may be used.

A noble metal coating is previously applied to the contact plate 202 having the tapered pin as a countermeasure against the crevice corrosion environment. Method 1 of the present invention for repairing cracks when using a backing plate 202 having tapered pins
FIG. 1, which is a flowchart of No. 0, is a process from the second stage 2. In the second stage 2, the electric discharge machine 633, which is suspended from the crane 620 and can be operated even in water, faces the outer surface of the shroud from the patch plate by electric discharge machining.
1 having a tapered pin so as to sandwich 1
A plurality of tapers are processed so as to fit the tapered pin portions of. The processed holes may be through holes or non-through holes.

As the third stage 3, after the taper hole drilling,
Using a remotely operable patch plate fixing device 631 suspended from a crane 620, a patch plate 2 having a tapered pin
02 is inserted from the inner surface of the shroud. By these operations, the patch plate and the defective portion are fastened.

As the fourth stage 4, in order to prevent the backing plate 202 having tapered pins from falling into the reactor during plant operation, the backing plate 202 having tapered pins is used.
Is fixed from the outer surface of the shroud. A first embodiment of fixing a backing plate 202 having tapered pins to the inner surface of the shroud is shown below. After fastening the patch plate 202 having the tapered pin and the defective portion 100, as shown in FIG.
Female thread milling device 6 that can be remotely controlled from 0
Using No. 35, set up a tap from the outer surface of the shroud and perform the thread cutting work. However, considering the complexity of the work and the finishing accuracy, this female thread cutting work is performed with the tapered pin 3
It is better to do this at the stage of bringing 01 into the reactor. After cutting the internal thread, by using a screw tightening device 636 which is hung from the crane 620 and which can be operated remotely, by inserting a screw 400 suitable for the internal thread size from the outer surface of the shroud into the taper portion, as shown in FIGS. As described above, the pad plate 202 having the tapered pin can be fixed to the defective portion 100. As a result, the contact plate 20 having the tapered pin
2 does not fall into the reactor.

Tapered pin 300 and caul plate 200
Alternatively, the tapered pin 300 and the caul plate 200 or the caul plate 202 having a tapered pin for preventing the caul plate 202 having the tapered pin from falling out of the reactor.
A second embodiment for fixing the is shown below. This uses a pin fixing device 634 which is hung from a crane 620 and which can be remotely controlled, and the sum of the width of the pad plate and the width of the defective portion is about 1.
After fastening the backing plate 200 and the defective portion 100 with the tapered pin 302 having a length of about twice, using the pedestal fixing device 637 which is hung from the crane 620 from the outer surface of the shroud and which can be remotely operated Place the pedestal like the washer 500 on the head of the tapered pin,
The overlay welding 501 is performed on the head of the tapered pin by using the simple welding device 633 that can be remotely operated and can be operated in water, which is suspended from 20. As shown in FIG. 7, the tapered pin is fixed from the outer surface of the shroud, and it is possible to prevent the tapered pin 302 and the caul plate 200 from dropping into the reactor.

Next, the tapered pin 300 and the pad 2
00 or a third embodiment for fixing a backing plate 202 having tapered pins is shown below. This is a crane
A pin fixing device 634 hung from 620 that can be operated remotely.
After fastening the backing plate 200 and the defective portion 100 with the headed bifurcated pin 303, the crane 62
Using a remotely operable pin splitting device 638 hung from 0, the bifurcated head portion of the bifurcated headed pin 303 is bent and brought into close contact with the outer surface portion of the shroud. As shown in FIG. 6, the tapered pin 303 is fixed from the outer surface of the shroud,
It is possible to prevent the head-headed bifurcated tapered pin 303 and the backing plate 200 from falling out of the reactor.

[0026]

EFFECTS OF THE INVENTION According to the present invention, it is possible to provide a method for repairing the internal structure of a nuclear reactor which is highly safe against seismic loads accompanied by vertical shaking, and can extend the life of a nuclear power plant. To

[Brief description of drawings]

1 is a flow chart of a method according to the present invention.

FIG. 2 is an explanatory diagram showing a method of accessing defects in a furnace of various devices.

FIG. 3 is an explanatory view of repairing a defective portion using a tapered pin and a backing plate.

FIG. 4 is an explanatory view of fixing a tapered pin using a fixing screw.

FIG. 5 is an explanatory view of repairing a defective portion using a patch plate having a tapered pin portion.

FIG. 6 is an explanatory view of fixing a backing plate having a tapered pin portion using a fixing screw.

FIG. 7 is an explanatory view of a tapered pin fixed state using a washer and build-up welding.

FIG. 8 is an explanatory view of a tapered pin fixed state using a forked head pin.

FIG. 9 is a perspective view of a backing plate in which the tapered protrusion has a polygonal shape.

[Explanation of symbols]

100 ... Defect part, 101 ... Crack surface, 200 ... Patch plate,
201 ... Coating part, 300 ... Tapered pin.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Eisaku Hayashi 3-1-1, Saiwaicho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi factory

Claims (5)

[Claims] 1. A part of a reactor internal structure containing a defect is covered with a patch plate, and after temporarily fixing the patch plate to the part containing the defect, a tapered hole is formed in the part having the defect and the patch plate, Alternatively, by processing a tapered groove, by inserting a tapered pin that fits into the hole or the groove into the hole or the groove, and fixing the tapered pin,
A method for repairing defects in a nuclear reactor internal structure, comprising fixing and fastening a portion including the defective portion and the patch plate. 2. The tapered hole or the tapered groove is formed in a portion including the defect, and the tapered pin is formed so as to be fitted in the tapered hole or the groove. Inserting the patch plate into the tapered hole or groove and fixing the tapered pin of the patch plate to fix and fasten the part including the defect portion and the patch plate. Defect repair method. 3. The pin according to claim 1 or 2, wherein after fitting the defective portion and the backing plate, the tapered pin and the pin portion of the backing plate having the tapered pin from an outer surface portion of the defective portion. A method for repairing defects in a nuclear reactor internal structure, which comprises fixing the tapered pin and the backing plate by inserting a fixing screw into the. 4. The method according to claim 1, wherein after fitting the defective portion and the backing plate, the tapered pin and the pin head of the backing plate are covered with washers from the outer surface portion of the defective portion. A method for repairing defects in a nuclear reactor internal structure, wherein build-up welding is applied to a head of the tapered pin to fix the tapered pin and the backing plate. 5. The tapered head bifurcated pin according to claim 1 or 2, which has been preliminarily processed so that the pin head is bifurcated, and the head is fitted with the defective portion and the backing plate. A method of repairing defects in a reactor internal structure, in which a tapered pin and a backing plate are fixed by bending a forked portion of a forked pin.