JPH08122485A - Repairing method of shroud in nuclear reactor pressurized container - Google Patents

Abstract

PURPOSE: To prevent the progress of a crack on a shroud in a nuclear reactor pressurized container. CONSTITUTION: In a nuclear reactor pressurized container 1, a baffle plate 7 is provided on the outer circumferential face of the lower part of a shroud 2 supported by a shroud support 11. the baffle plate 7 and a shroud head bolt- fixing lug 3 provided on the outer circumferential face of the upper part of the shroud 2 are connected to each other with a reinforcing member 5. Thereby, it is possible to prevent the progress of a crack when the crack is generated on the shroud 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for repairing a shroud in a reactor pressure vessel installed in the reactor pressure vessel of a boiling water reactor.

[0002]

2. Description of the Related Art In a reactor pressure vessel of a boiling water reactor, a shroud is installed which holds a core support plate and an upper lattice plate and encloses the entire fuel assembly to form a core. A shroud head fixed by a shroud head bolt is provided on an upper portion of the shroud, and a steam separator is attached to the shroud head. This steam separator separates steam and water generated from the core.

A baffle plate called a pump deck for fixing the jet pump is attached to the lower outer surface of the shroud. The jet pump is arranged outside the core and forcedly circulates the coolant.

[0004]

Most of the reactor internals such as the shroud in the reactor pressure vessel are composed of welded stainless steel members. However, when the carbon content is high, the welded part or near the welded part is formed. Cracks may occur due to stress corrosion cracking.

In particular, the shroud holds the upper lattice plate and the core support plate inside, as described above, and the shroud itself is supported at the lower end by welding to the shroud support ring integrally formed with the reactor pressure vessel. Has been done. Therefore, it is extremely difficult to replace it, and even if it can be replaced, it is expected to be enormously expensive.

[0006] Reactor internal structures and equipment such as shrouds in a reactor pressure vessel that have been used for a long time are fragile due to neutron irradiation, and when welded, finer cracks may occur around the weld metal. Therefore, there is a problem that repairing by welding is difficult.

The present invention has been made to solve the above problems, and when defects such as cracks occur in the shroud in the reactor pressure vessel, the shroud head guarantees the same strength as the original structural material. (EN) An effective method for repairing a shroud in a reactor pressure vessel that does not impair the function of a bolt lug.

[0008]

According to the present invention, a baffle plate is attached to a lower outer surface of a shroud supported by a shroud support in a reactor pressure vessel, and the shroud attached to the baffle plate and the upper outer surface of the shroud. The head bolt fixing lug is connected by a reinforcing member.

[0009]

The reinforcing member connects between the shroud head bolt fixing lug for fixing the shroud head attached to the upper part of the shroud and the baffle plate.
As a result, it is possible to prevent the crack from proceeding when the shroud cracks, without impairing the fixing function of the shroud head bolt.

Further, by using a material having a coefficient of thermal expansion smaller than that of austenitic stainless steel for the material of the reinforcing member, a slight additional fastening load is required at the time of mounting the reinforcing member. It will be easy.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for repairing a shroud in a reactor pressure vessel according to the present invention will be described with reference to the drawings. 1 is a perspective view showing a part of the reactor pressure vessel in a vertical cross section by notching the inside of the reactor pressure vessel for explaining the method of the present invention, and FIG. 2 is an enlarged perspective view of part A of FIG. 2 is a perspective view showing another example of FIG. 2, FIG. 4 is an enlarged perspective view of a partial cross-sectional view for explaining a portion B of FIG. 1, and FIG. 5 is a partial cross-section of another example of FIG. 6 is a perspective view showing a part of the turnbuckle portion in FIG. 1 in a side view.

As shown in FIG. 1, a shroud 2 is installed in a reactor pressure vessel 1 while being supported by a shroud support ring 11. A baffle plate 7 is attached to the lower outer surface of the shroud 2, and a shroud head bolt fixing lug 3 is attached to the upper outer surface of the shroud 2. The baffle plate 7 and the shroud head bolt fixing lug 3 are connected and fixed by the reinforcing member 5 to repair the shroud 2 in the reactor pressure vessel 1.

This connecting and fixing method is as shown in FIG.
Form a hole 4 in the lug 3 for fixing the shroud head bolt,
A hole is also formed in the reinforcing member 5 at the same position as the hole 4. The reinforcing member 5 is pushed in from the outside of the lug 3 and a fixing component 6 such as a pin or a bolt is inserted through the hole and fixed in the hole 4 provided in the lug 3. By this fixing method, the reinforcing member 5 can be fixed by contact with the shroud head bolt fixing lug 3 without losing the fixing function of the shroud head bolt.

As a method of fixing the reinforcing member 5 to the baffle plate 7, screw holes 8 are formed in the baffle plate 7 and the reinforcing member 5 as shown in FIG. At the time of fixing, the leakage prevention component 9 is provided on the surface of the baffle plate 7 and the contact surface of the reinforcing member 5. This makes it possible to prevent leakage of the reactor cooling water from the pump deck, that is, the lower part of the baffle plate 7.

Further, a hole is formed in the baffle plate 7, a reinforcing member is inserted into this hole, and the tip claw of the reinforcing member 5 after the insertion.
10 is provided, and when the claw 10 is opened, it is fixed in contact with the lower surface of the baffle plate 7. In this case, the leakage prevention component is provided in the gap between the hole processing surface of the baffle plate and the reinforcing member.

Further, as shown in FIG. 1, a turnbuckle 10 is provided between the contact fixing portion of the lug 3 for fixing the shroud head bolt and the contact fixing portion of the baffle plate 7, and the turnbuckle 10 is installed in the reactor pressure vessel 1. Shroud 2
It is possible to reliably reinforce. It is also possible to provide the turnbuckle 10 above the contact fixing portion of the reinforcing member and the shroud head bolt fixing lug 3. At this time, the function of fixing the shroud head bolt of the contact fixing portion of the reinforcing member 5 is lost, but the shroud head is fixed by another shroud head bolt.

Further, as the material of the reinforcing member, a material having a coefficient of thermal expansion smaller than that of austenitic stainless steel which is a material of the shroud, for example, a corrosion resistant heat resistant superalloy (NCF material) is selected.

As a result, a difference in thermal expansion between the shroud, which is the member to be fastened, and the reinforcing member, which is the fastening member, occurs under the high-temperature and high-pressure operation that requires a great holding force, and the resulting reinforcing member is obtained. The axial force of the shaft effectively acts to hold the shroud. According to this method, the tightening load added when mounting the reinforcing member requires only a small load, so that the mounting work of the reinforcing member becomes easy.

FIG. 1 shows a state in which the shroud 2 is reinforced by connecting and fixing the shroud head bolt fixing lug 3 and the baffle plate 3 with a reinforcing member 5 having a turnbuckle 10.

FIG. 2 shows details of a state in which the lug 3 for fixing the shroud head bolt and the reinforcing member 5 are fixed in contact with each other by the fixing component 6. Since the fixing parts 6 are attached to each of the right and left sides of the shroud head bolt fixing lug 3, they do not interfere with the inserted shroud head bolt when the shroud head is installed, and thus the fastening function of the shroud head bolt is not lost. .

FIG. 3 shows details of a state in which the lug 3 for fixing the shroud head bolt and the reinforcing member 5 are contact-fixed by the fixing component 6 by another method. By this fixing method, the function of the turnbuckle 10 shown in FIG. 1 can be performed by the fixing component 6, so that the turnbuckle 10 can be deleted.

FIG. 4 shows details of the state where the reinforcing member 5 and the baffle plate 7 are fixed in contact with each other. A leak prevention component 9 is installed at the contact portion between the main reinforcing member 5 and the baffle plate 7 to prevent the reactor cooling leak. Further, the pawl 10 is securely inserted on the lower surface of the baffle plate 7 after being inserted into the pump deck, that is, the baffle plate 7.
The shape is asymmetrical so that it will be caught.

FIG. 5 shows details of a state in which the reinforcing member 5 and the baffle plate 7 are contact-fixed by another method. At the contact portion between the main reinforcing member 5 and the baffle plate 7, a leak prevention component is installed as in the method shown in FIG. 4 to prevent leakage of the reactor cooling water.

FIG. 6 shows details of the state in which the turnbuckle 10 is installed. The pair of upper and lower reinforcing members 5 are provided with screws 5
It is possible to adjust the reinforcing force of the shroud 2 by forming a and screwing it into the screw 10a formed on the turnbuckle 10 and rotating the turnbuckle 10 in the direction of the arrow shown in FIG.

[0025]

According to the present invention, when a defect such as a crack occurs in a shroud installed in a reactor pressure vessel of a boiling water type light water cooled reactor, a shroud head bolt lug and a baffle plate are reinforced by a reinforcing member. It is possible to provide an effective repairing method that guarantees strength equivalent to that of the original structural material and does not impair the function of the shroud head bolt by connecting and fixing.

In addition, since the reinforcing member can be connected and fixed to the baffle plate and the shroud head bolt fixing lug in water or by remote control, there is an effect that radiation exposure can be reduced during construction in the nuclear reactor.

[Brief description of drawings]

FIG. 1 is a perspective view showing a partial cross-section for explaining an embodiment of a method for repairing a shroud in a reactor pressure vessel according to the present invention.

FIG. 2 is an enlarged perspective view showing a portion A in FIG.

FIG. 3 is a perspective view showing another example in FIG.

FIG. 4 is a perspective view for explaining a method of inserting a B portion in FIG.

FIG. 5 is a perspective view for explaining another example in FIG.

FIG. 6 is a perspective view showing the turnbuckle portion in FIG.

[Explanation of symbols]

1 ... Reactor pressure vessel, 2 ... Shroud, 3 ... Shroud head bolt fixing lug, 4 ... Hole, 5 ... Reinforcing member, 6 ...
Fixed parts, 7 ... Baffle plate, 8 ... Screw holes, 9 ... Leakage prevention parts, 10 ... Turnbuckle, 11 ... Shroud support.

Claims (5)

[Claims] 1. A baffle plate is attached to a lower outer surface of a shroud supported by a shroud support in a reactor pressure vessel, and the baffle plate and the lug for fixing the shroud head bolt are connected by a reinforcing member. Repair method for shroud in reactor pressure vessel. 2. The method for repairing a shroud in a reactor pressure vessel according to claim 1, wherein a reinforcing member is contact-fixed to the baffle plate through a leakage prevention component. 3. The method for repairing a shroud in a reactor pressure vessel according to claim 1, wherein a reinforcing member is surrounded from the outer surface of the lug for the shroud head bolt and fixed by contact with a fixing component. 4. The method for repairing a shroud in a reactor pressure vessel according to claim 1, wherein the baffle plate and the lug for fixing the shroud head bolt are contact-fixed with a reinforcing member having a turnbuckle. 5. The method for repairing a shroud in a reactor pressure vessel according to claim 1, wherein the reinforcing member is made of a material having a coefficient of thermal expansion smaller than that of austenitic stainless steel.