JPH02210296A - Method and structure for repairing long-sized housing - Google Patents

Abstract

PURPOSE:To prevent reactor water from leaking from a defective part nearby the weld zone of the long-sized housing by inserting a repair sleeve into the long-sized housing so that the sleeve covers and blocking its defective occurrence part from inside, and fixing the sleeve. CONSTITUTION:For example, a neutron flux detector 15 is extracted from the neutron flux monitor housing 18 and the upper part of the weld zone of the housing 18 is sealed with a water plug. Then the housing 18 is expanded at the insertion position of the through hole 23 of a pressure container 10 and sealing and fixation are carried out. Then the inner peripheral surface of the periphery of the defect occurrence part 31 is bored and grinded. Then the thin repair sleeve 30 is inserted into the housing 18 and set covering the defective position 31 from inside, and the sleeve is expanded (about <=10% tube expansion rate) by an expander to contact the inner peripheral surface of the housing. Then, a sleeve welder performs arc seam welding 32 in the circumferential direction above and below the defective part 31 to fix the sleeve to the inner peripheral surface. Further, the upper and lower ends of the sleeve 30 are welded 33 for sealing to the entire circumference. Consequently, the reactor water is prevented from leaking and the defective part 31 can be isolated from the reactor water.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a repair method and a repair structure for a long housing such as a neutron flux monitor housing that is fixedly supported in a nuclear reactor vessel.

(Prior art) The output of a nuclear reactor such as a boiling water reactor is proportional to the neutron flux, so in order to display the reactor output and evaluate the burnup, the neutron flux of the reactor is measured using a neutron flux detector (neutron flux detector). It is measured and monitored using a bundle monitor.

A neutron flux detector 1 is installed in a boiling water nuclear reactor as schematically shown in FIG. There is a reactor core 3 inside the reactor pressure vessel 2.
is accommodated as shown by the broken line.

A neutron detector 1 is installed in this core 3. In the illustrated example, one neutron detector 1 is installed for the sake of simplicity.

The neutron flux monitor main body 4 of the neutron detector 1 is formed into an elongated shape, and its upper end is elastically supported by the lower support hole 5a of the upper grid plate 5 of the reactor core, and its lower part is connected to the neutron flux monitor guide tube. 6 and protrudes downward through the neutron flux monitor housing (in-core monitor housing) 7.1. Its lower end is a neutral neutron flux monitor flange (in-core flange)
8 and is fixed by a tightening nut 9 for installation.

The upper part of the neutron flux monitor housing 7 is the reactor pressure vessel 2
It is fixed by welding to the lower mirror welding part and is placed in a hanging state. Since the neutron flux monitor housing 7 uses an austenitic stainless steel tube such as 5LIS304,
If the three conditions of stress, corrosive environment, and material (creation of a chromium-deficient layer) are satisfied, stress corrosion cracking (hereinafter referred to as SCC) may occur near the weld to the reactor pressure vessel 2. Stress corrosion cracking will not occur if even one of the three conditions is missing, so to prevent stress corrosion cracking,
Various measures are being taken.

(Problems to be Solved by the Invention) For example, intergranular stress corrosion cracking (IGS) occurs near the welded part of the reactor pressure vessel 2 that fixedly supports the neutron flux monitor housing 7.
CC) occurs, or a welding defect occurs due to poor fusion during welding, or a crack occurs in the neutron flux monitor housing near the weld due to a defect in the neutron flux monitor housing itself, and this crack is a housing penetrating defect. If this progresses, there is a risk that it will develop into a reactor water leak.

On the other hand, the neutron flux detector that measures and monitors the neutron flux in the reactor core measures the reactor's output l! Unlike the υ control rod drive mechanism that shuts down reactor operation, the seal support structure of the neutron flux monitor housing is not intended for the reactor safety system, as it does not belong to the reactor safety system. In the event that a penetration defect occurs in the neutron flux monitor housing itself near the weld to the pressure vessel, no permanent repair method or seal support structure has been established to prevent reactor water leakage.

The present invention has been made in consideration of the above-mentioned circumstances, and is capable of reliably and quickly preventing leakage of reactor water from defective parts near the welds of elongated housings such as neutron flux monitor housings.
It is an object of the present invention to provide a permanent method for repairing a long housing and a structure for repairing the same, which can also suppress the growth of defective parts.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above-mentioned problems, a method for repairing a long housing according to the present invention provides a method for repairing a neutron flux monitor housing, etc. fixed to a welded part of a reactor vessel. In this method, a repair sleeve is inserted into the elongated housing, the inserted repair sleeve covers and closes the defective part of the elongated housing from the inside, and the repair sleeve is fixed to the elongated housing at this closed position.

In addition, in order to solve the above-mentioned problems, the long housing repair method according to the present invention is a method for repairing a long housing such as a neutron flux monitor housing fixed to the lower mirror welding part of the reactor vessel. While the hole is expanded and sealed at the insertion position, a repair sleeve is inserted into the long housing, and the inserted repair sleeve covers and closes the defective part of the long housing from the inside, and the closed position In this method, the repair sleeve is fixed to the elongated housing.

Furthermore, in order to solve the above-mentioned problem, the elongated housing repair structure according to the present invention repairs the defective part of the elongated housing such as the neutron flux monitor housing fixed to the welded part of the reactor vessel. A repair sleeve is inserted so as to close it from the inside, and the repair sleeve is fixed to the elongated housing at the closed position.

Furthermore, in order to solve the above-mentioned problems, the repair structure for a long housing according to the present invention provides a long housing such as a neutron flux monitor housing that passes through the through hole of the reactor vessel and is fixed to the welded portion of the lower mirror. The long housing is expanded and sealed at the through-hole insertion position, and a repair sleeve is inserted into the long housing so as to close the defective part of the housing from the inside, and the repair sleeve is inserted into the long housing at the closed position. It is fixed to the housing.

(Function) The repair method and structure of this long housing are as follows:
If a penetrating defect occurs in the elongated housing itself, such as the neutron flux monitor housing, during operation of the nuclear reactor, the defect location is sealed from the inside with a repair sleeve inserted into the elongated housing. By fixing the repair sleeve to the elongated housing at the closed position, leakage of reactor water from the defective position of the elongated housing can be reliably and quickly prevented, and the progress of the defective part can also be suppressed by isolating it from the reactor water environment.

In addition, when a long housing inserted into a through-hole in a reactor vessel is expanded at the insertion position and sealed and fixed in the through-hole, the long housing and the repair sleeve inserted into the through-hole are double-sided. It can have a sealing structure, reliably prevent reactor water leaks, and provide permanent sealing measures.

(Example) Hereinafter, an example of the present invention will be described with reference to the accompanying drawings.

As shown in FIG. 2, a boiling water reactor is equipped with a reactor pressure vessel 10 as a reactor vessel.
0 is supported on its support pedestal 11 via a support skirt 12. At the lower part (lower mirror) of the reactor pressure vessel 10, a large number of control rod drive mechanisms (CRD) 13 are installed vertically in a stand-alone manner for moving control rods (not shown) in and out of the reactor core. CRD housing 14 of control rod drive mechanism 13
is fixed to the lower mirror of the reactor pressure vessel 10 by welding. This CRD housing (long housing) 14 has 5US
Stainless steel such as 304.5 US 3041 is used.

Further, in order to display the output of the nuclear reactor and evaluate the burnup, the neutron flux generated in the core of the nuclear reactor is measured and monitored by the neutron flux detector 15. The neutron flux detector 15 is connected to each CHD.
As shown in FIG. 3, the main body 16 of the neutron flux monitor has an elongated shape and is disposed in an appropriate space between the monitors 13 and 13.

The neutron flux monitor main body 16 has a V8 long tubular shape, and the lower side thereof has a neutron flux 72 guide tube 17 which is a long housing.
It extends downward through the neutron flux monitor housing (in-core monitor housing) 18, and its lower end portion is abutted and supported by the inner peripheral shoulder portion of the neutron flux monitor 7 flange 19.

This neutron flux monitor flange 19 is attached to the lower end outer circumference 7 flange 18a of the neutron flux monitor housing 18 with a tightening bolt 20.
Fixed by The neutron flux monitor main body 16 supported by the neutron flux monitor flange 19 is an in-core nut (
An installation tightening nut may also be used. )21.

On the other hand, the neutron flux monitor housing 18 into which the neutron flux monitor main body 16 is inserted is 5LIS304.5LIS304.
As shown in FIG. 4, the upper part of the neutron flux monitor housing 18 is passed through the through hole 23 of the reactor pressure vessel 10 whose base material is carbon steel. It is fixed by welding from the inside of the furnace pressure vessel 10.

Specifically, a stainless steel overlay 24 is formed by welding on the inside of the reactor pressure vessel 10, and is mirror-finished. The inclined side of the through hole portion 23 is beveled and welded with Inconel 182 or the like to form the nozzle stub 25. A groove is formed at the top of this nozzle stub 25, and this groove is welded with Inconel 82, Inconel 182 containing Nb, etc., and the neutron flux monitor housing (long housing ) 18 is fixed to the nozzle stand 25 and sealed.

The welded portion 26 of the nozzle stub 25 separates the inside of the reactor pressure vessel 10 from the lower pressure boundary 27 and isolates it from the reactor water environment.

On the other hand, the neutron flux monitor housing 18 and CRD housing 14, which are long housings, are made of stainless steel (StJS
If the three conditions for stress corrosion cracking are satisfied, stress corrosion cracking may occur at the welded portion with the reactor pressure vessel 10. This stress corrosion cracking (SC)
C) occurs, a penetrating defect occurs in the long housing due to a defect in the housing itself, a crack occurs due to a welding defect due to poor fusion during welding, and if this crack grows and becomes larger, it may damage the reactor pressure vessel. There is a risk that the reactor water in the reactor 10 may leak out of the reactor pressure vessel through the penetrating defect occurring portion of the elongated housing.

This reactor water leak is monitored by various detectors, and is also inspected and detected during periodic inspections. When a reactor water leak is detected, leak prevention measures are taken, and the defective part is repaired using the following repair method, and reactor water leaks are reliably and permanently prevented.

FIGS. 1A to 1D show an example of a method for repairing a neutron flux monitor housing and a structure for repairing the same.

When performing this repair method, the neutron detector 15 is pulled upward from the neutron flux monitor housing 18 and removed, while the neutron flux monitor guide tube 17 may be placed above the welded portion of the neutron flux monitor housing 18. ) with a water faucet such as a bore plug.

Next, the neutron flux monitor housing 18 is expanded at a position where the through hole 23 of the reactor pressure vessel is inserted, as shown in FIG. Crimp and secure the seal. The expanded state of the neutron flux monitor housing 18 is measured by a dimension measuring machine (not shown). After the tube expansion operation of the neutron flux monitor housing 18 (or before the tube expansion operation is started).

), a non-destructive testing device such as an ultrasonic flaw detection device (UT device) is inserted from below the housing to investigate and identify the location where the penetrating defect occurs.

After the tube expansion work of the neutron flux monitor housing 18 is completed, the inner circumferential surface around the defective area is polished in a predetermined axial direction using a remote-controlled housing inner surface processing machine or a housing inner surface finishing machine (both not shown) as necessary. Pauling is performed over the length, and the inner surface is ground as shown in FIG. 1(B).

After the inner surface of the neutron flux monitor housing 18 is finished, the thin repair sleeve 30 is inserted into the neutron flux monitor housing 18 as an inner coating sleeve. The inserted repair sleeve 30 is set so as to cover the housing defect part @31 from the inside. The repair sleeve 30 has S
Stainless steel such as 5t JS316L with CC countermeasures is used, and the repair sleeve 30 has a wall thickness smaller than the inner diameter of the neutron flux monitor housing 18 and has a wall thickness of, for example, about 2 shoes, enough to withstand the pressure inside the reactor during reactor operation. has.

The repair sleeve 30 inserted so as to cover the defective position 31 of the neutron flux monitor housing 18 is expanded by cold working etc. using an expander as shown in FIG. be done. The expansion ratio of the repair sleeve 30 is suppressed to such an extent that residual stress does not remain, for example, within about 10%, taking SCC countermeasures into consideration. The expanded repair sleeve 30 has an inner diameter into which the neutron flux monitor main body 16 of the neutron detector 15 (for example, outer diameter 34.1 mm) is inserted.

The tube is expanded at a position covering the defective part 31 of the neutron flux monitor housing 18, and the W! The applied repair sleeve 30 is then arc seam welded (TI) in the circumferential direction at positions above and below the defect occurrence area using a sleeve welding machine.
(G fusion welding) 32, and is fixed to the inner circumferential surface of the housing as shown in FIG. 1(D). The repair sleeve 30 fixed in the neutron flux monitor housing 18 is further sealed by welding 33 at the upper and lower ends of the sleeve over the entire circumference.
The gap between the repair sleeve 30 and the neutron flux monitor housing 18 is isolated from reactor water to eliminate a corrosive environment.

Thereby, leakage of reactor water is prevented, and furthermore, the defective portion of the neutron flux monitor housing 18 can be isolated from the water, and further development of the defect can be effectively prevented. FIG. 1(D) shows a repair structure for a long housing that takes measures against reactor water.

After the repair sleeve 30 is fixed at a predetermined position within the neutron flux monitor housing 18, the inner diameter of the sleeve is measured by a dimension measuring machine, while a penetrant inspection machine (not shown) is used.
The soundness of the repair sleeve 30 is confirmed by the PT device), and the repair work of the neutron flux monitor housing 18 is completed.

When carrying out the M repair work on the neutron flux monitor housing 18, the following points should be considered as measures against leakage of reactor water.

■It must be a repair method that can be applied to the pressure-resistant boundary of the reactor pressure vessel 10.

■Remove the defect indicator of the neutron flux monitor housing or prevent the defect from progressing.

■Prevent leakage from around housing defects.

■Do not worsen the properties of the sensitized area of the housing defect (neutron flux monitor housing attachment weld).

■It must not conform to technical standards.

Considering these points, the neutron flux monitor housing 18
Repair work will be carried out.

After this repair work is completed, the faucet is removed, and the neutron flux monitor main body 16 is guided into the neutron flux monitor housing 18, and is supported and fixed by the neutron flux monitor housing 18.

In this case, the neutron flux monitor housing 18 is prevented from leaking reactor water by the repair sleeve 30, while the neutron flux monitor housing 18 is expanded and sealed at the insertion position corresponding to the reactor pressure vessel through hole 23. , a double seal structure can be adopted, and reactor water leakage can be reliably and effectively prevented.

Next, the fifth section describes the tube expansion method of the neutron flux monitor housing 18 carried out in the long housing repair method.
This will be explained more specifically with reference to FIGS. (A) and (B).

The tube expansion of the neutron flux monitor housing 18 is carried out in stages using a housing tube expander.
), the upper housing 34a is expanded, and then the lower housing 34b is expanded, as shown in FIG. 5(B). In this case, by expanding the tube of the neutron flux monitor housing 18, the housing 18 can be crimped to the lower mirror through hole of the reactor pressure vessel 10, and a seal can be secured. 23
A labyrinth groove (not shown) may be bored in advance.

The feature of this tube expansion method for the neutron flux monitor housing 18 is that even if cracks occur not only in the housing, but also in the welded part 26 between the housing 18 and the nozzle stub 25, or the nozzle stub 25 itself, the cracks will cause the reactor water to flow into the reactor. It is possible to prevent leakage to the outside of the pressure vessel 10, providing a highly versatile reactor water leak prevention measure.

Further, the repair method of inserting and fixing the repair sleeve into the neutron flux monitor housing 18 may be carried out by the procedure shown in FIGS. 6(A) to 6(C).

This repair method omits the housing tube expansion step of expanding the neutron flux monitor housing 18 and tightly fixing it under the reactor pressure vessel 10 by Mmm.

In other repair procedures, the process shown in Figure 1 (A) is simply omitted, and Figure 6<A) or 'C) is shown in Figure 1 (B).
) to D), respectively, so the same reference numerals are given and the explanation will be omitted.

In the method for repairing a long housing shown in FIGS. 6(A) to 6(C), the method for repairing a long housing is as follows:
Repair sleeve 3 thick enough to withstand reactor pressure during reactor operation
0 is inserted, and the repair sleeve 30 is expanded from the inside so as to close the housing defect 31, and is brought into close contact with the inner circumferential surface of the neutron flux monitor housing 18, thereby blocking the housing defect 31 and, due to this blockage, removing the reactor water environment. It is designed to be isolated. Furthermore, by fixing the upper and lower parts of the repair sleeve 30 to the neutron flux monitor housing 18 by arc seam welding 32, the defective part can be isolated from the reactor water environment, and the progress of the defect can be prevented.

Next, another embodiment of a method for repairing a long housing will be described with reference to FIGS. 7(A) to 7(C).

The repair method for a long housing shown in this embodiment is a repair method in which a repair sleeve 35 is attached to the inside of the neutron flux monitor housing 18 using a surplus solder 36.

°When performing this repair method, the neutron detector 15 is removed upward from the neutron flux monitor housing 18, and the upper part of the housing is sealed off with a water faucet such as a bore plug. The area around the penetrating defect in the neutron flux monitor housing 19 is polled, and the inner surface is finished as shown in FIG.

Thereafter, the thin-walled repair sleeve 35 is inserted into the neutron flux monitor housing 18. Gold solder 36 is applied as a brazing material to the upper and lower ends of the repair sleeve 35 in the circumferential direction. Instead of applying this gold solder 36 to the repair sleeve 35, it may be applied in advance above and below the penetrating defect whose inner surface has been finished by poling.

Thus, the repair sleeve 35 inserted into the neutron flux monitor housing 18 is positioned at a position that closes the defective part of the housing from the inside, and after this positioning, the repair sleeve 35 is moved by the expander as shown in FIG. 7(B). The tube is expanded and crimped onto the inner circumferential surface of the neutron flux monitor housing 18 so as to be brought into close contact. At this time, the expansion ratio of the repair sleeve 35 is within about 10%, which is such that no residual stress remains in the sleeve 7. Expanded repair sleeve 35
The expanded state of the tube is measured using a sleeve dimension measuring machine.

The repair sleeve 35 expanded within the neutron flux monitor housing 18 is then heated by a heating coil 37 to melt the solder metal 36 as shown in FIG. 7(C). The repair sleeve 35 is fixed to the neutron flux monitor housing 18 by melting the gold solder 36. After this fixation, the heating coil 37 is removed from the repair sleeve 35 to construct a repair structure for the elongated housing, and the repair work is completed.

In this case, since the gold solder 36 is a chemically and physically stable substance, no adverse effects will occur, but by heating the repair sleeve 35, the neutron flux monitor housing 1
8, it is necessary to fully consider the sensitization of the material due to heating. As described above, since a heating action is required to attach the repair sleeve 35, the sleeve length of the repair sleeve 35 is longer than that of the repair sleeve 30 shown in FIG.

FIGS. 8(A) to 8(C) show still another embodiment of a method for repairing a long housing.

In the repair method shown in this embodiment, a repair sleeve 30 inserted into the neutron flux monitor housing 18 is fixed to the inner peripheral surface of the housing using a remote laser welding machine.

Among these repair methods, those shown in FIGS. 8(A) and (B) are the same as the repair methods shown in FIGS. 7(A) and (B), so the explanation thereof will be omitted.

On the other hand, as shown in FIG. 8(C) using a remote rape welder, the repair sleeve 3o is welded inside the neutron flux monitor housing 18. is confirmed and checked, and the repair work is completed. FIG. 8(C) shows a repair structure for a long housing.

In this case as well, the same effects as shown in FIG. 6 can be achieved.

In addition, in one embodiment of the present invention, the repair method and the repair structure of the neutron flux monitor housing have been explained.
The same can be applied to the case of RD housing. Furthermore, the present invention can also be applied to piping provided in the primary and secondary coolant partitions of a steam generator of a pressurized water reactor (DWR).

In addition, the support structure for long housings such as neutron flux monitor housings is such that from the beginning of reactor construction, the long housings are crimped and supported at the penetration part of the reactor vessel by expanding pipes, and are supported at welded parts and have a double seal structure. It may be supported by

[Effects of the Invention] As described above, in the method for repairing a long housing such as a neutron flux monitor housing and its repair structure according to the present invention, the long housing itself such as a neutron flux monitor housing can be damaged during operation of a nuclear reactor. Even if a penetrating defect occurs in the long housing, the defect location can be closed from the inside with a repair sleeve inserted into the long housing, and the repair sleeve can be fixed to the long housing at this closed position. Reactor water leakage from defective positions in the housing can be reliably and quickly prevented, and the growth of the defective parts can also be suppressed.

Furthermore, reliable repair can be performed with simple repair work in a relatively short time, reducing radiation exposure and improving reliability.

In addition, when the long housing inserted into the through hole of the reactor vessel is expanded at the insertion position and sealed and fixed to the T1 through hole, the long housing and the repair sleeve inserted therein will double up. It can have a sealing structure, reliably prevent reactor water leaks, and provide permanent sealing measures.

[Brief explanation of the drawing]

FIG. 1 (A> to D) is a diagram showing an embodiment of a long housing repair method and its repair structure according to the present invention;
Figure 2 is a diagram showing the lower structure of a boiling water reactor, Figure 3 is a diagram showing a neutron flux detector fixedly supported on the reactor pressure vessel in Figure 2, and Figure 4 is a diagram showing the neutron flux detector mentioned above. Figures 5 (A) and (B) are an example of the housing tube expansion process used in the repair method for the elongated housing shown in Figure 1. Figures 6(A) to C) are diagrams showing other embodiments of the long housing repair method and its repair structure according to the present invention, and Figures 7(A) to C) and Figures 8 (A) to C) are views showing still other embodiments of the present invention, and Figure 9 is a view schematically showing an installation example of a neutron flux detector installed in a conventional boiling water reactor. It is. 3... Reactor core, 5... Upper grid plate, 10... Reactor pressure vessel, 13... tlJ 11 rod drive mechanism, 14...
...CRD housing, 15...Neutron flux detector, 1
6... Neutron flux monitor main body, 17... Neutron flux monitor guide tube, 18... Neutron flux monitor housing, 23
...Through hole, 25...Nozzle holder (welded part), 26...
Welded part, 30. 35... Repair sleeve, 31... Defect part, 32... Arm seam welding, 33... Seal welding, 36... Gold solder, 37... Heating coil. Applicant's agent Hisashi Hatano 2J (A) Figure 5 (B)

Claims (1)

[Claims] 1. Inserting a repair sleeve into a long housing such as a neutron flux monitor housing fixed to a welded part of a reactor vessel,
A method for repairing an elongated housing, comprising: closing a defective part of the elongated housing so as to cover it from the inside with the inserted repair sleeve, and fixing the repair sleeve to the elongated housing at this closed position. 2. The elongated housing according to claim 1, wherein the repair sleeve is expanded at a closed position to cover the defect occurrence site of the elongated housing from the inside, and the repair sleeve is brought into close contact with the inner surface of the elongated housing, and the adhered repair sleeve is fixed by arc seam welding. How to repair. 3. A long housing such as a neutron flux monitor housing fixed to the lower mirror welding part of the reactor vessel is expanded into the through hole of the reactor vessel at the insertion position and sealed and fixed, while the long housing is fixed inside the long housing. A long housing characterized in that a repair sleeve is inserted, the inserted repair sleeve covers and closes a defect occurring part of the elongated housing from the inside, and the repair sleeve is fixed to the elongated housing in this closed position. Repair method. 4. Insert the repair sleeve into a long housing such as a neutron flux monitor housing fixed to the welded part of the reactor vessel so as to close the defective part of the housing from the inside, and insert the repair sleeve into the long housing at the closed position. A repair structure for a long housing, which is characterized by being firmly fixed to the housing. 5. The repair structure for an elongated housing according to claim 4, wherein the repair sleeve inserted into the elongated housing is expanded at a closed position of the defective housing portion and tightly adhered to the inner surface of the elongated housing. 6. A long housing such as a neutron flux monitor housing that passes through the through hole of the reactor vessel and is fixed to the welded portion of the lower mirror is expanded at the through hole insertion position and fixed with a seal, while the long housing A repair structure for a long housing, characterized in that a repair sleeve is inserted so as to close the defective part of the housing from the inside, and the repair sleeve is fixed to the long housing at the closed position.