JP2519316B2 - Repair method for long housing and repair structure - Google Patents

Description

The present invention relates to a method for repairing a long housing such as a neutron flux monitor housing fixedly supported by a reactor vessel, and a repair structure therefor.

(Prior art) Since the output of a nuclear reactor such as a boiling water reactor is proportional to the neutron flux, the neutron flux of the reactor (neutron flux) is used to display the reactor output and evaluate burnup. Monitor) to measure and monitor.

The neutron flux detector 1 is installed in a boiling water reactor as shown schematically in FIG. A reactor core 3 is housed in the reactor pressure vessel 2 as indicated by a broken line. The neutron detector 1 is installed in this core 3. In the illustrated example, 1 is used for simplicity.
The example which installed the neutron detector 1 of a book is shown.

The neutron flux monitor main body 3 of the neutron detector 1 is formed in a long and slender shape, the upper end thereof is elastically supported by the lower surface support hole 5a of the upper lattice plate 5 of the reactor core, and the lower part thereof is the neutron flux monitor guide tube 6 Also, it projects downward through a neutron flux monitor housing (incore monitor housing) 7, the lower end of which is supported in contact with a neutron flux monitor flange (incore flange) 8 and is fixed by a tightening nut 9 for installation.

The upper part of the neutron flux monitor housing 7 is fixed to the lower mirror welded portion of the reactor pressure vessel 2 by welding, and is provided in a suspended state. Since the neutron flux monitor housing 7 uses an austenitic stainless steel tube such as SUS304, stress,
When the three conditions of the corrosive environment and the material (generation of chromium deficient layer) are satisfied, stress corrosion cracking (hereinafter referred to as SCC) may occur near the welded portion with the reactor pressure vessel 2. Since stress corrosion cracking does not occur if even one of the three conditions is missing, various measures have been taken to prevent this stress corrosion cracking.

(Problems to be Solved by the Invention) For example, intergranular stress corrosion cracking (IGSC) near the welded portion of the reactor pressure vessel 2 that supports and fixes the neutron flux monitor housing 7.
C) occurs, or a welding defect occurs due to poor fusion during welding, or a defect in the neutron flux monitor housing itself causes a crack in the neutron flux monitor housing near the weld, and this crack is a housing penetration defect. 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 core is different from the control rod drive mechanism that controls the reactor power output or shuts down the reactor, because it does not belong to the safety system of the reactor.
The seal support structure of the neutron flux monitor housing is not premised on the safety system of the reactor, and if a penetration defect of the neutron flux monitor housing itself occurs near the weld with the reactor pressure vessel, the reactor A permanent repair method and seal support structure for water leakage have not been established.

The present invention has been made in consideration of the above-mentioned circumstances, and it is possible to reliably and quickly prevent reactor water leakage from a defective portion near a welded portion of a long housing such as a neutron flux monitor housing, and suppress the progress of the defective portion. An object of the present invention is to provide a permanent long housing repair method and a repair structure therefor.

[Structure of Invention]

(Means for Solving the Problems) A method for repairing a long housing according to the present invention is, in order to solve the above-mentioned problems, a long housing such as a neutron flux monitor housing fixed to a welded portion of a reactor vessel. Insert the repair sleeve, close the defect occurrence part of the long housing from the inside with the inserted repair sleeve, expand the repair sleeve at this closed position to make it adhere to the inner surface of the long housing, and make a close contact. This is a method of fixing the sleeve to the long housing by welding.

Further, in order to solve the above-mentioned problems, a method of repairing a long housing according to the present invention is a long housing such as a neutron flux monitor housing fixed to a lower mirror welded portion of a reactor vessel, which penetrates the reactor vessel. While expanding the pipe into the hole at the insertion position and sealingly fixing it, a repair sleeve is inserted into the elongated housing, and the defective sleeve of the elongated housing is covered with the inserted repair sleeve from the inside to close the defect position. Is a method of fixing the repair sleeve to the long housing.

Furthermore, the repair structure for the long housing according to the present invention is
In order to solve the above-mentioned problem, a long housing such as a neutron flux monitor housing fixed to the welded part of the reactor vessel is inserted with a repair sleeve so as to close the housing defect occurrence part from the inside, and the housing defect occurrence part In this closed position, the repair sleeve is expanded and brought into close contact with the inner surface of the long housing to fix the repair sleeve to the long housing.

Furthermore, in order to solve the above-mentioned problems, the repair structure of the long housing according to the present invention passes through the through hole of the reactor vessel, and has a long length such as a neutron flux monitor housing fixed to the lower mirror welded portion. The length housing is expanded at the position where the through hole is inserted to fix the seal, and a repair sleeve is inserted into the long housing so as to block the housing defect occurrence part from the inside, and the length of the repair sleeve is lengthened at the closed position. It is fixed to the housing.

(Operation) This repair method for a long housing and its repair structure are designed so that when a penetrating defect occurs in the long housing itself such as the neutron flux monitor housing during the operation of the reactor, this defect occurrence position is The repair sleeve inserted inside the length housing closes it from the inside, expands the repair sleeve at this closed position and makes it adhere to the inner surface of the long housing, and the adhered repair sleeve is fixed to the long housing by welding. Reactor water leakage from the defective position of the shaku housing can be reliably and quickly prevented, and the development of defective portions can be suppressed by separating from the reactor water environment.

Further, when the long housing that is inserted into the through hole of the reactor vessel is expanded at the insertion position and seal-fixed to the through hole, the long housing may have a double seal structure together with the repair sleeve to be inserted. As a result, reactor water leaks can be reliably prevented, and permanent sealing measures can be taken.

Embodiment An embodiment of the present invention will be described below with reference to the accompanying drawings.

The boiling water reactor is equipped with a reactor pressure vessel 10 as a reactor vessel as shown in FIG.
Is supported on its support pedestal 11 via a support skirt 12. A number of control rod drive mechanisms (CRD) 13 for vertically moving control rods (not shown) in and out of the reactor core are vertically installed under the reactor pressure vessel 10 (lower mirror). The CRD housing 14 of the control rod drive mechanism 13 is the reactor pressure vessel 10
It is fixed to the lower mirror by welding. The CRD housing (long housing) 14 is made of stainless steel such as SUS304 and SUS304L.

Further, the neutron flux generated in the core of the reactor is measured and monitored by the neutron flux detector 15 in order to display the output of the reactor and evaluate the burnup. The neutron flux detector 15 is disposed in an appropriate space between the CRDs 13 and has an elongated neutron flux monitor main body 16 as shown in FIG.

The neutron flux monitor main body 16 has an elongated tubular shape, and the lower side of the neutron flux monitor guide tube 17 is a long housing and the neutron flux monitor housing (in-core monitor housing).
It extends downward through 18 and its lower end is abutted against and supported by the inner peripheral shoulder of the neutron flux monitor flange 19. The neutron flux monitor flange 19 is fixed to the lower end outer peripheral flange 18a of the neutron flux monitor housing 18 with a tightening bolt 20. The neutron flux monitor body 16 supported by the neutron flux monitor flange 19 is fixed by an in-core nut (which may be an installation tightening nut) 21.

On the other hand, the neutron flux monitor housing 18 in which the neutron flux monitor main body 16 is inserted is made of stainless steel such as SUS304, SUS304L, SUS316L.
As shown in FIG. 4, the upper part of the reactor is passed through the through hole 23 of the reactor pressure vessel 10 using carbon steel as a base material to
It is fixed by welding from the inside.

Specifically, the stainless steel build-up portion 24 is formed by welding on the inside of the reactor pressure vessel 10 and is mirror-finished. A groove is formed on the inclined side of the through hole 23 and welded with Inconel 182 or the like to form a nozzle 25. A groove is formed on the top of this nozzle 25, and this groove is welded with Inconel 82 or Inconel 182 containing Nb (niobium), and the neutron flux monitor housing (long housing ) 18 is fixed to the nozzle 25 and sealed. The welded portion 26 of the nozzle 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, since the neutron flux monitor housing 18 and the CRD housing 14 which are long housings are made of stainless steel (SUS steel), if the three conditions of stress corrosion cracking are satisfied,
There is a possibility that stress corrosion cracking may occur at the welded portion with the reactor pressure vessel 10. This stress corrosion cracking (SCC) occurs, a defect in the housing itself causes a penetrating defect in the long housing, and a crack occurs due to a welding defect caused by poor fusion during welding. In that case, the reactor water in the reactor pressure vessel 10 may leak to the outside of the reactor pressure vessel through the penetrating defect generation portion of the long housing.

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

FIGS. 1 (A) to 1 (D) show an example of a method of repairing a neutron flux monitor housing and its repair structure.

When performing this repair method, the neutron flux detector 15 is pulled out upward from the neutron flux monitor housing 18 and removed, while the upper portion of the welded portion of the neutron flux monitor housing 18 (the neutron flux monitor guide tube 17 may be used). Seal with a water tap.

Next, the neutron flux monitor housing 18 is expanded at the insertion position of the through hole 23 of the reactor pressure vessel by a remote operation with a housing expander (not shown) as shown in FIG.
Crim the inner wall surface of 23 and fix the seal. The expanded state of the neutron flux monitor housing 18 is measured by a size measuring machine (not shown). This neutron flux monitor housing
After the tube expanding work of 18 (before the pipe expanding work may be started), a non-destructive inspection device such as an ultrasonic flaw detector (UT device) is inserted from below the housing to check the penetrating defect occurrence position.
Identify.

After the tube expansion work of the neutron flux monitor housing 18 is completed, by using a housing inner surface processing machine and a housing inner surface finishing machine (both not shown) by remote control, the inner peripheral surface around the defect occurrence part can be moved in a predetermined axial direction. Boring is performed over the length, and the inner surface is ground as shown in FIG. 1 (B).

After the inner surface processing of the neutron flux monitor housing 18 is completed, the thin repair sleeve 30 is inserted into the neutron flux monitor housing 18 as an inner surface covering sleeve. The inserted repair sleeve 30 is set so as to cover the housing defect position 31 from the inside. The repair sleeve 30 is made of stainless steel such as SUS316L that has been subjected to SCC measures.This repair sleeve 30 is smaller than the inner diameter of the neutron flux monitor housing 18, and has a wall thickness that can withstand the internal pressure of the reactor during operation, For example, it has about 2 mm.

The repair sleeve 30 inserted so as to cover the defect position 31 of the neutron flux monitor housing 18 is expanded by an expander device by cold working or the like as shown in FIG. 1 (C), and is closely attached to the inner peripheral surface of the housing. To be done. The expansion ratio of the repair sleeve 30 is suppressed to a level where residual stress does not remain, for example, within about 10% in consideration of SCC measures. The expanded repair sleeve 30 has an inner diameter through which the neutron flux monitor body 16 (for example, outer diameter 34.1 mmφ) of the neutron detector 15 is inserted.

A repair sleeve expanded at a position covering the defective portion 31 of the neutron flux monitor housing 18 and closely attached to the inner peripheral surface of the housing.
30 is then subjected to arc seam welding (TIG fusion welding) 32 in the circumferential direction above and below the defect occurrence portion by a sleeve welder 32, and as shown in FIG.
It is fixed as shown in. Neutron flux monitor housing 18
The repair sleeve 30 fixed inside is further seal-welded 33 around the upper and lower ends of the sleeve to isolate the gap between the repair sleeve 30 and the neutron flux monitor housing 18 from the reactor water and remove the corrosive environment.

As a result, leakage of reactor water can be prevented, and the defective portion of the neutron flux monitor housing 18 can be isolated from the reactor water, and new development of defects can be effectively prevented. FIG. 1 (D) shows a repair structure for a long housing provided with measures against reactor water leaks.

After the repair sleeve 30 is fixed at a predetermined position in the neutron flux monitor housing 18, the inner diameter of the sleeve is measured by a dimension measuring device, while the penetrant flaw detector (PT
Device) confirms the integrity of the repair sleeve 30,
The repair work of the neutron flux monitor housing 18 is completed.

When repairing the neutron flux monitor housing 18, the following points are considered as measures against reactor water leakage.

A repair method applicable to the pressure boundary of the reactor pressure vessel 10.

Remove the defect indicator in the neutron flux monitor housing or prevent the development of defects.

 Prevent leakage from around the defective part of the housing.

Do not deteriorate the properties of the sensitized area of the defective part of the housing (welding part for attaching the neutron flux monitor housing).

 It does not meet the technical standards.

Considering these points, the neutron flux monitor housing 18
Repair work is performed.

After completion of this repair work, the faucet is removed, the neutron flux monitor main body 16 is guided into the neutron flux monitor housing 18, and is supported and fixed to 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 and fixed at the insertion position corresponding to the reactor pressure vessel through hole 23. A double seal structure can be adopted, and the reactor water leak can be reliably and effectively prevented.

Next, regarding the tube expansion method of the neutron flux monitor housing 18 which is carried out in the repair method of the long housing,
A more specific description will be given with reference to FIGS.

The expansion of the neutron flux monitor housing 18 is performed stepwise by using a housing expander. First, the upper stage 34a of the housing is expanded as shown in FIG. 5 (A), and then FIG. 5 (B). As shown in (4), the housing lower stage 34b is expanded. In this case, by expanding the neutron flux monitor housing 18 by crimping the housing 18 to the lower mirror through hole of the reactor pressure vessel 10, it is possible to fix the seal, but in order to improve the seal fixing, the through hole A labyrinth groove (not shown) may be formed in 23 in advance.

The feature of this neutron flux monitor housing 18 tube expansion method is that not only the housing but also the welded portion 26 of the housing 18 and the nozzle 25 or the nozzle 25 itself, even if cracks occur, Leakage to the outside of the pressure vessel 10 can be prevented, which is a highly versatile reactor water leak prevention measure.

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

This repair method omits the housing expanding step of expanding the neutron flux monitor housing 18 and closely fixing it to the lower mirror penetration portion of the reactor pressure vessel 10.

In other repair procedures, only the step shown in FIG. 1 (A) is omitted, and FIGS. 6 (A) to (C) correspond to FIGS. 1 (B) to (D), respectively. The same reference numerals are given and the description is omitted.

Also in the method of repairing the long housing shown in FIGS. 6 (A) to 6 (C), the through hole defect generation site 31 of the neutron flux monitor housing 18 is smaller than the inner diameter of the housing and withstands the internal pressure of the reactor during operation. Insert the repair sleeve 30 of the thickness to be obtained, expand the repair sleeve 30 from the inside so as to close the housing defect portion 31 and closely contact with the inner peripheral surface of the neutron flux monitor housing 18, and close the housing defect portion 31.
This blockage isolates it from the reactor water environment. Further, 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 development of the defect can be prevented.

Next, another embodiment of a repair method for a long housing is described in a seventh embodiment.
A description will be given with reference to FIGS.

The repair method for the long housing shown in this embodiment is
This is a repairing method in which the repair sleeve 35 is mounted in the neutron flux monitor housing 18 with a brazing filler metal 36.

Even when performing this repair method, remove the neutron detector 15 from the neutron flux monitor housing 18 upward, and after stopping the upper part of the housing with a faucet such as a bore plug, use a housing inner surface processing machine or a housing inner surface finishing machine for neutron The periphery of the penetrating defect portion of the bundle monitor housing 19 is subjected to boring, and the inner surface is finished as shown in FIG. 7 (A). After finishing the inner surface, the inner dimension of the housing is measured by the housing dimension measuring machine.

Then, a thin repair sleeve 35 is inserted into the neutron flux monitor housing 18. A brazing filler metal 36 is circumferentially applied to the upper and lower ends of the repair sleeve 35 as a brazing filler metal.
Instead of applying the gold brazing material 36 to the repair sleeve 35, it may be applied in advance above and below the penetrating defect portion whose inner surface is finished by boring.

Then, the repair sleeve 35 inserted into the neutron flux monitor housing 18 is positioned so as to close the defective portion of the housing from the inside, and after this positioning, the repair sleeve 35 is positioned by the extract band device as shown in FIG. 7 (B). Then, the tube is expanded and pressure-bonded to the inner peripheral surface of the neutron flux monitor housing 18 for close contact. At this time, the tube expansion ratio of the repair sleeve 35 is within about 10%, and the residual stress does not remain in the sleeve. The expanded state of the expanded repair sleeve 35 is measured by a sleeve dimension measuring machine.

The repair sleeve 35 expanded in the neutron flux monitor housing 18 is subsequently heated by the heating coil 37 as shown in FIG. 7 (C) to melt the brazing filler metal 36. This money wax
The repair sleeve 35 is fixed to the neutron flux monitor housing 18 by melting of 36. After the fixing, the heating coil 37 is removed from the repair sleeve 35 to form a repair structure for the long housing, and the repair work is completed.

In this case, since the brazing filler metal 36 is a chemically and physically stable substance, no adverse effects will occur, but the repair sleeve
Since 35 is fixed to the neutron flux monitor housing 18 by heating, it is necessary to sufficiently consider the sensitization of the material by heating. In this way, repair sleeve 35
Since the heating action is required for the attachment, the length of the repair sleeve 35 is longer than that of the repair sleeve 30 shown in FIG.

FIGS. 8A to 8C show still another embodiment of the repair method for the long housing.

In the repairing method shown in this embodiment, the repairing sleeve 30 inserted in the neutron flux monitor housing 18 is fixed to the inner surface of the housing of the remote laser welding machine. Of these repair methods, those shown in FIGS. 8 (A) and (B) are not different from the repair methods shown in FIGS. 7 (A) and (B), and therefore description thereof will be omitted.

On the other hand, as shown in FIG. 8 (C) by the remote laser welding machine, the repair sleeve 30 welded in the neutron flux monitor housing 18 is fixed by the nondestructive inspection device such as the PT device after the fixation. Confirmed, checked and repair work is completed. FIG. 8 (C) shows a repair structure for a long housing.

In this case as well, the same operational effects as those shown in FIG. 6 are exhibited.

Although the method of repairing the neutron flux monitor housing 18 and the repair structure thereof have been described in the embodiment of the present invention, the same can be applied to the case of the CRD 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 has a double seal structure from the beginning of the reactor construction by crimping and supporting the long housing in the penetration part of the reactor vessel by expanding the pipe. It may be supported.

〔The invention's effect〕

As described above, in the method for repairing the long housing such as the neutron flux monitor housing according to the present invention and the repair structure thereof, there is a penetration defect in the long housing itself such as the neutron flux monitor housing during the operation of the reactor. Even if it should occur, this defect occurrence position is closed from the inside with a repair sleeve that is inserted into the long housing, and at this closed position the repair sleeve is expanded and brought into close contact with the inner surface of the long housing. By fixing the to the long housing by welding, it is possible to reliably and quickly prevent the reactor water leak from the defective position of the long housing and suppress the development of the defective portion. Further, reliable repair can be performed by a simple repair work in a comparatively short time, the dose of radiation can be reduced, and the reliability can be improved.

In addition, if the long housing that is inserted through the through hole of the reactor vessel is expanded at the insertion position and seal-fixed to the through hole, the long housing should have a double seal structure together with the repair sleeve to be inserted. As a result, reactor water leakage can be reliably prevented and permanent sealing measures can be taken.

[Brief description of drawings]

1 (A) to 1 (D) are views showing an embodiment of a method of repairing a long housing and a repair structure thereof according to the present invention,
FIG. 2 is a diagram showing a lower structure of a boiling water reactor, FIG. 3 is a diagram showing a neutron flux detector fixedly supported by the reactor pressure vessel of FIG. 2, and FIG. 4 is the neutron flux detector. Showing a mounting structure for fixing and supporting the neutron flux monitor housing of FIG. 1 to the reactor pressure vessel, and FIGS. 5 (A) and 5 (B) are examples of the housing expanding process used in the repair method of the long housing of FIG. 6 (A) to 6 (C) are views showing another embodiment of the method for repairing a long housing and the repair structure thereof according to the present invention, FIGS. 7 (A) to (C) and 8 FIGS. 9A to 9C are views showing still another embodiment of the present invention, and FIG. 9 is a view schematically showing an installation example of a neutron flux detector attached to a conventional boiling water reactor. is there. 3 ... Reactor core, 5 ... Upper lattice plate, 10 ... Reactor pressure vessel, 13 ... Control rod drive mechanism, 14 ... CRD housing, 15
…… Neutron flux detector, 16 …… Neutron flux monitor main body, 17…
… Neutron flux monitor guide tube, 18 …… Neutron flux monitor housing, 23 …… Through hole, 25 …… Tube base (welded part), 26 …… Welded part, 30,35… Repair sleeve, 31… Defective part , 32 ……
Arm seam welding, 33 …… Seal welding, 36 …… Gold brazing,
37 …… Heating coil.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yasuhiro Hattori 1-1-1, Shibaura, Minato-ku, Tokyo Inside Toshiba Headquarters office (72) Inventor Toshihiro Yasuda 1-1-1, Shibaura, Minato-ku, Tokyo No. Stock Company Toshiba Head Office (56) References JP-A-2-98695 (JP, A) JP-A-56-82493 (JP, A)

Claims (4)

(57) [Claims] 1. A repair sleeve is inserted into a long housing such as a neutron flux monitor housing fixed to a welded portion of a reactor vessel, and the inserted repair sleeve covers a defect occurrence portion of the long housing from the inside. A method of repairing a long housing, which comprises closing the tube, expanding the repair sleeve at the closed position to bring the repair sleeve into close contact with the inner surface of the long housing, and fixing the closely attached repair sleeve to the long housing by welding. 2. A long housing such as a neutron flux monitor housing fixed to the lower mirror welded portion of the reactor vessel is expanded into a through hole of the reactor vessel at the insertion position to seally fix the long housing. Insert the repair sleeve into the housing,
A repair method for a long housing, comprising: closing a defect occurrence portion of the long housing from the inside with an inserted repair sleeve, and fixing the repair sleeve to the long housing at the closed position. 3. A repair sleeve is inserted into a long housing such as a neutron flux monitor housing fixed to a welded portion of a reactor vessel so as to close the housing defect occurrence portion from the inside, and the housing defect occurrence portion closed position. A repair structure for a long housing, characterized in that the repair sleeve is expanded and closely attached to the inner surface of the long housing to fix the repair sleeve to the long housing. 4. A long housing, such as a neutron flux monitor housing, which is fixed to the lower mirror welded portion of the reactor through the through hole of the reactor vessel, is expanded at the through hole insertion position to be fixedly sealed, while A repair structure for a long housing, characterized in that a repair sleeve is inserted into the long housing so as to block the housing defect occurrence portion from the inside, and the repair sleeve is fixed to the long housing at the closed position.