JPH02118499A - Repairing method for neutron flux monitor housing - Google Patents

Abstract

PURPOSE:To obtain high-reliability eternal countermeasure technique not except an existent housing by cutting an existent neutron flux monitor housing above a weld zone and detaching it, and inserting a new one from below and performing two-dimensional peripheral welding. CONSTITUTION:The existent neutron flux monitor housing 3 is inserted into the stab tube 2 on the internal surface of a nuclear pressure vessel lower end plate 1D while penetrating the wall of the lower barrel 1D and coupled with the tube 2 by the weld zone 4. The housing 3 after being cut above this weld zone 4 is detached from the tube 2 and weld zone 4 and the part of height where water leaks is removed. Then a new upper housing 3 is inserted into a through hole from below the lower end plate 1D and the existent housing 3 and existent tube 2 are fitted by simple two-dimensional peripheral welding. Further, the new lower housing 3 is inserted similarly and fitted to said new upper housing 3 by two-dimensional peripheral welding. Thus, the welding is all carried out by the two-dimensional peripheral welding which is easier than three-dimensional peripheral welding.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is used to repair a neutron flux monitor housing (hereinafter referred to as ICM housing) in a nuclear reactor pressure vessel (hereinafter referred to as RPV) during the service life of a nuclear power plant. Regarding how to.

[Conventional technology]

The ICM housing of the RPV of the boiling water reactor has a structure as shown in FIG. That is, a through hole IA is provided in the RPVI which is overlay welded using Inconel material or the like, and the stub tube 2 is attached so as to communicate with the through hole IA. This stub tube 2
An ICM housing 3 is attached via welds 4 through the wall of the RPVl.

Conventional boiling water reactor ICM housing 3 is 5US
304 series steel pipes are used, and the stress corrosion cracking resistance has been tested in case a through crack occurs at or near the welded part 4 of the ICM housing 3 and there is a possibility that reactor water leaks. It is necessary to establish in advance a method to replace the pipes with stainless steel pipes that have a high carbon content and low carbon content.

Regarding the repair of ICM housing, please refer to JP-A-56-82.
It is described in Japanese Patent No. 696, and the structure of the ICM housing after repair is shown in FIG.

[Problem to be solved by the invention]

The conventional ICM housing repair method described in Japanese Patent Application Laid-Open No. 56-82696 is a relatively easy method.

It cannot be considered as a permanent countermeasure construction method because the existing 0M housing 3 of the 5US304 series is left at the reactor pressure boundary.

Therefore, the purpose of the present invention is to add 5U to the reactor pressure boundary.
The object of the present invention is to provide a highly reliable permanent construction method that does not leave behind the already installed 0M housing 3 of the S304 series and performs all repair work such as welding and cutting in a relatively simple two-dimensional manner.

[Means to solve the problem]

A first means for achieving the above object is that the stub tube is inserted into a cylindrical stub tube attached to the inner surface of the reactor pressure vessel through the wall of the reactor pressure vessel, and is connected to the stub tube at a welded portion. In the existing cylindrical neutron flux monitor housing, the neutron flux monitor housing is cut above the welded part, and the existing neutron flux monitor housing is removed from the welded part with the stub tube, and a new upper neutron flux monitor is installed. The housing is inserted from the bottom of the reactor pressure vessel through the reactor pressure vessel through-hole and attached to the existing neutron flux monitor housing and the existing stub tube by two-dimensional circumferential welding, and then the new lower neutron flux monitor housing is inserted into the bottom of the reactor pressure vessel. A method for repairing a neutron flux monitor housing, characterized in that the housing is inserted through a through-hole in a reactor pressure vessel and attached to the new upper neutron flux monitor housing by two-dimensional circumferential welding, and the second means also includes the method for repairing a neutron flux monitor housing. In addition to this, the method for repairing a neutron flux monitor housing is characterized in that after removing the existing neutron flux monitor housing from the welded part with the stub tube, the welded part of the stub tube and the existing neutron flux monitor housing is scraped off. Similarly, the third means is a cylindrical stub tube that is inserted into a cylindrical stub tube attached to the inner surface of the reactor pressure vessel through the wall of the reactor pressure vessel, and is connected to the stub tube at a welded portion. In the existing neutron flux monitor housing,
Cut and remove the existing neutron flux monitor housing directly below the welded part between the existing neutron flux monitor housing and the existing stub tube, and insert the 1M neutron flux monitor housing from below the reactor pressure vessel through the reactor pressure vessel through hole. A method for repairing a neutron flux monitor housing, which is characterized by inserting and attaching it to an existing neutron flux monitor housing by two-dimensional circumferential welding; The present invention is a method for repairing a neutron flux monitor housing, characterized in that the new neutron flux monitor housing is made of stainless steel containing a low carbon content and is highly resistant to stress corrosion cracking.

[Effect]

In the first means, an existing cylindrical neutron is inserted into a cylindrical stub tube attached to the inner surface of the reactor pressure vessel through the wall of the reactor pressure vessel, and is connected to the stub tube at a welded portion. In the flux monitor housing, the neutron flux monitor housing is cut above the welded part, and then the existing neutron flux monitor housing is removed from the welded part with the stub tube, and the housing portion at the height where water leakage has occurred is removed. Then, a new upper neutron flux monitor housing was inserted from the bottom of the reactor pressure vessel through the reactor pressure vessel through hole, and the existing neutron flux monitor housing and the existing stub tube were welded together using a two-dimensional process that was easier than three-dimensional circumferential welding. Attach by circumferential welding. Further, a new lower neutron flux monitor housing is inserted from the lower part of the reactor pressure vessel through the reactor pressure vessel through hole and attached to the new upper neutron flux monitor housing by two-dimensional circumferential welding. In this way, all welding can be accomplished by two-dimensional circumferential welding, which is simpler than three-dimensional circumferential welding.

In the second means, in the method of the first means, after the existing neutron flux monitor housing is removed from the welded part with the stub tube, the welded part of the stub tube and the existing neutron flux monitor housing is made so that no cracks remain. Scrape away and prevent remaining cracks from growing later.

In the third means, the existing cylindrical neutron is inserted into a cylindrical stub tube attached to the inner surface of the reactor pressure vessel through the wall of the reactor pressure vessel and is connected to the stub tube at a welded portion. In the flux monitor housing, the existing neutron flux monitor housing is cut and removed from directly below the weld between the existing neutron flux monitor housing and the existing stub tube to eliminate cracks. Then, the new neutron flux monitor housing is inserted from below the reactor pressure vessel through the reactor pressure vessel through-hole and attached to the existing neutron flux monitor housing by two-dimensional circumferential welding, which is simpler than three-dimensional circumferential welding, and there is no cracking. Obtain a new installed neutron flux monitor housing.

According to the fourth means, 5 In any of the first means to the third means, the existing neutron flux monitor housing is replaced with a new neutron flux monitor housing made of low carbon content stainless steel with high stress corrosion cracking resistance. Since it is replaced, it can be repaired to a structure with less chance of cracking.

〔Example〕

Embodiments of the present invention will be described below with reference to FIG. 1 and FIGS. 5 to 13.

FIG. 1 shows an ICM housing 3 according to an embodiment of the present invention.
The figure shows the shape after repair. Figure 5 shows the lower mirror ID of RPVl.
Indicates the vicinity of the area. FIG. 6 shows a conventional structure for attaching the ICM housing 3 to the RPV1. Figure 6-1 shows the conventional I
A hypothetical case is shown in which a defect should occur near the welded portion 4 of the CM housing 3 and stub tube 2. FIG. 7 shows an outline of a method for repairing the ICM housing 3 according to an embodiment of the present invention. Figure 8 shows 2 used to carry out the present invention.
The configuration of the dimensional cutting machine 10 is shown. Figure 9-1, Figure 9-
FIG. 2 shows the configuration of a two-dimensional automatic welding machine 20 used to carry out the present invention. 10 to 13 show a repair procedure for the ICM housing 3 according to an embodiment of the present invention.

FIG. 5 shows the RPV lower mirror section of a boiling water reactor. R.P.
The VI is composed of an RPV fuselage IC, an RPV lower mirror ID, and an RPV upper cover (not shown). RPVI is attached to the reactor containment vessel pedestal (not shown) by skirt 5.
fixed on top.

The ICM housing 3 is fixed to the RPVT-mirror ID.

FIG. 6 shows a sectional view of the ICM housing through hole IA before repair, which is attached to the lower mirror ID of the boiling water reactor pressure vessel. During manufacture, the ICU housing 3 is welded to the inner surface of the reactor pressure vessel lower mirror 1D from the inside of the reactor pressure vessel by a stub tube 2 and partial welding 4. However, such welding is a welding method that is performed when the inside of the furnace is accessible to humans in the absence of radiation, and there are many difficult factors to weld the relevant parts after the plant is in operation.

FIG. 7 shows an ICM housing 3 according to an embodiment of the present invention.
An overview of the repair method is shown below. This repair work is performed by installing a remote-controlled two-dimensional processing machine 10 and a two-dimensional automatic welding machine 20 inside the RPV pedestal 31, and approaching the ICM housing 3 to be repaired from below the RPVI.

FIG. 8 shows a two-dimensional cutting machine 10 for implementing the present invention.
The configuration is shown below. The two-dimensional cutting machine 10 includes a driving power source 11. Control device 12. Processing head 13. Lifter (lifting device) 14. Drive mechanism 15, bite 16. It is composed of an operation panel 17.

The axial movement (upward and downward movement) of the two-dimensional processing machine 10 is performed by the beam lid 14, and the rotational movement in the circumferential direction and the feeding movement in the radial direction are performed by the drive mechanism 15.

The two-dimensional cutting machine 1o is remotely controlled by an operation panel 17.

9-1 and 9-2 show the configuration of a two-dimensional automatic welding machine 20 for carrying out the present invention. The two-dimensional automatic welding machine 20 includes a drive power source 21. Control device 22, welding head 23
．． Lifter (elevating device) 24° drive mechanism 25. Operation panel 26
The welding head 23 is equipped with a clamping device 27.
．． Torch 28° fiber scope/TV camera 29.
A wire feeding device 30 is incorporated. The axial movement (upward and downward movement) of the two-dimensional automatic welding machine 20 is carried out by the lifter 24.
The rotation movement in the circumferential direction and the feeding movement in the radial direction are performed by a drive mechanism 25, and the monitoring of the weld zone is performed by a fiberscope/TV camera 29. The two-dimensional automatic welding machine is remotely controlled by an operation panel 26. I according to an embodiment of the present invention as shown in FIGS. 10 to 13
A procedure for repairing the CM housing 3 will be shown. Figure 10~
The repair procedure shown in FIG. 13 shows the repair procedure for the virtual crack 32 shown in FIGS. First, as shown in Figure 10,
A remote-controlled two-dimensional cutting machine 10 is inserted into the ICM housing 3 to be repaired from below the RPVI from the lower end of the ICM housing 3, and above the welded part 4 of the already installed CM housing 3 and stub tube 2. CM already installed in
The housing 3 is cut and beveled. Then the 11th
As shown in the figure, the two-dimensional cutting machine 10 is used to remove the welded portion 4 between the installed CM housing 3 and the stub tube 2, thereby removing it from the installed CM housing 3 and the stub tube 2, and pulling it out below the RPV. Next, the first
As shown in Figure 2, a newly manufactured new upper ICM housing 6 made of low carbon stainless steel is inserted from below the RPV, and the existing C
The upper part of the M housing 3 is welded to the welding part 8. The length of the new upper ICM housing 6 is adjusted in advance so that its lower end is located on the stub tube 2, and then the first
As shown in FIG. 3, a new lower ICM housing 7 made of newly manufactured low carbon stainless steel is inserted from below the RPVI, and the new lower ICM housing 7 is welded at a location on the inner surface of the stub tube 2 by the two-dimensional automatic welding machine 20. It is welded to the upper ECM housing 6 by the welding part 9. Further, although not shown in the drawings, the two-dimensional cutting machine 10 performs internal finishing of the welded portions 8 and 9. In this way,
A virtual crack 32 as shown in FIG. 6-1 occurs near the weld 4 between the ICM housing 3 and the stub tube 2, and the coolant in the RPVI leaks into the ICM housing 3, the stub tube 2, and the RPV lower mirror ID. Even if leakage occurs through the gap between the new ICM and the
Can be replaced with housing. FIG. 1 shows a repaired ICM housing that has been repaired according to the procedure described above.

According to this repair method, the existing housing is removed.

Insertion of new housing 2 All repair work such as machining, welding, etc. can be performed from outside the lower part of the reactor pressure vessel lower mirror. Repair work is basically carried out after draining the reactor water, but even in this case, the upper side of the pressure vessel is in a high radiation environment, while the lower part of the pressure vessel is not as high in radiation levels and can be used for a short period of time. If so, humans can approach directly below the housing. This means that workability becomes significantly easier when handling repair equipment or replacing parts. Furthermore, when working from below, the existing housing can be removed or the repaired part can be approached linearly from inside the housing hole. On the other hand, when working from above, the reactor internals become an obstacle and it is not possible to approach the repaired area in a straight line, making it necessary to take a detour.

The possibility of direct access to the repair area is important when working under radiation conditions such as in nuclear reactor pressure vessels, and is important when carrying in and out parts or carrying in and out of remote automatic equipment, and when operating remote automatic equipment. Workability or device design and manufacturing efficiency is greatly improved.

Therefore, with this repair method, we have developed a repair method that overcomes the narrowness of the penetration, which was a problem when working from the bottom side, so that the above effects can be obtained, and specifically, all future repairs It is possible to increase the safety margin by reducing working hours, reducing radiation exposure for workers, rationalizing the design of remote automated equipment, jigs, etc., and improving costs.

Other embodiments of the invention are shown in FIGS. 2, 3, 6-1, and 14-20. 2 and 3 show the shape of the ICM housing 3 after repair according to another embodiment of the present invention. FIG. 6-1 shows a hypothetical case in which a defect should occur near the welded portion 4 of the conventional TCM housing 3 and stub tube 2. 14 to 20 show a repair procedure according to an embodiment of the present invention.

14 to 18 are I according to the second embodiment of the present invention.
A procedure for repairing the CM housing 3 will be shown. Figure 14~
The repair procedure shown in Figure 18 is for the virtual crack 3 in Figure 6-1.
The repair procedure for 3 is shown below.

In the case of the virtual crack 32, it is sufficient to replace the existing ICM housing 3 with a new ICM housing 6.7, but in the case of the virtual crack 33, since the crack has occurred in the welded part 4, the crack after repair is Considering the progress.

Preferably, the welded portion 4 is removed by the two-dimensional cutting machine 10. Therefore, in the second embodiment, in addition to the repair contents of the first embodiment, the work of scraping off the welded portion 4 is added. FIG. 2 shows a repaired 1CM housing that has been repaired according to the procedures shown in FIGS. 14 to 18.

FIGS. 19 and 20 show I according to the third embodiment of the present invention.
A procedure for repairing the CM housing 3 will be shown. The repair procedure shown in the figure shows the repair procedure j:@ for the virtual crack 34 in FIG. 6-1. ICM housing 3 for virtual crack 34
It is only necessary to replace the ICM housing on the lower side of the welded part 4 between the and the stub tube 2, and there is no need to replace the ICM housing on the upper side of the welded part 4 as in the first embodiment, simplifying the repair work. . FIG. 3 shows the repaired ICM/) housing which was repaired according to the procedures shown in FIGS. 19 and 20.

In both examples, 5US3 is applied to the reactor pressure boundary.
The existing CM housing of the 04 series is not left behind, and welded.
Since all repair work such as cutting can be performed in two dimensions, it is possible to provide a highly reliable permanent countermeasure construction method after repair.

〔Effect of the invention〕

According to the inventions of claims 1 and 3, no defective existing CM housing is left in the reactor pressure boundary, and all repair work such as welding and cutting during repair can be performed in two dimensions. , it is possible to provide a highly reliable permanent countermeasure construction method after repair.

According to the invention of claim 2, in addition to the effect of the invention of claim 1, it is possible to obtain a highly sound state in which no defects remain in the structure after repair.

According to the invention of claim 4, in addition to the effects of any one of the inventions of claims 1 to 3, the CM housing of the 5US304 series after repair can be removed without leaving the existing CM housing of the 5US304 system at the reactor pressure boundary. It is possible to provide a more reliable permanent countermeasure construction method.

[Brief explanation of the drawing]

1 to 3 are longitudinal sectional views of the ICM housing after repair according to the present invention, FIG. 4 is a longitudinal sectional view of the ICM housing showing a conventional ICM housing repair structure, and FIG. 5 is a longitudinal sectional view showing the RPV lower structure. 6 is a vertical cross-sectional view of a conventional ICM housing, and FIG. 6-1 is a vertical cross-sectional view of the vicinity of the ICM housing in the event that a crack occurs in the conventional ICM housing.
Fig. 7 is a schematic longitudinal sectional view of the repair method of the present invention, Fig. 8 is a structural explanatory diagram of the two-dimensional cutting machine used in the present invention, and Fig. 9-
Figures 1 and 9-2 are structural explanatory diagrams of the two-dimensional automatic welding machine used in the present invention, and Figures 9-2 (,) are A-A in Figure 9-2.
The arrow views and FIGS. 10 to 20 are procedural diagrams of the repair method of the present invention. 1...Reactor pressure vessel, IA...Lower mirror through hole, IB
... Overlay seat, i C・RP V JI 4 bodies, LD-
RP V lower mirror, 2... stub tube, 3... IC
M housing, 4... Welded part (ICM housing and stub tube), 5... Skirt, 6... New upper part I
CM housing, 7...New lower ICM housing,
8...Welding part (existing CM housing and new upper IC)
M housing), 9... Welding part (existing upper ICM housing and new lower ICM housing), 10... Two-dimensional cutting machine. 11... Drive power supply, 12... Control device, 13...
・Processing head, 14... Lifter (lifting device), 15.
...Drive mechanism, 16...Bite, 17...Operation panel,
18...Adapter, 20...Two-dimensional automatic welding machine,
21... Power supply for welding machine, 22... Control device, 23.
...Welding head. 24... Lifter (lifting device), 25... Drive mechanism, 2
7... Clamp device, 28... Torch, 29...
Fiberscope/TV camera, 30...Wire feeding device, 31...RPV pedestal, 32...Crack, foil 1 prisoner 20th 3rd trouble 4th figure spouting mouth 1st eye - 1st shadow figure s ``1 117-1 the 1st hair (Z mouth 14th vine 1st ward zO prisoner

Claims (1)

[Claims] 1. A cylindrical stub tube that is inserted into a cylindrical stub tube attached to the inner surface of the reactor pressure vessel through the wall of the reactor pressure vessel, and is connected to the stub tube at a welded portion. In the existing neutron flux monitor housing, the neutron flux monitor housing is cut above the welded part, the existing neutron flux monitor housing is removed from the welded part with the stub tube, and a new upper neutron flux monitor housing is attached to the atomic It is inserted from the bottom of the reactor pressure vessel through the reactor pressure vessel through hole and attached to the existing neutron flux monitor housing and existing stub tube by two-dimensional circumferential welding.
Further, a new lower neutron flux monitor housing is inserted from the lower part of the reactor pressure vessel through the reactor pressure vessel through hole and attached to the new upper neutron flux monitor housing by two-dimensional circumferential welding. Repair method. 2. The neutron flux monitor housing according to claim 1, wherein the welded portion between the stub tube and the existing neutron flux monitor housing is scraped off after the existing neutron flux monitor housing is removed from the welded portion with the stub tube. Repair method. 3. An existing cylindrical neutron flux monitor housing inserted into a cylindrical stub tube attached to the inner surface of the reactor pressure vessel through the wall of the reactor pressure vessel and connected to the stub tube at a welded portion. In this step, the existing neutron flux monitor housing is cut and removed from directly below the weld between the existing neutron flux monitor housing and the existing stub tube, and the new neutron flux monitor housing is installed from below the reactor pressure vessel through the reactor pressure vessel through-hole. A method for repairing a neutron flux monitor housing, the method comprising inserting it through the housing and attaching it to an existing neutron flux monitor housing by two-dimensional circumferential welding. 4. Repair of a neutron flux monitor housing according to any one of claims 1 to 3, characterized in that the new neutron flux monitor housing is made of low carbon content stainless steel with high stress corrosion cracking resistance. Method.