JP2000105292A - Preventive maintenance method and device for neutron measurement housing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce exposure amount for a worker by cladding by welding high corrosion resistance welding material to the inner surface by work of one stage in a preventive maintenance method for an ICM (neutron measurement) housing. SOLUTION: This preventive maintenance method for an ICM housing comprising a reactor pressure vessel having a build-up seat 12 on the inner surface, and a cylindrical ICM housing 5 passed through the build-up seat formed on the pressure vessel and fitted to the build-up seat by welding includes the steps of inserting an automatic welder 16 and a welding wire 17 in the ICM housing from below the reactor pressure vessel, welding the welding wire 17 by the automatic welder, and forming high corrosion resistance inner surface build-up layer 18 on the inner surface near the welded portion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for preventive maintenance of a neutron measurement (hereinafter referred to as "ICM") housing in a reactor pressure vessel in a nuclear power plant, and particularly to preventive maintenance of stress corrosion cracking of an ICM housing. Method and apparatus.

[0002]

2. Description of the Related Art A boiling water reactor pressure vessel has an elongated ICM housing penetrating a lower mirror of the pressure vessel.
The CM housing accommodates an ICM monitor that detects neutrons and monitors the output of the reactor. The part of the ICM housing that penetrates the lower mirror of the reactor pressure vessel is fixed to the lower mirror by welding.
A guide tube is connected by welding so as to extend the housing upward, and a lower end is provided with an ICM flange.

[0003] I in a nuclear power plant constructed earlier
The CM housing is an austenitic stainless steel containing a relatively large amount of carbon, such as SUS304, and the ICM housing using such a steel material has a problem in that the reactor pressure vessel and the housing are not affected by the thermal effect at the time of welding and the carbon content. , A high residual stress is generated near the welded portion, and a chromium-deficient layer is formed at the crystal grain boundary, thereby increasing the susceptibility to stress corrosion cracking. For this reason, the housing requires preventive maintenance measures to prevent stress corrosion cracking.

Conventionally, this kind of preventive maintenance measures include the following methods: (1) Inserting a thin-walled cylindrical sleeve into an ICM housing, and the cylindrical sleeve is subjected to preventive maintenance in the ICM housing. Guide to the location.
Next, a pipe expanding device is inserted into the ICM housing, and the thin sleeve is expanded to give plastic deformation to the thin sleeve.
It is crimped to the inner surface of ICM housing. Then, an automatic welding machine is inserted into the ICM housing, and the entire surface of the cylindrical sleeve is melted and welded to the inner surface of the ICM housing.
Alternatively, (2) applying a paste of metal powder to a required height range including a welded portion on the inner peripheral surface of the ICM housing to form a processed portion, and irradiating the processed portion with a laser to solidify the processed portion. Method, was adopted.

FIG. 15 is a flowchart showing the method (1).

First, in step S1, the main body of the ICM monitor is taken out from above the ICM guide tube provided to extend the ICM housing upward.

Next, in step 2, a faucet is attached to the upper part of the ICM guide tube, and the IC
Loosen the M flange and drain the cooling water from the ICM housing.

Next, in step S3, the ICM flange is removed.

Next, in step S4, the inner surface of the ICM housing is inspected. Also, the inner diameter of the ICM housing and the thickness of the ICM housing are measured.

Next, in step S5, a processing machine is inserted into the ICM housing, and the inner surface of the ICM housing in the vicinity of the welded portion of the ICM housing to the reactor pressure vessel is ground and removed to improve the insertability and adhesion of the cylindrical sleeve.

Next, in step S6, a post-processing inspection of the inner surface processing is performed.

Next, in step S7, a thin-walled cylindrical sleeve is inserted from below the ICM housing to the processed position of the ICM housing by a pipe expanding device, and the cylindrical sleeve is plastically deformed and pressed against the inner surface of the ICM housing.

Next, in step S8, an inspection after the sleeve is attached is performed.

Next, in step S9, an automatic welding machine is inserted from below the ICM housing, and the cylindrical sleeve is welded to the ICM housing. Next, step S1
At 0, a post-melt inspection of the cylindrical sleeve is performed.

Next, in step S11, an ICM flange is attached to the ICM housing.

Next, in step S12, the faucet attached to the upper part of the ICM guide tube is removed.

Next, in step S13, the ICM monitor is inserted into the ICM housing from above the ICM guide tube, and the mounting of the ICM monitor is completed.

[0018]

The above-mentioned conventional preventive maintenance measures require two steps since the welding machine is inserted and welded after the thin sleeve is mounted in the ICM housing. Further, when installing the thin-walled sleeve, the thin-walled sleeve must be inserted into the ICM housing having an inner diameter of about 38 mm from below the housing by remote operation, and mounted at a position advanced about 4 m upward, and the ICM housing is installed in the pressure vessel. Since many are accommodated, it takes a long time to perform the operation, and furthermore, such an operation is performed from below the ICM housing, that is, an operation under radiation, so that the amount of exposure of workers increases. There is.

Also, a method of applying a paste-like metal powder to a required height range including a welded portion on the inner peripheral surface of the ICM housing to form a portion to be processed, and irradiating the portion to be processed with laser irradiation to solidify the portion. Is also required in two steps, and there is a problem that the amount of exposure increases as in the case described above.

The present invention has been made in view of the above-mentioned various problems. A high corrosion-resistant welding material having a low carbon content is welded on the inner surface of an ICM housing in a one-step operation to thereby increase the stress of the ICM housing. A method and apparatus for preventing corrosion cracking is provided.

[0021]

The present invention employs the following means in order to solve the above-mentioned problems.

A neutron comprising a reactor pressure vessel having an overlaid seat formed on the inner surface thereof, and a cylindrical neutron measuring housing penetrating the overlaid seat formed on the pressure vessel and attached to and welded to the overlaid seat. In the preventive maintenance method for a measurement housing, a welding machine and a welding wire are inserted into the neutron housing from below the reactor pressure vessel, the welding wire is melted by the welding machine, and the neutron near the attached and welded portion is melted. A highly corrosion-resistant inner cladding layer is formed on the inner surface of the measurement housing.

[0023] Further, the reactor pressure vessel having an overlaid seat formed on the inner surface thereof, and a cylindrical neutron measurement housing which penetrates the overlaid seat formed in the pressure vessel and is attached to and welded to the overlaid seat. In the preventive maintenance method for a neutron measurement housing, after removing the inner surface of the neutron measurement housing near the attached and welded portion by mechanical means, a welding machine and a welding wire are inserted into the neutron housing from below the reactor pressure vessel. The welding wire is melted by the welding machine to form a highly corrosion-resistant inner cladding layer on the inner surface of the neutron measurement housing near the attachment-welded portion.

Further, in the preventive maintenance method for a neutron measurement housing, the part removed by the mechanical means is a part deformed by mounting welding.

Also, the welding head comprises a welding head outer cylinder which can be moved up and down and rotatable in the neutron measurement housing, and a welding block mounted on the welding head outer cylinder so as to be movable in a radial direction,
An automatic welding machine for a neutron measurement housing for overlay welding within the neutron measurement housing, wherein the welding head outer cylinder includes a mechanism for holding, moving up and down and rotating the outer cylinder, and the welding block includes a welding electrode, It is characterized by comprising a welding wire, a wire supply mechanism for supplying the wire, and a monitoring camera for monitoring the welding status.

Also, a processing head that can be raised and lowered and rotatable within the neutron measurement housing, a slide block attached to the processing head so as to be able to move back and forth toward the inner surface of the housing, and a rotatable cutter attached to the slide block A processing device for a neutron measurement housing for grinding and removing an inner surface of the neutron measurement housing, wherein the cutter includes an electric motor connected via a universal joint, and the processing head is a vertical core in the neutron measurement housing. And a clamp mechanism for fixing the processing head by aligning the vertical center of the processing head with the processing head.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a view showing a pressure vessel of a boiling water reactor according to the present embodiment, FIG. 2 is a view showing an ICM housing according to the present embodiment, and FIG. 3 is a view showing a state where the inner surface of the ICM housing according to the present embodiment is welded. FIG. 4 is a flowchart showing a method for welding the inner surface of the ICM housing according to the present embodiment.

In FIG. 1, reference numeral 1 denotes a reactor pressure vessel made of low alloy steel as a base material, 1a denotes a core support plate for supporting a core, 2
Is a pedestal, 3 is a support skirt, and the reactor pressure vessel 1 is supported on the pedestal 2 via the support skirt 3. 4 is a lower mirror of the reactor pressure vessel, 5 is SUS304,
An ICM housing made of stainless steel such as SUS316, 6 is an ICM guide tube configured to extend the ICM housing upward, 7 is an ICM flange, and 8 is an ICM.
A mounting bolt for mounting an ICM flange on a housing.

An ICM housing is attached to the lower mirror 4 of the reactor pressure vessel 1 by welding.
An ICM guide tube 6 is attached to the upper end of the base by welding. The ICM housing 5 and the ICM guide tube 6 are provided with an ICM monitor main body (not shown) containing a neutron measuring device.
The ICM monitor is inserted from above the CM guide tube and monitors the output of the reactor. Reference numeral 15 denotes a faucet, which will be described later. The faucet is provided on the upper part of the ICM guide tube when the ICM housing 5 is repaired, and the cooling water in the ICM housing is drained.

In FIG. 2, reference numeral 9 denotes an ICM monitor main body, 1
Reference numeral 0 denotes a through hole formed in the pressure vessel 1, reference numeral 11 denotes a built-up portion formed of high nickel steel (Inconel) or stainless steel formed inside the reactor pressure vessel 1, and reference numeral 12 denotes a through hole 10 formed on the inner surface side of the reactor pressure vessel. A padding formed on the periphery of high nickel steel (Inconel), 13 is a groove formed on the top of the padding, and 14 is a welded portion of high nickel steel (Inconel) formed on the groove.

The ICM housing 5 is inserted through the through hole 10 of the reactor pressure vessel 1, and the upper part of the ICM housing is welded on the inner surface side of the pressure vessel 1. Inside the reactor pressure vessel 1, a build-up portion 11 of high nickel steel or stainless steel is formed by welding to impart corrosion resistance. In addition, through hole 1
On the inner surface side of the reactor pressure vessel 1 of No. 0, a build-up seat 12 formed by build-up welding with high nickel steel is formed, and a groove 13 is formed above the build-up seat. The groove 13 is filled with high nickel steel, and the ICM housing 5 is welded to the overlay 12.

As described above, the ICM housing 5 is made of stainless steel. Particularly, in the nuclear power plant which was initially constructed, stainless steel having a high carbon content is adopted, so that the reactor pressure vessel 1 and the ICM housing 5 are made of stainless steel. Stress corrosion cracking may occur in the ICM housing near the weld with the housing, for example, the ICM housing immediately above the weld 14.

FIG. 3 is a diagram showing a state where the inner surface of the ICM housing is welded.

In the figure, 16 is an automatic welding machine, 17 is a welding wire formed of stainless steel having a low carbon content, 1
Reference numeral 8 denotes an inner surface overlay layer formed by welding the welding wire 17. An automatic welding machine 16 equipped with a welding wire 17 is inserted from below the ICM housing 5, and the welding wire 17 is melted on the inner surface of the ICM housing by the automatic welding machine 16 to form an inner build-up layer 18.

FIG. 4 is a flowchart showing a preventive maintenance method for the ICM housing according to this embodiment.

First, in step S1, the main body 9 of the neutron flux monitor is taken out from above the ICM guide tube 6 shown in FIG.

Next, in step S2, the faucet 15 is attached to the upper part of the ICM guide tube 6.

Next, in step S3, the bolt 8 is loosened to drain the cooling water from the ICM housing, and the ICM flange 7 is further removed.

Next, in step S4, the inner surface of the ICM housing is inspected. For the inner surface inspection, visual inspection, ultrasonic inspection, or eddy current inspection is performed to confirm the soundness of the ICM housing to be installed.
CM housing will be repaired separately. In addition, the inner diameter of the ICM housing and the thickness of the ICM housing are measured and used as construction data in the work of forming the inner cladding layer by the automatic welding machine.

Next, in step S5, an automatic welding machine equipped with a welding wire is inserted from below the ICM housing, and the welding wire is melted by the automatic welding machine 16 to obtain
An inner cladding layer 18 is formed on the inner surface of the CM housing.

Next, in step S6, as a post-weld inspection, a permeated liquid inspection test or a visual inspection is performed to confirm the soundness of the welded portion.

Next, in step S7, the ICM flange 7 is attached with bolts 8.

Next, in step S8, the faucet 15 disposed above the ICM guide tube 6 is removed.

Next, in step S9, the ICM monitor main body 9 is inserted into the ICM housing 5 from above the ICM guide tube 6, and the mounting of the ICM monitor is completed.

Next, a second embodiment of the present invention will be described with reference to FIGS.

FIG. 5 is a diagram showing a state in which the inner surface of the ICM housing is machined, FIG. 6 is a diagram showing a state in which the inner surface of the ICM housing is locally machined, and an inner surface overlay layer is formed on the inner surface, and FIG. It is a flowchart which shows the preventive maintenance method of such an ICM housing. 5 and 6,
Reference numeral 18a denotes an inner surface build-up layer formed on the inner surface of the ICM housing including the processing groove 20, 19 denotes a processing machine for removing the inner surface of the ICM housing by mechanical means, and 20 denotes a processing groove processed by the processing machine 19. In the drawings, the same portions as those shown in FIGS. 1 to 4 are denoted by the same reference numerals, and description thereof will be omitted.

In the ICM housing, as described above, the IC
Since the M monitor main body is inserted, if the build-up welding is performed in the ICM housing to form the build-up layer, the ICM monitor may not be able to be inserted. The machining groove 20 is the IC
The inner surface of the M housing in the vicinity of the welded portion with the reactor pressure vessel is formed by removing the inner surface by mechanical means to secure the inner diameter of the ICM housing after the build-up welding.
The insertion of the monitor body is guaranteed.

FIG. 7 is a flowchart showing a preventive maintenance method for the ICM housing according to the present embodiment.

First, in step S1, the ICM monitor main body 9 is taken out from above the ICM guide tube 6.

Next, in step 2, a faucet 15 is attached to the upper part of the ICM guide tube 6.

Next, in step S3, the bolt 8 is loosened to drain the cooling water from the ICM housing, and the ICM flange 7 is further removed.

Next, in step S4, the inner surface of the ICM housing is inspected. For the inner surface inspection, visual inspection, ultrasonic inspection, or eddy current inspection is performed to confirm the soundness of the ICM housing to be installed.
CM housing will be repaired separately. In addition, the inner diameter of the ICM housing and the thickness of the ICM housing are measured and used as construction data in the work of forming the inner cladding layer by the automatic welding machine.

Next, in step S5, a processing machine is inserted into the ICM housing from below the housing.
The inner surface of the ICM housing near the welded portion to the reactor pressure vessel is removed by mechanical means to form the machining groove 20.

Next, in step S6, an inner diameter measurement, a thickness measurement, and a visual inspection of the housing are performed as inspections after processing the ICM housing.

Next, in step S7, an automatic welding machine equipped with a welding wire is inserted from below the ICM housing, and the welding wire is melted by the automatic welding machine 16 on the inner surface of the portion including the machining groove 20 where the welding was performed. To form an inner cladding layer 18a.

Next, in step S8, as a post-weld inspection, a penetrant inspection test or a visual inspection is performed to confirm the soundness of the welded portion.

Next, in step S 9, the ICM flange 7 is attached with the bolt 8.

Next, in step S10, the faucet 15 disposed above the ICM guide tube 6 is removed.

Next, in step S11, the ICM monitor main body 9 is moved from the top of the ICM guide tube 6 to the ICM guide tube 6.
And the ICM monitor is inserted into the ICM housing 5 to complete the mounting of the ICM monitor.

Next, a third embodiment of the present invention will be described with reference to FIGS. FIG. 8 is a diagram showing a state in which the inner surface of the ICM housing is locally processed, FIG. 9 is a diagram showing a state in which the inner surface of the ICM housing is locally processed and then an inner surface buildup layer is formed on the inner surface, and FIG. 10 is an ICM according to this embodiment. It is a flowchart which shows the preventive maintenance method of a housing.

In FIGS. 8 and 9, reference numeral 18b denotes a processing groove 2;
0a, an inner cladding layer formed by melting a welding wire on the inner surface of the attachment-welded part including 20a;
This is a locally processed groove formed by locally processing the inner surface of the housing 5. In the drawings, the same portions as those shown in FIGS. 1 to 7 are denoted by the same reference numerals, and description thereof will be omitted.

The locally machined groove 20a is formed by removing the inner surface of the ICM housing near the welded portion of the ICM housing to the reactor pressure vessel by mechanical means.
The inside diameter of the M housing is secured, and the insertion of the ICM monitor main body is guaranteed.

The local machining groove 20a limits the area to be ground and removed to the minimum local area necessary for guaranteeing the insertion of the ICM monitor main body, thereby shortening the machining time and reducing the worker's exposure. Can be reduced.

FIG. 10 is a flowchart showing a preventive maintenance method for the ICM housing according to this embodiment.

First, in step S1, the ICM monitor main body 9 is taken out from above the ICM guide tube 6 shown in FIG.

Next, in step S2, a faucet 15 is attached to the upper part of the ICM guide tube 6.

Next, in step S3, the bolt 8 is loosened to drain the cooling water from the ICM housing, and the ICM flange 7 is further removed.

Next, in step S4, the inner surface of the ICM housing is inspected. For the inner surface inspection, visual inspection, ultrasonic inspection, or eddy current inspection is performed to confirm the soundness of the ICM housing to be installed.
CM housing will be repaired separately. In addition, the inner diameter of the ICM housing and the thickness of the ICM housing are measured and used as construction data in the work of forming the inner cladding layer by the automatic welding machine.

Next, in step S5, a working machine is inserted into the ICM housing from below the ICM housing, and the inner surface of the ICM housing near the welded portion to the reactor pressure vessel is locally ground and removed. A locally processed groove 20a is formed.

Next, in step S6, the inner diameter of the housing, the thickness of the housing, and the visual inspection are performed as inspections after processing the ICM housing.

Next, in step S7, an automatic welding machine equipped with a welding wire is inserted from below the ICM housing, and the welding wire is melted by the automatic welding machine 16 on the inner surface of the attachment-welded portion including the local machining groove 20a. Thus, the inner surface build-up layer 18b is formed.

Next, in step S8, as a post-weld inspection, a penetrant test or a visual inspection is performed to confirm the integrity of the welded portion.

Next, in step S 9, the ICM flange 7 is attached with the bolt 8.

Next, in step S10, the faucet 15 disposed above the ICM guide tube 6 is removed.

Next, in step S11, the ICM monitor main body 9 is inserted into the ICM housing 5 from above the ICM guide tube 6, and the mounting of the ICM monitor is completed.

Next, a fourth embodiment of the present invention will be described with reference to FIGS.

FIG. 11 is a longitudinal sectional view showing a use state of the automatic welding machine according to the present embodiment, and FIG. 12 is a view showing the entire configuration of the automatic welding apparatus.

In FIG. 11, reference numeral 21 denotes a hollow welding head outer cylinder arranged vertically, which is configured to be able to move up and down and rotate in the circumferential direction in the ICM housing. Reference numeral 22 denotes a welding block drive mechanism attached to the welding head outer cylinder 21, and reference numeral 23 denotes a welding electrode, which generates an arc between the electrode and the housing. Reference numeral 24 denotes a welding block to which the welding electrode 23 is attached, and the welding block drive mechanism 2
Driven back and forth by 2 to control the arc length during welding.

Reference numeral 25 denotes a welding wire, reference numeral 26 denotes a wire feeding mechanism attached to the welding head outer cylinder 21, and reference numeral 27 denotes an electric motor for driving the wire feeding mechanism 26. Wire feeding mechanism 26
Is provided with a mechanism for adjusting the position of the tip of the welding wire. The tip of the welding wire 25 is fed to the vicinity of the tip of the welding electrode 23, and the welding wire melted by the arc heat is supplied to the I.
Overlay welding on the inner surface of the CM housing.

Reference numeral 28 denotes a mounting box for mounting a surveillance camera, which is mounted near the center of the welding head outer cylinder 21;
Reference numeral 29 denotes a prism, and reference numeral 30 denotes a surveillance camera for monitoring the welding situation via the prism 29, which is housed in the mounting box 28 for protection. 1 to 10 in the drawings.
The same reference numerals are given to the same parts as those shown in FIG.

In FIG. 12, reference numeral 31 denotes an automatic welding machine support portion, and 32 denotes a relay box attached to the lower end of the ICM housing, which accommodates a motor for feeding the welding wire 25. 33 is attached to the lower part of the ICM housing,
A driving device for the automatic welding machine support 31, and a driving device 33
And an electric motor for vertically moving the automatic welding machine support portion 31, and a motor 35 for the driving device 33, which rotates the automatic welding machine support portion.

The automatic welding machine 16 is mounted on the upper part of the automatic welding machine support portion 31.
Up and down movement and rotation operation are performed by 4, 35.

Reference numeral 36 denotes a control device for driving and controlling the electric motors 34 and 35 and the electric motor for feeding the welding wire mounted in the relay box, 37 denotes a monitor cable,
38 is a monitor connected to the surveillance camera 30 via a monitor cable 37, 39 is a power cable for supplying welding power, 40 is a power cable for driving a motor, 41 is welding power and supplies power to a control device. Power supply device. In the drawings, the same parts as those shown in FIGS. 1 to 11 are denoted by the same reference numerals, and description thereof will be omitted.

The control device 36, the monitor 38, and the power supply device 41 are arranged on a floor separated from the reactor pressure vessel 1,
Automatic welding can be performed by remote control while monitoring the welding status on the monitor 38.

Next, a fifth embodiment of the present invention will be described with reference to FIGS.

FIG. 13 is a view showing a use state of the processing machine according to the present embodiment, and FIG. 14 is a view showing an entire configuration of the processing machine according to the present embodiment.

In FIG. 13, reference numeral 42 denotes a processing machine, which grinds and removes the inner surface of the ICM housing in the vicinity of the welded portion where the ICM housing is attached to the reactor pressure vessel as described above. 43 is a hollow processing head provided so as to be able to move up and down and rotate inside the ICM housing, 44 is a slide block provided above the processing head 43, 45 is a receiving table provided above the processing head, and 45 is a receiving table. A mechanism is provided for holding the slide block 44 movably back and forth toward the inner surface of the ICM housing. Reference numeral 46 denotes a plate spring, and 47 denotes a ball screw. The upper end of the plate spring 46 is bent in the horizontal direction in the vicinity of the receiving base 45 and is connected to the slide block 44. The other end of the leaf spring is coupled to a ball screw 47, and the leaf spring 46 is driven in the vertical direction in the drawing by the rotation of the ball screw 47.

48 is a cutter for grinding and removing the inner surface of the ICM housing, 49 is a bearing of the cutter 48, 50 is a spindle of the cutter, and the spindle of the cutter 48 is attached to the slide block 44 via a bearing 49. 51 is a shaft driven by an electric motor described below,
A universal joint 52 connects the shaft 51 and the spindle 50. In the drawings, the same portions as those shown in FIGS. 1 to 12 are denoted by the same reference numerals, and description thereof will be omitted.

The torque of the electric motor is transmitted to the cutter via the shaft 51, the universal joint 52 and the spindle 50, and drives the cutter 48 to rotate. Grinding of the inner surface of the ICM housing is performed by pressing a rotating cutter against the inner surface of the ICM housing. When the ball screw 47 is driven to move the leaf spring 46 in the vertical direction, the slide block 44 attached to the upper end of the leaf spring 46 is driven in the left-right direction in the drawing, and the cutter attached to the slide block is placed on the inner surface of the ICM housing. Can be imposed.

In FIG. 14, reference numeral 53 denotes a processing machine 42 connected to an IC.
A bolt attached to a flange formed at a lower portion of the M housing 5, a turning motor 54 for rotating the processing head 43 in the ICM housing, a lifting motor 55 for moving the processing head 43 up and down, and 56 rotating the shaft 51 Motor for driving the cutter by operating
Is a clamp mechanism that fixes the processing head to the ICM housing by aligning the vertical core of the ICM housing 5 with the vertical core of the ICM housing 5. During the operation, the processing head is firmly held so as not to be tilted by a reaction force during the grinding processing.

Although not shown, the processing machine 42 includes a control device, a monitor, and a power supply device. These devices are arranged on a floor separated from the reactor pressure vessel 1 and monitor the processing status with the monitor. Automatic processing can be performed by remote control.

[0092]

As described above, according to the present invention, a high corrosion resistance welding material having a low carbon content is welded onto the inner surface of an ICM housing in one step to prevent stress corrosion cracking of the ICM housing. In addition, the construction procedure is simplified, and the amount of exposure of the worker can be reduced. In addition, the automatic welding machine of the present invention can maintain a constant welding amount of the welding wire, so that a good build-up layer can be formed on the inner surface of the ICM housing and stress corrosion cracking can be satisfactorily prevented. Further, since the processing machine of the present invention can grind and remove only a necessary portion, work can be performed efficiently and in a short time.

[Brief description of the drawings]

FIG. 1 is a diagram showing a pressure vessel of a boiling water reactor according to a first embodiment of the present invention.

FIG. 2 is a diagram showing an ICM housing according to the first embodiment of the present invention.

FIG. 3 is a view showing a state where an inner surface of the ICM housing according to the first embodiment of the present invention is welded;

FIG. 4 is a flowchart illustrating a method of welding an inner surface of an ICM housing according to the first embodiment of the present invention.

FIG. 5 is a diagram showing a state where an inner surface of an ICM housing according to a second embodiment of the present invention is locally processed.

FIG. 6 is a view showing a state in which an inner surface buildup layer is formed on an inner surface of an ICM housing according to a second embodiment of the present invention after an inner surface of the ICM housing is locally processed.

FIG. 7 is a flowchart illustrating a preventive maintenance method for an ICM housing according to a second embodiment of the present invention.

FIG. 8 is a diagram showing a state where an inner surface of an ICM housing according to a third embodiment of the present invention is locally processed.

FIG. 9 is a diagram showing a state in which an inner surface buildup layer is formed on an inner surface of an ICM housing according to a third embodiment of the present invention, after the inner surface is locally processed.

FIG. 10 is a flowchart illustrating a preventive maintenance method for an ICM housing according to a third embodiment of the present invention.

FIG. 11 is a longitudinal sectional view showing a use state of an automatic welding machine according to a fourth embodiment of the present invention.

FIG. 12 is a diagram showing an entire configuration of an automatic welding device according to a fourth embodiment of the present invention.

FIG. 13 is a view showing a use state of a processing machine according to a fifth embodiment of the present invention.

FIG. 14 is a diagram showing an overall configuration of a processing machine according to a fifth embodiment of the present invention.

FIG. 15 is a flowchart showing a conventional ICM housing preventive maintenance method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reactor pressure vessel 2 Pedestal 3 Support skirt 4 Lower mirror 5 ICM housing 6 ICM guide tube 7 ICM flange 9 ICM monitor main body 11 Overlay portion 12 Overlay seat 13 Groove 14 Weld portion 15 Water faucet 16 Automatic welding machine 17 Welding Wire 18 inner surface build-up layer 19 processing machine 20 processing groove 21 welding head outer cylinder 23 welding electrode 24 welding block 25 welding wire 26 wire feeding mechanism 29 prism 30 monitoring camera 31 automatic welding machine support 32 relay box 33 drive Device 36 Control device 38 Monitor 42 Processing machine 44 Slide block 45 Receiver 47 Ball screw 48 Cutter 57 Clamp mechanism

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Minoru Otaka 3-2-2, Sachimachi, Hitachi City, Ibaraki Prefecture Within Hitachi New Clear Engineering Co., Ltd. (72) Inventor Hiroshi Takada Sachimachi, Hitachi City, Ibaraki Prefecture Hitachi 1-1, Hitachi Works, Ltd. (72) Inventor Tadashi Kume 3-1-1, Sakaimachi, Hitachi, Ibaraki Prefecture Hitachi Plant, Hitachi, Ltd. (72) Inventor Hiroshi Tsujimura Hitachi, Ibaraki 3-1-1, Ichiyukicho F-term (reference) in Hitachi, Ltd. Hitachi Plant 4E081 YS01 YX05 YY19 YY20

Claims (5)

[Claims] 1. A reactor pressure vessel having an overlaid seat formed on an inner surface thereof, and a cylindrical neutron measuring housing which penetrates the overlaid seat formed on the pressure vessel and is attached to and welded to the overlaid seat. In the method for preventive maintenance of a neutron measurement housing, a welding machine and a welding wire are inserted into the neutron housing from below the reactor pressure vessel, and the welding wire is melted by the welding machine, and the vicinity of the attached and welded portion is A preventive maintenance method for a neutron measurement housing, comprising forming a highly corrosion-resistant inner cladding layer on the inner surface of the neutron measurement housing. 2. A reactor pressure vessel having a build-up seat formed on an inner surface thereof, and a cylindrical neutron measurement housing that penetrates the build-up base formed in the pressure vessel and is attached to and welded to the build-up seat. In the preventive maintenance method for a neutron measurement housing, after removing the inner surface of the neutron measurement housing near the attached and welded portion by mechanical means, a welding machine and a welding wire are inserted into the neutron housing from below the reactor pressure vessel. And a welding wire is melted by the welding machine to form a highly corrosion-resistant inner cladding layer on the inner surface of the neutron measurement housing near the attachment-welded portion. 3. The preventive maintenance method for a neutron measurement housing according to claim 2, wherein the part removed by the mechanical means is a part deformed by mounting welding. 4. A welding head outer cylinder which can be moved up and down and rotatable in a neutron measurement housing, and a welding block mounted on the welding head outer cylinder so as to be movable in a radial direction, and a build-up welding is performed in the neutron measurement housing. An automatic welding machine for a neutron measurement housing, wherein the welding head outer cylinder includes a mechanism for holding, moving up and down and rotating the outer cylinder, and the welding block supplies a welding electrode, a welding wire, and the wire. An automatic welding machine for a neutron measurement housing, comprising a wire supply mechanism and a monitoring camera for monitoring a welding situation. 5. A processing head that can move up and down and rotate in a neutron measurement housing, a slide block attached to the processing head so as to be able to move back and forth toward the inner surface of the housing, and a rotatable cutter attached to the slide block. A processing device for a neutron measurement housing for removing an inner surface of the neutron measurement housing by mechanical means, wherein the cutter includes an electric motor connected via a universal joint, and the processing head is provided inside the neutron measurement housing. A processing device for a neutron housing, comprising: a clamp mechanism for fixing the processing head by aligning a vertical core of the processing head with a vertical core of the processing head.