JP2005345296A - Machining device of reactor pressure vessel and its machining method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reactor bottom structure machining device and its machining method capable of various kinds of machine works to the reactor bottom structure by remote control of the machining device inserted/removed through a penetration hole of control rod driving mechanism housing from the pedestal side positioned under a reactor pressure vessel, and storing inside a chip recovery hose. <P>SOLUTION: A weld zone of a stub tube which is a machining object in the reactor pressure vessel is enclosed by a cylindrical member, to thereby put the inside of the cylindrical member into the aerial state, and a machining head part of the machining device is inserted into the inside of the control rod driving mechanism housing which is a machining object or into the through hole of the reactor pressure vessel for allowing the control rod driving mechanism housing to penetrate, from the pedestal side supporting the reactor pressure vessel from below. Then, the control rod driving mechanism housing or the stub tube which is the machining object is cut circularly, or a machining work of an excess thickness part after cutting is performed on the trace of a reactor bottom shape of the reactor pressure vessel. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a processing apparatus and a processing method for repairing or replacing a structure formed on the bottom of a reactor pressure vessel.

  15 and 16 are views showing a state in which a reactor bottom structure of a reactor pressure vessel according to a conventional technique is repaired. FIG. 15 shows a control rod drive mechanism housing 3 which is accessed from the operation floor side above the reactor inside which is not shown in the figure, and which remotely operates the high pressure water jet device 51 in water and penetrates the bottom of the reactor pressure vessel 1. The stub tube 4 provided in the penetrating portion of the control rod drive mechanism housing 3 is cut and processed. FIG. 16 is also accessed from the operation floor side, and the stub tube 4 is remotely operated in water by remotely operating the electrolytic discharge machining device 52. The state where the installation part of is subjected to electric discharge machining is shown.

Patent Document 1 below describes a technique for repairing the neutron flux monitor housing from the furnace bottom side.
Japanese Unexamined Patent Publication No. 2-98697

When machining the furnace bottom structure using the conventional processing apparatus shown in FIG. 15 and FIG. 16 described above, a device is required that is long from the operation floor to the work site at the furnace bottom and collects chips in water. Therefore, there is a drawback that the processing apparatus itself becomes a large facility.
Moreover, since the conventional processing apparatus described in FIG. 15, FIG. 16, and patent document 1 has only a single function, there existed a fault that only limited processing was possible with respect to each furnace bottom part structure.

  The present invention has been made in view of the above-described conventional circumstances, and is inserted / removed from the pedestal side supporting the reactor pressure vessel through the through hole of the control rod drive mechanism housing, and the cutter and the chip recovery hose are accommodated therein. It is an object of the present invention to provide a reactor pressure vessel processing apparatus and a processing method thereof capable of performing various types of machining on the reactor bottom structure by remotely operating the processing apparatus.

  In order to achieve the above object, a reactor pressure vessel processing method according to a first aspect of the present invention includes a control rod drive mechanism housing fixed through the bottom of the reactor pressure vessel and a stub tube around the control rod drive mechanism housing. In the method of processing a furnace bottom structure composed of, etc., the inside of the cylindrical member is placed in the air by surrounding the welded portion of the furnace bottom structure to be processed with the cylindrical member, and controlled from the control rod drive mechanism housing. After pulling out the rod drive mechanism, the machining head portion of the machining apparatus is inserted into the control rod drive mechanism housing to be machined from the pedestal side that supports the reactor pressure vessel, and the control rod drive mechanism housing to be machined is It is characterized by cutting in an annular shape from the inner diameter side.

  Further, the invention of the method of processing a reactor pressure vessel according to claim 2 is directed to a reactor bottom portion comprising a control rod drive mechanism housing fixed through the reactor bottom portion of the reactor pressure vessel and a stub tube around the control rod drive mechanism housing. In a method of machining a structure, by enclosing a welded portion of a furnace bottom structure to be processed with a cylindrical member, the inside of the cylindrical member is brought into an air state, and the control rod driving mechanism is pulled out from the control rod driving mechanism housing. After that, insert the machining head part of the machining device into the control rod drive mechanism housing to be machined from the pedestal side that supports the reactor pressure vessel, and cut the control rod drive mechanism housing to be machined annularly from the inner diameter side. After that, the lower cutting side of the control rod drive mechanism housing is removed, and then the stub tube is annularly cut from the inner diameter side, and the upper cutting side after the cutting is removed Wherein the processing by following the excess thickness portion to the furnace bottom portion shape of the reactor pressure vessel.

  According to a third aspect of the present invention, there is provided a reactor pressure vessel processing apparatus comprising: a control rod drive mechanism housing fixed through the reactor bottom portion of the reactor pressure vessel; a stub tube surrounding the control rod drive mechanism housing; The structure is annularly formed by the machining head portion of the machining apparatus in which the structure is inserted from the pedestal side of the reactor pressure vessel into the control rod drive mechanism housing to be machined or through the through hole of the reactor pressure vessel that penetrates the control rod drive mechanism housing. In the reactor pressure vessel processing apparatus configured to machine the cut or surplus portion after cutting in accordance with the shape of the bottom of the reactor pressure vessel, the inside of the control rod drive mechanism housing to be processed or the atom A cutter that is inserted into a through hole of a control rod drive mechanism housing provided in the furnace pressure vessel to machine the furnace bottom structure, and this cutter is rotated. A processing head portion having a rotary shaft and a cutting shaft for taking in and out the rotary shaft of the cutter, and a main body drive mechanism portion supported by a base plate at the lower end of the control rod drive mechanism housing adjacent to the workpiece, and having a turning shaft and a lifting shaft And a strut portion that connects the machining head portion and the main body drive mechanism portion to transmit the driving torque of the main body drive mechanism portion to the machining head portion.

  The reactor pressure vessel processing apparatus of the present invention and the processing method thereof do not employ a method in which an operator accesses from the pedestal side below the reactor pressure vessel and processes using a hand tool or a jig, Because the machining head is inserted into and removed from the control rod drive mechanism housing through hole in the pedestal, and the cutter is replaced and the machining head replaced in the pedestal, there is no risk of exposure to radiation during work. In addition, various types of machining can be performed on the furnace bottom structure.

  The present invention relates to a control rod drive mechanism housing and a stub tube which are inserted into a control rod drive mechanism housing at a machining target part from the pedestal side under the furnace and are removably fixed to the tip of the machining head. The present invention relates to a reactor pressure vessel processing apparatus and a method for processing the reactor bottom structure that can be cut into a ring shape or machined into a flat or inclined surface following the shape of the bottom.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same part through each figure, and the overlapping description is abbreviate | omitted.

  In the following explanation, in order to facilitate understanding of the present invention, the structure of the processing apparatus itself and the state in which the reactor bottom structure of the reactor pressure vessel is repaired using this processing apparatus prior to the method of loading and installing the processing apparatus. Will be described.

  1 is a block diagram of a processing apparatus, FIG. 2 is a view taken along the line AA in FIG. 1, FIG. 3 is a detailed view of a portion B in FIG. 1, and FIG. 4 is a repair processing of a bottom structure of a reactor pressure vessel. It is a figure explaining the situation to do. In FIG. 1, reference numeral 1 denotes a reactor bottom portion of a reactor pressure vessel 1 in a water-filled state, 3 denotes a control rod drive mechanism housing fixed through the reactor bottom portion of the reactor pressure vessel 1, and 4 denotes a control rod drive mechanism It is a stub tube that welds the penetration part of the housing 3 and the furnace bottom part. In this embodiment, first, the control rod drive mechanism is pulled out from the control rod drive mechanism housing 3 to form a hollow tube, and the sealed cylindrical member 2 is welded so as to surround the stub tube 4 substantially concentrically. To fix.

  As described above, since the stub tube 4 is welded so as to be concentrically surrounded by the sealed cylindrical member 2, the water stretched on the reactor pressure vessel 1 does not enter the sealed cylindrical member 2. And machining such as cutting of the stub tube 4 can be performed in the air instead of in the water.

  After the above preparation is completed, the cutter and the processing tool of the processing apparatus 20 are inserted into the hollow tube of the housing 3 from the pedestal (described later) side under the furnace. Although a large number of control rod drive mechanism housings 3 are actually provided, only one control rod drive mechanism housing 3 is shown in FIG. 1 to avoid complexity.

  The processing device 20 is roughly composed of the following three elements. That is, the processing device 20 includes a processing head portion 21 for mounting a processing tool such as a cutter 24 for cutting the control rod drive mechanism housing 3 and the stub tube 4, and a processing tool such as the cutter located at the lowermost part in the figure. The driving mechanism unit 23 that outputs a driving torque for driving the motor 24, the machining head unit 21, and the driving mechanism unit 23 are coupled to each other, and the driving torque is transmitted to the machining tool 24 so that it can be turned and moved up and down. And the support column 22.

  The drive mechanism 23 is fixed to a base plate 40 provided at the lower end of the housings 3a and 3b adjacent to the control rod drive mechanism housing 3 to be processed, and the entire weight is supported by the base plate 40.

  Further, the processing head portion 21 is configured to be inserted into the control rod drive mechanism housing 3 to be processed from the pedestal side under the furnace, and as shown in FIG. 2, a cutter 24 as a processing tool, A monitoring camera 26 for remotely monitoring the cutting status and wear status of the cutter 24 and the amount of chips generated during the cutting, and a chip suction port 28 for sending the chips to an external collecting device Provided.

  The cutter 24 is driven to rotate by a cutter rotating shaft 24-1 and is configured so that the protruding state of the cutter can be adjusted by a cutting shaft 24-2. The processing head portion 21 is inserted into a predetermined position inside the housing 3. When pulling from the predetermined position to the pedestal, the cutter 24 itself is accommodated by moving the position of the cutting shaft 24-2 into the machining head portion 21. During the cutting operation, the protruding amount of the cutter 24 is adjusted. You can cut while.

  Further, as shown in the cross-sectional view of FIG. 3A, the machining head portion 21 is provided with a plurality of centering guides 25 at equal intervals in the circumferential direction on the outer peripheral portion, and the machining head portion 21 is controlled by a control rod. When inserted into the internal space of the drive mechanism housing 3 or the through hole of the pressure vessel, it is configured so as to project evenly in the radial direction to produce a centering function. ), The cutter 24 can be adjusted up and down by providing an annular hydraulic cylinder 21J. The centering guide 25 is provided with a sliding member at the contact portion in order to smoothly insert and remove the processing head portion 21.

  By the way, the machining apparatus 20 shares the support column 22 and the drive mechanism 23, and is configured to perform various types of machining by simply replacing the machining tool 24 or the machining head 21.

  In addition to the power transmission unit, the support column 22 is provided with a chip collection hose 27, and the chips sucked by the chip suction port 28 of the processing head unit 21 are externally connected via the chip collection hose 27. It collects to the collection device.

  Further, in order to prevent the machining head portion 21 from shaking due to vibrations generated during the cutting operation, as shown in FIG. 4, the control rod drive mechanism housings 3a, 3b adjacent to the reactor pressure vessel 1 immediately below the reactor bottom portion. The triangular pedestal 30 is fixed to the pedestal 30, and a guide jig 31 is fixed to the pedestal 30. The guide jig 31 supports the processing head portion 21 and the support column portion 22 while rotating from the circumferential direction. ing.

The machining head unit 21 is remotely operated by a control operation panel 29 installed outside the pedestal 5 through a monitoring control cable 29C.
The case where the existing or new furnace bottom structure is removed by the processing apparatus 20 configured as described above will be described with reference to FIGS. 3 and 4.

(I. Removal of existing furnace bottom structure)
When removing the existing furnace bottom structure, the following process is performed.
(I-1). First, in FIG. 5, a cutter 24 a is attached to the distal end portion of a machining head portion 21 a designed to have an outer diameter that fits in the inner space of the control rod drive mechanism housing 3, and the position of the cutter 24 a is supported by the base plate 40. The height is adjusted by the elevating shaft of the main body drive mechanism 23 and set to a predetermined cutting height.

(I-2). Next, while rotating the cutter 24a, the cutting shaft (not shown) is projected to a predetermined dimension corresponding to the thickness of the control rod drive mechanism housing 3, and the post-processing head portion 21a is turned by the main body drive mechanism portion 23. The control rod drive mechanism housing 3 is cut up and down 3-1 and 3-2 in the vicinity of the welded portion of the pressure vessel 1 by rotating 360 degrees around a shaft (not shown).

(I-3). In this state, the portion 3-1 located above the cut portion of the control rod drive mechanism housing 3 is fixed to the stub tube 4, but the portion 3-2 located below the cut portion is free. Therefore, it can be removed by drawing to the lower pedestal side.

(I-4). Next, in FIG. 6, the machining head portion 21a is replaced with a machining head portion 21b designed to have an outer diameter size corresponding to the outer diameter size of the control rod drive mechanism housing 3, that is, the size of the through hole of the pressure vessel 1, and the control is performed. As in the case of the cutting process of the rod drive mechanism housing 3, the cutter 24 is turned so as to make a round in the stub tube 4 and cut, and the upper side 4-1 of the cut portion is lifted from the operation floor and removed. .

(I-5). Further, in order to remove the lower surplus portion 4-2 remaining on the pressure vessel 1 after the stub tube 4 is cut, a cutter provided at the tip of the processing head portion 21b from the operation floor as shown in FIG. 24b is replaced with a structural unit that rotates on a horizontal axis perpendicular to the vertical direction and a cutter 24c of an end mill, and then the swivel axis and the elevating axis of the main body drive mechanism 23 are controlled so that the stub tube 4 installation part at the bottom of the furnace This is done by flattening following the tilt angle.

  In the case of the step (I-4), the machining head portion 21a is replaced with 21b and the cutting process is performed, but the centering guide 25 functions so that no vibration is generated between the machining head portion 21a and the through hole. In addition, when the cutting amount of the cutter 24a can be adjusted so that the stub tube 4 can be cut into an annular shape, it is not necessary to replace the processing head portion 21a with 21b.

(II. Removal of the new furnace bottom structure)
(II-1). When forming a new furnace bottom structure, an annular seating surface that follows the inclination angle of the newly installed stub tube 4 is processed in the same manner as the removal process of the lower surplus portion 4b of the stub tube 4 described above. (See FIG. 7).

(II-2). Next, the processing head portion 21b is replaced with a conical groove processing cutter 24d, and an inclined processing for groove welding is performed on the annular seat surface of the stub tube 4 formed in the same manner as described above (see FIG. 8). ).
This is the end of the description of the processing operation for removing the furnace bottom structure by the processing apparatus 20.

(III. Method of installing processing equipment)
Next, a method of installing the processing apparatus 20 on the bottom of the reactor pressure vessel will be described with reference to FIGS.

  In FIG. 9, reference numeral 5 denotes a pedestal formed in a substantially cylindrical shape to support the reactor pressure vessel 1, and the control rod drive mechanism and the control rod drive mechanism housing 3 are accommodated immediately below the reactor pressure vessel 1. While having the accommodating part 5a, it has the carrying-in / out opening 5b for carrying in / out a control-rod drive mechanism housing in a side part.

When processing the bottom of the reactor pressure vessel, the following steps are performed.
(III-1). First, the sealed cylindrical member 2 is fixed to the pressure vessel 1 by welding so as to surround the outer periphery of the annular welded portion of the processing object control rod drive mechanism housing 3 in a state where the pressure vessel 1 is filled with water.

(III-2). The base plate 40 is attached to the lower ends of the adjacent control rod drive mechanism housings 3a and 3b. The base plate 40 may be attached to the lower ends of the control rod drive mechanism housings 3a and 3b in advance.

(III-3). Thereafter, the machining head portion 21 and the support column portion 22 are connected outside the furnace, and are mounted on the existing control rod drive mechanism housing carry-in / out cart 11 while maintaining the connected state, and are accommodated from the carry-in / out port 5b of the pedestal 5 It carries in in 5a (refer FIG. 9).

(III-4). Then, the loaded processing head portion 21 and the column portion 22 are transferred to the existing control rod drive mechanism housing exchanger 12 and raised, and in this state, the processing head portion 21 and the column portion 22 are placed on the axis on the XY plane. It is moved to a position where it can be inserted into the inside of the control rod drive mechanism housing 3 or the through hole of the pressure vessel 1.

(III-5). When the position is determined, the machining head portion 21 and the column portion 22 are raised by the control rod drive mechanism housing exchanger 12 (see FIG. 10).
(III-6). After the processing head portion 21 and the column portion 22 are held on the base plate 40 and temporarily placed, the control rod drive mechanism housing exchanger 12 is retracted.

(III-7). On the other hand, the main body drive mechanism 23 is mounted on the lifter carriage 41, carried into the pedestal 5 from outside the furnace, and installed on the base plate 40 (see FIG. 11). At this time, the support column 22 and the pivot shaft flange (not shown) of the main body drive mechanism 23 are connected.

(III-8). The lifter carriage 41 is withdrawn, and wiring and piping from the apparatus control panel 29 outside the furnace, the main body drive mechanism section 23 and the column section 22 are connected to complete the installation (see FIG. 12). FIG. 1 shows an enlarged view of this state.
This is the end of the description of the method for installing the processing apparatus on the bottom of the reactor pressure vessel.

(IV. Cutter replacement, processing head replacement)
Next, the steps for exchanging the cutter and replacing the machining head during the machining operation will be described with reference to FIGS.

(IV-1). The pivot shaft flange of the main body drive mechanism 23 is separated from the support column 22, and the support 22 is temporarily placed on the base plate 40 (see FIG. 14).
(IV-2). The main body drive mechanism 23 is removed from the base plate 40, mounted on the lifter carriage 41, and retracted (see FIG. 13).

(IV-3). The support rod 22 is received and lowered by the control rod drive mechanism housing exchange 12.
In the state where the processing head portion 21 is lowered, the cutter is replaced or the processing head portion is replaced (see FIG. 13).

(IV-4). When removing an existing surplus portion of the stub tube 4 or attaching a processing head portion 21b for forming and processing a seating surface in a new installation, the processing head portion 21 is suspended from the operation floor side by using a detachable lifting tool and sealed. Inserted into the through-hole of the pressure vessel 1 through the cylindrical member 2, the processing head portion 21 and the column portion 22 are connected in a state where the main body drive mechanism 23 and the column portion 22 are installed on the base plate 40 (see FIG. 14). ).

  As described above, according to the present embodiment, the machining operation such as a plane, an inclined surface, or the like that is cut in an annular shape with respect to the furnace bottom structure or formed in an annular shape following the furnace bottom inclination with the working environment in the air. Because it can be performed in the air, and it is installed and inserted from the pedestal side below the easily accessible pressure pedestal for remote operation, it is possible to reduce the radiation exposure of the worker compared to the conventional case. .

  Further, the chips generated during processing can be sucked from a chip suction port provided in the processing head and collected by an external chip collecting device via a chip collecting hose accommodated in the processing apparatus.

The block diagram which shows one Example of the processing apparatus by this invention. The AA arrow directional view of FIG. FIG. 3 is a detailed view of a portion B in FIG. 1, in which FIG. 3A is a cross-sectional view and FIG. 3B is a vertical cross-sectional view. The figure which shows the shake prevention jig | tool of FIG. The figure which shows the mode of the removal process of the existing furnace bottom part structure. The figure which shows the mode of the removal process of the existing furnace bottom part structure. The figure which shows the mode of a formation process of the newly installed furnace bottom part structure. The figure which shows the mode of a formation process of the newly installed furnace bottom part structure. The figure which shows the installation procedure of the processing apparatus by this invention. The figure which shows the installation procedure of the processing apparatus by this invention. The figure which shows the installation procedure of the processing apparatus by this invention. The figure which shows the installation procedure of the processing apparatus by this invention. The figure which shows the replacement method of a process head part. The figure which shows the replacement method of a process head part. The figure which shows the processing method 1 in the conventional furnace bottom part structure repair. The figure which shows the processing method 2 in the conventional furnace bottom part structure repair.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Pressure vessel, 2 ... Sealed cylindrical part, 3, 3a, 3b ... Control rod drive mechanism housing, 4 ... Stub tube, 5 ... Pedestal, 5a ... Accommodating part, 5b ... Carry-in / out port, 20 ... Processing apparatus, 21, 21a , 21b ... Processing head part, 21J ... Hydraulic jack, 22 ... Post part, 23 ... Main body drive mechanism part, 24, 24a, 24b, 24c ... Cutter, 25 ... Centering guide, 26 ... Monitoring camera, 27 ... Chip collection Hose, 29 ... control operation panel, 29C ... monitoring and control cable, 31 ... guide jig, 40 ... base plate.

Claims (9)

In a processing method of processing a reactor bottom structure composed of a control rod drive mechanism housing fixed through the reactor bottom of a reactor pressure vessel and a stub tube around the control rod drive mechanism housing,
By enclosing the welded part of the reactor bottom structure to be processed with a cylindrical member, the inside of the cylindrical member is brought into the air state, and after the control rod drive mechanism is pulled out from the control rod drive mechanism housing, the reactor pressure vessel is supported. The reactor pressure is characterized in that the machining head portion of the machining apparatus is inserted into the control rod drive mechanism housing to be machined from the pedestal side, and the control rod drive mechanism housing to be machined is annularly cut from the inner diameter side. Container processing method. In a processing method of processing a reactor bottom structure composed of a control rod drive mechanism housing fixed through the reactor bottom of a reactor pressure vessel and a stub tube around the control rod drive mechanism housing,
By enclosing the welded part of the reactor bottom structure to be processed with a cylindrical member, the inside of the cylindrical member is brought into the air state, and after the control rod drive mechanism is pulled out of the control rod drive mechanism housing, the reactor pressure vessel is supported. After inserting the machining head portion of the machining apparatus into the control rod drive mechanism housing to be machined from the pedestal side, and cutting the control rod drive mechanism housing to be machined annularly from the inner diameter side, the control rod drive mechanism housing Next, the stub tube is cut into an annular shape from the inner diameter side, the upper cut side after cutting is removed, and the lower surplus portion is machined according to the shape of the bottom of the reactor pressure vessel A method for processing a reactor pressure vessel. Control of the object to be processed from the pedestal side of the reactor pressure vessel, such as the control rod drive mechanism housing fixed through the reactor bottom of the reactor pressure vessel and the surrounding stub tube, etc. Cut into the ring at the machining head of the machining device inserted through the through hole of the reactor pressure vessel that penetrates the rod drive mechanism housing or through the control rod drive mechanism housing, or the surplus portion after the cut is the reactor bottom of the reactor pressure vessel In the reactor pressure vessel processing device configured to machine according to the shape,
A cutter that is inserted into a through hole of a control rod drive mechanism housing provided in a control rod drive mechanism housing or a reactor pressure vessel to be machined to machine the reactor bottom structure, a rotary shaft that rotates the cutter, and A machining head portion having a cutting shaft for taking in and out a rotating shaft of the cutter, a main body driving mechanism portion supported by a base plate at a lower end of a control rod drive mechanism housing adjacent to the workpiece, and having a swivel shaft and a lifting shaft; An apparatus for processing a reactor pressure vessel, comprising: a support head portion that connects a processing head portion and a main body drive mechanism portion to transmit a driving torque of the main body drive mechanism portion to the processing head portion.   The main body drive mechanism unit and the support column unit are shared, and the processing head unit is configured to be detachable so that the processing head unit or the processing tool can be changed according to the structure to be processed. The reactor pressure vessel processing apparatus according to claim 3.   4. The nuclear reactor according to claim 3, wherein the cutter is housed in the machining head when the machining head is installed and inserted, and the position of the cutting shaft is remotely controlled so that the cutter protrudes from the machining head during cutting. Pressure vessel processing equipment.   A cutter can rotate on a horizontal axis perpendicular to the vertical direction at the tip of the processing head part, and the pivot axis and the lifting axis of the main body drive mechanism part are controlled to control the reactor bottom structure of the reactor pressure vessel. 4. The reactor pressure vessel processing apparatus according to claim 3, wherein the annular surface is processed following the installation angle.   When the machining head part is inserted into the control rod drive mechanism housing or the through hole of the pressure vessel, a plurality of centering guides arranged on the outer periphery of the machining head part project equally in the radial direction and contact with the centering guide. 4. The reactor pressure vessel processing apparatus according to claim 3, wherein the portion has a tensioning centering function that can be rotated by a sliding member.   A monitoring camera and a chip suction port are provided in the vicinity of the cutter mounting portion, and the cutter is worn, cut, and the amount of chips is remotely monitored, and cut through a suction hose communicating with the chip suction port. 4. The reactor pressure vessel processing device according to claim 3, wherein the powder is recovered by an external recovery device. In order to prevent the machining head portion from shaking due to vibrations generated during machining, a guide jig is supported on the pedestal fixed to the adjacent control rod drive mechanism housing so that the machining head portion can be rotated while being pushed from the circumferential direction. The reactor pressure vessel processing apparatus according to claim 3, further comprising a tool.

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