JP2020085608A - Reactor monitoring test piece holder, shroud head bolt, stand for shroud head bolt, and reactor monitoring test specimen installation method - Google Patents

Abstract

To provide a reactor monitoring test piece holder and the like capable of performing additional installation of test pieces without the need for construction such as welding to the reactor pressure vessel or the internal structure of the reactor.SOLUTION: The reactor monitoring test piece holder is fixed to a T-bar provided at the lower end of the shroud head bolt for fixing the shroud and shroud head, which includes: a container-shaped test piece storage part that can hermetically close the inside and contains a test piece for monitoring the health of the reactor; and a fixing mechanism disposed above the test strip storage part and fixes the test strip storage part to the lower side of the T-bar. The entire shape is configured to be inserted into a through-hole that penetrates the T-bar in the reactor.SELECTED DRAWING: Figure 1

Description

Embodiments of the present invention relate to a reactor monitoring test piece holder, a shroud head bolt, a shroud head bolt mount, and a reactor monitoring test piece installation method.

The steel material of a reactor pressure vessel of a nuclear power plant is exposed to extremely intense radiation such as neutrons and gamma rays. It is known that the mechanical properties of general steel materials deteriorate with the dose of radiation, especially the dose of neutrons. Therefore, the soundness of the nuclear reactor structural material may deteriorate as the radiation dose is accumulated. Further, since the reactor is operated at high temperature and high pressure, the reactor pressure vessel that constitutes the reactor is designed to end its life in a radiation environment while maintaining sufficient soundness.

In reality, the reactor continues to operate while actually confirming the validity of the design over time. As a method of actually confirming the validity of the design over time, the method of investigating the effects of radiation such as neutron rays using the "reactor steel material monitoring test piece" is adopted. The reactor steel monitoring test piece is housed in a reactor monitoring test piece holder installed at an appropriate location in the reactor.

In the reactor monitoring specimen holder, a dosimeter (irradiation dose measurement sample) and the like are housed in addition to the reactor steel monitoring specimen. The dosimeter is for measuring the radiation dose of radiation, especially neutrons. During the period in which the reactor is regularly shut down and the reactor is inspected (also called periodic inspection or regular inspection), the reactor steel material monitoring test is conducted from the reactor. The strip and the dosimeter are removed. As a dosimeter, one that detects neutrons has been conventionally used in most cases, and in this case, it may be referred to as a neutron dosimeter. In the following description, one or both of the reactor steel material monitoring test piece and the dosimeter are simply referred to as a test piece.

Generally, the reactor monitoring test piece holder is installed at a height equivalent to the center of the nuclear fuel core height (core height) on the inner wall of the nuclear pressure vessel. In a boiling water reactor (BWR), a method of accommodating a reactor monitoring test piece holder in a bracket installed on a reactor wall is adopted. The reactor monitoring test piece holder has a structure in which a test piece called a capsule is further enclosed.

Reactor monitoring test piece holders are installed at multiple locations on the reactor wall, and are taken out one by one after a certain period of operation, and test pieces are used to evaluate the soundness of reactor structural materials. Perform a destructive test. After performing the destructive test, the test piece may be reloaded into the furnace in order to reuse a part of the test piece after the destruction for future tests. The brackets installed on the furnace wall have been used for reloading.

On the other hand, in the BWR, in addition to the core height, an acceleration irradiation bracket and a holder for confirming the irradiation environment of the reactor immediately after the start of operation are installed at the position of the upper end of the nuclear fuel. There is no structure for reloading the bracket and holder after they are taken out from the furnace.

JP, 2002-181985, A

Conventionally, nuclear power plants have been planning a monitoring test for reactor pressure vessel steel materials, assuming 40 years from the start of service, but currently, application for extension of the operation period up to 60 years after the start of service at the nuclear power plant Recognized by. If the operation period is extended, it may be necessary to install additional test pieces.

The problem to be solved by the present invention is to provide a reactor pressure vessel, a reactor monitoring test piece holder that can carry out additional installation of test pieces without the need for construction by welding to reactor internals. Provided is a method for installing a shroud head bolt, a shroud head bolt mount, and a reactor monitoring test piece.

The reactor monitoring test piece holder of the embodiment is a reactor monitoring test piece holder fixed to a tea bar provided at a lower end portion of a shroud head bolt for fixing a shroud and a shroud head. A container-shaped test strip accommodating portion for accommodating the test specimen for monitoring the soundness of the reactor, which is capable of airtightly closing the inside, and is disposed above the test strip accommodating portion, and the test strip accommodating portion And a fixing mechanism for fixing it to the lower side of the tea bar, and the entire shape is insertable into a through hole that inserts the tea bar in the nuclear reactor.

It is a figure which shows the structure of the reactor monitoring test-piece holder and shroud head bolt which concern on 1st Embodiment, (A) is a figure which shows a side surface structure, (B) is a figure which shows a partial cross-section structure. The figure which expands and shows the part of the nuclear reactor monitoring test piece holder of FIG. It is a figure which shows the structure of the reactor monitoring test-piece holder and shroud head bolt which concern on 2nd Embodiment, (A) is a figure which shows a side surface structure, (B) is a figure which shows a partial cross-section structure. The figure which expands and shows the part of the reactor monitoring test piece holder of FIG. The figure which shows the structure of the reactor monitoring test piece holder which concerns on 3rd Embodiment. The figure which shows the structure of the temporary house of a shroud head bolt and a monitoring test piece holder. The figure which shows the cross-sectional structure of the mount for shroud head bolts. The figure which shows the whole structure of the mount for shroud head bolts. It is a figure which shows the structure of the conventional shroud head bolt, (A) is a figure which shows a side surface structure, (B) is a figure which shows a cross-sectional structure.

Hereinafter, a reactor monitoring test piece holder, a shroud head bolt, a shroud head bolt mount, and a reactor monitoring test piece installation method according to an embodiment will be described with reference to the drawings.

First, the structure of the shroud head bolt 14 conventionally used in a BWR will be described with reference to FIG.

9A and 9B are diagrams showing the configurations of the reactor monitoring test piece holder and the shroud head bolt 14, wherein FIG. 9A is a diagram showing a side configuration, and FIG. 9B is a sectional configuration seen from a direction rotated by 90°. It is a figure. Further, FIG. 9(A) shows a state in which the shroud 10 and the shroud head 6 housed in the reactor pressure vessel (not shown) are assembled, and these are fixed by the shroud head bolt 14.

As shown in FIG. 9(A), in the conventional BWR, the shroud head bolt 14 is used when fixing the shroud head 6 on the shroud 10. A plurality of shroud head bolts 14 are arranged along the circumference of the shroud 10 and the shroud head 6.

The shroud flange 9 at the upper end of the shroud 10 and the shroud head flange 8 at the lower end of the shroud head 6 are arranged to abut against each other. , 9a are provided. The tabs 8a and 9a are fixtures for the shroud head bolt 10, which are provided in pairs so as to sandwich the shroud head bolt 14 from the circumferential direction of the shroud 10. By these, the shroud head bolt 14 is restrained in the circumferential direction of the shroud 10.

As shown in FIG. 9(B), the shroud head bolt 14 includes a tubular pipe 4, and a rod 4 is provided inside the pipe 4 such that a part of the rod 4 protrudes from a lower end portion of the pipe 4. Twelve are housed. A tea bar 13 is arranged at the lower end of the rod 12, and a stud 11 is fixed to the upper part of the rod 12. The tea bar 13 protrudes horizontally in a T shape, for example, has a shape that protrudes in the horizontal direction when viewed from the direction shown in FIG. 9(B), and in this case, it is rotated by 90°. The shape viewed from the direction indicated by is substantially the same as the side surface of the rod 12.

On the other hand, as described above, the shroud head flange 8 and the shroud flange 9 are provided with the tabs 8a and 9a corresponding to the shape of the tea bar 13. Then, with the longitudinal direction of the tea bar 13 at the lower end portion of the shroud head bolt 14 aligned with the radial direction of the shroud 10, the tea bar 13 is inserted between the pair of tabs 8a and 9a, respectively. A plurality of support rings 3 are provided on the upper part of the shroud head 6, and these support rings 3 are formed with horizontally elongated holes (through holes) 3 a for inserting the shroud head bolts 14. ..

The tightening of the shroud head bolt 14 is performed by tightening between the shroud head bolt 14 and the base 7 having a large diameter whose lower surface hits the upper surfaces of the pair of claws 8a. In this case, the tea bar 13 is rotated so that its longitudinal direction is oriented in the circumferential direction of the shroud 10, so that the tea bar 13 engages with the claw 9a and has a fastening action on the shroud 10 and the shroud head 6. You can The tightening is performed by rotating the nut 1 provided on the upper end of the shroud head bolt 14 to pull up the tea bar 13 together with the stud 11 and the rod 12. In FIG. 9, reference numeral 2 denotes a head provided outside the shroud head bolt 14, and reference numeral 5 denotes a spacer provided outside the shroud head bolt 14.

(First embodiment)
Next, a reactor monitoring test piece holder 16 and the like according to the first embodiment that uses the shroud head bolt 14 having the above-described configuration will be described with reference to FIGS. In these figures, parts corresponding to those of the shroud head bolt 14 shown in FIG. 9 are designated by the same reference numerals.

1A and 1B are diagrams showing a configuration of a shroud head bolt 14 provided with a reactor monitoring test piece holder 16 according to the first embodiment. FIG. 1A is a side view showing a configuration, and FIG. It is a figure which shows the structure seen from the direction. It should be noted that FIG. 1B is a view showing the inside of the pipe 4 and the like on the outside so that the inside can be seen. As shown in FIG. 1, the shroud head bolt 14 is modified to mount the reactor monitoring specimen holder 16 and includes a tea bar 15 having a bolt hole 20 described below.

Further, FIG. 2 is an enlarged view of the portion of the reactor monitoring test piece holder 16 taken along the line AA of FIG. 1B. The horizontal cross-sectional shape of the entire outer shape of the reactor monitoring test piece holder 16 is substantially the same as the lower surface shape of the tea bar 15, and a horizontally elongated hole (through hole) 3a for inserting the tea bar 15 in the reactor is provided. The reactor monitoring test piece holder 16 can also be inserted between the pair of claws 8a and 9a and the like.

As shown in FIG. 1, the reactor monitoring test piece holder 16 according to the first embodiment is provided on the lower surface of the tea bar 15 provided at the lower end of the shroud head bolt 14. The reactor monitoring test piece holder 16 has a horizontal cross-sectional shape similar to the shape of the lower surface of the tea bar 15, extends vertically downward, and can accommodate the test piece 17 therein. It is composed of a container-shaped tubular body having.

In this embodiment, the reactor monitoring test piece holder 16 is attached to the tea bar 15 as shown in FIG. 2 by providing a plurality of bolt holes 20 in the tea bar 15 and fixing them using these bolt holes 20. This is performed by fastening the bolt 21 for use. The bolt hole 20 provided in the tea bar 15 has a hole 20a provided in the upper surface of the tea bar 15 and a through hole 20b provided at a position concentric with the hole 20a and having a smaller diameter than the hole 20a.

The hole 20a provided on the upper surface of the tea bar 15 has a polygonal shape similar to the head shape of the fixing bolt 21, and can prevent the fixing bolt 21 from being rotated when the fixing nut 22 is tightened. It is like this. The depth of the hole 20a is deeper than the height of the bolt head, and the bolt head does not protrude from the hole 20a.

A fixing mechanism for fixing to the tea bar 15 is provided on the top of the reactor monitoring test piece holder 16. That is, the fixed plate 16 a is provided on the top of the reactor monitoring test piece holder 16, and the fixed plate 16 a is provided with a bolt hole 16 b corresponding to the bolt hole 20. The fixed plate 16a may be integrated with the reactor monitoring test piece holder 16 or may be joined by welding. The tip side of the fixing bolt 21 penetrating the bolt hole 20 of the tea bar 15 is inserted into the bolt hole 16b, and the fixing nut 22 is screwed into the tip portion of the fixing bolt 21 on the lower surface side of the fixing plate 16a. .. As a result, the reactor monitoring test piece holder 16 is fixed to the lower surface of the tea bar 15 of the shroud head bolt 14. For example, tack welding is applied to the fixing nut 22 as a measure for preventing loosening and dropping.

The reactor monitoring test piece holder 16 is formed of, for example, a metal such as stainless steel into a container shape, and the inside thereof has a test piece housing portion for housing a test piece 17 for monitoring the soundness of the constituent members of the reactor. It is said that. Further, the reactor monitoring test piece holder 16 can hermetically seal the inside, and a seal gas is injected into the inside. The test pieces 17 housed in the reactor monitoring test piece holder 16 are, for example, three types, that is, a tensile test piece, a Charpy impact test piece, and a fracture toughness test piece. In addition, a dosimeter wire for measuring neutron dose and a temperature monitor wire for measuring temperature are accommodated. 2 (the same applies to FIGS. 4 and 5), a part of the outer wall of the reactor monitoring test piece holder 16 is cut away so that the test piece 17 can be seen.

When the reactor monitoring test piece holder 16 having the above configuration is applied to a BWR, the orientation of the reactor monitoring test piece holder 16 (the orientation of the test piece 17) is opposed to the neutron beam passage direction from the core, and the test The piece 17 can receive neutron irradiation that is almost uniform, and the applicability as the test piece 17 can be enhanced.

According to the reactor monitoring test piece holder 16 of the present embodiment, it is possible to additionally install the test piece without the need for welding or the like to the internal structure of the reactor.
Further, since the shroud head 6 may have the existing structure, the shroud head 6 need not be modified.
Further, the shroud head bolt 14 according to the present embodiment can take out an existing shroud head bolt and modify it outside the furnace, or can newly manufacture and use the shroud head bolt 14 according to the present embodiment. Work is unnecessary. The shroud head bolt 14 can be operated in a conventional manner.
The test piece 17 can be taken out by taking the shroud head bolt 14 out of the furnace, and it is not necessary to remotely carry out the work in the furnace.
Further, according to the configuration of the present embodiment, the reactor monitoring test piece holder 16 is not configured to support other structures, and an excessive load is not generated.
Further, when the reactor monitoring test piece holder 16 is detached from the shroud head bolt 14, no in-reactor work occurs, so that the restriction on radiation control required when performing in-reactor work is relaxed. Contribute to shortening the process.

Next, an additional construction of the reactor monitoring test piece holder 16 to the existing shroud head bolt 14 will be described. In order to install the reactor monitoring test piece holder 16 on the tea bar 15 of the shroud head bolt 14, the tea bar 13 shown in FIG. It is necessary to make the tea bar 15 to which the piece holder 16 can be attached. At the time of performing this processing, a cradle for holding the long shroud head bolt 14 is required, but since the reactor monitoring test piece holder 16 which is a heavy object is installed at the lower end, before installation in the reactor. It is necessary to avoid excessive load on the lower end of the tea bar 15 when hoisting. Therefore, a shroud head bolt mount configured to support the shroud head bolt at a position distant from the tea bar 15 is installed on the operating floor of the reactor building so that an excessive load is not applied to the tea bar 15 during processing and lifting. To do.

Further, when the reactor monitoring test piece holder 16 is taken out, the loosening prevention and the falling prevention measures of the fixing nut 22 of the fixing bolt 21 that fastens the tea bar 15 of the shroud head bolt 14 and the fixing plate 16a are canceled. Then, the fixing nut 22 is rotated so that the tack welding or the like is broken. In order to prevent the fixing nut 22 from being lost, a tray for the fixing nut 22 is prepared when removing the fixing nut 22. Further, since the fixing of the reactor monitoring test piece holder 16 is released by removing all the fixing nuts 22, a hook is used in advance to prevent the reactor monitoring test piece holder 16 from falling, and the reactor monitoring test piece holder 16 is prepared for hanging. Keep it. After the reactor monitoring test piece holder 16 is taken out, the reactor monitoring test piece holder 16 is suspended by a hook and the reactor monitoring test piece holder 16 is moved to the transfer cask as it is.

As shown in FIG. 2, the reactor monitoring test piece holder 16 is provided with a notch 18 near the middle of the axial length. The notch 18 is provided when the reactor monitoring test piece holder 16 is larger than the capacity of the transfer cask, and the reactor monitoring test piece holder 16 is formed by electrical discharge machining or the like in accordance with the notch 18. Is cut into an upper part and a lower part so that it can be divided into two parts.

With such a configuration, the reactor monitoring test piece holder 16 can be easily divided into two parts, can be disassembled without touching the internal test piece 17, and can be installed in water. Therefore, the effect of radiation exposure can be reduced. After the reactor monitoring test strip holder 16 is divided, the two divided reactor monitoring test strip holders 16 are moved to the transportation cask and transported using the transportation cask.

As described above, in the method for installing the reactor monitoring test piece of the embodiment, the step of taking out the shroud head bolt 14 from the reactor pressure vessel of the boiling water reactor and the step of accommodating the test piece outside the reactor pressure vessel are performed. Fixing the reactor monitoring test piece holder 16 to the tea bar 15 at the lower end of the shroud head bolt 14, and transferring the shroud head bolt 14 to which the reactor monitoring test piece holder 16 is fixed into the reactor pressure vessel. And a step of installing.

(Second embodiment)
Next, a second embodiment will be described with reference to FIGS. The parts corresponding to those in the first embodiment shown in FIGS. 1 and 2 are designated by the same reference numerals. 3A and 3B are diagrams showing the configuration of the shroud head bolt 14 including the reactor monitoring test piece holder 116 according to the second embodiment, where FIG. 3A is a side view and FIG. 3B is rotated by 90°. It is a figure which shows the structure seen from the direction. It should be noted that FIG. 3B shows the inside of the pipe 4 and the like so that the inside can be seen.

In the first embodiment, the reactor monitoring test piece holder 16 is configured to be fixed to the tea bar 15 of the shroud head bolt 14 by bolt fastening, but in the second embodiment, as shown in FIGS. 3 and 4, It has a structure of a reactor monitoring test piece holder 116 integrated with the tea bar 15.

The greatest advantage of the above-described structure in the second embodiment is that the rigidity of the shroud head bolt 14 and the reactor monitoring test piece holder 116 can be increased as compared with the case where bolts or the like are added. The basic structure of the reactor monitoring test piece holder 116 is the same as that of the first embodiment, but the reactor monitoring test piece holder 116 has a cross section similar to that of the tea bar 15 in the first embodiment. The plate thickness of the upper surface of the reactor monitoring test piece holder 116 is thicker than that in the first embodiment.

As described above, the second embodiment has higher rigidity than the first embodiment, and can obtain the effect of suppressing the influence of vibration due to the fluid in the furnace. Further, after the completion of the monitoring test by the test piece 17, the portion of the reactor monitoring test piece holder 116 at the lower end portion of the shroud head bolt 14 is cut by electric discharge machining or the like, so that the function as the normal shroud head bolt 14 is provided. It is possible to reuse it in the state of being.

(Third Embodiment)
Next, a third embodiment will be described with reference to FIG.
As described above, by adopting the configurations of the first and second embodiments, it becomes possible to additionally load the test piece 17 into the reactor. On the other hand, it is necessary to be prepared when an appropriate neutron dose cannot be obtained when the reactor is additionally loaded.

In this case, as shown in FIG. 5, the reactor monitoring test piece holder 216 has a structure in which the axial length of the reactor monitoring test piece holder 216 has an appropriate margin. The position can be adjusted by inserting the spacer 19 into the lower portion of the test piece 17. With such a structure, the position in the height direction of the test piece 17 in the nuclear reactor can be adjusted, and the neutron irradiation dose can be adjusted so that an appropriate neutron irradiation dose can be obtained.

The dimensional constraint of the reactor monitoring test piece holder 216 in the height direction is that the load applied to the reactor monitoring test piece holder 216 by the flow inside the reactor is allowable, and the piping in the reactor is It is to be within a range where interference with can be avoided. Therefore, the reactor monitoring test piece holder 216 can be extended in the height direction. When extending the reactor monitoring test piece holder 216 in the height direction, the reactor monitoring test piece holder 216 may interfere with the pool bottom when the shroud head 6 is installed in the equipment pool during regular inspection. It is necessary to install a temporary stand for the shroud head 6.

At the time of regular inspection, the shroud head bolt 14 is still connected to the shroud head 6 and is not generally removed. The work of removing 14 from the shroud head 6 is required.

When the shroud head bolt 14 is removed from the shroud head 6, for example, the shroud head bolt 14 is temporarily placed in the house 23 as shown in FIG. Although a person can enter the house 23, it is also possible to use a material mixed with a small amount of a shielding substance for the house 23 in order to reduce unnecessary exposure. Furthermore, in order to reduce the air dose in the house 23, it is preferable to install the discharge device 24 and the like.

In addition, a shroud head bolt mount 25 for temporarily placing the shroud head bolts 14 and the like when installing the reactor monitoring test piece holder 16 and the like to the shroud head bolts 14 is installed in the house 23.

The shroud head bolt mount 25 includes, for example, as shown in FIGS. 7 and 8, a fixing mechanism 27 and a mounting table 28 provided adjacent to the fixing mechanism 27. Note that FIG. 7 is a sectional view taken along the line BB of FIG.

The fixing mechanism 27 can fix the tea bar 13 by tightening the wing bolts 26 while sandwiching the unprocessed tea bar 13 shown in FIG. 9. Further, on the mounting table 28, the reactor monitoring test piece holder 16 for mounting on the tea bar 13 fixed to the fixing mechanism 27 is mounted. The fixing mechanism 27 and the mounting table 28 have a recess having a shape corresponding to the outer shape of the reactor monitoring test piece holder 16 and the outer shape of the tea bar 13. By installing the reactor monitoring test piece holder 16 and the tea bar 13 so as to fit in the recesses, the alignment can be easily performed.

When connecting with the fixing bolts 21, the reactor monitoring test piece holder 16 and the tea bar 13 are aligned on the shroud head bolt mount 25. After that, processing for providing the bolt hole 20 in the tea bar 13 is performed, and then, the reactor monitoring test piece holder 16 and the tea bar 13 (tea bar 13 after drilling) with the fixing bolt 21 and the fixing nut 22 are performed. 15) Fix and. After that, for example, tack welding is performed as a measure for preventing loosening and falling.

On the other hand, when the tea bar 13 is modified so as to be integrated with the tea bar 15 like the reactor monitoring test piece holder 116, the processing using the shroud head bolt mount 25 as described above is not necessary. This can be dealt with by newly preparing the shroud head bolt 14 having the reactor monitoring test piece holder 116.

Although some embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the scope equivalent thereto.

1... Nut, 2... Head, 3... Support ring, 3a... Horizontally elongated hole, 4... Pipe, 5... Spacer, 6... Shroud head, 7... Base, 8... Shroud head flange, 8a... Claw, 9... Shroud flange, 9a... Claw, 10... Shroud, 11... Stud, 12... Rod, 13... Tea bar, 14... Shroud head bolt, 15... Tea bar, 16, 116, 216... Reactor monitoring test piece holder, 16a... Fixing plate, 16b... Bolt hole, 17... Test piece, 18... Notch, 19... Spacer, 20... Bolt hole, 20a ...Hole, 20b...through hole, 21...fixing bolt, 22...fixing nut, 23...house, 24...discharging device, 25...shroud head bolt mount, 26...wing bolt, 27: fixing mechanism, 28: mounting table.

Claims (10)

A reactor monitoring test piece holder fixed to a tea bar provided at a lower end portion of a shroud head bolt for fixing a shroud and a shroud head,
A container-shaped test piece accommodating portion for accommodating the test piece for monitoring the health of the reactor, which can be hermetically closed inside.
A fixing mechanism that is disposed on the upper portion of the test strip accommodating portion and that fixes the test strip accommodating portion to the lower side of the tea bar,
Equipped with,
The reactor shape test piece holder, wherein the entire shape can be inserted into a through hole that inserts the tea bar in the reactor. The fixing mechanism is
A fixed plate disposed on the top of the test piece accommodating portion,
A plurality of bolt holes provided on the fixing plate for bolting to the tea bar,
The reactor monitoring test piece holder according to claim 1, further comprising: The reactor monitoring test piece according to claim 1 or 2, further comprising: a cutout portion provided outside the test piece storage portion for cutting the test piece storage portion into an upper portion and a lower portion. holder. The reactor monitoring test piece holder according to any one of claims 1 to 3, wherein a spacer for adjusting the height of the test piece can be housed in the test piece housing portion. . A shroud head bolt for securing a shroud and a shroud head, comprising a tea bar locked to a shroud at a lower end portion,
It is provided below the tea bar and has a container-shaped test piece accommodating portion for accommodating the test piece that can hermetically close the inside and monitors the soundness of the reactor, and the overall shape is the reactor. A shroud head bolt comprising: a reactor monitoring test piece holder that is insertable into a through hole that inserts the tea bar therein. The shroud head bolt according to claim 5, wherein the tea bar and the reactor monitoring test piece holder are fixed by bolting. The shroud head bolt according to claim 5, wherein the tea bar and the reactor monitoring test piece holder are integrally formed. A cutout for cutting the test strip containing part into an upper part and a lower part is provided outside the test strip containing part. 8. The test piece containing part according to claim 5, wherein Shroud head bolt. A shroud head bolt mount on which a shroud head bolt for fixing the shroud and the shroud head is mounted,
A tea bar fixing portion for fixing the tea bar provided at the lower end of the shroud head bolt,
A holder mounting part which is disposed adjacent to the tea bar fixing part and on which a reactor monitoring test piece holder according to any one of claims 1 to 4 is mounted on a lower end side of the tea bar.
A shroud head bolt mount characterized by comprising: Removing the shroud head bolt from the reactor pressure vessel of a boiling water reactor,
Outside the reactor pressure vessel, fixing a reactor monitoring test piece holder containing a test piece to the tea bar at the lower end of the shroud head bolt,
And a step of transferring the shroud head bolt, to which the reactor monitoring test piece holder is fixed, into the reactor pressure vessel and setting the shroud head bolt.

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