JP7039443B2 - Installation method of reactor monitoring test piece holder, shroud head bolt and shroud head bolt mount, and reactor monitoring test piece - Google Patents

Description

An embodiment of the present invention relates to a reactor monitoring test piece holder, a shroud head bolt and a shroud head bolt mount, and a method for installing the reactor monitoring test piece.

The steel material of the reactor pressure vessel of a nuclear power plant is exposed to extremely strong radiation such as neutrons and gamma rays. It is known that the mechanical properties of general steel materials deteriorate with the irradiation amount of radiation, particularly the irradiation amount of neutron rays. Therefore, as the amount of radiation is accumulated, the soundness of the reactor structural material may deteriorate. In addition, since the reactor is operated at high temperature and high pressure, the reactor pressure vessel constituting the reactor is designed to end its life while maintaining sufficient soundness under a radiation environment.

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, a method of investigating the influence of radiation such as neutron rays by using a "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 addition to the reactor steel material monitoring test piece, a dosimeter (irradiation amount measurement sample) and the like are housed in the reactor monitoring test piece holder. The dosimeter is for measuring the irradiation amount of radiation, especially neutrons, and during the period of periodic shutdown and inspection of the reactor (also called periodic inspection or regular inspection), the reactor steel monitoring test from the reactor The piece and the dosimeter are taken out. As the doji meter, a meter that detects neutrons has been used in most cases, and in this case, it may be called a neutron dodimeter. In the following description, one or both of the reactor steel 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) of the inner wall of the reactor pressure vessel. Boiling water reactors (BWRs) employ a method in which a reactor monitoring test piece holder is housed in a bracket installed on the furnace wall. It has a structure in which a test piece called a capsule is further enclosed in the reactor monitoring test piece holder.

Reactor monitoring test piece holders are installed at multiple locations on the reactor wall, and they are taken out one by one after a certain period of operation, and test pieces are used to evaluate the soundness of the 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 post-destructive test piece for future tests. When reloading, the bracket installed on the furnace wall has been used.

On the other hand, in the BWR, in addition to the core height, an accelerated irradiation bracket and a holder for confirming the irradiation environment of the reactor immediately after the start of operation are installed at the upper end of the nuclear fuel. It does not have a structure to reload the bracket and holder after they are taken out of the furnace.

Japanese Unexamined Patent Publication No. 2002-181985

In the past, at nuclear power plants, a monitoring test of reactor pressure vessel steel was planned assuming 40 years after the start of service, but now, an application is being made to extend the operation period up to 60 years after the start of service of the nuclear power plant. Is recognized by. If the operating period is extended, additional test pieces may need to be installed.

The problem to be solved by the present invention is a reactor monitoring test piece holder capable of performing additional test piece installation without requiring construction by welding to a reactor pressure vessel or a structure inside the reactor. , A platform for shroud head bolts and shroud head bolts, and a method for installing 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 the lower end of a shroud head bolt for fixing the shroud and the shroud head. A container-shaped test piece accommodating portion that can be hermetically closed inside and accommodates a test piece for monitoring the soundness of the reactor, and the test piece accommodating portion that is arranged above the test piece accommodating portion. The tea bar is provided with a fixing mechanism for fixing the tea bar to the lower side, and the overall shape can be inserted into a through hole through which the tea bar is inserted in a nuclear reactor.

It is a figure which shows the structure of the reactor monitoring test piece holder and the shroud head bolt which concerns on 1st Embodiment, (A) is the figure which shows the side surface structure, (B) is the figure which shows the partial cross-sectional structure. The figure which shows the part of the reactor monitoring test piece holder of FIG. 1 enlarged. It is a figure which shows the structure of the reactor monitoring test piece holder and the shroud head bolt which concerns on 2nd Embodiment, (A) is the figure which shows the side surface structure, (B) is the figure which shows the partial cross-sectional structure. FIG. 3 is an enlarged view showing a portion of the reactor monitoring test piece holder in 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 place house of a shroud head bolt and a monitoring test piece holder. The figure which shows the cross-sectional structure of the mount for a shroud head bolt. The figure which shows the whole structure of the mount for a shroud head bolt. It is a figure which shows the structure of the conventional shroud head bolt, (A) is the figure which shows the side surface structure, (B) is the figure which shows the cross-sectional structure.

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

First, with reference to FIG. 9, the configuration of the shroud head bolt 14 conventionally used in the BWR will be described.

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

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

The shroud flange 9 at the upper end of the shroud 10 and the shroud flange 9 and the shroud head flange 8 at the lower end of the shroud head 6 are arranged so as to be butted against each other. , 9a are provided. The claws 8a and 9a are fasteners for the shroud head bolt 10 provided in pairs so as to sandwich the shroud head bolt 14 from the circumferential direction of the shroud 10. As a result, the shroud head bolt 14 is constrained in the circumferential direction of the shroud 10.

As shown in FIG. 9B, the shroud head bolt 14 includes a tubular pipe 4, and a rod is provided inside the pipe 4 so that a part thereof protrudes from the lower end portion of the pipe 4. Twelve are housed. A tea bar 13 is disposed at the lower end of the rod 12, and a stud 11 is fixed to the upper portion of the rod 12. The tea bar 13 protrudes horizontally in a T shape, for example, has a shape protruding horizontally when viewed from the direction shown in FIG. 9 (B), and in this case, the tea bar 13 is rotated by 90 ° (A). The shape seen from the direction shown in 1 is substantially flush with 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 claws 8a and 9a according to the shape of the tea bar 13. Then, the tea bar 13 is inserted between the pair of claws 8a and 9a, respectively, with the longitudinal direction of the tea bar 13 at the lower end of the shroud head bolt 14 aligned with the radial direction of the shroud 10. A plurality of support rings 3 are provided on the upper portion of the shroud head 6, and a horizontally long hole (through hole) 3a for inserting the shroud head bolt 14 is formed in these support rings 3. ..

The shroud head bolt 14 is tightened by tightening between the base 7 having a large diameter whose lower surface corresponds to the upper surface of the pair of claws 8a and the shroud head bolt 14. In this case, the tea bar 13 engages with the claw 9a by rotating its longitudinal direction so as to face the circumferential direction of the shroud 10, and has a fastening action with respect to the shroud 10 and the shroud head 6. Can be done. Tightening is performed by pulling up the tea bar 13 together with the stud 11 and the rod 12 by rotating the nut 1 provided at the upper end of the shroud head bolt 14. In FIG. 9, reference numeral 2 indicates a head provided on the outside of the shroud head bolt 14, and reference numeral 5 indicates a spacer provided on the outside of the shroud head bolt 14.

(First Embodiment)
Next, the reactor monitoring test piece holder 16 and the like according to the first embodiment using the shroud head bolt 14 having the above configuration will be described with reference to FIGS. 1 and 2. In these figures, the parts corresponding to the shroud head bolt 14 shown in FIG. 9 are designated by the same reference numerals.

1A and 1B are views showing the 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 diagram showing a side surface configuration, and FIG. 1B is a view showing a side configuration and FIG. 1B is rotated by 90 °. It is a figure which shows the structure seen from the direction. Note that FIG. 1B is shown with the outer pipe 4 and the like as a cross section so that the inside can be seen. As shown in FIG. 1, the shroud head bolt 14 is modified to attach the reactor monitoring test piece holder 16 and includes a tea bar 15 having a bolt hole 20 described later.

Further, FIG. 2 is an enlarged view taken along the line AA of FIG. 1 (B), showing an enlarged portion of the reactor monitoring test piece holder 16. The horizontal cross-sectional shape of the 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 the horizontally elongated hole (through hole) 3a through which the tea bar 15 is inserted in the reactor is formed. The reactor monitoring test piece holder 16 can also be inserted between the pair of claws 8a and 9a.

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 downward in the vertical direction, and is a test piece accommodating portion capable of accommodating the test piece 17 inside. It is composed of a container-shaped tubular body having the above.

In the present embodiment, the reactor monitoring test piece holder 16 is attached to the tea bar 15 by providing a plurality of bolt holes 20 in the tea bar 15 and fixing them using these bolt holes 20 as shown in FIG. This is done by fastening the bolt 21. The bolt hole 20 provided in the tea bar 15 has a hole 20a provided on the upper surface of the tea bar 15 and a through hole 20b provided at a position concentric with the hole 20a and smaller than the hole diameter of 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 rotating when the fixing nut 22 is tightened. It has become like. Further, the depth of the hole 20a is deeper than the height of the bolt head, so that 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, a fixing plate 16a is provided on the top of the reactor monitoring test piece holder 16, and the fixing plate 16a is provided with a bolt hole 16b corresponding to the bolt hole 20. The fixed plate 16a may have an integral structure with the reactor monitoring test piece holder 16 or may have a structure joined by welding. The tip end 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 end 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. The fixing nut 22 is subjected to, for example, tack welding as a measure to prevent loosening and falling off.

The reactor monitoring test piece holder 16 is made of a metal such as stainless steel in a container shape, and the inside thereof is a test piece accommodating portion for accommodating a test piece 17 for monitoring the integrity of the components of the reactor. It is said that. Further, the inside of the reactor monitoring test piece holder 16 can be hermetically sealed, and the 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: a tensile test piece, a Charpy impact test piece, and a fracture toughness test piece. In addition, a dosimeter wire for measuring the neutron irradiation dose and a temperature monitor wire for measuring the temperature are housed. In FIG. 2 (the same applies to FIGS. 4 and 5), a part of the outer wall thereof is cut out so that the test piece 17 inside the reactor monitoring test piece holder 16 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 (direction of the test piece 17) faces the neutron beam passing direction from the core, and the test is performed. The piece 17 can be irradiated with neutrons that are 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, additional test pieces can be installed without requiring construction by welding to the structure inside the furnace.
Further, since the shroud head 6 may have the same existing structure, there is no need to modify the shroud head 6.
Further, the shroud head bolt 14 according to the present embodiment can be used by taking out the existing shroud head bolt and modifying it outside the furnace, or by newly manufacturing and using the shroud head bolt 14 according to the present embodiment. No work is required. The shroud head bolt 14 can be operated in the same manner as before.
Further, the work of taking out the test piece 17 may be performed by taking out the shroud head bolt 14 out of the furnace, and it is not necessary to perform the work in the furnace remotely.
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 removed from the shroud head bolt 14, no internal work is required, so that the radiation control restrictions required for the internal work are relaxed. , Contributes to process shortening.

Next, additional work 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. 9 is processed by providing the bolt hole 20 described above, and the reactor monitoring test is performed. It is necessary to make the tea bar 15 to which the one-side holder 16 can be attached. When performing this processing, a stand for holding the long shroud head bolt 14 is required, but since the heavy reactor monitoring test piece holder 16 is installed at the lower end, it is before installation in the furnace. It is necessary to avoid the generation of an excessive load on the lower end of the tea bar 15 at the time of lifting. For this reason, a shroud head bolt mount that supports the shroud head bolt at a position away from the tea bar 15 is installed on the operating floor of the reactor building so that the tea bar 15 is not overloaded during processing and lifting. do.

Further, when the reactor monitoring test piece holder 16 is taken out, the measures to prevent loosening and falling off of the fixing nut 22 of the fixing bolt 21 which fastened the tea bar 15 of the shroud head bolt 14 and the fixing plate 16a are released. Then, the fixing nut 22 is rotated so as to break the tack welding or the like. In order to prevent the fixing nut 22 from being lost, prepare a saucer for the fixing nut 22 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 preparations for hanging are prepared. Keep it. After taking out the reactor monitoring test piece holder 16, the reactor monitoring test piece holder 16 is hung with a hook and moved to the transport 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 in case the reactor monitoring test piece holder 16 is larger than the capacity of the transport cask, and the reactor monitoring test piece holder 16 is subjected to electric discharge machining or the like according to 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 underwater. Therefore, the influence of radiation exposure can be reduced. After the reactor monitoring test piece holder 16 is divided, the two divided reactor monitoring test piece holders 16 are moved to the transportation cask and transported using the transportation cask.

As described above, in the method of installing the reactor monitoring test piece of the embodiment, the step of taking out the shroud head bolt 14 from the inside of the reactor pressure vessel of the boiling water reactor and the step of accommodating the test piece outside the reactor pressure vessel. The step of fixing the reactor monitoring test piece holder 16 to the tea bar 15 at the lower end of the shroud head bolt 14 and the shroud head bolt 14 to which the reactor monitoring test piece holder 16 is fixed are transferred into the reactor pressure vessel. It has a step to install and.

(Second Embodiment)
Next, the second embodiment will be described with reference to FIGS. 3 and 4. The parts corresponding to the first embodiment shown in FIGS. 1 and 2 are designated by the same reference numerals. 3A and 3B are views showing the configuration of the shroud head bolt 14 provided with the reactor monitoring test piece holder 116 according to the second embodiment, FIG. 3A is a diagram showing a side surface configuration, and FIG. It is a figure which shows the structure seen from the direction. Note that FIG. 3B is shown with the outer pipe 4 and the like as a cross section so that the inside can be seen.

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

The greatest advantage of the second embodiment of the above structure 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 the rigidity is added by bolt fastening or the like. 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 the same cross section as 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 of the first embodiment.

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

(Third Embodiment)
Next, the third embodiment will be described with reference to FIG.
As described above, by adopting the configurations of the first and second embodiments, it is possible to additionally load the test piece 17 into the reactor. On the other hand, it is necessary to prepare for the case where an appropriate neutron irradiation amount cannot be obtained when additional loading is performed on the reactor.

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

The dimensional restrictions on the reactor monitoring test piece holder 216 with respect to the height direction are within the range in which the load applied to the reactor monitoring test piece holder 216 due to the in-reactor flow is allowed, and the in-reactor piping. It is within the range where interference can be avoided. Therefore, the reactor monitoring test piece holder 216 can be extended in the height direction. When the reactor monitoring test piece holder 216 is extended in the height direction, the reactor monitoring test piece holder 216 may interfere with the bottom of the pool when the shroud head 6 is installed in the equipment pool at the time of 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 remains connected to the shroud head 6 and is generally not removed. However, when installing the reactor monitoring test piece holder 16 or the like on the shroud head bolt 14, the shroud head bolt Work is required to remove 14 from the shroud head 6.

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 people can enter the house 23, it is possible to use a material mixed with a small amount of a shielding substance in the house 23 in order to reduce unnecessary exposure. Further, in order to reduce the air dose in the house 23, it is preferable to install a discharge device 24 or the like.

Further, in the house 23, a shroud head bolt mount 25 for temporarily placing the shroud head bolt 14 or the like is installed when the reactor monitoring test piece holder 16 or the like is attached to the shroud head bolt 14.

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

The fixing mechanism 27 can fix the tea bar 13 by tightening the wing bolt 26 in a state where the tea bar 13 before processing shown in FIG. 9 is sandwiched. Further, a reactor monitoring test piece holder 16 for attaching to the tea bar 13 fixed to the fixing mechanism 27 is placed on the mounting table 28. 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 into this recess, the alignment can be easily performed.

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

On the other hand, when the tea bar 13 is modified to be integrated with the tea bar 15 like the reactor monitoring test piece holder 116, processing using the shroud head bolt mount 25 as described above is not necessary. This can be handled by newly preparing a shroud head bolt 14 having a 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 embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are also included in the scope of the invention described in the claims and the equivalent scope thereof.

1 ... Nut, 2 ... Head, 3 ... Support ring, 3a ... Horizontal hole, 4 ... Pipe, 5 ... Spacer, 6 ... Shroud head, 7 ... Base, 8 ... Shroud head flange, 8a ... claws, 9 ... shroud flanges, 9a ... claws, 10 ... shrouds, 11 ... studs, 12 ... rods, 13 ... tea bars, 14 ... shroud head bolts, 15 ... tea bars, 16,116,216 ... Reactor monitoring test piece holder, 16a ... Fixed 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 …… Discharge device, 25 …… Shroud head bolt mount, 26 …… Flange bolt, 27 ... fixing mechanism, 28 ... mounting stand.

Claims (10)

A reactor monitoring test piece holder fixed to a tea bar provided at the lower end of a shroud head bolt for fixing a shroud and a shroud head.
A container-shaped test piece accommodating part that can be airtightly closed and accommodates test pieces for monitoring the integrity of the reactor,
A fixing mechanism disposed on the upper part of the test piece accommodating portion and for fixing the test piece accommodating portion to the lower side of the tea bar,
Equipped with
A reactor monitoring test piece holder characterized in that the overall shape is such that it can be inserted into a through hole through which the tea bar is inserted in the reactor. The fixing mechanism is
A fixing plate arranged at the top of the test piece accommodating portion and
A plurality of bolt holes provided in the fixing plate for bolting to the tea bar, and
The reactor monitoring test piece holder according to claim 1, wherein the nuclear reactor monitoring test piece holder is provided. The reactor monitoring test piece according to claim 1 or 2, wherein a notch for cutting the test piece accommodating portion into an upper portion and a lower portion is provided on the outside of the test piece accommodating 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 accommodating portion. .. A shroud head bolt having a tea bar locked to the shroud at the lower end and for fixing the shroud and the shroud head.
It is provided below the tea bar and has a container-shaped test piece accommodating part that can be airtightly closed and accommodates test pieces for monitoring the soundness of the reactor, and the overall shape is the reactor. A shroud head bolt having a reactor monitoring test piece holder that can be inserted into a through hole through which the tea bar is inserted. 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 configured. The invention according to any one of claims 5 to 7, wherein a notch for cutting the test piece accommodating portion into an upper portion and a lower portion is provided on the outside of the test piece accommodating portion. Shroud head bolt. A shroud head bolt mount on which a shroud head bolt for fixing the shroud and the shroud head is placed.
A tea bar fixing portion for fixing the tea bar provided at the lower end of the shroud head bolt, and a tea bar fixing portion.
A holder mounting portion which is arranged adjacent to the tea bar fixing portion and on which the reactor monitoring test piece holder according to any one of claims 1 to 4 is mounted on the lower end side of the tea bar.
A mount for shroud head bolts, which is characterized by being equipped with. The step of removing the shroud head bolt from the reactor pressure vessel of a boiling water reactor,
A step of fixing the reactor monitoring test piece holder containing the test piece to the tea bar at the lower end of the shroud head bolt outside the reactor pressure vessel.
A method for installing a reactor monitoring test piece, comprising: a step of transferring and installing the shroud head bolt to which the reactor monitoring test piece holder is fixed into the reactor pressure vessel.

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