Method for closing leaking parts of reactor pressure vessels and structure for closing leaking parts

Abstract

To facilitate separation of fuel debris from a cut-off material and reduce the amount of waste without increasing the amount of cut-off materials.SOLUTION: There is provided a leakage part blocking method for a reactor pressure vessel which blocks a leakage point (opening) at the bottom of the reactor pressure vessel by using a cut-off material. The method uses a camera mounted on a remote device to confirm the shape of the leakage point from the outside of the reactor pressure vessel, when the shape of the leakage point is known, operates the remote device to insert and fix a plug, patch, or mortar being the cut-off material from the outside of the reactor pressure vessel to the leakage point to block the leakage point, when the shape of the leakage point is unknown but the position of the leakage point can be identified, operates the remote device to insert a bag containing fluid to be solidified with accumulation and expansion being the cut-off material from the outside of the reactor pressure vessel to the leakage point, and then, blocks the leakage point with the bag in which the fluid is accumulated and expanded.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method and structure for closing a leaking part in a reactor pressure vessel, and more particularly to a method and structure for closing a leaking part in a reactor pressure vessel that are suitable for closing a leaking part in the reactor pressure vessel by accessing the bottom of the reactor pressure vessel from outside. [Background technology]

[0002] If a boiling water reactor nuclear power plant were to lose all power due to a major earthquake or tsunami, the water supply to the reactor would stop, which could lead to a meltdown of the fuel core and partial damage to the reactor pressure vessel.Even in the unlikely event of a severe accident in which the fuel core melts and the reactor pressure vessel is partially damaged, the reactor pressure vessel needs to be supplied with cooling water from an external source in order to steadily cool the decay heat of the fuel core.

[0003] At this time, if the reactor pressure vessel is partially damaged, there is a risk that the cooling water supplied to the reactor pressure vessel will leak from the damaged area.

[0004] For this reason, in order to remove the fuel debris while the reactor pressure vessel is filled with cooling water, technology is being considered to access the leaking point (opening) in the reactor pressure vessel from the outside of the bottom of the reactor pressure vessel and stop or minimize the water leak.

[0005] For example, Patent Document 1 describes providing an injection hole in a pipe connected to the inside of a reactor pressure vessel, and injecting a water-stopping material through this injection hole.

[0006] Specifically, it describes how water-stopping material (for example, iron powder, boron carbonite, or cement) is injected into the reactor core using either the CS system water injection piping of the high-pressure water injection system or the low-pressure water injection system that is directly connected to the reactor core, thereby sealing holes and cracks that have appeared in the bottom of the reactor pressure vessel without opening the top lid of the reactor containment vessel or reactor pressure vessel, and stopping or minimizing water leakage from the reactor pressure vessel. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-235009 Summary of the Invention [Problem to be solved by the invention]

[0008] However, in the technology of injecting waterstop material into the reactor pressure vessel described in the above-mentioned Patent Document 1, since the waterstop material is injected into the reactor pressure vessel, the waterstop material accumulates on the reactor internals, increasing the amount of material, and when the waterstop material is sprayed, the waterstop material accumulates over the entire reactor bottom, which may increase the amount of material to be injected. Also, when fuel debris and waterstop material are mixed together, it becomes difficult to separate the two, which increases the amount of waste material.

[0009] The present invention has been made in consideration of the above points, and an object of the present invention is to provide a method for closing a leak in a reactor pressure vessel and a structure for closing the leak, which does not increase the amount of water-stopping material, makes it easy to separate fuel debris from the water-stopping material, and reduces the amount of waste material. [Means for solving the problem]

[0010] In order to achieve the above object, the method for closing a leaking part in a reactor pressure vessel of the present invention is a method for closing a leaking part (opening) at the bottom of the reactor pressure vessel using a water-stopping material, the method comprising: confirming the shape of the leaking part (opening) from outside the reactor pressure vessel with a camera mounted on a remote device; and, if the shape of the leaking part (opening) is known, operating the remote device to insert and fix the water-stopping material, i.e., a plug, patch, or mortar, into the leaking part (opening) from outside the reactor pressure vessel, thereby closing the leaking part (opening); and, if the shape of the leaking part (opening) is unknown but the position of the leaking part (opening) can be identified, operating the remote device to insert and fix the water-stopping material, i.e., a plug, patch, or mortar. body A bag containing a fluid that expands and solidifies is inserted into the leaking location (opening) from the outside of the reactor pressure vessel, and then the fluid is body The expanded bag is characterized in that it closes the water leakage point (opening).

[0011] In order to achieve the above object, the present invention provides a method for closing a leaking part in a reactor pressure vessel, which uses a water-stopping material to close a water-leaking point (opening) at the bottom of the reactor pressure vessel, and includes a first step of inserting a remote device into the reactor containment vessel and extending the remote device into the support skirt of the reactor pressure vessel; a second step of identifying the water-leaking point (opening) at the bottom of the reactor pressure vessel from the outside of the reactor pressure vessel using the remote device; and a second step of identifying the water-leaking point (opening) at the bottom of the reactor pressure vessel from the outside of the reactor pressure vessel, inside the support skirt of the reactor pressure vessel, using the remote device to a third step of removing rust from the water leakage point (opening) and processing the water leakage point (opening) to fit the shape of the water stop material that will close the water leakage point (opening); and after the third step, if the shape of the water leakage point (opening) is known, the remote device is operated to insert and fix the water stop material, which is a plug, patch, or mortar, into the water leakage point (opening) from the outside of the reactor pressure vessel, thereby closing the water leakage point (opening); and if the shape of the water leakage point (opening) is unknown but the position of the water leakage point (opening) can be identified, the remote device is operated to insert and fix the water stop material, which is a plug, patch, or mortar, into the water leakage point (opening). bodyA bag containing a fluid that expands and solidifies is inserted into the leaking location (opening) from the outside of the reactor pressure vessel, and then the fluid is body and a fourth step of closing the water leakage point (opening) with the expanded bag.

[0012] In order to achieve the above object, the leaking portion closure structure for a reactor pressure vessel of the present invention is a leaking portion closure structure for a reactor pressure vessel in which a water leaking point (opening) at the bottom of the reactor pressure vessel is closed with a water-stopping material, before It is a waterproof material body The fluid in the bag expands and solidifies. body The leakage point (opening) is blocked by the expansion. The fluid that expands in volume and solidifies is urethane foam, and the bag is made of aramid. After the urethane foam solidifies, mortar is injected into the reactor pressure vessel using a hose attached to the bag, and the leaking point (opening) is closed. It is characterized by: [Effects of the Invention]

[0013] According to the present invention, the amount of waterstop material does not increase, fuel debris can be easily separated from the waterstop material, and the amount of waste can be reduced. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a diagram showing a schematic structure of a boiling water nuclear power plant to which the method for closing a leaking part in a reactor pressure vessel and the structure for closing the leaking part of the present invention are applied. [Figure 2] 1A and 1B are diagrams showing the closing operation in the method for closing a leaking part in a reactor pressure vessel of the present invention when the shape of the leaking point (opening) is known. [Figure 3] 10A and 10B are diagrams showing the closing operation in the method for closing a leaking part in a reactor pressure vessel of the present invention when the shape of the leaking part (opening) is unknown but the position of the leaking part (opening) is identified. DETAILED DESCRIPTION OF THE INVENTION

[0015] The method and structure for closing a leaking portion of a reactor pressure vessel according to the present invention will be described below with reference to the illustrated embodiments. In each drawing, the same reference numerals are used for the same components. [Example]

[0016] FIG. 1 shows a schematic structure of a boiling water nuclear power plant to which the method for closing a leak in a reactor pressure vessel and the structure for closing the leak in the reactor pressure vessel of the present invention are applied.

[0017] As shown in the figure, the boiling water nuclear power plant in this embodiment includes a reactor and a reactor containment vessel 2. The reactor containment vessel 2 is installed in a reactor building 1, and a top cover 2A is attached to the upper end and sealed. The reactor containment vessel 2 has a dry well 9 formed therein and an annular pressure suppression chamber 24 in which a suppression pool filled with cooling water 23 is formed. One end of a vent passage connected to the dry well 9 is immersed in the cooling water 23 for the suppression pool in the suppression chamber 24. The suppression chamber 24 is located in an annular torus chamber 26 formed in the reactor building 1.

[0018] The nuclear reactor includes a reactor pressure vessel 3 configured with an upper lid 3A attached, a core 27 loaded with a plurality of fuel assemblies containing nuclear fuel material, a steam separator (not shown), a steam dryer (not shown), etc. The core 27, steam separator, and steam dryer are arranged inside the reactor pressure vessel 3. Each fuel assembly loaded inside the core 27 has its lower end supported by a core support plate 28 and its upper end held by an upper grid plate 29. The steam separator is arranged above the upper grid plate 29, and the steam dryer is arranged above the steam separator.

[0019] A plurality of control rod guide tubes 30 are arranged below the core support plate 28. A control rod (not shown), which is inserted and removed between the fuel assemblies in the core 27 to control the reactor power, is arranged in each control rod guide tube 30. A plurality of control rod drive mechanism housings 31 are attached to the bottom head of the reactor pressure vessel 3. A control rod drive mechanism (not shown) is installed in each control rod drive mechanism housing 31 and is connected to the control rod in the control rod guide tube 30.

[0020] The reactor pressure vessel 3 is installed on a cylindrical pedestal 5 that is placed on a concrete mat 32 that is placed at the bottom of the reactor containment vessel 2. A cylindrical gamma ray shield 33 is installed at the upper end of the pedestal 5 and surrounds the reactor pressure vessel 3. A pedestal opening 34 is formed in the pedestal 5, and communicates between the dry well 9 in the reactor containment vessel 2 and an internal space 35 formed in the pedestal 5. A plurality of control rod drive mechanism housings 31 extend from the bottom head of the reactor pressure vessel 3 toward the internal space 35.

[0021] A cylindrical concrete biological shield 6, which is part of the reactor building 1, surrounds the reactor containment vessel 2. An access passage with an airlock door is provided to allow workers to enter the reactor containment vessel 2 during maintenance and inspections that are carried out after the operation of the boiling water reactor plant is shut down, and this access passage penetrates the biological shield 6 and the reactor containment vessel 2. In addition to the access passage, a control rod drive mechanism hatch 36 and an equipment hatch are also provided that penetrate the biological shield 6 and the reactor containment vessel 2. The control rod drive mechanism hatch 36 extends toward the side wall of the reactor building 1 that faces the radioactive waste treatment building 37.

[0022] The access passage is established by opening the airlock door, and the equipment hatch and control rod drive mechanism hatch 36 are opened to connect the area 38 outside the reactor containment vessel 2 within the reactor building 1 with the dry well 9 inside the reactor containment vessel 2. When the boiling water nuclear plant is in operation, the airlock door and these hatches are closed.

[0023] An operating floor 39 is formed above the reactor containment vessel 2 within the reactor building 1. A fuel storage pool 40 is formed and surrounded by the operating floor 39, and is filled with cooling water. A plurality of spent fuel assemblies removed from the reactor core 27 are stored in the cooling water within the fuel storage pool 40.

[0024] The reactor building 1 has a square cross section and four side walls. A radioactive waste treatment building 37 is located adjacent to the reactor building 1 and extends parallel to one side wall of the reactor building 1. A turbine building (not shown) is located adjacent to the other side wall of the reactor building 1, perpendicular to the side wall adjacent to the radioactive waste treatment building 37.

[0025] In this embodiment, as shown in FIG. 2, when a water leak (opening) 3a at the bottom of the reactor pressure vessel 3 is closed using a water stop material (e.g., a plug 8) (L1 in FIG. 2 is the size of the water leak (opening) 3a), the shape of the water leak (opening) 3a is confirmed from outside the reactor pressure vessel 3 using a camera (not shown) mounted on a remote device (e.g., a robot 7). If the shape of the water leak (opening) 3a is known (a hole or a crack is known, for example, whether it is a round hole or a square hole), the robot 7 is operated to insert a water stop material such as a plug 8, a patch (not shown), or mortar (not shown) into the water leak (opening) 3a from outside the reactor pressure vessel 3 and fix it with welding 10, thereby closing the water leak (opening) 3a (L1 in FIG. 2 is the size of the water leak (opening) 3a, and the water leak (opening) 3a is closed using a water stop material (e.g., a plug 8) that matches the size L1 of the water leak (opening) 3a).

[0026] On the other hand, if the shape of the water leakage point (opening) 3a is unknown but the position of the water leakage point (opening) 3a can be identified (for example, a part of the hole is visible, but the whole hole is hidden behind an object), as shown in Figure 3, ,B Operate Bot 7 to create a waterproof material. body A fluid that expands and solidifies (e.g., foam The bag 11 containing the urethane 13) is inserted into the leaking point (opening) 3a from the outside of the reactor pressure vessel 3, and then foam Urethane 13 body The expanded bag 11 closes the leaking point (opening) 3a (L2 in FIG. 3 is the size of the leaking point (opening) 3a, and the size L2 of the leaking point (opening) 3a is closed). body A fluid that expands and solidifies (e.g., foam The bag 11 is closed using urethane 13).

[0027] The plug 8 or patch, which is the water-stopping material described above, is fixed to the water leakage point (opening) 3a of the reactor pressure vessel 3 by welding, and the mortar is fixed to the water leakage point (opening) 3a of the reactor pressure vessel 3 by injecting it through a hose inserted into the inside of the reactor pressure vessel 3.

[0028] As mentioned above, the body The fluid that expands and solidifies is foam The bag 11 is made of aramid, and the robot 7 is used to insert the aramid bag 11 into the leaking location (opening) 3a. foam Urethane 13 is injected and this foam After the urethane 13 has solidified, mortar 14 is injected into the reactor pressure vessel 3 using a hose 12 attached to the bag 11 to close the water leak point (opening) 3a.

[0029] The mortar 14 injected into the reactor pressure vessel 3 using the hose 12 attached to the bag 11 is arranged so as to cover the part of the bag 11 located inside the reactor pressure vessel 3.

[0030] Furthermore, in this embodiment, if the shape of the water leakage point (opening) 3a is unknown but the position of the water leakage point (opening) 3a can be identified, and if the bag 11 and mortar 14 cannot withstand the water pressure when water is injected into the reactor pressure vessel 3, a strength member that will serve as a reinforcing material after being inserted into the reactor pressure vessel 3 can be enclosed in the bag 11 in advance, or a support material can be inserted from the outside of the reactor pressure vessel 3 to reinforce it after the water-stopping material is installed.

[0031] Furthermore, the method for closing a leaking part in the reactor pressure vessel 3 of this embodiment will be specifically described. The method for closing a leaking part in the reactor pressure vessel 3 of this embodiment is to move a remote device (robot 7) to the reactor containment vessel. 2a first step in which the robot 7 is inserted into the support skirt of the reactor pressure vessel 3 and penetrates the robot 7 into the inside of the support skirt of the reactor pressure vessel 3; a second step in which the robot 7 identifies the leaking point (opening) 3a at the bottom of the reactor pressure vessel 3 from the outside of the reactor pressure vessel 3; a third step in which, inside the support skirt of the reactor pressure vessel 3, the robot 7 removes rust from the leaking point (opening) 3a that has opened in the bottom head of the reactor pressure vessel 3 when there is no water, using a sander or the like, and processes the leaking point (opening) 3a with a laser or the like to fit the shape of a water-stopping material that will close the leaking point (opening) 3a; and after the third step, if the shape of the leaking point (opening) 3a is known (if a hole or crack is known, for example, In the case where it is known whether the hole is a round hole or a square hole), the robot 7 is operated to insert a water-stopping material, such as a plug 8, a patch (not shown), or mortar (not shown), into the water-leakage point (opening) 3a from the outside of the reactor pressure vessel 3 and fix it by welding 10, thereby closing the water-leakage point (opening) 3a (L1 in FIG. 2 is the size of the water-leakage point (opening) 3a, and the water-leakage point (opening) 3a is closed using a water-stopping material (for example, a plug 8) that fits the size L1). In the case where the shape of the water-leakage point (opening) 3a is unknown but the position of the water-leakage point (opening) 3a can be identified (for example, a part of the hole can be seen, but the whole hole cannot be seen because it is hidden behind an object), as shown in FIG. ,B Operate Bot 7 to create a waterproof material. body A fluid that expands and solidifies (e.g., foam The bag 11 containing the urethane 13) is inserted into the leaking point (opening) 3a from the outside of the reactor pressure vessel 3, and then foam Urethane 13 body A fourth step is carried out in which the expanded bag 11 closes the water leakage point (opening) 3a.

[0032] In the method for closing a leaking part in a reactor pressure vessel 3 according to the present embodiment described above, the plug 8 or patch is fixed to the leaking part (opening) 3a of the reactor pressure vessel 8 by welding, and the mortar is fixed to the leaking part (opening) 3a of the reactor pressure vessel 3 by injecting it through a hose inserted into the inside of the reactor pressure vessel 3.

[0033] In addition, body The fluid that expands and solidifies is foamThe bag 11 is made of aramid and is made of urethane 13. The robot 7 is used to insert the aramid bag 11 into the leaking location (opening) 3a. foam Urethane 13 is injected and this foam After the urethane 13 has solidified, mortar 14 is injected into the reactor pressure vessel 3 using a hose attached to the bag 11 to close the leak point (opening) 3a. The mortar 14 injected into the reactor pressure vessel 3 using a hose 12 attached to the bag 11 is arranged so as to cover the part of the bag 11 located inside the reactor pressure vessel 3.

[0034] In this embodiment, the robot 7 is remotely controlled by an operator in a control room while watching a monitor.

[0035] The leaking portion closing structure of the reactor pressure vessel 3 performed by the leaking portion closing method of the reactor pressure vessel 3 of this embodiment is such that the leaking portion (opening) 3a is closed by fixing a plug or patch or mortar, which is a water-stopping material, to the leaking portion (opening) 3a, or body The growth expands and solidifies foam The release of aramid bags 11 containing urethane 13 foam Urethane 13 body The leakage point (opening) 3a is blocked by the expansion.

[0036] The plug 8 or patch is fixed to the leaking location (opening) 3a of the reactor pressure vessel 3 by welding 10, and the mortar is fixed to the leaking location (opening) 3a of the reactor pressure vessel 3 by injecting it through a hose inserted into the inside of the reactor pressure vessel 3. At this time, the mortar 14 injected into the inside of the reactor pressure vessel 3 using a hose 12 attached to an aramid bag 11 is arranged so as to cover the part of the aramid bag located inside the reactor pressure vessel 3.

[0037] In addition, in the leak portion closure structure of the reactor pressure vessel 3 in this embodiment, the strength members that become reinforcing members after being inserted into the reactor pressure vessel 3 are toThe waterproof material is enclosed in an aramid bag 11 or reinforced with a support material inserted from the outside of the reactor pressure vessel 3.

[0038] According to this embodiment, watertight work can be performed without opening the reactor pressure vessel 3 and regardless of the internal condition of the reactor pressure vessel 3, and the amount of watertight material used can be reduced compared to watertight work performed from inside the reactor pressure vessel 3, and there is no need to change the shape of the watertight material for each water leak point (opening) 3a in the reactor pressure vessel 3. Therefore, in this embodiment, the amount of watertight material does not increase, and it becomes easier to separate the fuel debris and the watertight material, making it possible to reduce the amount of waste.

[0039] The present invention is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations. [Explanation of symbols]

[0040] 1... reactor building, 2... reactor containment vessel, 2A... reactor containment vessel top cover, 3... reactor pressure vessel, 3a... reactor pressure vessel vessel Leakage point (opening), 3A...Top lid of reactor pressure vessel 、5 ...pedestal, 6...biological shield, 7...robot, 8...plug, 9...dry well, 10...welding, 11...bag, 12...hose, 13...fire foamUrethane, 14...mortar, 23...cooling water, 24...pressure suppression chamber, 26...torus chamber, 27...core, 28...core support plate, 29...upper grid plate, 30...control rod guide tube, 31...control rod drive mechanism housing, 32...concrete mat, 33...gamma ray shield, 34...pedestal opening, 35...inner space, 36...control rod drive mechanism hatch, 37...radioactive waste treatment building, 38...area outside the reactor containment vessel, 39...operating floor, 40...fuel storage pool.

Claims

1. A method for closing a leaking portion of a reactor pressure vessel, which closes a water-leaking portion (opening) at the bottom of the reactor pressure vessel using a water-stopping material, comprising: The shape of the water leak point (opening) is confirmed from outside the reactor pressure vessel using a camera mounted on a remote device, and when the shape of the water leak point (opening) is known, the remote device is operated to insert and fix the water stop material, which is a plug, patch, or mortar, into the water leak point (opening) from outside the reactor pressure vessel, thereby closing the water leak point (opening); A method for closing a leak in a reactor pressure vessel, characterized in that, when the shape of the leaking point (opening) is unknown but the position of the leaking point (opening) can be identified, the remote device is operated to insert a bag containing the water-stopping material, a fluid that expands in volume and solidifies, into the leaking point (opening) from outside the reactor pressure vessel, and then the bag containing the fluid that has expanded in volume is used to close the leaking point (opening).

2. 2. The method for closing a leak in a reactor pressure vessel according to claim 1, comprising: a plug or patch being fixed to the water leaking location (opening) of the reactor pressure vessel by welding, and a mortar being fixed to the water leaking location (opening) of the reactor pressure vessel by injecting the mortar through a hose inserted into the inside of the reactor pressure vessel.

3. 2. The method for closing a leak in a reactor pressure vessel according to claim 1, comprising: a remote device for inserting the aramid bag from the leaking location (opening), and then injecting the urethane foam into the aramid bag; and after the urethane foam has solidified, injecting the mortar into the reactor pressure vessel using a hose attached to the bag, thereby closing the leaking location (opening).

4. 4. The method for closing a leak in a reactor pressure vessel according to claim 3, comprising:

1. A method for closing a leak in a reactor pressure vessel, wherein the mortar injected into the reactor pressure vessel using a hose attached to the bag is arranged so as to cover a portion of the bag located inside the reactor pressure vessel.

5. 5. The method for closing a leak in a reactor pressure vessel according to claim 4, comprising: A method for closing a leaking part in a reactor pressure vessel, characterized in that, when the shape of the leaking part (opening) is unknown but the position of the leaking part (opening) can be identified, and when the bag and mortar are not sufficient to withstand the differential pressure when water is injected into the reactor pressure vessel, a strength member that will serve as a reinforcing material after being inserted into the reactor pressure vessel is enclosed in the bag in advance, or after the waterstop material is installed, a support material is inserted from the outside of the reactor pressure vessel to reinforce it.

6. A method for closing a leaking portion of a reactor pressure vessel, which closes a water-leaking portion (opening) at the bottom of the reactor pressure vessel using a water-stopping material, comprising: a first step of inserting a remote device into the reactor containment vessel and extending the remote device into a support skirt of the reactor pressure vessel; a second step of identifying the leak location (opening) at the bottom of the reactor pressure vessel from outside the reactor pressure vessel using the remote device; a third step in which, inside the support skirt of the reactor pressure vessel, the remote device removes rust from the water leakage point (opening) in the bottom head of the reactor pressure vessel when there is no water, and processes the water leakage point (opening) to fit the shape of the water-stopping material that closes the water leakage point (opening); After the third step, if the shape of the water leakage point (opening) is known, the remote device is operated to insert and fix the water-stopping material, such as a plug, patch, or mortar, into the water leakage point (opening) from the outside of the reactor pressure vessel, thereby closing the water leakage point (opening); and a fourth step of operating the remote device to insert a bag containing the water-stopping material, which is a fluid that expands in volume and solidifies, into the water-stopping point (opening) from outside the reactor pressure vessel when the shape of the water-stopping point (opening) is unknown but the position of the water-stopping point (opening) can be identified, and then closing the water-stopping point (opening) with the bag containing the fluid that has expanded in volume.

7. 7. A method for closing a leak in a reactor pressure vessel according to claim 6, comprising: a plug or patch being fixed to the water leaking location (opening) of the reactor pressure vessel by welding, and a mortar being fixed to the water leaking location (opening) of the reactor pressure vessel by injecting the mortar through a hose inserted into the inside of the reactor pressure vessel.

8. 7. A method for closing a leak in a reactor pressure vessel according to claim 6, comprising: a remote device for inserting the aramid bag from the leaking location (opening), and then injecting the urethane foam into the aramid bag; and after the urethane foam has solidified, injecting the mortar into the reactor pressure vessel using a hose attached to the bag, thereby closing the leaking location (opening).

9. 9. A method for closing a leak in a reactor pressure vessel according to claim 8, comprising:

1. A method for closing a leak in a reactor pressure vessel, wherein the mortar injected into the reactor pressure vessel using a hose attached to the bag is arranged so as to cover a portion of the bag located inside the reactor pressure vessel.

10. A leak closure structure for a reactor pressure vessel, in which a water leak point (opening) at the bottom of the reactor pressure vessel is closed by a water stop material, The fluid in the bag containing the water-stopping material, which expands in volume and solidifies, expands in volume, thereby closing the leaking portion (opening), a closure structure for a leaking part in a reactor pressure vessel, wherein the fluid that expands in volume and solidifies is urethane foam, and the bag is made of aramid, and when the urethane foam solidifies, mortar is injected into the inside of the reactor pressure vessel using a hose attached to the bag to close the leaking part (opening).

11. The reactor pressure vessel leak closure structure according to claim 10, 1. A reactor pressure vessel leak closure structure, comprising: a bag for sealing a leak portion of a reactor pressure vessel; a hose for attaching the bag to the bag; and a mortar for injecting the mortar into the reactor pressure vessel using the hose attached to the bag, the mortar being arranged to cover the portion of the bag located inside the reactor pressure vessel.

12. The reactor pressure vessel leak closure structure according to claim 11, A structure for closing a leaking part of a reactor pressure vessel, characterized in that a strength member that will become a reinforcing material after being inserted into the inside of the reactor pressure vessel is contained in the bag in advance, or the water-stopping material is reinforced with a support material inserted from the outside of the reactor pressure vessel.

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