Methods for dismantling a nuclear reactor vessel

Abstract

To ensure the smooth dismantling of the reactor vessel. [Solution] A method for dismantling a reactor vessel, comprising a reactor vessel body and an insulating material covering the reactor vessel body from the outer periphery, the method comprising: a step of disconnecting the connection between the reactor vessel body and the insulating material; a step of moving the reactor vessel body and the insulating material relative to each other vertically; and a step of cutting the portion that is no longer covered by the insulating material due to the relative movement.

Description

Technical Field

[0001] This disclosure relates to a method for disassembling a reactor vessel.

Background Art

[0002] Patent Document 1 describes a method for disassembling a nuclear power plant for which decommissioning measures have been determined. In the disassembling method of this Patent Document 1, the in-vessel structures inside the reactor vessel are disassembled in the water stored in the working pool, and the disassembled in-vessel structures are carried out from the working pool.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in a nuclear power plant as described in Patent Document 1, after taking out the in-vessel structures from the reactor vessel and disassembling them, the reactor vessel from which the in-vessel structures have been taken out is also disassembled. The reactor vessel has a bottomed cylindrical reactor vessel body and a heat insulating material that covers the reactor vessel body from the outside. When disassembling the reactor vessel inside the reactor containment vessel, due to the work space, it may be difficult to remove only the heat insulating material from the reactor vessel body and remove it before cutting and disassembling the reactor vessel body. In this case, there is a problem that the heat insulating material interferes when cutting the reactor vessel body, and the disassembly work of the reactor vessel cannot be carried out smoothly.

[0005] This disclosure has been made in view of the above circumstances, and provides a method for disassembling a reactor vessel that can smoothly perform the disassembly work of the reactor vessel.

Means for Solving the Problems

[0006] To solve the above problems, the method for dismantling a reactor vessel according to this disclosure involves covering the reactor vessel body and the reactor vessel body from the outer periphery. cylindrical A method for dismantling a reactor vessel having an insulating material, comprising the steps of disconnecting the connection between the reactor vessel body and the insulating material, The aforementioned heat-insulating material is in a cylindrical shape. The process includes the steps of moving the reactor vessel body and the heat-insulating material vertically relative to each other, and cutting off the portion that is no longer covered by the heat-insulating material due to the relative movement. [Effects of the Invention]

[0007] According to this disclosure, the dismantling of the reactor vessel can be carried out smoothly. [Brief explanation of the drawing]

[0008] [Figure 1] This is a longitudinal cross-sectional view showing a pressurized water reactor 1, which is the reactor to be dismantled according to this embodiment. [Figure 2] This is a schematic diagram showing how a pressurized water reactor according to this embodiment is arranged inside the reactor building. [Figure 3] This is a schematic diagram showing an enlarged view of the area near the boundary between the upper and lower container bodies. [Figure 4] This is a flowchart illustrating the method for dismantling the reactor vessel in this embodiment. [Figure 5] This is a schematic diagram showing the reactor vessel in the state immediately before the dismantling method described above is implemented. [Figure 6] This figure shows the reactor vessel supported from below by a support structure. [Figure 7] This figure shows the state in which vertical movement wires are fixed to the lower insulation section of the reactor vessel, which is supported by the above-mentioned frame. [Figure 8] This diagram shows the lower insulation section moved downwards and the upper container removed. [Figure 9] This figure shows the lower insulation section in the state when it has been moved upward using a wire for vertical movement. [Figure 10] This diagram shows the torso insulation section being supported from below. [Figure 11]This diagram shows the reactor vessel body after it has been moved upward and the upper vessel body has been removed. [Figure 12] This figure shows the process of moving the reactor vessel body and the insulation material up and down relative to each other in a modified example of the second embodiment. [Modes for carrying out the invention]

[0009] The following describes embodiments for implementing the reactor vessel dismantling method according to this disclosure, with reference to the attached drawings. However, this disclosure is not limited to these embodiments.

[0010] <First Embodiment> (nuclear reactor) Figure 1 is a longitudinal cross-sectional view showing a pressurized water reactor 1, which is the reactor to be dismantled according to this embodiment. The reactor illustrated in this embodiment is a pressurized water reactor (PWR) that uses light water as a reactor coolant and neutron moderator, creating high-temperature, high-pressure water that does not boil throughout the entire core, sending this high-temperature, high-pressure water to a steam generator to generate steam through heat exchange, and sending this steam to a turbine generator to generate electricity.

[0011] Figure 2 is a schematic diagram showing how a pressurized water reactor according to this embodiment is arranged inside the reactor building. As shown in FIG. 2, the pressurized water reactor 1 is disposed in a reactor building pool 100 provided within a reactor building (not shown). A space capable of storing cooling water (water) is formed within the reactor building pool 100. The reactor building pool 100 of the present embodiment has, as a space, a first cavity 110 in which the pressurized water reactor 1 is disposed, and a second cavity 120 disposed adjacent to the first cavity 110. The first cavity 110 has a first floor surface 111 on which an operator can walk. The second cavity 120 has a second floor surface 121 that is recessed from the first floor surface 111. That is, the second floor surface 121 is located below the first floor surface 111 in the vertical direction (up and down direction) Dv. Thereby, the second cavity 120 is formed as a space that is recessed below the first cavity 110 in the vertical direction Dv.

[0012] As shown in FIGS. 1 and 2, the pressurized water reactor 1 of the present embodiment includes a reactor vessel 2, an upper core structure 5, and a lower core structure 6. (Reactor vessel) The reactor vessel 2 has a reactor vessel main body 21, a reactor vessel head 22 (upper mirror), and a heat insulating material 25 so that in-vessel structures can be inserted therein. The reactor vessel 2 is disposed inside a hole 130 formed to be recessed downward from the first floor surface 111. In other words, the reactor vessel 2 is installed inside a hole 130 formed in concrete. The reactor vessel 2 is disposed in a state where a part thereof (specifically, the reactor vessel head 22) protrudes from the first floor surface 111. In FIG. 1, the illustration of the heat insulating material 25 is omitted.

[0013] The reactor vessel main body 21 can be opened at the upper part by removing the reactor vessel head 22. The reactor vessel main body 21 integrally has a body part 211 and a lower closing part 212. The body part 211 is formed in a cylindrical shape extending in the vertical direction Dv. The lower closing part 212 closes the lower end of the body part 211. The lower closing part 212 is a lower mirror having a hemispherical shape.

[0014] At the upper part of the reactor vessel main body 21, an inlet nozzle 23 (inlet pipe support) for supplying light water (coolant) as primary cooling water (water) and an outlet nozzle 24 (outlet pipe support) for discharging light water are formed. Further, the reactor vessel main body 21 has an injection nozzle (injection pipe support), not shown, separately from the inlet nozzle 23 and the outlet nozzle 24.

[0015] The reactor vessel head 22 is attached to the upper part of the reactor vessel main body 21. The reactor vessel head 22 is fixedly attached to the reactor vessel main body 21 by a plurality of stud bolts and nuts (not shown) so as to be openable and closable.

[0016] As shown in FIG. 2, the heat insulating material 25 covers the reactor vessel main body 21 from the outer peripheral side. The heat insulating material 25 has a function of suppressing the transfer of the thermal energy of the reactor vessel main body 21 to the gas or concrete in the reactor building. The heat insulating material 25 exemplified in the present embodiment has a body heat insulating portion 251 and a lower mirror heat insulating portion 252. The body heat insulating portion 251 is arranged so as to cover the outer peripheral side of the reactor vessel main body 21. The lower mirror heat insulating portion 252 is arranged so as to cover the lower closing portion 212 of the reactor vessel main body 21 from below. Although the case where the heat insulating material 25 includes the body heat insulating portion 251 and the lower mirror heat insulating portion 252 has been described, the present invention is not limited to this configuration. For example, the lower mirror heat insulating portion 252 may be omitted and the lower closing portion 212 may be covered by the body heat insulating portion 251. In this case, the body heat insulating portion 251 may be extended to below the lower closing portion 212 and the lower edge of the body heat insulating portion 251 may be closed. Further, when the lower closing portion 212 is covered by the body heat insulating portion 251 in this manner, the second ring member 26b of the body heat insulating portion 251 may be arranged below the lower closing portion 212.

[0017] The body heat insulating portion 251 has a frame 25a and a heat insulating material main body 25b. The frame 25a supports the heat insulating material main body 25b. The frame 25a has a ring member 26 formed in a circular shape covering the entire circumference of the reactor vessel main body 21 and a vertical member 27 extending in a direction intersecting the ring member 26. The frame 25a and the body portion 211 of the reactor vessel main body 21 are arranged with a slight gap in the radial direction of the body portion 211.

[0018] In this embodiment, the frame 25a includes a ring member 26, which is a first ring member 26a located above the inlet nozzle 23 and the outlet nozzle 24, and a second ring member 26b located near the boundary between the body portion 211 and the lower closing portion 212. The vertical members 27 are provided so as to extend across the first ring member 26a and the second ring member 26b. Multiple vertical members 27 are provided at intervals in the circumferential direction of the body portion 211.

[0019] The first ring member 26a is supported from below by the inlet nozzle 23 and the outlet nozzle 24. This restricts the downward movement of the first ring member 26a. The frame 25a below the first ring member 26a is supported by the first ring member 26a. In other words, the vertical member 27 and the second ring member 26b are each provided to hang from the first ring member 26a. To put it another way, the vertical member 27 and the second ring member 26b are not fixed to the body 211 below the inlet nozzle 23 and the outlet nozzle 24.

[0020] The insulation material body 25b is fixed to the frame 25a. In other words, the insulation material body 25b is supported by the frame 25a. The insulation material body 25b can be formed by arranging multiple panels, for example, a box-shaped panel with a metal film laminated inside. In the insulation material body 25b of this embodiment, multiple panels are stacked on a second ring member 26b, for example, and arranged without gaps in the vertical and circumferential directions to form a cylindrical shape. However, the insulation material body 25b is not limited to being formed by arranging multiple panels.

[0021] Figure 3 is a schematic diagram showing an enlarged view of the area near the boundary between the upper and lower container bodies. As shown in Figures 1 and 3, the body portion 211 of the reactor vessel body 21 in this embodiment comprises an upper vessel body 21U to which the inlet nozzle 23 and outlet nozzle 24 are connected, and a lower vessel body 21L that is located below the upper vessel body 21U and has a smaller outer diameter than the upper vessel body 21U. The upper vessel body 21U in this embodiment has a tapered portion 21R at its lower edge that gradually decreases in diameter downwards, and the lower vessel body 21L extends downwards from the lower edge of the tapered portion 21R. Note that the frame 25a is not shown in Figure 3.

[0022] As shown in Figures 2 and 3, the body insulation section 251 of this embodiment comprises an upper insulation section 251U for insulating the upper vessel body 21U and a lower insulation section 251L for insulating the lower vessel body 21L. These upper insulation section 251U and lower insulation section 251L are cylindrical in shape, with inner diameters corresponding to the outer diameter of the reactor vessel body 21 at the respective locations to be insulated. In other words, the inner diameter of the lower insulation section 251L is smaller than the inner diameter of the upper insulation section 251U. The upper insulation section 251U and the lower insulation section 251L of this embodiment have equivalent thicknesses. Therefore, the outer diameter of the upper insulation section 251U is larger than the outer diameter of the lower insulation section 251L.

[0023] Here, a hole 130 for housing the reactor vessel 2 is formed in the first cavity 110 of the reactor building pool 100 described above. The hole 130 is formed to be recessed downward from the first floor surface 111. As shown in Figure 3, the hole 130 in this embodiment has an upper housing section 130U that houses the upper vessel body 21U and the upper insulation section 251U, and a lower housing section 130L that houses the lower vessel body 21L and the lower insulation section 251L. The lower housing section 130L has an inner diameter slightly larger than the outer diameter of the lower insulation section 251L and forms a cylindrical space that extends in the vertical direction.

[0024] Similarly, the upper housing section 130U has an inner diameter slightly larger than the outer diameter of the upper insulation section 251U and forms a cylindrical space that extends vertically. This is because the upper housing section 130U is formed by pouring concrete around the upper insulation section 251U and hardening it while the lower vessel body 21L and the lower insulation section 251L are housed in the lower housing section 130L. As shown in Figure 2, in this embodiment, the upper housing section 130U is formed such that the reactor vessel lid 22 protrudes above the first floor surface 111. Below the lower housing section 130L, an in-core chest chamber 141 is formed for routing conduit tubes 140 and the like that extending from through-pipes such as instrumentation pipes that penetrate the lower closure section 212 of the reactor vessel 2. The in-core chest chamber 141 has a floor surface 142 that faces the lower opening of the lower housing section 130L. In this embodiment, the inner chests chamber 141 extends horizontally from vertically below the hole 130.

[0025] As shown in Figure 2, the lower mirror insulation section 252 comprises a lower frame (not shown) that covers the lower closure section 212 and an insulation material body 252b. The lower mirror insulation section 252 is hemispherical in shape along the outer circumferential surface of the lower closure section 212. In this embodiment, the lower mirror insulation section 252 has holes (not shown) for allowing through-piping such as instrumentation pipes that penetrate the lower closure section 212 to pass through. The lower mirror insulation section 252 is connected to the second ring member 26b of the frame 25a. In this embodiment, the case in which the lower closure section 212 and the lower mirror insulation section 252 protrude from the lower housing section 130L into the in-core chest chamber 141 is illustrated. The lower mirror insulation section 252 is formed by multiple panels, similar to the body insulation section 251. For example, the lower mirror insulation section 252 can be removed from the body insulation section 251 by removing the panel of the insulation material body 252b from the lower frame (not shown) of the lower mirror insulation section 252 and releasing the connection between the lower frame (not shown) and the frame 25a. Note that the lower mirror insulation section 252 is not limited to being formed by arranging multiple panels. Also, the lower closing section 212 and the lower mirror insulation section 252 are not limited to protruding from the lower housing section 130L into the inner chest chamber 141. For example, the lower closing section 212 and the lower mirror insulation section 252 may be positioned above the lower edge of the lower housing section 130L.

[0026] (Upper core structure) As shown in Figure 1, the upper core structure 5 is located inside the reactor vessel 2. The upper core structure 5 can be removed from the reactor vessel body 21 by moving it upward in the vertical direction Dv relative to the reactor vessel body 21. The upper core structure 5 in this embodiment has an upper core plate 51, an upper core support plate 52, an upper core support column 53, a guide tube 55, and a water level gauge support pipe (not shown). However, the upper core structure 5 does not have only the structure described above. The upper core structure 5 has other configurations not shown, such as a mixer, thermocouple lead-out pipes, and reinforcing beams.

[0027] (Lower core structure) The lower core structure 6 is located inside the reactor vessel 2. Many of the components of the lower core structure 6 are positioned vertically Dv below the upper core structure 5. The lower core structure 6 can be removed from the reactor vessel body 21 by moving it vertically Dv above the reactor vessel body 21. The lower core structure 6 is separable from the upper core structure 5 inside the reactor vessel body 21.

[0028] (Method for dismantling the reactor vessel) The following describes a method for dismantling the reactor vessel 2 according to the first embodiment of this disclosure. Figure 4 is a flowchart showing the method for dismantling the reactor vessel in this embodiment. As shown in Figure 4, the method S10 for dismantling the reactor vessel 2 in this embodiment includes at least the steps of: S11 for disconnecting the connection between the reactor vessel body and the insulation material; S12 for moving the reactor vessel body and the insulation material relative to each other vertically; and S13 for cutting the portion that is no longer covered by the insulation material.

[0029] Figure 5 is a schematic diagram showing the reactor vessel in the state immediately before the above-described method of dismantling the reactor vessel is implemented. Here, before carrying out the above-described dismantling method S10 for the reactor vessel 2, preparations for dismantling the reactor vessel 2 are made. This involves removing the reactor vessel lid 22 of the reactor vessel 2 and removing and dismantling the upper core structure 5 and lower core structure 6 from inside the reactor vessel body 21 by an appropriate method. Furthermore, as shown in Figure 5, a shielding lid 28 is attached to the reactor vessel body 21 to close the reactor vessel body 21, and the concrete of the upper containment section 130U surrounding the upper vessel body 21U and the upper insulation section 251U is removed. At this time, concrete in a predetermined range is removed around the entire circumference of the reactor vessel body 21 in the circumferential direction. This creates a working space 30 around the upper vessel body 21U and the upper insulation section 251U. In this embodiment, the reactor vessel body 21 is supported by the surrounding concrete via the inlet nozzle 23 and the outlet nozzle 24 even before the working space 30 is formed. With the formation of the above-mentioned workspace 30, the concrete of the floor surface 30a of the workspace 30 supports the inlet nozzle 23 and outlet nozzle 24 of the reactor vessel body 21 from below. Support members (not shown), such as wooden beams, may be placed between the inlet nozzle 23 and outlet nozzle 24 and the floor surface 30a.

[0030] In this embodiment, after the work space 30 is formed, various pipes connected to the upper container body 21U, such as the inlet nozzle 23 and outlet nozzle 24, are cut, and the insulation material body 25b of the upper insulation section 251U is removed from the frame 25a. An example of a cutting position for the various pipes connected to the upper container body 21U is a position that allows the inlet nozzle 23 and outlet nozzle 24 to remain supported on the floor surface 30a. Furthermore, the timing for removing the insulation material body 25b of the upper insulation section 251U may be at an appropriate time, as long as the upper insulation section 251U does not hinder the dismantling work.

[0031] On the other hand, in this embodiment, the lower end insulation section 252 of the insulation material 25 is removed, leaving the body insulation section 251. Furthermore, in this embodiment, the through-pipe (not shown) such as an instrumentation pipe or the conduit tube 140 that penetrates the lower closure section 212 is cut and removed. Then, a plug is placed over the remaining through-pipe in the lower closure section 212 to prevent water leakage. Then, water is filled into the reactor vessel body 21 up to a position just below the inlet nozzle 23 and the outlet nozzle 24. Examples of methods for filling the reactor vessel body 21 with water include, for example, installing pipes, hoses, etc. that penetrate the shielding cover 28 and supplying water into the reactor vessel body 21 via the pipes, hoses, etc., or, for example, installing an opening / closing hatch (not shown) on the shielding cover 28 and supplying water into the reactor vessel body 21 via this opening / closing hatch.

[0032] Figure 6 shows the reactor vessel supported from below by a support structure. In step S11, which involves disconnecting the connection between the reactor vessel body and the insulation material, the connection between the insulation material 25 and the reactor vessel body 21 is disconnected. As shown in Figure 6, in step S11 of this embodiment, first, a lifting wire 29 is placed over the top of the reactor vessel body 21 and lifted by a crane. The reactor vessel body 21 of this embodiment has stud bolt holes (not shown) for closing the shielding cover 28. Therefore, as a method for lifting the reactor vessel body 21 with the crane, one example is to make effective use of the stud bolt holes by installing eye bolts or the like in the stud bolt holes, and then placing the lifting wire 29 over the eye bolts or the like and lifting it by a crane.

[0033] Furthermore, in step S11 of this embodiment, a support frame 31 capable of supporting the lower closure portion 212 of the reactor vessel body 21 from below is installed in the in-core chest chamber 141. Then, the reactor vessel body 21 is placed on the support frame 31. As a result, the reactor vessel body 21 is positioned higher than it was before it was lifted by the lifting wire 29. In other words, the reactor vessel body 21 transitions from a state where the inlet nozzle 23 and outlet nozzle 24 are supported from below to a state where the lower closure portion 212 is supported from below by the support frame 31.

[0034] Figure 7 shows the state in which the vertical movement wire is fixed to the lower insulation section of the reactor vessel, which is supported by the above-mentioned frame. As shown in Figure 7, in step S11, with the reactor vessel body 21 supported on the frame 31, the first end of the vertical movement wire 32 is further fixed to the lower insulation section 251L. Specifically, the first end of the vertical movement wire 32 is fixed to the upper part of the frame 25a that constitutes the lower insulation section 251L. The second end of the vertical movement wire 32 is connected to a device such as a winch that can wind up and feed out the vertical movement wire 32. In this embodiment, the vertical movement wire 32 is guided by a plurality of pulleys 33 provided in the work space 30 or the like.

[0035] In step S11 described above, with the first end of the vertical movement wire 32 fixed to the lower insulation section 251L, the frame 25a of the upper insulation section 251U is further separated from the frame 25a of the lower insulation section 251L. Specifically, the first ring member 26a and vertical member 27 constituting the frame 25a of the upper insulation section 251U are separated from the second ring member 26b and vertical member 27 constituting the frame 25a of the lower insulation section 251L. At this time, the first ring member 26a and vertical member 27 constituting the upper insulation section 251U may be removed from the reactor vessel body 21. In this embodiment, the first ring member 26a and vertical member 27 constituting the upper insulation section 251U are removed and taken away from the reactor vessel body 21. As a result, the connection between the reactor vessel body 21 and the lower insulation section 251L, which remains as insulation material 25, is severed, and the lower insulation section 251L is supported only by the vertical movement wire 32.

[0036] In step S12, which involves moving the reactor vessel body and the insulation material vertically relative to each other, the reactor vessel body 21 and the insulation material 25 are moved vertically relative to each other. In step S12 of this embodiment, the reactor vessel body 21 is moved downward and the insulation material 25 is moved upward relative to each other. Specifically, in this embodiment, the lower vessel body 21L and the lower insulation section 251L are moved vertically relative to each other. More specifically, in this embodiment, the lower insulation section 251L is moved upward relative to the lower vessel body 21L and removed without changing the vertical position of the reactor vessel body 21.

[0037] Figure 8 shows the state after the lower insulation section has been moved downwards and the upper container has been removed. As shown in Figure 8, in step S12 of this embodiment, the upper vessel body 21U, which has a larger diameter than the lower insulation section 251L, is cut and removed in order to allow the lower insulation section 251L to be moved upward relative to the lower vessel body 21L. To do this, first, a vertical movement wire 32 is fed in, and the lower insulation section 251L, supported by the vertical movement wire 32, is moved downward along the reactor vessel body 21. In this state, the upper vessel body 21U is cut by the cutting device 40 and gradually removed from top to bottom. As described above, with the removal of the upper vessel body 21U, which has an outer diameter larger than the inner diameter of the lower insulation section 251L, it becomes possible to move the lower insulation section 251L upward relative to the lower vessel body 21L.

[0038] Here, the cutting device 40 can be one that has a first disc D1 capable of cutting the reactor vessel body 21 in the vertical direction and a second disc D2 capable of cutting the reactor vessel body 21 in the horizontal direction. The cutting device 40 can divide the body portion 211 of the reactor vessel body 21 into multiple cut pieces by cutting the body portion 211 in the vertical direction and the circumferential direction, respectively. The cutting device 40 is inserted into the reactor vessel body 21 from above, for example, and cuts are made from the inside of the reactor vessel body 21. The inlet nozzle 23 and outlet nozzle 24 may be moved to, for example, the first floor surface 111, before cutting to create multiple cut pieces.

[0039] Figure 9 shows the lower insulation section in a state where it has been moved upward using a wire for vertical movement. As shown in Figure 9, in step S12, the vertical movement wire 32 is further wound up to move the lower insulation section 251L to the work space 30. Then, the lifting wire 29 is fixed to the lower insulation section 251L, and the vertical movement wire 32 is detached from the lower insulation section 251L. The lifting wire 29 and the lower insulation section 251L are then lifted upwards by a crane and removed. In other words, the lower insulation section 251L is moved upwards relative to the lower container body 21L. As a result, the lower insulation section 251L is no longer positioned around the lower container body 21L housed in the hole 130. The removed lower insulation section 251L is moved to, for example, the first floor surface 111, and multiple panels are removed from the frame 25a, and the frame 25a is cut into multiple smaller pieces.

[0040] In step S13, which involves cutting the portion no longer covered by the insulation material, the portion of the reactor vessel body 21 that is no longer covered by the insulation material 25 due to the relative movement in step S12 is cut and removed. In other words, in this embodiment, since the lower insulation portion 251L has moved upward and been removed, the lower vessel body 21L, which is housed in the lower housing portion 130L of the hole 130 (see Figure 3) and is no longer covered by the lower insulation portion 251L, is cut and removed using the cutting device 40 in the same way as the upper vessel body 21U.

[0041] In this embodiment, similar to the upper container body 21U, the lower container body 21L is cut from top to bottom, dividing it into multiple pieces which are then gradually removed. At this time, since the lower container body 21L is filled with water, the cutting work is carried out while lowering the water level so that the water surface is just below the cutting position. After the body portion 211 is removed, the lower closure portion 212 will remain inside the hole 130. However, the lower closure portion 212 may be cut after being removed above the hole 130, for example, rather than being cut inside the hole 130. The multiple pieces are then placed in a waste container for disposing of radioactive materials and transported out of the reactor building.

[0042] (Effects and Benefits) In the reactor vessel dismantling method S10 of the first embodiment described above, the connection between the reactor vessel body 21 and the insulation material 25 is disconnected, the reactor vessel body 21 and the insulation material 25 are moved relative to each other vertically, and the portion of the reactor vessel body 21 that is no longer covered by the insulation material 25 due to this relative movement is cut. This makes it possible to prevent the insulation material 25 from being positioned on the outer circumference of the reactor vessel body 21 at the cutting point, even if it is difficult to remove the insulation material 25 from the outer circumference of the reactor vessel body 21 while the reactor vessel 2 is housed in the hole 130. Therefore, it is possible to prevent problems such as the cutting disc of the disc saw interfering with the insulation material 25 when cutting the reactor vessel body 21. Consequently, the dismantling work of the reactor vessel 2 can be carried out smoothly.

[0043] Furthermore, in the reactor vessel dismantling method S10 of the first embodiment described above, in step S12, in which the reactor vessel body and the insulation material are moved relative to each other vertically, the insulation material 25 is moved upward relative to the reactor vessel body 21. This makes it possible to avoid positioning the insulation material 25 on the outer circumference of the reactor vessel body 21 at the cutting point, even if there is insufficient space to move the insulation material 25 relative to the reactor vessel body 21 below it.

[0044] Furthermore, in the reactor vessel dismantling method S10 of the first embodiment described above, the connection between the upper insulation section 251U and the lower insulation section 251L is disconnected, and after removing the upper vessel body 21U and the upper insulation section 251U, the lower vessel body 21L and the lower insulation section 251L are moved relative to each other vertically, and the portion of the lower vessel body 21L that is no longer covered by the lower insulation section 251L due to the relative movement is cut off. By removing the upper vessel body 21U, which has a larger diameter than the lower vessel body 21L, and the upper insulation section 251U that covers the upper vessel body 21U first, it becomes possible to displace the lower insulation section 251L upward relative to the lower vessel body 21L. Therefore, even if sufficient space cannot be secured below the reactor vessel body 21 to move the lower insulation section 251L relative to it, it is possible to avoid positioning the lower insulation section 251L on the outer circumference of the lower vessel body 21L at the cutting point. Thus, the cutting work of the lower vessel body 21L can be carried out smoothly.

[0045] Furthermore, in the reactor vessel dismantling method S10 of the first embodiment described above, in step S12 in which the reactor vessel body and the insulation material are moved relative to each other vertically, when the upper vessel body 21U and the upper insulation section 251U covering the upper vessel body 21U are removed first, the lower insulation section 251L is moved downward by a wire for vertical movement. This prevents the lower insulation section 251L from getting in the way when removing the upper container body 21U and the upper insulation section 251U. Therefore, the removal of the upper container body 21U and the upper insulation section 251U can be carried out smoothly.

[0046] <Modification of the first embodiment> In step 12 of the first embodiment described above, the case in which the lower insulation section 251L is lifted by a crane and moved to the first floor surface 111 before the dismantling work is performed was explained. However, the method of dismantling the lower insulation section 251L is not limited to the method of dismantling the lower insulation section 251L exemplified in the first embodiment above.

[0047] For example, while the insulation material 25 is being removed upward from the hole 130, that is, while the lower insulation section 251L is being lifted upward from the hole 130 by a crane, a worker positioned in the work space 30 above the hole 130 may remove the panel of the insulation material body 25b that is exposed upward from the hole 130 from the frame 25a. This eliminates the need to erect a large scaffold on the first floor surface 111, etc., for workers to remove the panels of the insulation material body 25b, as is the case when removing the panels of the insulation material body 25b on the first floor surface 111, etc. Furthermore, on the first floor surface 111, etc., only the frame 25a, which is lighter and has less volume compared to the lower insulation section 251L, needs to be dismantled, so the work can be done using a simple workbench, reducing the burden on the workers performing the dismantling work.

[0048] Furthermore, if a worker positioned in the work space 30 removes a panel of the insulation material body 25b from the frame 25a as described above, even if the panel of the insulation material body 25b unintentionally collapses, the direction in which the panel falls is limited to the direction of the hole 130, allowing the worker to be positioned so as not to interfere with the falling object. Therefore, worker safety can be improved.

[0049] Furthermore, as described above, when the lower insulation section 251L is lifted by a crane and moved upward through the hole 130, if workers positioned in the work space 30 remove the panels from the frame 25a during this process, the primary shielding made of concrete surrounding the hole 130 can be utilized. Therefore, the exposure effects on workers positioned in the work space 30 from the reactor vessel body 21 located inside the hole 130 and the lower insulation section 251L outside the dismantling area can be reduced.

[0050] Furthermore, if the lower insulation section 251L is dismantled (the insulation material 25 is dismantled) without the relative movement described above, workers will be strongly affected by radiation exposure from the lower vessel body 21L of the fuel region. However, by moving the lower insulation section 251L relative to the lower vessel body 21L (reactor vessel body 21) as described above before dismantling the lower insulation section 251L, the lower vessel body 21L can be dismantled at a distance from the high-radiation areas of the reactor vessel body 21, thereby reducing the radiation exposure to workers dismantling the lower insulation section 251L.

[0051] Furthermore, by moving (separating) the lower insulation section 251L and the lower container body 21L relative to each other and dismantling the lower container body 21L and the lower insulation section 251L, it is possible to sort and apply cutting methods suitable for the dismantling of the lower container body 21L and the lower insulation section 251L respectively, thus enabling a more reliable dismantling method.

[0052] Furthermore, since the panels of the insulation material body 25b can be dismantled from the top relative to the frame 25a of the lower insulation section 251L, the risk of the panels of the insulation material body 25b collapsing can be reduced, as is the case when dismantling the panels of the insulation material body 25b stacked on top of the second ring member 26b from the bottom.

[0053] Furthermore, if the insulation material 25 and the reactor vessel body 21 are not moved (separated) during dismantling, it is conceivable to dismantle the reactor vessel body 21 and the insulation material 25 as a single unit. However, the inside of the hole 130 formed in the concrete is narrow and workability is poor. Also, when transporting the insulation material 25 and the reactor vessel body 21 to a wide area such as the first cavity 110 or the second cavity 120, there are concerns about exposure to radiation to the public and workers. However, by moving them relative to each other before dismantling as described above, workability can be improved and concerns about radiation exposure can be eliminated.

[0054] <Second Embodiment> Next, a method for dismantling a reactor vessel according to the second embodiment of this disclosure will be described. The method for dismantling a reactor vessel in this second embodiment differs from the method for dismantling a reactor vessel in the first embodiment described above in that the insulation material is moved downward relative to the reactor vessel. For this reason, Figures 1 to 5 will be used with reference, and the same parts as in the first embodiment described above will be denoted by the same reference numerals, and redundant explanations will be omitted.

[0055] (Nuclear reactor and reactor vessel) As shown in Figures 1 to 3, the pressurized water reactor 1 in the second embodiment has the same configuration as the pressurized water reactor 1 in the first embodiment described above, and comprises a reactor vessel 2, a control rod drive device 3, an upper core structure 5, and a lower core structure 6. The reactor vessel 2 comprises a reactor vessel body 21, a reactor vessel lid 22, and insulation material 25.

[0056] (Method for dismantling the reactor vessel) As shown in Figure 4, the dismantling method S20 for the reactor vessel 2 in the second embodiment includes at least the steps of: S21 of disconnecting the connection between the reactor vessel body and the insulation material; S22 of moving the reactor vessel body and the insulation material relative to each other vertically; and S23 of cutting the portion that is no longer covered by the insulation material.

[0057] In the second embodiment's method for dismantling the reactor vessel 2, S20, preparations for dismantling the reactor vessel 2 are made first, similar to the first embodiment. Specifically, the upper core structure 5 and the lower core structure 6 are removed from inside the reactor vessel body 21 to form a work space 30, and the insulation material body 25b of the upper insulation section 251U is removed. Furthermore, the lower end insulation section 252 is removed from the insulation material 25, leaving the body insulation section 251, and the through-pipes (not shown) such as instrumentation pipes or conduit tubes 140 that penetrate the lower closure section 212 are cut and removed, and the remaining through-pipes in the lower closure section 212 are plugged to prevent water leakage. Then, water is filled into the reactor vessel body 21 up to a position just below the inlet nozzle 23 and the outlet nozzle 24.

[0058] Figure 10 shows the body insulation section being supported from below. In step S21, which disconnects the connection between the reactor vessel body and the insulation material, the connection between the insulation material 25 and the reactor vessel body 21 is disconnected. As shown in Figure 10, in step S21 of the second embodiment, first, the insulation material support part 35 supports the body insulation part 251 of the insulation material 25 from below. The insulation material support part 35 supports only the body insulation part 251 and does not support the reactor vessel body 21. The insulation material support part 35 is installed so as to be sandwiched between the floor surface 142 of the in-core chest chamber 141 and the body insulation part 251. By installing this insulation material support part 35, the downward displacement of the body insulation part 251 (lower insulation part 251L) is restricted.

[0059] In step S21 described above, with the downward displacement of the lower insulation section 251L restricted, the frame 25a of the upper insulation section 251U is further separated from the frame 25a of the lower insulation section 251L, similar to step S11 of the first embodiment. At this time, the first ring member 26a and the vertical member 27 constituting the upper insulation section 251U may be removed from the reactor vessel body 21. As a result, the connection between the reactor vessel body 21 and the lower insulation section 251L remaining around the reactor vessel body 21 as insulation material 25 is severed, and the lower insulation section 251L is supported only by the insulation material support section 35.

[0060] Figure 11 shows the state after the reactor vessel body has been moved upward and the upper vessel body 21U has been removed. In step S22, which involves moving the reactor vessel body and the insulation material vertically relative to each other, the reactor vessel body 21 and the insulation material 25 are moved vertically relative to each other. In step S22 of the second embodiment, the reactor vessel body 21 is moved upward and the insulation material 25 is moved downward relative to each other. Specifically, the lower vessel body 21L and the lower insulation section 251L are moved vertically relative to each other. More specifically, the lower vessel body 21L (body section 211) is moved upward relative to the lower insulation section 251L without changing the vertical position of the lower insulation section 251L.

[0061] In this second embodiment, the reactor vessel body 21 is moved upward using the vessel gripping device 45. The vessel gripping device 45 has a columnar portion 45a that extends vertically and is displaceable vertically, and a gripping portion 45b that extends radially outward from the columnar portion 45a and is capable of gripping the reactor vessel body 21 from the inside. The vessel gripping device 45 is able to stably lift the reactor vessel body 21 while gripping it with these columnar portion 45a and gripping portion 45b. In this embodiment, the vessel gripping device 45 grips the lowest part of the body portion 211 from the inside and moves the reactor vessel body 21 upward.

[0062] As shown in Figure 11, in step S23, which involves cutting the portion no longer covered by the insulation material, the portion of the reactor vessel body 21 that is no longer covered by the insulation material 25 is cut. In this step S23, a cutting device 50 is installed on the floor surface 30a of the work space 30. The cutting device 50 has a cutting disc that can cut the body 211 of the reactor vessel body 21 from the outer circumference. The cutting device 50 in this embodiment has a cutting disc that can cut the reactor vessel body 21 in the vertical direction and a cutting disc that can cut the reactor vessel in the horizontal direction. The cutting device 50 cuts the portion of the body 211 of the reactor vessel body 21 that is exposed above the floor surface 30a, thereby dividing the body 211 of the reactor vessel body 21 into multiple cut pieces, similar to the first embodiment. Then, the upward movement of the lower vessel body 21L by the vessel gripping device 45 and the cutting by the cutting device 50 are repeated. As a result, the body section 211 is gradually divided into cut pieces from top to bottom. Here, since the lower container body 21L is filled with water as in the first embodiment, the cutting operation by the cutting device 50 is performed while lowering the water level so that the water level is just below the cutting position. The lower closure section 212 may be cut after being removed from the work space 30, for example, rather than being cut in the work space 30. The divided cut pieces are placed in a waste container for disposing of radioactive materials and then transported out of the reactor building.

[0063] In the reactor vessel dismantling method S20 of this second embodiment, after step S23, the insulation material 25 is removed upward from the hole 130 and dismantled. At this time, similar to the modification of the first embodiment, while the insulation material 25 is being removed upward from the hole 130, a worker positioned in the work space 30 above the hole 130 may sequentially remove the insulation material body 25b that is exposed upward from the hole 130 from the frame 25a. In this way, similar to the modification of the first embodiment, the insulation material body 25b can be removed from the frame 25a without having to erect scaffolding to perform the work of removing the insulation material body 25b from the frame 25a. Furthermore, since the frame 25a from which the insulation material body 25b has been removed is easy to move, the frame 25a can be moved to any space where dismantling work can be easily performed before dismantling. Therefore, the workability related to the dismantling of the insulation material 25 can be improved. Furthermore, when removing the insulation material body 25b from the frame 25a, only a portion of the insulation material body 25b, which is the radiation source, is exposed through the hole 130. Therefore, by utilizing temporary shielding around the hole 130, the impact of radiation exposure on workers dismantling the insulation material 25 can be reduced.

[0064] (Effects and Benefits) In the reactor vessel dismantling method S20 of the second embodiment described above, the reactor vessel body 21 and the insulation material 25 are moved relative to each other vertically so that the reactor vessel body 21 is positioned above and the insulation material 25 is positioned below, and the portion of the reactor vessel body 21 that is no longer covered by the insulation material 25 due to the relative movement is cut. As a result, similar to the first embodiment, the insulation material 25 is not located on the outer circumference of the reactor vessel body 21 that has moved above the insulation material 25. Therefore, by cutting the reactor vessel body 21 that has moved above the insulation material 25, it is possible to prevent problems such as the cutting disc of the disc saw interfering with the insulation material 25. Thus, the dismantling work of the reactor vessel 2 can be carried out smoothly.

[0065] Furthermore, in the reactor vessel dismantling method S20 of the second embodiment described above, the reactor vessel body 21 is moved upward relative to the insulation material 25. This allows the reactor vessel body 21 to be gradually moved upward, exposing it above the insulation material 25. Therefore, even if there is insufficient space to move the insulation material 25 relative to the reactor vessel body 21, the insulation material 25 can be kept away from the outer periphery of the reactor vessel body 21. Consequently, when cutting the reactor vessel body 21, interference with the insulation material 25 by the cutting disc of the disc saw is prevented, and the dismantling of the reactor vessel 2 can be carried out smoothly.

[0066] Furthermore, in the reactor vessel dismantling method S20 of the second embodiment described above, the lower insulation section 251L is supported from below to disconnect the connection between the upper insulation section 251U and the lower insulation section 251L. Then, the lower vessel body 21L is moved upward relative to the lower insulation section 251L, and in the work space 30, the portion of the lower vessel body 21L that is no longer covered by the lower insulation section 251L is cut. This allows the lower vessel body 21L to be moved upward without changing the position of the lower insulation section 251L in the vertical direction. Therefore, even if there is insufficient space to move the lower insulation section 251L relative to the reactor vessel body 21, for example, the lower insulation section 251L can be positioned so as not to be located on the outer circumference of the lower vessel body 21L at the cutting point. Thus, the cutting operation of the lower vessel body 21L can be carried out smoothly.

[0067] Furthermore, in the second embodiment described above, the cutting device 50 can be installed in the workspace 30. Therefore, it becomes possible to utilize the wide area of ​​the workspace 30 to perform the cutting work on the lower container body 21L, thereby improving work efficiency.

[0068] (Modified version of the second embodiment) Figure 12 shows a step in which the reactor vessel body and the insulation material are moved vertically relative to each other in a modified example of the second embodiment. In the second embodiment described above, the case in which the reactor vessel body 21 is supported from above and moved upward by the vessel gripping device 45 was explained. However, the configuration is not limited to moving the reactor vessel body 21 upward using the vessel gripping device 45. For example, as shown in Figure 12, the reactor vessel body 21 may be supported from below using a frame 31a on which multiple stacking sections 131 can be stacked vertically. This makes it possible to move the reactor vessel body 21 upward in stages according to the number of stacking sections 131 of the frame 31a. When stacking the stacking sections 131 of the frame 31a, for example, the reactor vessel body 21 can be temporarily lifted by a lifting wire 29, and during this time, the stacking sections 131 of the frame 31a can be added, and the reactor vessel body 21 can be placed on these added stacking sections 131 of the frame 31a. Note that the insulation material support section 35 is not shown in Figure 12.

[0069] (Other embodiments) This disclosure is not limited to the configurations of the embodiments described above, and design modifications are possible without departing from the gist of the disclosure. For example, the cutting devices 40, 50, container gripping device 45, stands 31, 31a, stacking section 131, etc., are not limited to the configuration of the above embodiment. Any device that has the necessary cutting and gripping functions is acceptable. Furthermore, while the above embodiment illustrates the use of wires, such as the lifting wire 29 and the vertical movement wire 32, the configuration is not limited to the use of wires, as long as it enables lifting and vertical movement. Furthermore, while the above embodiments and modifications illustrate the case in which the body insulation section 251 comprises an upper insulation section 251U and a lower insulation section 251L having a smaller diameter than the upper insulation section 251U, the configuration is not limited to this.

[0070] <Note> The reactor vessel dismantling methods S10 and S20 described in the embodiment can be understood, for example, as follows.

[0071] (1) The first method for dismantling a reactor vessel S10, S20 is a method for dismantling a reactor vessel having a reactor vessel body 21 and an insulating material 25 that covers the reactor vessel body 21 from the outer periphery, and includes steps S11, S21 for disconnecting the connection between the reactor vessel body 21 and the insulating material 25, steps S12, 22 for relatively moving the reactor vessel body 21 and the insulating material 25 up and down, and steps S13, 23 for cutting the portion that is no longer covered by the insulating material 25 due to the relative movement.

[0072] This prevents problems such as the cutting disc of the disc saw interfering with the insulation material 25 when cutting the reactor vessel body 21. Therefore, the dismantling work of the reactor vessel 2 can be carried out smoothly.

[0073] (2) The reactor vessel dismantling method S10 according to the second embodiment is the reactor vessel dismantling method S10 of (1), wherein in step S12 of moving the reactor vessel body 21 and the heat insulating material 25 up and down relative to each other, the heat insulating material 25 is moved upward with respect to the reactor vessel body 21.

[0074] This makes it possible to avoid positioning the insulation material 25 on the outer circumference of the reactor vessel body 21 at the cutting point, even if there is insufficient space to move the insulation material 25 relative to the reactor vessel body 21 below it.

[0075] (3) A third method for dismantling a reactor vessel S20 is the method for dismantling a reactor vessel S20 of (1), wherein in step S22 of moving the reactor vessel body 21 and the heat insulating material 25 up and down relative to each other, the reactor vessel body 21 and the heat insulating material 25 are moved up and down relative to each other such that the reactor vessel body 21 is positioned above and the heat insulating material 25 is positioned below.

[0076] As a result, the insulation material 25 is not located on the outer circumference of the reactor vessel body 21 that has moved above the insulation material 25. Therefore, by cutting the reactor vessel body 21 that has moved above the insulation material 25, it is possible to prevent problems such as the cutting disc of the disc saw interfering with the insulation material 25.

[0077] (4) A fourth method for dismantling a reactor vessel S20 is the method for dismantling a reactor vessel S20 of (1) or (3), wherein in step S22 of moving the reactor vessel body 21 and the heat insulating material 25 up and down relative to each other, the reactor vessel body 21 is moved upward relative to the heat insulating material 25.

[0078] This allows the reactor vessel body 21 to be gradually moved upward, exposing it above the insulation material 25. Therefore, even if there is insufficient space above the reactor vessel body 21 to move the insulation material 25 relative to it, the insulation material 25 can be kept away from the outer periphery of the reactor vessel body 21.

[0079] (5) A fifth method for dismantling a reactor vessel S10 is the reactor vessel dismantling method S10 of (1) or (2), wherein the reactor vessel body 21 comprises an upper vessel body 21U and a lower vessel body 21L having a smaller diameter than the upper vessel body 21U, and the insulation material 25 comprises an upper insulation section 251U supported by the upper vessel body 21U and covering the upper vessel body 21U, and a lower insulation section 251L supported by the upper insulation section 251U and covering the lower vessel body 21L, and a step S11 of disconnecting the connection between the reactor vessel body 21 and the insulation material 25. Then, in step S12, which involves disconnecting the connection between the upper insulation section 251U and the lower insulation section 251L and moving the reactor vessel body 21 and the insulation material 25 up and down relative to each other, the upper vessel body 21U and the upper insulation section 251U are removed, and then the lower vessel body 21L and the lower insulation section 251L are moved up and down relative to each other. In step S13, which involves cutting the portion of the lower vessel body 21L that is no longer covered by the insulation material 25 due to the relative movement, the portion of the lower vessel body 21L that is no longer covered by the lower insulation section 251L due to the relative movement is cut.

[0080] This allows for upward displacement of the lower insulation section 251L relative to the lower vessel body 21L. Therefore, even if sufficient space cannot be secured below the reactor vessel body 21 to move the lower insulation section 251L relative to it, the lower insulation section 251L can be prevented from being positioned on the outer circumference of the lower vessel body 21L at the cutting point. Consequently, the cutting operation of the lower vessel body 21L can be carried out smoothly.

[0081] (6) A method S10 for dismantling a reactor vessel according to the sixth embodiment is the method S10 for dismantling a reactor vessel according to (1), wherein the reactor vessel 2 is installed inside a hole 130 formed in a pool 100 inside the reactor building, the insulation material 25 has a plurality of panel-shaped insulation material bodies 25b and a frame 25a that stacks and supports the plurality of insulation material bodies 25b in the vertical direction Dv, and in the process of removing the insulation material 25 upward from the hole 130, the insulation material bodies 25b that are exposed upward from the hole 130 are sequentially removed from the frame 25a.

[0082] This allows the insulation material body 25b to be removed from the frame 25a without the need to erect scaffolding for the removal work. Furthermore, since the frame 25a with the insulation material body 25b removed is easy to move, it can be moved to any space that facilitates dismantling work before being dismantled. Therefore, the work efficiency related to the dismantling of the insulation material 25 can be improved. In addition, when the insulation material body 25b is removed from the frame 25a, only a portion of the insulation material body 25b, which is the radiation source, is exposed through the hole 130. Therefore, by utilizing temporary shielding around the hole 130, the radiation exposure to workers dismantling the insulation material 25 can be reduced.

[0083] (7) A dismantling method S10 for a reactor vessel according to the seventh embodiment is the dismantling method S10 for a reactor vessel according to (5), wherein the lower insulation section 251L has a plurality of panel-shaped insulation material bodies 25b and a frame 25a that stacks and supports the plurality of insulation material bodies 25b in the vertical direction, and in step S12 in which the reactor vessel body and the insulation material are moved relative to each other vertically, the lower insulation section 251L that covers the lower vessel body 21L is moved upward with respect to the lower vessel body 21L which is located inside the concrete hole 130 after the upper vessel body 21U and the upper insulation section 251U have been removed, and the insulation material bodies 25b are removed from the frame 25a above the hole 130 while the lower insulation section 251L is being moved upward.

[0084] This eliminates the need to erect large scaffolding on the first floor 111, etc., for workers to remove the panels of the insulation material body 25b, as is the case when removing the panels of the insulation material body 25b on the first floor 111, etc. Furthermore, on the first floor 111, etc., only the frame 25a, which is lighter and has less volume compared to the lower insulation section 251L, needs to be dismantled, so the work can be done using a simple workbench, reducing the burden on the workers performing the dismantling work. In addition, even if the panels of the insulation material body 25b collapse unintentionally, the direction in which the panels fall will be limited to the direction of the hole 130, so workers can be positioned so as not to interfere with the falling objects. Therefore, worker safety can be improved. Furthermore, the primary shielding made of concrete around the hole 130 can be utilized. Therefore, the exposure effects on workers positioned in the work space 30 from the reactor vessel body 21 located inside the hole 130 and the lower insulation section 251L outside the dismantling area can be reduced. Furthermore, since the lower vessel body 21L can be dismantled while maintaining a distance from high-radiation areas of the reactor vessel body 21, the radiation exposure to workers dismantling the lower insulation section 251L can be reduced. In addition, since the insulation material body 25b can be removed from the top, the risk of the insulation material body 25b panels collapsing can be reduced. Moreover, by removing the insulation material body 25b above the hole 130, work efficiency can be improved and concerns about radiation exposure can be eliminated. [Explanation of Symbols]

[0085] 1… Pressurized water reactor 2…Reactor vessel 3…Control rod drive mechanism 5…Upper core structure 6…Lower core structure 21…Reactor vessel 21U…Upper container body 21L…Lower container body 21R…Reduced diameter part 22...Reactor vessel lid 23... Inlet nozzle 24…Outlet nozzle 25…Heat insulation material 25a...frame 25b…Heat insulation material body 26... Ring component 26a...First ring member 26b...Second ring member 27…Vertical members 28... Shielding cover 29… Lifting wire 30…Workspace 30a... Floor surface 31… Stand 32…Wire for vertical movement 33... Pulley 35...Heat insulation material support part 40...Cutting device 45...Container gripping device 45a...Columnar part 45b...gripping part 50...Cutting device 60...Waste containers 100... Pool inside the reactor building 110... First Cavity 111...First floor 120...Second cavity 121…Second floor surface 130...hole 130U... Upper storage area 130L... Lower storage compartment 131... Stacking section 140... Conduit tube 141... Incore Chess Room 142... Floor surface 211... Torso 212…Lower obstruction part 251... Torso insulation section 251U…Upper heat retention section 251L…lower heat retention section 252…Lower mirror heat retention part 252b…Heat insulation material body

Claims

1. A method for dismantling a reactor vessel, comprising a reactor vessel body and a cylindrical insulating material covering the reactor vessel body from the outer periphery, A step of disconnecting the connection between the reactor vessel body and the insulation material, The process involves moving the reactor vessel body and the insulating material vertically relative to each other while the insulating material is in a cylindrical state, The process includes cutting the portion that is no longer covered by the heat-insulating material due to the relative movement. Methods for dismantling a nuclear reactor vessel.

2. In the process of moving the reactor vessel body and the heat-insulating material up and down relative to each other, Move the heat-insulating material upward relative to the reactor vessel body. The method for dismantling a reactor vessel according to claim 1.

3. A method for dismantling a reactor vessel, comprising a reactor vessel body and an insulating material covering the reactor vessel body from the outer periphery, A step of disconnecting the connection between the reactor vessel body and the insulation material, A step of moving the reactor vessel body and the heat insulating material up and down relative to each other, The process includes cutting the portion that is no longer covered by the heat-insulating material due to the relative movement, In the process of moving the reactor vessel body and the heat-insulating material up and down relative to each other, The reactor vessel body and the insulating material are moved vertically relative to each other so that the reactor vessel body is positioned above and the insulating material is positioned below. Methods for dismantling a nuclear reactor vessel.

4. A method for dismantling a reactor vessel, comprising a reactor vessel body and an insulating material covering the reactor vessel body from the outer periphery, A step of disconnecting the connection between the reactor vessel body and the insulation material, A step of moving the reactor vessel body and the heat insulating material up and down relative to each other, The process includes cutting the portion that is no longer covered by the heat-insulating material due to the relative movement, In the process of moving the reactor vessel body and the heat-insulating material up and down relative to each other, Move the reactor vessel body upward relative to the heat-insulating material. Methods for dismantling a nuclear reactor vessel.

5. A method for dismantling a reactor vessel, comprising a reactor vessel body and an insulating material covering the reactor vessel body from the outer periphery, A step of disconnecting the connection between the reactor vessel body and the insulation material, A step of moving the reactor vessel body and the heat insulating material up and down relative to each other, The process includes cutting the portion that is no longer covered by the heat-insulating material due to the relative movement, The reactor vessel body comprises an upper vessel body and a lower vessel body having a smaller diameter than the upper vessel body. The aforementioned heat-insulating material comprises an upper heat-insulating section supported by the upper container body and covering the upper container body, and a lower heat-insulating section supported by the upper heat-insulating section and covering the lower container body. In the step of disconnecting the connection between the reactor vessel body and the insulation material, The connection between the upper insulation section and the lower insulation section is disconnected. In the process of moving the reactor vessel body and the heat-insulating material up and down relative to each other, After removing the upper container body and the upper insulation section, the lower container body and the lower insulation section are moved relative to each other vertically. In the step of cutting the portion that is no longer covered by the heat-insulating material due to the relative movement, The portion of the lower container body that is no longer covered by the lower heat-insulating section due to the relative movement is cut. Methods for dismantling a nuclear reactor vessel.

6. A method for dismantling a reactor vessel, comprising a reactor vessel body and an insulating material covering the reactor vessel body from the outer periphery, A step of disconnecting the connection between the reactor vessel body and the insulation material, A step of moving the reactor vessel body and the heat insulating material up and down relative to each other, The process includes cutting the portion that is no longer covered by the heat-insulating material due to the relative movement, The reactor vessel is installed inside a hole formed in the pool inside the reactor building. The aforementioned heat-insulating material comprises a plurality of panel-shaped heat-insulating material bodies and a frame that stacks and supports the plurality of heat-insulating material bodies in the vertical direction. While removing the insulation material upward from the hole, the insulation material body exposed upward from the hole is sequentially removed from the frame. Methods for dismantling a nuclear reactor vessel.

7. The lower insulation section comprises a plurality of panel-shaped insulation material bodies and a frame that stacks and supports the plurality of insulation material bodies in the vertical direction. In the process of moving the reactor vessel body and the heat-insulating material up and down relative to each other, After removing the upper container body and the upper insulation section, the lower insulation section covering the lower container body is moved upward relative to the lower container body which is positioned inside the hole in the concrete, and the insulation material body is removed from the frame above the hole while the lower insulation section is being moved upward. The method for dismantling a reactor vessel according to claim 5.

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