How to dismantle insulation material

Abstract

To ensure the dismantling of insulation materials proceeds smoothly. [Solution] A method for dismantling a thermal insulation material that covers a reactor vessel body from the outer periphery, comprising a plurality of thermal insulation material bodies and a frame that stacks and supports the plurality of thermal insulation material bodies in the vertical direction, comprising the steps of: moving the thermal insulation material upward in order to remove the thermal insulation material installed inside a hole formed in a pool inside a reactor building from the hole; and sequentially removing the thermal insulation material bodies that are exposed above the hole from the frame while the thermal insulation material is being removed upward from the hole.

Description

Technical Field

[0001] The present disclosure relates to a method for disassembling thermal insulation materials.

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 of 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 thermal insulation material that covers the reactor vessel body from the outside. When the reactor vessel is arranged in the hole of the concrete forming the primary shield, it is difficult to disassemble the thermal insulation material in the hole. On the other hand, when the thermal insulation material is taken out from the hole and then disassembled, there is a risk of collapse of the thermal insulation material and exposure of workers, so there is a problem that the disassembling work of the thermal insulation material cannot be carried out smoothly.

[0005] The present disclosure has been made in view of the above circumstances, and provides a method for disassembling a thermal insulation material that can smoothly perform the disassembling work of the thermal insulation material.

Means for Solving the Problems

[0006] To solve the above problems, the method for dismantling thermal insulation material according to this disclosure comprises a plurality of thermal insulation material bodies and a frame that stacks and supports the plurality of thermal insulation material bodies in the vertical direction, and is a method for dismantling thermal insulation material that covers the reactor vessel body from the outer periphery, comprising the steps of: moving the thermal insulation material upward in order to remove the thermal insulation material installed inside a hole formed in a pool inside the reactor building from the hole; and sequentially removing the thermal insulation material bodies that are exposed above the hole from the frame while the thermal insulation material is being removed upward from the hole. A step of cutting the frame with the insulation material body removed, Includes. [Effects of the Invention]

[0007] According to this disclosure, the dismantling of insulation materials 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 the stacking of the insulation material in the body insulation section. [Figure 4] This is a schematic diagram showing an enlarged view of the area near the boundary between the upper and lower container bodies. [Figure 5] This is a flowchart showing the method for dismantling the insulation material in this embodiment. [Figure 6] This is a schematic diagram showing the reactor vessel immediately before the dismantling method for the insulation material described above is implemented. [Figure 7] This figure shows the reactor vessel supported from below by a support structure. [Figure 8] 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 9] This diagram shows the lower insulation section moved downwards and the upper container removed. [Figure 10]This figure shows the lower insulation section in the state when it has been moved upward using a wire for vertical movement. [Figure 11] This diagram shows the lower insulation section being moved upwards by a crane. [Figure 12] This diagram shows the cutting position after moving the frame mentioned above. [Figure 13] This diagram shows the cutting position of the lower frame of the division. [Figure 14] This diagram shows the upper frame of the split screen moved downwards. [Modes for carrying out the invention]

[0009] The following describes an embodiment for implementing the method of dismantling the insulation material according to this disclosure, with reference to the attached drawings. However, this disclosure is not limited to this embodiment.

[0010] <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 spaces, 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. A first floor surface 111 on which an operator can walk is formed in the first cavity 110. 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 such 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 the hole 130 formed in the concrete as a primary shield. 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 upper part of the reactor vessel main body 21 can be opened by removing the reactor vessel head 22. The reactor vessel main body 21 integrally has a cylindrical 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] The upper part of the reactor vessel body 21 has an inlet nozzle 23 (inlet nozzle holder) for supplying light water (coolant) as primary cooling water (water), and an outlet nozzle 24 (outlet nozzle holder) for discharging light water. In addition, the reactor vessel body 21 has an injection nozzle (injection nozzle holder) (not shown) formed separately from the inlet nozzle 23 and the outlet nozzle 24.

[0015] The reactor vessel lid 22 is attached to the top of the reactor vessel body 21. The reactor vessel lid 22 is fixed to the reactor vessel body 21 so as to be openable and closable by a plurality of stud bolts and nuts (not shown).

[0016] (Heat insulation material) As shown in Figure 2, the insulation material 25 covers the reactor vessel body 21 from the outer periphery. The insulation material 25 has the function of suppressing the transfer of thermal energy from the reactor vessel body 21 to the gas and concrete inside the reactor building. The insulation material 25 exemplified in this embodiment has a body insulation section 251 and a lower end insulation section 252. The body insulation section 251 is arranged to cover the outer periphery of the reactor vessel body 21. The lower end insulation section 252 is arranged to cover the lower closure section 212 of the reactor vessel body 21 from below. Although the case in which the insulation material 25 comprises a body insulation section 251 and a lower end insulation section 252 has been described, the configuration is not limited to this. For example, the lower end insulation section 252 may be omitted, and the lower closure section 212 may be covered only by the body insulation section 251. In this case, the body insulation section 251 can be extended below the lower closing section 212, and the lower edge of the body insulation section 251 can be closed. Alternatively, when the lower closing section 212 is covered by the body insulation section 251 in this manner, the second ring member 26b of the body insulation section 251 may be positioned below the lower closing section 212.

[0017] (Body insulation section) The body insulation section 251 comprises a frame 25a and an insulation material body 25b. The frame 25a supports the insulation material body 25b. The frame 25a has a circularly formed ring member 26 that covers the entire circumference of the reactor vessel body 21 and a vertical member 27 that extends in a direction intersecting the ring member 26. The frame 25a and the body 211 of the reactor vessel body 21 are positioned with a small gap in the radial direction of the body 211.

[0018] (frame) 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] (Insulation material itself) Figure 3 is a schematic diagram showing the stacking of the insulation material in the body insulation section. 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 consists of, for example, a box-shaped panel with a metal film laminated inside. As shown in Figure 3, in the insulation material body 25b of this embodiment, multiple panel-shaped insulation material bodies 25b are stacked on, for example, the second ring member 26b and arranged without gaps in the vertical and circumferential directions to form a cylindrical shape. The multiple panel-shaped insulation material bodies 25b in this embodiment each form an arc shape with the same radius of curvature when viewed from above. Adjacent insulation material bodies 25b are connected to each other using, for example, fasteners (not shown) arranged on the outer circumference of the insulation material body 25b.

[0021] Figure 4 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 4, the body 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 diameter section 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 diameter section 21R. Note that the frame 25a is not shown in Figure 4.

[0022] As shown in Figures 2 and 4, 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, in the first cavity 110 of the reactor building pool 100 described above, a hole 130 is formed to accommodate the reactor vessel 2 in order to construct primary shielding against the reactor vessel 2. The hole 130 is formed to be recessed downward from the first floor surface 111. As shown in Figure 4, the hole 130 in this embodiment has an upper housing section 130U that accommodates the upper vessel body 21U and the upper insulation section 251U, and a lower housing section 130L that accommodates 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] (How to dismantle insulation material) The following describes a method for dismantling the heat-insulating material 25 according to the embodiment of this disclosure. Figure 5 is a flowchart showing the method for dismantling the heat-insulating material in this embodiment. As shown in Figure 5, the insulation material dismantling method S10 in this embodiment includes the steps of: S11 to disconnect the connection between the reactor vessel body and the insulation material; S12 to move the insulation material upward; S13 to remove the insulation material body exposed upward through the hole from the frame; and S14 to cut the frame from which the insulation material body has been removed.

[0029] Figure 6 is a schematic diagram showing the reactor vessel immediately before the dismantling method of the insulation material described above is implemented. Here, before carrying out the insulation material dismantling method S10 described above, preparations are made to dismantle the insulation material 25. In this embodiment, the reactor vessel lid 22 of the reactor vessel 2 is removed, and the upper core structure 5 and the lower core structure 6 are removed from inside the reactor vessel body 21 and dismantled by an appropriate method. Furthermore, as shown in Figure 6, a shielding lid 28 is attached to the reactor vessel body 21 to close the reactor vessel body 21.

[0030] On the other hand, the concrete of the upper containment section 130U surrounding the upper vessel body 21U and the upper insulation section 251U is removed. In this process, concrete is removed in a predetermined range around the entire circumference of the reactor vessel body 21. This creates a workspace 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 workspace 30 is formed. With the formation of the workspace 30, the concrete of the floor surface 30a of the workspace 30 supports the inlet nozzle 23 and the 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 the outlet nozzle 24 and the floor surface 30a.

[0031] 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.

[0032] In this embodiment, the lower end insulation section 252 of the insulation material 25 is removed, leaving the body insulation section 251. Also, through-pipes (not shown) such as instrumentation pipes or conduit tubes 140 that penetrate the lower closure section 212 are cut and removed. At this time, plugs are placed in the through-pipes remaining in the lower closure section 212 to prevent water leakage. After that, 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.

[0033] Figure 7 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 7, 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, an example can be given of making 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.

[0034] 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.

[0035] Figure 8 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 8, 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.

[0036] 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.

[0037] Figure 9 shows the state after the lower insulation unit has been moved downwards and the upper container has been removed. As shown in Figure 9, in step S11 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 10 shows the lower insulation section being moved upward using a wire for vertical movement. Figure 11 shows the lower insulation section being moved upward using a crane. In step S12, which involves moving the insulation material upward, the lower insulation section 251L, which is located in the lower storage section 130L of the hole 130, is moved upward. As shown in Figure 10, in step S12, the vertical movement wire 32 is wound up to move the upper edge of 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, making it possible to lift the lower insulation section 251L upward with a crane. Then, the lower insulation section 251L is moved upward with a crane in order to remove the lower insulation section 251L upward from the lower housing section 130L of the hole 130. This upward movement of the lower insulation section 251L can be exemplified by moving it slowly at a constant speed or moving it intermittently at predetermined intervals.

[0040] In step S13, which involves removing the insulation material body exposed upward from the hole from the frame, the insulation material body 25b of the lower insulation section 251L that is exposed upward from the lower housing section 130L of the hole 130 is sequentially removed while the lower insulation section 251L is being pulled upward from the lower housing section 130L of the hole 130. As shown in Figure 11, in this embodiment, a worker W is positioned in a work space 30 formed above the lower housing section 130L of the hole 130, and the worker W positioned in this work space 30 sequentially removes only the insulation material body 25b of the lower insulation section 251L that is exposed upward from the lower housing section 130L of the hole 130. At this time, the insulation material body 25b positioned at the very top around the entire circumference of the lower insulation section 251L is removed. In other words, the insulation material body 25b of the lower insulation section 251L is sequentially removed from top to bottom.

[0041] Figure 12 shows the cutting position after moving the frame described above. Figure 13 shows the cutting position of the lower divided frame. Figure 14 shows the state after moving the upper divided frame downwards. In step S14, which involves cutting the frame from which the insulation material body has been removed, the frame 25a of the lower insulation section 251L, from which the insulation material body 25b has been completely removed, is cut into several smaller pieces. Specifically, the lower insulation section 251L, which has been lifted above the work space 30, consists only of the frame 25a, and this frame 25a is moved to, for example, the first floor surface 111. Then, the frame 25a that has been moved to the first floor surface 111 is dismantled by worker W.

[0042] Specifically, as shown in Figure 12, the upper part of frame 25a is supported from above by a crane or the like, and the frame 25a is cut at a position midway between the top and bottom (for example, the position shown by the dashed line in Figure 12). At this time, worker W climbs onto a workbench D or the like and cuts frame 25a with a cutting tool such as a disc saw. This results in a divided upper frame 25au and a divided lower frame 25ab. The divided upper frame 25au is supported from above by a crane or the like, while the divided lower frame 25ab is placed on the first floor surface 111.

[0043] Next, the divided lower frame 25ab, which is placed on the first floor surface 111, is dismantled by the worker W. Specifically, as shown in Figure 13, it is cut at a position that is small enough to fit into the waste container 60 (for example, the position shown by the dashed line in Figure 13). In this embodiment, the cutting positions of the divided lower frame 25ab are all at a height that can be reached by the worker W on the first floor surface 111. The cut pieces of the divided lower frame 25ab are stored in the waste container 60.

[0044] Subsequently, the divided upper frame 25au, which is supported from above by a crane or the like, is moved downwards and dismantled. For example, as shown in Figure 14, a worker W who has climbed onto a work platform D or the like detaches the lifting wire 29 extending from the crane or the like from the divided upper frame 25au. Then, the divided upper frame 25au, which has been released from its support from above, is cut on the first floor surface 111 or the like and stored in a waste container (not shown). The divided upper frame 25au may also be cut while it is lifted by the lifting wire 29.

[0045] (Removal of the reactor vessel) The reactor vessel body 21, which is no longer covered by the insulation material 25, is cut and removed. In other words, in this embodiment, the lower vessel body 21L, which is no longer covered by the lower insulation section 251L, is cut and removed by the cutting device 40, just like the upper vessel body 21U.

[0046] (Effects and Benefits) In the insulation material dismantling method S10 of the above embodiment, while the insulation material 25 is being pulled upward from the hole 130, the insulation material body 25b that is exposed upward from the hole 130 is sequentially removed from the frame 25a. This allows the insulation material body 25b to be removed from the frame 25a without having to erect scaffolding for the work of removing the insulation material body 25b from the frame 25a. 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 the primary shielding around the hole 130, the radiation exposure to workers dismantling the insulation material 25 can be reduced. Furthermore, when a worker W positioned in the work space 30 removes the insulation material body 25b from the frame 25a, even if the insulation material body 25b unintentionally collapses, the direction in which the insulation material body 25b falls is limited to the inside of the hole 130. Therefore, the worker W can be positioned so as not to interfere with the falling object. Thus, the dismantling work of the insulation material can be carried out smoothly.

[0047] Furthermore, in the insulation material dismantling method S10 of the above embodiment, the frame 25a, from which the insulation material body 25b has been removed, is moved before dismantling. Since it is easy to move the frame 25a from which the insulation material body 25b has been removed, the frame 25a can be moved to any space where dismantling work can be easily performed before dismantling. Also, since only the frame 25a, which is lighter and has less volume compared to the lower insulation section 251L, needs to be dismantled, the work can be performed using a simple workbench. Therefore, the workability related to the dismantling of the insulation material 25 can be improved.

[0048] Furthermore, in the insulation material dismantling method S10 of the above embodiment, the frame 25a is divided into the upper frame 25au and the lower frame 25ab, and then cut and dismantled respectively. Therefore, cutting work can be performed by workers W without having to erect scaffolding or other equipment for working at heights. Thus, the work efficiency related to the dismantling of the frame 25a can be improved.

[0049] Furthermore, in the insulation material dismantling method S10 of the above embodiment, the connection between the reactor vessel body 21 and the insulation material 25 is disconnected. Therefore, only the insulation material 25 can be moved upward. Consequently, there is no need to move the reactor vessel body 21 together with the insulation material 25, which improves the workability when moving the insulation material 25 upward.

[0050] Furthermore, in the insulation material dismantling method S10 of the above embodiment, the connection between the upper insulation section 251U and the lower insulation section 251L is disconnected, the upper container body 21U and the upper insulation section 251U are removed, and then the lower insulation section 251L is moved upward, and the insulation material body 25b of the lower insulation section 251L, which is exposed upward through the hole 130, is sequentially removed from the frame 25a. By removing the upper container body 21U, which has a larger diameter than the lower container body 21L, and the upper insulation section 251U that covers the upper container body 21U, it becomes possible to displace the lower insulation section 251L upward relative to the lower container body 21L. Therefore, it becomes possible to move the lower insulation section 251L upward smoothly.

[0051] Furthermore, if the lower insulation section 251L is dismantled (the insulation material 25 is dismantled) without moving the insulation material 25 upward as described above, workers will be strongly affected by radiation exposure from the lower vessel body 21L of the fuel area. However, by moving the lower insulation section 251L relative to the lower vessel body 21L (reactor vessel body 21) as described above, 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.

[0052] 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.

[0053] Furthermore, since the insulation material body 25b, which is located above the frame 25a of the lower insulation section 251L, is removed sequentially, the risk of the insulation material body 25b collapsing can be reduced, as would occur when dismantling the insulation material body 25b stacked on top of the second ring member 26b from the bottom.

[0054] Furthermore, if the insulation material 25 and the reactor vessel body 21 are not moved (separated) relative to each other 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 the 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 for the public and workers W. However, by moving the insulation material 25 and the reactor vessel body 21 relative to each other before dismantling, as described above, workability can be improved and concerns about radiation exposure can be eliminated.

[0055] (Other embodiments) This disclosure is not limited to the configuration of the embodiments described above, and design modifications are possible without departing from the spirit thereof. For example, in the above embodiment, the case in which the insulation material 25 is dismantled before the dismantling of the reactor vessel body 21 is completed was described as an example, but the configuration is not limited to this. For example, the insulation material 25 may be moved upward after the dismantling of the reactor vessel body 21 and the insulation material body 25b may be removed.

[0056] 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.

[0057] Furthermore, although the above embodiment illustrates a case where 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. Similarly, although the above embodiment illustrates a case where the hole 130 has an upper housing section 130U and a lower housing section 130L, the configuration is not limited to this.

[0058] <Note> The method S10 for dismantling the heat-insulating material described in the embodiment can be understood, for example, as follows.

[0059] (1) A method for dismantling a thermal insulation material according to the first embodiment S10 comprises a plurality of thermal insulation material bodies 25b and a frame 25a that stacks and supports the plurality of thermal insulation material bodies 25b in the vertical direction, and is a method for dismantling a thermal insulation material 25 that covers the reactor vessel body 21 from the outer periphery, and includes a step S12 of moving the thermal insulation material 25 upward in order to remove the thermal insulation material 25 installed inside a hole 130 formed in a pool 100 inside the reactor building from the hole 130, and a step S13 of sequentially removing the thermal insulation material bodies 25b that are exposed above the hole 130 from the frame 25a while the thermal insulation material 25 is being removed upward from the hole 130.

[0060] This allows the insulation material body 25b to be removed from the frame 25a without having to erect scaffolding for the work of removing the insulation material body 25b from the frame 25a. 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 the primary shielding around the hole 130, the radiation exposure to workers dismantling the insulation material 25 can be reduced.

[0061] (2) The method for dismantling the insulation material S10 according to the second embodiment is the method for dismantling the insulation material S10 of (1), further comprising the step S14 of cutting the frame 25a in the state in which the insulation material body 25b has been removed.

[0062] This allows the frame 25a to be moved to any space that facilitates dismantling before being dismantled. Furthermore, since only the frame 25a, which is lighter and less bulky than the lower insulation section 251L, needs to be dismantled, the work can be carried out using a simple workbench. Therefore, the work efficiency related to the dismantling of the insulation material 25 can be improved.

[0063] (3) A third method for dismantling the insulation material S10 is the method for dismantling the insulation material S10 of (2), wherein the step S14 for cutting the frame 25a includes the steps of: cutting the frame 25a in the middle of the upper and lower parts while supporting the upper part of the frame 25a from above to obtain a divided upper frame 25au and a divided lower frame 25ab; dismantling the divided lower frame 25ab on the floor surface 111; and moving the divided upper frame 25au downward to dismantle the divided upper frame 25au.

[0064] This allows cutting work to be performed by worker W without the need to erect scaffolding for working at heights. Therefore, the work efficiency related to the dismantling of frame 25a can be improved.

[0065] (4) The fourth method of dismantling the insulation material S10 is any one of the methods of dismantling the insulation material S10 from (1) to (3), further comprising a step S11 of disconnecting the connection between the reactor vessel body 21 and the insulation material 25.

[0066] This allows only the insulation material 25 to be moved upward. Therefore, since it is not necessary to move the reactor vessel body 21 together with the insulation material 25, the workability when moving the insulation material 25 upward can be improved.

[0067] (5) A fifth method for dismantling the insulation material S10 is the method for dismantling the insulation material S10 of (4), 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 in step S11 for disconnecting the connection between the reactor vessel body 21 and the insulation material 25, the connection between the upper insulation section 251U and the lower insulation section 251L is disconnected, and in step S12 for moving the insulation material 25 upward, the upper vessel body 21U and the upper insulation section 251U are removed and then the lower insulation section 251L is moved upward.

[0068] This allows the lower insulation section 251L to be displaced upward relative to the lower container body 21L. Therefore, the upward movement of the lower insulation section 251L can be made smooth. [Explanation of Symbols]

[0069] 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 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 insulation material that covers the reactor vessel body from the outer periphery, comprising multiple insulation material bodies and a frame that stacks and supports the multiple insulation material bodies in the vertical direction, A step of moving the insulating material upward in order to remove the insulating material installed inside a hole formed in the pool inside the reactor building from the hole, The process of sequentially removing the insulation material body that is exposed upward from the hole from the frame while removing the insulation material upward from the hole, The process of cutting the frame with the insulation material body removed, including How to dismantle insulation material.

2. The process of cutting the frame includes: a step of cutting the frame in the middle section while supporting the upper part of the frame from above to obtain a divided upper frame and a divided lower frame; a step of dismantling the divided lower frame on the floor surface; and a step of moving the divided upper frame downward to dismantle the divided upper frame. A method for dismantling an insulating material as described in claim 1.

3. The process further includes a step of disconnecting the connection between the reactor vessel body and the insulation material. A method for dismantling an insulating material as described in claim 1.

4. 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 step of moving the aforementioned heat-insulating material upward, After removing the upper container body and the upper insulation section, move the lower insulation section upward. A method for dismantling an insulating material as described in claim 3.

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