Method and apparatus for dismantling a bottomed cylindrical member

Abstract

To efficiently dismantle bottomed cylindrical components while minimizing the effects of radioactivity. [Solution] A method for dismantling a bottomed cylindrical member is provided inside a reactor containment vessel and has a body portion extending in the vertical direction and a lower closing portion that closes the lower end of the body portion, and includes the steps of: filling a bottomed cylindrical member installed in a concrete hole with water; cutting the bottomed cylindrical member from the inside of the bottomed cylindrical member above the water level in the bottomed cylindrical member; and transporting the cut pieces generated by cutting the bottomed cylindrical member to the outside of the bottomed cylindrical member.

Description

Technical Field

[0004] ,

[0006] , , , , , ,

[0005] , , , It is installed in a concrete hole formed in the cavity of the reactor building's indoor pool, which is recessed downward from the floor surface. , , ,

[0001] The present disclosure relates to a method and apparatus for disassembling a bottomed cylindrical member.

Background Art

[0002] Patent Document 1 discloses a technique for disassembling in-vessel structures in a reactor vessel in water stored in a working pool and carrying out the disassembled in-vessel structures from the working pool in a method for disassembling a nuclear power plant.

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 order to disassemble a nuclear power plant as described in Patent Document 1, it is necessary to cut a bottomed cylindrical member such as a reactor vessel into a plurality of cut pieces, store them in a waste container for storing radioactive waste, and then carry them out to the outside of the reactor containment vessel. However, since the bottomed cylindrical members such as the reactor vessel provided in the reactor containment vessel are often high-level radioactive waste, it is desired to efficiently disassemble the bottomed cylindrical members while suppressing the influence of radioactivity.

[0005] The present disclosure has been made to solve the above problems, and an object thereof is to provide a method and apparatus for disassembling a bottomed cylindrical member that can efficiently disassemble the bottomed cylindrical member while suppressing the influence of radioactivity.

Means for Solving the Problems

[0006] In order to solve the above problems, the method for disassembling a bottomed cylindrical member according to the present disclosure is Pool inside the reactor building of a pressurized water reactor provided inside, It is installed in a concrete hole formed in the cavity of the reactor building's indoor pool, which is recessed downward from the floor surface.This is a method for dismantling a bottomed cylindrical member having a body portion extending in the vertical direction and a lower closing portion that closes the lower end of the body portion. The method for dismantling the bottomed cylindrical member includes the steps of filling the bottomed cylindrical member with water, cutting the bottomed cylindrical member, and discharging the cut pieces to the outside of the bottomed cylindrical member. The step of filling the bottomed cylindrical member with water is, The aforementioned Inside the concrete hole The bottomed cylindrical member installed In that state, The process involves filling the bottomed cylindrical member with water. The process of cutting the bottomed cylindrical member involves cutting the bottomed cylindrical member from the inside of the bottomed cylindrical member above the water level in the bottomed cylindrical member. The process of transporting the cut pieces to the outside of the bottomed cylindrical member involves transporting the cut pieces generated by cutting the bottomed cylindrical member to the outside of the bottomed cylindrical member.

[0007] The dismantling apparatus according to this disclosure is a dismantling apparatus used in a method for dismantling the bottomed cylindrical member described above, and comprises: a base fixed to the lower part inside the bottomed cylindrical member; a column member extending vertically upward from the base; a table that can move vertically up and down inside the bottomed cylindrical member along the central axis of the column member; a first disc saw provided on the table and capable of moving vertically up and down, having a disc shape located in a vertical plane extending radially around the central axis, and having a first cutting disc capable of cutting the bottomed cylindrical member from the inside; and a second disc saw provided on the table and having a disc shape located in a horizontal plane intersecting the vertical direction, and having a second cutting disc capable of cutting the bottomed cylindrical member from the inside. [Effects of the Invention]

[0008] According to this disclosure, the dismantling of the bottomed cylindrical member can be carried out efficiently while minimizing the effects of radioactivity. [Brief explanation of the drawing]

[0009] [Figure 1] This is a longitudinal cross-sectional view showing a pressurized water reactor, which is a reactor to be dismantled according to the embodiment of this disclosure. [Figure 2]This is a schematic diagram showing a pressurized water reactor, with water stored inside according to the embodiment, with the reactor vessel lid removed, positioned inside the reactor building. [Figure 3] This figure shows the reactor vessel body, which is the target of cutting by the reactor vessel dismantling method according to the embodiment. [Figure 4] This figure shows a dismantling device used for dismantling the reactor vessel body, arranged inside a bottomed cylindrical member, in a method for dismantling a bottomed cylindrical member according to an embodiment. [Figure 5] This is a flowchart showing a method for dismantling the reactor vessel body according to the embodiment of this disclosure. [Figure 6] This figure shows the state in which the bottomed cylindrical member is being cut vertically during the step of cutting the bottomed cylindrical member in the dismantling method for the bottomed cylindrical member according to the embodiment. [Figure 7] This is a plan view showing the state in which the bottomed cylindrical member is being cut vertically in the step of cutting the bottomed cylindrical member in the dismantling method for the bottomed cylindrical member according to the embodiment. [Figure 8] This figure shows the step of cutting a bottomed cylindrical member in the circumferential direction in a method for dismantling a bottomed cylindrical member according to an embodiment. [Figure 9] This is a plan view showing the state in which the bottomed cylindrical member is being cut in the circumferential direction during the step of cutting the bottomed cylindrical member in the dismantling method for the bottomed cylindrical member according to the embodiment. [Figure 10] This is a plan view showing one of the steps for cutting a bottomed cylindrical member in the circumferential direction, in the dismantling method for a bottomed cylindrical member according to the embodiment. [Figure 11] This figure shows the state following Figure 10. [Figure 12] This figure shows the step of lowering the water level in the dismantling method for a bottomed cylindrical member according to the embodiment. [Modes for carrying out the invention]

[0010] Hereinafter, with reference to the accompanying drawings, embodiments for implementing a method and apparatus for disassembling a bottomed cylindrical member according to the present disclosure will be described. However, the present disclosure is not limited to only this embodiment.

[0011] <Embodiment> (Nuclear reactor) FIG. 1 is a longitudinal sectional view showing a pressurized water reactor 1 which is a nuclear reactor to be disassembled according to the embodiment. The nuclear reactor exemplified in the present embodiment uses light water as a nuclear reactor coolant and a neutron moderator, and is high-temperature and high-pressure water that does not boil throughout the reactor core. This high-temperature and high-pressure water is sent to a steam generator to generate steam by heat exchange, and this steam is sent to a turbine generator to generate electricity. It is a pressurized water reactor 1 (PWR: Pressurized Water Reactor).

[0012] As shown in FIG. 2, the pressurized water reactor 1 is disposed in a reactor building pool 100 provided in a reactor building (not shown). In the reactor building pool 100, a space capable of storing cooling water (water) is formed. 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.

[0013] The pressurized water reactor 1 of the present embodiment includes a reactor vessel 2, an upper reactor core structure 5, and a lower reactor core structure 6 in a reactor containment vessel (not shown) as shown in FIGS. 1 and 2.

[0014] The reactor vessel 2 has a reactor vessel main body (bottomed cylindrical member) 21 and a reactor vessel head 22 (upper mirror) so that the in-vessel structures can be inserted therein. As shown in FIG. 2, the reactor vessel 2 is disposed inside a concrete hole 15 formed to be recessed with respect to the first floor surface 11; and is disposed in a state where a part thereof (specifically, the reactor vessel head 22) protrudes from the first floor surface 111.

[0015] 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 part 211 and a lower closing part 212. The cylindrical 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 cylindrical part 211. The lower closing part 212 is a lower mirror having a hemispherical shape.

[0016] An inlet nozzle 23 (inlet header) for supplying light water (coolant) as primary cooling water (water) and an outlet nozzle 24 (outlet header) for discharging the light water are formed at the upper part of the reactor vessel main body 21. Further, a water injection nozzle (water injection header) not shown is formed in the reactor vessel main body 21 separately from the inlet nozzle 23 and the outlet nozzle 24.

[0017] The reactor vessel head 22 is mounted on 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.

[0018] The upper core structure 5 is disposed inside the reactor vessel 2. The upper core structure 5 can be withdrawn from the reactor vessel main body 21 by being moved upward in the vertical direction Dv with respect to the reactor vessel main body 21. The upper core structure 5 of the present embodiment has an upper core plate 51, an upper core support plate 52, upper core support columns 53, guide tubes 55, and a water level gauge support tube (not shown). Note that the upper core structure 5 does not have only the structure described above. The upper core structure 5 has other components such as a mixer, a thermocouple lead-out tube, and a reinforcing beam as components not shown.

[0019] As shown in Figures 1 and 2, 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.

[0020] (Method for dismantling the reactor vessel) The following describes a method for dismantling the reactor vessel body 21 according to the embodiment of this disclosure. Figure 3 shows the reactor vessel body that is to be cut by the reactor vessel dismantling method according to the embodiment. As shown in Figure 3, the reactor vessel body 21 is cut into multiple pieces. In this embodiment, the reactor vessel body 21 is dismantled by cutting at least the torso 211 into multiple pieces 215. To dismantle the reactor vessel body 21, the torso 211 is cut in the circumferential direction Dh and the vertical direction Dv. In this embodiment, for example, the reactor vessel body 21 is cut in the vertical direction Dv at each of a plurality of cutting positions K spaced apart in the circumferential direction Dh. Then, between adjacent cutting positions K in the circumferential direction Dh, the torso 211 is cut in the circumferential direction Dh at a position Q a predetermined distance below the upper end of the torso 211. As a result, pieces 215 that are curved in an arc shape when viewed from the vertical direction Dv are cut out from the torso 211.

[0021] Figure 4 shows the dismantling device 300 used for dismantling the reactor vessel body 21 in the dismantling method for a bottomed cylindrical member according to the embodiment, with the device positioned inside the bottomed cylindrical member. In this embodiment, a dismantling device 300 is used to dismantle the reactor vessel body 21. As shown in Figure 4, the dismantling device 300 comprises at least a base 310, a column member 320, a table 330, a support member 340, a first disc saw 350, a second disc saw 360, and a gripping member 370.

[0022] The base 310 is fixed to the reactor vessel body 21. In this embodiment, the base 310 is formed from steel material or steel plate extending in a direction intersecting the vertical direction Dv. The base 310 is located in the lower part of the reactor vessel body 21, more specifically within the lower closure portion 212.

[0023] A fixing member 312 is provided on the outer circumference of the base 310. The fixing member 312 fixes the base 310 to a projection 212t provided on the inner circumferential surface of the lower closing portion 212. The fixing member 312 includes, for example, an upper fixing member 313 that rises upward from the base 310 and follows the upper surface of the projection 212t, and a lower fixing member 314 positioned below the projection 212t. The lower fixing member 314 is provided so as to be able to move radially back and forth relative to the upper fixing member 313. By moving the lower fixing member 314 radially outward, the projection 212t is sandwiched between the upper fixing member 313 and the lower fixing member 314 from above and below, thereby fixing the base 310 to the lower closing portion 212. Note that the method of fixing the base 310 to the lower closing portion 212 is not limited to the fixing member 312, and other methods may be used as appropriate.

[0024] The column member 320 extends upward from the base 310 in the vertical direction Dv. The column member 320 has a circular cross-sectional shape when viewed from the vertical direction Dv and is positioned to coincide with the central axis C of the body 211 of the reactor vessel body 21. Note that the cross-sectional shape of the column member 320 is an example and is not limited to a circular shape.

[0025] The table 330 integrally comprises a cylindrical section 331 provided radially outward of the column member 320 and extending vertically in the direction Dv, and a table body 332 that extends radially outward from the cylindrical section 331. The table 330 is provided so as to be able to move vertically in the direction Dv along the column member 320 by a lifting mechanism such as a winch (not shown). The table 330 is also provided so as to be able to rotate in the circumferential direction Dh about the central axis C by a motor or the like (not shown).

[0026] The support member 340 is provided on the underside of the table 330. The support member 340 has a base member 341 extending radially outward from the column member 320, and an actuator 342, such as a cylinder mechanism, that can extend and retract radially from the base member 341. The base member 341 is provided so as to be able to move up and down vertically in the direction Dv along the column member 320 by a lifting mechanism (not shown). Multiple actuators 342 are provided at intervals in the circumferential direction Dh. The support member 340 prevents the column member 320 from tilting by extending the multiple actuators 342 radially outward at a position above the base 310 and abutting them against the inner circumferential surface of the body 211.

[0027] The first disc saw 350 comprises a first cutting disc 351 and a disc saw body (not shown). The first cutting disc 351 is disc-shaped and located in a vertical plane extending radially from a central axis C, and has a plurality of cutting blades (not shown) on its outer circumference. The disc saw body has a drive source such as a motor that rotates the first cutting disc 351. The first disc saw 350 is mounted on a table body 332 so as to be able to move up and down in the vertical direction Dv along a guide 353 provided on the table body 332 by a lifting mechanism (not shown).

[0028] The second disc saw 360 comprises a second cutting disc 361 and a disc saw body (not shown). The second cutting disc 361 is disc-shaped and located in a horizontal plane intersecting the vertical direction Dv, and has a plurality of cutting blades (not shown) on its outer circumference. The disc saw body has a drive source such as a motor that rotates the second cutting disc 361. The second disc saw 360 is mounted to move radially back and forth relative to the table body 332 along a guide 363 provided on the table body 332 by a reciprocating mechanism (not shown).

[0029] The gripping member 370 has an arm 371 and a gripping portion 372. The arm 371 extends radially outward from the cylindrical portion 331. The arm 371 is extendable and retractable in the radial direction. The gripping portion 372 is provided at the tip of the arm 371 and is provided to be able to move up and down in the vertical direction Dv. The gripping portion 372 is provided to be able to clamp the upper end of the body portion 211 of the reactor vessel body 21 from both radial sides. The gripping member 370 is provided at different positions in the circumferential direction Dh around the central axis C of the column member 320 with respect to the first disc saw 350.

[0030] The first disc saw 350, the second disc saw 360, and the gripping member 370 are provided together with the table 330 so as to be able to move up and down vertically in the direction Dv along the column member 320 and to rotate in the direction Dh circumferentially.

[0031] The dismantling of the reactor vessel body 21 is carried out while the reactor vessel body 21 remains installed in the concrete hole 15 of the reactor building pool 100, as shown in Figure 2. The cutting of the reactor vessel body 21 is carried out after the reactor vessel lid 22 has been removed from the reactor vessel body 21, and further, after the upper core structure 5 and lower core structure 6 have been removed from inside the reactor vessel body 21. Here, there are no limitations on the method of removing the upper core structure 5 and lower core structure 6 from inside the reactor vessel body 21, and any appropriate method may be used.

[0032] Figure 5 is a flowchart showing a dismantling method S10 for the reactor vessel body 21 according to the present disclosure. As shown in Figure 5, the dismantling method S10 for the reactor vessel body 21 includes the steps of filling the reactor vessel body 21 with water S11, cutting the reactor vessel body 21 S12, transporting the cut pieces 215 to the outside of the reactor vessel body 21 S13, and lowering the water level Wf S14.

[0033] In step S11, which involves filling the reactor vessel body 21 with water, water is filled into the reactor vessel body 21, which is installed in the concrete hole 15, using a pump (not shown) or the like. At this time, the water level Wf inside the reactor vessel body 21 is set to be below the table 330.

[0034] Furthermore, a support frame 70 is installed below the lower closure section 212 at an appropriate time to support the lower closure section 212 from below. The support frame 70 is installed on a third floor surface 113 located below the lower closure section 212. A ring member 80 is also attached to the lower closure section 212. The ring member 80 has an inner diameter smaller than the maximum outer diameter of the lower closure section 212. By abutting the ring member 80 against the lower closure section 212 from below, the ring member 80 is positioned to follow the hemispherical outer surface of the lower closure section 212. The ring member 80 is fixed to the lower closure section 212, for example, by welding or using appropriate fittings. The ring member 80 is also connected to the support frame 70 using bolts or the like. The configuration of the support frame 70 and the ring member 80 can be changed as appropriate.

[0035] Figure 6 shows the state in which the bottomed cylindrical member is being cut vertically during the step of cutting the bottomed cylindrical member in the dismantling method for the bottomed cylindrical member according to the embodiment. In step S12, which involves cutting the reactor vessel body 21, as shown in Figure 6, the reactor vessel body 21 is cut from the inside of the reactor vessel body 21 above the water level Wf in the reactor vessel body 21. In order to cut the reactor vessel body 21 in step S12, it is preferable to adjust the height of the table 330 so that the second cutting disc 361 of the second disc saw 360 is at the same height as the position Q where the body portion 211 is cut in the circumferential direction Dh.

[0036] Figure 7 is a plan view showing the state in which the bottomed cylindrical member is being cut vertically in the step of cutting the bottomed cylindrical member in the dismantling method for the bottomed cylindrical member according to the embodiment. To cut the reactor vessel body 21, first, at cutting position K, the body 211 is cut vertically in the direction Dv using the first disc saw 350. To do this, the table 330 (see Figure 6) is rotated in the circumferential direction Dh, and the first cutting disc 351 is aligned with the first cutting position K1 among the multiple cutting positions K. As shown in Figure 6, the first disc saw 350 is raised along the guide 353 so that the first cutting disc 351 is positioned above the upper end of the body 211. Next, while rotating the first cutting disc 351, the first disc saw 350 is lowered along the guide 353, and at the first cutting position K1, the body portion 211 is cut vertically in the direction Dv to a position Q a predetermined distance below the upper end of the body portion 211. After that, the first disc saw 350 is raised along the guide 353, and the first cutting disc 351 is returned to a position above the upper end of the body portion 211.

[0037] Next, the table 330 is rotated in the circumferential direction Dh to align the first cutting disc 351 with the second cutting position K2, which is adjacent to the first cutting position K1 on one side in the circumferential direction Dh among the multiple cutting positions K. Subsequently, while rotating the first cutting disc 351 in the same manner as at the first cutting position K1, the first disc saw 350 is lowered along the guide 353 to cut the body 211 vertically in the direction Dv to a position Q a predetermined dimension below the upper end of the body 211. After that, the first disc saw 350 is raised along the guide 353 to return the first cutting disc 351 to a position above the upper end of the body 211.

[0038] Figure 8 shows the step of cutting a bottomed cylindrical member in the circumferential direction in the dismantling method of a bottomed cylindrical member according to the embodiment. Next, the table 330 is rotated in the circumferential direction Dh, so that the second cutting disc 361 of the second disc saw 360 faces radially into the region between the first cutting position K1 and the second cutting position K2. Also, as shown in Figure 8, the gripping portion 372 of the gripping member 370 is lowered to grip the upper end of the body portion 211 between the first cutting position K1 and the second cutting position K2.

[0039] Figure 9 is a plan view showing the state in which the bottomed cylindrical member is being cut in the circumferential direction during the step of cutting the bottomed cylindrical member in the dismantling method for the bottomed cylindrical member according to the embodiment. Next, as shown in Figure 9, while rotating the second cutting disc 361, the second disc saw 360 is moved radially outward, and the table 330 is rotated in the circumferential direction Dh, so that the body portion 211 is cut in the circumferential direction Dh between the first cutting position K1 and the second cutting position K2 at a position Q (see Figure 8) a predetermined distance below the upper end of the body portion 211.

[0040] In this case, the second disc saw 360 may, for example, be moved radially outward at the first cutting position K1 to cut into the body portion 211 with the second cutting disc 361, and then moved together with the table 330 to one side in the circumferential direction Dh, thereby continuously cutting the body portion 211 in the circumferential direction Dh up to the second cutting position K2.

[0041] Figure 10 is a plan view showing one of the steps in the process of cutting a bottomed cylindrical member in the circumferential direction in the dismantling method for a bottomed cylindrical member according to the embodiment. Figure 11 is a diagram showing the state following Figure 10. Alternatively, the second disc saw 360 may be moved radially outward at the first cutting position K1, for example, to cut into the body portion 211 with the second cutting disc 361, and then moved back radially inward. In this case, as shown in Figure 10, the second disc saw 360 is then moved radially outward at the second cutting position K2 to cut the body portion 211 with the second cutting disc 361, and then moved back radially inward. Furthermore, as shown in Figure 11, at an intermediate position between the first cutting position K1 and the second cutting position K2, the second disc saw 360 is moved radially outward to cut the body portion 211 with the second cutting disc 361, and then moved back radially inward. In this way, the body portion 211 may be cut in the circumferential direction Dh by cutting it at multiple different locations in the circumferential direction Dh.

[0042] By cutting the body portion 211 in this manner, the first cut piece 215 is obtained between the first cutting position K1 and the second cutting position K2. As shown in Figure 8, the obtained cut piece 215 is held by the gripping member 370, which prevents the cut piece 215 from falling unintentionally.

[0043] In step S13, which involves transporting the cut pieces 215 to the outside of the reactor vessel body 21, the cut pieces 215 generated by cutting the reactor vessel body 21 are transported to the outside of the reactor vessel body 21. The cut pieces 215, which are gripped by the gripping part 372, are transported to the outside of the reactor vessel body 21 by raising the gripping part 372 and extending the arm 371 radially outward. The transported cut pieces 215 are stored in, for example, a waste container (not shown).

[0044] After obtaining the first cut piece 215 through the above steps S11 to S13, the process returns to step S12, which involves cutting the reactor vessel body 21, and the shell portion 211 is cut to obtain the second cut piece 215. To do this, first, the table 330 is rotated in the circumferential direction Dh, and the first cutting disc 351 is aligned with the third cutting position K3, which is adjacent to the second cutting position K2 on one side in the circumferential direction Dh, among the multiple cutting positions K. Next, similar to the first and second cutting positions K2, the shell portion 211 is cut vertically in the direction Dv by the first disc saw 350 to a position Q a predetermined distance below the upper end of the shell portion 211. After that, the first disc saw 350 is raised along the guide 353 and returned to its original position.

[0045] Next, the table 330 is rotated in the circumferential direction Dh, so that the second cutting disc 361 of the second disc saw 360 faces radially into the region between the second cutting position K2 and the third cutting position K3. Also, the gripping portion 372 of the gripping member 370 is lowered to grip the upper end of the body portion 211 between the second cutting position K2 and the third cutting position K3.

[0046] Next, the second disc saw 360 cuts the body 211 in the circumferential direction Dh at a position Q a predetermined distance below the upper end of the body 211, between the second cutting position K2 and the third cutting position K3.

[0047] By cutting the torso 211 in this manner, the second cut piece 215 is obtained between the second cutting position K2 and the third cutting position K3. The obtained cut pieces 215 are removed to the outside of the reactor vessel body 21 in step S13, which is the process of removing the cut pieces 215 to the outside of the reactor vessel body 21.

[0048] Subsequently, the process S12 of cutting the reactor vessel body 21 and the process S13 of transporting the cut pieces 215 to the outside of the reactor vessel body 21 are repeated, and the third and subsequent cut pieces 215 are sequentially cut and transported along the entire circumference Dh of the body 211.

[0049] Once the cutting and removal of multiple cut pieces 215 along the entire circumference Dh of the hull 211 is complete, the position of the upper end of the hull 211 will be lowered. In this state, step S14 is performed to lower the water level Wf.

[0050] Figure 12 shows the step of lowering the water level in the dismantling method for a bottomed cylindrical member according to the embodiment. As shown in Figure 12, in step S14, which lowers the water level Wf, the water inside the reactor vessel body 21 is lowered to a predetermined dimension below the water level Wf using a submersible pump (not shown) or the like. In step S14, the support member 340 is moved downward as needed. To move the support member 340 downward, the multiple actuators 342 are retracted radially inward, the support member 340 is moved downward, and then the multiple actuators 342 are extended radially outward again to abut against the inner circumferential surface of the body 211. Subsequently, the table 330 is moved downward by a predetermined distance so that the second cutting disc 361 of the second disc saw 360 is at the same height as the next position Q where the body portion 211 is cut in the circumferential direction Dh.

[0051] Then, in the same manner as described above, the process S12 of cutting the reactor vessel body 21 and the process S13 of transporting the cut pieces 215 to the outside of the reactor vessel body 21 are repeated, and multiple cut pieces 215 are cut and transported along the entire circumference Dh of the body 211.

[0052] Subsequently, the body section 211 is dismantled by repeatedly performing the steps of lowering the water level Wf (S14), cutting the reactor vessel body 21 (S12), and transporting the cut pieces 215 to the outside of the reactor vessel body 21 (S13), thereby cutting out multiple pieces 215 along the entire circumference of the circumferential direction Dh.

[0053] (Effects and Benefits) In the dismantling method S10 of the bottomed cylindrical member of the above embodiment, the reactor vessel body 21 is dismantled by cutting it from the inside while it is still installed in the concrete hole 15. Therefore, compared to the case where the reactor vessel body 21 is removed from the concrete hole 15 before dismantling, the need to separately prepare space for the dismantling work is reduced. In addition, the reactor vessel body 21 is filled with water and cut above the water level Wf. Therefore, at least a portion of the metal shavings generated during cutting sinks in the water. By performing the cutting work with water inside the reactor vessel body 21, the dismantling work of the reactor vessel body 21 can be carried out while suppressing the effects of radiation exposure from the inner surface of the reactor vessel body 21, especially when the radioactivity level inside the reactor vessel body 21 is high. As a result, the dismantling of the reactor vessel body 21 can be carried out efficiently while suppressing the effects of radioactivity. Furthermore, by cutting the reactor vessel body 21 within the concrete hole 15, the shielding effect of the concrete structure can be effectively utilized to reduce exposure to the public and workers from the outer surface of the reactor vessel body 21.

[0054] Furthermore, in the above embodiment, while draining the water from the reactor vessel body 21 to lower the water level Wf, the portion of the reactor vessel body 21 above the lowered water level Wf is cut, and the cut pieces 215 are transported to the outside. With this configuration, the dismantling work of the reactor vessel body 21 can be carried out smoothly while exposing the minimum portion of the reactor vessel body 21 to be cut above the water level Wf.

[0055] Furthermore, in step S12 of the above embodiment for cutting the reactor vessel body 21, the reactor vessel body 21 is cut vertically at multiple cutting positions K spaced apart in the circumferential direction Dh, and also cut in the circumferential direction Dh between adjacent cutting positions K in the circumferential direction Dh. With this configuration, the cut pieces 215 generated by cutting the reactor vessel body 21 are rectangular plates curved in an arc shape. Therefore, it is easy to standardize the shape and size of the cut pieces 215, and compared to cases where cut pieces 215 of various shapes and sizes are obtained, the handling and disposal of the cut pieces 215 are easier. In the dismantling of the reactor vessel body 21, it is advantageous from the perspective of working time to carry out the primary cutting, which involves cutting the vessel into pieces of a certain size, and the secondary cutting, which involves cutting the divided pieces into pieces small enough to fit into the waste container, in parallel at different locations. However, the primary and secondary cutting require the placement of the dismantled material pieces in their respective work areas. Therefore, if these primary and secondary cuttings are carried out in the air, the combined exposure from both sources of radioactivity will result in an excessively large amount of radiation exposure, raising concerns about the impact on the public and workers. In contrast, in the above embodiment, it is possible to cut the reactor vessel body 21 into secondary cut pieces that can be stored in the waste container within the concrete hole 15, thereby reducing the impact on the public and workers as described above. Furthermore, in the dismantling apparatus 300 of the above embodiment, the cut pieces 215 obtained by cutting the bottomed cylindrical member 21 can be clamped by the gripping member 370, making it easy to transport out the cut pieces 215. Furthermore, in the demolition device 300 of the above embodiment, multiple actuators 342 can be extended radially outward and abut against the inner circumferential surface of the bottomed cylindrical member 21. Therefore, it is possible to prevent the column member 320 from accurately positioning the demolition device 300 relative to the bottomed cylindrical member 21 which extends in the vertical direction Dv.

[0056] (Other embodiments) Although embodiments of this disclosure have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments and may include design changes and the like that do not depart from the gist of this disclosure. In the above embodiment, the torso 211 is dismantled using the first disc saw 350, the second disc saw 360, and the gripping member 370, but the configuration of the equipment used to dismantle the torso 211 can be changed as appropriate.

[0057] The steps in the above dismantling method S10 for the bottomed cylindrical member can be rearranged as appropriate. For example, the body portion 211 may be cut in the circumferential direction Dh, and then the body portion 211 may be cut in the vertical direction Dv to obtain the cut piece 215.

[0058] Furthermore, in the above embodiment, the shell portion 211 of the reactor vessel 2 was dismantled using the dismantling method S10 for the bottomed cylindrical member. However, the method is not limited to this, and the same dismantling method S10 for the bottomed cylindrical member can also be applied when dismantling the shell portions of other equipment such as pressurizers and steam generators installed in the reactor containment vessel.

[0059] Furthermore, the above-described case of the dismantling device 300 being installed inside the reactor vessel body 21 has been explained. However, the dismantling device 300 is not limited to being installed inside the reactor vessel body 21.

[0060] Furthermore, the demolition device 300 has been described in a way that includes a base 310 and column members 320, and supports the table 330 from below. However, the demolition device 300 is not limited to this method. For example, the demolition device 300 may be one in which the table 330 is not supported from below, but is lifted from above.

[0061] <Note> The dismantling method S10 and dismantling apparatus 300 for the bottomed cylindrical member 21 described in the embodiment can be understood, for example, as follows.

[0062] (1) A dismantling method S10 for a bottomed cylindrical member 21 according to the first embodiment is a dismantling method S10 for a bottomed cylindrical member 21 provided in a reactor containment vessel and having a body portion 211 extending in the vertical direction and a lower closing portion 212 that closes the lower end of the body portion 211, and includes a step S11 of filling the bottomed cylindrical member 21 installed in a concrete hole 15 with water; a step S12 of cutting the bottomed cylindrical member 21 from the inside of the bottomed cylindrical member 21 above the water level Wf in the bottomed cylindrical member 21; and a step S13 of transporting the cut pieces 215 generated by cutting the bottomed cylindrical member 21 to the outside of the bottomed cylindrical member 21. Examples of bottomed cylindrical members 21 include reactor vessels, pressurizers, and steam generators installed inside the reactor containment vessel.

[0063] This dismantling method S10 for the bottomed cylindrical member 21 involves cutting the bottomed cylindrical member 21 from the inside while it remains installed in the concrete hole 15. Therefore, compared to the method where the bottomed cylindrical member 21 is removed from the concrete hole before dismantling, the need to prepare a separate space for the dismantling work is reduced. Furthermore, the bottomed cylindrical member 21 is filled with water, and cut above the water level Wf. As a result, at least some of the metal shavings generated during cutting sink into the water. By performing the cutting work with water inside the bottomed cylindrical member 21, the dismantling work can be carried out smoothly while minimizing the effects of radioactivity, especially when the radioactivity level inside the bottomed cylindrical member 21 is high. As a result, the dismantling of the bottomed cylindrical member 21 can be carried out efficiently while minimizing the effects of radioactivity.

[0064] (2) The dismantling method S10 for the bottomed cylindrical member 21 according to the second embodiment is the dismantling method S10 for the bottomed cylindrical member 21 according to (1), further comprising the step S14 of draining the water from inside the bottomed cylindrical member 21 and lowering the level of the water surface Wf, and repeating the step S12 of cutting the bottomed cylindrical member 21 in the portion above the lowered level of the water surface Wf, and the step S13 of transporting the cut piece 215 to the outside of the bottomed cylindrical member 21.

[0065] This allows for efficient dismantling of the bottomed cylindrical member 21 while exposing the minimum portion of the bottomed cylindrical member 21 that is to be cut above the water surface Wf.

[0066] (3) A dismantling method S10 for a bottomed cylindrical member 21 according to the third embodiment is the dismantling method S10 for a bottomed cylindrical member 21 according to (1) or (2), wherein in the step S12 for cutting the bottomed cylindrical member 21, the bottomed cylindrical member 21 is cut in the vertical direction Dv at a plurality of cutting positions K spaced apart in the circumferential direction of the bottomed cylindrical member 21, and the bottomed cylindrical member 21 is cut in the circumferential direction Dh between adjacent cutting positions K in the circumferential direction Dh.

[0067] As a result, the cut pieces 215 generated by cutting the bottomed cylindrical member 21 are rectangular plates that are curved in an arc shape. Therefore, it is easy to standardize the shape and size of the cut pieces 215, and compared to cases where cut pieces 215 of various shapes and sizes are obtained, the handling and disposal of the cut pieces 215 are easier.

[0068] (4) The dismantling apparatus 300 according to the fourth embodiment is a dismantling apparatus 300 used in the method for dismantling a bottomed cylindrical member described in any one of (1) to (3), and comprises: a first disc saw 350 having a first cutting disc 351 that is disc-shaped and located in a vertical plane extending radially around the axis of the bottomed cylindrical member 21 and capable of cutting the bottomed cylindrical member 21; a second disc saw 360 having a second cutting disc 361 that is disc-shaped and located in a horizontal plane intersecting the vertical direction Dv and capable of cutting the bottomed cylindrical member 21 from the inside; and a table 330 that supports the first disc saw 350 and the second disc saw 360 so as to be movable in the circumferential direction around the axis of the bottomed cylindrical member 21.

[0069] This makes it possible to cut the bottomed cylindrical member 21 and to cut the bottomed cylindrical member 21 into a rectangular plate-shaped cut piece 215 that is curved in an arc shape.

[0070] (5) The dismantling device 300 according to the fifth embodiment is the dismantling device 300 of (4), further comprising a gripping member 370 capable of clamping the upper end of the bottomed cylindrical member 21 from both sides in the radial direction centered on the axis.

[0071] This allows the cut pieces 215 obtained by cutting the bottomed cylindrical member 21 to be clamped by the gripping member 370, making it easy to transport the cut pieces 215.

[0072] (6) The dismantling device 300 according to the sixth embodiment is the dismantling device 300 of (4) or (5), further comprising a support member 340 that is supported on the inner circumferential surface of the bottomed cylindrical member 21 and is positionable with respect to the inner circumferential surface, the support member 340 comprising a base member 341 that extends radially outward from the axis of the bottomed cylindrical member 21, and a plurality of actuators 342 that are spaced apart in the circumferential direction from the base member 341 and are extendable and retractable in the radial direction.

[0073] This allows multiple actuators 342 to be extended radially outward and abut against the inner circumferential surface of the closed-bottom cylindrical member 21. Therefore, the dismantling device 300 can be precisely positioned relative to the closed-bottom cylindrical member 21 that extends in the vertical direction Dv. [Explanation of symbols]

[0074] 1… Pressurized water reactor 2…Reactor vessel 3…Control rod drive mechanism 5…Upper core structure 6…Lower core structure 15…Concrete hole 21...Reactor vessel body (bottomed cylindrical member) 22...Reactor vessel lid 23... Inlet nozzle 24…Outlet nozzle 51…Upper core plate 52…Upper core support plate 53… Upper core support column 55... Guide tube 70… Stand 80... Ring component 100... Pool inside the reactor building 110... First Cavity 111...First floor 113...Third floor 120...Second cavity 121…Second floor surface 211... Torso 212…Lower obstruction part 212t…protrusion 215...Cut piece 300...Demolition equipment 310...bass 312… Fixing member 313…Upper fixing member 314...Lower fixing member 320...Column member 330... Table 331...Cylindrical part 332... Table body 340...Support member 341...Base member 342… Actuator 350... First Disc Saw 351...First Disk 353... Guide 360... Second disc saw 361...Second Disk 363… Guide 370... Gripping member 371... Arm 372...Gripping part Wf…Water surface

Claims

1. A method for dismantling a bottomed cylindrical member provided in a pool inside the reactor building of a pressurized water reactor, installed in a concrete hole formed by a recess below the floor surface formed in the cavity of the pool inside the reactor building, having a body portion extending in the vertical direction and a lower closing portion that closes the lower end of the body portion, With the bottomed cylindrical member installed in the concrete hole, the process involves filling the bottomed cylindrical member with water, The process involves cutting the bottomed cylindrical member from the inside of the bottomed cylindrical member above the water surface in the bottomed cylindrical member, A step of transporting the cut pieces generated by cutting the bottomed cylindrical member to the outside of the bottomed cylindrical member, A method for dismantling a bottomed cylindrical member, including the member in question.

2. The process further includes the step of draining the water from the bottomed cylindrical member and lowering the water level, The process of cutting the bottomed cylindrical member and transporting the cut piece to the outside of the bottomed cylindrical member is repeated in the portion above the lowered water level. A method for dismantling a bottomed cylindrical member as described in claim 1.

3. In the step of cutting the bottomed cylindrical member, the bottomed cylindrical member is cut vertically at multiple cutting positions spaced apart in the circumferential direction, and the bottomed cylindrical member is cut circumferentially between adjacent cutting positions in the circumferential direction. A method for dismantling a bottomed cylindrical member according to claim 1 or 2.

4. A dismantling device used in the method for dismantling a bottomed cylindrical member as described in claim 1, A first disc saw having a disc-shaped first cutting disc that is located in a vertical plane extending radially around the axis of the bottomed cylindrical member and capable of cutting the bottomed cylindrical member, A second disc saw having a disc-shaped second cutting disc located in a horizontal plane intersecting the vertical direction, capable of cutting the bottomed cylindrical member, A table that supports the first disc saw and the second disc saw so that they can move in the circumferential direction about the axis of the bottomed cylindrical member, A demolition device equipped with the following features.

5. The upper end of the bottomed cylindrical member is further provided with gripping members that can be clamped from both sides in the radial direction around the axis. The dismantling apparatus according to claim 4.

6. The bottomed cylindrical member further comprises a support member that is supported on the inner circumferential surface and is positionable relative to the inner circumferential surface, The support member comprises a base member extending radially outward from the axis of the bottomed cylindrical member, and a plurality of actuators provided at intervals in the circumferential direction from the axis of the bottomed cylindrical member, which are extendable and retractable radially from the base member. The dismantling apparatus according to claim 4 or 5.

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