Method for cutting a bottomed cylindrical member
The described method efficiently cuts and dismantles reactor vessels by containing chips within the vessel, addressing inefficiencies and contamination risks in existing disassembly methods.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- MITSUBISHI HEAVY IND LTD
- Filing Date
- 2025-12-23
- Publication Date
- 2026-06-26
AI Technical Summary
The disassembly of high-level radioactive bottomed cylindrical members, such as reactor vessels, is inefficient due to the scattering of chips during cutting, leading to decreased efficiency and potential contamination spread.
A method involving a disc saw that rotates and cuts the cylindrical member by transitioning its outer circumference in specific rotational and feed directions, ensuring chips fall into the reactor vessel, reducing scattering and facilitating easy collection.
The method enhances the efficiency of dismantling the reactor vessel by containing chips within the vessel, minimizing contamination spread and reducing the need for chip collection, while also reducing worker exposure to radiation.
Smart Images
Figure 0007881034000001_ABST
Abstract
Description
Technical Field
[0001] The present disclosure relates to a method for cutting a bottomed cylindrical member.
Background Art
[0002] Patent Document 1 discloses a technique for disassembling an in-vessel structure in a reactor vessel in water stored in a working pool and carrying out the disassembled in-vessel structure from the working pool with respect to 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, operations such as collecting the chips scattered during cutting occur, and there is a problem that the disassembly efficiency of the bottomed cylindrical member decreases.
[0005] The present disclosure has been made to solve the above problems, and an object thereof is to provide a method for cutting a bottomed cylindrical member capable of efficiently disassembling the bottomed cylindrical member.
Means for Solving the Problems
[0006] To solve the above problems, the method for cutting a bottomed cylindrical member according to the present disclosure is a method for cutting a bottomed cylindrical member provided in a reactor containment vessel, 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 cutting the bottomed cylindrical member includes the steps of rotating a cutting disc and cutting the body portion. In the step of rotating the cutting disc, a disc saw is driven to rotate the cutting disc of the disc saw. In the step of cutting the body portion, the disc saw is fed along the surface of the body portion with the cutting disc penetrating the body portion to cut the body portion. In the step of rotating the cutting disc, in the step of cutting the body portion, the outer circumference of the cutting disc in contact with the body portion is driven in a rotational direction that transitions in the following order: radially outward of the bottomed cylindrical member, forward in the feeding direction of the disc saw, radially inward of the bottomed cylindrical member, and rearward in the feeding direction of the disc saw. Then, in the process of cutting the body, the disc saw driven by the process of rotating the cutting disc is moved forward in the feed direction to cut the body, while scattering the cutting chips from the body radially inward. . [Effects of the Invention]
[0007] According to the method for cutting a bottomed cylindrical member of this disclosure, the bottomed cylindrical member can be dismantled efficiently. [Brief explanation of the drawing]
[0008] [Figure 1] This is a longitudinal cross-sectional view showing a pressurized water reactor, which is the reactor to be dismantled according to this embodiment. [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 to be cut by the reactor vessel cutting method according to the embodiment. [Figure 4] This figure shows a method for cutting a bottomed cylindrical member according to an embodiment, in which the disc saw is positioned radially inside the bottomed cylindrical member. [Figure 5] This is a flowchart showing a method for cutting a bottomed cylindrical member according to an embodiment. [Figure 6]This figure shows the state in which a disc saw is brought into contact with the inner circumferential surface of a bottomed cylindrical member in a method for cutting a bottomed cylindrical member according to the embodiment. [Figure 7] This figure shows the state in which the cutting disc of the disc saw penetrates the bottomed cylindrical member during the cutting method of the bottomed cylindrical member according to the embodiment. [Figure 8] This figure shows a method for cutting a bottomed cylindrical member according to an embodiment, in which a disc saw is positioned radially inward of the bottomed cylindrical member in order to cut the bottomed cylindrical member in the circumferential direction. [Figure 9] This figure shows a state in which a disc saw is brought into contact with the inner circumferential surface of a bottomed cylindrical member in order to cut the bottomed cylindrical member in the circumferential direction, according to the method for cutting a bottomed cylindrical member according to the embodiment. [Figure 10] This figure shows the state in which the cutting disc of a disc saw penetrates the bottomed cylindrical member in order to cut the bottomed cylindrical member in the circumferential direction, according to the method for cutting a bottomed cylindrical member according to the embodiment. [Figure 11] This figure shows a state in which the cutting disc of a disc saw penetrates the bottomed cylindrical member and cuts the bottomed cylindrical member in a method for cutting a bottomed cylindrical member according to a modified embodiment. [Modes for carrying out the invention]
[0009] The following describes embodiments for implementing the method for cutting a bottomed cylindrical member according to this disclosure, with reference to the attached drawings. However, this disclosure is not limited to these embodiments.
[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] As shown in Figure 2, the pressurized water reactor 1 is located in a reactor building pool 100, which is provided within the reactor building (not shown). The reactor building pool 100 has a space where cooling water (water) can be stored. In this embodiment, the reactor building pool 100 has a first cavity 110 in which the pressurized water reactor 1 is located, and a second cavity 120 located adjacent to the first cavity 110. The first cavity 110 has a first floor surface 111 that workers can walk on. 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 more than a vertical Dv below the first floor surface 111. As a result, the second cavity 120 is formed as a space that is recessed vertically Dv lower than the first cavity 110.
[0012] As shown in Figures 1 and 2, the pressurized water reactor 1 of this embodiment comprises a reactor vessel 2, a control rod drive unit 3 (see Figure 1), an upper core structure 5, and a lower core structure 6.
[0013] The reactor vessel 2 has a reactor vessel body (bottomed cylindrical member) 21 and a reactor vessel lid 22 (upper mirror) so that internal reactor structures can be inserted inside. The reactor vessel 2 is positioned inside a hole formed to be recessed from the first floor surface 111. The reactor vessel 2 is positioned so that a portion of it (specifically the reactor vessel lid 22) protrudes from the first floor surface 111.
[0014] The reactor vessel body 21 is configured such that its upper part can be opened by removing the reactor vessel head 22. The reactor vessel body 21 integrally includes a cylindrical body portion 211 and a lower closing portion 212. The body portion 211 is formed in a cylindrical shape extending in the vertical direction Dv. The lower closing portion 212 closes the lower end of the body portion 211. The lower closing portion 212 is a lower mirror having a hemispherical shape.
[0015] At the upper part of the reactor vessel body 21, an inlet nozzle 23 (inlet pipe support) for supplying light water (coolant) as primary cooling water (water) and an outlet nozzle 24 (outlet pipe support) for discharging the light water are formed. Further, the reactor vessel body 21 has a water injection nozzle (water injection pipe support), not shown in the figure, separately from the inlet nozzle 23 and the outlet nozzle 24.
[0016] The reactor vessel head 22 is attached to the upper part of the reactor vessel body 21. The reactor vessel head 22 is fixedly attached to the reactor vessel body 21 by a plurality of stud bolts and nuts (not shown) so as to be openable and closable.
[0017] The upper core structure 5 is disposed inside the reactor vessel 2. The upper core structure 5 can be withdrawn from the reactor vessel body 21 by being moved upward in the vertical direction Dv with respect to the reactor vessel body 21. The upper core structure 5 of the present embodiment includes 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, not shown, such as, for example, a mixer, a thermocouple lead-out tube, and a reinforcing beam.
[0018] 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.
[0019] (Method for cutting the reactor vessel) The following describes a method for cutting 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 cutting method according to the embodiment. As shown in Figure 3, the reactor vessel body 21 is cut into multiple pieces. In this embodiment, the torso 211 of the reactor vessel body 21 is cut into multiple pieces 215. The cutting of the reactor vessel body 21 is carried out while the reactor vessel body 21 remains installed in 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 the lower core structure 6 have been removed from inside the reactor vessel body 21. Here, the method for removing the upper core structure 5 and the lower core structure 6 from inside the reactor vessel body 21 is not limited in any way and may be carried out by an appropriate method.
[0020] As shown in Figure 3, when cutting the reactor vessel body 21, the shell portion 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 a plurality of cutting positions K spaced apart in the circumferential direction Dh, and then the shell portion 211 is cut in the circumferential direction Dh at a position Q a predetermined distance below the upper end of the shell portion 211, between adjacent cutting positions K in the circumferential direction Dh. As a result, one cut piece 215 is cut out from the shell portion 211. The cut piece 215 is stored in a waste container (not shown) and transported out of the reactor building as appropriate.
[0021] Figure 4 shows a state in which a disc saw is positioned radially inside the bottomed cylindrical member in the method for cutting a bottomed cylindrical member according to the embodiment. A disc saw 200 is used to cut the torso 211. The disc saw 200 comprises a cutting disc 201 and a disc saw body (not shown). The cutting disc 201 is disc-shaped 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 cutting disc 201. The disc saw body is supported by an appropriate disc saw support (not shown) so as to be movable relative to the reactor vessel body 21.
[0022] The cutting of the reactor vessel body 21 is carried out with water stored inside the reactor vessel body 21. When cutting the body portion 211 of the reactor vessel body 21, the disc saw 200 is positioned above the water level Wf inside the reactor vessel body 21. Therefore, if necessary, the water stored inside the reactor vessel body 21 is drained so that the position Q where the body portion 211 is cut in the circumferential direction Dh is above the water level Wf inside the reactor vessel body 21.
[0023] Figure 5 is a flowchart showing a method S10 for cutting the reactor vessel body 21 according to the present disclosure. When cutting the body 211 in the vertical direction Dv and the circumferential direction Dh using a disc saw 200, the following reactor vessel body cutting method S10 is performed. As shown in Figure 5, the method S10 for cutting the reactor vessel body 21 includes the steps of: positioning the disc saw 200 in step S11; rotating the cutting disc 201 in step S12; and cutting the body portion 211 in step S13.
[0024] (When cutting the torso vertically) When cutting the body portion 211 in the vertical direction Dv, in step S11, the disc saw 200 is positioned on the inside of the body portion 211 in the radial direction Dr, as shown in Figure 4.
[0025] In step S12, which involves rotating the cutting disc 201, the drive source (motor) of the disc saw 200 is driven to rotate the cutting disc 201 of the disc saw 200 in a predetermined rotational direction R1 around a drive shaft (not shown) that supports the cutting disc 201. The rotational direction R1 is preferably set so that the cutting disc 201 transitions from top to bottom in the portion of its outer circumference facing the body 211, so that the chips generated when the cutting disc 201 cuts the body 211 in step S13 are sent flying downwards.
[0026] Figure 6 shows the state in which the disc saw is brought into contact with the inner circumferential surface of the bottomed cylindrical member in the method for cutting the bottomed cylindrical member according to the embodiment. Figure 7 shows the state in which the bottomed cylindrical member is cut with the cutting disc of the disc saw penetrating the bottomed cylindrical member in the method for cutting the bottomed cylindrical member according to the embodiment. In step S13, which involves cutting the body portion 211, the body portion 211 is cut in the vertical direction Dv. In step S13, first, as shown in Figure 6, the disc saw 200, which is positioned inside the radial direction Dr of the body 211, is moved to the outside of the radial direction Dr, and the cutting disc 201, which is rotated in the rotational direction R1, cuts into the inner circumferential surface 211f of the body 211 toward the outside of the radial direction Dr. At this time, the metal shavings Z from the body 211 being cut by the cutting disc 201 are scattered from the body 211 toward the front (downward) in the rotational direction R1 of the cutting disc 201 toward the inside of the radial direction Dr of the body 211, and fall into the reactor vessel body 21 by their own weight.
[0027] As shown in Figure 7, by moving the disc saw 200 further outward in the radial direction Dr, the cutting disc 201 penetrates the body 211. After the cutting disc 201 has penetrated the body 211, the movement of the disc saw 200 outward in the radial direction Dr is stopped. Next, with the cutting disc 201 having penetrated the body 211, the disc saw 200 is fed along the surface of the body 211. At this time, the feed direction M1 of the disc saw 200 is the vertical direction Dv. In Figure 7, the feed direction M1 of the disc saw 200 is vertically downward.
[0028] In this configuration, the outer circumference of the cutting disc 201, which rotates in rotational direction R1 and contacts the body portion 211, transitions in the following order: position P11 on the radially outside Dr of the reactor vessel body 21, position P12 on the forward (downward) side in the feed direction of the disc saw 200, position P13 on the radially inside Dr of the reactor vessel body 21, and position P14 on the rear (upward) side in the feed direction of the disc saw 200. In other words, in step S12, which rotates the cutting disc 201, in step S13, which cuts the body portion 211, the outer circumference of the cutting disc 201 that contacts the body portion 211 moves in the following order: position P11 outside the radial Dr of the reactor vessel body 21, position P12 forward in the feed direction of the disc saw 200, position P13 inside the radial Dr of the reactor vessel body 21, and position P14 backward in the feed direction of the disc saw 200.
[0029] In step S13, the disc saw 200 is fed downward along the feed direction M1, and the cutting disc 201, which rotates in the rotation direction R1, cuts the body 211 in the vertical direction Dv. After cutting the body 211 in the vertical direction Dv, the disc saw 200 is moved in the circumferential direction Dh of the body 211, and steps S11 to S13 are repeated at other cutting positions K.
[0030] (When cutting the torso in the circumferential direction Dh) Figure 8 shows a state in which a disc saw is positioned radially inward of a bottomed cylindrical member in order to cut the bottomed cylindrical member in the circumferential direction, according to the method for cutting a bottomed cylindrical member according to the embodiment. In step S11, which involves positioning the disc saw 200, the disc saw 200 is positioned at a predetermined location relative to the reactor vessel body 21, as shown in Figure 8. In this embodiment, the disc saw 200 is positioned inside the radial Dr of the body portion 211 of the reactor vessel body 21.
[0031] In step S12, which involves rotating the cutting disc 201, the drive source (motor) of the disc saw 200 is driven to rotate the cutting disc 201 of the disc saw 200 in a predetermined rotational direction R2 around a drive shaft (not shown) that supports the cutting disc 201.
[0032] Figure 9 shows the state in which a disc saw is brought into contact with the inner circumferential surface of a bottomed cylindrical member in order to cut the bottomed cylindrical member in the circumferential direction, in the cutting method of a bottomed cylindrical member according to the embodiment. Figure 10 shows the state in which the cutting disc of the disc saw penetrates the bottomed cylindrical member in order to cut the bottomed cylindrical member in the circumferential direction, in the cutting method of a bottomed cylindrical member according to the embodiment. In step S13, which cuts the body portion 211, first, as shown in Figure 9, the disc saw 200, which is positioned inside the radial direction Dr of the body portion 211, is moved to the outside of the radial direction Dr, and the cutting disc 201, which is rotated in the rotational direction R2, cuts into the inner circumferential surface 211f of the body portion 211 toward the outside of the radial direction Dr. At this time, the metal shavings Z from the body portion 211 being cut by the cutting disc 201 are scattered from the body portion 211 toward the front in the rotational direction R2 of the cutting disc 201 toward the inside of the radial direction Dr of the body portion 211, and fall into the reactor vessel body 21 by their own weight.
[0033] As shown in Figure 10, the cutting disc 201 penetrates the body 211 by moving the disc saw 200 further outward in the radial direction Dr. After the cutting disc 201 has penetrated the body 211, the movement of the disc saw 200 outward in the radial direction Dr is stopped. Subsequently, with the cutting disc 201 having penetrated the body 211, the disc saw 200 is fed along the surface of the body 211. The feed direction M2 of the disc saw 200 is one side of the circumferential direction Dh around the central axis C2 of the body 211. Here, the rotation direction R2 of the cutting disc 201 and the feed direction M2 of the disc saw 200 are in the same direction (for example, clockwise) when viewed from the vertical direction Dv.
[0034] In this configuration, the outer circumference of the cutting disc 201, which rotates in the rotational direction R2 and contacts the body portion 211, transitions in the following order: position P21 on the radially outside Dr of the reactor vessel body 21, position P22 on the forward side in the feed direction of the disc saw 200, position P23 on the radially inside Dr of the reactor vessel body 21, and position P24 on the rear side in the feed direction of the disc saw 200. In other words, in step S12, which rotates the cutting disc 201, in step S13, which cuts the body portion 211, the disc saw 200 is driven to rotate in a rotational direction R2 that transitions in the following order: position P21 outside the radial Dr of the reactor vessel body 21, position P22 forward in the feed direction of the disc saw 200, position P23 inside the radial Dr of the reactor vessel body 21, and position P24 backward in the feed direction of the disc saw 200.
[0035] In step S13, the disc saw 200 is fed in the feed direction M2, and the cutting disc 201, which rotates in the rotation direction R2, cuts the body portion 211 in the circumferential direction Dh around the central axis C2. As a result, the body portion 211 is cut in the circumferential direction Dh between adjacent cutting positions K in the vertical direction Dv, and the cut pieces 215 are cut out. The cut pieces 215 are stored in a waste container (not shown).
[0036] Next, the disc saw 200 is moved further in the circumferential direction Dh, and the body portion 211 is cut in the circumferential direction Dh between other adjacent cutting positions K in the circumferential direction Dh, sequentially cutting out multiple pieces 215.
[0037] Cuts are made in the vertical direction Dv and the circumferential direction Dh along the entire circumference of the body 211. After the cutting of multiple pieces 215 is complete, the position Q for cutting the body 211 in the vertical direction Dv and the circumferential direction Dh is sequentially moved downwards.
[0038] (Effects and Benefits) In the method S10 for cutting a bottomed cylindrical member according to the above embodiment, the outer circumference of the cutting disc 201 that contacts the body portion 211 drives the disc saw 200 in rotational directions R1 and R2, which transition in the following order: radially outside Dr of the reactor vessel body 21, forward in the feed direction of the disc saw 200, radially inside Dr of the reactor vessel body 21, and rear in the feed direction of the disc saw 200. With this configuration, the chips Z generated when the cutting disc 201 cuts the body portion 211 fall into the reactor vessel body 21. Therefore, the scattering of chips Z, which are often highly radioactive waste, outside the reactor vessel body 21 and the effort required to collect the chips are suppressed, and the collection of chips Z can be made easier. Thus, the dismantling of the reactor vessel body 21 can be performed efficiently. Furthermore, if the radioactive contaminants, the metal chips Z, were to scatter outside the less contaminated reactor vessel body 21, it would lead to the spread of contamination. However, since the metal chips Z can be discharged into the already contaminated reactor vessel body 21, this method offers an advantage in preventing the spread of contamination.
[0039] Furthermore, in the above embodiment, prior to the step S12 in which the cutting disc 201 is rotated, the disc saw 200 is positioned radially inward Dr of the reactor vessel body 21. As a result, when the cutting disc 201 is rotated, the cutting disc 201 does not penetrate the body 211. Even if the cutting disc 201 does not penetrate the body 211, the resulting chips fall into the reactor vessel body 21. Therefore, the chips Z can be easily collected, reducing the need for work such as collecting chips Z scattered outside the reactor vessel body 21, and enabling efficient dismantling of the reactor vessel body 21.
[0040] Furthermore, in the above embodiment, in step S13, which involves cutting the shell portion 211, the disc saw 200 is fed in the circumferential direction Dh of the shell portion 211, and the shell portion 211 is cut into multiple pieces in the vertical direction Dv. This configuration allows for easy collection of the chips Z while efficiently dismantling the reactor vessel body 21.
[0041] Furthermore, in the above embodiment, in step S13, which involves cutting the body portion 211, the disc saw 200 is fed in the vertical direction Dv, and the body portion 211 is cut into multiple pieces in the circumferential direction Dh. This configuration allows for easy collection of the chips Z while efficiently dismantling the reactor vessel body 21.
[0042] Furthermore, in the above embodiment, water is stored inside the reactor vessel body 21, and the torso 211 is cut by the disc saw 200 at a position above the water level Wf inside the reactor vessel body 21. This configuration allows the torso 211 to be cut while reducing the exposure of workers and the impact of exposure on the environment (public).
[0043] (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 disc saw 200 is positioned inside the radial direction Dr of the body portion 211, and the body portion 211 is cut from the inside of the radial direction Dr, but the embodiment is not limited to this.
[0044] Figure 11 shows a state in which the cutting disc of the disc saw penetrates the bottomed cylindrical member in a method for cutting a bottomed cylindrical member according to a modified embodiment. For example, as shown in Figure 11, the disc saw 200 may be positioned outside the radial direction Dr of the body 211, so that the body 211 is cut from the outside of the radial direction Dr. In this case, the cutting disc 201 of the disc saw 200 cuts into the body 211 from the outer surface 211t of the body 211 inward in the radial direction Dr, and until it penetrates the body 211, the chips from the body 211 are scattered to the outside of the body 211. However, when cutting the body portion 211 while the cutting disc 201 has penetrated the body portion 211 and the disc saw 200 is fed in the feed direction M3, the outer circumference of the cutting disc 201 in contact with the body portion 211 moves in the following order: position P31 on the radially outside Dr of the reactor vessel body 21, position P32 on the forward side in the feed direction of the disc saw 200, position P33 on the radially inside Dr of the reactor vessel body 21, and position P34 on the rear side in the feed direction of the disc saw 200. By driving the cutting disc 201 of the disc saw 200 in this rotation direction R3, the chips Z can be scattered toward the inside of the reactor vessel body 21 and fall into the reactor vessel body 21.
[0045] The steps for cutting the bottomed cylindrical member in the above embodiment and modified examples 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.
[0046] <Note> The cutting method S10 for the bottomed cylindrical member 21 described in the embodiment can be understood, for example, as follows.
[0047] (1) A cutting method S10 for a bottomed cylindrical member 21 according to the first embodiment is a cutting method S10 for a bottomed cylindrical member 21 provided inside 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, comprising the steps of driving a disc saw 200 and rotating the cutting disc 201 of the disc saw 200, and feeding the disc saw 200 along the surface of the body portion 211 with the cutting disc 201 penetrating the body portion 211 The process includes a step S13 for cutting the body portion 211, and in step S12 for rotating the cutting disc 201, in step S13 for cutting the body portion 211, the outer circumference of the cutting disc 201 that is in contact with the body portion 211 drives the disc saw 200 in rotational directions R1 to R3, which transition in the following order: radially outward Dr of the bottomed cylindrical member 21, forward in the feed direction of the disc saw 200, radially inward Dr of the bottomed cylindrical member 21, and rearward in the feed direction of the disc saw 200.
[0048] With this configuration, the metal shavings generated when the body section 211 is cut by the cutting disc 201 fall into the bottomed cylindrical member 21. Therefore, the scattering of metal shavings, which are often highly radioactive waste, outside the bottomed cylindrical member 21 and the effort required to collect them are suppressed, and the metal shavings can be easily collected. Consequently, the dismantling of the bottomed cylindrical member 21 can be performed efficiently. In addition, if the metal shavings Z, which are radioactive contaminants, are scattered outside the less contaminated reactor vessel body 21, it will lead to the spread of contamination. However, since the metal shavings Z can be discharged inside the already contaminated reactor vessel body 21, this configuration is also advantageous in preventing the spread of contamination.
[0049] (2) A cutting method S10 for a bottomed cylindrical member 21 according to a second embodiment is the cutting method S10 for a bottomed cylindrical member 21 according to (1), further comprising a step S11 of positioning the disc saw 200 radially inward Dr of the bottomed cylindrical member 21 prior to the step S12 of rotating the cutting disc 201.
[0050] As a result, when the cutting disc 201 is rotated, the cutting disc 201 does not penetrate the body portion 211, and even if the cutting disc 201 does not penetrate the body portion 211, the generated chips fall into the bottomed cylindrical member 21. Therefore, the chips can be easily collected, and the work required to collect the chips Z, which are often highly radioactive waste, is reduced, and the bottomed cylindrical member 21 can be dismantled efficiently.
[0051] (3) A third embodiment of the method S10 for cutting a bottomed cylindrical member 21 is the method S10 for cutting a bottomed cylindrical member 21 according to (1), further comprising a step S11 in which the disc saw 200 is positioned radially outward Dr of the bottomed cylindrical member 21 prior to the step S12 in which the cutting disc 201 is rotated.
[0052] As a result, when the cutting disc 201 is rotated, the chips generated will scatter outside the bottomed cylindrical member 21 until the cutting disc 201 penetrates the body 211. However, once the cutting disc 201 has penetrated the body 211, the chips will fall back into the bottomed cylindrical member 21. Therefore, the bottomed cylindrical member 21 can be dismantled efficiently.
[0053] (4) The cutting method S10 for the bottomed cylindrical member 21 according to the fourth embodiment is any one of the cutting methods S10 for the bottomed cylindrical member 21 from (1) to (3), wherein the step S13 for cutting the body portion 211 is to feed the disc saw 200 in the circumferential direction of the body portion 211 and cut the body portion 211 into multiple pieces in the vertical direction.
[0054] This makes it easy to collect the chips while efficiently dismantling the bottomed cylindrical member 21.
[0055] (5) The fifth method S10 for cutting a bottomed cylindrical member 21 is any one of the methods S10 for cutting a bottomed cylindrical member 21 from (1) to (4), wherein the step S13 for cutting the body portion 211 is to feed the disc saw 200 in the vertical direction and cut the body portion 211 into multiple pieces in the circumferential direction of the body portion 211.
[0056] This makes it easy to collect the chips while efficiently dismantling the bottomed cylindrical member 21.
[0057] (6) The sixth method S10 for cutting a bottomed cylindrical member 21 is any one of the methods S10 for cutting a bottomed cylindrical member 21 from (1) to (5), wherein the bottomed cylindrical member 21 is a reactor vessel 21, water is stored in the reactor vessel 21, and the water in the reactor vessel 21 is drained to a position above the water level in the reactor vessel 21, at which point the body portion 211 is cut with the disc saw 200.
[0058] This allows the body section 211 to be cut at a position above the water level Wf while water is stored inside the reactor vessel 21, thereby reducing radiation exposure to workers and minimizing the impact of radiation exposure on the environment. [Explanation of symbols]
[0059] 2…Reactor vessel 21...Reactor vessel body (bottomed cylindrical member) 200... Disc saw 201...Cutting disc 211... Torso 212…Lower obstruction part M1~M3...Feed direction R1~R3...Rotation direction Wf…Water surface
Claims
1. A method for cutting a bottomed cylindrical member provided inside a reactor containment vessel, having a body portion extending in the vertical direction and a lower closing portion that closes the lower end of the body portion, A step of driving the disc saw and rotating the cutting disc of the disc saw, The process of cutting the body by feeding the disc saw along the surface of the body while the cutting disc has penetrated the body, Includes, In the step of rotating the cutting disc, in the step of cutting the body portion, the disc saw is driven in a rotational direction in which the outer circumference of the cutting disc that contacts the body portion transitions in the following order: radially outward of the bottomed cylindrical member, forward in the feed direction of the disc saw, radially inward of the bottomed cylindrical member, and rearward in the feed direction of the disc saw. In the process of cutting the torso, the disc saw driven by the process of rotating the cutting disc is moved forward in the feed direction to cut the torso, while scattering the cutting chips from the torso radially inward. A method for cutting a bottomed cylindrical member.
2. Prior to the step of rotating the cutting disc, the step of positioning the disc saw radially inward of the bottomed cylindrical member is further included. A method for cutting a bottomed cylindrical member as described in claim 1.
3. A method for cutting a bottomed cylindrical member provided inside a reactor containment vessel, having a body portion extending in the vertical direction and a lower closing portion that closes the lower end of the body portion, A step of driving the disc saw and rotating the cutting disc of the disc saw, The process of cutting the body by feeding the disc saw along the surface of the body while the cutting disc has penetrated the body, Prior to the step of rotating the cutting disc, the disc saw is positioned radially outward of the bottomed cylindrical member, Includes, In the step of rotating the cutting disc, in the step of cutting the body portion, the outer circumference of the cutting disc that contacts the body portion drives the disc saw in a rotational direction that transitions in the following order: radially outward of the bottomed cylindrical member, forward in the feed direction of the disc saw, radially inward of the bottomed cylindrical member, and backward in the feed direction of the disc saw. A method for cutting a bottomed cylindrical member.
4. The process of cutting the torso involves feeding the disc saw in the circumferential direction of the torso and cutting the torso into multiple pieces in the vertical direction. A method for cutting a bottomed cylindrical member according to claim 1 or 2.
5. The process of cutting the torso involves feeding the disc saw in the vertical direction and cutting the torso into multiple pieces in the circumferential direction. A method for cutting a bottomed cylindrical member according to claim 1 or 2.
6. A method for cutting a bottomed cylindrical member provided inside a reactor containment vessel, having a body portion extending in the vertical direction and a lower closing portion that closes the lower end of the body portion, A step of driving the disc saw and rotating the cutting disc of the disc saw, The process of cutting the body by feeding the disc saw along the surface of the body while the cutting disc has penetrated the body, Includes, In the step of rotating the cutting disc, in the step of cutting the body portion, the disc saw is driven in a rotational direction in which the outer circumference of the cutting disc that contacts the body portion transitions in the following order: radially outward of the bottomed cylindrical member, forward in the feed direction of the disc saw, radially inward of the bottomed cylindrical member, and rearward in the feed direction of the disc saw. The bottomed cylindrical member is a reactor vessel, Water is stored in the aforementioned reactor vessel, The water inside the reactor vessel is drained, and at a position above the water level inside the reactor vessel, the torso is cut with the disc saw. A method for cutting a bottomed cylindrical member.