JP5989688B2 - Dismantling method for reactor pressure vessel - Google Patents

Description

  The present invention is a method for dismantling a reactor pressure vessel, and in particular, can dismantle a reactor pressure vessel easily and reliably without installing an elevating means for raising the reactor pressure vessel in a shielding wall. The present invention relates to a method for dismantling a reactor pressure vessel.

  Patent Document 1 discloses an example of a method of dismantling a pressure vessel that dismantles and removes a reactor pressure vessel (hereinafter sometimes simply referred to as a pressure vessel) with the decommissioning of the reactor. Hereinafter, this disassembly method is referred to as a conventional disassembly method 1 and will be described with reference to the drawings.

  11A is a cross-sectional view showing a state in which the pressure vessel is supported by the elevating means, and FIG. 11B is a cross-sectional view showing a state in which the pressure vessel is raised by the elevating means and the upper portion of the pressure vessel is cut. FIG. 12 is an enlarged view of a portion surrounded by a two-dot chain line in FIG.

  In the conventional dismantling method 1, first, as shown in FIG. 11A, a pressure vessel 41 filled with a shielding material such as mortar is supported by an elevating means 43 installed in a shielding wall. Next, as shown in FIG. 11 (B), the pressure vessel 41 is raised by a predetermined height by the lifting means 43. Next, the upper part of the pressure vessel 41 is horizontally cut by the wire saw 44, and the cut piece is accommodated in the shielding vessel 45 and carried out.

  As shown in FIG. 12, the elevating means 43 includes a temporary base 46 and a plurality of hydraulic cylinders 47 placed on the temporary base 46, and the pressure vessel 41 is placed on the hydraulic cylinder 47 via a support base 48. Placed. The pressure vessel 41 is sequentially raised by changing the plurality of hydraulic cylinders 47 by sequentially extending the temporary base 46 upward.

  Patent Document 2 discloses another method for dismantling a pressure vessel. Hereinafter, this disassembly method is referred to as a conventional disassembly method 2.

  In the conventional dismantling method 2, although not shown, the pressure vessel is cut into small pieces by a cutting torch provided in the pressure vessel, and the dismantled product is held by a holding arm provided in the pressure vessel and carried out. .

Japanese Patent Laid-Open No. 2005-3434 JP-A-10-90493 Japanese Patent No. 2828430

  According to the conventional disassembly methods 1 and 2, the pressure vessel can be disassembled, but there are the following problems.

  In the conventional dismantling method 1, the pressure vessel 41 is cut by the wire saw 44, so that the cutting equipment becomes large. Moreover, since the heavy pressure vessel 41 needs to be raised by the hydraulic cylinder 47, the large hydraulic cylinder 47 is required. Accordingly, since it is necessary to make a large opening in the shielding wall 42 for carrying the large hydraulic cylinder 47 into the shielding wall 42, the strength of the shielding wall 42 is lowered, and there is a risk of hindering the subsequent dismantling work. There is. Furthermore, since it is necessary to change the hydraulic cylinder 47 by sequentially extending the temporary base 46 upward, it takes a lot of time and labor to install and operate the lifting means 43.

  In the conventional disassembly method 2, the pressure vessel is cut with a cutting torch, so that the cutting equipment is not large. However, since the pressure vessel is cut into small pieces, it takes time and labor to disassemble.

  Accordingly, an object of the present invention is to minimize the size of the opening in the shielding wall by using a mount with an electromagnet that can be attracted to the bottom of the pressure vessel in place of the lifting means of the conventional dismantling method 1. In addition, by using a plurality of electromagnet mounts, the height of the pressure vessel can be easily adjusted, and therefore a method for dismantling the pressure vessel for reactors can be provided. There is to do.

  Another object of the present invention is to attach a cutting torch for cutting the pressure vessel horizontally to the hollow rotating shaft of the cutting mechanism, and through a wheel rolling on a base fixed to the fixed shaft of the cutting mechanism, To provide a method for disassembling a pressure vessel for a nuclear reactor capable of accurately cutting a pressure vessel horizontally by rotating it horizontally while maintaining a constant distance between the tip of the cutting torch and the inner surface of the pressure vessel. It is in.

  Another object of the present invention is to attach an arm that can be raised and lowered radially around a hollow rotary shaft, and tilt the arm so that the tip of the arm contacts the inner surface of the pressure vessel. It is an object of the present invention to provide a method of dismantling a pressure vessel for a nuclear reactor that can accurately cut the pressure vessel horizontally by positioning in the position.

  The present invention has been made to achieve the above object, and is characterized by the following.

The invention according to claim 1 is a method of disassembling a reactor pressure vessel surrounded by a shielding wall.
(A) An opening is made in the lower part of the shielding wall, the pressure vessel is suspended by a strand jack, and the head of the pressure vessel is removed.
(B) A platform with an electromagnet is placed on the bottom of the shielding wall from the opening and carried on a carriage with an elevator.
(C) The elevator is extended to lift the gantry to the bottom of the pressure vessel, and an electromagnet is operated to be attached to the bottom of the pressure vessel.
(D) The elevator is shrunk and the next frame with an electromagnet is placed on the carriage and carried into the bottom of the shielding wall.
(E) The elevator is extended to lift the next frame to the existing frame, and an electromagnet is actuated to be attached to the existing frame.
(F) The steps (d) and (e) are repeated to install a plurality of mounts at the bottom of the pressure vessel.
(G) The pressure vessel is lifted by the strand jack together with a plurality of the gantry, and a new gantry is installed by the cart in the gap between the bottom of the shielding wall and the lowermost gantry installed in the pressure vessel. Bring it in and place it on the bottom gantry.
(H) The elevator is shrunk and the cart is removed.
(I) The pressure vessel is suspended from the bottom of the shielding wall by the strand jack together with the plurality of mounts.
(J) The upper part of the pressure vessel protruding from the shielding wall is horizontally cut by a cutting mechanism installed in the pressure vessel.
(K) The cut piece is lifted by the strand jack and removed.
(L) The strand jack is replaced and the pressure vessel is lifted, and a new frame is carried by the carriage into the gap between the bottom of the shielding wall and the lowermost frame installed on the pressure vessel.
(M) Extending the elevator and attaching the new frame to the lower frame.
(N) The steps (g) to (m) are repeated to disassemble and remove the pressure vessel.
It has the characteristic in having.

  According to a second aspect of the present invention, in the first aspect of the present invention, the cutting mechanism includes a fixed shaft disposed in a central portion of the pressure vessel and a hollow provided rotatably on the outer side of the fixed shaft. A rotating shaft, a base fixed to the fixed shaft, an extendable cutting torch attached to the hollow rotating shaft on the base at a right angle to the hollow rotating shaft, and attached to the hollow rotating shaft Positioning means, and the cutting torch rotates horizontally while maintaining a constant distance between the tip of the cutting torch and the inner surface of the pressure vessel via a wheel rolling on the base, The positioning means includes a retractable arm that is radially attached to the hollow rotating shaft about the hollow rotating shaft, and the arm is tilted so that the tip of the arm contacts the inner surface of the pressure vessel. By the cutting toe The one having a characteristic to be positioned at a predetermined position.

  According to this invention, instead of the lifting means of the conventional dismantling method 1, the size of the opening in the shielding wall can be kept to the minimum necessary by using a mount with an electromagnet that can be attracted to the bottom of the pressure vessel. Therefore, there is no possibility that the strength of the shielding wall is reduced. Moreover, since the height of the pressure vessel can be easily adjusted by using a plurality of mounts with electromagnets, the pressure vessel can be easily disassembled.

  According to the present invention, the cutting torch is attached horizontally to the hollow rotating shaft of the cutting mechanism, and the tip of the cutting torch and the pressure vessel are moved via the wheels that roll on the base fixed to the fixed shaft of the cutting mechanism. The pressure vessel can be accurately cut by horizontally rotating while maintaining a constant distance from the inner surface of the pressure vessel.

  Further, according to the present invention, the arm that can be raised and lowered radially about the hollow rotary shaft is attached, the arm is tilted, the tip of the arm is brought into contact with the inner surface of the pressure vessel, and the cutting torch is brought into a predetermined position. By positioning, the pressure vessel can be cut accurately.

It is a schematic sectional drawing which shows the dismantling method of the pressure vessel for reactors of this invention. It is a schematic perspective view which shows a driving | running | working lifter. It is a schematic front view which shows a driving | running | working lifter. It is a schematic front view which shows the traveling lifter which lifted the heavy article with the 2nd strand jack. It is a schematic front view which shows the traveling lifter which deposited the weight of the heavy article on the fixed beam and lifted the inner column with the first strand jack. It is a front view which shows the mount frame with the electromagnet adsorb | sucked mutually. It is sectional drawing which shows the process of carrying in the trolley | bogie with an elevator which put the mount with an electromagnet in the shielding wall. It is sectional drawing which shows the process which lifts the 1st mount frame to the bottom part of a pressure vessel with an elevator, operates an electromagnet, and makes it adsorb | suck to the bottom part of a pressure vessel. It is sectional drawing which repeats (A) and (B) process, and shows the process of installing several mounts in the bottom part of a pressure vessel. It is sectional drawing which shows the process of installing the lowermost mount frame in the bottom part of a pressure vessel. It is sectional drawing which shows the process of lifting the pressure vessel which installed the several mount with the 2nd strand jack. It is sectional drawing which shows the process of installing a new mounting frame in the clearance gap between the bottom part of a shielding wall, and the lowermost mounting frame installed in the pressure vessel. It is sectional drawing which shows the process of shrinking an elevator and removing a trolley | bogie. It is sectional drawing which shows the process of hanging a pressure vessel on the bottom part of a shielding wall with a 2nd strand jack with several mounts. It is sectional drawing which shows the process of cut | disconnecting horizontally the upper part of the pressure vessel which protruded from the shielding wall with a cutting mechanism. It is sectional drawing which shows the process of carrying in a cutting | disconnection mechanism in a pressure vessel. It is sectional drawing which shows the process of tilting an arm and positioning a cutting torch in a predetermined position. It is sectional drawing which shows the process of extending a cutting torch. It is sectional drawing which shows the process of turning a cutting torch horizontally and cutting a pressure vessel. It is a partial notch enlarged view of a cutting mechanism. It is an expanded sectional view which shows the front-end | tip part of a cutting torch. It is sectional drawing which shows the state which supported the pressure vessel with the raising / lowering means by the conventional dismantling method 1. FIG. It is sectional drawing which shows the state which raised the pressure vessel by the raising / lowering means by the conventional dismantling method 1, and cut | disconnected the upper part of the pressure vessel. FIG. 12 is an enlarged view of a portion surrounded by a two-dot chain line in FIG.

  An embodiment of a method for dismantling a reactor pressure vessel according to the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic cross-sectional view showing a method for dismantling a reactor pressure vessel according to the present invention.

  In FIG. 1, 1 is a reactor vessel, 2 is a shield wall installed in the reactor vessel 1, with an opening 3 in the bottom, and 4 is a reactor pressure installed in the shield wall 2. The container 5 lifts and lowers the pressure vessel 4 and also transports a cut piece 6 of the pressure vessel 4 [see FIG. 7 (I)], and the lift 5 is attached to the elevator 8 [see FIG. 7 (B)]. A carriage 9 is mounted on the carriage 7, and a mount with an electromagnet 10 attached thereto, and 11 is a cutting mechanism installed in the pressure vessel 4.

  First, the traveling lifter 5 will be described with reference to the drawings.

  FIG. 2 is a schematic perspective view showing the travel lifter, and FIG. 3 is a schematic front view showing the travel lifter.

  As shown in FIG. 2 and FIG. 3, the traveling lifter 5 includes a pair of lifting and lowering mechanisms 13A consisting of two lifting mechanisms 13 and a pair of lifting and lowering means 14A that are arranged in parallel with one lifting and lowering means 14A. And the other lifting / lowering means 14B composed of two lifting / lowering mechanisms 13. One lifting / lowering means 14A and the other lifting / lowering means 14B can be moved integrally along the rail 16 by the wheels 15 (see FIG. 3).

  The elevating mechanism 13 is assembled so that it can be moved up and down by a first strand jack 19 </ b> A (see FIG. 3) in which the inner column 18 is nested with the outer column 17 and the strand 21 b is nested.

  A jack receiving beam 20 to which a second strand jack 19B is attached is stretched between the upper portions of the inner struts 18 of the one lifting means 14A and the other lifting means 14B. The second strand jack 19B has basically the same structure as the first strand jack 19A, and lifts and lowers the heavy load (W) suspended by the strand 21a, in this example, the reactor pressure vessel 4 intermittently. . The first and second strand jacks 19A and 19B are disclosed in Patent Document 3, for example.

  A fixed beam 23 to which a fixed anchor 22 is attached is stretched between upper portions of the outer struts 17 of the one lifting means 14A and the other lifting means 14B. The fixed anchor 22 has a structure in which the strand 21a inserted therethrough can be pulled up without resistance but cannot be pulled down by the wedge structure.

  Next, a method for moving a heavy object (W) by the traveling lifter 5 will be described with reference to the drawings.

  First, as shown in FIGS. 2 and 3, the lower end of the strand 21a of the second strand jack 19B is set to a heavy object (W) in the state where the inner struts 18 of the elevating means 13 are lowered, and the fixed anchor of the fixed beam 23 is fixed. It fixes through 22.

  Next, as shown in FIG. 4, the heavy object (W) is lifted by the second strand jack 19B. At this time, since the lower end of each inner column 18 is in contact with the base 24, the heavy object (W) can be stably lifted.

  Thereafter, lifting of the heavy load (W) by the second strand jack 19B is released. As a result, the weight of the heavy object (W) is deposited on the fixed beam 23 via the fixed anchor 22. That is, since the fixed beam 23 is fixed between the upper ends of the outer support columns 17, the weight of the heavy object (W) is entrusted to the outer support columns 17.

  When the weight of the heavy object (W) is deposited in the outer column 17 in this manner, as shown in FIG. 5, each inner column 18 that is not loaded is raised by the first strand jack 19A, and each inner column 18 is moved. Is slightly lifted from the base 24.

  And in this state, one raising / lowering means 14A and the other raising / lowering means 14B are integrally moved with a heavy article (W).

  In this way, according to the traveling lifter 5, the heavy object (W), that is, the moving piece 6 of the reactor pressure vessel 4 is not moved in the lifted state, but is moved after being lifted. Since it can be moved in the state deposited in the lifter 5, the cut piece 6 can be moved stably.

  Next, the cart 7 will be described.

  An elevator 8 [see FIG. 7 (B)] is attached on the carriage 7 so that the gantry 9 placed on the elevator 8 can be raised and lowered. The carriage 7 can enter and exit the reactor vessel 1 through the opening 3 of the reactor vessel 1 in a state where the elevator 8 is contracted.

  Next, the gantry 9 will be described with reference to the drawings.

  FIG. 6 is a front view showing the gantry 9 with the electromagnets adsorbed to each other.

  As shown in FIG. 6, the gantry 9 is attached with an electromagnet 10 and can be attracted to the bottom of the pressure vessel 4, and the gantry 9 can also be attracted to each other. Further, when the load of the pressure vessel 4 is applied to the gantry 9, the electromagnet 10 is not directly loaded, and the load is applied only to the main body of the gantry 9.

  Further, since the gantry 9 is small, the size of the opening 3 in the shielding wall 2 can be minimized. As a result, there is no possibility that the strength of the shielding wall 2 is reduced. Moreover, since the height of the pressure vessel 4 can be easily adjusted by using a plurality of mounts 9 with electromagnets, the pressure vessel 4 can be easily disassembled.

  Next, the cutting mechanism 11 will be described with reference to the drawings.

  FIG. 8A is a cross-sectional view showing a step of carrying the cutting mechanism into the pressure vessel, and FIG. 9 is an enlarged partial cutaway view of the cutting mechanism.

  As shown in FIGS. 8A and 9, the cutting mechanism 11 includes a fixed shaft 25 disposed at the center of the pressure vessel 4, and a hollow rotary shaft 26 that is rotatably provided outside the fixed shaft 25. A disc-shaped base 27 fixed to the fixed shaft 25, an extendable cutting torch 28 attached to the hollow rotary shaft 26 on the base 27 at a right angle to the hollow rotary shaft 26, and the hollow rotary shaft 26. And an arm 29 as positioning means.

  The cutting torch 28 rotates horizontally while maintaining a constant distance between the tip of the cutting torch 28 and the inner surface of the pressure vessel 4 via a wheel 30 that rolls on the base 27. A mechanism for maintaining a constant distance between the tip of the cutting torch 28 and the inner surface of the pressure vessel 4 will be described with reference to the drawings.

  FIG. 10 is an enlarged cross-sectional view showing the tip portion of the cutting torch 28.

  As shown in FIG. 10, the distal end portion 28 a of the cutting torch 28 is attached to a leg member 33 having a roller 32 that rolls on the inner surface of the pressure vessel 4, and the distal end portion 28 a together with the leg member 33 is connected to the torch body 28 b. On the other hand, it can be expanded and contracted via a spring 31.

  As a result, even if the position of the hollow rotary shaft 26 to which the cutting torch 28 is attached is slightly displaced in the horizontal direction, the roller 32 rolls along the inner surface of the pressure vessel 4. The distance between the inner surface of the pressure vessel 4 is always kept constant. As a result, the pressure vessel 4 can be accurately cut horizontally.

  The arm 29 is attached to the hollow rotary shaft 26 so as to be able to rise and fall radially about the hollow rotary shaft 26, and the arm 29 is tilted to bring the tip of the arm 29 into contact with the inner surface of the pressure vessel 4. It has a function of positioning 28 at a predetermined position.

  A method for dismantling the reactor pressure vessel according to the present invention will be described.

  First, as shown in FIG. 1, the opening 3 is opened at the lower part of the shielding wall 2, the pressure vessel 4 is suspended by the strand 21a of the second strand jack 19B of the traveling lifter 5, and the head 4a of the pressure vessel 4 is removed. .

  Next, as shown in FIG. 7 (A), a base 9 with an electromagnet is placed on the bottom 7 of the shielding wall 2 from the opening 3 and carried on a carriage 7 with an elevator.

  Next, as shown in FIG. 7B, the elevator 8 of the carriage 7 is extended to lift the gantry 9 to the bottom of the pressure vessel 4, and the electromagnet 10 is operated to be attracted to the bottom of the pressure vessel 4.

  Next, as shown in FIG. 7C, the elevator 8 is shrunk and the next base 9 with an electromagnet is placed on the carriage 7 and carried into the bottom of the shielding wall 2. The next base 9 is extended by extending the elevator 8. It lifts up to the existing base 9, operates the electromagnet 10, and makes it adsorb | suck to the existing base 9, and installs.

  The above steps are repeated to install a plurality of mounts 9 at the bottom of the pressure vessel 4 as shown in FIG.

  Next, as shown in FIG. 7E, the pressure vessel 4 is lifted together with the plurality of mounts 9 by the strands 21 a of the second strand jack 19 </ b> B of the traveling lifter 5.

  Next, as shown in FIG. 7 (F), a new base 9 is carried by the carriage 7 into the gap between the bottom of the shielding wall 2 and the bottom base 9 installed in the pressure vessel 4. It is adsorbed on the base 9 and installed.

  Next, as shown in FIG. 7 (G), the elevator 8 is contracted and the carriage 7 is removed.

  Next, as shown in FIG. 7H, the pressure vessel 4 is suspended from the bottom of the shielding wall 2 by the strands 21 a of the second strand jack 19 </ b> B of the traveling lifter 5 together with the plurality of mounts 9.

  Next, as shown in FIG. 7 (I), the upper part of the pressure vessel 4 protruding from the shielding wall 2 is horizontally cut by a cutting mechanism installed in the pressure vessel 4, and the cut piece 6 is secondly connected to the second lifter 5. It is lifted and removed by the strand 21a of the strand jack 19B. A method for cutting the pressure vessel 4 will be described later.

  Next, the second strand jack 19B is replaced, the pressure vessel 4 is lifted, and a new gantry 9 is installed by the carriage 7 in the gap between the bottom of the shielding wall 2 and the lowermost gantry 9 installed in the pressure vessel 4. Carry in.

  Next, the elevator 8 is extended and a new base 9 is attached to the bottom base 9 and installed.

  And the said process is performed repeatedly and the pressure vessel 4 is disassembled and removed.

  Next, a method for cutting the pressure vessel 4 will be described.

  First, as shown in FIG. 8A, the cutting mechanism 11 is lowered to a predetermined position in the pressure vessel 4 with the arm 29 raised.

  Next, as shown in FIG. 8B, the arm 29 is tilted to bring the tip of the arm 29 into contact with the inner surface of the pressure vessel 4. Thereby, the cutting torch 28 is positioned at a predetermined position of the pressure vessel 4.

  Next, as shown in FIG. 8C, the cutting torch 28 is extended until the roller 32 comes into contact with the inner surface of the pressure vessel 4.

  Then, as shown in FIG. 8D, the pressure vessel 4 is cut by turning the cutting torch 28 horizontally while supplying gas to the cutting torch 28. At this time, the distance between the tip of the cutting torch 28 and the inner surface of the pressure vessel 4 is always kept constant. Moreover, since the cutting torch 28 rolls on the base 27 via the wheels 30, it stably turns horizontally.

  The cut piece 6 of the pressure vessel 4 cut in this way is lifted by the traveling lifter 5 and removed.

  As described above, according to the present invention, the opening 3 in the shielding wall 2 can be obtained by using the gantry 9 with an electromagnet that can be attracted to the bottom of the pressure vessel 4 in place of the lifting means of the conventional dismantling method 1. Therefore, there is no possibility that the strength of the shielding wall 2 is reduced. Moreover, since the height of the pressure vessel 4 can be easily adjusted by using a plurality of mounts 9 with electromagnets, the pressure vessel 4 can be easily disassembled.

  Further, according to the present invention, the cutting torch 28 is horizontally attached to the hollow rotary shaft 26 of the cutting mechanism 11, and the wheels 30 are rolled on the base 27 fixed to the fixed shaft 25 of the cutting mechanism 11. By rotating horizontally while maintaining a constant distance between the tip of the cutting torch 28 and the inner surface of the pressure vessel 4, the pressure vessel 4 can be accurately cut.

  Further, according to the present invention, the arm 29 that can be raised and lowered radially about the hollow rotary shaft 26 is attached to the hollow rotary shaft 26, and the tip of the arm 29 is brought into contact with the inner surface of the pressure vessel 4 by tilting the arm 29. Since the cutting torch 28 can be positioned at a predetermined position, the pressure vessel 4 can be accurately cut horizontally.

1: Reactor vessel 2: Shielding wall 4: Reactor pressure vessel 4a: Head 5: Travel lifter 6: Cutting piece 7: Carriage 8: Elevator 9: Mount 10: Electromagnet 11: Cutting mechanism 13: Elevating mechanism 14A: One Lifting means 14B: The other lifting means 15: Wheel 16: Rail 17: Outer strut 18: Inner strut 19A: First strand jack 19B: Second strand jack 20: Jack receiving beam 21a: Strand 21b: Strand 22: Fixed anchor 23 : Fixed beam 24: Base 25: Fixed shaft 26: Hollow rotating shaft 27: Base 28: Cutting torch 28a: Tip portion 28b: Torch body 29: Arm 30: Wheel 31: Spring 32: Roller 33: Leg member 41: Pressure Container 42: Shielding wall 43: Lifting means 44: Wire saw 45: Shielding container 46: Temporary stand 47: Hydraulic system Linder 48: Support stand

Claims (2)

In a method for dismantling a reactor pressure vessel surrounded by a shielding wall,
(A) An opening is made in the lower part of the shielding wall, the pressure vessel is suspended by a strand jack, and the head of the pressure vessel is removed.
(B) A platform with an electromagnet is placed on the bottom of the shielding wall from the opening and carried on a carriage with an elevator.
(C) The elevator is extended to lift the gantry to the bottom of the pressure vessel, and an electromagnet is operated to be attached to the bottom of the pressure vessel.
(D) The elevator is shrunk and the next frame with an electromagnet is placed on the carriage and carried into the bottom of the shielding wall.
(E) The elevator is extended to lift the next frame to the existing frame, and an electromagnet is actuated to be attached to the existing frame.
(F) The steps (d) and (e) are repeated to install a plurality of mounts at the bottom of the pressure vessel.
(G) The pressure vessel is lifted by the strand jack together with a plurality of the gantry, and a new gantry is installed by the cart in the gap between the bottom of the shielding wall and the lowermost gantry installed in the pressure vessel. Bring it in and place it on the bottom gantry.
(H) The elevator is shrunk and the cart is removed.
(I) The pressure vessel is suspended from the bottom of the shielding wall by the strand jack together with the plurality of mounts.
(J) The upper part of the pressure vessel protruding from the shielding wall is horizontally cut by a cutting mechanism installed in the pressure vessel.
(K) The cut piece is lifted by the strand jack and removed.
(L) The strand jack is replaced and the pressure vessel is lifted, and a new frame is carried by the carriage into the gap between the bottom of the shielding wall and the lowermost frame installed on the pressure vessel.
(M) Extending the elevator and attaching the new frame to the lower frame.
(N) The steps (g) to (m) are repeated to disassemble and remove the pressure vessel.
A method for dismantling a pressure vessel for a nuclear reactor, comprising:   The cutting mechanism includes a fixed shaft disposed at a central portion of the pressure vessel, a hollow rotary shaft rotatably provided outside the fixed shaft, a base fixed to the fixed shaft, and the base An extendable cutting torch attached to the hollow rotary shaft at right angles to the hollow rotary shaft, and positioning means attached to the hollow rotary shaft, the cutting torch rolling on the base And rotating horizontally while maintaining a constant distance between the tip of the cutting torch and the inner surface of the pressure vessel via a rotating wheel, and the positioning means is radially centered on the hollow rotating shaft. 2. The cutting torch is positioned at a predetermined position by tilting an attached tiltable arm and bringing a tip of the arm into contact with an inner surface of the pressure vessel. 3. , Reactor pressure Method of disassembling the container.

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