JP4234631B2 - Method for decontamination and disassembly of cylindrical structure - Google Patents

Description

  The present invention relates to a method for decontamination and disassembly of cylindrical structures such as heat exchangers and pipes whose inner peripheral surface is radioactively contaminated. is there.

  Along with the decommissioning of an aging nuclear plant, a method for disposing of equipment in the plant is being studied. As a disposal method, a method of dismantling the equipment and discarding all the dismantled materials is conceivable. However, this method generates a large amount of waste, and enormous costs are required for disposal, and the dismantled material cannot be reused. In view of this, a method for decontamination (or decontamination after disassembly) after decontaminating (removing attached radioactive substances) the surface of the device that has been radioactively contaminated has been studied. According to this method, the amount of waste can be reduced and the dismantled material can be reused.

  Conventionally, as a decontamination method, a chemical decontamination method for decontamination using a decontamination solution, a blasting method for decontamination by blowing an abrasive and scraping the surface, and the like have been proposed. As a chemical decontamination method, for example, there was a method described in Patent Document 1 below. As a blasting method, for example, there is a method described in Patent Document 2 below.

Japanese Patent Laid-Open No. 11-109094 JP 2000-75095 A

  Conventional decontamination and disassembly required separate equipment. The present invention has been made in view of the above-described points, and an object of the present invention is to provide a decontamination and disassembly method that performs decontamination and disassembly using a common apparatus.

  In the method for decontamination and dismantling of the cylindrical structure according to the present invention, the outer peripheral surface (14a) is such that the inner peripheral surface (14b) surrounds the outer peripheral surface (14a) of the cylindrical structure (14) that is radioactively contaminated. A fixed portion (46) to be mounted on the rotating portion, and a rotating portion that is rotatably supported by the fixed portion (46) and rotates around the outer peripheral surface (14a) of the cylindrical structure (14) by power (58). (48), a cutting tool (66, 74) mounted on the rotating part (48), and a cutting tool (72, 84) mounted on the tool rest (66, 74). (44) is used, the cutting blade (84) is inserted from the open end (14c) of the cylindrical structure (14), and the cutting blade (84) is inserted into the inner peripheral surface of the cylindrical structure (14). (14b), the rotating part (48) is rotated and the cutting blade (84) The inner peripheral surface (14b) of the cylindrical structure (14) is cut by the cutting blade (84) by feeding it in the axial direction of the cylindrical structure (14) to remove the inner peripheral surface (14b). Dyeing is performed, the cutting blade (72) is opposed to the outer peripheral surface (14a) of the cylindrical structure (14), the rotating portion (48) is rotated, and the cutting blade (72) is moved to the cylindrical structure. The cylindrical structure (14) is disassembled by cutting the cylindrical structure (14) from the outside with the cutting blade (72) by cutting it inward in the radial direction of (14). .

In the present invention, when the inner peripheral surface (14b) is decontaminated, a cutting tool (84) is inserted from the opening end (14c) of the cylindrical structure (14) as the tool post. Inner circumference that allows the cutting blade (84) to face the inner peripheral surface (14b) of the cylindrical structure (14) and feed the cutting blade (84) in the axial direction of the cylindrical structure (14) When the surface cutting tool post (74) is used and the disassembly is performed, the cutting tool (72) faces the outer peripheral surface (14a) of the cylindrical structure (14) as the tool post and the cutting is performed. it is to use blade (72) of the cylindrical structure (14) outer peripheral surface cutting tool rest that can be sent in a radial direction in the direction of the (66).

The present invention further performs the decontamination of the inner peripheral surface (14b) of the cylindrical structure (14) over a predetermined width in the axial depth direction from the open end (14c) of the cylindrical structure (14). After the decontamination, the mounting position of the fixing portion (46) of the cutting machine (44) with respect to the outer peripheral surface (14a) of the cylindrical structure (14) is decontaminated on the inner peripheral surface (14b). Moving to the back side in the axial direction from the planned cutting position (C3, C4,..., Cn) set at the position where the cutting is performed, and performing the cutting at the planned cutting position (C3, C4,..., Cn), After cutting, the mounting position of the fixed part (46) of the cutting machine (44) remains unchanged, and the cylindrical structure (14) is renewed with respect to the inner peripheral surface (14b) of the cylindrical structure (14). open end from (14c ') over the axial inner direction of the predetermined width is performed the decontamination.

  The cycle of the decontamination process, the fixing part moving process, and the cutting process can be repeated as appropriate.

  A method for decontamination and disassembly of a cylindrical structure according to the present invention is a method for decontaminating and disassembling a heat exchanger (10) in which the inside of a cylindrical main body (14) is radioactively contaminated, wherein the main body A fixing portion (46) mounted on the outer peripheral surface (14a) so as to surround the outer peripheral surface (14a) of (14), and the main body by the power (58) supported rotatably on the fixing portion (46). A rotating part (46) rotating around the outer peripheral surface (14a) of the body (14), a tool post (66, 74) mounted on the rotating part (46), and the tool post (66, 74) A cutting machine (44) having a mounted cutting blade (72, 84) is used, and the fixing part (46) of the cutting machine (44) is connected to the tube plate (16) of the main body barrel (14). ) On the back side of the heat transfer tube bundle (26), and the tool post as the tool post. A tool post for outer peripheral surface cutting that allows the cutting blade (72) to face the outer peripheral surface (14a) of the main body barrel (14) and feed the cutting blade (72) in the radially inward direction of the main body barrel (14). (66) and a cutting blade (72) on the outer peripheral surface (14a) of the main body barrel (14) at a position between the mounting position of the fixing portion (46) and the position of the tube plate (16). , The rotating portion (48) is rotated, and the cutting blade (72) is fed inwardly in the radial direction of the main body barrel (14), whereby the main body barrel (14) is moved by the cutting blade (72). After cutting from the outside, the heat transfer tube bundle (26) is extracted from the main body barrel (14) together with the tube plate (16), and after the extraction, the mounting position of the fixing portion (46) is As it is, the opening end formed by cutting the main body barrel (14) as the tool post 14c), the cutting blade (84) is inserted so that the cutting blade (84) faces the inner peripheral surface (14b) of the main body barrel (14) and the cutting blade (84) is placed on the shaft of the main body barrel (14). The cutting tool (84) is inserted by inserting the cutting tool (84) from the opening end (14c) of the main body barrel (14) using the inner peripheral surface cutting tool post (74) capable of feeding in the direction. By facing the inner peripheral surface (14b) of the main body cylinder (14), rotating the rotating portion (48) and sending the cutting blade (84) in the axial direction of the main body cylinder (14), the cutting The inner peripheral surface (14b) of the main body barrel (14) is cut with a cutter (84) to decontaminate the inner peripheral surface (14b) from the opening end (14c) over a predetermined width in the axial direction. After the decontamination, the cutting machine (44) is fixed to the outer peripheral surface of the main body barrel (14). The mounting position of the part (46) is moved further in the axial direction than the next scheduled cutting position (C3, C4,..., Cn) set at the position where the inner peripheral surface (14b) has been decontaminated. The cutting tool (72) is made to face the outer peripheral surface (14a) of the body barrel (14) at the planned cutting position (C3, C4,..., Cn) using the outer peripheral surface cutting tool post (66). The rotating body (48) is rotated and the cutting blade (72) is fed inward in the radial direction of the main body barrel (14) to cut the main body barrel (14) from the outside with the cutting blade (72). After the cutting, the mounting position of the fixing portion (46) is left as it is, the inner peripheral surface cutting tool post (74) is used, and a new open end ( 14c ′), the cutting blade (84) is inserted, and the cutting blade (84) is placed on the inner peripheral surface of the main body barrel (14). The cutting blade (84) is rotated in the axial direction of the main body cylinder (14) by rotating the rotating portion (48) and facing the inner periphery of the main body cylinder (14). The surface (14b) is cut to decontaminate the inner peripheral surface (14b) from the new open end (14c ′) over a predetermined width in the axial direction, and the movement of the fixed portion (46) is performed thereafter. The cycle of the process, the cutting process, and the decontamination process is repeated as appropriate.

  The extracted heat transfer tube bundle (26) is cut and separated into individual heat transfer tubes, and the outer peripheral surface and the inner peripheral surface can be decontaminated for each heat transfer tube.

According to the present invention, it is possible to perform decontamination and disassembly by sharing a cutting machine.

  Embodiments of the present invention will be described below. Here, the case where decontamination and dismantling of the feed water heater of a nuclear power plant is demonstrated. First, the structure of the feed water heater will be described with reference to FIG. The feed water heater 10 is used by being placed horizontally on the floor 12. A water chamber body 18 is connected to one end of the cylindrical body body 14 with a tube plate 16 in between. The internal space of the water chamber body 18 is partitioned into upper and lower spaces 18 a and 18 b by a partition plate 20. The lower space 18 b communicates with a water supply inlet 22 formed on the lower surface of the water chamber body 18. The upper space 18 a communicates with a water supply outlet 24 formed on the upper surface of the water chamber body 18. A heat transfer tube bundle 26 is accommodated in the main body barrel 14 by being bent in a U-shape. The inlet side end of the heat transfer tube bundle 26 penetrates through the tube plate 16 and communicates with the water chamber trunk lower space 18b. The outlet side end of the heat transfer tube bundle 26 penetrates the tube plate 16 and communicates with the water chamber trunk upper space 18a. A steam inlet 28 is formed on the upper surface of the main body cylinder 14. A drain outlet 30 is formed on the lower surface of the main body barrel 14. In addition to this, a body escape valve seat 32, a body air vent seat 34, and the like are formed in the main body body 14. The other end of the main body barrel 14 is closed with a body end plate 36. A fixed leg 38 and wheeled legs 40 and 42 are attached to the lower surface of the main body body 14.

  An example of a cutting machine used for decontamination and disassembly of the main body cylinder 14 is shown in FIG. (A) is a front view, (b) is a right side view. This cutting machine 44 uses “Cutland” (trademark) manufactured by Todate Engineering Co., Ltd. “Cutland” is an apparatus using the technique described in Japanese Patent Application Laid-Open No. 2003-117720 (name of invention “cutting / groove processing apparatus”). That is, the cutting machine 44 includes a ring-shaped fixing portion 46 and a rotating portion 48 having an inner diameter larger than the outer diameter of the main body cylinder 14. The fixing portion 46 has an upper and lower divided structure (half structure) divided by a horizontal dividing line 50, and both divided portions 46a and 46b are hooks 52 arranged on the left and right outer peripheral surfaces (only the right hook is shown in FIG. 3). (B), they can be hooked together and bolted together to be connected to each other.

  Similarly, the rotating part 48 has a two-divided structure (half structure) and can be connected to each other by a connecting tool (not shown). When dividing the fixed part 46 and the rotating part 48, the rotating part 48 is aligned with the initial position (position in FIG. 3), and the rotating part upper divided part 48a is connected to the fixed part upper divided part 46a for rotation. In a state where the subordinate-side divided portion 48b is connected to the fixed portion lower-side divided portion 46b, it is divided into two vertically by a dividing line 50. In other words, the fixed portion 46 and the rotating portion 48 are divided into half in a state where the upper divided portions 46a and 48a are integrated and the lower divided portions 46b and 48b are integrated. The connection can be performed in the reverse procedure.

  An appropriate number of legs 54 (eight in the example of FIG. 3) are arranged on the inner peripheral surface of the fixed portion 46 at equal intervals in the circumferential direction. The front end surface of the leg 54 is seated (abutted) on the outer peripheral surface 14 a of the work (main body trunk) 14. Each leg 54 can be adjusted to advance and retreat in the radial direction of the fixed portion 46, and by this advance and retreat adjustment, the cutting machine 44 is fixedly mounted on the outer peripheral surface 14 a of the workpiece 14, and centering (center axis of the cutting machine 44 is provided). Can be made to coincide with the central axis L of the workpiece 14). When the cutting machine 44 is mounted on the workpiece 14, the upper and lower divided portions that are divided are arranged at the upper and lower positions of the outer peripheral surface 14a of the workpiece 14, and the left and right hooks 52 are attached. Hook it and tighten it with bolts to connect the two parts together. As a result, the cutting machine 44 is fitted to the workpiece 14. Further, by adjusting the advance / retreat position of each leg 54, the cutting machine 44 is securely attached to the work 14 and centering is performed.

  A motor 58 serving as a power source for rotationally driving the rotating portion 48 is mounted on the upper divided portion 46 a of the fixed portion 46 via a gear box 56. The motor 58 can be mounted on the front side or the back side (58 ') of the fixed portion 46. The rotation of the motor 58 is decelerated by the gear in the gear box 56 and transmitted to the rotating unit 48. That is, the rotating portion 48 has a gear 60 coaxially formed on the outer peripheral surface thereof as shown in FIG. 4 at a place accommodated in the fixed portion 46, and the final stage gear in the gear box 56 is this The rotating portion 48 is rotated by meshing with the gear 60. As for the rotation direction of the rotation unit 48, the clockwise direction indicated by the arrow A in FIG. The gear 60 has a structure in which the gear 60 is divided into two parts integrally with the front surface (face plate) of the rotating portion 48.

  Tool post mounting portions 62 and 64 are set at positions where the rotation angles of the front surface (face plate) of the rotating portion 48 are shifted from each other by 180 °. When cutting the workpiece 14, the outer peripheral surface cutting tool post (cut-off cannula base) is mounted on the tool post mounting portions 62 and 64, respectively, and the outer peripheral surface of the work 14 is formed by two opposing cutting tools (bite). 14a is cut. When decontamination of the inner peripheral surface 14b of the work 14 is performed, an inner peripheral surface cutting tool post (inner diameter cannula base) is attached to one of the tool post attaching portions 62 and 64, and a balancer weight is attached to the other.

  The arrangement of the tool post and the cutting tool when the workpiece 14 is cut is shown in FIG. 5 (only one tool post is shown). (A) is the front view seen from the direction of the axis | shaft L of the workpiece | work 14, (b) is the top view cut | disconnected by the horizontal surface which passes along the axis | shaft L of the workpiece | work 14. FIG. In FIG. 5, the outer diameter of the workpiece 14 is shown smaller than the actual outer diameter of the main body cylinder 14. The turret 66 is an outer peripheral surface cutting turret (cut-off plane), and the base portion 68 is mounted on the turret mounting portion 62 (FIG. 3A) of the rotating portion 48 of the cutting machine 44 with a bolt 69. . A radial direction moving portion 70 is attached to and supported by the base portion 68 so as to be movable in the radial direction of the workpiece 14. A cutting tool 72 is attached to the tip of the radial direction moving part 70. The cutting edge of the cutting tool 72 faces the outer peripheral surface 14 a of the workpiece 14. The other tool post mounting part 64 (FIG. 3A) (not shown in FIG. 5) is also provided with the same outer peripheral surface cutting tool post and cutting tool, and the cutting edge of the tool faces the outer peripheral surface 14a of the workpiece 14. ing.

  In this state, when the rotating portion 48 is rotated in the forward rotation direction (the direction of arrow A in FIG. 5A), the outer peripheral surface 14a of the workpiece 14 can be cut with the two cutting tools 72. By sequentially feeding the radially moving portion 70 in the radially inward direction of the workpiece 14 (in the direction of arrow B in FIG. 5) in synchronization with the progress of the cutting, the cutting can be performed continuously, and finally the workpiece is cut into circles. Can be cut into a state. If the cut-off cannula attached to “Cutland” is used as the outer peripheral surface cutting tool post 66, the rotation of the rotating part 48 is decelerated by the gear and transmitted to the feed screw so that the radially moving part 70 is moved in the radial direction. The workpiece 14 can be cut by automatically feeding in the direction to automatically advance the cutting. For details of the automatic feeding mechanism, refer to the aforementioned Japanese Patent Application Laid-Open No. 2003-117720.

  FIG. 6 shows the arrangement of the tool post and the cutting tool when the inner peripheral surface 14b of the work 14 is decontaminated. (A) is the front view seen from the direction of the axis | shaft L of the workpiece | work 14, (b) is the top view cut | disconnected by the horizontal surface which passes along the axis | shaft L of the workpiece | work 14. FIG. In FIG. 6, the outer diameter of the workpiece 14 is shown smaller than the actual outer diameter of the main body cylinder 14. The turret 74 is an inner peripheral surface cutting turret (inner diameter cannula base), and the base 76 is a turret mounting portion 62 (or 64) of the rotating portion 48 of the cutting machine 44. It is installed with. A radial direction moving portion 80 is attached to and supported by the base portion 76 so as to be movable in the radial direction of the workpiece 14. An axially moving portion 82 is mounted and supported on the radially moving portion 80 so as to be movable in the axial direction of the workpiece 14 (direction parallel to the central axis L of the workpiece 14). A cutting tool 84 is attached to the tip of the axially moving portion 82. The cutting edge of the cutting tool 84 faces the inner peripheral surface 14 b of the work 14.

  When the rotating part 48 is rotated in the normal rotation direction (the direction of arrow A in FIG. 6A) in this state, the inner peripheral surface 14b of the workpiece 14 can be cut with the cutting tool 84. Synchronously with the rotation of the rotating part 48, the axially moving part 82 is sequentially sent in the axially back direction of the workpiece 14 (in the direction of arrow C in FIG. 6B) (feeding at a speed that does not cause a gap in cutting). Thus, cutting can be performed continuously. In this way, the radioactive substance attached to the inner peripheral surface 14b can be removed entirely along with the cutting waste. The axial length (cutting width, that is, decontamination width) that can be cut without moving the mounting position of the inner peripheral surface cutting tool post 74 can be set by the length of the axial movement portion 82, for example, The length from the opening end 14c to the depth of about 1 m can be set. If the inner diameter cutter table attached to “Cutland” is used as the inner peripheral surface cutting tool post 74, the rotation of the rotating portion 48 is reduced by the gear and transmitted to the feed screw, so that the axial direction moving portion 82 is pivoted. Cutting can be automatically advanced by automatically feeding in the back direction. Further, the blade edge adjustment (adjustment of the cutting depth) in the radial direction (direction of arrow D in FIG. 6) is performed by manually operating the radial position of the radial moving portion 80 in the case of the inner diameter canter stand attached to “Cut Land”. This can be done by adjusting.

  Here, a method of performing decontamination and disassembly of the feed water heater 10 of FIG. 2 using the cutting machine 44 of FIGS. 3 to 6 described above will be described. The procedure of decontamination and dismantling work will be described with reference to FIG. 1 and FIGS. In this operation, the water chamber body 18 is first cut using the cutting machine 44 (step S1 in FIG. 1). That is, as shown in step (1) in FIG. 7, the cutting machine 44 is mounted in the vicinity of the tube plate 16, and the cutting tool C for cutting the cutting edge 72 is cut using the outer peripheral surface cutting tool post 66 (FIG. 5). It faces the outer peripheral surface 14a (position closer to the body of the water chamber than the tube plate 16). In this state, the rotating portion 48 of the cutting machine 44 is rotated, and the cutting tool C1 is sequentially cut over the entire circumference by sequentially feeding the cutting tool 72 in the radial direction of the feed water heater 10, thereby cutting the water chamber body 18. To do.

  When the water chamber barrel 18 is cut, as shown in step (2) of FIG. 7, the cutting machine 44 is moved in the axial direction in the back direction (in the back direction from the tube sheet 16 and in the back direction from the next scheduled cutting position C2). ("Back direction" refers to the left direction in Figs. 7 and 8) and moved to the position of the main body cylinder 14 and reattached, and similarly using the outer peripheral surface cutting tool post 66, The cutting tool 72 is made to face the scheduled cutting position C2. In this state, the rotating portion 48 of the cutting machine 44 is rotated and the cutting tool 72 is sequentially fed in the radial direction of the feed water heater 10 to sequentially cut the planned cutting position C2 over the entire circumference. 14 is cut (step S2 in FIG. 1). Note that the main body barrel portion 14-1 is fixed and supported on an appropriate support base 86 so that the main body barrel portion 14-1 does not fall off during cutting.

  When the main body cylinder 14-1 is cut, as shown in step (3) of FIG. 7, the remaining part of the main body cylinder 14 is rolled on the floor 12 with the legs 40 and 42 with wheels, and the main body cylinder portion is cut. It is moved in the direction away from 14-1. As a result, the heat transfer tube bundle 26 integrally connected to the tube plate 16 and the cut main body cylinder portion 14-1 is extracted from the main body cylinder 14 (step S3 in FIG. 1).

  Subsequently, while the mounting position of the cutting machine 44 remains unchanged, the tool post is replaced with an inner peripheral surface cutting tool post 74 (FIG. 6), and the inner peripheral surface 14b of the main body barrel 14 is cut. That is, as shown in step (4) of FIG. 8, the cutting tool 84 is positioned at the opening end portion 14 c of the main body cylinder 14 so as to face the inner peripheral surface 14 b of the main body cylinder 14. In this state, the rotating portion 48 of the cutting machine 44 is rotated and the cutting tool 84 is sequentially fed in the axial direction of the main body cylinder 14 until the next scheduled cutting position C3 (or slightly behind the planned cutting position C3). The entire circumference of the inner circumferential surface 14b is cut over the entire surface over a predetermined width (for example, 1 m). In this manner, the entire inner peripheral surface 14b of the main body barrel portion 14-2 is decontaminated up to the next scheduled cutting position C3 (step S4 in FIG. 1).

  Further, the tool post is replaced with the outer peripheral surface cutting tool post 66, and as shown in step (5) of FIG. 8, the cutting machine 44 is moved to the position of the main body cylinder 14 on the back side from the next scheduled cutting position C3. Is moved and reattached (step S5 in FIG. 1), and the cutting tool 72 faces the scheduled cutting position C3. In this state, the rotating portion 48 of the cutting machine 44 is rotated and the cutting tool 72 is sequentially fed in the radial direction of the main body cylinder 14 to sequentially cut the planned cutting position C3 over the entire circumference, and at the position C3, the main body cylinder 14 is cut. Is cut (step S6 in FIG. 1). Note that the main body cylinder 14 is fixed and supported on the support base 88 at an appropriate interval so that the main body cylinder 14 does not fall off during cutting.

  Subsequently, while the mounting position of the cutting machine 44 is kept as it is, the tool post is replaced with the inner peripheral surface cutting tool post 74 and the inner peripheral surface 14b of the main body cylinder 14 is cut. That is, as shown in step (6) of FIG. 8, the cutting tool 84 is positioned at the new opening end portion 14 c ′ of the main body cylinder 14 and is made to face the inner peripheral surface 14 b of the main body cylinder 14. In this state, the rotating portion 48 of the cutting machine 44 is rotated and the cutting tool 84 is sequentially fed in the axial direction of the main body cylinder 14 until the next scheduled cutting position C4 (or slightly behind the planned cutting position C4). The entire circumference of the inner circumferential surface 14b is cut over the entire surface over a predetermined width (for example, 1 m). In this manner, the entire inner peripheral surface 14b of the main body barrel portion 14-3 is decontaminated up to the next scheduled cutting position C4 (step S4 in FIG. 1).

  Thereafter, the movement of the cutting machine 44 (step S5 in FIG. 1), cutting of the main body cylinder 14 (step S6), and decontamination of the entire inner peripheral surface 14b of the main body cylinder 14 (step S4) are repeated. .., Cn are sequentially cut into main body barrel portions 14-3, 14-4,..., 14-n. When the cutting at the final cutting position Cn is completed (step S7 in FIG. 1), the body endplate 36 (14-n) and the water chamber body 18 are decontaminated by an appropriate method (step S8 in FIG. 1). The decontaminated and disassembled water chamber barrel 18, main body barrel 14, and body endplate 36 are recycled (step S9 in FIG. 1). Cutting waste is discarded as radioactive waste. The inner peripheral surfaces of the steam inlet 28, the drain outlet 30, the fuselage relief valve seat 32, the fuselage air vent seat 34, and the like provided in the main body barrel 14 are separately decontaminated by an appropriate method.

  A method for decontamination and disassembly of the heat transfer tube bundle 26 extracted from the main body cylinder 14 will be described. As shown in FIG. 9, the heat transfer tube bundle 26 extracted from the main body portion 14 is integrally connected to the tube plate 16 and the cut main body barrel portion 14-1. Therefore, using a band saw, a wire saw, or the like, the heat transfer tube bundle 26 is cut at a position P1 close to the main body cylinder 14-1 and a position P2 close to the portion bent in the U shape, and separated into individual heat transfer tubes. (Step S10 in FIG. 1). Next, the individual heat transfer tubes are put into, for example, a rotating cylindrical brush, the outer peripheral surface is brushed, and the radioactive material adhering to the outer peripheral surface is scraped to decontaminate (step S11). ). Furthermore, by inserting a rotating brush into the opening of each heat transfer tube, the inner peripheral surface is brushed and the radioactive material adhering to the inner peripheral surface is scraped off for decontamination (same as above). Step S12). When the decontamination is completed, each heat transfer tube is cut into halves (step S13), and further cut into short chips 26a as shown in FIG. 10 (step S14) and recycled (step S15). The cutting scraps scraped off with the brush are discarded as radioactive waste. In addition, also about the part bent by the U shape of each heat exchanger tube, the outer peripheral surface and an inner peripheral surface are decontaminated by brushing, and it cuts into half and cuts into chips and recycles. Further, the remaining tube plate 16 and main body barrel portion 14-1 are also decontaminated and recycled by an appropriate method.

  In the above embodiment, the inner peripheral surface 14b is cut from the opening end side to the back side of the main body barrel 14, but conversely the inner peripheral surface 14b from the back side to the opening end side. Can also be cut. In the above-described embodiment, the inner peripheral surface 14b is cut by sequentially feeding the axially moving portion 82 toward the back in the axial direction of the workpiece 14 while continuously rotating the rotating portion 48. Instead of this, the rotation of the rotating part 48 is stopped and the axially moving part 82 is transferred from the opening end part 14c of the work 14 in the axially rearward direction by a predetermined distance. Then, the rotary part 48 is rotated by a small amount and stopped. Then, the axially moving part 82 is again transferred from the opening end part 14c of the work 14 in the axially back direction by a predetermined distance and then cut. It is also possible to cut the inner peripheral surface 14b by repeating this operation until the rotating portion 48 makes one round (that is, to repeat axial cutting over the entire circumference of the inner peripheral surface 14b). In the above embodiment, the outer peripheral surface cutting tool post 66 feeds the cutting tool 72 only in the radial direction of the workpiece 14, but it can move in the axial direction and is wider than the thickness of the cutting tool 72. Cutting can also be performed by cutting with the groove width. In the embodiment, the cut portion is cut after the inner peripheral surface 14b is cut, but the inner peripheral surface 14b of the cut portion is cut after the cut. You can also.

  In the above-described embodiment, the case of performing decontamination and dismantling of the feed water heater of the nuclear power plant has been described. However, the present invention is not limited thereto, and heat exchange in which the nuclear power plant steam generator and other inner peripheral surfaces are radioactively contaminated is described. Decontamination and disassembly can be performed on cylindrical structures such as vessels and piping by the method of the present invention.

It is a flowchart which shows the procedure which performs the decontamination and dismantling of the feed water heater 10 of FIG. 2 using the cutting machine 44 of FIGS. It is a longitudinal cross-sectional side view which shows the structure of the feed water heater of a nuclear power plant. It is the front view and right view which show an example of the cutting machine used for decontamination and the dismantling of the main body cylinder 14 of the feed water heater of FIG. It is a perspective view which shows the gear formed coaxially in the rotation part 48 of the cutting machine of FIG. It is a figure which shows arrangement | positioning of the tool post and the cutting blade when cutting the main body cylinder 14 of the feed water heater of FIG. 2 using the cutting machine of FIG. 3, (a) is a front view seen from the axial direction, (B) is the top view cut | disconnected by the horizontal surface which passes along an axis | shaft. It is a figure which shows arrangement | positioning of the tool post and the cutting blade when decontaminating the main body cylinder 14 of the feed water heater of FIG. 2 using the cutting machine of FIG. 3, (a) is the front view seen from the axial direction (B) is the top view cut | disconnected by the horizontal surface which passes along an axis | shaft. It is explanatory drawing of the main processes of the procedure of FIG. FIG. 8 is an explanatory diagram showing a continuation process of FIG. 7. It is a figure which shows an example of the cutting position of the heat exchanger tube bundle. It is a perspective view which shows the chip | tip by which the heat exchanger tube was cut | disconnected by half.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Feed water heater (heat exchanger), 14 ... Main body trunk | drum (cylindrical structure), 14-1, 14-2, ..., 14-n ... Main body trunk part cut | disconnected or cut | disconnected, 14a ... outer peripheral surface, 14b ... inner peripheral surface, 14c ... open end of cylindrical structure, 14c '... new open end of cylindrical structure, 16 ... tube plate, 26 ... heat transfer tube bundle, 44 ... cutting , 46 ... fixed part, 48 ... rotating part, 58 ... motor (power), 66 ... outer peripheral surface cutting tool post, 72, 84 ... cutting tool (cutting tool), 74 ... inner peripheral surface cutting tool post, C1, C2,..., Cn: scheduled cutting position, L: central axis of the cylindrical structure.

Claims (4)

A fixed portion mounted on the outer peripheral surface so that the inner peripheral surface surrounds the outer peripheral surface of the radioactively contaminated cylindrical structure, and an outer periphery of the cylindrical structure that is rotatably supported by the fixed portion and driven by power Using a cutting machine comprising a rotating part that rotates around a surface, a tool post mounted on the rotating part, and a cutting tool mounted on the tool post,
A cutting blade is inserted from the opening end of the cylindrical structure so that the cutting blade faces the inner peripheral surface of the cylindrical structure, the rotating portion is rotated, and the cutting blade is moved to the axis of the cylindrical structure. Cutting the inner peripheral surface of the cylindrical structure with the cutting blade by sending in the direction to decontaminate the inner peripheral surface,
A cutting blade is made to face the outer peripheral surface of the cylindrical structure, the rotating portion is rotated, and the cutting blade is fed inward in the radial direction of the cylindrical structure so that the cylindrical structure is moved with the cutting blade. A method for decontamination and disassembly of a cylindrical structure in which the cylindrical structure is disassembled by cutting and cutting from the outside ,
When performing decontamination of the inner peripheral surface, as the tool post, a cutting tool is inserted from the opening end of the cylindrical structure so that the cutting tool faces the inner peripheral surface of the cylindrical structure, and Using an inner peripheral surface cutting tool post capable of sending a cutting tool in the axial direction of the cylindrical structure,
When the dismantling is performed, as the tool post, the cutting tool is used for cutting an outer peripheral surface, which allows the cutting tool to face the outer peripheral surface of the cylindrical structure and feed the cutting tool in the radially inward direction of the cylindrical structure. Use the tool post,
Performing the decontamination over a predetermined width in the axial direction from the opening end of the cylindrical structure on the inner peripheral surface of the cylindrical structure,
After the decontamination, the mounting position of the fixed portion of the cutting machine with respect to the outer peripheral surface of the cylindrical structure is set to the back side in the axial direction from the planned cutting position set at the position where the inner peripheral surface has been decontaminated. To perform the cutting at the planned cutting position,
After the cutting, the removal position of the fixed portion of the cutting machine is left as it is over the predetermined width in the axial direction from the new opening end of the cylindrical structure on the inner peripheral surface of the cylindrical structure. A method for decontamination and disassembly of a cylindrical structure for dyeing. The decontamination step, the moving step of the fixed part, decontamination and dismantling method according to claim 1 cylindrical structure according to repeat as appropriate number of cycles of the cutting process. A method for decontaminating and dismantling a heat exchanger in which the inside of a cylindrical main body is radioactively contaminated,
A fixed portion mounted on the outer peripheral surface so as to surround the outer peripheral surface of the main body barrel; a rotating portion that is rotatably supported by the fixed portion and rotates around the outer peripheral surface of the main body barrel by power; and the rotation Using a cutting machine equipped with a tool post mounted on the part and a cutting tool mounted on the tool post,
Attach the fixed part of the cutting machine to the position on the side of the main body barrel, which is behind the tube sheet, on which the heat transfer tube bundle is disposed,
Use of an outer peripheral surface cutting tool post capable of causing the cutting tool to face the outer peripheral surface of the main body cylinder and feeding the cutting tool radially inward of the main body cylinder as the tool post, and the mounting position of the fixed portion And a position of the tube sheet between the cutting edge and the outer peripheral surface of the main body cylinder, the cutting blade is rotated, and the rotating portion is rotated and the cutting blade is sent inward in the radial direction of the main body cylinder. Cutting the main body cylinder from the outside with a cutting blade and cutting it,
After the cutting, the heat transfer tube bundle is extracted from the main body body together with the tube plate,
After the extraction, the mounting position of the fixed part is left as it is, and the cutting tool is inserted from the opening end formed by cutting the main body cylinder as the tool post so that the cutting tool faces the inner peripheral surface of the main body cylinder. And using an inner peripheral surface cutting turret capable of feeding the cutting tool in the axial direction of the main body cylinder, inserting the cutting tool from the opening end of the main body cylinder, and inserting the cutting tool into the inner side of the main body cylinder. Decontamination of the inner peripheral surface by cutting the inner peripheral surface of the main body cylinder with the cutting blade by causing the cutting blade to face the peripheral surface, rotating the rotating portion and sending the cutting blade in the axial direction of the main body cylinder Over a predetermined width in the axial direction from the opening end,
After the decontamination, the mounting position of the fixed portion of the cutting machine with respect to the outer peripheral surface of the main body cylinder is set to the back side in the axial direction from the next scheduled cutting position set to the position where the inner peripheral surface has been decontaminated And using the outer peripheral surface cutting turret, causing the cutting tool to face the outer peripheral surface of the main body barrel at the planned cutting position, rotating the rotating portion and causing the cutting tool to move in the radial direction of the main body cylinder. Cutting the main body cylinder from the outside with the cutting blade by sending it inwardly,
After the cutting, the mounting position of the fixed part is kept as it is, and the cutting tool for cutting the inner peripheral surface is used, and the cutting tool is inserted from a new opening end of the main body cylinder so that the cutting tool is inserted into the main body cylinder. Decontamination of the inner peripheral surface by cutting the inner peripheral surface of the main body cylinder with the cutting blade by causing the cutting blade to face the peripheral surface, rotating the rotating portion and sending the cutting blade in the axial direction of the main body cylinder Over a predetermined width in the axial depth direction from the new opening end,
Thereafter, a method for decontamination and dismantling of a cylindrical structure in which a cycle of the fixing part moving step, cutting step, and decontamination step is repeated as appropriate. 4. The decontamination and dismantling of the cylindrical structure according to claim 3, wherein the extracted heat transfer tube bundle is cut and separated into individual heat transfer tubes, and the outer peripheral surface and the inner peripheral surface are decontaminated for each heat transfer tube. Method.

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