Supporting metallic material removal method

Abstract

To provide a supporting metallic material removal method capable of appropriately removing a supporting metallic material from a supporting column.SOLUTION: A supporting metallic material removal method removes a supporting metallic material from a supporting column, in which a catch configured to support a thermocouple lead-out pipe is mounted inside an upper end part of the supporting column having a cylindrical shape, with a lower end face of the supporting metallic material having a cylindrical shape connected via a weld zone at an upper end face. The supporting metallic material removal method includes: a step of cutting a lower end part of the supporting metallic material at a position upward from the catch and separating from the supporting column; a step of cutting an upper region of the lower end part of the supporting metallic material remaining on a side of the supporting column at a thickness smaller by a first specified quantity than a plate thickness to remove from the supporting column while leaving a residual ring; a step of cutting the lower end part of the supporting metallic material including the weld zone at a thickness thicker by a second specified quantity than the plate thickness to remove from the supporting column; and a step of removing the residual ring from the catch.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a support hardware removal method for removing a support hardware from a support pole. [Background technology]

[0002] In a nuclear power plant, a containment vessel is erected on solid ground such as bedrock, and a nuclear reactor is disposed inside the containment vessel. The reactor is configured by disposing reactor internals such as fuel inside the reactor vessel. As reactor internals, a plurality of tubular thermocouple withdrawal pipe support columns are disposed between an upper core support plate and an upper core plate. Tubular support metal fittings are connected to the upper ends of the thermocouple withdrawal pipe support columns. Thermocouple withdrawal pipes are disposed inside the thermocouple withdrawal pipe support columns and the support metal fittings. The support metal fittings need to be replaced as necessary. For example, Patent Document 1 describes a technology for replacing such reactor internals. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-264206 Summary of the Invention [Problem to be solved by the invention]

[0004] A stopper plate that supports the thermocouple lead pipe is attached to the inside of the upper end of the thermocouple lead pipe support column, and the lower end of a support metal is welded to the end face. When replacing the support metal, the welded portion to the thermocouple lead pipe support column is machined off, and then the support metal is removed from the thermocouple lead pipe support column. However, when the support metal is welded to the thermocouple lead pipe support column, the lower end may be deformed by thermal distortion and become stuck to the stopper plate. In this case, it becomes difficult to remove the support metal by simply machined off the welded portion between the support metal and the thermocouple lead pipe support column.

[0005] The present disclosure is intended to solve the above-mentioned problems and aims to provide a support hardware removal method that can properly remove support hardware from a support column. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, the support hardware removal method of the present disclosure includes a support hardware removal method in which a stopper plate supporting a thermocouple extraction tube is attached to the inside of the upper end of a cylindrical support pillar, and the lower end surface of the cylindrical support pillar is connected to the upper end surface via a weld, and the support hardware removal method includes the steps of cutting the lower end of the support pillar at a position above the stopper plate to separate it from the support pillar, cutting the upper region of the lower end of the support pillar remaining on the support pillar side by a thickness that is a first predetermined amount less than the plate thickness to leave a residual ring and removing it from the support pillar, cutting the lower end of the support pillar including the welded portion by a thickness that is a second predetermined amount more than the plate thickness to remove it from the support pillar, and removing the residual ring from the stopper plate. [Effects of the Invention]

[0007] According to the support hardware removal method disclosed herein, the support hardware can be properly removed from the support column. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a longitudinal cross-sectional view showing a pressurized water reactor. [Figure 2] FIG. 2 is a schematic cross-sectional view showing the connection structure between the support column, the stopper plate, and the support metal fitting. [Figure 3] FIG. 3 is a schematic diagram showing the support metal removal method of this embodiment. [Figure 4] FIG. 4 is a schematic diagram showing the support metal removal method. [Figure 5] FIG. 5 is a schematic diagram showing the support metal removal method. [Figure 6] FIG. 6 is a schematic diagram showing the support metal removal method. [Figure 7]FIG. 7 is a schematic diagram showing the support metal removal method. [Figure 8] FIG. 8 is a schematic diagram showing the support metal removal method. [Figure 9] FIG. 9 is a schematic diagram showing the support metal removal method. [Figure 10] FIG. 10 is a schematic diagram showing the support metal removal method. DETAILED DESCRIPTION OF THE INVENTION

[0009] Preferred embodiments of the present disclosure will be described in detail below with reference to the drawings. Note that the present disclosure is not limited to these embodiments, and when there are multiple embodiments, the present disclosure also includes configurations that combine the embodiments. Furthermore, the components in the embodiments include those that can be easily imagined by a person skilled in the art, those that are substantially identical, and those that are within the so-called equivalent range.

[0010] <Pressurized water reactor> FIG. 1 is a longitudinal cross-sectional view showing a pressurized water reactor.

[0011] Although not shown, the nuclear power plant has a nuclear reactor and a steam generator arranged in a reactor containment vessel, and a steam turbine power generation facility. The nuclear reactor in this embodiment is a pressurized water reactor (PWR). However, the nuclear reactor may be any type of nuclear reactor, such as a boiling water reactor (BWR) or a fast breeder reactor (FBR).

[0012] As shown in FIG. 1, in a pressurized water reactor 10, a reactor vessel 11 is composed of a reactor vessel main body 12 and a reactor vessel lid 13 attached to the top so that reactor internals can be inserted inside, and the reactor vessel lid 13 is fixed to the reactor vessel main body 12 by a plurality of stud bolts 14 and nuts 15 so that it can be opened and closed.

[0013] The reactor vessel body 12 has a cylindrical shape that is open at the top and closed at the bottom, forming a hemispherical shape, and is provided with an inlet nozzle 16 at the top for supplying light water as primary coolant and an outlet nozzle 17 for discharging the light water. A core barrel 18 is disposed inside the reactor vessel body 12, and its upper part is supported by the inner wall surface of the reactor vessel body 12. An upper core support plate 19 is disposed inside the reactor vessel body 12, and its upper part is supported by the upper part of the core barrel 18. An upper core plate 20 is suspended and supported from the upper core support plate 19 by a plurality of core support rods 21.

[0014] A lower core support plate 22 is supported below the core barrel 18, and the outer periphery of the lower core support plate 22 is positioned and supported by positioning members 23 on the inner wall surface of the reactor vessel body 12. A lower core plate 24 is supported below the core barrel 18. A core 25 is formed by arranging a large number of fuel assemblies 26, and a large number of control rods 27 are arranged inside, and the control rods 27 are insertable into the fuel assemblies 26. A large number of control rod cluster guide tubes 28 are fixed to the upper core support plate 19, and the control rods 27 can be inserted therein. The reactor vessel lid 13 is hemispherical, and a control rod drive mechanism 29 is arranged therein. A plurality of control rod cluster drive shafts 30 are inserted into the control rod cluster guide tubes 28, and the control rods 27 are connected to the lower ends thereof. The control rod drive mechanism 29 controls the reactor power by inserting and withdrawing each control rod 27 into and from the core 25.

[0015] Furthermore, a detector guide device 31 is disposed inside the reactor vessel 11. The detector guide device 31 guides a neutron flux detector (not shown) from an instrumentation nozzle 32 on the reactor vessel lid 13 to the core 25 (fuel assemblies 26) through a guide member 33. The neutron flux detector can measure the neutron level and distribution (neutron flux). Specifically, the detector guide device 31 guides the neutron flux detector (not shown) from the instrumentation nozzle 32 on the reactor vessel lid 13 to the core 25 (fuel assemblies 26) through the guide member 33 and a guide thimble (not shown) fixed to the lower end of the guide member 33.

[0016] <Connection structure between support column, stopper plate and support hardware> FIG. 2 is a schematic cross-sectional view showing the connection structure between the support column, the stopper plate, and the support metal fitting.

[0017] As shown in Figures 1 and 2, the support column (thermocouple withdrawal pipe support column) 51 has a cylindrical shape, and its lower end is supported by the upper core support plate 19. The support column 51 has a support portion 51a formed on the inside of its upper end, where the inner diameter is larger. The support hardware 52 has a cylindrical shape, and its upper end is supported by the reactor vessel lid 13. An upper end surface 51b of the support column 51 and a lower end surface 52a of the support hardware 52 are in contact with each other and are joined by a welded portion 54. The outer diameter and inner diameter of the upper end of the support column 51 are the same as those of the lower end of the support hardware 52.

[0018] The stopper plate 53 has a cylindrical shape and is attached to and supported by the support portion 51a at the upper end of the support column 51. The stopper plate 53 supports the upper end of the lower thermocouple lead pipe 61 and also supports the lower end of the upper thermocouple lead pipe 62. That is, the upper end of the lower thermocouple lead pipe 61 is supported by penetrating the stopper plate from below. The lower end of the upper thermocouple lead pipe 62 is supported by the stopper plate 53. The upper end of the lower thermocouple lead pipe 61 and the lower end of the upper thermocouple lead pipe 62 are supported by the stopper plate 53 and communicate with each other. The lower thermocouple lead pipe 61 and the upper thermocouple lead pipe 62 movably support thermocouples (not shown) therein.

[0019] <How to remove the support metal fittings> Figures 3 to 10 are schematic diagrams showing the support metal removal method. Note that the lower thermocouple lead pipe 61 and the upper thermocouple lead pipe 62 are omitted from Figures 3 to 10. In Figures 3 to 10, the left side shows the state before the work, and the right side shows the state after the work.

[0020] As shown in Figures 2 and 3, in the support hardware removal method of this embodiment, a stopper 53 that supports the lower thermocouple lead-out pipe 61 and the upper thermocouple lead-out pipe 62 is attached to the inside of the upper end of the support column 51, and the lower end surface 52a of the support hardware 52 is connected to the upper end surface 51b via a welded portion 54, and the support hardware 52 is removed from the support column 51.

[0021] As shown in Figure 3, first, the lower end of the support metal 52 is cut at a position above the stopper plate 53 to separate it from the support column 51. That is, the cutting tool 101 is moved so that its tip is positioned above the upper end surface of the stopper plate 53 and facing the outer peripheral surface of the support metal 52. From this state, the cutting tool 101 is moved in the circumferential direction of the support metal 52 and toward the center of the support metal 52 to cut and separate the support metal 52. At this time, it is preferable to cut the lower end of the support metal 52 so that after cutting, the upper end surface of the lower end 52A of the support metal 52 remaining on the support column 51 side and the upper end surface of the stopper plate 53 are approximately aligned in the height direction.

[0022] 4 and 5, next, the upper region of the lower end portion 52A of the support metal 52 remaining on the support column 51 side is cut away by a thickness that is a first predetermined amount less than the plate thickness, and the remaining ring 52B is removed from the support column 51. That is, as shown in Fig. 4, the cutting tool 101 is moved so that the position of the upper end face is aligned with the position of the upper end face of the stopper plate 53. From this state, the cutting tool 101 is moved in the circumferential direction of the support metal 52 and toward the center of the support metal 52 to cut the support metal 52.

[0023] At this time, the cutting depth (cutting thickness of the support metal 52) by the cutting tool 101 is set to a depth (thickness) that is a first predetermined amount less than the thickness of the support metal 52. The first predetermined amount is, for example, 0.3 mm. Furthermore, the cutting height T1 by the cutting tool 101 is slightly shorter than the height of the cutting tool 101. Because the cutting tool 101 cuts to a depth that is less than the thickness of the support metal 52, a residual ring 52B of the first predetermined thickness remains on the outer peripheral surface side of the stopper plate 53.

[0024] As shown in FIG. 5 , the cutting tool 101 is lowered by a height T1, and similarly, the cutting tool 101 is moved in the circumferential direction of the support metal 52 and toward the center of the support metal 52 to cut the support metal 52. At this time, the cutting depth (cutting thickness of the support metal 52) by the cutting tool 101 is set to a depth (thickness) that is a first predetermined amount less than the thickness of the support metal 52. Also, the cutting height T1 by the cutting tool 101 is slightly shorter than the height of the cutting tool 101. Because the cutting tool 101 cuts to a depth less than the thickness of the support metal 52, a residual ring 52B of height T2 and the first predetermined thickness remains on the outer peripheral surface of the stopper plate 53. At this time, at least the deepest portion of the welded portion 54 is left uncut by the cutting tool 101.

[0025] As shown in FIG. 6 , the lower end 52A of the support metal 52, including the welded portion 54, is then removed from the support column 51 by cutting a thickness that is a second predetermined amount greater than the plate thickness. That is, the cutting tool 101 is lowered by a height T1, and the cutting tool 101 is moved circumferentially around the support metal 52 and the support column 51 while also moving toward the center of the support metal 52 and the support column 51, thereby cutting the support metal 52 and the support column 51, including the welded portion 54. At this time, the cutting depth (cutting thickness of the support metal 52 and the support column 51) by the cutting tool 101 is set to a depth (thickness) that is a second predetermined amount greater than the cutting thickness of the support metal 52 and the support column 51. The second predetermined amount is, for example, 0.1 mm. The cutting height T1 by the cutting tool 101 is slightly shorter than the height of the cutting tool 101.

[0026] The cutting tool 101 cuts the lower end 52A of the support metal 52, including the welded portion 54, and the upper end of the support column 51 by a thickness that is a second predetermined amount greater than the plate thickness, thereby separating the remaining ring 52B from the support column 51. In other words, by cutting the support metal 52 and the support column 51, including the welded portion 54, by a thickness that is a second predetermined amount greater than the plate thickness, the surface of the stopper plate 53 is cut by the second predetermined amount.

[0027] 7, the remaining ring 52B is now removed from the fastener 53. That is, since the remaining ring 52B has been separated from the support column 51, it can be removed from the fastener 53. The removal of the remaining ring 52B from the fastener 53 may be performed using a predetermined tool.

[0028] As shown in Fig. 8, the cutting tool 101 is then lowered and moved to a position facing the upper end of the support column 51. Here, as shown in Fig. 9, a groove is made on the upper end of the support column 51. That is, the cutting tool 102 is moved in the circumferential direction of the support column 51 and also moved toward the center of the support column 51, and an inclined groove surface 51c is formed on the upper end of the support column 51. The groove surface 51c has an angle θ with respect to the horizontal plane.

[0029] The support metal removal method is completed by the above-mentioned work, and as shown in Figure 10, a new support metal 55 is placed facing the groove surface 51c of the support column 51 and is connected to it by a welded portion 56. This work completes the replacement work of the support metal 55 (52).

[0030] [Effects of this embodiment] The support hardware removal method of the first embodiment includes the steps of cutting the lower end of the support hardware 52 at a position above the stopper 53 to separate it from the support column 51, cutting the upper region of the lower end of the support hardware 52 remaining on the support column 51 side by a thickness that is a first predetermined amount less than the plate thickness to remove it from the support column 51 while leaving a remaining ring 52B, cutting the lower end of the support hardware 52 including the welded portion 54 by a thickness that is a second predetermined amount more than the plate thickness to remove it from the support column 51, and removing the remaining ring 52B from the stopper 53.

[0031] According to the support hardware removal method of the first aspect, after cutting and removing the support hardware 52, the lower end of the support hardware 52 remaining on the support column 51 side is cut away to leave the residual ring 52B, and then the lower end of the support hardware 52 including the welded portion 54 is cut away, thereby removing the support hardware 52 while leaving only the portion of the support hardware 52 fitted into the stopper plate 53 at the welded portion 54, i.e., the residual ring 52B. The work is then completed by removing the residual ring 52B later. As a result, the support hardware 52 can be properly removed from the support column 51 even if the support hardware is stuck to the stopper plate 53 due to deformation during welding.

[0032] The support metal removal method according to the second aspect is the support metal removal method according to the first aspect, and further comprises cutting the lower end of the support metal 52 above the stopper plate 53 so that the upper end face of the lower end of the support metal 52 remaining on the support column 51 side after cutting is approximately aligned in the height direction with the upper end face of the stopper plate 53. This makes it easy to perform the cutting work that leaves the remaining ring 52B on the stopper plate 53.

[0033] The support hardware removal method according to the third aspect is the support hardware removal method according to the first or second aspect, and further comprises cutting the lower end of the support hardware 52, including the welded portion 54, by a thickness that is a second predetermined amount greater than the plate thickness, thereby cutting the surface of the stopper plate 53. This allows the connection between the remaining ring 52B and the support column 51 to be properly released.

[0034] The support hardware removal method according to the fourth aspect is the support hardware removal method according to any one of the first to third aspects, and further includes groove preparation on the upper end of the support column 51. This makes it possible to easily connect a new support hardware 55 to the groove surface 51c of the support column 51, and perform the replacement work of the support hardware 55 (52). [Explanation of symbols]

[0035] 10 Pressurized Water Reactor 11 Reactor vessel 12 Reactor vessel body 13 Reactor vessel lid 18 Core tank 19 Upper core support plate 20 Upper core plate 21 Core support rod 25 reactor core 26 Fuel assembly 51 Support column 52,55 Support hardware 53 Clasp 54,56 Welded parts

Claims

1. A support metal removal method is provided in which a stopper for supporting a thermocouple lead pipe is attached to the inside of the upper end of a cylindrical support pole, and the lower end surface of a cylindrical support metal is connected to the upper end surface via a weld, and the support metal is removed from the support pole, cutting the lower end of the support metal at a position above the stopper to separate it from the support pole; a step of removing an upper region of the lower end of the support metal remaining on the support pole side by a thickness that is a first predetermined amount less than the plate thickness, and leaving a residual ring; a step of removing the lower end of the support metal including the welded portion from the support column by cutting a thickness that is a second predetermined amount greater than the plate thickness; removing the retainer ring from the staple; A support metal removal method comprising:

2. The lower end of the support metal is cut at a position above the stopper so that the upper end surface of the lower end of the support metal remaining on the support column side after cutting and the upper end surface of the stopper are approximately aligned in the height direction. The method for removing a support metal fitting according to claim 1.

3. The lower end of the support metal, including the welded portion, is cut by a thickness that is a second predetermined amount greater than the plate thickness, thereby cutting the surface of the stopper plate. The method for removing a support metal fitting according to claim 1.

4. Beveling is performed on the upper end of the support pillar. A method for removing a support metal fitting according to any one of claims 1 to 3.

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