Underwater remote replacement method for lock nut of support column of pressurized water reactor in-core component

Abstract

The application relates to a method for underwater remote replacement of a locking nut of a support column of an in-core component of a pressurized water reactor, and belongs to the technical field of maintenance, which comprises a method for dismounting an old locking nut and a method for mounting a new locking nut. The application establishes a coordinate system for replacement of the locking nut of the basket assembly of the pressurized water reactor, proposes the concept of a working channel for replacement of the locking nut of the basket assembly of the pressurized water reactor, and establishes the concept of a maintenance platform. The application solves the problem of replacement of the locking nut of the support column of the basket assembly of the pressurized water reactor in a nuclear power plant under the conditions of high irradiation, long distance and underwater, and has high accuracy, can maximize the distance from the high irradiation environment, and greatly reduces the irradiation dose of the operator.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of maintenance, in particular to a method for underwater remote replacement of a locking nut of a support column of an in-core component of a pressurized water reactor. BACKGROUND

[0002] The in-core component in the pressurized water reactor pressure vessel of a nuclear power plant is a core part of the nuclear reactor, and the lower basket assembly, which is one of the constituent parts, plays a supporting, fixing and guiding role. The basket assembly is composed of a core bottom plate, a flow distribution plate, a basket bottom plate, a break prevention support plate, a break prevention bottom plate, a support column and a connecting plate. The support column connects the core bottom plate, the flow distribution plate and the basket bottom plate and is fixed through a locking nut with an anti-loosening structure at the lower end.

[0003] When the anti-loosening structure of the locking nut is subjected to nuclear irradiation and water flow impact for a long time, the defect site cannot withstand the flow-induced vibration load and thermal load, and fatigue fracture occurs at the anti-loosening position. The failure of the structural component reduces the natural frequency of the basket assembly support column, causing the flow-induced vibration load to further increase. In addition, the loosened parts produce friction and vibration under the impact of the water flow, further increasing the damage to the support column, thereby affecting the support strength of the adjacent plates and the insertion of the neutron flux tube.

[0004] Therefore, it is necessary to regularly inspect the anti-loosening structure of the locking nut of the support column and disassemble and update the locking nut with the risk of loosening. The common method for replacing the nut with the anti-loosening structure at present is to manually cut off the anti-loosening structure and directly replace the nut using a corresponding wrench, and then weld or fix the anti-loosening structure.

[0005] Due to the presence of a large amount of radiation in the in-core component, remote operation is required in the deep water pool during maintenance and repair. Moreover, the basket bottom plate has a diameter of more than three meters, and there are dozens of locking nuts of the support column with different positions, so personnel and simple tools cannot complete the replacement of the locking nuts.

[0006] The conventional method cannot meet the requirements, and a new safe and precise replacement method and equipment support are needed to meet the replacement of the locking nut of the support column of the in-core component of the pressurized water reactor under high irradiation, long distance and underwater conditions. SUMMARY

[0007] The present application aims to provide a method for underwater remote replacement of a locking nut of a support column of an in-core component of a pressurized water reactor, which realizes safe, error-free and systematic replacement of the locking nut of the support column of the in-core component of the pressurized water reactor under high irradiation, long distance and underwater conditions, reduces the difficulty of replacement and improves the speed of replacement.

[0008] In order to achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0009] A method for underwater remote replacement of a pressurized water reactor in-core support column locking nut, comprising a method for disassembling an old locking nut and a method for installing a new locking nut;

[0010] The method for disassembling the old locking nut comprises the following steps: determining a locking nut anti-loosening structure state; if the locking nut anti-loosening structure is loose or fails, establishing a positioning base to form a working coordinate system; forming a working channel and installing a working platform base; installing a working platform to establish a working base; installing an extension platform of the working platform; installing an anti-loosening structure removal device to make the anti-loosening structure fail; installing a locking nut screwing device to disassemble a pre-disassembled locking nut;

[0011] The method for installing the new locking nut comprises the following steps: installing a measuring device to measure a pre-installation depth of a pre-installed locking nut; installing an anti-loosening cap limiting groove processing device to process an anti-loosening cap limiting groove; installing a welding tumor removal device to remove welding tumors on a lower thread of the support column; installing a screw rod cleaning device to clean impurities at the screw rod thread; installing a process nut trial installation device to check the quality of the screw rod thread; installing a screw rod thread repair device to repair the screw rod thread; installing a locking nut screwing device to install an anti-loosening cap and a pre-installed locking nut; installing a locking nut pretightening force calibration device to screw the pre-installed locking nut to a set torque; and installing an anti-loosening cap pressing device to tightly fasten the anti-loosening cap on the pre-installed locking nut.

[0012] Common locking nut anti-loosening structures are anti-loosening pins, anti-loosening caps and direct welding; through remote video inspection, it is found that the conditions requiring replacement of the locking nut are divided into two types: one is that the locking nut anti-loosening structure is loose, including anti-loosening pin displacement, anti-loosening cap deformation and partial welding point cracking; the other is that the locking nut anti-loosening structure fails, including anti-loosening pin disengagement, anti-loosening cap fracture and complete welding point cracking. In the present application, the locking nut anti-loosening structure is direct welding; through remote video inspection, it is found that the conditions requiring replacement of the locking nut are divided into two types: one is that the locking nut anti-loosening structure is loose, including partial welding point cracking; the other is that the locking nut anti-loosening structure fails, including complete welding point cracking.

[0013] In the present application, in the method for disassembling the old locking nut, the positioning base is established and the working coordinate system is formed, comprising:

[0014] The anti-breaking support plate in the basket assembly is taken as the positioning reference, the upper surface of the anti-breaking support plate is taken as the horizontal zero point, the central axis of the anti-breaking support plate is taken as the Z axis, and the 0-degree and 90-degree lines on the anti-breaking support plate are taken as the X axis and the Y axis respectively to form a three-dimensional coordinate system;

[0015] The three-dimensional coordinate value of the pre-disassembled locking nut in the three-dimensional coordinate system with the anti-breaking support plate as the positioning reference is determined.

[0016] In the present application, the method for disassembling the old locking nut comprises the following steps:

[0017] According to the position of the pre-disassembled locking nut, a horizontally outward linearly extending working channel is determined; the working channel is formed under the condition that the pre-disassembled locking nut is taken as the center and the space on both sides is sufficient to place the working platform without obstacles such as columns;

[0018] The working channel has no less than three holes on the anti-breaking support plate as positioning reference a, positioning reference b and positioning reference c;

[0019] The working platform base is remotely placed on the ground outside the working channel of the hanging basket assembly, serving as the support body of the working platform outside the hanging basket assembly.

[0020] Further, in the method for disassembling the old locking nut, the working platform is installed and the working foundation is established, comprising the following steps:

[0021] The working platform is built on the anti-breaking support plate at the working channel on the upper surface of the anti-breaking support plate, taking the positioning reference a, the positioning reference b and the positioning reference c on the anti-breaking support plate as the positioning reference; the three-dimensional coordinate values of the working platform in the three-dimensional coordinate system are determined;

[0022] The conveying platform of the working platform can move in XYZ three directions, and the conveying platform has a positioning pin shaft a and a remote locking bolt hole a, which can transport various working devices remotely locked on the conveying platform to the pre-disassembled locking nut and position them for disassembly operation;

[0023] The working platform extends horizontally to the outside of the anti-breaking support plate, and the tail of the working platform is placed on the working platform base.

[0024] Further, in the method for disassembling the old locking nut, the extension platform of the working platform is installed, comprising the following steps:

[0025] The extension platform is built at the tail end of the working platform, taking the working platform as the positioning reference, and the extension platform is placed on the working platform base at the same time;

[0026] The extension platform has a positioning pin shaft b and a remote locking bolt hole b, which can position and lock the extension part of various working devices.

[0027] Further, in the method for disassembling the old locking nut, the anti-loosening structure removal device is installed to disable the anti-loosening structure, comprising the following steps:

[0028] If the anti-loosening structure is not completely disabled, i.e. the anti-loosening structure is loose, the anti-loosening structure removal device is remotely installed on the conveying platform of the working platform;

[0029] The conveying platform sends the anti-loosening structure removal device to the pre-disassembled locking nut according to the three-dimensional coordinate values of the pre-disassembled locking nut, and removes the anti-loosening structure.

[0030] Further, in the method of disassembling the old locking nut, the locking nut screwing device is installed, and the pre-disassembled locking nut is disassembled, comprising:

[0031] The locking nut screwing device is installed on the conveying platform and the extension platform of the working platform remotely, the locking nut screwing device is operated by the manual, electric, hydraulic or pneumatic water remote screwing device, the pre-disassembled locking nut is screwed off, and the basket assembly is transported out.

[0032] Further, in the method of installing the new locking nut, the measuring device is installed, the pre-installation depth of the pre-installed locking nut is measured, comprising:

[0033] The measuring device is installed on the conveying platform of the working platform remotely, and the pre-installation depth of the pre-installed locking nut is determined by the measurement of the measuring device.

[0034] Further, in the method of installing the new locking nut, the anti-loose cap limiting groove processing device is installed, and the anti-loose cap limiting groove is processed, comprising:

[0035] The anti-loose cap limiting groove processing device is installed on the conveying platform of the working platform remotely, and more than two symmetrical anti-loose cap limiting grooves are processed outside the installation hole of the pre-installed locking nut on the bottom plate of the basket; the width and number of the anti-loose cap limiting grooves are determined according to the size of the pre-installed locking nut.

[0036] Further, in the method of installing the new locking nut, the welding bump removing device is installed, and the welding bump left when the lower thread of the supporting column is fixed with the anti-loose structure is removed, comprising:

[0037] The welding bump removing device is installed on the conveying platform of the working platform remotely, and the welding bump left when the lower thread of the supporting column is fixed with the anti-loose structure is removed; these welding bumps will affect the installation of the pre-installed locking nut.

[0038] Further, in the method of installing the new locking nut, the screw rod cleaning device is installed, and the impurities at the thread of the screw rod are cleaned, comprising:

[0039] The screw rod cleaning device is installed on the conveying platform and the extension platform of the working platform remotely, and the screw rod cleaning device is operated by the manual, electric, hydraulic or pneumatic water remote screwing device.

[0040] Further, in the method of installing the new locking nut, the process nut trial installation device is installed, and the quality of the thread of the screw rod is inspected, comprising:

[0041] The process nut trial installation device is installed on the conveying platform and the extension platform of the working platform remotely, and the process nut trial installation device is operated by the manual, electric, hydraulic or pneumatic water remote screwing device; the process nut is made of aluminum alloy or wear-resistant non-metallic material, and has the same shape as the pre-installed locking nut.

[0042] The process nut is screwed onto the lower thread of the support column using a process nut trial assembly device. The quality of the lower thread of the support column is then inspected based on the installation and removal of the process nut.

[0043] Furthermore, in the method of installing a new locking nut, a screw thread repair device is installed to repair the screw thread, including:

[0044] If the process nut gets stuck or scratched during the trial assembly, it indicates that there is a defect in the lower thread of the support column. It is necessary to remotely install a screw thread repair device on the conveyor platform of the work platform to repair the lower thread of the support column, improve the thread quality, and enhance the thread's fitability.

[0045] After repair, the lower thread of the support column was repaired by repeatedly installing the process nut until the process nut was installed smoothly.

[0046] Furthermore, the method for installing the new locking nut includes installing a locking nut tightening device, installing an anti-loosening cap, and pre-installing the locking nut, including:

[0047] The locking nut tightening device is remotely installed on the conveyor platform and extension platform of the work platform. The locking nut tightening device is operated by manual, electric, hydraulic or pneumatic water-based remote tightening device. The overall shape of the anti-loosening cap is a bottomed cylindrical shape with two or more even-numbered side protrusions on the side.

[0048] The anti-loosening cap and the pre-installed locking nut are lifted together by the conveyor platform of the work platform to the bottom of the basket; through underwater television observation, the locking nut tightening device is operated to rotate a certain angle until the side protrusion of the anti-loosening cap is aligned with the anti-loosening cap limiting groove on the bottom of the basket, at which point the anti-loosening cap is restricted from rotating.

[0049] Continue rotating the locking nut tightening device until the pre-installed locking nut can no longer be tightened. Observe the position of the pre-installed locking nut through underwater television. If it is obviously not in the pre-installed position, remove the pre-installed locking nut using the locking nut tightening device and reinstall it.

[0050] Furthermore, in the method of installing the new locking nut, the installation of the locking nut preload calibration device and the tightening of the pre-installed locking nut to the set torque include:

[0051] The locking nut preload calibration device is remotely installed on the conveyor platform and extension platform of the work platform. The locking nut preload calibration device is operated by a manual, electric, hydraulic or pneumatic waterborne remote tightening device.

[0052] The underwater part of the locking nut preload calibration device tightens the pre-installed locking nut, while the surface remote tightening device is equipped with a torque calibrator. Tests show that the torque value is halved when the pre-installed locking nut is transferred from the surface remote tightening device through a series of connecting devices to the locking nut preload calibration device. Therefore, the calibration value on the torque calibrator of the surface remote tightening device is set to twice the preload of the pre-installed locking nut. When the torque value of the torque calibrator reaches the set value, the preload of the pre-installed locking nut meets the standard.

[0053] Furthermore, in the method of installing the new locking nut, the installation of the anti-loosening cap clamping device, which secures the anti-loosening cap to the pre-installed locking nut, includes:

[0054] The anti-loosening cap clamping device is remotely installed on the conveyor platform and extension platform of the work platform. The anti-loosening cap clamping device is operated by a manual, electric, hydraulic or pneumatic remote water-based screwing device. The anti-loosening cap is squeezed by the anti-loosening cap clamping device, causing the anti-loosening cap to deform and fasten into the side groove of the pre-installed locking nut. If the anti-loosening cap is not properly clamped by underwater television inspection, the clamping is repeated multiple times until the deformed anti-loosening cap fits into the side groove of the pre-installed locking nut.

[0055] Beneficial technical effects of the present invention:

[0056] This invention discloses a method for underwater remote replacement of locking nuts on support columns of pressurized water reactor (PWR) internal components. It establishes a coordinate system for replacing locking nuts on the PWR basket assembly, encompassing all locking nuts at different coordinate values. This facilitates targeted work at specific locations and provides guidance for future replacements of locking nuts on the PWR basket assembly. The invention also proposes the concept of a working channel for replacing locking nuts on the PWR basket assembly, providing a theoretical basis for the construction of the working platform base and platform. Furthermore, it establishes the concept of a maintenance platform, providing a unified carrier for subsequent working devices, enabling remote positioning and connection of interfaces, and paving the way for future expansion with other working devices. A series of related works... The device features a unified installation interface, enabling remote positioning and connection to the work platform, paving the way for future expansion with other work devices. It includes a locking nut anti-loosening structure, a work platform, a locking nut tightening device, an underwater remote measuring device, an anti-loosening cap limiting groove machining device, an underwater remote inspection device for internal threaded holes, an underwater remote calibration preload device for locking nuts, and a remote tightening device for locking nut anti-loosening caps, providing process and equipment guarantees for future related work. It solves the problem of high-radiation, long-distance, underwater replacement of locking nuts on support columns of suspended platform components in nuclear power plant pressurized water reactors, achieving high accuracy and minimizing exposure to high-radiation environments, significantly reducing the radiation dose to operators. Attached Figure Description

[0057] Figure 1This is a schematic flowchart illustrating the process of disassembling old locking nuts according to the present invention.

[0058] Figure 2 This is a schematic diagram illustrating the process of installing the new locking nut according to the present invention;

[0059] Figure 3 This is a structural schematic diagram of the suspended platform assembly;

[0060] Figure 4 This is a schematic diagram illustrating the establishment of a three-dimensional coordinate system.

[0061] Figure 5 This is a schematic diagram of the working channel for replacing the locking nuts of the 300,000 stack support columns, taking points H6 and F8 as an example;

[0062] Figure 6 This is a schematic diagram of the work platform and surrounding equipment;

[0063] Figure 7 This is a schematic diagram of the working platform and its surrounding platform structure.

[0064] Figure 8 A schematic diagram of the anti-loosening cap structure;

[0065] Figure 9 This is a schematic diagram of the locking nut structure;

[0066] Figure 10 This is a schematic diagram showing the lock nut after installation.

[0067] In the diagram: 1: Suspended platform assembly; 2: Anti-breakage support plate; 3: Pre-disassembly locking nut; 4: Working channel; 6: Working platform base; 7: Working platform; 8: Conveying platform; 9: Anti-loosening structure; 10: Anti-loosening structure removal device; 11: Extension platform; 15: Waterborne remote tightening device; 18: Pre-installed locking nut; 20: Suspended platform bottom plate; 21: Mounting hole; 22: Anti-loosening cap limiting groove; 24: Support column; 25: Lower thread; 31: Anti-loosening cap; 32: Side boss; 36: Side groove; 40: Positioning reference a; 41: Positioning reference b; 50: Positioning pin a; 51: Remote locking bolt hole a; 52: Positioning pin b; 53: Remote locking bolt hole b. Detailed Implementation

[0068] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein in the specification of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0069] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0070] In the description of this invention, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0071] The terms “first,” “second,” “third,” etc., are used merely to distinguish elements with similar properties, not to indicate or imply relative importance or a specific order.

[0072] The terms “include,” “comprising,” or any other variation thereof are intended to cover non-exclusive inclusion, which includes not only the elements listed but also other elements not expressly listed.

[0073] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments.

[0074] This embodiment provides a method for remotely replacing the locking nut of the support column of the internal components of a pressurized water reactor underwater, including a method for remotely removing the old locking nut underwater and a method for remotely installing the new locking nut underwater.

[0075] Figure 1 This is a flowchart illustrating a method for remotely removing old lock nuts underwater. Underwater television inspection reveals that the lock nut's anti-loosening structure is loose or ineffective. The anti-loosening structure is removed according to the flowchart, and the old lock nut is then disassembled.

[0076] Figure 2 This is a flowchart illustrating the method for remotely installing a new lock nut underwater. After removing the old lock nut, follow the flowchart to install the new lock nut, including the installation, limiting, and tightening of the anti-loosening cap.

[0077] The following is a specific example of replacing the locking nut on the support column at position H6 of the 300,000 kW / s suspended platform assembly at Qinshan Nuclear Power Plant:

[0078] The specific steps for removing an old lock nut are as follows:

[0079] 1. For example Figure 3As shown, the condition of the locking nut anti-loosening structure is determined: the anti-loosening measure for the locking nut of the support column at H6 of the Qinshan Nuclear Power Plant 300,000-unit cradle assembly is to directly spot weld it to the bottom plate 20 of the cradle; there are two situations where the locking nut needs to be replaced: one is that the anti-loosening structure is loose, that is, the weld point is partially cracked; the other is that the anti-loosening structure fails, that is, the weld point is completely cracked.

[0080] 2. For example Figure 4 As shown, a positioning reference is established to form a working coordinate system: the anti-breakage support plate 2 in the suspended basket assembly 1 is used as the positioning reference, the upper surface of the anti-breakage support plate 2 is used as the horizontal zero point, the central axis of the anti-breakage support plate 2 is used as the Z-axis, and the 0-degree and 90-degree lines on the anti-breakage support plate 2 are used as the X-axis and Y-axis, respectively, to form a three-dimensional coordinate system; the three-dimensional coordinate values ​​of the pre-disassembly locking nut 3 in the three-dimensional coordinate system with the anti-breakage support plate 2 as the positioning reference are determined.

[0081] 3. For example Figure 5 As shown, a working channel 4 is formed, and a working platform base 6 is installed: the working channel 4 is determined to extend horizontally outward in a straight line according to the position of the pre-removed locking nut 3 at H6; the working platform base 6 is remotely placed on the ground of the working pool outside the working channel 4 of the suspended basket assembly 1.

[0082] 4. For example Figure 6 As shown, install the working platform 7 and establish the working foundation: at the working channel 4 on the upper surface of the anti-breakage support plate 2, lay the working platform 7 with the three holes around H6 on the anti-breakage support plate 2 as positioning points and coinciding with positioning reference a40, positioning reference b41, and positioning reference c.

[0083] The transport platform 8 of the work platform 7 can move in three directions: XYZ. The transport platform 8 has a positioning pin a50 and a remote locking bolt hole a51, which can transport various working devices remotely locked on the transport platform 8 to the pre-disassembly locking nut 3 and position them for disassembly.

[0084] The working platform 7 extends horizontally to the outside of the anti-breakage support plate 2, and the tail of the working platform 7 rests on the working platform base 6.

[0085] 5. For example Figure 7 As shown, the extension platform 11 of the installation work platform 7 is remotely installed at the tail end of the work platform 7 and on the work platform base 6, with the work platform 7 as the positioning reference. The extension platform 11 has a positioning pin b52 and a remote locking bolt hole b53, which can position and lock the extension parts of various working devices.

[0086] 6. Install the anti-loosening structure removal device 10 to disable the anti-loosening structure 9: If the anti-loosening structure 9 is not completely disabled, that is, the weld joint of the anti-loosening structure 9 is partially cracked, the anti-loosening structure removal device 10 is remotely installed on the transport platform 8 of the work platform 7; the transport platform 8 sends the anti-loosening structure removal device 10 to the pre-disassembly locking nut 3 according to the three-dimensional coordinate value of the pre-disassembly locking nut 3 at H6, removes the anti-loosening structure 9, that is, processes away all the weld joints.

[0087] 7. Install the locking nut tightening device and remove the pre-removed locking nut 3: Install the locking nut tightening device on the conveying platform 8 and extension platform 11 of the working platform 7. Operate the locking nut tightening device by manually, electrically, hydraulically or pneumatically using the water-based remote tightening device 15 to tighten and remove the pre-removed locking nut 3 and transport it out of the suspended basket assembly 1.

[0088] The specific steps for installing a new lock nut are as follows:

[0089] 1. Install a measuring device to measure the pre-installation depth of the pre-installed locking nut 18: The measuring device is remotely installed on the conveyor platform 8 of the working platform 7 to determine the installation depth of the pre-installed locking nut 18; the actual installation depth of the pre-installed locking nut 18 at H6 is measured to be 45 mm.

[0090] 2. Install the anti-loosening cap limiting groove processing device and process the anti-loosening cap limiting groove 22: Remotely install the anti-loosening cap limiting groove processing device on the conveyor platform 8 of the work platform 7, and process two symmetrical anti-loosening cap limiting grooves 22 on the outside of the mounting hole 21 of the pre-installed locking nut 18 at H6 of the bottom plate 20 of the suspended basket by means of electrical discharge machining or mechanical machining; the anti-loosening cap limiting groove 22 is square and 10 mm wide.

[0091] 3. Install a screw weld bead removal device to remove weld beads on the lower thread 25 of the support column 24: Remotely install a screw weld bead removal device on the conveyor platform 8 of the work platform 7. Remove the weld beads left when the lower thread 25 of the support column 24 at H6 is fixed to the anti-loosening structure 9 by electrical discharge machining or machining. These weld beads will affect the installation of the pre-installed locking nut 18.

[0092] 4. Install a screw cleaning device to clean impurities from the screw threads: Install a screw cleaning device on the conveying platform 8 and extension platform 11 of the working platform 7. Control the screw cleaning device to work by manually, electrically, hydraulically or pneumatically using a water-based remote screwing device 15. The screw cleaning device is fitted onto the lower thread 25 of the support column 24 at H6 and rotates rapidly to brush away impurities from the lower thread 25 of the support column 24.

[0093] 5. Install the process nut trial fitting device and inspect the quality of the screw thread; install the process nut trial fitting device on the conveying platform 8 and extension platform 11 of the working platform 7, and operate the process nut trial fitting device through the manual, electric, hydraulic or pneumatic water-based remote tightening device 15; the process nut is made of aluminum alloy and has the same shape as the pre-installed locking nut 18; tighten the process nut onto the lower thread 25 of the support column 24 at H6 through the process nut trial fitting device, and inspect the quality of the lower thread 25 of the support column 24 at H6 based on the installation and disassembly of the process nut.

[0094] 6. Install the screw thread repair device to repair the screw thread: If the process nut gets stuck or scratched during the trial assembly, it indicates that the lower thread 25 of the support column 24 at H6 is defective; the screw thread repair device needs to be installed on the conveyor platform 8 of the working platform 7, and the lower thread 25 of the support column 24 at H6 is repaired through laser cladding repair or mechanical repair processes to improve the thread quality and improve the thread's fitability; after repair, the lower thread 25 of the support column 24 at H6 is repaired by repeatedly installing the process nut until the process nut is installed smoothly.

[0095] 7. For example Figure 8 , Figure 9 , Figure 10 As shown, a locking nut tightening device is installed, along with an anti-loosening cap 31 and a pre-installed locking nut 18. The locking nut tightening device is installed on the conveyor platform 8 and extension platform 11 of the working platform 7. It is operated via a manual, electric, hydraulic, or pneumatic waterborne remote tightening device 15. The anti-loosening cap 31 is a cylindrical shape with a bottom and two side protrusions 32. The anti-loosening cap 31 and the pre-installed locking nut 18 are lifted together by the conveyor platform 8 of the working platform 7 to a position below the bottom plate 20H6 of the suspended platform. ; By observing the underwater television, the locking nut tightening device is rotated at a certain angle until the two side protrusions 32 of the anti-loosening cap 31 are aligned with the anti-loosening cap limiting groove 22 at H6 on the bottom plate 20 of the basket. At this time, the anti-loosening cap 31 is restricted from rotating. Continue to rotate the locking nut tightening device to drive the pre-installed locking nut 18 to be tightened until it can no longer be tightened. Observe the position of the pre-installed locking nut 18 through the underwater television. If it is obviously not in the pre-installed position, remove the pre-installed locking nut 18 through the locking nut tightening device and reinstall it.

[0096] 8. Install the locking nut preload calibration device and tighten the pre-installed locking nut 18 to the set torque: Install the locking nut preload calibration device on the conveying platform 8 and extension platform 11 of the working platform 7. Operate the locking nut preload calibration device through a manual, electric, hydraulic, or pneumatic waterborne remote tightening device 15; the underwater part of the locking nut preload calibration device tightens the pre-installed locking nut 18, and the waterborne remote tightening device 15 is equipped with a torque calibrator; according to the test results, the preload torque can be adjusted by the waterborne remote tightening device. The torque value of the pre-installed locking nut 18 on the locking nut preload calibration device is halved when the tightening device 15 is connected to the locking nut preload calibration device via a series of connecting devices. Therefore, the calibration value on the torque calibrator of the waterborne remote tightening device 15 is set to twice the preload of the preload of the preload of the locking nut 18. When the torque value of the torque calibrator reaches the set value, the preload of the preload of the locking nut 18 meets the standard. The preload of the preload of the locking nut 18 at H6 is 50 N·m, and it meets the standard when the torque calibrator reaches 100 N·m.

[0097] 9. Install the anti-loosening cap clamping device to fasten the anti-loosening cap 31 onto the pre-installed locking nut 18: Install the anti-loosening cap clamping device on the conveying platform 8 and extension platform 11 of the working platform 7. Operate the anti-loosening cap clamping device through the manual, electric, hydraulic or pneumatic waterborne remote tightening device 15; The head of the anti-loosening cap clamping device corresponds to the side groove 36 of the pre-installed locking nut 18; The anti-loosening cap 31 is squeezed by the anti-loosening cap clamping device, causing the new anti-loosening cap 31 to deform and fasten into the side groove 36 of the pre-installed locking nut 18; Check by underwater television. If the anti-loosening cap 31 is not tightened in place, repeat the pressing multiple times until the deformed anti-loosening cap 31 fits into the side groove 36 of the pre-installed locking nut 18.

[0098] Each step of the process is planned with divers on hand. When special confirmations or fine-tuning are required, divers can assist as needed.

[0099] Through the above specific operations, the replacement of the locking nut on the support column at H6 of the 300,000-ton stack internals has been completed. The same method can be used to inspect and replace the locking nuts on the support columns of other locations or other stack types.

[0100] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for underwater remote replacement of locking nuts on support columns of internal components of a pressurized water reactor, characterized in that, This includes methods for removing old lock nuts and methods for installing new lock nuts; The method for disassembling the old locking nut includes the following steps: determining the state of the locking nut's anti-loosening structure; if the locking nut's anti-loosening structure is loose or ineffective, establishing a positioning foundation to form a working coordinate system; determining a horizontally extending working channel (4) based on the position of the pre-disassembled locking nut (3), the working channel (4) is formed under the condition that the space on both sides is sufficient to place the working platform (7) with the pre-disassembled locking nut (3) as the center and there are no obstacles; the working channel (4) has at least three holes on the anti-breakage support plate (2) for... For positioning reference a (40), positioning reference b (41) and positioning reference c, a work platform base (6) is remotely placed on the ground of the work pool outside the work channel (4) of the suspended platform assembly (1) as a support for the work platform (7) outside the suspended platform assembly (1); the work platform (7) is installed to establish a working foundation; the extension platform (11) of the work platform (7) is installed; the anti-loosening structure removal device (10) is installed to disable the anti-loosening structure (9); the locking nut tightening device is installed and the pre-disassembly locking nut (3) is removed; The method for installing a new locking nut includes the following steps: installing a measuring device to measure the pre-installation depth of the pre-installed locking nut (18); installing a locking cap limiting groove processing device to process the locking cap limiting groove (22); installing a screw weld bead removal device to remove weld beads on the lower thread (25) of the support column (24); installing a screw cleaning device to clean impurities at the screw thread; installing a process nut trial installation device to inspect the screw thread quality; installing a screw thread repair device to repair the screw thread; installing a locking nut tightening device to install the locking cap (31) and the pre-installed locking nut (18); installing a locking nut preload calibration device to tighten the pre-installed locking nut (18) to the set torque; and installing a locking cap clamping device to fasten the locking cap (31) onto the pre-installed locking nut (18).

2. The method for underwater remote replacement of the locking nut of the internal component support column of a pressurized water reactor according to claim 1, characterized in that, The locking nut anti-loosening structure is directly welded; after remote video inspection, it was found that there are two situations in which the locking nut needs to be replaced: one is that the locking nut anti-loosening structure is loose, including cracks in the weld; the other is that the locking nut anti-loosening structure has failed, including complete cracking of the weld.

3. The method for underwater remote replacement of the locking nut of the internal component support column of a pressurized water reactor according to claim 2, characterized in that, In the method of disassembling old lock nuts, a positioning foundation is established to form a working coordinate system, including: Using the anti-breakage support plate (2) in the suspended basket assembly (1) as the positioning reference, the upper surface of the anti-breakage support plate (2) as the horizontal zero point, the central axis of the anti-breakage support plate (2) as the Z axis, and the 0-degree and 90-degree lines on the anti-breakage support plate (2) as the X axis and Y axis respectively, a three-dimensional coordinate system is formed. Determine the three-dimensional coordinates of the pre-disassembly locking nut (3) in a three-dimensional coordinate system with the anti-breakage support plate (2) as the positioning reference.

4. The method for underwater remote replacement of the locking nut of the internal component support column of a pressurized water reactor according to claim 1, characterized in that, In the method of disassembling the old lock nut, the work platform (7) is installed to establish the working foundation, including: At the working channel (4) on the upper surface of the anti-breakage support plate (2), a working platform (7) is built with positioning reference a (40), positioning reference b (41) and positioning reference c on the anti-breakage support plate (2) as positioning references; the three-dimensional coordinate values ​​of the working platform (7) in the three-dimensional coordinate system are determined; The conveying platform (8) of the work platform (7) can move in three directions: XYZ. The conveying platform (8) has a positioning pin a (50) and a remote locking bolt hole a (51), which can transport various working devices remotely locked on the conveying platform (8) to the pre-disassembly locking nut (3) and position them for disassembly. The working platform (7) extends horizontally to the outside of the anti-breakage support plate (2), and the tail of the working platform (7) rests on the working platform base (6).

5. The method for underwater remote replacement of the locking nut of the internal component support column of a pressurized water reactor according to claim 4, characterized in that, In the method of removing the old lock nut, the extension platform (11) of the installation work platform (7) includes: Using the work platform (7) as the positioning reference, an extension platform (11) is built at the tail end of the work platform (7), and the extension platform (11) is placed on the work platform base (6). The extension platform (11) has a positioning pin b (52) and a remote locking bolt hole b (53) for positioning and locking the extension parts of various working devices.

6. The method for underwater remote replacement of the locking nut of the internal component support column of a pressurized water reactor according to claim 5, characterized in that, In the method of removing the old lock nut, the anti-loosening structure removal device (10) is installed to disable the anti-loosening structure (9), including: If the anti-loosening structure (9) is not completely ineffective, the anti-loosening structure removal device (10) is remotely installed on the transport platform (8) of the work platform (7); The transport platform (8) sends the anti-loosening structure removal device (10) to the pre-loosening lock nut (3) according to the three-dimensional coordinate value of the pre-disassembly lock nut (3) to remove the anti-loosening structure (9).

7. The method for underwater remote replacement of the locking nut of the internal component support column of a pressurized water reactor according to claim 6, characterized in that, In the method of removing the old lock nut, the lock nut tightening device is installed, and the pre-removed lock nut (3) is removed, including: The locking nut tightening device is installed remotely on the conveying platform (8) and extension platform (11) of the working platform (7). The locking nut tightening device is operated by manual, electric, hydraulic or pneumatic waterborne remote tightening device (15) to tighten and remove the pre-disassembled locking nut (3) and transport the basket assembly (1).

8. The method for underwater remote replacement of the locking nut of the internal component support column of a pressurized water reactor according to claim 7, characterized in that, In the method of installing a new locking nut, a measuring device is installed to measure the pre-installation depth of the pre-installed locking nut (18), including: A measuring device is remotely installed on the conveyor platform (8) of the work platform (7) to determine the installation depth of the pre-installed locking nut (18) through the measurement of the measuring device.

9. The method for underwater remote replacement of the locking nut of the internal component support column of a pressurized water reactor according to claim 8, characterized in that, In the method of installing a new locking nut, the anti-loosening cap limiting groove machining device is used to machine the anti-loosening cap limiting groove (22), including: A remote anti-loosening cap limiting groove processing device is installed on the conveyor platform (8) of the work platform (7). Two or more even-numbered symmetrical anti-loosening cap limiting grooves (22) are processed on the outside of the mounting hole (21) of the pre-installed locking nut (18) on the bottom plate (20) of the basket. The width and number of anti-loosening cap limiting grooves (22) are determined according to the size of the pre-installed locking nut (18).

10. The method for underwater remote replacement of the locking nut of the internal component support column of a pressurized water reactor according to claim 9, characterized in that, In the method of installing the new locking nut, a device for removing weld beads from the screw is installed to remove weld beads from the lower thread (25) of the support column (24), including: A device for removing weld beads from screws is installed remotely on the conveyor platform (8) of the work platform (7) to remove weld beads left when the lower thread (25) of the support column (24) is fixed to the anti-loosening structure (9).

11. The method for underwater remote replacement of the locking nut of the internal component support column of a pressurized water reactor according to claim 10, characterized in that, In the method of installing a new locking nut, a screw cleaning device is installed to clean impurities from the screw threads, including: The screw cleaning device is remotely installed on the conveyor platform (8) and extension platform (11) of the working platform (7), and the screw cleaning device is operated by a manual, electric, hydraulic or pneumatic waterborne remote screwing device (15).

12. The method for underwater remote replacement of the locking nut of the internal component support column of a pressurized water reactor according to claim 11, characterized in that, In the method of installing a new locking nut, the installation process includes a nut trial fitting device to inspect the quality of the screw thread, including: The process nut trial installation device is installed remotely on the conveying platform (8) and extension platform (11) of the work platform (7). The process nut trial installation device is operated by a manual, electric, hydraulic or pneumatic water-based remote screwing device (15). The process nut is made of aluminum alloy or wear-resistant non-metallic material and has the same shape as the pre-installed locking nut (18). The process nut is screwed onto the lower thread (25) of the support column (24) using the process nut trial assembly device. The quality of the lower thread (25) of the support column (24) is checked based on the installation and disassembly of the process nut.

13. The method for underwater remote replacement of the locking nut of the internal component support column of a pressurized water reactor according to claim 12, characterized in that, The method for installing a new locking nut includes installing a screw thread repair device to repair the screw thread, including: If the process nut gets stuck or scratched during the trial assembly, a screw thread repair device needs to be installed remotely on the conveyor platform (8) of the work platform (7) to repair the lower thread (25) of the support column (24); After repair, the lower thread (25) of the support column (24) is repaired by repeatedly installing the process nut until the process nut is installed smoothly.

14. The method for underwater remote replacement of the locking nut of the internal component support column of a pressurized water reactor according to claim 13, characterized in that, The method for installing a new locking nut includes installing a locking nut tightening device, installing an anti-loosening cap (31), and pre-installing a locking nut (18), comprising: The locking nut tightening device is installed remotely on the conveying platform (8) and extension platform (11) of the working platform (7). The locking nut tightening device is operated by a manual, electric, hydraulic or pneumatic water-based remote tightening device (15). The anti-loosening cap (31) is cylindrical with a bottom and has two or more even-numbered side protrusions (32) on the side. The anti-loosening cap (31) and the pre-installed locking nut (18) are lifted together by the conveying platform (8) of the working platform (7) to the bottom plate (20) of the basket. Through the observation of the underwater television, the locking nut tightening device is operated to rotate a certain angle until the side protrusion (32) of the anti-loosening cap (31) is aligned with the anti-loosening cap limiting groove (22) on the bottom plate (20) of the basket. At this time, the anti-loosening cap (31) is restricted from rotating. Continue rotating the locking nut tightening device to tighten the pre-installed locking nut (18) until it cannot be tightened further. Observe the position of the pre-installed locking nut (18) through the underwater television. If it is obviously not in the pre-installed position, remove the pre-installed locking nut (18) through the locking nut tightening device and reinstall it.

15. The method for underwater remote replacement of the locking nut of the internal component support column of a pressurized water reactor according to claim 14, characterized in that, In the method of installing a new locking nut, the locking nut preload calibration device is installed, and the pre-installed locking nut (18) is tightened to the set torque, including: The locking nut preload calibration device is installed remotely on the conveying platform (8) and extension platform (11) of the working platform (7). The locking nut preload calibration device is operated by a manual, electric, hydraulic or pneumatic waterborne remote tightening device (15). The underwater part of the locking nut preload calibration device screws the pre-installed locking nut (18), and the above-water remote screwing device (15) is equipped with a torque calibrator; the calibration value on the torque calibrator of the above-water remote screwing device (15) is set to twice the preload of the pre-installed locking nut (18); when the torque value of the torque calibrator reaches the set value, the preload of the pre-installed locking nut (18) meets the standard.

16. The method for underwater remote replacement of the locking nut of the internal component support column of a pressurized water reactor according to claim 15, characterized in that, In the method of installing a new locking nut, the anti-loosening cap clamping device is installed so that the anti-loosening cap (31) is fastened to the pre-installed locking nut (18), including: The anti-loosening cap clamping device is remotely installed on the conveying platform (8) and extension platform (11) of the working platform (7). The anti-loosening cap clamping device is operated by a manual, electric, hydraulic or pneumatic waterborne remote screwing device (15). The anti-loosening cap (31) is squeezed by the anti-loosening cap clamping device, so that the anti-loosening cap (31) is deformed and fastened in the side groove (36) of the pre-installed locking nut (18). If the anti-loosening cap (31) is not clamped in place by underwater television inspection, the pressing is repeated multiple times until the deformed anti-loosening cap (31) fits into the side groove (36) of the pre-installed locking nut (18).

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