A device and method for replacing a pressurized water reactor in-core instrument regulator nut

Abstract

The present application belongs to the field of underwater special maintenance of nuclear power plant, and particularly relates to a device and method for replacing and maintaining a regulating nut of a pressurized water reactor in-pile component, which comprises: a conveying and positioning platform, used for positioning and fixing an execution component, conveying the execution component to a working position, conveying the regulating nut and sleeve to the in-pile component; the execution component, used for removing the regulating nut and sleeve, cleaning and repairing the thread, and installing a new integrated sleeve; a remote gripper, used for clamping the sleeve and sending the sleeve out to the conveying and positioning platform; and an underwater camera, used for observing the whole process to ensure that all operation procedures are correct and all parts are installed in place. The present application can utilize a narrow maintenance channel to realize remote underwater removal of the regulating nut, cleaning of the thread hole, inspection and measurement of the thread state, installation of the new integrated sleeve, detection of the nut installation torque and depth, and the like.

Description

Technical Field

[0001] This invention belongs to the field of underwater special maintenance of nuclear power plants, specifically relating to a device and method for replacing and maintaining the adjusting nuts of internal components of a pressurized water reactor. Background Technology

[0002] Nuclear reactor internals refer to all components within the reactor pressure vessel except for fuel assemblies and related parts, core measuring instruments, and pressure vessel material irradiation monitoring tubes. They are critical components of the nuclear island and are important parts of the reactor, divided into upper internals and lower internals. Adjusting nuts are installed inside the basket base plate of the lower internals and primarily serve to support the sleeves and adjust the preload of the flow distribution plate.

[0003] Because reactor internals operate within the pressure vessel for extended periods, their operating conditions are affected by factors such as thermal loads, mechanical loads, vibration loads, and neutron irradiation. These factors inevitably have a time-dependent effect, causing parts such as adjusting nuts to loosen and fail. The failure of a single part can also compromise the integrity of the entire reactor internals, thereby weakening or eliminating their functionality before the end of the nuclear power plant's lifespan, posing a significant risk to the safe operation of the nuclear power plant.

[0004] There are 40 adjusting nuts in the lower reactor internals, distributed in different positions within the bottom plate of the basket. Maintenance can only be performed from the bottom upwards, and the bottom is blocked by a breakage-prevention support plate, surrounded by support columns. The space is extremely limited, far from the outer edge of the lower reactor internals, making replacement and maintenance very difficult.

[0005] Currently, there is no solution for replacing the adjusting nut individually. Furthermore, overall maintenance of the lower in-core components requires rotating the entire in-core assembly 180 degrees and then completely disassembling, replacing, and reinstalling all relevant parts. This approach is time-consuming, expensive, and involves high levels of radiation, which could harm maintenance personnel. Therefore, it is not suitable for repairing individual adjusting nuts.

[0006] Alternatively, underwater repairs by divers can be used, but this method carries significant safety risks, and divers cannot access certain confined spaces, thus failing to completely solve the repair problem. Summary of the Invention

[0007] The purpose of this invention is to provide a device and method for replacing and maintaining the adjusting nut of the internal components of a pressurized water reactor. It can utilize a narrow maintenance passage, a conveying and positioning platform, an actuator, and a remote gripper to achieve remote underwater removal of the adjusting nut, cleaning of the threaded hole, inspection and measurement of the thread condition, installation of a new integrated sleeve, and detection of the nut installation torque and depth.

[0008] Technical solution to achieve the purpose of this invention: In a first aspect, the present invention provides a device for replacing and maintaining the adjusting nuts of internal components of a pressurized water reactor, comprising: The conveying and positioning platform is used to position and fix the actuators, and to transport the actuators to the working position, and to transport the adjusting nuts and sleeves to the outside of the stack components; The actuator is used to remove adjusting nuts and sleeves, clean and repair threads, and install new integrated sleeves; Remote grippers are used to grip the sleeve and deliver it to the conveying and positioning platform; Underwater cameras are used to observe the entire work process, ensuring that all procedures are performed correctly and all parts are installed in place.

[0009] Furthermore, the execution component includes: Adjusting nut tightening tool, used for tightening adjusting nuts; a new type of one-piece sleeve part; Nut cutter, used to cut off adjusting nuts; Thread cleaning and repair tools are used for cleaning, rinsing, and repairing threads; Thread inspection and measurement tools are used to inspect and measure cleaned, flushed, and repaired threads to determine whether the thread accuracy is up to standard. Sleeve installation tool for installing new integrated sleeves; Remote measuring tools are used to detect and confirm the installation height of the new integrated sleeve, ensuring that the new integrated sleeve is installed in place.

[0010] Furthermore, the conveying and positioning platform includes: a positioning component, a platform base, a working position gripper, a transport component, and a three-way motion mechanism; the positioning component is located at the bottom of the platform base and is used to position and fix it with the anti-breakage support plate on the maintenance channel to ensure that the conveying and positioning platform will not loosen or shift during use; the three-way motion mechanism is an X, Y, and Z three-way motion mechanism, which is used to control the movement of the transport component on the platform base along the X, Y, and Z directions, transporting each actuator installed on the transport component from the outside of the stacked components to the working position and accurately positioning it; the working position gripper is installed at the head of the platform base and is used to clamp the parts that need to be installed and transported to the working position by the conveying and positioning platform.

[0011] Furthermore, the adjusting nut tightening tool includes: a remote connecting rod, a transmission mechanism, and a tightening head, which are connected in sequence. The remote connecting rod transmits power to the tightening head through the transmission mechanism.

[0012] Secondly, the present invention provides a method for replacing and maintaining the adjusting nuts of internal components of a pressurized water reactor, comprising: Step 1: Model the repair site to obtain a 3D model of the repair site; Step 2: Based on the 3D model and the location of the adjusting nut that needs repair, determine the repair channel, clamping channel, and observation channel; Step 3: Install the underwater camera in the observation channel; Step 4: Install the conveyor positioning platform onto the maintenance channel; Step 5: Install the adjusting nut tightening tool onto the conveyor positioning platform and remove the adjusting nut that needs to be replaced; Step 6: Remove the sleeve that needs to be replaced; Step 7: Clean and repair the threads on the lower core plate; Step 8: Install the new integrated sleeve, tighten the new integrated sleeve parts, and ensure that the new integrated sleeve is installed in place.

[0013] Furthermore, in step 2, the maintenance channel is used as the entry and exit channel for installing the delivery and positioning platform and all the execution components, the gripping channel is used for installing remote grippers and performing remote gripper operations, and the observation channel is used for installing underwater cameras.

[0014] Further, step 5 includes: placing the adjusting nut tightening tool on the transport component of the conveying and positioning platform, positioning and fixing the adjusting nut tightening tool, transporting the adjusting nut tightening tool to the working position through the three-way motion mechanism of the conveying and positioning platform, and tightening the adjusting nut that needs to be replaced using the adjusting nut tightening tool; if the adjusting nut can be unscrewed, removing the adjusting nut using the adjusting nut tightening tool, and then transporting the removed adjusting nut out of the in-core components through the conveying and positioning platform; if the adjusting nut cannot be unscrewed, replacing the adjusting nut tightening tool with a nut cutting tool, positioning and fixing the nut cutting tool on the conveying and positioning platform, cutting the adjusting nut from inside the lower core plate using the nut cutting tool, and then transporting the removed adjusting nut out of the in-core components through the conveying and positioning platform.

[0015] Furthermore, step 6 includes: if the sleeve slides out and falls normally, the sleeve is placed on the conveying and positioning platform, and the sleeve is transported to the outside of the in-stack components through the conveying and positioning platform; if the sleeve cannot slide out normally, the sleeve is gripped by a remote gripper through the gripping channel and sent to the conveying and positioning platform, and then the sleeve is transported to the outside of the in-stack components through the conveying and positioning platform.

[0016] Further, step 7 includes: placing the thread cleaning and repair tool on the transport component of the conveying and positioning platform, positioning and fixing the thread cleaning and repair tool, and transporting the thread cleaning and repair tool to the working position through the three-way motion mechanism of the conveying and positioning platform; using the thread cleaning and repair tool to clean, rinse and repair the threads; placing the thread inspection and measurement tool on the transport component of the conveying and positioning platform, positioning and fixing the thread inspection and measurement tool, and transporting the thread inspection and measurement tool to the working position through the three-way motion mechanism of the conveying and positioning platform; using the thread inspection and measurement tool to inspect and measure the cleaned, rinsed and repaired threads; if the thread accuracy is qualified, proceed to the next step; if the thread accuracy is unqualified, replace it with the thread cleaning and repair tool, and clean and repair the threads again until the thread accuracy is qualified.

[0017] Further, step 8 includes: placing the new integrated sleeve to be installed onto the sleeve installation tool; placing the sleeve installation tool and the new integrated sleeve onto the transport component; transporting the sleeve installation tool to the working position via the three-way motion mechanism of the conveying and positioning platform; installing the new integrated sleeve into place in a relay manner through the Z-axis movement of the three-way motion mechanism of the conveying and positioning platform and the cooperation of the working position grippers; clamping and fixing the new integrated sleeve with the working position grippers; removing the sleeve installation tool; placing the adjusting nut tightening tool onto the transport component of the conveying and positioning platform, and... The adjusting nut tightening tool is positioned and fixed, and then transported to the working position by the three-way motion mechanism of the conveying and positioning platform. The working position grippers are released, and the adjusting nut tightening tool is used to tighten the parts of the new integrated sleeve. The remote measuring tool is placed on the transport component of the conveying and positioning platform, and positioned and fixed. The remote measuring tool is then transported to the working position by the three-way motion mechanism of the conveying and positioning platform. Through remote measurement, it is confirmed that the installation height of the new integrated sleeve is consistent with the theoretical value, ensuring that the new integrated sleeve is installed in place.

[0018] The beneficial technical effects of this invention are as follows: 1. The present invention provides a device for replacing and repairing adjusting nuts of internal components of pressurized water reactors. In the narrow underwater maintenance channel, a conveying and positioning platform is set up. Through the conveying and positioning platform, the execution component and the remote gripper, the adjusting nut that needs to be repaired is connected to the operator, realizing remote maintenance of the adjusting nut. This solves the difficulties in the maintenance process such as limited space, complex underwater maintenance process, difficulty in long-distance operation and large radiation dose.

[0019] 2. The method for replacing and repairing the adjusting nut of the internal components of a pressurized water reactor provided by this invention is a separate point-to-point repair, which has a small workload, short cycle and low cost.

[0020] 3. The method for replacing and repairing the adjusting nuts of the internal components of a pressurized water reactor provided by this invention has been practically verified in the overhaul of Qinshan Nuclear Power Plant. It has solved the maintenance work of the adjusting nuts of the lower internal components, shortened the overhaul cycle, and played a good demonstration role. It can be widely applied to the replacement and maintenance of bolts, nuts and other parts under similar working conditions. Attached Figure Description

[0021] Figure 1 A flowchart of a method for replacing and maintaining the adjusting nut of an internal component of a pressurized water reactor provided by the present invention; Figure 2 This is a schematic diagram of the installation of the conveying and positioning platform in a pressurized water reactor internal component adjustment nut replacement and maintenance device provided by the present invention; Figure 3 A schematic diagram of the working state of a pressurized water reactor internal component adjustment nut replacement and maintenance device provided by the present invention; Figure 4 This is a schematic diagram of the conveying and positioning platform structure in a pressurized water reactor internal component adjustment nut replacement and maintenance device provided by the present invention; Figure 5 This is a schematic diagram of the adjusting nut tightening tool in a pressurized water reactor internal component adjusting nut replacement and maintenance device provided by the present invention; Figure 6 The present invention provides a remote gripper in a pressurized water reactor internal component adjustment nut replacement and maintenance device. Figure 7 This invention provides a tool for cleaning and repairing threads in a pressurized water reactor internal component adjustment nut replacement and maintenance device; Figure 8 This invention provides a remote measuring tool for replacing and maintaining the adjusting nut of an internal component of a pressurized water reactor. Figure 9 This is a schematic diagram of the installation of a novel integrated sleeve in a pressurized water reactor internal component adjustment nut replacement and maintenance device provided by the present invention. Detailed Implementation

[0022] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0023] This invention provides a device for replacing and maintaining the adjusting nuts of internal components of a pressurized water reactor, including a conveying and positioning platform 7, an execution component, a remote gripper, and an underwater camera.

[0024] The conveying and positioning platform 7 is used to position and fix the actuator, and to transport the actuator to the working position, and to transport the adjusting nut 5 and the sleeve 6 to the outside of the stack components; The actuator is used to remove the adjusting nut 5 and the sleeve 6, clean and repair the threads, and install the new integrated sleeve 17; The remote gripper is used to grip the sleeve 6 and send the sleeve 6 to the conveying and positioning platform 7; Underwater cameras are used to observe the entire work process, ensuring that all procedures are performed correctly and all parts are installed in place.

[0025] The actuators include: adjusting nut tightening tool, nut cutting tool, thread cleaning and repair tool, thread inspection and measuring tool, sleeve installation tool 16, and remote measuring tool.

[0026] Adjusting nut tightening tool is used to tighten adjusting nuts 5 and new integrated sleeve 17. The nut cutter is used to cut off the adjusting nut 5; Thread cleaning and repair tools are used to clean, rinse, and repair threads; Thread inspection and measuring tools are used to inspect and measure cleaned, flushed, and repaired threads to determine whether the thread accuracy is up to standard. Sleeve installation tool 16 is used to install the new integrated sleeve 17; Remote measuring tools are used to detect and confirm the installation height of the new integrated sleeve 17, ensuring that the new integrated sleeve 17 is installed in place.

[0027] In one specific embodiment, the delivery positioning platform 7, such as Figure 4 As shown, it includes: a positioning component 9, a platform base 10, a working gripper 11, a transport component 12, and a three-way motion mechanism; the positioning component 9 is located at the bottom of the platform base 10 and is used to position and fix it with the anti-breakage support plate 4 on the maintenance passage to ensure that the transport positioning platform 7 will not loosen or shift during use; the three-way motion mechanism is an X, Y, and Z three-way motion mechanism, which is used to control the movement of the transport component 12 on the platform base 10 in the X, Y, and Z directions, transporting each actuator installed on the transport component 12 from the outside of the stacked components to the working position and accurately positioning it, such as... Figure 3 As shown; the working position gripper 11 is installed on the head of the platform base 10 and is used to grip the parts that need to be installed, which are transported to the working position by the conveying positioning platform 7.

[0028] In one specific embodiment, the adjusting nut tightening tool, such as Figure 5 As shown, it includes: a remote connecting rod 13, a transmission mechanism 14, and a screwing head 15. The remote connecting rod 13, the transmission mechanism 14, and the screwing head 15 are connected in sequence. The remote connecting rod 13 transmits power to the screwing head 15 through the transmission mechanism 14.

[0029] In one specific embodiment, the remote gripper, such as Figure 6 As shown. In one specific embodiment, the thread cleaning and repair tool, such as Figure 7As shown, it includes: a first base, a first commutator, and a working head; the working head comes in different types (various brush heads, water spray cleaning heads, repair heads, etc.) and is used for cleaning, rinsing and repairing threads, and can be replaced according to different functions.

[0030] Thread inspection and measurement tools include: a second base, a second commutator, and thread gauges. Thread gauges are made of non-metallic material and will not damage the threads during measurement. If there are burrs or deformation inside the screw, they will leave marks on the thread gauge during measurement.

[0031] In one specific implementation, a remote measurement tool such as Figure 8 As shown.

[0032] This invention also provides a method for replacing and maintaining the adjusting nuts of internal components in a pressurized water reactor, such as... Figure 1 As shown, the specific steps include: Step 1: Model the repair site to obtain a 3D model of the repair site. During overhauls, the in-core components are placed at the bottom of the water tank, and these components have a high radiation dose, making on-site measurement and simulation impossible. Preliminary work on the adjusting nut requires precise modeling of the on-site working environment to support subsequent work and ensure smooth replacement and repair. The modeling includes structures such as in-core component 1, water tank 2, and tooling components within the water tank 3, etc. Figure 2 As shown.

[0033] Step 2: Based on the 3D model and the location of the adjusting nut 5 that needs repair, determine the repair channel, clamping channel, and observation channel. Based on the 3D model and the location of the adjusting nut 5 requiring maintenance, the maintenance channel, gripping channel, and observation channel are determined. The maintenance channel is used for the installation and access of the conveyor positioning platform 7 and all actuators; the gripping channel is used for installing remote grippers and performing remote gripping operations; and the observation channel is used for installing underwater cameras.

[0034] The actuators include: adjusting nut tightening tool, nut cutting tool, thread cleaning and repair tool, thread inspection and measuring tool, sleeve installation tool 16, and remote measuring tool.

[0035] Step 3: Install the underwater camera in the observation channel. The underwater camera is fixedly installed in the observation channel, and all work is observed through the underwater camera to ensure that all procedures are performed correctly and all parts are installed in place.

[0036] Step 4: Install the conveyor positioning platform 7 onto the anti-breakage support plate 4 of the maintenance passage. Using a remote installation tool, the conveying and positioning platform 7 is installed along the maintenance channel to the designated position on the anti-breakage support plate 4. Positioning parts 9 at the bottom of the conveying and positioning platform are used to position and mechanically fix it to the anti-breakage support plate 4, ensuring that the conveying and positioning platform 7 will not loosen or shift during use. Through the control of a three-way motion mechanism, the transport component 12 moves on the platform base 10, transporting each actuator installed on the conveying component 12 from the outside of the stacked components to the working position and ensuring precise positioning. After the installation tool transports the part to be installed to the working position via the conveying and positioning platform 7, the working position gripper 11 clamps and fixes it, facilitating tool replacement during subsequent operations.

[0037] Step 5: Install the adjusting nut tightening tool onto the conveying and positioning platform 7, transport it to the working position, and remove the adjusting nut 5 that needs to be replaced. Using a remote hoisting tool, the adjusting nut tightening tool is placed on the transport component 12 of the conveying and positioning platform 7, and the tool is positioned and fixed. Then, the three-way motion mechanism of the conveying and positioning platform is operated to transport the adjusting nut tightening tool to the working position. By operating the remote connecting rod 13, power is transmitted to the tightening head 15 through the transmission mechanism 14, and the adjusting nut 5 that needs to be replaced is slowly tightened.

[0038] If the adjusting nut 5 can be unscrewed and falls onto the screwdriver 15, continue operating the transport and positioning platform 7 to move the adjusting nut screwdriver and the removed adjusting nut to the outside of the lower reactor core assembly. Because the adjusting nut 5 operates within the reactor for extended periods, it may become deformed or jammed and cannot be unscrewed. If the adjusting nut 5 cannot be unscrewed, the adjusting nut screwdriver must be replaced with a nut cutter. The adjusting nut is then cut from the lower core plate 8 using the nut cutter. Continue operating the transport and positioning platform 7 to move the nut cutter and the removed adjusting nut to the outside of the lower reactor core assembly. The nut cutting method is generally EDM or mechanical, ensuring the adjusting nut can be removed smoothly.

[0039] Step 6: Remove the sleeve 6 that needs to be replaced, and transport the sleeve 6 to the outside of the stack components via the conveying and positioning platform 7. After the adjusting nut 5 is removed, the inner sleeve 6 will slowly slide out under normal circumstances, and the sleeve 6 will fall into the transport basket on the transport component 12. The sleeve 6 can then be transported to the outside of the stacked components by the conveying and positioning platform 7. If the sleeve 6 becomes deformed and jammed, preventing it from sliding out and falling normally, a remote gripper is required. When using it, extend the remote gripper into the lower core component from the gripping channel, grip the inner sleeve 6, and gradually pull the sleeve 6 down out of the lower core plate 8. Then, place the sleeve 6 into the transport basket on the transport component 12 of the conveying and positioning platform and transport it outside the core component.

[0040] Step 7: Clean and repair the threads on the lower core plate 8. Using a remote hoisting tool, the thread cleaning and repair tool is placed onto the transport component 12 of the conveying and positioning platform 7, and then positioned and secured. During use, the three-way motion mechanism of the conveying and positioning platform transports the thread cleaning and repair tool to the working position. The thread cleaning and repair tool is used to clean, rinse, and repair the threads, ensuring there are no obvious impurities inside the threads. Using a remote hoisting tool, the thread inspection and measurement tool is placed onto the transport component 12 of the conveying and positioning platform 7, and then positioned and secured. The three-way motion mechanism of the conveying and positioning platform 7 transports the thread inspection and measurement tool to the working position. The thread gauge is made of non-metallic material and will not damage the threads during measurement. If there are burrs or deformation inside the screw, marks will be left on the thread gauge during measurement. The thread inspection and measurement tool is used to measure the thread. If the measurement shows the thread is normal, proceed to the next step. If the measured thread is deformed or has burrs, the thread cleaning and repair tool is used, and the thread is repaired until the thread accuracy is qualified.

[0041] Step 8: Install the new integrated sleeve 17. Tighten the new integrated sleeve 17 parts using the adjusting nut tightening tool to ensure that the new integrated sleeve 17 is installed in place. The new integrated sleeve 17 to be installed is placed on the sleeve installation tool 16. Using a remote hoisting tool, the sleeve installation tool 16 and the new integrated sleeve 17 are placed on the transport component 12. The three-way motion mechanism of the transport and positioning platform 7 is then operated to transport the sleeve installation tool 16 to the working position. The installation components of the new integrated sleeve 17 include multiple positioning rods of varying heights. Because the new integrated sleeve 17 is relatively long, it cannot be installed in one go. The Z-axis movement of the three-way motion mechanism of the conveying and positioning platform 7 and the working position gripper 11 work together to install the new integrated sleeve 17 in a relay manner. Specifically, after the Z-axis lifts the transport component 12 to a certain height h1, the working position gripper 11 clamps the new integrated sleeve 17. The Z-axis then retracts to its lowest position, and the positioning rod at height h2 is placed on the transport component 12 to position and fix it. The working position gripper 11 then releases, and the Z-axis, through the positioning rod at height h2, lifts the new integrated sleeve 17 to a height of h1 + h2. This relay motion, using the sleeve installation tool 16, completes the installation of the new integrated sleeve 17 into place. Figure 9 As shown. After installation, the working position gripper 11 clamps and fixes the new integrated sleeve 17, and the sleeve installation tool 16 is removed.

[0042] Using a remote hoisting tool, the adjusting nut tightening tool is placed on the transport component 12 of the conveying and positioning platform, and the tool is positioned and fixed. The three-way motion mechanism of the conveying and positioning platform is then used to transport the adjusting nut tightening tool to the working position. At this point, the working position gripper 11 is released, and the adjusting nut tightening tool is used to tighten the parts of the new integrated sleeve 17. The tightening torque reaches the value required in the simulation experiment, ensuring that the parts of the new integrated sleeve 17 are installed in place, thus completing the installation of the new integrated sleeve 17.

[0043] Using a remote hoisting tool, the remote measuring tool is placed onto the transport component 12 of the conveying and positioning platform, and the remote measuring tool is positioned and secured. The three-way motion mechanism of the conveying and positioning platform is then operated to transport the remote measuring tool to the working position. Remote measurement confirms that the installation height of the new integrated sleeve 17 matches the theoretical value, ensuring that the new integrated sleeve 17 is installed correctly.

[0044] After completing all installation tasks, remove all tools.

[0045] The present invention has been described in detail above with reference to the accompanying drawings and embodiments. However, the present invention is not limited to the above embodiments, and various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention. All contents not described in detail in the present invention can be derived from existing technologies.

Claims

1. A device for replacing and maintaining adjusting nuts on internal components of a pressurized water reactor, characterized in that, include: The conveying and positioning platform (7) is used to position and fix the actuator, and to transport the actuator to the working position, and to transport the adjusting nut (5) and sleeve (6) to the outside of the stack components; The actuator is used to remove the adjusting nut (5) and sleeve (6), clean and repair the threads, and install the new integrated sleeve (17). Remote grippers are used to grip the sleeve (6) and send the sleeve (6) to the conveying and positioning platform (7); Underwater cameras are used to observe the entire work process, ensuring that all procedures are performed correctly and all parts are installed in place.

2. The device for replacing and maintaining the adjusting nut of the internal components of a pressurized water reactor according to claim 1, characterized in that, The execution component includes: Adjusting nut tightening tool, used for tightening adjusting nuts (5) and new integrated sleeve (17); Nut cutting tool for cutting off adjusting nuts (5); Thread cleaning and repair tools are used for cleaning, rinsing, and repairing threads; Thread inspection and measurement tools are used to inspect and measure cleaned, flushed, and repaired threads to determine whether the thread accuracy is up to standard. Sleeve installation tool (16) for installing the new integrated sleeve (17); Remote measuring tools are used to detect and confirm the installation height of the new integrated sleeve (17) to ensure that the new integrated sleeve (17) is installed in place.

3. The device for replacing and maintaining the adjusting nut of the internal components of a pressurized water reactor according to claim 1, characterized in that, The conveying and positioning platform (7) includes: positioning parts (9), platform base (10), working position grippers (11), transport components (12), and a three-way motion mechanism; the positioning parts (9) are located at the bottom of the platform base (10) and are used to position and fix with the anti-breakage support plate (4) on the maintenance channel to ensure that the conveying and positioning platform (7) will not loosen or shift during use; the three-way motion mechanism is an X, Y, Z three-way motion mechanism, which is used to control the movement of the transport components (12) on the platform base (10) along the X, Y, and Z directions, and to transport each execution component installed on the transport components (12) from the outside of the stacked components to the working position and to accurately position it; the working position grippers (11) are installed at the head of the platform base (10) and are used to clamp the parts that need to be installed and transported to the working position by the conveying and positioning platform (7).

4. A device for replacing and maintaining adjusting nuts of internal components in a pressurized water reactor according to claim 2, characterized in that, The adjusting nut tightening tool includes: a remote connecting rod (13), a transmission mechanism (14), and a tightening head (15). The remote connecting rod (13), the transmission mechanism (14), and the tightening head (15) are connected in sequence. The remote connecting rod (13) transmits power to the tightening head (15) through the transmission mechanism (14).

5. A method for replacing and maintaining the adjusting nut of an internal component of a pressurized water reactor, using the device described in any one of claims 1-4, characterized in that... include: Step 1: Model the repair site to obtain a 3D model of the repair site; Step 2: Based on the 3D model and the location of the adjusting nut (5) that needs repair, determine the repair channel, clamping channel and observation channel; Step 3: Install the underwater camera in the observation channel; Step 4: Install the conveyor positioning platform (7) onto the maintenance channel; Step 5: Install the adjusting nut tightening tool onto the conveying positioning platform (7) and remove the adjusting nut (5) that needs to be replaced. Step 6: Remove the sleeve that needs to be replaced (6); Step 7: Clean and repair the threads on the lower core plate (8); Step 8: Install the new integrated sleeve (17), tighten the new integrated sleeve (17) parts, and ensure that the new integrated sleeve (17) is installed in place.

6. A method for replacing and maintaining the adjusting nut of an internal component of a pressurized water reactor according to claim 5, characterized in that, In step 2, the maintenance channel is used to install the conveying and positioning platform (7) and the entry and exit channels of all the execution components, the gripping channel is used to install the remote gripper and carry out the remote gripper operation, and the observation channel is used to install the underwater camera.

7. A method for replacing and maintaining the adjusting nut of an internal component of a pressurized water reactor according to claim 5, characterized in that, Step 5 includes: placing the adjusting nut tightening tool on the transport component (12) of the transport positioning platform (7), positioning and fixing the adjusting nut tightening tool, transporting the adjusting nut tightening tool to the working position through the three-way motion mechanism of the transport positioning platform (7), and tightening the adjusting nut (5) that needs to be replaced through the adjusting nut tightening tool; if the adjusting nut (5) can be unscrewed, removing the adjusting nut (5) through the adjusting nut tightening tool, and then transporting the removed adjusting nut (5) out of the stack internal components (1) through the transport positioning platform (7); if the adjusting nut (5) cannot be unscrewed, replacing the adjusting nut tightening tool with a nut cutting tool, positioning and fixing the nut cutting tool on the transport positioning platform (7), cutting the adjusting nut from the lower core plate (8) through the nut cutting tool, and then transporting the removed adjusting nut (5) out of the stack internal components (1) through the transport positioning platform (7).

8. A method for replacing and maintaining the adjusting nut of an internal component of a pressurized water reactor according to claim 5, characterized in that, Step 6 includes: if the sleeve (6) slides out and falls normally, the sleeve (6) is placed on the conveying and positioning platform (7), and the sleeve (6) is transported to the outside of the stack components through the conveying and positioning platform (7); if the sleeve (6) cannot slide out normally, the sleeve (6) is gripped by a remote gripper through the gripping channel and sent to the conveying and positioning platform (7), and then the sleeve (6) is transported to the outside of the stack components through the conveying and positioning platform (7).

9. A method for replacing and maintaining the adjusting nut of an internal component of a pressurized water reactor according to claim 5, characterized in that, Step 7 includes: placing the thread cleaning and repair tool on the transport component (12) of the transport positioning platform (7), positioning and fixing the thread cleaning and repair tool, and transporting the thread cleaning and repair tool to the working position through the three-way motion mechanism of the transport positioning platform (7), and using the thread cleaning and repair tool to clean, rinse and repair the threads; placing the thread inspection and measurement tool on the transport component (12) of the transport positioning platform (7), positioning and fixing the thread inspection and measurement tool, and transporting the thread inspection and measurement tool to the working position through the three-way motion mechanism of the transport positioning platform (7), and using the thread inspection and measurement tool to inspect and measure the cleaned, rinsed and repaired threads; if the thread accuracy is qualified, proceed to the next step; if the thread accuracy is unqualified, replace it with the thread cleaning and repair tool, and clean and repair the threads again until the thread accuracy is qualified.

10. A method for replacing and maintaining the adjusting nut of an internal component of a pressurized water reactor according to claim 5, characterized in that, Step 8 includes: placing the new integrated sleeve (17) to be installed onto the sleeve installation tool (16); placing the sleeve installation tool (16) and the new integrated sleeve (17) onto the transport component (12); transporting the sleeve installation tool (16) to the working position via the three-way motion mechanism of the transport positioning platform (7); installing the new integrated sleeve (17) into place in a relay manner through the Z-axis movement of the three-way motion mechanism of the transport positioning platform (7) and the cooperation of the working position gripper (11); clamping and fixing the new integrated sleeve (17) via the working position gripper (11); and removing the sleeve installation tool (16); placing the adjusting nut tightening tool onto the transport positioning platform. The adjusting nut tightening tool is positioned and fixed on the transport component (12) of the platform. The adjusting nut tightening tool is transported to the working position through the three-way motion mechanism of the transport positioning platform. The working position gripper (11) is released, and the adjusting nut tightening tool is used to tighten the parts of the new integrated sleeve (17). The remote measuring tool is placed on the transport component (12) of the transport positioning platform, and the remote measuring tool is positioned and fixed. The remote measuring tool is transported to the working position through the three-way motion mechanism of the transport positioning platform. Through remote measurement, the installation height of the new integrated sleeve (17) is confirmed to be consistent with the theoretical value, ensuring that the new integrated sleeve (17) is installed in place.

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