A method for repairing a seal weld of a control rod drive mechanism upper-lower assembly

Abstract

The application provides a control rod drive mechanism upper and lower assembly sealing weld repair method, which comprises the following steps: cutting along the sealing weld of the drive mechanism by using a sealing weld cutting device to separate the upper assembly and the lower assembly of the drive mechanism; taking off the upper assembly and grinding the bevels of the upper assembly and the lower assembly respectively to make the bevels of the upper assembly and the lower assembly have the same shape as the initial bevels and meet the welding requirements; reassembling the upper assembly and the lower assembly and measuring the bevel gap between the bevels of the upper assembly and the lower assembly; and welding the upper assembly and the lower assembly according to the size of the bevel gap. The application can make the welding repair one-time forming, improve the repair efficiency, save the repair time, and make the quality of the sealing weld the same as that of the first welding, so that special safety evaluation work is not needed.

Description

Technical Field

[0001] This invention relates to the field of nuclear power technology, and more specifically, to a method for repairing the sealing welds of the upper and lower components of a control rod drive mechanism. Background Technology

[0002] Nuclear power is a low-carbon, efficient, and clean energy source. With the goals of "carbon neutrality" and "carbon peaking," the advantages of nuclear power are further highlighted. The reactor control rod drive mechanism is a servo mechanism of the reactor control and protection system. Its main function is to drive the control rod assembly up and down within the reactor core according to instructions, maintain the control rod assembly at the commanded height, release the control rod assembly upon power failure, and allow it to quickly insert into the reactor core under gravity. This completes functions such as reactor startup, power regulation, power maintenance, normal shutdown, and accident shutdown.

[0003] The sealing welds between different components in the control rod drive mechanism are a special structure called Canopy welds or Ω welds. These welds form part of the pressure boundary of the reactor's primary loop system and are crucial to the safe operation of the entire reactor. Located between the upper and lower components of each drive mechanism, the Canopy welds have limited welding space. Furthermore, the Canopy weld bevel thickness is 2.35mm ± 0.05mm, with a bevel gap of 1.2mm. Due to structural constraints, the weld must be formed on both sides in a single pass, making welding extremely difficult. Additionally, because the base material of the Canopy weld is thin, post-weld finishing is not possible to prevent further thinning; the sealing weld must be formed successfully in one pass. Since the Canopy weld wall thickness is only about 2.35mm, weld failure can easily lead to reactor coolant leakage. Moreover, if quality problems occur with the Canopy welds during the manufacturing and operation of the main nuclear power equipment, repair is hampered by the limited space, making ordinary machining and welding processes impossible, and compromising the timeliness and safety of Canopy weld repair.

[0004] In existing technologies, when a Canopy seal weld leaks, a large amount of fused metal is typically deposited on the surface to seal the leak. However, this method involves a large amount of weld deposit, high heat input due to the structure, requires specialized safety assessments after repair, and results in poor repair quality and low efficiency. Summary of the Invention

[0005] The problem addressed by this invention is how to provide a repair method for the sealing welds of the upper and lower components of a drive mechanism that offers high repair quality and efficiency and eliminates the need for post-repair safety assessments.

[0006] To address at least one of the aforementioned problems, the present invention provides a method for repairing the sealing weld of the upper and lower components of a control rod drive mechanism, comprising the following steps:

[0007] Step S1: Use a sealing weld cutting device to cut along the sealing weld of the drive mechanism to separate the upper and lower components of the drive mechanism.

[0008] Step S2: Remove the upper component and grind the bevels of the upper component and the lower component respectively to make the bevels of the upper component and the lower component the same as the initial bevel shape, so as to meet the welding requirements;

[0009] Step S3: Reassemble the upper component and the lower component, and measure the bevel gap between the bevels of the upper component and the lower component;

[0010] Step S4: Weld the upper component and the lower component according to the size of the bevel gap. The welding torch placement distance after arc initiation is set to 1.6-1.75mm, the base value of the welding current is set to 58-65A, the peak value of the welding current is set to 114-125A, the welding voltage is set to 9.9-10.5V, the base value of the wire feed speed is set to 920-950mm / min, and the peak value of the wire feed speed is set to 1720-1850mm / min.

[0011] Preferably, in step S4, when the bevel gap is 1.2mm, the welding torch placement distance after arc initiation is set to 1.6mm, the base value of the welding current is set to 58A, the peak value of the welding current is set to 114A, the welding voltage is set to 9.9V, the base value of the wire feed speed is set to 920mm / min, and the peak value of the wire feed speed is set to 1720mm / min;

[0012] When the bevel gap is 1.25mm, the welding torch placement distance after arc initiation is set to 1.65mm, the base value of the welding current is set to 60A, the peak value of the welding current is set to 115A, the welding voltage is set to 10.0V, the base value of the wire feed speed is set to 920mm / min, and the peak value of the wire feed speed is set to 1750mm / min.

[0013] When the bevel gap is 1.3mm, the welding torch placement distance after arc initiation is set to 1.7mm, the base value of the welding current is set to 65A, the peak value of the welding current is set to 120A, the welding voltage is set to 10.2V, the base value of the wire feed speed is set to 950mm / min, and the peak value of the wire feed speed is set to 1800mm / min.

[0014] When the bevel gap is 1.35mm, the welding torch placement distance after arc initiation is set to 1.75mm, the base value of the welding current is set to 65A, the peak value of the welding current is set to 125A, the welding voltage is set to 10.5V, the base value of the wire feed speed is set to 950mm / min, and the peak value of the wire feed speed is set to 1850mm / min.

[0015] Preferably, in step S1, the sealing weld cutting device includes a driving device, a fixed ring, and a rotating ring located above the fixed ring. The rotating ring is provided with a knife holder, and the driving device is used to drive the rotating ring to rotate. Both the fixed ring and the rotating ring are of a segmented structure.

[0016] Preferably, step S1 includes:

[0017] Step S11: Mark the beveling processing line and processing area on the drive mechanism, and then install the sealing weld cutting device onto the drive mechanism;

[0018] Step S12: Install a grooving knife on the knife holder of the sealing weld cutting device, and align the sealing weld cutting device using a dial indicator and set the knife.

[0019] Step S13: Start the sealing weld cutting device, process and remove the high point of the sealing weld, and then perform grooving to obtain the bevel of the upper component and the lower component;

[0020] Step S14: Replace the grooving knife on the knife holder with a chamfering knife, and restart the sealing weld cutting device to chamfer the bevels of the upper component and the lower component.

[0021] Step S15: Remove the chamfering knife and remove the sealing weld cutting device from the drive mechanism.

[0022] Preferably, in steps S13-S14, an inflation device is used to inflate the drive mechanism from the bottom, thereby generating positive pressure inside the drive mechanism.

[0023] Preferably, in step S12, the grooving tool includes a first shank and a cutting head, the cutting head is located at the end of the first shank, and the thickness of the cutting head is less than or equal to 2 mm.

[0024] Preferably, in step S14, the chamfering tool includes a second handle and a cutting edge located at the end of the second handle, wherein the included angle of the cutting edge is 37.5°.

[0025] Preferably, in step S2, during the bevel grinding process of the upper component and the lower component, a contouring tool is used to check the dimensions of the bevels of the upper component and the lower component until the bevels of the upper component and the lower component are the same as the initial bevel shape of the sealing weld.

[0026] Preferably, in step S2, a spherical grinding head with a diameter of 3mm is used to grind the bevels of the upper component and the lower component.

[0027] Preferably, in step S3, during the reassembly of the upper component and the lower component, the upper component and the lower component are fixed by three pre-tightening operations, wherein the pre-tightening force of the first pre-tightening is 163 N.M, the pre-tightening force of the second pre-tightening is 325 N.M, and the pre-tightening force of the third pre-tightening is 475 N.M.

[0028] This invention involves cutting and disassembling the drive mechanism to separate its upper and lower components. The bevels of both components are then ground to match the initial bevel shape, meeting welding requirements. The components are then reassembled, and welding is performed using different parameters based on the bevel gap size. Further processing of the disassembled components ensures the bevels are restored to their original shape. Since the bevel spacing changes after grinding, appropriate welding parameters are selected based on the specific gap, allowing for one-time welding repair. This improves repair efficiency, saves time, and produces a seal weld of the same quality as the initial weld, eliminating the need for a dedicated safety assessment. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the sealing weld of the control rod drive mechanism in an embodiment of the present invention;

[0030] Figure 2 This is a flowchart illustrating the method for repairing the sealing weld of the upper and lower components of the control rod drive mechanism in an embodiment of the present invention.

[0031] Figure 3 This is a schematic diagram of the grooving tool in an embodiment of the present invention;

[0032] Figure 4 This is a schematic diagram of the chamfering tool in an embodiment of the present invention;

[0033] Figure 5 This is a schematic diagram of the structure of the first contouring tool in an embodiment of the present invention;

[0034] Figure 6This is a schematic diagram of the structure of the second contouring tool in an embodiment of the present invention.

[0035] Explanation of reference numerals in the attached figures:

[0036] 1. Grooving tool; 11. First tool holder; 12. Tool head; 2. Chamfering tool; 21. Second tool holder; 22. Blade; 3. First contouring tool; 4. Second contouring tool. Detailed Implementation

[0037] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below.

[0038] It should be noted that, where there is no conflict, the features in the embodiments of this invention can be combined with each other. Furthermore, it should be understood that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in sequences other than those illustrated or described herein.

[0039] Each pressurized water reactor pressure vessel has 61-89 drive mechanisms. The small spacing between these drive mechanisms on the pressure vessel results in limited welding space. Furthermore, the sealing welds of the control rod drive mechanisms have a special design structure (generally referred to as Canopy welds or Ω welds). The Canopy welds are located between the upper and lower components of each drive mechanism, and the bevel thickness of the Canopy welds is approximately 2.35 mm, with a bevel gap of approximately 1.2 mm. This requires single-pass welding with double-sided forming, making the welding process quite challenging. Figure 1 This is a schematic diagram of the sealing weld in the control rod drive mechanism. The black shaded area in the diagram represents the Canopy sealing weld. The structure above the Canopy sealing weld is the upper component, and the structure below it is the lower component. Figure 1 As shown, the thickness of the Canopy sealing weld (i.e., the bevel gap) is 1.2 mm, the bevel thickness is 2.35 mm, and the welding process can only be carried out through external welding.

[0040] like Figure 2 As shown, this embodiment of the invention provides a method for repairing the sealing weld of the upper and lower components of a control rod drive mechanism, including the following steps:

[0041] Step S1: Use a sealing weld cutting device to cut along the sealing weld of the drive mechanism to separate the upper and lower components of the drive mechanism.

[0042] Step S2: Remove the upper component and grind the bevels of the upper component and the lower component respectively to make the bevels of the upper component and the lower component the same as the initial bevel shape, so as to meet the welding requirements;

[0043] Step S3: Reassemble the upper component and the lower component, and measure the bevel gap between the bevels of the upper component and the lower component;

[0044] Step S4: Weld the upper component and the lower component according to the size of the bevel gap. The welding torch placement distance after arc initiation is set to 1.6-1.75mm, the base value of the welding current is set to 58-65A, the peak value of the welding current is set to 114-125A, the welding voltage is set to 9.9-10.5V, the base value of the wire feed speed is set to 920-950mm / min, and the peak value of the wire feed speed is set to 1720-1850mm / min.

[0045] In step S1, the sealing weld cutting device includes a driving device, a fixed ring, and a rotating ring located above the fixed ring. A knife holder is provided on the rotating ring, and the driving device is used to drive the rotating ring to rotate. Both the fixed ring and the rotating ring are of a segmented structure.

[0046] That is, the sealing weld cutting device includes a fixed ring and a rotating ring located above the fixed ring. Both the fixed ring and the rotating ring are of a segmented structure, and the multiple segmented structures are detachably connected to facilitate the installation of the fixed ring and the rotating ring onto the periphery of the drive mechanism. The inner wall of the fixed ring can abut against the outer wall of the drive mechanism, thereby fixing the sealing weld cutting device onto the drive mechanism. The rotating ring is provided with a tool holder for mounting cutting tools. When the drive device drives the rotating ring, the rotating ring drives the tool on the tool holder to rotate, thereby performing the cutting operation.

[0047] The sealing weld cutting device provided in this embodiment of the invention occupies a small space and has a segmented structure, which can be applied to situations where the spacing between the control rod drive mechanisms is small, and the cutting quality is high.

[0048] Step S1 includes the following steps:

[0049] Step S11: Mark the beveling processing line and processing area on the drive mechanism, and then install the sealing weld cutting device onto the drive mechanism;

[0050] Step S12: Install the grooving knife 1 on the knife holder of the sealing weld cutting device, and align the sealing weld cutting device with a dial indicator and set the knife.

[0051] Step S13: Start the sealing weld cutting device, process and remove the high point of the sealing weld, and then perform grooving to obtain the bevel of the upper component and the lower component;

[0052] Step S14: Replace the grooving knife 1 on the knife holder with the chamfering knife 2, and restart the sealing weld cutting device to chamfer the bevels of the upper component and the lower component.

[0053] Step S15: Remove the chamfering knife 2 and remove the sealing weld cutting device from the drive mechanism.

[0054] In step S11, by marking the bevel processing line and processing area on the drive mechanism, the cutting position and area can be clearly defined, reducing cutting processing errors.

[0055] In step S12, the drive mechanism can be slotted by installing the grooving tool 1. Specifically, the structure of the grooving tool 1 is as follows: Figure 3 As shown, the device includes a first tool holder 11 and a tool head 12. The tool head 12 is located at the end of the first tool holder 11, and the thickness of the tool head 12 is less than or equal to 2 mm. By using the tool head 12 with a thickness of less than or equal to 2 mm to groove the sealing weld of the drive mechanism, a groove that meets the requirements can be obtained, avoiding excessively large grooves that may affect subsequent welding.

[0056] Figure 3 Image (a) is a front view of the grooving tool 1. Figure 3 (b) is a bottom view of the grooving tool 1. Figure 3 (c) is the right view of the grooving tool 1. Figure 3 It can be seen that the cutting head 12 is located at the end of the first shank 11, and the thickness of the cutting head 12 gradually increases from the end close to the first shank 11 to the end away from the first shank 11, with the thickness at the end away from the first shank 11 being less than or equal to 2mm; in addition, the thickness of the cutting head 12 also gradually decreases along the horizontal direction, forming a cutting edge, which facilitates the cutting of the sealing weld.

[0057] In step S13, after installing the grooving cutter 1, the high point of the sealing weld is first processed to remove it, and then grooving is performed to obtain the bevel of the upper component and the lower component. At this time, the upper component and the lower component of the drive mechanism are separated.

[0058] In step S14, the grooving cutter 1 on the tool holder is replaced with a chamfering cutter 2 to chamfer the bevels of the upper and lower components. The chamfering cutter 2 includes a second handle 21 and a cutting edge 22 located at the end of the second handle 21. The included angle of the cutting edge is 37.5°. The chamfering cutter 2 with an included angle of 37.5° can form a suitable chamfer on the bevels of the upper and lower components, which is convenient for further processing.

[0059] Figure 4 Image (a) is the front view of chamfering tool 2. Figure 4 (b) is Figure 4 Cross-sectional view at point (a) AA. Figure 4 Image (c) is a top view of chamfering tool 2. Figure 4 The included angle α shown in (a) is the included angle of the cutting edge. Figure 4 It can be seen that the cutting edge 22 of the chamfering knife 2 is located at the end of the second handle 21, and the cutting edge 22 forms an included angle of 37.5°.

[0060] In step S15, after the drive mechanism is processed by the grooving knife 1 and the chamfering knife 2 in sequence, the sealing weld cutting device can be removed.

[0061] In addition, in steps S13-S14, during the process of cutting the sealing weld of the drive mechanism using the grooving knife 1 and the chamfering knife 2, in order to prevent cutting debris from entering the drive mechanism, air is injected at the bottom of the drive mechanism to create positive pressure inside the drive mechanism and discharge the cutting debris.

[0062] In step S2, the upper component is removed, and the bevels of the upper component and the lower component are ground. During this process, a contouring tool is used to check the dimensions of the bevels of the upper component and the lower component until the bevels of the upper component and the lower component are the same as the initial bevel shape.

[0063] In other words, to facilitate further processing of the bevels of the upper and lower components to meet requirements, the upper and lower components of the drive mechanism are disassembled. After the upper component is removed, the bevels of both the upper and lower components are ground separately. To ensure welding quality, a contour tool is used for dimensional inspection during grinding. The shape of the contour tool is the same as the initial bevel shape. Therefore, by combining the contour tool with dimensional inspection and grinding, the bevels of the upper and lower components after grinding can be made to match the initial bevel shape, thus meeting welding requirements.

[0064] Furthermore, a 3mm diameter ball grinding head is selected during the grinding process to ensure the precision of the bevel and improve the welding quality.

[0065] In one embodiment, the length of the drive mechanism is 8147mm, which has poor stability during hoisting and installation and poses a hoisting risk. Therefore, after cutting and disassembling the upper component of the drive mechanism, the upper component is placed in a hoisting tool with multiple limit rings, and the two ends of the drive mechanism are fixed before hoisting to avoid the drive mechanism shaking and causing collisions during the hoisting process.

[0066] In another embodiment, the structure of the first contouring tool 3 corresponding to the bevel of the upper component is as follows: Figure 5 As shown, the structure of the second contouring tool 4 corresponding to the bevel of the lower component is as follows: Figure 6 As shown.

[0067] like Figure 5 and Figure 6 As shown, the contouring tool includes a first contouring tool 3 and a second contouring tool 4. The shape of the first contouring tool 3 is the same as the initial bevel shape of the upper component, and the shape of the second contouring tool 4 is the same as the initial bevel shape of the lower component. By using the first contouring tool 3 and the second contouring tool 4 for dimensional checks during the grinding process, the required bevel dimensions can be obtained, thereby meeting the welding requirements.

[0068] In step S3, in order to make the bevel gap between the assembled upper component and the lower component uniform, three pre-tightening processes are performed during the assembly process. The pre-tightening force for the first pre-tightening is 163 N.M, the pre-tightening force for the second pre-tightening is 325 N.M, and the pre-tightening force for the third pre-tightening is 475 N.M.

[0069] In step S4, since the bevel gap varies after grinding, the welding parameters are adjusted according to the bevel gap during welding. The welding torch placement distance after arc initiation is set to 1.6-1.75mm, the base value of the welding current is set to 58-65A, the peak value is set to 114-125A, the welding voltage is set to 9.9-10.5V, the base value of the wire feed speed is set to 920-950mm / min, and the peak value is set to 1720-1850mm / min. Specifically:

[0070] When the bevel gap is 1.2mm, the welding torch placement distance after arc initiation is set to 1.6mm, the base value of the welding current is set to 58A, the peak value of the welding current is set to 114A, the welding voltage is set to 9.9V, the base value of the wire feed speed is set to 920mm / min, and the peak value of the wire feed speed is set to 1720mm / min.

[0071] When the bevel gap is 1.25mm, the welding torch placement distance after arc initiation is set to 1.65mm, the base value of the welding current is set to 60A, the peak value of the welding current is set to 115A, the welding voltage is set to 10.0V, the base value of the wire feed speed is set to 920mm / min, and the peak value of the wire feed speed is set to 1750mm / min.

[0072] When the bevel gap is 1.3mm, the welding torch placement distance after arc initiation is set to 1.7mm, the base value of the welding current is set to 65A, the peak value of the welding current is set to 120A, the welding voltage is set to 10.2V, the base value of the wire feed speed is set to 950mm / min, and the peak value of the wire feed speed is set to 1800mm / min.

[0073] When the bevel gap is 1.35mm, the welding torch placement distance after arc initiation is set to 1.75mm, the base value of the welding current is set to 65A, the peak value of the welding current is set to 125A, the welding voltage is set to 10.5V, the base value of the wire feed speed is set to 950mm / min, and the peak value of the wire feed speed is set to 1850mm / min.

[0074] By setting different welding parameters according to different bevel gaps, it is possible to ensure one-time forming and good welding quality for different bevel gaps.

[0075] For example, when the bevel gap is 1.2 mm, the complete welding procedure and welding parameters are shown in Table 1.

[0076] Table 1 Welding procedure for a bevel gap of 1.2 mm

[0077]

[0078]

[0079] It should be understood that when the bevel gap is different, the corresponding welding parameters are adjusted according to the size of the bevel gap, but the overall welding procedure is the same.

[0080] The repair method provided in this invention separates the upper and lower components by cutting the drive mechanism from the sealing weld. Then, the bevels of the upper and lower components are repaired and processed to restore them to their initial bevel shapes. Since the grinding process causes changes in the bevel gap, different welding parameters are set according to different bevel gaps to complete the welding of the upper and lower components. This allows the sealing weld to be formed in one step, significantly improving repair efficiency and saving repair time. Furthermore, since the same welding procedure as the initial welding is used during the repair process, no special safety assessment is required, ensuring the quality of the welding.

[0081] While the disclosure is as stated above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of this disclosure, and all such changes and modifications will fall within the protection scope of this invention.

Claims

1. A method of repairing a seal weld of a control rod drive mechanism upper-lower assembly, comprising: The method comprises the following steps: Step S1, cutting along the sealing weld of the driving mechanism by using a sealing weld cutting device to separate the upper assembly and the lower assembly of the driving mechanism; Step S2, removing the upper assembly, and grinding the bevels of the upper assembly and the lower assembly respectively, so that the bevels of the upper assembly and the lower assembly are the same as the initial bevel shape and meet the welding requirements; Step S3, reassembling the upper assembly and the lower assembly, and measuring the bevel gap between the bevels of the upper assembly and the lower assembly; Step S4, welding the upper assembly and the lower assembly according to the size of the bevel gap, wherein the post-arc welding gun placement distance is set to 1.6-1.75mm, the base value of the welding current is set to 58-65A, the peak value of the welding current is set to 114-125A, the welding voltage is set to 9.9-10.5V, and the base value of the wire feeding speed is set to 920-950mm / min, and the peak value of the wire feeding speed is set to 1720-1850mm / min; In the step S1, the sealing weld cutting device comprises a driving device, a fixed ring, and a rotating ring above the fixed ring, the rotating ring is movably connected with the fixed ring, a tool holder is arranged on the rotating ring, and the driving device is used to drive the rotating ring to rotate, wherein the fixed ring and the rotating ring are both split structure; In the step S4, when the bevel gap is 1.2mm, the post-arc welding gun placement distance is set to 1.6mm, the base value of the welding current is set to 58A, the peak value of the welding current is set to 114A, the welding voltage is set to 9.9V, the base value of the wire feeding speed is set to 920mm / min, and the peak value of the wire feeding speed is set to 1720mm / min; When the bevel gap is 1.25mm, the post-arc welding gun placement distance is set to 1.65mm, the base value of the welding current is set to 60A, the peak value of the welding current is set to 115A, the welding voltage is set to 10.0V, the base value of the wire feeding speed is set to 920mm / min, and the peak value of the wire feeding speed is set to 1750mm / min; When the bevel gap is 1.3mm, the post-arc welding gun placement distance is set to 1.7mm, the base value of the welding current is set to 65A, the peak value of the welding current is set to 120A, the welding voltage is set to 10.2V, the base value of the wire feeding speed is set to 950mm / min, and the peak value of the wire feeding speed is set to 1800mm / min; When the bevel gap is 1.35mm, the post-arc welding gun placement distance is set to 1.75mm, the base value of the welding current is set to 65A, the peak value of the welding current is set to 125A, the welding voltage is set to 10.5V, the base value of the wire feeding speed is set to 950mm / min, and the peak value of the wire feeding speed is set to 1850mm / min.

2. The method of claim 1, wherein: The step S1 comprises: S11, groove processing line and processing area are drawn on the driving mechanism, and then the sealing weld cutting device is installed on the driving mechanism; S12, a slotting cutter (1) is installed on the cutter holder of the sealing weld cutting device, the sealing weld cutting device is calibrated and the cutter is set; S13, the sealing weld cutting device is started, the high point of the sealing weld is processed and removed, and then slotting is processed to obtain the groove of the upper assembly and the lower assembly; S14, the slotting cutter (1) on the cutter holder is replaced with a chamfering cutter (2), the sealing weld cutting device is started again, and the groove of the upper assembly and the lower assembly is chamfered and formed; S15, the chamfering cutter (2) is removed, and the sealing weld cutting device is removed from the driving mechanism.

3. The method of claim 2, wherein the method further comprises: In steps S13-S14, the driving mechanism is inflated from the bottom to generate positive pressure in the driving mechanism.

4. The method of claim 2, wherein the method further comprises: In step S12, the slotting cutter (1) includes a first cutter handle (11) and a cutter head (12), the cutter head (12) is located at the end of the first cutter handle (11), and the thickness of the cutter head (12) is less than or equal to 2mm.

5. The method of claim 2, wherein the method further comprises: In step S14, the chamfering cutter (2) includes a second cutter handle (21) and a blade portion (22) located at the end of the second cutter handle (21), and the included angle of the blade portion (22) is 37.5°.

6. The control rod drive mechanism upper and lower assembly seal weld repair method of claim 1, wherein, In step S2, during the grinding process of the grooves of the upper assembly and the lower assembly, a profiling tool is used to check the size of the grooves of the upper assembly and the lower assembly until the grooves of the upper assembly and the lower assembly are the same as the initial groove shape of the sealing weld.

7. The method of claim 6, wherein the method further comprises: In step S2, a spherical grinding head with a diameter of 3mm is used to grind the grooves of the upper assembly and the lower assembly.

8. The method of claim 1, wherein, In step S3, during the reassembly of the upper assembly and the lower assembly, the upper assembly and the lower assembly are fixed by three pre-tightenings, wherein the pre-tightening force of the first pre-tightening is 163N.M, the pre-tightening force of the second pre-tightening is 325N.M, and the pre-tightening force of the third pre-tightening is 475N.M.

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