A nuclear power plant solder joint grinding simulation device and method thereof

Abstract

The present invention belongs to the field of nuclear power plant equipment maintenance, and relates to a simulation device and method for grinding nuclear power plant solder joints. The simulation device includes a simulation bench, a simulation shoulder and a solder joint grinding tool; the simulation bench includes a simulation bench base, a bracket, a cylindrical surface simulation part of a protection tube assembly and a support beam; the simulation shoulder is fixedly installed on the front surface of the cylindrical surface simulation part of the protection tube assembly; the solder joint grinding tool includes a solder joint grinding tool body, a grinding hole, a limit stop block and a positioning bolt, the solder joint grinding tool body is movably installed on the simulation shoulder, a grinding hole is formed in the top surface of the solder joint grinding tool body, and the limit stop blocks are symmetrically and fixedly installed on the inner top surface of the solder joint grinding tool body; the positioning bolt is detachably installed on the side surface of the adjacent surface of the solder joint grinding tool body. The present invention can simulate the shoulder structure of the protection tube assembly and its relative position with the protection tube assembly, and effectively prevent the damage to the main body of the protection tube assembly during solder joint grinding.

Description

Technical Field

[0001] The invention belongs to the field of nuclear power plant equipment maintenance, and particularly relates to a nuclear power plant solder joint grinding simulation device and method. Background Art

[0002] The first and second phases of Tianwan Nuclear Power Plant are four VVER-1000 nuclear power units. The nuclear reactor device is a B-428 type reactor. The main pressure boundary of the reactor is the reactor pressure vessel. Inside the pressure vessel is a fuel basket. The lower half inside the fuel basket is nuclear fuel, and control rods are installed in the nuclear fuel. The nuclear reaction power is adjusted by lifting or lowering the control rods in the nuclear fuel. The upper half inside the fuel basket is a protection tube assembly, which provides a channel and protection for the up and down movement of the control rods.

[0003] In order to extend the refueling cycle of the two units in the first phase of the project, the nuclear fuel has been replaced from AFA fuel assemblies to TVS-2M fuel assemblies. The two units in the second phase of the project used TVS-2M fuel assemblies for the first refueling. In order to meet the usage requirements of the TVS-2M fuel assemblies, it is necessary to adjust the longitudinal position of the protection tube assemblies of the four units.

[0004] The protection tube assembly is cylindrical in shape, and there is a ring-shaped shoulder in the middle of the outer surface of the cylinder. The protection tube assembly is placed on the upper end of the fuel basket through the shoulder, and thin backing plates are installed on both the upper and lower surfaces of the shoulder. The thickness of the backing plate on the lower surface of the shoulder determines the longitudinal position of the protection tube assembly. Therefore, the essence of adjusting the position of the protection tube assembly is to adjust the thickness of the backing plate on the lower surface of the shoulder. When adjusting, the sum of the thicknesses of the shoulder and the upper and lower backing plates cannot be changed. Therefore, when adjusting the lower backing plate, the upper backing plate also needs to be adjusted.

[0005] Adjusting the thickness of the backing plate means disassembling and replacing the backing plate. The backing plate is fastened to the shoulder by countersunk head screws, and two solder joints are welded to the head of each countersunk head screw to prevent loosening. Then, before removing the fastening countersunk head screws of the old backing plate, it is necessary to grind the solder joints of the countersunk head screws first. Solder joint grinding is one of the main tasks in the on-site implementation of adjusting the position of the protection tube assembly. Solder joint grinding is divided into two parts: First, the operator bends down to grind the solder joints on the upper backing plate of the shoulder. Second, after the upper backing plate is ground and removed, the protection tube assembly is lifted to a height equal to the head of the operator above the shoulder, and the operator looks up to grind the solder joints on the lower backing plate of the shoulder.

[0006] There are such difficulties in the on-site implementation of the position adjustment of the protection tube assembly: the radiation dose rate is high, the temperature is high, the risk of generating foreign objects is high at the operation site, and it takes up the key path time of the major overhaul. On-site operation requires a high degree of proficiency of the operators. Especially for the work of soldering point grinding, unskilled operation of the operators will take a lot of time. Therefore, it is necessary to conduct operation training for the operators before the formal implementation of the position adjustment of the protection tube assembly. However, the current shortcoming is the lack of simulation equipment for practical operation training.

[0007] The work of position adjustment of the protection tube assembly needs to be implemented on-site during the unit overhaul. The operation environment is harsh, including high radiation dose rate, high temperature, and high risk of foreign object generation. And the grinding of the countersunk head screws of the shoulder backing plate is the main work. Therefore, it is urgent to develop a simulation device for soldering point grinding in nuclear power plants, which can simulate the shoulder structure of the protection tube assembly and its relative position with the protection tube assembly, and at the same time can effectively prevent damage to the body of the protection tube assembly during soldering point grinding. Summary of the Invention

[0008] The purpose of the present invention is to provide a simulation device and method for soldering point grinding in nuclear power plants. The simulation device can simulate the shoulder structure of the protection tube assembly and its relative position with the protection tube assembly, and effectively prevent damage to the body of the protection tube assembly during soldering point grinding.

[0009] The technical solution to achieve the purpose of the present invention: A simulation device for soldering point grinding in nuclear power plants, including a simulation bench, a simulation shoulder, and a soldering point grinding tool;

[0010] The simulation bench includes a simulation bench base, brackets, a cylindrical surface simulation part of the protection tube assembly, and support beams. The brackets are symmetrically and fixedly installed on both sides of the simulation bench base. The cylindrical surface simulation part of the protection tube assembly is fixedly installed on the top surface of the simulation bench base. The support beams are respectively fixedly installed on the cylindrical surface simulation part of the protection tube assembly and the simulation bench base;

[0011] The simulation shoulder is fixedly installed on the front of the cylindrical surface simulation part of the protection tube assembly;

[0012] The soldering point grinding tool includes a soldering point grinding tool body, a grinding hole, a limit stop block, and a positioning bolt. The soldering point grinding tool body is movably installed on the simulation shoulder. A grinding hole is opened on the top surface of the soldering point grinding tool body. The limit stop blocks are symmetrically and fixedly installed on the inner top surface of the soldering point grinding tool body; The positioning bolt is detachably installed on the side surface of the adjacent surface of the soldering point grinding tool body.

[0013] Furthermore, the front of the cylindrical surface simulation part of the protection tube assembly and the front of the simulation bench base are located in the same vertical plane, and the support beam is arranged on the back of the cylindrical surface simulation part of the protection tube assembly.

[0014] Further, the top surface of the simulated shoulder with the shoulder backing plate installed thereon is oriented upward, corresponding to the shoulder height when grinding the solder joints of the shoulder backing plate on the protection tube assembly shoulder, and the simulated shoulder is installed at the lower front part of the cylindrical surface simulator of the protection tube assembly.

[0015] Further, the top surface of the simulated shoulder with the shoulder backing plate installed thereon is oriented downward, corresponding to the shoulder height when grinding the solder joints of the lower shoulder backing plate on the protection tube assembly shoulder, and the simulated shoulder is installed at the upper front part of the cylindrical surface simulator of the protection tube assembly.

[0016] Further, the simulated shoulder includes a shoulder body, a shoulder backing plate, a shoulder support frame, a countersunk head screw solder joint, and countersunk head screws. The shoulder backing plate is fixedly installed on the top surface of the shoulder body through the countersunk head screws, and the head of the countersunk head screw is welded with the countersunk head screw solder joint. The shoulder support frame is fixedly installed on one side of the shoulder body, and the simulated shoulder is fixedly installed on the front surface of the cylindrical surface simulator of the protection tube assembly through the shoulder support frame.

[0017] Further, the shoulder support frame is an isosceles triangle structure with an open top end.

[0018] Further, the shoulder support frame is symmetrically and fixedly connected to the shoulder body through the end with the open top end.

[0019] Further, the shoulder support frame is fixedly installed on the front surface of the cylindrical surface simulator of the protection tube assembly through fastening bolts.

[0020] Further, the main body of the solder joint grinding tool is a side U-shaped structure.

[0021] Further, the positioning bolts are respectively installed on the inner bottom surface and the inner end surface of the main body of the solder joint grinding tool.

[0022] Further, a handle is fixedly connected to the free end of the positioning bolt.

[0023] A grinding method for a solder joint grinding simulation device of a nuclear power plant includes the following steps:

[0024] Step (1), install the simulated shoulder on the front surface of the cylindrical surface simulator of the protection tube assembly of the simulation bench;

[0025] Step (2), install the solder joint grinding tool onto the shoulder body of the simulated shoulder;

[0026] Step (3), use an electric straight grinder to grind the countersunk head screw solder joints of the simulated shoulder;

[0027] Step (4), after grinding, screw out the countersunk head screws in the simulated shoulder;

[0028] Step (5): Repeat steps (2) - (4) to perform grinding on the next countersunk screw weld point until all countersunk screw weld points are ground.

[0029] Further, step (1) includes:

[0030] Step (1.1): Place the top surface of the simulated shoulder with the shoulder backing plate facing upward, and install the simulated shoulder on the lower part of the front surface of the cylindrical surface simulator of the protection tube assembly corresponding to the shoulder height when grinding the upper backing plate weld point on the shoulder of the protection tube assembly.

[0031] Step (1.2): Place the top surface of the simulated shoulder with the shoulder backing plate facing downward, and install the simulated shoulder on the upper part of the front surface of the cylindrical surface simulator of the protection tube assembly corresponding to the shoulder height when grinding the lower backing plate weld point on the shoulder of the protection tube assembly.

[0032] Further, step (2) includes:

[0033] Step (2.1): Loosen the four positioning bolts of the weld point grinding tool until the positioning bolts do not protrude from the inner surface of the weld point grinding tool.

[0034] Step (2.2): Install the main body of the weld point grinding tool on the shoulder body so that the limit stop block hooks the inner edge of the shoulder backing plate.

[0035] Step (2.3): Tighten the four positioning bolts to make the weld point grinding tool stable without shaking.

[0036] Further, step (3) specifically uses an electric straight grinder to grind the countersunk screw weld point of the simulated shoulder through the grinding hole of the weld point grinding tool.

[0037] The beneficial technical effects of the present invention are as follows:

[0038] 1. The nuclear power plant weld point grinding simulation device provided by the present invention fills the lack of practical training simulation equipment for the position adjustment work of the protection tube assembly. After the operators are trained using this set of equipment, their skill proficiency has been greatly improved, preparing the personnel skills for the formal implementation of the position adjustment work of the protection tube assembly;

[0039] 2. The simulation bench in the nuclear power plant weld point grinding simulation device provided by the present invention simulates the 200 mm distance between the grinding position and the cylindrical surface of the protection tube assembly body during the formal implementation of weld point grinding by adding a cylindrical surface simulator of the protection tube assembly. Due to the small distance, there are certain spatial limitations on the grinding operation of the operators. The addition of the cylindrical surface simulator of the protection tube assembly enables the operators to adapt to operating in such a narrow space in advance;

[0040] 3. In the simulation bench of a nuclear power plant solder joint grinding simulation device provided by the present invention, the solder joint grinding of the upper pad on the shoulder and the lower pad on the shoulder is concentrated on one simulation bench, and the simulation bench base is bolted to each component, which is detachable, reducing the occupation of the limited area of the plant and facilitating transportation;

[0041] 4. In the solder joint grinding tool of a nuclear power plant solder joint grinding simulation device provided by the present invention, by adding a grinding hole, the operator holds an electric straight grinder and grinds in this grinding hole, which can effectively limit the jumping and offset of the electric straight grinder and avoid damage to the body of the protection tube assembly by the grinding head of the straight grinder;

[0042] 5. In the solder joint grinding tool of a nuclear power plant solder joint grinding simulation device provided by the present invention, through the positioning bolts, the tool is firmly fixed on the simulation shoulder in the axial and radial directions to ensure precise grinding of the solder joint;

[0043] 6. After training the operation skills of the operator using a nuclear power plant solder joint grinding simulation device provided by the present invention, the grinding time for the countersunk head screw solder joint of 1 simulation shoulder is shortened from an average of 3 minutes to an average of 1.5 minutes; when implemented officially, there are 93 countersunk head screw solder joints on the protection tube assembly that need to be ground, and it is estimated that the grinding time can be saved by 93×1.5 minutes = 139.5 minutes = 2.325 hours. The environmental dose rate at the operation site is 0.4 mSv / h, and the collective radiation dose can be reduced by 0.4×2.325 = 0.93 mSv, effectively improving the radiation safety benefit. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a schematic structural diagram of the simulation bench in a nuclear power plant solder joint grinding simulation device provided by the present invention;

[0045] Figure 2 It is a schematic structural diagram of the simulation shoulder in a nuclear power plant solder joint grinding simulation device provided by the present invention;

[0046] Figure 3 It is a schematic structural diagram of the solder joint grinding tool in a nuclear power plant solder joint grinding simulation device provided by the present invention;

[0047] Figure 4A It is the installation position of the simulation shoulder on the simulation bench when the nuclear power plant solder joint grinding simulation device provided by the present invention is used to simulate the grinding of the solder joint of the lower pad on the shoulder of the protection tube assembly;

[0048] Figure 4B It is the installation position of the simulation shoulder on the simulation bench when the nuclear power plant solder joint grinding simulation device provided by the present invention is used to simulate the grinding of the solder joint of the upper pad on the shoulder of the protection tube assembly;

[0049] Figure 5 Schematic diagram of the use of a simulation device for grinding nuclear power plant solder joints provided by the present invention.

[0050] In the figure: 1 - simulation bench base; 2 - bracket; 3 - cylindrical surface simulation part of the protection tube assembly; 4 - support beam; 5 - simulated shoulder; 7 - shoulder body; 8 - shoulder backing plate; 9 - shoulder support frame; 10 - fastening bolt; 11 - counterbore; 12 - countersunk head screw solder joint; 13 - countersunk head screw; 14 - main body of the solder joint grinding tool; 15 - grinding hole; 16 - limit stop; 17 - positioning bolt; 18 - electric straight grinder. Specific embodiments

[0051] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0052] As Figures 1-5 shown, a simulation device for grinding nuclear power plant solder joints provided by the present invention includes a simulation bench, a simulated shoulder 5 and a solder joint grinding tool.

[0053] As Figure 1 shown, the simulation bench includes a simulation bench base 1, a bracket 2, a cylindrical surface simulation part 3 of the protection tube assembly and a support beam 4.

[0054] The simulation bench base 1 is a cuboid structure welded by steel beams; the bracket 2 is a triangular structure welded by steel beams, and two identical brackets 2 are symmetrically installed on both sides of the simulation bench base 1 through bolts for stabilizing the simulation bench; the cylindrical surface simulation part 3 of the protection tube assembly is a thin steel plate, which is installed on the top surface of the simulation bench base 1 through bolts, and the front surface of the cylindrical surface simulation part 3 of the protection tube assembly is in the same vertical plane as the front surface of the simulation bench base 1; the support beam 4 is symmetrically arranged on the back of the cylindrical surface simulation part 3 of the protection tube assembly, one end of the support beam 4 is welded on the left and right sides of the back of the cylindrical surface simulation part 3 of the protection tube assembly, and the other end is installed on the top surface of the simulation bench base 1 through bolts for supporting the cylindrical surface simulation part 3 of the protection tube assembly and reducing the vibration generated during solder joint grinding.

[0055] As Figure 2 shown, the simulated shoulder 5 is a component simulating the structure and size of the shoulder of the protection tube assembly, and the simulated shoulder 5 includes a shoulder body 7, a shoulder backing plate 8, a shoulder support frame 9, a fastening bolt 10, a counterbore 11, a countersunk head screw solder joint 12 and a countersunk head screw 13.

[0056] On the top surface of the shoulder body 7, there are 10 internal threaded holes for installing countersunk head screws 13; on the shoulder backing plate 8, there are 10 countersunk holes 11 corresponding to the internal threaded holes. By passing the countersunk head screws 13 through the countersunk holes 11 and screwing them into the internal threaded holes, the shoulder backing plate 8 is fixedly installed on the top surface of the shoulder body 7; on the head of each countersunk head screw 13, there are two countersunk head screw welding points 12, and the countersunk head screw welding points 12 are used to prevent the loosening of the countersunk head screws 13 and are the objects to be polished during the grinding of the welding points; the shoulder support frame 9 is an isosceles triangle structure with an open top end. The shoulder support frame 9 is symmetrically arranged on one side of the shoulder body 7, and the end of the open top end of the shoulder support frame 9 is symmetrically fixedly connected to the shoulder body 7 by welding; on the bottom edge of the shoulder support frame 9, there are symmetrically arranged screw holes, and the fastening bolts 10 pass through the screw holes to fixedly install the shoulder support frame 9 fixedly connected with the shoulder body 7 at the corresponding position on the front surface of the cylindrical surface simulation part 3 of the protection tube assembly, so as to play a role in stably supporting the simulated shoulder 5.

[0057] When simulating the grinding of the welding points on the upper backing plate of the shoulder of the protection tube assembly, the top surface of the simulated shoulder 5 with the shoulder backing plate 8 installed is facing upwards, corresponding to the shoulder height when grinding the welding points on the upper backing plate of the shoulder of the protection tube assembly. The simulated shoulder 5 is installed on the lower part of the front surface of the cylindrical surface simulation part 3 of the protection tube assembly through the fastening bolts 10; when simulating the grinding of the welding points on the lower backing plate of the shoulder of the protection tube assembly, the top surface of the simulated shoulder 5 with the shoulder backing plate 8 installed is facing downwards, corresponding to the shoulder height when grinding the welding points on the lower backing plate of the shoulder of the protection tube assembly. The simulated shoulder 5 is installed on the upper part of the front surface of the cylindrical surface simulation part 3 of the protection tube assembly through the fastening bolts 10.

[0058] As Figure 3 shown, the welding point grinding tool includes a welding point grinding tool body 14, a grinding hole 15, a limit stop 16 and a positioning bolt 17.

[0059] The welding point grinding tool body 14 is a side U-shaped structure formed by welding three iron plates, and the welding point grinding tool body 14 is movably installed on the shoulder body 7. On the top surface of the welding point grinding tool body 14, there is a grinding hole 15, and the position of the grinding hole 15 corresponds to the position of the countersunk hole 11 on the shoulder backing plate 8, which is used to accommodate the electric straight grinder 18 during the grinding of the welding points and limit the jumping and offset of the electric straight grinder 18. There are 2 limit stops 16, which are symmetrically welded on the inner top surface of the welding point grinding tool body 14 and are used to clamp the inner edge of the shoulder backing plate 8. There are 4 positioning bolts 17, 2 positioning bolts 17 are symmetrically arranged on the inner bottom surface of the welding point grinding tool body 14, and 2 positioning bolts 17 are symmetrically arranged on the inner end surface of the welding point grinding tool body 14, which are used to fix the welding point grinding tool on the simulated shoulder 5; the free end of the positioning bolt 17 is fixedly connected with a handle to facilitate the screwing of the positioning bolt 17.

[0060] As shown in Figures 4 - 5, a grinding method for a nuclear power plant solder joint grinding simulation device provided by the present invention includes the following steps:

[0061] Step (1): Install the simulation shoulder 5 on the front of the cylindrical surface simulation part 3 of the protection pipe assembly of the simulation bench.

[0062] Step (1.1): Place the top surface of the simulation shoulder 5 with the shoulder backing plate 8 facing upwards. Corresponding to the shoulder height when grinding the upper backing plate solder joint on the shoulder of the protection pipe assembly, install the simulation shoulder 5 on the lower part of the front of the cylindrical surface simulation part 3 of the protection pipe assembly.

[0063] Step (1.2): Place the top surface of the simulation shoulder 5 with the shoulder backing plate 8 facing downwards. Corresponding to the shoulder height when grinding the lower backing plate solder joint on the shoulder of the protection pipe assembly, install the simulation shoulder 5 on the upper part of the front of the cylindrical surface simulation part 3 of the protection pipe assembly.

[0064] Step (2): Install the solder joint grinding tool on the shoulder body 7 of the simulation shoulder 5.

[0065] Step (2.1): Loosen the four positioning bolts 17 of the solder joint grinding tool until the positioning bolts 17 do not protrude from the inner surface of the solder joint grinding tool.

[0066] Step (2.2): Install the solder joint grinding tool body 14 on the shoulder body 7, so that the limit stop 16 hooks the inner edge of the shoulder backing plate 8.

[0067] Step (2.3): Tighten the four positioning bolts 17 to make the solder joint grinding tool stable without shaking.

[0068] Step (3): Use the electric straight grinder 18 to grind the countersunk head screw solder joint 12 of the simulation shoulder 5.

[0069] Use the electric straight grinder 18 to pass through the grinding hole 15 of the solder joint grinding tool to grind the countersunk head screw solder joint 12 of the simulation shoulder 5.

[0070] Step (4): After grinding, unscrew the countersunk head screw 13 in the simulation shoulder 5.

[0071] Step (5): Repeat Step (2) - Step (4) to grind the next countersunk head screw solder joint 12 until all the countersunk head screw solder joints 12 are ground.

[0072] The present invention has been described in detail above in conjunction with the accompanying drawings and embodiments. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those of ordinary skill in the art, various changes can be made without departing from the gist of the present invention. The content not described in detail in the present invention can all adopt the prior art.

Claims

1. A simulation device for grinding nuclear power plant solder joints, characterized in that, the simulation device includes a simulation bench, a simulation shoulder (5) and a solder joint grinding tool; The simulation bench includes a simulation bench base (1), brackets (2), a cylindrical surface simulation part (3) of the protection tube assembly and a support beam (4). The brackets (2) are symmetrically and fixedly installed on both sides of the simulation bench base (1). The cylindrical surface simulation part (3) of the protection tube assembly is fixedly installed on the top surface of the simulation bench base (1). The support beam (4) is fixedly installed on the cylindrical surface simulation part (3) of the protection tube assembly and the simulation bench base (1) respectively; The simulation shoulder (5) is fixedly installed on the front of the cylindrical surface simulation part (3) of the protection tube assembly; The solder joint grinding tool includes a solder joint grinding tool body (14), a grinding hole (15), a limit stop (16) and a positioning bolt (17). The solder joint grinding tool body (14) is movably installed on the simulation shoulder (5). A grinding hole (15) is opened on the top surface of the solder joint grinding tool body (14). The limit stops (16) are symmetrically and fixedly installed on the inner top surface of the solder joint grinding tool body (14); The positioning bolt (17) is detachably installed on the side surface of the adjacent surface of the solder joint grinding tool body (14).

2. The simulation device for grinding nuclear power plant solder joints according to claim 1, characterized in that, the front of the cylindrical surface simulation part (3) of the protection tube assembly and the front of the simulation bench base (1) are located in the same vertical plane, and the support beam (4) is arranged on the back of the cylindrical surface simulation part (3) of the protection tube assembly.

3. The simulation device for grinding nuclear power plant solder joints according to claim 1, characterized in that, the simulation shoulder (5) has the top surface with the shoulder backing plate (8) installed facing upwards, corresponding to the shoulder height when grinding the solder joint on the upper backing plate of the protection tube assembly shoulder, and the simulation shoulder (5) is installed on the lower part of the front of the cylindrical surface simulation part (3) of the protection tube assembly.

4. The simulation device for grinding nuclear power plant solder joints according to claim 1, characterized in that, the simulation shoulder (5) has the top surface with the shoulder backing plate (8) installed facing downwards, corresponding to the shoulder height when grinding the solder joint on the lower backing plate of the protection tube assembly shoulder, and the simulation shoulder (5) is installed on the upper part of the front of the cylindrical surface simulation part (3) of the protection tube assembly.

5. The simulation device for grinding nuclear power plant solder joints according to claim 1, characterized in that, the simulation shoulder (5) includes a shoulder body (7), a shoulder backing plate (8), a shoulder support frame (9), a countersunk head screw solder joint (12) and a countersunk head screw (13). The shoulder backing plate (8) is fixedly installed on the top surface of the shoulder body (7) through the countersunk head screw (13). The head of the countersunk head screw (13) is welded with the countersunk head screw solder joint (12). The shoulder support frame (9) is fixedly installed on one side of the shoulder body (7). The simulation shoulder (5) is fixedly installed on the front of the cylindrical surface simulation part (3) of the protection tube assembly through the shoulder support frame (9).

6. The simulation device for grinding nuclear power plant solder joints according to claim 5, characterized in that, the shoulder support frame (9) is an isosceles triangle structure with an open top.

7. An apparatus for simulating the grinding of solder joints in a nuclear power plant according to claim 6, characterized in that, the shoulder support frame (9) is symmetrically and fixedly connected to the shoulder body (7) through the end with an open top.

8. An apparatus for simulating the grinding of solder joints in a nuclear power plant according to claim 7, characterized in that, the shoulder support frame (9) is fixedly installed on the front surface of the cylindrical surface simulation part (3) of the protection tube assembly through fastening bolts (10).

9. An apparatus for simulating the grinding of solder joints in a nuclear power plant according to claim 1, characterized in that, the main body (14) of the solder joint grinding tool is of a side U-shaped structure.

10. An apparatus for simulating the grinding of solder joints in a nuclear power plant according to claim 9, characterized in that, the positioning bolts (17) are respectively installed on the inner bottom surface and the inner end surface of the main body (14) of the solder joint grinding tool.

11. An apparatus for simulating the grinding of solder joints in a nuclear power plant according to claim 1, characterized in that, a handle is fixedly connected to the free end of the positioning bolt (17).

12. A grinding method using the apparatus for simulating the grinding of solder joints in a nuclear power plant according to claim 5, characterized in that, the method includes the following steps: Step (1), install the simulated shoulder (5) on the front surface of the cylindrical surface simulation part (3) of the protection tube assembly of the simulation bench; Step (2), install the solder joint grinding tool on the shoulder body (7) of the simulated shoulder (5); Step (3), use an electric straight grinder (18) to grind the countersunk head screw solder joints (12) of the simulated shoulder (5); Step (4), after grinding, screw out the countersunk head screws (13) in the simulated shoulder (5); Step (5), repeat Step (2) - Step (4) to grind the next countersunk head screw solder joint (12) until all the countersunk head screw solder joints (12) are ground.

13. A grinding method using the apparatus for simulating the grinding of solder joints in a nuclear power plant according to claim 12, characterized in that, Step (1) includes: Step (1.1), place the top surface of the simulated shoulder (5) with the shoulder backing plate (8) facing up, and install the simulated shoulder (5) on the lower part of the front surface of the cylindrical surface simulation part (3) of the protection tube assembly corresponding to the shoulder height when grinding the upper backing plate solder joints on the shoulder of the protection tube assembly; Step (1.2), place the top surface of the simulated shoulder (5) with the shoulder backing plate (8) facing down, and install the simulated shoulder (5) on the upper part of the front surface of the cylindrical surface simulation part (3) of the protection tube assembly corresponding to the shoulder height when grinding the lower backing plate solder joints on the shoulder of the protection tube assembly.

14. A grinding method using the apparatus for simulating the grinding of solder joints in a nuclear power plant according to claim 12, characterized in that, Step (2) includes: Step (2.1), loosen the four positioning bolts (17) of the solder joint grinding tool until the positioning bolts (17) do not protrude from the inner surface of the solder joint grinding tool; Step (2.2), install the main body (14) of the solder joint grinding tool on the shoulder body (7) so that the limit stop block (16) hooks the inner edge of the shoulder backing plate (8); Step (2.3), tighten the four positioning bolts (17) to make the solder joint grinding tool stable without shaking.

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