Tube socket clamping device for accurately simulating mechanical boundary of reactor fuel assembly

Abstract

According to the tube seat clamping device capable of accurately simulating the mechanical boundary of the reactor fuel assembly, the fuel assembly comprises an assembly upper tube seat extension section, an assembly upper tube seat transition section, a sub-assembly, an assembly lower tube seat transition section and an assembly lower tube seat extension section, the upper end of the sub-assembly is connected with the assembly upper tube seat transition section, and the lower end of the sub-assembly is connected with the assembly lower tube seat transition section; the assembly upper tube seat transition section is connected with the assembly upper tube seat extension section, and the assembly lower tube seat transition section is connected with the assembly lower tube seat extension section. The upper reactor core coaming is used for fixing the assembly upper tube seat extension section and the assembly upper tube seat transition section, the lower reactor core coaming is used for fixing the assembly lower tube seat transition section and the assembly lower tube seat extension section, a displacement sensor is mounted on the assembly upper tube seat transition section, and a force sensor is arranged in the upper reactor core coaming. The influence of the upper and lower tube seat extension section structure on the fuel assembly mechanical property measurement test is effectively eliminated, and the measurement result of the fuel assembly mechanical property test is more accurate.

Description

Technical Field

[0001] This invention relates to the field of reactor fuel assembly mechanical performance testing technology, specifically to a tube holder clamping device that accurately simulates the mechanical boundaries of reactor fuel assemblies. Background Technology

[0002] With the development of nuclear reactor technology, China has also begun to develop fuel assemblies with independent intellectual property rights. The mechanical properties of fuel assemblies are important parameters in their structural design, directly affecting their integrity and safety. According to relevant nuclear safety regulations, newly designed fuel assemblies must undergo off-core mechanical property testing. The upper and lower tube supports, as important components of the fuel assembly, are mainly used for support and positioning. The structure of new fuel assemblies differs significantly from traditional pressurized water reactor fuel assemblies, resulting in significant differences in support and positioning methods. The upper and lower tube supports may be non-uniform cross-sections comprising multiple structural segments. One end connects to the upper and lower grating structures, the middle is a transition section with varying cross-sections, and the other end serves as an extension for assembly hoisting and positioning. The support and fixation of these new assemblies within the reactor mainly occurs in the middle transition section of the upper and lower tube supports. Mechanical performance testing focuses on the assembly structure between the upper and lower tube support transition sections (excluding the tube support extensions). Due to the distance between the upper and lower tube support extensions, achieving assembly clamping and positioning only in the middle transition section of the fuel assembly tube supports has been a persistent technical challenge in assembly mechanical testing. The clamping device proposed in this invention can clamp and position the intermediate transition section of the fuel assembly tube across the extension section of the tube, accurately simulate the boundary conditions of the assembly in the reactor, and realize the mechanical performance test and evaluation of the fuel assembly under different loading conditions. Summary of the Invention

[0003] The purpose of this invention is to provide a tube holder clamping device that accurately simulates the mechanical boundaries of reactor fuel assemblies, thereby meeting the requirements for off-core mechanical performance testing of fuel assemblies.

[0004] The technical solution of the present invention is as follows: a tube holder clamping device for accurately simulating the mechanical boundary of a reactor fuel assembly, wherein the fuel assembly includes an upper tube holder extension section, an upper tube holder transition section, a sub-assembly, a lower tube holder transition section, and a lower tube holder extension section, wherein the upper end of the sub-assembly is connected to the upper tube holder transition section, and the lower end is connected to the lower tube holder transition section; the upper tube holder transition section is connected to the upper tube holder extension section, and the lower tube holder transition section is connected to the lower tube holder extension section; the invention is characterized by including an upper core shroud and a lower core shroud; the upper core shroud fixes the upper tube holder extension section and the upper tube holder transition section, while the lower core shroud fixes the lower tube holder transition section and the lower tube holder extension section; a displacement sensor is installed on the upper tube holder transition section, and a force sensor is located in the upper core shroud.

[0005] The lower core enclosure includes a lower tube holder clamping sleeve and a connecting base plate. The lower tube holder clamping sleeve and the connecting base plate are connected by bolts, and the connecting base plate is connected to the test device base platform by bolts. The lower tube holder extension of the fuel assembly is inserted into the lower tube holder clamping sleeve, and the upper end of the lower tube holder clamping sleeve has a chamfer, so that the surface of the lower tube holder transition section of the assembly fits with the chamfer inside the upper end of the sleeve. The upper core enclosure includes an upper tube holder clamping sleeve and a compression cover plate. The upper tube holder clamping sleeve is connected to the compression cover plate by bolts. The upper tube holder extension 1 of the assembly is embedded in the upper tube holder clamping sleeve, and the transition surface of the upper tube holder of the assembly fits tightly with the inner surface of the lower end of the sleeve.

[0006] The pad embedded inside the lower tube holder sleeve raises the fuel assembly height.

[0007] Remove the upper core enclosure, leaving only the lower core enclosure.

[0008] A shallow groove is cut into the center of the upper surface of the compression cover plate to house the compression force sensor.

[0009] The upper tube seat clamping sleeve and the lower tube seat clamping sleeve are grooved inside.

[0010] The upper tube socket transition section of the assembly includes a transition section and a straight section. The transition section is a chamfered structure that matches the inner side of the upper core shroud, while the straight section is connected to the sub-assembly and is equipped with a displacement sensor.

[0011] The lower core enclosure includes a lower tube seat welding flange, a lower tube seat connecting sleeve, a connecting base plate, and a test device base platform. An upper flange structure is welded to the root of the lower tube seat extension section, and the lower tube seat extension section is completely embedded inside the sleeve. The welding flange is bolted to the upper end of the lower tube seat connecting sleeve, and the lower tube seat connecting sleeve is bolted to the connecting base plate. The connecting base plate and the test device base platform are bolted together. The upper core enclosure includes an upper tube seat welding flange, an upper tube seat connecting sleeve, and a connecting cover plate. An upper flange structure is welded to the root of the upper tube seat extension section, and the assembly upper tube seat extension section 1 is embedded inside the upper tube seat connecting sleeve. The welding flange is bolted to the upper tube seat connecting sleeve, and the upper end of the upper tube seat connecting sleeve is bolted to the connecting cover plate.

[0012] A groove is cut into the center of the bottom of the connecting cover plate, and a tensile force sensor or torque sensor is installed inside.

[0013] During the initial fuel assembly loading phase, the upper and lower core cladding plates are in contact with the upper tube socket transition section and the lower tube socket transition section, respectively. During fuel assembly operation, the lower end of the fuel assembly rises a certain distance; the upper core cladding plate remains in contact with the upper tube socket transition section, while the lower core cladding plate separates from the lower tube socket transition section, but still constrains the lower tube socket extension section. During fuel assembly refueling, the lower end of the fuel assembly rises a certain distance; the upper core cladding plate is removed, and the lower core cladding plate becomes in contact with the lower tube socket transition section.

[0014] The significant advantages of this invention are:

[0015] A tube holder clamping device is provided that can accurately simulate the mechanical boundary within the fuel assembly, effectively eliminating the influence of the upper and lower tube holder extension sections on the mechanical performance measurement test of the fuel assembly, resulting in more accurate mechanical performance test measurement results for the fuel assembly.

[0016] The device is easy to install and operate, has a reasonable design, a compact structure, is simple and practical, has a large tensile capacity, is easy to disassemble, can be reused, is highly versatile, has low cost, and is very convenient to use. Attached Figure Description

[0017] Appendix Figure 1a This is a schematic diagram of the initial stacking state of a fuel assembly with an irregular tube socket.

[0018] Appendix Figure 1b This is a schematic diagram of the operating status of a fuel assembly with an irregular connector.

[0019] Appendix Figure 1c This is a schematic diagram of the refueling status of a fuel assembly with an irregular tube socket.

[0020] Appendix Figure 2 A schematic diagram of the lower tube clamping device for accurately simulating the mechanical boundaries of the component during compression and bending tests is attached. Figure 3 A schematic diagram of the upper tube clamping device for accurately simulating the mechanical boundaries of the component during compression and bending tests is attached. Figure 4 A schematic diagram of the lower tube clamping device for accurately simulating the mechanical boundaries of the component during tensile and torsion tests is attached. Figure 5 This is a schematic diagram of the upper tube clamping device, which accurately simulates the mechanical boundary of the component during tensile and torsion tests.

[0021] In the diagram: 1 is the extension section of the upper tube socket of the component, 2 is the transition section of the upper tube socket of the component, 3 is the sub-component, 4 is the transition section of the lower tube socket of the component, 5 is the extension section of the lower tube socket of the component, 6 is the upper core shroud, and 7 is the lower core shroud.

[0022] 8 is the lower tube seat clamping sleeve, 9 is the connecting base plate, 10 is the test device base platform, 11 is the connecting bolt, and 12 is the connecting bolt.

[0023] 13 is the compression cover plate, 14 is the upper pipe seat clamping sleeve, and 15 is the connecting bolt A;

[0024] 16 is the lower pipe seat welding flange, 17 is the lower pipe seat connecting sleeve, and 18 is the connecting bolt B;

[0025] 19 is the connecting cover plate, 20 is the upper pipe seat connecting sleeve, 21 is the upper pipe seat welding flange, 22 is the connecting bolt C, and 23 is the connecting bolt D. Detailed Implementation

[0026] Many specific details are set forth in the following description to provide a full understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of this application; therefore, this application is not limited to the specific embodiments disclosed below.

[0027] The terminology used in one or more embodiments of this application is for the purpose of describing particular embodiments only and is not intended to limit the scope of one or more embodiments of this application. The singular forms “a,” “the,” and “the” used in one or more embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and or” used in one or more embodiments of this application refers to and includes any or all possible combinations of one or more associated listed items.

[0028] It should be understood that although the terms first, second, etc., may be used to describe various information in one or more embodiments of this application, such information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, first may also be referred to as second without departing from the scope of one or more embodiments of this application, and similarly, second may also be referred to as first.

[0029] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] Currently, newly developed fuel assemblies do not have connecting and positioning components for mechanical performance testing at the upper and lower tube sockets when they leave the factory. This necessitates the design of additional clamping devices tailored to the structure of the upper and lower tube sockets for off-core mechanical performance testing. These devices must interface with the entire testing system to obtain accurate mechanical experimental data under different loading conditions. This requires consideration of both the displacement constraint and fixing methods of the upper and lower tube sockets, and the application of test loads under different conditions. To obtain accurate assembly stiffness, critical loads, and other key mechanical performance parameters, the assembly clamping device needs to accurately simulate the mechanical boundaries of the assembly during in-core operation.

[0031] Taking a typical state of a fuel assembly in the reactor as an example, as shown in Figure 1, the fuel assembly includes an upper tube extension section 1, an upper tube transition section 2, a sub-assembly 3, a lower tube transition section 4, and a lower tube extension section 5. The upper end of the sub-assembly 3 is connected to the upper tube transition section 2, and the lower end is connected to the lower tube transition section 4. The upper tube transition section 2 is connected to the upper tube extension section 1, and the lower tube transition section 4 is connected to the lower tube extension section 5. The upper tube extension section 1 and the upper tube transition section 2 form the upper tube, and the lower tube transition section 4 and the lower tube extension section 5 form the lower tube.

[0032] Specifically, both the upper tube socket transition section 2 and the lower tube socket transition section 4 of the component have chamfers and match the inner sides of the upper core shroud 6 and the lower core shroud 7, thereby clamping the upper tube socket transition section 2 and the lower tube socket transition section 4 of the component.

[0033] Specifically, the upper tube seat transition section 2 of the component includes a transition section and a straight section. The transition section is a chamfered structure that matches the inner side of the upper core shroud 6, while the straight section is connected to the sub-component 3. A displacement sensor is installed on the straight section to record the deformation of the upper tube seat transition surface 2 under pressure.

[0034] For different states of fuel assemblies, the upper core shroud 6 and the lower core shroud 7 adopt different installation methods;

[0035] like Figure 1a As shown, when the fuel assembly is initially loaded into the reactor, the upper core shroud 6 and the lower core shroud 7 are in contact with the upper tube transition section 2 and the lower tube transition section 4 of the assembly, respectively.

[0036] like Figure 1b As shown, when the fuel assembly is in operation, the lower end of the fuel assembly rises a certain distance; the upper core shroud 6 and the upper tube transition section 2 remain in contact; while the lower core shroud 7 separates from the lower tube transition section 4, but the lower core shroud 7 still constrains the lower tube extension section 5 of the assembly.

[0037] like Figure 1c As shown, during fuel assembly refueling, the lower end of the fuel assembly rises a certain distance; the upper core shroud 6 is removed, and the lower core shroud 7 comes into contact with the lower tube socket transition section 4 of the assembly.

[0038] The fuel assembly is supported and clamped by the upper core shroud 6 and the lower core shroud 7. The support and clamping positions are located on the surface of the upper tube seat transition section 2 and the lower tube seat transition section 4 of the assembly. In the actual fuel assembly mechanical performance test, the structural mechanical characteristics of the upper tube seat transition section 2, the sub-assembly 3, and the lower tube seat transition section 4 of the assembly are measured, and the mechanical characteristics of the upper tube seat extension section 1 and the lower tube seat extension section 5 of the assembly are not considered.

[0039] To achieve the above objectives, the present invention provides a pipe clamping device that accurately simulates the mechanical boundaries of fuel assemblies.

[0040] Appendix Figure 2 The diagram shows a lower tube holder clamping device for accurately simulating the mechanical boundaries of the component during compression or bending tests. The lower core enclosure 7 includes a lower tube holder clamping sleeve 8 and a connecting base plate 9. The lower tube holder clamping sleeve 8 has a ring of bolt holes at its lower end. The number of holes needs to be determined based on the sleeve diameter to ensure that a specific number of bolts 11 can effectively stabilize the sleeve structure. During implementation, the lower tube holder clamping sleeve 8 is first connected to the connecting base plate 9 with a ring of bolts 11. The bolt holes are countersunk at the lower end of the connecting base plate 9. Then, the connecting base plate 9 is connected to the test device base platform 10 with a ring of bolts. Connect 12 to secure the lower tube seat clamping sleeve 8. Then, insert the lower tube seat extension 5 of the fuel assembly into the lower tube seat clamping sleeve 8. The upper end of the lower tube seat clamping sleeve 8 has a chamfer, which makes the surface of the lower tube seat transition section 4 of the assembly fit tightly with the chamfer inside the upper end of the sleeve 8. The lower tube seat extension 5 of the assembly is completely embedded in the sleeve 8. In this way, the lower tube seat clamping sleeve 8 provides a good surface support effect, constraining the lateral displacement and downward axial displacement of the lower tube seat transition section 4 and the lower tube seat extension 5, accurately simulating the mechanical boundary of the lower tube seat of the assembly in the reactor.

[0041] If the lifting of the component in other states is taken into account, a pad with a specific lifting height needs to be embedded inside the lower tube seat clamping sleeve 8 to ensure that the component reaches the corresponding lifting height when it is seated in the sleeve 8.

[0042] Appendix Figure 3 The diagram shows a schematic of the upper tube holder clamping device for accurately simulating the mechanical boundary of the assembly during compression or bending tests. The upper core shroud 6 includes an upper tube holder clamping sleeve 14 and a compression cover plate 13. The upper tube holder clamping sleeve 14 has a ring of threaded holes at its upper end. The number of holes needs to be determined according to the sleeve diameter to ensure that a specific number of bolts 15 can effectively stabilize the sleeve structure. During implementation, the upper tube holder clamping sleeve 14 is first inserted into the upper tube holder of the fuel assembly, so that the transition surface 2 of the upper tube holder is tightly fitted with the inner surface of the lower end of the sleeve 14, and the extension section 1 of the upper tube holder of the assembly can be completely embedded inside the sleeve 14. Then, the compression cover plate 13 is attached to the upper tube holder. The upper end of the tube seat clamping sleeve 14 is connected by a ring of bolts 15. A shallow groove is opened in the center of the upper surface of the compression cover plate 13, which is just right to place the disc-shaped compression force sensor. This can effectively prevent the compression force sensor from slipping laterally. The upper end of the compression force sensor is then connected to the axial actuator on the crossbeam of the test device. By applying axial displacement through the axial actuator, the compression force can be transmitted to the upper tube seat clamping sleeve 14. The lower end of the upper tube seat clamping sleeve 14 has a chamfer and fits with the upper tube seat transition section 2. The axial compression load is applied to the upper tube seat transition section 2 through the fitting surface, which accurately simulates the mechanical boundary of the upper tube seat of the component in the stack.

[0043] Considering the possible limiting pins in the upper tube seat extension section 1 and the lower tube seat extension section 5 of the component, the upper tube seat clamping sleeve 14 and the lower tube seat clamping sleeve 8 need to be slotted inside so that the pins can be well embedded. The slotting depth needs to be greater than the distance between the pin and the root of the tube seat extension section.

[0044] During the compression test, pressure is applied vertically downward from above the compression cover plate 13 and transmitted to the upper tube seat transition surface 2 through the upper tube seat clamping sleeve 14. The deformation of the upper tube seat transition surface 2 under pressure is recorded by the displacement sensor installed on the straight section of the upper tube seat transition surface 2, and the pressure value is recorded by the compression force sensor on the compression cover plate 13.

[0045] During the bending test, a force is applied to the horizontal direction of the sub-assembly 3, and the deformation of the upper tube seat transition surface 2 under bending is recorded by the displacement sensor installed on the sub-assembly 3 in both the fuel assembly operation state and the fuel assembly refueling state.

[0046] During compression and bending tests, it is necessary to constrain the lateral and downward axial displacement of the lower tube seat, while simultaneously constraining the lateral displacement of the upper tube seat. An axial load is applied to the assembly from the upper tube seat, with the constraint and load applied at the conical surface of the transition section between the upper and lower tube seats. At this point, it is not necessary to completely fix and constrain the upper and lower tube seats; instead, the lower tube seat transition section 4 is used to press against the lower tube seat sleeve 8, and the upper tube seat sleeve 14 is used to cover the upper tube seat transition section 2 for clamping and positioning. This accurately reflects the actual state of the fuel assembly within the reactor. This clamping device design has no bolted connection to the fuel assembly structure itself, only surface contact, and is completely detachable. This avoids damage to the upper and lower tube seats of the fuel assembly and accurately simulates the mechanical boundaries of the fuel assembly within the reactor, resulting in test measurement results that better match the mechanical properties of the assembly itself.

[0047] Although tensile and torsion tests do not correspond to the in-flush state of the fuel assembly, it is still necessary to measure the corresponding stiffness characteristics for assembly design verification. The extended sections of the upper and lower mounting tubes are slender, thin-walled structures with relatively low stiffness, significantly impacting the measurement of the assembly's true stiffness characteristics. Theoretically, this part of the structure should be ignored during experimental measurements. Therefore, a mounting tube clamping device was designed to accurately simulate the mechanical boundaries of the fuel assembly.

[0048] Appendix Figure 4The diagram shows a lower tube holder clamping device for accurately simulating the mechanical boundary of the assembly during tensile and torsion tests. The lower core shroud 7 includes a lower tube holder welded flange 16, a lower tube holder connecting sleeve 17, and a connecting base plate 9. In practice, the flange structure 16 is first welded to the root of the lower tube holder extension 5. Then, the lower tube holder connecting sleeve 17 is installed in a manner similar to that used in compression and bending tests. The lower tube holder connecting sleeve 17 and the test device base platform 10 are then firmly connected through the connecting base plate 9. The fuel assembly with the welded flange 16 is then hoisted and inserted into the lower tube holder connecting sleeve 17, allowing the lower tube holder extension 5 to be completely embedded inside the sleeve 17. At the same time, the welded flange 16 is connected to the upper end of the lower tube holder connecting sleeve 17 with a ring of bolts 18. This ensures that the fuel assembly lower tube holder achieves a fully free and tightly fixed clamping effect near the transition section 4, eliminating the influence of the slender lower tube holder extension 5 on the lower end constraint clamping and accurately simulating the mechanical boundary of the assembly lower tube holder within the reactor.

[0049] Appendix Figure 5 The diagram shows a schematic of the upper tube seat clamping device for accurately simulating the mechanical boundary of the assembly during tensile and torsional tests. The upper core shroud 6 includes an upper tube seat welding flange 21, an upper tube seat connecting sleeve 20, and a connecting cover plate 19. In practice, the upper flange structure 21 is first welded to the root of the upper tube seat extension section 1. Then, the welding flange 21 is connected to the upper tube seat connecting sleeve 20 by a ring of bolts 23. The upper end of the upper tube seat connecting sleeve 20 is then connected to the connecting cover plate 19 by a ring of bolts 22. The bottom center of the connecting cover plate 19 has a groove, and a tensile force sensor or torque sensor is installed inside. It is connected to the lower end of the tensile force sensor or torque sensor by a countersunk bolt. The upper end of the tensile force sensor or torque sensor is then connected to the axial actuator interface of the device. In this way, when the axial actuator applies tensile or torsional loads, the load is transmitted to the upper tube seat welding flange 21 of the assembly through the force sensor or torque sensor, eliminating the influence of the slender extension section 1 of the upper tube seat on the upper load, and accurately simulating the mechanical boundary of the upper tube seat of the assembly within the reactor.

[0050] During the tensile test, an upward tensile force is applied to the connecting cover plate 19, and the deformation of the upper tube seat transition surface 2 under tension is recorded by a displacement sensor installed on the straight section of the upper tube seat transition surface 2.

[0051] During the torsion test, a torque is applied to the connecting cover plate 19, and the deformation of the upper tube seat transition surface 2 under torque is recorded by a displacement sensor installed on the straight section of the upper tube seat transition surface 2.

[0052] Based on the design of the upper and lower tube clamping device, and in conjunction with the fuel assembly stiffness testing device, various working condition loads can be applied by axial and lateral actuators, and corresponding load and displacement measurement sensors can be arranged to carry out various mechanical performance tests of the fuel assembly and obtain accurate stiffness characteristics and critical load and other key mechanical performance parameter data.

[0053] In actual fuel assembly mechanical performance testing, the first step is to install the lower tube holder clamping device on the base platform of the device system. After installation, the fuel assembly is hoisted in and connected to the lower tube holder clamping device. Finally, the upper tube holder clamping device is installed on the upper tube holder of the fuel assembly, and force and displacement sensors are connected to it. This is then connected to the axial actuator on the upper crossbeam of the device system, achieving constraint clamping and load application of the upper and lower tube holders of the fuel assembly. In conjunction with the lateral actuator, tensile, compressive, bending, and torsional test loads can be applied to the fuel assembly, thereby obtaining key mechanical performance parameters such as stiffness and critical load. Because the upper and lower tube holder clamping device proposed in this invention accurately simulates the mechanical boundaries of the fuel assembly within the reactor, the obtained mechanical performance parameter data of the fuel assembly truly reflects the actual operating state of the assembly, and is more instructive for the verification of the mechanical design of the fuel assembly.

[0054] The above description is merely a preferred embodiment of this patent and is not intended to limit this patent. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this patent shall be included within the scope of protection of this patent.

[0055] It should be noted that, for the sake of simplicity, the foregoing method embodiments are all described as a series of actions. However, those skilled in the art should understand that this application is not limited to the described order of actions, as some steps may be performed in other orders or simultaneously according to this application. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and modules involved are not necessarily essential to this application.

[0056] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0057] The preferred embodiments disclosed above are merely illustrative of this application. The optional embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this application. These embodiments are selected and specifically described in this application to better explain the principles and practical applications of this application, thereby enabling those skilled in the art to better understand and utilize this application.

Claims

1. A tube support clamping device for accurately simulating the mechanical boundary of a reactor fuel assembly, the fuel assembly comprising an upper assembly tube extension section (1), an upper assembly tube transition section (2), a subassembly (3), a lower assembly tube transition section (4), a lower assembly tube extension section (5), wherein the upper end of the subassembly (3) is connected to the upper assembly tube transition section (2), the lower end of the subassembly (3) is connected to the lower assembly tube transition section (4), the upper assembly tube transition section (2) is connected to the upper assembly tube extension section (1), and the lower assembly tube transition section (4) is connected to the lower assembly tube extension section (5), characterized in that: The upper core shroud (6) and the lower core shroud (7) are included; the upper core shroud (6) is fixed to the upper tube support extension section (1) and the upper tube support transition section (2) of the assembly, and the lower core shroud (7) is fixed to the lower tube support transition section (4) and the lower tube support extension section (5) of the assembly; the displacement sensor is installed on the upper tube support transition section (2), and the force sensor is arranged in the upper core shroud (6).

2. A nozzle clamp apparatus for accurately modeling the mechanical boundary of a reactor fuel assembly according to claim 1, wherein: The lower core shroud (7) includes the lower tube support clamping sleeve (8) and the connecting bottom plate (9); the lower tube support clamping sleeve (8) is connected to the connecting bottom plate (9) through bolts; the connecting bottom plate (9) is connected to the test device base platform (10) through bolts; the lower tube support extension section (5) of the fuel assembly is inserted into the lower tube support clamping sleeve (8); the upper end of the lower tube support clamping sleeve (8) is internally chamfered, so that the surface of the lower tube support transition section (4) of the assembly is in close contact with the chamfered upper end of the sleeve (8); the upper core shroud (6) includes the upper tube support clamping sleeve (14) and the compression cover plate (13); the upper tube support clamping sleeve (14) is connected to the compression cover plate (13) through bolts (15); the upper tube support extension section (1) of the assembly is embedded in the upper tube support clamping sleeve (14); and the upper tube support transition surface (2) of the assembly is in close contact with the inner surface of the lower end of the sleeve (14).

3. A nozzle clamp apparatus for accurately modeling the mechanical boundary of a reactor fuel assembly according to claim 2, wherein: The embedded cushion block in the lower tube support clamping sleeve (8) allows the fuel assembly to be lifted to a certain height.

4. A collet gripping device for accurately modeling the mechanical boundary of a reactor fuel assembly according to claim 3, wherein: The upper core shroud (6) is removed, and only the lower core shroud (7) is retained.

5. A collet gripping device for accurately modeling the mechanical boundary of a reactor fuel assembly according to claim 2, wherein: A shallow groove is formed in the center of the upper surface of the compression cover plate (13) to place the compression force sensor.

6. A collet gripping device for accurately modeling the mechanical boundary of a reactor fuel assembly according to claim 2, wherein: The upper tube support clamping sleeve (14) and the lower tube support clamping sleeve (8) are internally grooved.

7. A collet gripping device for accurately modeling the mechanical boundary of a reactor fuel assembly according to claim 2, wherein: The upper tube support transition section (2) of the assembly includes a transition section and a straight cylinder section; the transition section is a chamfered structure matched with the inner side of the upper core shroud (6); the straight cylinder section is connected to the sub-assembly (3), and the displacement sensor is installed on the straight cylinder section.

8. A collet gripping device for accurately modeling the mechanical boundary of a reactor fuel assembly according to claim 1, wherein: The lower core shroud (7) includes the lower tube support welding flange (16), the lower tube support connecting sleeve (17), the connecting bottom plate (9), and the test device base platform (10); the lower tube support extension section (5) is welded to the upper flange structure (16) at the root, and is completely embedded in the sleeve (17); the welding flange (16) is connected to the upper end of the lower tube support connecting sleeve (17) through bolts; the lower tube support connecting sleeve (17) is connected to the connecting bottom plate (9) through bolts; the connecting bottom plate (9) and the test device base platform (10) are connected through bolts; the upper core shroud (6) includes the upper tube support welding flange (21), the upper tube support connecting sleeve (20), and the connecting cover plate (19); the upper tube support extension section (1) is welded to the upper flange structure (21) at the root, and is embedded in the upper tube support connecting sleeve (20); the welding flange (21) is connected to the upper tube support connecting sleeve (20) through bolts; the upper end of the upper tube support connecting sleeve (20) is connected to the connecting cover plate (19) through bolts.

9. A collet gripping device for accurately modeling the mechanical boundary of a reactor fuel assembly according to claim 8, wherein: The connecting cover plate (19) is grooved at the center of the bottom, and the tensile force sensor or the torque sensor is installed inside.

10. A tube clamp device for accurately modeling the mechanical boundary of a reactor fuel assembly according to claim 1, wherein: In the initial loading state of the fuel assembly, the upper core plate (6) and the lower core plate (7) are in contact with the upper nozzle transition section (2) and the lower nozzle transition section (4) respectively; in the running state of the fuel assembly, the lower end of the fuel assembly is lifted by a certain distance; the upper core plate (6) is still in contact with the upper nozzle transition section (2); and the lower core plate (7) is separated from the lower nozzle transition section (4), but the lower core plate (7) still restrains the lower nozzle extension section (5) of the assembly; in the refueling state of the fuel assembly, the lower end of the fuel assembly is lifted by a certain distance; the upper core plate (6) is removed, and the lower core plate (7) is in contact with the lower nozzle transition section (4) of the assembly.

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