Experimental device and experimental method for abrasion and fatigue of nuclear fuel rod and grillwork in consideration of in-reactor working conditions

Abstract

The invention provides a nuclear fuel rod and grillwork abrasion and fatigue experimental device and experimental method considering in-reactor working conditions, and belongs to the technical field of nuclear fuel grillwork experimental devices.The device is characterized in that a first clamping assembly, a vibration assembly and a second clamping assembly are installed in an experimental box; the first clamping assembly is used for clamping a grillwork, and the second clamping assembly used for clamping a fuel rod is installed on the vibration assembly and drives the fuel rod to vibrate relative to the grillwork under the driving of the vibration assembly. In the experiment process, the grillwork is heated through the heating assembly; along with the proceeding of the experiment, the grillwork expands under the influence of temperature. The experiment condition at the moment restores the environment that the grillwork is influenced by the temperature in the actual nuclear reaction process; and data obtained after the experiment is closer to a real value.

Description

Technical Field

[0001] The present invention generally relates to the technical field of nuclear fuel grid experimental devices, and in particular to an experimental device and an experimental method for the wear and fatigue of nuclear fuel rods and grids taking into account the working conditions in a reactor. Background Art

[0002] The purpose of the current wear / fatigue experiments on nuclear fuel grids is to explore the durability of the grid structure design and adjust the elastic springs of the grid according to the experimental conditions; thus, in the actual nuclear reaction process, the elastic springs have sufficient structural strength to ensure that the grid is not damaged, resulting in a nuclear accident.

[0003] In the actual nuclear reaction process, the change in the number of protons in the nucleus will cause the nucleus to produce mass loss, and the lost mass is converted into energy and then into heat. Since the grids are made of metal, they will expand and deform after absorbing heat. Since the heat released in the actual nuclear reaction process far exceeds the heat generated in the existing experiments, even if the water absorbs the heat of the grid, the grid still has a high temperature and produces obvious expansion.

[0004] The existing experimental devices for wear / fatigue tests on the elastic springs of the grid all test the wear of the elastic springs of the fuel rods and the grid in a water environment, and do not conduct the test under the actual nuclear reaction. Therefore, the heat generated during the experiment is relatively small and will be absorbed by the water, resulting in the temperature of the grid during the experiment being significantly lower than the temperature during the actual nuclear reaction.

[0005] Based on the above situation, the influence of the expansion of the frame due to temperature on the wear cannot be ignored; however, the existing experimental device ignores the influence of the expansion deformation of the frame on the wear after the temperature changes, as well as the influence of temperature on the progress coefficient of the elastic spring; this situation leads to the existing experimental method for the inaccurate estimation of the wear and fatigue of the grid elastic spring. Summary of the invention

[0006] In view of the above-mentioned defects or deficiencies in the prior art, it is desirable to provide an experimental device and an experimental method for the wear and fatigue of nuclear fuel rods and grids taking into account the in-core working conditions.

[0007] On the one hand, the present invention provides an experimental device for the wear and fatigue of nuclear fuel rods and grids considering the working conditions in the reactor, wherein the grid has a through hole, and the inner side wall of the through hole has an elastic spring; the fuel rod is inserted into the through hole and abuts against the elastic spring; The device includes: Experiment box; a first clamping assembly, the first clamping assembly being installed in the experimental box and used for clamping the grid; A vibration component, wherein the vibration component is installed in the experimental box; a second clamping assembly, the second clamping assembly being mounted on the vibration assembly and used for clamping one end of the fuel rod and driving the fuel rod to vibrate under the action of the vibration assembly; A heating assembly is mounted on the first clamping assembly and is used to heat the grid.

[0008] According to the technical solution provided by the present invention, the first clamping assembly includes: A first driving device, wherein the first driving device is installed in the experimental box, and a first abutment member is fixedly installed on the driving shaft; the first driving device is used to drive the first abutment member to extend and retract along a first direction, so that the first abutment member abuts against the side wall of the grid along the first direction; A second driving device, wherein the second driving device is installed in the experimental box and a second abutment member is fixedly installed on the driving shaft; the second driving device is used to drive the second abutment member to extend and retract along a second direction, so that the second abutment member abuts against the side wall of the grid along the second direction; A third abutment member, the third abutment member is fixedly installed in the experimental box and is used to abut against the side wall of the grid along a third direction; The first direction, the second direction and the third direction are all horizontal directions.

[0009] According to the technical solution provided by the present invention, the vibration component includes: A crankshaft assembly, one end of which is rotatably mounted on the side wall of the experimental box; the second clamping assembly is mounted on the crankshaft assembly; A transmission mechanism, which is installed in the experimental box and connected to the other end of the crankshaft assembly, and is used to drive the crankshaft assembly to rotate with a line parallel to the third direction as an axis; When the transmission mechanism drives the crankshaft assembly to rotate, the crankshaft assembly drives the second clamping assembly and the fuel rod to vibrate.

[0010] According to the technical solution provided by the present invention, the crankshaft assembly includes: A first main shaft, the first main shaft is rotatably mounted on a side wall of the experimental box, and the axis thereof is parallel to the third direction; a first shaft arm, one end of which is rotatably connected to the first main shaft with a first axis direction as an axis; the first axis direction is perpendicular to the third direction and is used to adjust the shape of the crankshaft assembly; A connecting rod shaft, one end of which is rotatably connected to the other end of the first shaft arm, and the axis of which is parallel to the direction of the first axis, and is used to adjust the shape of the crankshaft assembly; A second shaft arm, one end of which is rotatably connected to the other end of the connecting rod shaft, and the axis of which is parallel to the direction of the first axis, and is used to adjust the shape of the crankshaft assembly; A second main shaft, one end of which is rotatably connected to the other end of the second shaft arm, and the axis is parallel to the direction of the first axis, and is used to adjust the shape of the crankshaft assembly; the other end of the second main shaft is fixedly connected to the transmission mechanism; The first main shaft, the connecting rod shaft and the second main shaft are all arranged parallel to the third direction; by adjusting the shape of the crankshaft assembly, the amplitude of the crankshaft assembly when rotating is changed; A connecting piece, one end of which is rotatably mounted on the connecting rod shaft and can slide relatively along a third direction, and the other end is fixedly connected to the second clamping assembly; the extending direction of the connecting piece is perpendicular to the connecting rod shaft.

[0011] According to the technical solution provided by the present invention, the transmission mechanism includes: a first support plate, the first support plate being installed in the experimental box; A third driving device is installed on the first supporting plate, and a driving shaft is fixedly connected to the second main shaft, and is used to drive the crankshaft assembly to rotate about a line parallel to the third direction.

[0012] According to the technical solution provided by the present invention, the first support plate can be slidably installed in the experimental box along the third direction; a threaded hole is initially provided on the first support plate; The transmission mechanism also includes: A fourth driving device, the fourth driving device is installed in the experimental box; A lead screw, the lead screw is installed in the threaded hole and is arranged parallel to the third direction; one end of the lead screw is fixedly connected to the driving shaft of the fourth driving device; The fourth driving device drives the lead screw to rotate, and is used to drive the first support plate and the third driving device to move along the third direction, so as to adjust the relative positions of the first support plate, the third driving device, the second spindle and the experimental box; The shape of the crankshaft assembly is changed by adjusting the relative position of the second main shaft and the experimental box.

[0013] According to the technical solution provided by the present invention, the second clamping assembly includes: A universal shaft, one end of which is fixedly connected to the connecting member; A mechanical claw is installed at the other end of the universal shaft and is used to clamp the end of the fuel rod.

[0014] According to the technical solution provided by the present invention, the heating component includes: A conductive layer, the conductive layer is installed on a side of the third abutting member close to the grid and is electrically connected to the grounding wire, and is used to abut against and electrically connect to the grid; A conductive clip, the conductive clip being electrically connected to a positive electrode of a power source through a wire; The conductive clip is used to be clamped on the grid, electrically connected to the grid, and connect current to the grid for heating.

[0015] According to the technical solution provided by the present invention, the heating component also includes: A temperature sensor is installed in the experimental box with a detection end facing the grid and used to detect the temperature of the grid.

[0016] On the other hand, the present invention provides an experimental method for an experimental device for wear and fatigue of nuclear fuel rods and grids considering in-core working conditions, which is applied to the above-mentioned experimental device for wear and fatigue of nuclear fuel rods and grids considering in-core working conditions, comprising: The grid is arranged in the experimental box, and the first clamping assembly clamps the grid; the conductive layer of the heating assembly is electrically connected to the grid; the conductive clamp of the heating assembly is arranged on the grid; Inserting the fuel rod into the through hole of the grid so that the fuel rod abuts against the elastic spring in the through hole; Controlling the second clamping assembly to clamp one end of the fuel rod; Obtain experimental vibration frequency and experimental amplitude; The transmission mechanism drives the second main shaft in the crankshaft assembly to move to an initial position; when the second main shaft is in the initial position, the crankshaft assembly is in a straightened state; Calculate, based on the experimental amplitude, the displacement required for the second main shaft when the crankshaft assembly rotates with the experimental amplitude to obtain a first displacement; The transmission mechanism drives the second spindle to move the first displacement, so that the crankshaft assembly is in a bent state; Calculate the rotation speed of the third driving device according to the experimental vibration frequency to obtain a first rotation speed; The third driving device drives the transmission mechanism to rotate at the first speed, thereby driving the second clamping assembly and the fuel rod to vibrate at the experimental vibration frequency; The heating component heats the grid and detects the temperature of the grid to obtain a first temperature; Calculating the expansion deformation amount of the grid according to the first temperature; According to the expansion deformation amount, the first clamping assembly is controlled to adjust the clamping degree of the grid.

[0017] The beneficial effects of the present invention are: The first clamping assembly, the vibration assembly, and the second clamping assembly are installed in the experimental box; the first clamping assembly is used to clamp the grid, and the second clamping assembly for clamping the fuel rod is installed on the vibration assembly, and the fuel rod is driven to vibrate relative to the grid under the drive of the vibration assembly. During the experiment, the grid is heated by the heating assembly; as the experiment proceeds, the grid expands due to the influence of temperature. The experimental conditions at this time restore the environment in which the grid is affected by temperature during the actual nuclear reaction process; making the data obtained after the experiment closer to the true value. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings: Figure 1 It is a cross-sectional view of the experimental box; Figure 2 This is a top view of the experimental box; Figure 3 It is a schematic diagram of the structure when the first clamping assembly is not installed with a grid; Figure 4 A schematic diagram of the structure when the first clamping assembly is installed on the grid; Figure 5 is a top view of the grid; Figure 6 A top view showing the fuel rod being installed in the through hole; Figure 7 is a schematic diagram of the geometric structure of the crankshaft assembly; Figure 8 Schematic diagram of the geometric structure before and after the grid expansion; Fig. 9 A schematic diagram of the geometric structure of a grid before and after expansion in another embodiment; Among them: 1. Grid; 2. Through hole; 3. Elastic spring; 4. Fuel rod; 5. Experiment box; 10. First drive device; 11. First abutment; 12. Second drive device; 13. Second abutment; 14. Third abutment; 15. Crankshaft assembly; 16. First spindle; 17. First shaft arm; 18. Connecting rod shaft; 19. Second shaft arm; 20. Second spindle; 21. Connecting member; 22. First support plate; 23. Third drive device; 24. Fourth drive device; 25. Lead screw; 26. Universal joint; 27. Mechanical claw; 28. Conductive layer; 29. ​​Conductive clamp; 30. Temperature sensor; 31. Rotating table. DETAILED DESCRIPTION

[0019] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the relevant invention, rather than to limit the invention. It should also be noted that, for ease of description, only the parts related to the invention are shown in the accompanying drawings.

[0020] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0021] Based on the defects in the prior art mentioned in the background technology, the present invention uniquely designs the wear / fatigue test device of the grid and the fuel rod according to the temperature change, in order to reflect the influence of temperature change on the grid during the vibration of the fuel rod, and adaptively regulate the thermal expansion of the grid, including the following contents: Example 1 The present invention provides an experimental device for the wear and fatigue of nuclear fuel rods and grids taking into account the working conditions in the reactor, referring to Figure 5-6 The grid 1 has a through hole 2, and the inner wall of the through hole 2 has an elastic spring 3; the fuel rod 4 is inserted into the through hole 2 and abuts against the elastic spring 3; refer to Figure 1 , the device comprises: Experiment box 5; A first clamping assembly, which is installed in the experimental box 5 and is used to clamp the grid 1; A vibration component, the vibration component is installed in the experimental box 5; a second clamping assembly, which is mounted on the vibration assembly and is used to clamp one end of the fuel rod 4 and drive the fuel rod 4 to vibrate under the action of the vibration assembly; A heating component is installed on the first clamping component and is used to heat the grid 1.

[0022] Principle explanation: When the fuel rod 4 is inserted into the grid 1, the outer wall of the fuel rod 4 abuts against the elastic spring 3 in the through hole 2 on the grid 1. The through holes 2 of the grid 1 are all square holes. Figure 6 The distance between the two opposite side walls of the through hole 2 remains unchanged, that is, the distance between the side walls on the left and right sides and the upper and lower sides remains unchanged, and the stiffness coefficient of the elastic spring 3 installed on the side wall is also a constant value.

[0023] When the temperature of the grid 1 gradually increases, the grid 1 expands significantly, so the sidewall spacing on the opposite sides of the through hole 2 will increase synchronously with the expansion of the grid 1; at the same time, the progress coefficient of the elastic spring 3 will also change with the temperature increase. Moreover, after the temperature of the fuel rod 4 increases, the expansion of the diameter and the change in the sidewall spacing of the through hole 2 of the grid 1 are likely to be inconsistent.

[0024] Due to the above-mentioned factors that vary with temperature, when the fuel rod 4 vibrates during the nuclear reaction, the wear between the outer wall of the fuel rod 4 and the elastic spring 3 is different from the wear of vibrations of the same frequency and amplitude at normal temperature; the fatigue test process of the elastic spring 3 is also different from that at normal temperature.

[0025] Based on the above principle, the present invention designs an experimental device, and the concept includes: In the process of designing the experimental device, it is necessary to consider meeting the experimental conditions and then build the experimental environment.

[0026] For the application scenario of the present invention, the experimental conditions include how to control the relative vibration between the fuel rods and the grid; the experimental environment includes specific temperature conditions.

[0027] In this embodiment, the structural design related to controlling the relative vibration between the fuel rod 4 and the grid 1 includes: a first clamping assembly, a vibration assembly, and a second clamping assembly. The first clamping assembly and the vibration assembly are both installed in the experimental box 5, and the second clamping assembly is installed on the vibration assembly. When the first clamping assembly clamps the grid 1 and the second clamping assembly clamps the fuel rod 4, the vibration assembly vibrates, causing vibration between the fuel rod 4 and the grid 1.

[0028] The design of the temperature condition includes a heating component, which is used to heat the grid 1. The grid 1 expands during the temperature rise, and the interaction force between the grid 1 and the elastic spring 3 decreases; at the same time, the stiffness coefficient of the elastic spring 3 changes with the temperature.

[0029] Based on the above design, the solution of the present invention not only builds the experimental conditions for controlling the relative vibration of the fuel rods 4 and the grid 1, but also reflects the influence of temperature changes on the experiment through the heating component. It restores the environment in which the grid is affected by temperature during the actual nuclear reaction process, making the data obtained after the experiment closer to the real value.

[0030] The specific scheme of the present invention for the above-mentioned structural design includes: 1. Structural design of the first clamping assembly refer to Figure 2-4 , the first clamping assembly comprises: A first driving device 10, wherein the first driving device 10 is installed in the experimental box 5, and a first abutment member 11 is fixedly installed on the driving shaft; the first driving device 10 is used to drive the first abutment member 11 to extend and retract along a first direction, so that the first abutment member 11 abuts against the side wall of the grid 1 along the first direction; A second driving device 12, the second driving device 12 is rotatably mounted in the experimental box 5 with the vertical direction as the axis and a second abutment member 13 is fixedly mounted on the driving axis; the second driving device 12 is used to drive the second abutment member 13 to extend and retract along the second direction, so that the second abutment member 13 abuts against the side wall of the grid 1 along the second direction; A third abutment member 14, the third abutment member 14 is fixedly installed in the experimental box 5, and is used to abut against the side wall of the grid 1 along a third direction; The first direction, the second direction and the third direction are all horizontal directions.

[0031] Specifically, the first driving device 10 is a servo cylinder, which is used to drive the first abutment member 11 fixedly mounted on its driving shaft to move along the first direction ( Figure 2 The first abutting member 11 abuts against the side wall of the frame 1.

[0032] The second driving device 12 is a servo cylinder, which is used to drive the second abutment member 13 fixedly mounted on its driving shaft to move along the second direction ( Figure 2 The second abutting member 13 abuts against the side of the grid 1.

[0033] In some embodiments, the second driving device 12 is fixedly mounted on a rotating table 31, and the rotating table 31 can be rotatably mounted in the experimental box 5, and the rotation axis is in a vertical direction, which is used to adjust the telescopic direction of the second driving device 12 so that its telescopic direction is parallel to the diagonal of the frame 1.

[0034] The surface of the second abutment member 13 near the grid 1 has a heat-resistant soft concave-convex structure. When the grid 1 is subjected to a wear test, this structure will not be damaged by heat, and the concave-convex structure can be used to clamp the edge of the grid 1 to avoid separation due to vibration.

[0035] The third abutment 14 is fixedly installed in the experimental box 5 and is used to support the side wall of the other side of the grid 1. The direction of the supporting force is parallel to Figure 2 In the c direction.

[0036] The first direction, the second direction and the third direction are all horizontal directions; at the same time, there is an angle of 135 degrees between the first direction and the second direction (since the horizontal cross-sections of the grid 1 are all square, this method can make the extension direction of the second drive device 12 parallel to the diagonal of the grid 1), and the first direction and the third direction are perpendicular to each other. In this arrangement, only two cylinders need to be installed to clamp the grid 1, so that the grid 1 will not deviate in the horizontal direction, and the complexity of control is reduced while ensuring the stability of the clamping.

[0037] (II) Structural design of vibration components The vibration assembly includes: A crankshaft assembly 15, one end of which is rotatably mounted on the side wall of the experimental box 5; the second clamping assembly is mounted on the crankshaft assembly 15; A transmission mechanism, which is installed in the experimental box 5 and connected to the other end of the crankshaft assembly 15, and is used to drive the crankshaft assembly 15 to rotate about a line parallel to the third direction; When the transmission mechanism drives the crankshaft assembly 15 to rotate, the crankshaft assembly 15 drives the second clamping assembly and the fuel rod 4 to vibrate.

[0038] Specifically, the fuel rods 4 are connected to the crankshaft assembly 15 via the second clamping assembly, and the transmission mechanism drives the crankshaft assembly 15 to rotate, thereby driving the second clamping assembly and the fuel rods 4 to vibrate relative to the grid 1 .

[0039] Furthermore, the crankshaft assembly 15 comprises: A first main shaft 16, wherein the first main shaft 16 is rotatably mounted on a side wall of the experimental box 5, and an axis thereof is parallel to the third direction; a first shaft arm 17, one end of which is rotatably connected to the first main shaft 16 with a first axis direction as an axis; the first axis direction is perpendicular to the third direction and is used to adjust the shape of the crankshaft assembly 15; A connecting rod shaft 18, one end of which is rotatably connected to the other end of the first shaft arm 17, and the axis of which is parallel to the direction of the first axis, and is used to adjust the shape of the crankshaft assembly 15; A second shaft arm 19, one end of which is rotatably connected to the other end of the connecting rod shaft 18, and the axis of the second shaft arm 19 is parallel to the first axis direction, and is used to adjust the shape of the crankshaft assembly 15; A second main shaft 20, one end of which is rotatably connected to the other end of the second shaft arm 19, and the axis is parallel to the direction of the first axis, and is used to adjust the shape of the crankshaft assembly 15; the other end of the second main shaft 20 is fixedly connected to the transmission mechanism; The first main shaft 16, the connecting rod shaft 18 and the second main shaft 20 are all arranged parallel to the third direction; by adjusting the shape of the crankshaft assembly 15, the amplitude of the crankshaft assembly 15 when rotating is changed; A connecting member 21 , one end of which is rotatably mounted on the connecting rod shaft 18 and can slide relatively along the third direction, and the other end is fixedly connected to the second clamping assembly; the extending direction of the connecting member 21 is perpendicular to the connecting rod shaft 18 .

[0040] Specifically, in the prior art, the fuel rod is mounted on a fixture, which is mounted on a slide rail, and the fixture is controlled by a motor to move along the slide rail. In order to achieve the vibration effect of this structure, the motor needs to repeatedly rotate forward and reverse to drive the fixture to reciprocate. However, the motor needs to switch forward and reverse at least 0.2 seconds. If the fuel rod 4 is driven to move, the maximum frequency can only reach 5 Hz, which is far from the vibration frequency required for the experiment. The actual vibration frequency is between 10-100 Hz.

[0041] In order to solve the above problems, the present invention uniquely designs a crankshaft assembly 15. Among them, the first main shaft 16 and the second main shaft 20 are coaxially arranged, and the connecting rod shaft 18 is parallel to the first main shaft 16 and the second main shaft 20, and is arranged along the third direction in this embodiment. The angle between the first shaft arm 17 and the second shaft arm 19 and the third direction is adjustable. The connecting member 21 is sleeved on the connecting rod shaft 18, and the two can rotate and slide along the third direction. Therefore, the crankshaft assembly 15 has the characteristic of changeable shape, and thus has a straight state and a bent state.

[0042] In this embodiment, when the crankshaft assembly 15 is in a straight state, the first main shaft 16, the first shaft arm 17, the connecting rod shaft 18, the second shaft arm 19 and the second main shaft 20 are collinear; at this time, the distance between the first main shaft 16 and the second main shaft 20 is the largest.

[0043] When in the bent state, the second main axis 20 moves a specific displacement amount close to the first main axis 16, so that the distance between the two is reduced, and an angle is generated between the first shaft arm 17 and the second shaft arm 19 and the third direction, so that the connecting rod shaft 18 and the first main axis 16 and the second main axis 20 are offset in a direction perpendicular to the third direction, such as Figure 1 The crankshaft assembly 15 rotates in this state, and the connecting rod shaft 18 rotates around the first main shaft 16 and the second main shaft 20. Then, the second clamping assembly rotatably sleeved on the connecting rod shaft 18 will generate vibration during the rotation of the connecting rod shaft 18 around the first main shaft 16 and the second main shaft 20, and drive the fuel rod 4 to vibrate.

[0044] Specifically, when the crankshaft assembly 15 designed by the present invention is in a bent state, the more the distance between the first main shaft 16 and the second main shaft 20 is shortened, the greater the offset between the connecting rod shaft 18 and the first main shaft 16 and the second main shaft 20 in the direction perpendicular to the third direction, and the greater the amplitude of vibration when the fuel rod 4 is driven to vibrate. The greater the angular velocity of the crankshaft assembly 15 rotating around the parallel line of the third direction as the axis, the higher the frequency of vibration of the fuel rod 4.

[0045] Therefore, based on the structural design of the crankshaft assembly 15 of the present invention, the way to control the amplitude and frequency of the fuel rod 4 is: the amplitude of the fuel rod 4 is adjusted by adjusting the distance between the first main shaft 16 and the second main shaft 20, and the vibration frequency of the fuel rod 4 is adjusted by adjusting the angular velocity of the crankshaft assembly 15. For the specific control scheme, refer to the content of Example 2.

[0046] Further, the transmission mechanism includes: a structural design for adjusting the angular velocity of the crankshaft assembly 15 and a structural design for adjusting the shape of the crankshaft assembly 15; Among them, the structural design for adjusting the angular velocity of the crankshaft assembly 15 includes: A first support plate 22 and a third driving device 23; The first support plate 22 is installed in the experimental box 5; specifically, the first support plate 22 is slidably installed in the experimental box 5 along the third direction; the first support plate 22 has a threaded hole; The third driving device 23 is mounted on the first supporting plate 22 , and the driving shaft is fixedly connected to the second main shaft 20 , so as to drive the crankshaft assembly 15 to rotate about a line parallel to the third direction.

[0047] Specifically, the third driving device 23 is a motor, and its driving shaft is coaxially fixedly connected to the second main shaft 20, and is used to drive the second main shaft 20 to rotate, and then drive the crankshaft assembly 15 to rotate as a whole; the third driving device 23 is controlled to rotate at different speeds to provide different angular velocities for the crankshaft assembly 15, and finally make the fuel rod 4 produce the required vibration frequency.

[0048] Among them, the structural design for adjusting the shape of the crankshaft assembly 15 includes: A fourth driving device 24, wherein the fourth driving device 24 is installed in the experimental box 5; A lead screw 25, the lead screw 25 is installed in the threaded hole and is arranged parallel to the third direction; one end of the lead screw 25 is fixedly connected to the driving shaft of the fourth driving device 24; The fourth driving device 24 drives the lead screw 25 to rotate, and is used to drive the first support plate 22 and the third driving device 23 to move along the third direction, so as to adjust the relative positions of the first support plate 22, the third driving device 23, the second spindle 20 and the experimental box 5; By adjusting the relative position of the second main shaft 20 and the experimental box 5 , the shape of the crankshaft assembly 15 is changed.

[0049] Specifically, the fourth driving device 24 includes a servo motor and a reduction gear set (a planetary gear in this embodiment) connected to a driving shaft of the servo motor.

[0050] Since the shape of the crankshaft assembly 15 needs to be changed during the process of adjusting the amplitude of the fuel rod 4, and the smaller the amplitude, the closer the shape of the crankshaft assembly 15 is to the straightened state. This means that the angle between the first shaft arm 17 and the second shaft arm 19 and the parallel line of the third direction is smaller; and thus, the displacement of the first main shaft 16 and the second main shaft 20 from the straightened state is controlled to be smaller.

[0051] If the transmission is completed only by directly and fixedly connecting the driving shaft of the servo motor with the lead screw 25 and finally adjusting the displacement, the actual adjustment accuracy will be difficult to meet the requirements.

[0052] Therefore, in this embodiment, a reduction gear set is connected to the servo motor drive shaft to increase the angle of rotation required for the servo motor to drive the lead screw 25 to rotate a unit angle; this method can improve the transmission accuracy and ensure that the shape of the crankshaft assembly 15 after adjustment can cause the fuel rod 4 to produce a corresponding amplitude.

[0053] Based on the above structural design of the vibration assembly, the solution designed in the present invention only needs to adjust the shape of the crankshaft assembly 15, that is, correspondingly adjust the distance between the first main shaft 16 and the second main shaft 20, and control the third driving device 23 to drive the crankshaft assembly 15 to rotate at a required angular velocity, so as to drive the fuel rod 4 to generate vibrations of corresponding amplitude and frequency.

[0054] (III) Structural design of the second clamping assembly The second clamping assembly comprises: A universal shaft 26, one end of which is fixedly connected to the connecting member 21; A mechanical claw 27 is installed at the other end of the universal shaft 26 and is used to clamp the end of the fuel rod 4.

[0055] Specifically, in order to ensure that the fuel rod 4 is not damaged during the vibration process, it is necessary to make it only translate as much as possible without rotating. In the second clamping assembly of this embodiment, the mechanical claw 27 and the connecting member 21 are connected by a universal shaft 26; the universal shaft 26 is used to buffer and eliminate the force perpendicular to the extension direction of the fuel rod 4 during the vibration of the crankshaft assembly 15.

[0056] The mechanical claw 27 is of an existing structural design, and its purpose is only to use the hook-shaped structure thereon to clamp the concave and convex parts of the end of the fuel rod 4 to achieve a stable connection and avoid separation from each other during vibration.

[0057] (IV) Structural design of heating components The heating assembly includes: A conductive layer 28, which is mounted on a side of the third abutting member 14 close to the grid 1 and is electrically connected to a grounding wire, and is used to abut against and electrically connect to the grid 1; A conductive clip 29, wherein the conductive clip 29 is electrically connected to the positive electrode of the power supply through a wire; The conductive clip 29 is used to be clamped on the grid 1 and electrically connected to the grid 1 to connect current to the grid 1 for heating.

[0058] Specifically, the conductive clip 29 and the conductive layer 28 are connected to the positive pole of the power supply and the ground wire respectively. When the conductive clip 29 is clamped on the grid 1, the grid 1, as a metal, can be equivalent to a resistor in the circuit, consuming electrical energy to generate heat; thereby realizing the function of heating the grid 1.

[0059] If water is added to the experimental box 5 of this embodiment, the water will not only cause a short circuit in each device, but also absorb the temperature of the grid 1; if the grid 1 is to be heated to the required temperature, additional electric energy will be consumed, resulting in a waste of energy. Therefore, in this embodiment, no water is added to the experimental box 5, which can avoid short circuits in each device, and also avoid water absorbing the heat of the grid 1, causing the temperature of the grid 1 to drop, making it difficult to achieve the desired effect.

[0060] Furthermore, the heating component also includes: The temperature sensor 30 is installed in the experimental box 5 with a detection end facing the grid 1 and is used to detect the temperature of the grid 1 .

[0061] In this embodiment, a temperature sensor 30 is additionally installed, specifically an infrared temperature sensor.

[0062] During the experiment, detecting the temperature of the grid 1 can not only provide temperature parameter support for the analysis of data after the experiment, but also calculate the expansion deformation of the grid 1 according to the temperature of the grid 1, and then control the first clamping component to adjust the clamping degree of the grid 1. For the specific scheme, refer to Example 2.

[0063] Specifically, the motion state required for the wear test is that when the outer wall of the fuel rod 4 and the elastic spring 3 abut against each other, repeated friction is generated.

[0064] The motion state required for the fatigue test of the elastic spring 3 is: the fuel rod 4 repeatedly compresses / relaxes the elastic spring 3 .

[0065] In this embodiment, the trajectory of the movement of the second clamping assembly driven by the crankshaft assembly 15 is a circle, and the center of the circle passes through the straight line where the first main shaft 16 is located. During the movement, after being transmitted by the universal shaft 26, the fuel rod 4 can be driven to reciprocate repeatedly in the vertical direction, and at the same time, a movement mode of periodically generating a force in the first direction can be achieved.

[0066] Based on this movement mode, the fuel rod 4 is driven to slide repeatedly relative to the elastic spring 3, and the elastic spring 3 is repeatedly compressed / released; therefore, wear and fatigue experiments can be carried out simultaneously.

[0067] Example 2 The present invention provides an experimental method for an experimental device for wear and fatigue of nuclear fuel rods and grids considering the working conditions in a reactor, which is applied to an experimental device for wear and fatigue of nuclear fuel rods and grids considering the working conditions in a reactor as described in the above embodiment, comprising: Step 1: Place the grid 1 in the experimental box 5, and clamp the grid 1 with the first clamping assembly; electrically connect the conductive layer 28 of the heating assembly to the grid 1; clamp the conductive clip 29 of the heating assembly on the grid 1; Step 2: insert the fuel rod 4 into the through hole 2 of the grid 1, so that the fuel rod 4 abuts against the elastic spring 3 in the through hole 2; Step 3: Control the second clamping assembly to clamp one end of the fuel rod 4; Step 4: Obtain the experimental vibration frequency and experimental amplitude; for example, the amplitude is 0.5 mm and the frequency is 50 Hz; Step 5: The transmission mechanism drives the second main shaft 20 in the crankshaft assembly 15 to move to the initial position; when the second main shaft 20 is in the initial position, the crankshaft assembly 15 is in a straightened state; Step 6: Calculate, based on the experimental amplitude, the displacement required for the second main shaft 20 when the crankshaft assembly 15 rotates with the experimental amplitude, and obtain a first displacement; refer to Figure 7 , the first displacement is calculated by formula 1, which is: Formula 1; in, A represents the experimental amplitude, which is a known quantity, Lrepresents the distance between the two ends of the second shaft arm 19, which is a known quantity. α It represents the angle between the second shaft arm 19 and the parallel line of the third direction, which is an unknown quantity and is obtained during the calculation process. represents the first displacement, which is an unknown quantity. Thus, two equations are obtained, which have two unknown quantities and can be solved to obtain the specific value of the first displacement.

[0068] Step 7: The transmission mechanism drives the second main shaft 20 to move the first displacement, so that the crankshaft assembly 15 is in a bent state; in this embodiment, the first displacement is moved in a direction close to the fuel rod 4; Step 8: Calculate the rotation speed of the third driving device 23 according to the experimental vibration frequency to obtain the first rotation speed; the experimental vibration frequency is equal to the numerical value of the motor rotation speed per second, and when converted into the first rotation speed, it needs to be multiplied by 60; for example, when the experimental vibration frequency is 50 Hz, the motor speed needs to be controlled to 50 revolutions per second, that is, 3000RPM.

[0069] Step 9: The third driving device 23 drives the transmission mechanism to rotate at the first speed, thereby driving the second clamping assembly and the fuel rod 4 to vibrate at the experimental vibration frequency; Step 10: The heating component heats the grid 1 and detects the temperature of the grid 1 to obtain a first temperature; Step 11: Calculating the expansion deformation of the grid 1 according to the first temperature, specifically comprising: Step 11-1: Obtain the function of the expansion deformation of the metal used in the grid 1 as a function of temperature, as shown in Formula 2; Formula 2: in, represents the diagonal expansion deformation, w 1. w 2. w 3 indicates the parameter to be tested, T Indicates temperature. The specific value of the first temperature is entered during calculation; Step 11-2: Get the parameters to be tested w 1. w 2. w The specific value of 3 (obtained in advance through thermal expansion experiments and stored in the database) is substituted into the function of expansion deformation with temperature together with the first temperature to calculate the expansion deformation in the direction of the angle line. ; The thermal expansion test process includes: measuring the difference between the diagonal length of the grid 1 and the diagonal length at 0 degrees Celsius under various temperature values; fitting the parameters to be measured using the least squares method based on multiple sets of diagonal differences and multiple sets of temperature values.

[0070] Step 12: According to the expansion deformation amount, controlling the first clamping assembly to adjust the clamping degree of the grid 1.

[0071] In this embodiment, the grid 1 needs to be heated. After the grid 1 has expanded, if the first clamping assembly is still clamped according to the length of the diagonal at room temperature, the grid 1 may be damaged. Therefore, the present invention also designs a control method for automatically adjusting the clamping degree of the grid 1 by the first clamping assembly.

[0072] Since the expansion mode of the grid 1 is from the center to all directions, the present invention takes into account the expansion of the grid 1 in multiple directions, and controls the first drive device 10 and the second drive device 12 in the first clamping assembly to shrink to specific lengths respectively to adjust the clamping degree of the grid 1.

[0073] refer to Figure 8 , where the smaller square is the grid 1 at 0 degrees Celsius, and the larger square is the grid 1 after thermal expansion.

[0074] The projection point of the rotation axis of the second driving device 12 along the vertical direction is Q1; The projection point along the vertical direction of the edge of the grid 1 abutting against the second abutting member 13 before expansion is Q2; After expansion, the projection point of the edge of the grid 1 abutting against the second abutting member 13 along the vertical direction is Q3; At 0 degrees Celsius, the diagonal length of the grid 1 is D; at 0 degrees Celsius, the distance from the rotation axis of the second drive device 12 to the edge of the grid 1 abutting the second abutting member 13 is F; after thermal expansion, the distance from the rotation axis of the second drive device 12 to the edge of the grid 1 abutting the second abutting member 13 is F'; G0 represents the center point of the grid 1 at 0 degrees Celsius; G' represents the center point of the grid 1 after thermal expansion; Figure 8 The left and right arrows represent the horizontal axis of the coordinate system, and the up and down arrows represent the vertical axis of the coordinate system.

[0075] Specifically, the specific steps of adjusting the clamping degree of the grid 1 include: Step 12-1: Obtain the diagonal length D of the grid 1 at 0 degrees Celsius; obtain the distance F from the rotation axis of the second driving device 12 to the edge where the grid 1 abuts against the second abutting member 13; In this embodiment, the port of the second driving device 12 for the driving end to be extended and retracted is located on the straight line where the rotation axis is located, so F can be calculated by obtaining the extension amount of the second driving device 12 and adding the thickness of the second abutment member 13; refer to Figure 2 and Figure 8, when the temperature is 0 degrees Celsius, the line from the rotation axis of the second driving device 12 to the edge of the grid 1 abutting against the second abutting member 13 is collinear with the diagonal line of the grid 1 in the horizontal direction; Step 12-2: According to the expansion deformation , it is calculated that the first driving device 10 drives the first abutment member 11 to contract along the first direction distance; The calculation shows that the second driving device 12 drives the second abutment member 13 to contract. distance; Step 12-3: Control the first driving device 10 to drive the first abutting member 11 to contract along the first direction The grid 1 is deformed due to expansion, and still maintains contact with the first abutment member 11, and the abutment interaction force is consistent with that at 0 degrees Celsius; Control the second driving device 12 to drive the second abutment member 13 to contract Frame 1 due to expansion deformation, still maintain abutment with the second abutment member 13, the abutment interaction force is consistent with 0 degrees Celsius.

[0076] Among them, reference Figure 8 , the first direction is the up and down direction, and the third direction is the left and right direction.

[0077] Calculated The process includes: A rectangular coordinate system is established with the projection point Q1 of the rotation axis of the second driving device 12 in the vertical direction as the coordinate origin, the third direction as the horizontal axis, and the first direction as the vertical axis; Since the grid 1 is a square, and the extension direction of the second driving device 12 is collinear with the diagonal direction of the grid 1 at 0 degrees Celsius, the coordinates of the projection point Q2 of the edge of the grid 1 abutting against the second abutting member 13 before expansion along the vertical direction are obtained as follows ( , ); Since the grid 1 abuts against the third abutting member 14 along the third direction, the edge of the grid 1 abutting against the second abutting member 13 is offset away from the third abutting member 14 along the third direction. Also because the first drive device 10 contracts along the first direction The edge of the frame 1 abutting against the second abutting member 13 is offset in the first direction away from the first driving device 10. distance; Therefore, after the expansion, the coordinates of the projection point Q3 of the edge where the grid 1 abuts against the second abutting member 13 along the vertical direction are ( , ); According to the coordinates of Q1 and Q3, the distance F' between Q1 and Q3 is calculated; Equal to the difference between F and F'.

[0078] In the clamping method of this embodiment, after the grid 1 expands, it will drive the second driving device 12 and the second abutment member 13 to produce a slight rotation with the vertical direction as the axis ( Figure 8 In the figure, the expansion deformation of the grid 1 is much smaller than the diagonal length of the grid 1, so the angle generated by the slight rotation is very small. At this time, the first clamping assembly can still stably clamp the grid 1.

[0079] After the above adjustment of the clamping degree, before and after the expansion of the grid 1, its center point is shifted from point G0 to point G', the position along the first direction remains unchanged, and the distance from the third abutment member 14 along the third direction is .

[0080] During the thermal expansion process, the grid 1 drives the fuel rod 4 and the second clamping assembly to deflect along the third direction. , and finally drives the connecting member 21 to slide relative to the connecting rod shaft 18 along the third direction This method can prevent the fuel rod 4 from being offset in the vertical direction.

[0081] The control scheme of this embodiment can automatically adapt to the shape of the grid 1 after thermal expansion, and control the first clamping assembly to adjust the clamping degree accordingly to ensure that the grid 1 is not damaged; it can also prevent the portion of the fuel rod 4 inserted into the grid 1 and the portion clamped by the second clamping assembly from being offset in the vertical direction after the grid 1 expands, thereby damaging the fuel rod 4.

[0082] In some embodiments, reference Fig. 9 , the first direction is the up and down direction, and the third direction is the left and right direction.

[0083] There is a first angle between the telescopic direction of the drive shaft of the second drive device 12 and the first direction. In this embodiment, the first angle is not equal to 135 degrees. The purpose of this embodiment is to make the telescopic direction of the second drive device 12 parallel to the actual expansion direction of the edge of the frame 1 abutting against the second abutment member 13.

[0084] As the grid 1 expands before and after, the edge abutting against the second abutment member 13 deviates along the third direction. , offset along the first direction , then the angle between the actual offset direction of the edge and the first direction is equal to 90 degrees plus β degrees; According to the above situation, tanβ is equal to and The ratio is equal to 0.5, from which the angle of β can be calculated and finally the first angle is obtained.

[0085] In this case, after the grid 1 expands, the first driving device 10 also contracts along the first direction. In this case, the contraction amount of the second drive device 12 Calculated by formula 3: Formula 3; In this embodiment, after the grid 1 expands, the second driving device 12 will no longer produce a slight rotation, and compared with the previous embodiment, it has higher clamping stability.

[0086] The above description is only a preferred embodiment of the present invention and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in the present invention is not limited to the technical solution formed by a specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept. For example, the above features are replaced with the technical features with similar functions disclosed in the present invention (but not limited to) to form a technical solution.

Claims

1. An experimental device for the wear and fatigue of nuclear fuel rods and grids considering the working conditions in the reactor, characterized in that: The grid (1) has a through hole (2), and the inner side wall of the through hole (2) has an elastic spring leaf (3); a fuel rod (4) is inserted into the through hole (2) and abuts against the elastic spring leaf (3); The device includes: Experimental box (5); A first clamping assembly, the first clamping assembly being installed in the experimental box (5) and being used for clamping the grid (1); A vibration component, the vibration component is installed in the experimental box (5); a second clamping assembly, the second clamping assembly being mounted on the vibration assembly and used for clamping one end of the fuel rod (4) and, under the action of the vibration assembly, driving the fuel rod (4) to vibrate; A heating component, the heating component is mounted on the first clamping component and is used to heat the grid (1).

2. The experimental device for the wear and fatigue of nuclear fuel rods and grids considering the working conditions in the reactor according to claim 1 is characterized in that: The first clamping assembly comprises: A first driving device (10), the first driving device (10) being installed in the experimental box (5), and a first abutment member (11) being fixedly installed on the driving shaft; the first driving device (10) is used to drive the first abutment member (11) to extend and retract along a first direction, so that the first abutment member (11) abuts against a side wall of the grid (1) along the first direction; a second driving device (12), the second driving device (12) being installed in the experimental box (5) and having a second abutment member (13) fixedly installed on the driving shaft; the second driving device (12) being used to drive the second abutment member (13) to extend and retract along a second direction, so that the second abutment member (13) abuts against a side wall of the grid (1) along the second direction; A third abutment member (14), the third abutment member (14) being fixedly mounted in the experimental box (5) and being used for abutting against a side wall of the grid (1) along a third direction; The first direction, the second direction and the third direction are all horizontal directions.

3. The experimental device for the wear and fatigue of nuclear fuel rods and grids considering the in-pile working conditions according to claim 2 is characterized in that: The vibration assembly comprises: A crankshaft assembly (15), one end of the crankshaft assembly (15) being rotatably mounted on a side wall of the experimental box (5); the second clamping assembly being mounted on the crankshaft assembly (15); a transmission mechanism, the transmission mechanism being installed in the experimental box (5) and connected to the other end of the crankshaft assembly (15), and being used to drive the crankshaft assembly (15) to rotate about a line parallel to the third direction; When the transmission mechanism drives the crankshaft assembly (15) to rotate, the crankshaft assembly (15) drives the second clamping assembly and the fuel rod (4) to vibrate.

4. The experimental device for the wear and fatigue of nuclear fuel rods and grids considering the working conditions in the reactor according to claim 3 is characterized in that: The crankshaft assembly (15) comprises: A first main shaft (16), the first main shaft (16) being rotatably mounted on a side wall inside the experimental box (5), and having an axis parallel to the third direction; a first shaft arm (17), one end of the first shaft arm (17) being rotatably connected to the first main shaft (16) with a first axis direction as an axis; the first axis direction is perpendicular to the third direction and is used to adjust the shape of the crankshaft assembly (15); a connecting rod shaft (18), one end of the connecting rod shaft (18) being rotatably connected to the other end of the first shaft arm (17), and the axis of the connecting rod shaft (18) being parallel to the direction of the first axis, and being used to adjust the shape of the crankshaft assembly (15); a second shaft arm (19), one end of the second shaft arm (19) being rotatably connected to the other end of the connecting rod shaft (18), and the axis of the second shaft arm (19) being parallel to the direction of the first axis, and being used for adjusting the shape of the crankshaft assembly (15); a second main shaft (20), one end of the second main shaft (20) being rotatably connected to the other end of the second shaft arm (19), and the axis thereof being parallel to the direction of the first axis, and being used for adjusting the shape of the crankshaft assembly (15); the other end of the second main shaft (20) being fixedly connected to the transmission mechanism; The first main shaft (16), the connecting rod shaft (18) and the second main shaft (20) are all arranged parallel to the third direction; the amplitude of the crankshaft assembly (15) when rotating is changed by adjusting the shape of the crankshaft assembly (15); A connecting member (21), one end of which is rotatably mounted on the connecting rod shaft (18) and can slide relatively along a third direction, and the other end of which is fixedly connected to the second clamping assembly; the extending direction of the connecting member (21) is perpendicular to the connecting rod shaft (18).

5. The experimental device for the wear and fatigue of nuclear fuel rods and grids considering the in-pile working conditions according to claim 4 is characterized in that: The transmission mechanism comprises: A first support plate (22), the first support plate (22) being installed in the experimental box (5); A third driving device (23), the third driving device (23) being mounted on the first supporting plate (22), and the driving shaft being fixedly connected to the second main shaft (20), and being used for driving the crankshaft assembly (15) to rotate about a line parallel to the third direction as an axis.

6. The experimental device for the wear and fatigue of nuclear fuel rods and grids considering the working conditions in the reactor according to claim 5, characterized in that: The first support plate (22) is slidably mounted in the experimental box (5) along the third direction; a threaded hole is initially provided on the first support plate (22); The transmission mechanism also includes: A fourth driving device (24), the fourth driving device (24) being installed in the experimental box (5); a lead screw (25), the lead screw (25) being installed in the threaded hole and arranged parallel to the third direction; one end of the lead screw (25) being fixedly connected to a drive shaft of the fourth drive device (24); The fourth driving device (24) drives the lead screw (25) to rotate, and is used to drive the first support plate (22) and the third driving device (23) to move along a third direction, so as to adjust the relative positions of the first support plate (22), the third driving device (23), the second spindle (20), and the experimental box (5); The shape of the crankshaft assembly (15) is changed by adjusting the relative position of the second main shaft (20) and the experimental box (5).

7. The experimental device for the wear and fatigue of nuclear fuel rods and grids considering the working conditions in the reactor according to claim 4, characterized in that: The second clamping assembly comprises: A universal shaft (26), one end of the universal shaft (26) being fixedly connected to the connecting member (21); A mechanical claw (27), the mechanical claw (27) being mounted on the other end of the universal shaft (26) and being used to clamp the end of the fuel rod (4).

8. The experimental device for the wear and fatigue of nuclear fuel rods and grids considering the working conditions in the reactor according to claim 2, characterized in that: The heating assembly comprises: A conductive layer (28), the conductive layer (28) being mounted on a side of the third abutting member (14) close to the grid (1) and electrically connected to a grounding wire, and being used to abut against and electrically connect to the grid (1); A conductive clip (29), the conductive clip (29) being electrically connected to a positive electrode of a power source via a wire; The conductive clip (29) is used to be clamped on the grid (1), electrically connected to the grid (1), and to connect current to the grid (1) for heating.

9. The experimental device for the wear and fatigue of nuclear fuel rods and grids considering the working conditions in the reactor according to claim 8, characterized in that: The heating assembly also includes: A temperature sensor (30), the temperature sensor (30) being installed in the experimental box (5) with a detection end facing the grid (1) and being used to detect the temperature of the grid (1).

10. An experimental method for an experimental device for the wear and fatigue of nuclear fuel rods and grids considering the in-pile working conditions, characterized in that: An experimental device for the wear and fatigue of nuclear fuel rods and grids considering the in-core working conditions as described in claims 1 to 9, comprising: The grid (1) is arranged in the experimental box (5), and the first clamping assembly clamps the grid (1); the conductive layer (28) of the heating assembly is electrically connected to the grid (1); and the conductive clamp (29) of the heating assembly is clamped on the grid (1); Inserting a fuel rod (4) into a through hole (2) of a grid (1) so that the fuel rod (4) abuts against an elastic spring sheet (3) in the through hole (2); controlling the second clamping assembly to clamp one end of the fuel rod (4); Obtain experimental vibration frequency and experimental amplitude; The transmission mechanism drives the second main shaft (20) in the crankshaft assembly (15) to move to an initial position; when the second main shaft (20) is in the initial position, the crankshaft assembly (15) is in a straightened state; Calculating, based on the experimental amplitude, the displacement amount required for the second main shaft (20) when the crankshaft assembly (15) rotates with the experimental amplitude, thereby obtaining a first displacement; The transmission mechanism drives the second main shaft (20) to move the first displacement, so that the crankshaft assembly (15) is in a bent state; Calculating the rotation speed of the third driving device (23) according to the experimental vibration frequency to obtain a first rotation speed; The third driving device (23) drives the transmission mechanism to rotate at the first speed, thereby driving the second clamping assembly and the fuel rod (4) to vibrate at the experimental vibration frequency; The heating component heats the grid (1) and detects the temperature of the grid (1) to obtain a first temperature; calculating the expansion deformation of the grid (1) according to the first temperature; According to the amount of expansion deformation, the first clamping assembly is controlled to adjust the degree of clamping of the grid (1).

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