An underwater measuring device and method for measuring deformation of a nuclear fuel assembly

Abstract

The application discloses a device and a method for measuring deformation of a nuclear fuel assembly underwater. The device comprises an underwater measuring mechanism, a water surface driving mechanism, a control box and an upper computer. The underwater measuring mechanism comprises a rack, clamping components, supporting components and a plurality of measuring components. The rack comprises a plurality of layers of supports provided with through holes or through grooves. The supporting components are arranged at the bottom of the rack and have a supporting position and a retracted position relative to the rack. The clamping components are arranged at the upper part of the rack and have a clamping position and a releasing position relative to the rack. The plurality of measuring components are arranged on corresponding supports along the height direction of the nuclear fuel assembly to be measured. The water surface driving mechanism is connected with the underwater measuring mechanism. The control box is connected with the water surface driving mechanism and the underwater measuring mechanism. The upper computer is used for verifying deformation data of the nuclear fuel assembly to be measured through a redundancy algorithm, data fitting and three-dimensional deformation model reconstruction, obtaining and displaying the deformation amount of the nuclear fuel assembly to be measured. The application further provides a method for measuring deformation of a nuclear fuel assembly underwater.

Description

Technical Field

[0001] This invention relates to nuclear fuel assembly measurement technology, and in particular to an underwater measuring device and method for measuring the deformation of nuclear fuel assemblies in a high-level radioactive environment. Background Technology

[0002] Nuclear fuel assemblies are crucial components of nuclear power systems, consisting of fuel rods, fuel cladding, and upper and lower mounting bases. The fuel cladding encloses the fuel rods, acting as a barrier to prevent the escape of radioactive particles. Factors such as assembly stress, thermal expansion, and fuel pellet swelling can cause combined deformations in nuclear fuel assemblies, including bending, twisting, and tilting. This results in prolonged refueling windows, impacting the economic efficiency of the nuclear power plant. Severely deformed fuel assemblies are prone to scraping and breaking from other fuel assemblies during the refueling process, causing production accidents and severely affecting the refueling and unloading process, significantly extending the main overhaul timeline of the nuclear power plant.

[0003] For deformed nuclear fuel assemblies, measuring the deformation before loading allows for the acquisition of deformation data. By optimizing the loading process and the placement orientation of the fuel assemblies, loading efficiency can be improved, the main overhaul time of the nuclear power plant can be shortened, and the risk of scratch damage to the fuel assemblies can be significantly reduced. Nuclear fuel assemblies are characterized by radioactivity, large size, and high temperature; therefore, remote automatic measurement is required in boric acid water. Section 4 of the document "Post-Irradiation Inspection of Pressurized Water Reactor Rod Bundle Fuel Assemblies Part 3: Underwater Dimensional Measurement of Fuel Assemblies" (EJ / T 20150.3-2021) mentions two measurement methods: the video image comparison method and the LVDT (Linear Variable Differential Transformer) method for underwater measurement of the external dimensions of irradiated nuclear fuel assemblies.

[0004] Existing technologies employ machine vision to measure the suspension attitude and deformation of nuclear fuel assemblies. However, these technologies cannot avoid the impact of insufficient underwater light, temperature fields, and turbulence on measurement accuracy, resulting in low reliability. Other methods, to overcome the influence of environmental factors such as ambient light and thermal turbulence, use multiple laser generators to project lasers onto the surface of the fuel assembly under test. An image capture device then captures images of the laser-affected surface, thus detecting the suspension attitude of the fuel assembly. However, this requires multiple radiation-resistant laser generators and image capture devices, which are expensive and cannot avoid the impact of irregular light refraction caused by turbulence on measurement accuracy. Still other methods employ single-point contact measurement of nuclear fuel assemblies. One proposed method involves placing a lifting platform around the perimeter of the spent fuel assembly, equipped with multiple linear displacement sensors to collect deformation data from the same cross-section of the assembly. However, in underwater environments with nuclear radiation, the use of numerous moving parts and pneumatic components necessitates a complex mechanism, requiring the lifting platform to ascend and descend a full stroke for each measurement. This places high demands on the rigidity and installation accuracy of the frame, making maintenance difficult and resulting in low reliability of the measurement function. Alternatively, the platform can be moved up and down multiple times to measure gauge blocks in layers before measurement to reduce measurement errors, replacing standard nuclear fuel assemblies. However, this method is time-consuming and not suitable for rapid measurement of nuclear fuel assemblies. Furthermore, the linear displacement sensor makes point contact with the nuclear fuel assembly, making it impossible to avoid the influence of the concave shape of the assembly on the measured dimensions. Existing devices do not employ a modular design to enable rapid assembly and disassembly of modules, leading to inconvenient maintenance and long repair times.

[0005] In addition, the top of the nuclear fuel assembly is subjected to stress during the loading process, and the bottom support is subjected to stress after loading is completed. The deformation of the nuclear fuel assembly varies under different stress conditions, which affects the control of the loading and unloading process. Existing nuclear fuel assembly measuring devices cannot measure nuclear fuel assemblies under different stress conditions.

[0006] In summary, existing technologies for underwater measurement of nuclear fuel assembly deformation in high-level radioactive environments have the following problems:

[0007] Insufficient underwater light, temperature field, and turbulence affect measurement accuracy; it is difficult to measure different stress postures of nuclear fuel assemblies; maintenance of measurement devices is difficult in underwater, irradiated, and high-temperature environments; the concave shape of nuclear fuel assemblies affects measurement accuracy; measurement efficiency is low; the measurement mechanism has a complex structure and is inconvenient to maintain; and the measurement equipment is expensive. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide an underwater measuring device and method for measuring the deformation of nuclear fuel assemblies, addressing the above-mentioned deficiencies of the prior art.

[0009] To achieve the above objectives, the present invention provides an underwater measuring device for the deformation of nuclear fuel assemblies, comprising:

[0010] An underwater measuring mechanism for contact measurement of the cross-sectional deformation dimensions of a nuclear fuel assembly under test includes a frame, clamping components, a support component, and multiple measuring components. The support component is located at the bottom of the frame and has a supporting position and a retracted position relative to the frame, used for axial positioning and stress state conversion of the nuclear fuel assembly under test. The clamping component is located at the top of the frame and has a clamping position and a releasing position relative to the frame, used for radial positioning and clamping of the nuclear fuel assembly under test. Multiple measuring components are respectively arranged on corresponding frame interfaces along the height direction of the nuclear fuel assembly under test for simultaneous measurement of deformation data of the nuclear fuel assembly under test in multiple sections and directions.

[0011] At least one set of above-water drive mechanisms is connected to the underwater measuring mechanism;

[0012] The control box is connected to both the surface drive mechanism and the underwater measuring mechanism; and

[0013] The host computer is used to obtain and visually display the deformation data of the nuclear fuel assembly under test obtained by the measuring component through redundancy algorithm verification, data fitting and three-dimensional deformation model reconstruction.

[0014] The aforementioned underwater measuring device for nuclear fuel assembly deformation includes a frame with multiple layers of locating pin holes and threaded holes for quick assembly and disassembly of the measuring components.

[0015] The aforementioned underwater measuring device for nuclear fuel assembly deformation includes a measuring plate, a connector, and a displacement sensor. The displacement sensor is connected to the measuring plate via the connector. The measuring rod of the displacement sensor extends adaptively via an elastic element. The measuring plate adapts to the nuclear fuel assembly under test through a slight angular deformation along the horizontal direction to achieve contact measurement.

[0016] The aforementioned underwater measuring device for nuclear fuel assembly deformation includes a measuring component that further comprises a retraction drive and a retraction link. The retraction drive is connected to the control box via a pipeline, and the retraction link is connected to both the retraction drive and the connecting component. The retraction drive drives the retraction link to extend or retract to control the contact or separation between the measuring plate and the nuclear fuel assembly under test.

[0017] The underwater measuring device for nuclear fuel assembly deformation described above, wherein the measuring component is configured corresponding to the grid and lower tube seat of the nuclear fuel assembly to be tested, and the measuring plate is in surface contact with the grid and lower tube seat of the nuclear fuel assembly to be tested to avoid secondary deformation and the concave shape of the outer wall of the nuclear fuel assembly to be tested affecting the measurement of its external dimensions.

[0018] The aforementioned underwater measurement device for nuclear fuel assembly deformation includes a support component comprising a support plate, a support spring, a lever, a limit switch, and a fixed plate. The support plate is mounted on the support spring and its upper limit position is limited by a spring limiter. When the support plate is at its upper limit position, the preload of the support spring is less than the weight of the nuclear fuel assembly under test. The limit switch is mounted on the fixed plate and is used to detect whether the nuclear fuel assembly under test is in position. One end of the lever is connected to the surface drive mechanism, and the other end of the lever is connected to the support plate. The surface drive mechanism controls the support plate to switch between the supported position and the retracted position via the lever.

[0019] The underwater measuring device for nuclear fuel assembly deformation described above includes a clamping component comprising a positioning component and a swinging component. The positioning component is located on one side of the nuclear fuel assembly to be tested and is used to provide X-axis and Y-axis positioning references for the nuclear fuel assembly to be tested. The swinging component is located on the other side of the nuclear fuel assembly to be tested and is used to push the nuclear fuel assembly to be tested into the positioning component to achieve X-axis and Y-axis positioning.

[0020] The aforementioned underwater measuring device for nuclear fuel assembly deformation includes a positioning component comprising a positioning flap and a flipping drive component. One end of the flipping drive component is connected to the positioning flap, and the flipping drive component is connected to the control box. The control box controls the positioning flap to contact or separate from the nuclear fuel assembly under test via the flipping drive component. The swing component includes a swing rod, a connecting rod, and a torsion spring. One end of the swing rod is connected to the torsion spring, and the other end of the swing rod is connected to the surface driving mechanism via the connecting rod. The surface driving mechanism controls the swing rod to be in the clamping position or the release position via the connecting rod.

[0021] The aforementioned underwater measurement device for nuclear fuel assembly deformation includes an above-water drive mechanism comprising a drive component, a steel cable, and a guide wheel. The drive component is connected to the steel cable via a quick-release connector. The steel cable passes through the guide wheel and is connected to the underwater measurement mechanism. The guide wheel is used for long-distance guidance and / or direction change of the steel cable.

[0022] In the aforementioned underwater measurement device for nuclear fuel assembly deformation, the above-mentioned underwater drive mechanism comprises multiple sets, with each set of the drive component connected to the clamping component and the support component in a one-to-one correspondence, and the corresponding clamping component and support component being independently controlled by the drive component.

[0023] To better achieve the above objectives, the present invention also provides an underwater measurement method for the deformation of nuclear fuel assemblies, comprising the following steps:

[0024] Preliminary measurement steps: Install the underwater measurement mechanism in the underwater measurement environment, hoist the standard nuclear fuel assembly into the underwater measurement mechanism, measure the standard nuclear fuel assembly in the bottom support posture, and use the measurement data as the calibration benchmark.

[0025] The deformation data measurement process involves using a contact-type multi-section, multi-directional synchronous measurement method to measure the deformation data of the nuclear fuel assembly under test in both the bottom-supported and top-suspended states, under the control of the host computer program, and then transmitting the data to the host computer.

[0026] In the deformation acquisition step, the host computer verifies the measured deformation data using a redundancy algorithm, performs data fitting, and reconstructs a three-dimensional deformation model to obtain the deformation of the nuclear fuel assembly under test and displays it visually; and

[0027] In the measurement completion step, the measuring component and clamping component are reset, the nuclear fuel assembly to be tested is lifted away, and the measurement ends.

[0028] In the step of measuring deformation data, when measuring the deformation data of the bottom support state, the nuclear fuel assembly to be tested is hoisted into the underwater measuring mechanism and placed on the supporting component to achieve axial and radial positioning. Multiple measuring components simultaneously contact the sidewall of the nuclear fuel assembly to be tested in multiple directions at corresponding cross sections and respectively acquire the deformation data of the bottom support state of the nuclear fuel assembly to be tested.

[0029] When measuring deformation data in the top-suspended state, the supporting component descends, the top of the nuclear fuel assembly under test is subjected to force, the clamping component clamps the nuclear fuel assembly under test to achieve radial positioning and clamping, and multiple measuring components simultaneously contact the sidewall of the nuclear fuel assembly under test in multiple directions at corresponding cross sections, and respectively acquire deformation data of the top-suspended state of the nuclear fuel assembly under test.

[0030] The beneficial effects of this invention are as follows:

[0031] This invention employs contact measurement, effectively avoiding interference from environmental factors such as insufficient underwater lighting, temperature field changes, and turbulence, ensuring measurement accuracy. Through the lifting and adjusting of the support components, deformation measurement of the nuclear fuel assembly is achieved between its top-suspended and bottom-supported states. By placing the above-water drive mechanism, control box, and host computer above the water surface, radiation protection requirements are reduced, as are manufacturing, sealing, and maintenance costs. Furthermore, above-water personnel can operate and maintain the device closely, effectively reducing operational difficulty. The frame can adopt an integrated structure with lifting points and side wall mounting points, allowing the underwater device to be directly lifted out of the water for maintenance and debugging in the above-water environment, effectively reducing the difficulty of equipment manufacturing, installation, debugging, and maintenance. The measurement components adopt a modular design, with each layer of measurement components allowing for quick assembly and disassembly from the frame. Measurement components of the same model are interchangeable, and different models can be replaced to adapt to different types of nuclear fuel assemblies or to different heights of the same fuel assembly. This modular design reduces installation and maintenance requirements and improves the device's scalability. Multiple measurement components are used along the frame... The longitudinal arrangement of the nuclear fuel assembly grid at different heights avoids frequent raising and lowering of the measuring sensors during measurement, simplifying the structure of the measuring device, reducing degrees of freedom, and facilitating inspection and maintenance. The contact between the measuring plate and the nuclear fuel assembly surface overcomes the influence of single-point indentations on measurement accuracy. Synchronous operation of multi-section, multi-directional measuring sensors significantly improves measurement efficiency. The use of multi-layer sensors eliminates frequent movement mechanisms, employing a relatively simple mechanism for measurement, making maintenance simple and convenient. The displacement sensors used are less expensive than radiation-resistant lasers and video sensors, giving them a competitive edge in the market. All measuring components of the underwater measuring device can simultaneously perform a one-time, integrated measurement of a standard nuclear fuel assembly to obtain calibration data. The measurement data is compared with the calibration data to generate deformation data. This method updates the measurement benchmark simply by re-measuring the standard nuclear fuel assembly to obtain calibration data. This method transfers the measurement benchmark from the equipment to the standard nuclear fuel assembly, effectively eliminating the impact of disassembly, assembly, and maintenance of measuring components on measurement accuracy, reducing manufacturing and installation difficulties, and offering high reliability and cost advantages.

[0032] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the present invention. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the device structure according to an embodiment of the present invention;

[0034] Figure 2 This is a schematic diagram of the working state of a device according to an embodiment of the present invention;

[0035] Figure 3This is a schematic diagram of the device installation and fixing according to an embodiment of the present invention;

[0036] Figure 4 This is a block diagram showing the connection relationship of an underwater measuring device according to an embodiment of the present invention;

[0037] Figure 5 This is a schematic diagram of an underwater measurement mechanism according to an embodiment of the present invention;

[0038] Figure 6A This is a schematic diagram of the device hanging point fixing according to an embodiment of the present invention;

[0039] Figure 6B This is a schematic diagram of the installation of the measuring component according to an embodiment of the present invention;

[0040] Figure 7 This is a schematic diagram of a water-based drive mechanism according to an embodiment of the present invention;

[0041] Figure 8 This is a schematic diagram of a clamping component according to an embodiment of the present invention;

[0042] Figure 9 This is a side view of a clamping component according to an embodiment of the present invention;

[0043] Figure 10 This is a bottom view schematic diagram of a clamping component according to an embodiment of the present invention;

[0044] Figure 11 This is a schematic diagram of a support component according to an embodiment of the present invention;

[0045] Figure 12A This is a schematic diagram of the top suspension posture of a nuclear fuel assembly according to an embodiment of the present invention;

[0046] Figure 12B for Figure 12A A magnified view of a portion of the clamping component;

[0047] Figure 12C for Figure 12A Enlarged view of a portion of the supporting components;

[0048] Figure 13A This is a schematic diagram of the bottom support posture of a nuclear fuel assembly according to an embodiment of the present invention;

[0049] Figure 13B for Figure 13A A magnified view of a portion of the clamping component;

[0050] Figure 13C for Figure 13A Enlarged view of a portion of the supporting components;

[0051] Figure 14 This is a schematic diagram of the measuring component structure according to an embodiment of the present invention;

[0052] Figure 15 This is a schematic diagram of a single-sided deformation state of a nuclear fuel assembly according to an embodiment of the present invention;

[0053] Figure 16 This is a schematic diagram of a three-dimensional model reconstruction of a nuclear fuel assembly in a deformed state according to an embodiment of the present invention;

[0054] Figure 17 A schematic diagram illustrating the principle of obtaining deformation variables according to an embodiment of the present invention;

[0055] Figure 18 This is a schematic diagram illustrating the working principle of an embodiment of the present invention;

[0056] Figure 19 This is a schematic diagram of two sets of measuring components arranged vertically to measure the same cross-section, as shown in Embodiment 1 of the present invention.

[0057] Figure 20 This is a schematic diagram of three sets of measuring components arranged in a T-shape for measuring the same cross-section, as shown in Embodiment 2 of the present invention.

[0058] Figure 21 This is a schematic diagram of two sets of measuring components arranged at 60° to measure the same cross-section in Embodiment 3 of the present invention;

[0059] Figure 22 This is a schematic diagram of three sets of measuring components arranged in pairs at 60° to measure the same cross-section in Embodiment 4 of the present invention.

[0060] Among them, the attached reference numerals

[0061] 1. Underwater Measurement Mechanism

[0062] 11 racks

[0063] 111 Hook

[0064] 112 hanging point

[0065] 12 Clamping components

[0066] 121 Positioning component

[0067] 1211 Positioning Flip Panel

[0068] 1212 Flip Drive

[0069] 122 Clamping parts

[0070] 1221 Pendulum

[0071] 1222 Link

[0072] 1223 Torsion Spring

[0073] 13 Measuring components

[0074] 131 Measuring Plate

[0075] 132 Connector

[0076] 133 Displacement Sensor

[0077] 134 Retraction Drive Component

[0078] 135 Retraction Link

[0079] 14 Support components

[0080] 141 Support plate

[0081] 142 Support Spring

[0082] 143 Spring limiting component

[0083] 144 levers

[0084] 145 Support guide plate

[0085] 146 Positioning Pin

[0086] 147 Limit Switch

[0087] 148 Fixing Plate

[0088] 2 pipelines

[0089] 3. Host computer

[0090] 4. Control box

[0091] 5. Water-based drive mechanism

[0092] 51 Linear Drive Components

[0093] 52 Steel Cable

[0094] 53 Guide wheels

[0095] 6 Nuclear fuel assemblies to be tested

[0096] 61 Upper tube seat

[0097] 62 shelves

[0098] 63 Lower tube seat

[0099] 7 hooks

[0100] 8. Water surface Detailed Implementation

[0101] The structural and working principles of the present invention will be described in detail below with reference to the accompanying drawings:

[0102] See Figures 1-6B , Figure 1This is a schematic diagram of the device structure according to an embodiment of the present invention. Figure 2 This is a schematic diagram of the working state of a device according to an embodiment of the present invention. Figure 3 This is a schematic diagram of the device installation and fixing according to an embodiment of the present invention. Figure 4 This is a block diagram showing the connection relationship of an underwater measuring device according to an embodiment of the present invention. Figure 5 This is a schematic diagram of the underwater measuring mechanism 1 according to an embodiment of the present invention. Figure 6A This is a schematic diagram of the device hanging point fixing according to an embodiment of the present invention. Figure 6B This is a schematic diagram of the installation of the measurement components according to an embodiment of the present invention. The underwater measurement device for nuclear fuel assembly deformation of the present invention is suitable for underwater measurement of nuclear fuel assembly deformation in a high-level radioactive environment. It includes: an underwater measurement mechanism 1 for contact measurement of the cross-sectional deformation dimensions of the nuclear fuel assembly 6 to be tested, comprising a frame 11, a clamping component 12, multiple measuring components 13, and a supporting component 14; the nuclear fuel assembly 6 to be tested includes an upper tube seat 61, a grid frame 62, and a lower tube seat 63; the frame 11 can be a universal connecting column, connecting the clamping component 12, the supporting component 14, and the multiple measuring components 13 via a quick-connect interface; the frame 11 includes a multi-layer support, the support having through holes or slots for accommodating the nuclear fuel assembly 6 to be tested; the supporting component 14 is located at the bottom of the frame 11 and has a supporting position and a retracted position relative to the frame 11, used for axial positioning and force state conversion of the nuclear fuel assembly 6 to be tested; the clamping component 12 is located at the upper part of the frame 11, and... The device has a clamping position and a releasing position relative to the frame 11, used for radial positioning and clamping of the nuclear fuel assembly 6 to be tested; multiple measuring components 13 are respectively set on the corresponding frame interfaces along the height direction of the nuclear fuel assembly 6 to be tested, used for multi-section and multi-directional synchronous measurement of the deformation data of the nuclear fuel assembly 6 to be tested. The measuring components 13 are installed and positioned by hooks and pins, and fastened to the frame 11 by bolts. The measuring components can be quickly installed and removed by removing and installing bolts; at least one set of above-water drive mechanism 5 is connected to the underwater measuring mechanism 1; the control box 4 is used to control the movement of each drive component, and is connected to the above-water drive mechanism 5 and the underwater measuring mechanism 1 respectively; the host computer 3 is used to obtain and intuitively display the deformation data of the nuclear fuel assembly 6 to be tested obtained by the measuring components 13 through data fitting and three-dimensional deformation model reconstruction, and can be connected to the control box 4 through pipeline 2.

[0103] The underwater measuring mechanism 1 and the host computer 3 are controlled and communicated via pipeline 2, enabling long-distance measurement. The host computer 3 can process deformation data, and through data fitting and three-dimensional deformation model reconstruction, it can intuitively display the deformation of the nuclear fuel assembly. The host computer 3 has external communication capabilities and can output the deformation data of the nuclear fuel assembly. The nuclear fuel assembly cross-section measured by the measuring component 13 is located at the nuclear fuel assembly grid 62 and the lower tube seat 63. The nuclear fuel assembly grid 62 and the lower tube seat 63 are rigid, and contact measurement on them will not cause secondary deformation of the nuclear fuel assembly.

[0104] See Figure 7 , Figure 7 This is a schematic diagram of a water-based drive mechanism 5 according to an embodiment of the present invention. In this embodiment, the water-based drive mechanism 5 is installed and fixed on the ground of a nuclear power plant fuel building, providing power to the underwater measurement mechanism 1. The water-based drive mechanism 5 includes a linear drive component 51, a steel cable 52, and multiple sets of guide wheels 53. The linear drive component 51 is connected to the steel cable 52 via a quick-release connector, and the linear drive component 51 is connected to the underwater measurement mechanism 1 via the steel cable 52. The guide wheels 53 are used for long-distance guidance and / or direction change of the steel cable 52.

[0105] In this embodiment, the linear drive component 51 can be a cylinder, hydraulic cylinder, or electric motor, and the steel cable 52 can be a steel wire rope or chain. The guide wheel 53 has a long-distance guiding function for the steel cable 52, preventing mutual friction between multiple steel cables 52; the guide wheel 53 can also realize the direction change of the steel cable 52, so that the measuring component 13 can move in any direction.

[0106] See Figures 8-10 , Figure 8 This is a schematic diagram of the clamping component 12 according to an embodiment of the present invention. Figure 9 This is a side view of the clamping component 12 according to an embodiment of the present invention. Figure 10This is a bottom view of a clamping component 12 according to an embodiment of the present invention. The clamping component 12 in this embodiment includes a clamping member 122 and a positioning member 121. The positioning member 121 is located on one side of the nuclear fuel assembly 6 to be tested, and is used to provide X-axis and Y-axis positioning references for the nuclear fuel assembly 6 to be tested. The clamping member 122 is located on the other side of the nuclear fuel assembly 6 to be tested, and is used to clamp the upper tube seat 61 to achieve X-axis and Y-axis positioning of the nuclear fuel assembly 6 to be tested. Preferably, the mounting plane of the positioning member 121 is coplanar with the mounting plane of the clamping member 122 and is perpendicular to the vertical direction of the nuclear fuel assembly. The positioning component 121 includes a positioning flap 1211 and a flipping drive component 1212. One end of the flipping drive component 1212 is connected to the positioning flap 1211, and the flipping drive component 1212 is connected to the water-based drive mechanism 5 via a pipeline 2. The water-based drive mechanism 5 controls the positioning flap 1211 to contact or separate from the nuclear fuel assembly 6 under test via the flipping drive component 1212. The clamping component 122 includes a swing rod 1221, a connecting rod 1222, and a torsion spring 1223. One end of the swing rod 1221 is connected to the torsion spring 1223, and the other end of the swing rod 1221 is connected to the water-based drive mechanism 5 via the connecting rod 1222 and a steel cable 52. The water-based drive mechanism 5 controls the swing rod 1221 to be in the clamping position and the release position via the connecting rod 1222. In this process, the swing arm 1221 releases the upper tube seat 61 under the action of the torsion spring 1223; the steel cable 52 passes through the guide wheel 53 and connects to the connecting rod 1222; the water drive mechanism 5 pulls the swing arm 1221 back through the steel cable 52 and clamps the upper tube seat 61.

[0107] See Figures 11-13C , Figure 11 This is a schematic diagram of the support member 14 according to an embodiment of the present invention. Figure 12A This is a schematic diagram of the upper hoisting posture of a nuclear fuel assembly according to an embodiment of the present invention. Figure 12B for Figure 12A A magnified view of a portion of the image. Figure 12C for Figure 12A Enlarged view of a portion of the supporting components. Figure 13A This is a schematic diagram of the bottom support posture of a nuclear fuel assembly according to an embodiment of the present invention. Figure 13B for Figure 13A Enlarged view of a portion of the clamping component. Figure 13C for Figure 13AA partial enlarged view of the support component. In this embodiment, the support component 14 is located at the bottom of the frame 11 and is used to achieve axial positioning and force attitude conversion of the nuclear fuel assembly 6 under test. It includes a support plate 141, a support spring 142, a spring limiting member 143, a lever 144, a support guide plate 145, a positioning pin 146, a limit switch 147, and a fixing plate 148. The support plate 141 is mounted and supported on the support spring 142, that is, the support plate 141 is fixed around its perimeter by the support spring 142, providing vertical support and positioning for the nuclear fuel assembly 6 under test. The spring limiting member 143 is located on the fixing plate 148 and connected to the support spring 142 to limit the upper limit position of the support plate 141. When plate 141 is at its upper limit position, the preload of the support spring 142 is slightly less than the weight of the nuclear fuel assembly 6 under test. During the hoisting and positioning of the nuclear fuel assembly 6, the support plate 141 moves slightly downwards. The limit switch 147 is fixed to the fixed plate 148 and is used to detect whether the lower tube seat 63 is in position. One end of the lever 144 is connected to the steel cable 52 of the water-based drive mechanism 5, and the other end is connected to the support plate 141. The water-based drive mechanism 5 uses the steel cable 52 to retract and extend the lever 144, controlling the support plate 141 to switch between the support position and the retracted position, thus achieving the lifting and lowering control of the support plate 141. When the support plate 141 descends, it disengages from the lower tube seat 63, and the force on the nuclear fuel assembly 6 changes from being at the bottom to being at the top, completing the force posture conversion.

[0108] See Figure 14 , Figure 14This is a schematic diagram of the measuring component 13 according to an embodiment of the present invention. The measuring component 13 of this embodiment enables contact measurement of the cross-sectional deformation dimensions of nuclear fuel assemblies. It is preferably an integrated structure, facilitating overall hoisting and installation. A hanging point 112 can be provided at the rear of the frame 11 of the underwater measuring mechanism 1. It can be installed on hooks 7 on the wall below the water level 8 of the spent fuel storage pool, fuel transfer bin, or container loading well in a nuclear power plant's nuclear fuel building, or placed on the pool bottom using anchor bolts. The underwater measuring mechanism 1 can be hoisted to its working position using the hooks 111 mounted on the frame 11. After installation, the underwater measuring mechanism 1 can be calibrated using standard nuclear fuel assemblies to reduce processing and installation errors and ensure measurement accuracy. The measuring component 13 includes a measuring plate 131, a connector 132, and a displacement sensor 133. The displacement sensor 133 is connected to the measuring plate 131 via the connector 132. The measuring rod of the displacement sensor 133 extends adaptively via a built-in elastic element. The measuring plate 131 adaptively conforms to the nuclear fuel assembly 6 under test by undergoing a slight angular deformation along the horizontal direction to achieve contact measurement. Preferably, the measuring component 13 is positioned corresponding to the grid 62 and lower tube seat 63 of the nuclear fuel assembly 6 under test. The measuring plate 131 and the grid 62 and lower tube seat 63 of the nuclear fuel assembly 6 under test are in surface contact to avoid secondary deformation and to prevent the concave shape of the outer wall of the nuclear fuel assembly 6 under test from affecting the measurement of its external dimensions. The measuring plate 131 adopts a hinged or thin plate structure, which can undergo slight angular deformation in the horizontal direction under stress. This allows the measuring plate 131 to adaptively fit with the nuclear fuel assembly 6 under test, enabling contact measurement of the nuclear fuel assembly 6 under test. The deformation data is not affected by environmental factors such as insufficient underwater light, temperature field and turbulence, ensuring measurement accuracy.

[0109] In another embodiment of the present invention, the measuring component 13 may further include a retraction drive 134 and a retraction link 135. The retraction drive 134 is connected to the water-based drive mechanism 5 via a pipeline 53, and the retraction drive 134 is connected to the connector 132 via the retraction link 135. The retraction drive 134 controls the contact or separation between the measuring plate 131 and the nuclear fuel assembly 6 under test by driving the extension or retraction of the retraction link 135. In this embodiment, the built-in elastic element of the displacement sensor 133 is preferably a spring, which can realize the adaptive extension of the measuring rod. The displacement data of the displacement sensor 133 can be output remotely via the pipeline 2 to realize remote measurement of the deformation size of the nuclear fuel assembly. There can be k displacement sensors 133 in a measuring component 13, where k≥2. The displacement sensor 133 adopts a waterproof, radiation-resistant, and high-temperature-resistant structure, which is suitable for underwater, irradiated, and temperature field changing environments. It is preferably an LVDT (linear variable differential transformer), which realizes accurate measurement of displacement by converting the displacement of the measuring rod into an electrical signal. The measuring components 13 can be arranged in 3-16 layers on the frame 11, along the vertical direction, and can simultaneously measure multiple cross-sections of the nuclear fuel assembly 6 to be tested. The underwater measuring mechanism 1 can have n sets of measuring components 13 on the same measuring cross-section of the frame 11, where n≥2.

[0110] See Figure 15 and Figure 16 , Figure 15 This is a schematic diagram of a single-sided deformation state of a nuclear fuel assembly according to an embodiment of the present invention. Figure 16 This is a schematic diagram of a three-dimensional model reconstruction of a nuclear fuel assembly deformation state according to an embodiment of the present invention. The underwater measurement method for nuclear fuel assembly deformation of the present invention includes the following steps:

[0111] Preliminary measurement steps: Install underwater measurement mechanism 1 in the underwater measurement environment, hoist standard nuclear fuel assembly into underwater measurement mechanism 1, measure the standard nuclear fuel assembly in the bottom support posture, and use the measurement data as calibration reference.

[0112] The deformation data measurement process involves simultaneously measuring the deformation data of the nuclear fuel assembly 6 under test in both the bottom-supported and top-suspended states using a contact-type multi-section, multi-directional method, and transmitting the data to the host computer 3.

[0113] In the deformation acquisition step, the host computer 3 uses redundancy algorithm verification, data fitting, and three-dimensional deformation model reconstruction to obtain the deformation of the nuclear fuel assembly 6 under test and displays it visually; and

[0114] In the measurement completion step, the measuring component 13 and clamping component 12 are reset, the nuclear fuel assembly 6 to be tested is lifted off, and the measurement ends.

[0115] In the deformation data measurement step, when measuring the deformation data of the bottom support state, the nuclear fuel assembly 6 to be tested is hoisted into the underwater measuring mechanism 1 and placed on the support component 14 for axial positioning. The i-th layer of measuring components 13 simultaneously contacts the sidewall of the nuclear fuel assembly 6 to be tested in multiple directions at corresponding cross-sections. The i-th layer X-direction displacement sensor 133X i1 X i2 and the i-th layer Y-axis displacement sensor 133Y i1 Y i2 Obtain deformation data of the bottom support state of the nuclear fuel assembly 6 under test;

[0116] When measuring deformation data in the top-suspended state, the support component 14 descends, and the top of the nuclear fuel assembly 6 under test is subjected to suspension force. The clamping component 12 clamps the nuclear fuel assembly 6 under test to achieve radial positioning and clamping. The measuring components 13 of the i-th layer simultaneously contact the sidewalls of the nuclear fuel assembly 6 under test in multiple directions at corresponding cross-sections. The displacement sensor X of the i-th layer in the X direction... i1 X i2 and the Y-axis displacement sensor of the i-th layer Y i1 Y i2 Obtain deformation data of the nuclear fuel assembly 6 under test in its suspended state.

[0117] See Figure 17 and Figure 18 , Figure 17 A schematic diagram illustrating the principle of obtaining deformation variables according to an embodiment of the present invention. Figure 18 A schematic diagram illustrating the working principle of an embodiment of the present invention. The cubic spline fitting process of the present invention includes the following steps:

[0118] The process begins with inputting the raw deformation parameters collected during the deformation data measurement step. The host computer 3 receives analog detection signals from the data acquisition unit and converts them into digital signals. Subsequently, parameterization and coefficient matrix construction are used for data preprocessing. Then, data fitting is performed, and cubic spline interpolation is used to generate a smooth and continuous function curve. Finally, a complete deformation dataset is output, accurately fitting the shape of the nuclear fuel assembly grid 62 and visually displaying the stress distribution and structural state of the tested nuclear fuel assembly 6. During the deformation data acquisition and processing of the nuclear fuel assembly, a multi-displacement sensor redundant measurement and data fusion strategy is adopted. Based on the prior condition that the diagonal lengths of a square are equal, a compatibility judgment of the sensor data is established, effectively reducing noise and improving measurement accuracy, thereby ensuring reliable measurement results. Through redundancy algorithm verification, the deformation data from multiple displacement sensors are grouped and calculated independently, which not only significantly improves the accuracy and reliability of the results but also provides fault tolerance. Even if some sensor data is abnormal, reliable measurement results can still be provided through other combinations, thereby enhancing the stability of the system. Finally, by fusing and adjusting the data from multiple calculations, the actual shape of the nuclear fuel assembly grid 62 is accurately fitted. During data fitting, a smooth and continuous function curve is generated by performing cubic spline fitting on the processed data. The fitted data allows for the calculation of key deformation features such as bending and torsion of the nuclear fuel assembly. In 3D data display, a 3D engine is used to visually display the bending and torsional deformation features of the nuclear fuel assembly model in real time. Custom shaders are generated using advanced shaders and Bézier curves to achieve natural deformation effects on the model. Colors are dynamically adjusted according to the degree of deformation, making the deformation areas readily apparent and thus intuitively displaying the stress distribution and structural state of the nuclear fuel assembly 6 under test. The host computer 3 has external communication capabilities and can output deformation data of the nuclear fuel assembly 6.

[0119] Example 1

[0120] like Figure 19 As shown, when the cross-section of the nuclear fuel assembly 6 to be tested is quadrilateral, and the underwater measuring mechanism 1 includes two sets of measuring components 13 in the same measuring cross-section, the two sets of measuring components 13 are arranged in the vertical direction, and the positioning surfaces of the measuring components 13 and the clamping components 12 are in the same direction. The two sets of measuring components 13 are used to measure the deformation dimensions of two adjacent surfaces in the same cross-section of the quadrilateral nuclear fuel assembly. Based on the known side length of the cross-section of the nuclear fuel assembly 6 to be tested, the positions of the other two surfaces can be determined. Combined with the digital fitting method, the overall deformation data of the measuring cross-section can be obtained.

[0121] The working principle of the underwater measurement device for nuclear fuel assembly deformation in this embodiment is as follows:

[0122] Reference calibration: The integrated synchronous measurement standard component calibrates the measurement reference, eliminating the impact of manufacturing, installation, debugging and maintenance on measurement accuracy;

[0123] Radial positioning: The upper tube seat of the fuel assembly is used as the measurement reference point, and clamping components are used to radially position and clamp the upper tube seat;

[0124] Axial positioning: The fuel assembly is axially positioned using support components to determine the location of the measurement section;

[0125] Measurement section determination: Select N relatively uniformly distributed fuel assembly grids and lower tube seat sections at defined locations;

[0126] Deformation data acquisition: Based on the premise that the shape of each selected cross section remains unchanged, the offset and torsion of each selected cross section are measured using contact and displacement sensors that adaptively fit the nuclear fuel assembly, and the deformation data is read.

[0127] Data processing: The N+1 cross-sectional data are processed and fitted to generate cubic spline curves. The three-dimensional deformation model reconstruction technology is used to visually display the deformation structure of the fuel assembly.

[0128] The specific measurement process is as follows: The underwater measuring mechanism 1 is hoisted to a position below the water surface 8 of the spent fuel storage pool in the fuel plant, and the frame 11 is fixedly installed against the side wall of the pool; a standard nuclear fuel assembly is hoisted into the underwater measuring mechanism 1, and the standard nuclear fuel assembly is placed on the support component 14 for axial positioning; the measuring plates 131 of the two sets of measuring components 13 extend and fit against the side wall of the standard nuclear fuel assembly, and the measurement data under the bottom support posture of the standard nuclear fuel assembly is read as a calibration reference to calibrate the measurement origin of the measuring component 13; the nuclear fuel assembly 6 to be tested is hoisted into the underwater measuring mechanism 1, and the nuclear fuel assembly 6 to be tested is placed on the support component 14 for axial positioning; the measuring plates 131 of the two sets of measuring components 13 extend and fit against the side wall of the standard nuclear fuel assembly, and the measurement data is used ... nuclear fuel assembly 6 to be tested is hoisted into the underwater measuring mechanism 1, and the nuclear fuel assembly 6 to be tested is placed on the support component 14 for axial positioning; the nuclear fuel assembly 6 to be tested is hoisted into the underwater measuring mechanism 1, and the nuclear fuel assembly 6 to be tested is placed on the support component 14 for axial positioning; the nuclear fuel assembly 6 to be tested is ho The deformation data of the bottom support posture of the nuclear fuel assembly 6 under test is read from the side wall of the fuel assembly 6. The host computer 3 performs data fitting and three-dimensional deformation model reconstruction on the deformation data to intuitively display the deformation of the nuclear fuel assembly 6 under test when the bottom support posture is displayed. The support plate 141 of the support component 14 descends, the top of the nuclear fuel assembly 6 under test is subjected to force, and the clamping component 12 clamps the nuclear fuel assembly 6 under test to achieve radial positioning and clamping, and reads the deformation data of the top suspension posture of the nuclear fuel assembly 6 under test. The host computer 3 performs data fitting and three-dimensional deformation model reconstruction on the deformation data to intuitively display the deformation of the nuclear fuel assembly 6 under test when the top suspension posture is displayed. The measuring component 13 and the clamping component 12 are reset, the nuclear fuel assembly 6 under test is lifted away, and the measurement ends.

[0129] Example 2

[0130] like Figure 20As shown, when the cross-section of the nuclear fuel assembly 6 under test is quadrilateral, and the underwater measuring mechanism 1 includes three sets of measuring components 13 on the same measuring cross-section, the three sets of measuring components 13 are arranged in a T-shape. The three sets of measuring components 13 are used to measure the deformation dimensions of three surfaces on the same cross-section of the quadrilateral nuclear fuel assembly 6 under test. Based on the known side length of the cross-section of the nuclear fuel assembly 6 under test, the position of the remaining surface can be determined. Combined with the digital fitting method, the overall deformation data of the cross-section can be obtained.

[0131] The specific measurement process is as follows: The underwater measuring mechanism 1 is hoisted to a position below the water surface 8 of the spent fuel storage pool in the fuel plant, and the frame 11 is fixedly installed against the side wall of the pool; a standard nuclear fuel assembly is hoisted into the underwater measuring mechanism 1, and the standard nuclear fuel assembly is placed on the support component 14 for axial positioning; the measuring plates 131 of the two sets of measuring components 13 extend and fit against the side wall of the standard nuclear fuel assembly, and the measurement data under the bottom support state is read as a calibration reference to calibrate the measurement origin of the measuring component 13; the nuclear fuel assembly 6 to be tested is hoisted into the underwater measuring mechanism 1, and the nuclear fuel assembly 6 to be tested is placed on the support component 14 for axial positioning; the measuring plates 131 of the three sets of measuring components 13 of the nuclear fuel assembly to be tested extend and fit against the side wall of the standard nuclear fuel assembly. The deformation data of the bottom support posture of the fuel assembly 6 under test is read from the side wall of the fuel assembly 6. The host computer 3 performs data fitting and three-dimensional deformation model reconstruction on the deformation data to intuitively display the deformation of the fuel assembly 6 under test when the bottom support posture is displayed. The support plate 141 of the support component 14 descends, the top of the fuel assembly 6 under test is subjected to force, and the clamping component 12 clamps the fuel assembly 6 under test to achieve radial positioning and clamping. The deformation data of the top suspension posture of the fuel assembly 6 under test is read. The host computer 3 performs data fitting and three-dimensional deformation model reconstruction on the deformation data to intuitively display the deformation of the fuel assembly 6 under test when the top suspension posture is displayed. The measuring component 13 and the clamping component 12 are reset, the fuel assembly 6 under test is lifted away, and the measurement ends.

[0132] Example 3

[0133] like Figure 21 As shown, when the cross-section of the nuclear fuel assembly 6 to be tested is hexagonal, and the underwater measuring mechanism 1 includes two sets of measuring components 13 in the same measuring cross-section, the two sets of measuring components 13 are arranged at 60°, and the positioning surfaces of the measuring components 13 and the clamping components 12 are facing each other. The two sets of measuring components 13 are used to measure the deformation dimensions of two adjacent surfaces in the same cross-section of the hexagonal nuclear fuel assembly 6 to be tested. After three measurements, the data information of three adjacent corners of the hexagon is obtained. Based on the known side length of the cross-section of the nuclear fuel assembly 6 to be tested, the positions of the other two surfaces can be determined. Combined with the digital fitting method, the overall deformation data of the measuring cross-section can be obtained. The measurement process in this embodiment is the same as that in Embodiment 1, and will not be repeated here.

[0134] Example 4

[0135] like Figure 22 As shown, when the cross-section of the nuclear fuel assembly 6 under test is hexagonal, and the underwater measuring mechanism 1 includes three sets of measuring components 13 in the same measuring cross-section, adjacent measuring components 13 in the three sets of measuring components 13 are distributed along a 60° angle. These three sets of measuring components 13 are used to measure the deformation dimensions of three opposite surfaces in the same cross-section of the hexagonal nuclear fuel assembly 6 under test. Four angular information of the nuclear fuel assembly can be obtained through two measurements. Based on the known side length of the nuclear fuel assembly cross-section, combined with a digital fitting method, the overall deformation data of the measuring cross-section can be obtained. The measurement process in this embodiment is the same as in Embodiment 1, and will not be repeated here.

[0136] This invention is applicable to underwater measurement of nuclear fuel assembly deformation in high-level radioactive environments, solving the problems of difficulty in manual measurement of nuclear fuel assembly deformation and the risk of nuclear exposure, as well as the difficulty in guaranteeing the accuracy of deformation results by non-contact measurement. This invention employs contact measurement, effectively avoiding interference from environmental factors such as insufficient underwater lighting, temperature field changes, and turbulence, ensuring measurement accuracy. By adjusting the lifting of the support component 14, deformation measurement of the nuclear fuel assembly is achieved between its top-suspended and bottom-supported positions. By placing the power unit above the water surface 8 and arranging multiple measuring components 13, frequent lifting and lowering of the measuring sensors during measurement is avoided, simplifying the structure of the measuring device and facilitating inspection and maintenance. The contact between the measuring plate 131 and the surface of the nuclear fuel assembly overcomes the influence of single-point indentations on the measurement accuracy. The simultaneous operation of multi-section, multi-directional measuring sensors greatly improves measurement efficiency.

[0137] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the appended claims.

Claims

1. An apparatus for measuring deformation of a nuclear fuel assembly underwater, characterized by, include: An underwater measuring mechanism for contact measurement of the cross-sectional deformation dimensions of a nuclear fuel assembly under test includes a frame, clamping components, a support component, and multiple measuring components. The support component is located at the bottom of the frame and has a supporting position and a retracted position relative to the frame, used for axial positioning and stress state conversion of the nuclear fuel assembly under test. The clamping component is located at the top of the frame and has a clamping position and a releasing position relative to the frame, used for radial positioning and clamping of the nuclear fuel assembly under test. Multiple measuring components are respectively arranged on corresponding frame interfaces along the height direction of the nuclear fuel assembly under test for simultaneous measurement of deformation data of the nuclear fuel assembly under test in multiple sections and directions. At least one set of above-water drive mechanisms is connected to the underwater measuring mechanism; The control box is connected to both the surface drive mechanism and the underwater measuring mechanism; and The host computer is used to obtain and visually display the deformation data of the nuclear fuel assembly under test obtained by the measuring component through data fitting and three-dimensional deformation model reconstruction. The deformation measurement of the nuclear fuel assembly between its top-suspended and bottom-supported states is achieved through the lifting and lowering adjustment of the supporting component. The supporting component includes a supporting plate, a supporting spring, a lever, a limit switch, and a fixing plate. The supporting plate is mounted on the supporting spring and its upper limit position is limited by a spring limiter. When the supporting plate is at its upper limit position, the preload of the supporting spring is less than the weight of the nuclear fuel assembly under test. The limit switch is mounted on the fixing plate and is used to detect whether the nuclear fuel assembly under test is in position. One end of the lever is connected to the water-based drive mechanism, and the other end of the lever is connected to the supporting plate. The water-based drive mechanism controls the supporting plate to switch between the supported position and the retracted position through the lever.

2. The underwater measuring device for nuclear fuel assembly deformation as described in claim 1, characterized in that, The measuring component includes a measuring plate, a connector, and a displacement sensor. The displacement sensor is connected to the measuring plate via the connector. The measuring rod of the displacement sensor extends adaptively via an elastic element. The measuring plate adapts to the nuclear fuel assembly under test by undergoing a slight angular deformation along the horizontal direction to achieve contact measurement.

3. The underwater measuring device for nuclear fuel assembly deformation as described in claim 2, characterized in that, The measuring component also includes a retraction drive and a retraction link. The retraction drive is connected to the control box, and the retraction link is connected to the retraction drive and the connector respectively. The retraction drive drives the retraction link to extend or retract to control the contact or separation of the measuring plate with the nuclear fuel assembly under test.

4. The underwater measuring device for nuclear fuel assembly deformation as described in claim 2, characterized in that, The measuring component is set corresponding to the grid and lower tube seat of the nuclear fuel assembly under test. The measuring plate is in surface contact with the grid and lower tube seat of the nuclear fuel assembly under test to avoid secondary deformation and the concave shape of the outer wall of the nuclear fuel assembly under test affecting the measurement of its external dimensions.

5. The underwater measuring device for nuclear fuel assembly deformation as described in claim 1, characterized in that, The clamping component includes a positioning element and a swinging element. The positioning element is located on one side of the nuclear fuel assembly under test and is used to provide X-axis and Y-axis positioning references for the nuclear fuel assembly under test. The swinging element is located on the other side of the nuclear fuel assembly under test and is used to push the nuclear fuel assembly under test into the positioning element to achieve X-axis and Y-axis positioning.

6. The underwater measuring device for nuclear fuel assembly deformation as described in claim 5, characterized in that, The positioning component includes a positioning flap and a flipping drive. One end of the flipping drive is connected to the positioning flap and the flipping drive is connected to the control box. The control box controls the positioning flap to contact or separate from the nuclear fuel assembly under test through the flipping drive. The swing component includes a swing rod, a connecting rod, and a torsion spring. One end of the swing rod is connected to the torsion spring, and the other end of the swing rod is connected to the water-based drive mechanism through the connecting rod. The water-based drive mechanism controls the swing rod to be in the clamping position or the release position through the connecting rod.

7. The underwater measuring device for nuclear fuel assembly deformation as described in claim 1, characterized in that, The waterborne drive mechanism includes a drive component, a steel cable, and a guide wheel. The drive component is connected to the steel cable via a quick-release connector. The steel cable passes through the guide wheel and is connected to the underwater measurement mechanism. The guide wheel is used for long-distance guidance and / or direction change of the steel cable.

8. The underwater measuring device for nuclear fuel assembly deformation as described in claim 7, characterized in that, The water-based drive mechanism consists of multiple sets. The drive component of each set of the water-based drive mechanism is connected to the clamping component and the support component in a one-to-one correspondence, and the corresponding clamping component and support component are independently controlled by the drive component.

9. An underwater method for measuring the deformation of nuclear fuel assemblies, characterized in that, The underwater measurement device for measuring the deformation of nuclear fuel assemblies as described in any one of claims 1-8 is used, comprising the following steps: Preliminary measurement steps: Install the underwater measurement mechanism and calibrate the measurement benchmark in the underwater measurement environment; The deformation data measurement process involves simultaneously measuring the deformation data of the nuclear fuel assembly under test in both the bottom-supported and top-suspended states using a contact-type multi-section, multi-directional method, and then transmitting the data to the host computer. In the deformation acquisition step, the host computer uses data fitting and three-dimensional deformation model reconstruction to obtain the deformation of the nuclear fuel assembly under test from the measured deformation data and displays it visually; and In the measurement completion step, the measuring component and clamping component are reset, the nuclear fuel assembly to be tested is lifted away, and the measurement ends. In the step of measuring deformation data, when measuring the deformation data of the bottom support state, the nuclear fuel assembly to be tested is hoisted into the underwater measuring mechanism and placed on the supporting component to achieve axial and radial positioning. Multiple measuring components simultaneously contact the sidewall of the nuclear fuel assembly to be tested in multiple directions at corresponding cross sections and respectively acquire the deformation data of the bottom support state of the nuclear fuel assembly to be tested. When measuring deformation data in the top-suspended state, the supporting component descends, the top of the nuclear fuel assembly under test is subjected to force, the clamping component clamps the nuclear fuel assembly under test to achieve radial positioning and clamping, and multiple measuring components simultaneously contact the sidewall of the nuclear fuel assembly under test in multiple directions at corresponding cross sections, and respectively acquire deformation data of the top-suspended state of the nuclear fuel assembly under test.

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