Fuel assembly grating oxide film measuring device and measuring method thereof

Abstract

The invention discloses a fuel assembly grating oxide film measuring device and a measuring method thereof. The device comprises a driving connection unit, an axial feeding unit, a sensing positioning unit, a multi-stage attitude self-adaptive mechanism and a width self-adaptive measuring terminal. Approaching and exiting of the device are achieved through axial feeding; the multi-stage posture self-adaptive mechanism is used for doing nodding motion and swinging motion respectively, and the posture deviation of the fuel assembly in the vertical plane and the horizontal plane is compensated; and the width of the grillwork is adapted through the width self-adaptive measuring arm. Measurement can be automatically, accurately and safely completed in a high-radioactivity environment, the technical problems of strong radiation, accurate positioning, anti-collision protection and the like are effectively solved, and a reliable technical means is provided for nuclear power station fuel assembly inspection.

Description

Technical Field

[0001] This invention relates to the field of nuclear fuel detection technology, and in particular to a fuel assembly grid oxide film measuring device and its measuring method. Background Technology

[0002] In the operating environment of a nuclear reactor, an oxide film forms on the surface of the fuel assembly grid due to high-temperature, high-pressure water corrosion. The presence of this oxide film significantly increases the thermal resistance between the fuel rods and the coolant, potentially leading to abnormally high fuel rod operating temperatures and affecting the accuracy of core thermal-hydraulic calculations, thus posing a potential risk to reactor safety. Therefore, accurately measuring the growth of the oxide film on the fuel assembly grid after irradiation is a crucial step in assessing fuel assembly performance, conducting safety margin analysis, and developing new materials.

[0003] Currently, the main technical bottleneck in achieving this measurement lies in the following: the irradiated fuel assemblies possess extremely high radioactivity, making them inaccessible to personnel and prone to failure with conventional measuring equipment; simultaneously, the fuel assemblies are stored on dense storage grids or underwater testing platforms, with complex grid structures and confined grid cell spaces. How to automatically and accurately position the measuring device and enter a specific grid cell without direct human intervention, and align the probe with the surface of the grid strip to be measured, is an extremely difficult challenge. Furthermore, the measurement process requires addressing the issue of mechanical collision protection between the probe and the grid, and possessing the ability to adaptively adjust to attitude deviations caused by potential manufacturing tolerances and irradiation deformation of the fuel assembly. Existing technologies lack a dedicated device capable of achieving fully automated, high-precision, and high-reliability measurements under such special conditions. Summary of the Invention

[0004] The primary objective of this invention is to overcome the shortcomings of existing technologies and provide a fuel assembly grid oxide film measuring device and method thereof. This device can safely, reliably, and accurately achieve automated measurement of the oxide film thickness on the surface of the fuel assembly grid in a high-radioactivity environment. It can also automatically compensate for installation deviations and deformations of the fuel assembly, ensuring stable and good contact between the measuring probe and the grid surface. This provides an efficient tool for rapid in-service inspection of fuel assemblies during nuclear power plant overhauls, shortens the critical path of overhauls, and provides key data support for reactor safe operation and the development of new fuels.

[0005] Specifically, the present invention provides a fuel assembly grid oxide film measuring device, comprising: A drive connection unit for connecting to an external drive mechanism; An axial feed unit, connected to the drive connection unit, is configured to bring the measuring device closer to or further away from the grid of the fuel assembly to be measured along its axial direction (i.e., the longitudinal direction). This unit may include a support frame and a limiting buffer structure, allowing the measuring terminal to have a small, continued displacement after contacting the workpiece, thus achieving buffering and triggering a limit.

[0006] A sensing and positioning unit, disposed on the axial feed unit, includes an observation module for visual positioning. The observation module (such as a radiation-resistant camera and a light source) provides remote visual feedback to assist in initial positioning; the sensing and positioning unit may also include a limit module for limiting the maximum feed stroke, the limit module (such as a mechanical limit switch) triggering a stop signal when the device reaches the precise measurement position.

[0007] Furthermore, preferably, the limiting module is disposed on the drive connection unit or the support frame, and is used to trigger when the movement stroke of the buffer structure reaches a preset value.

[0008] A multi-stage attitude adaptive mechanism, connected to the end effector of the axial feed unit, is used to passively adjust the spatial attitude of the measuring terminal during the device's forward movement. It includes: The first-stage adjustment mechanism is configured to make the measuring terminal nod about an axis parallel to the direction of travel to accommodate the tilt of the fuel assembly in the vertical plane. The second-stage adjustment mechanism, connected to the first-stage adjustment mechanism, is configured to cause the measuring terminal to swing around an axis perpendicular to the direction of travel in order to adapt to the deflection of the fuel assembly in the horizontal plane; the two adjustment mechanisms work together to form a universal joint-type adaptive system.

[0009] A width-adaptive measurement terminal, connected to the second-stage adjustment mechanism, performs the final measurement task, solving the problem of how the probe can be smoothly introduced and stably contacted in irregular grid cells. It may include at least one laterally sliding measurement arm and a measurement probe fixed to the arm. The measurement arm is configured to open laterally under external force (such as compression of the grid strip) or retract under internal force (such as spring tension), thereby adapting to different specifications or tolerances of the operating grid width.

[0010] Preferably, both the first-stage adjustment mechanism and the second-stage adjustment mechanism are equipped with a balance adjustment component, such as a balance bracket with a knob plunger, to provide damping for the rotational motion and preset the balance position, so as to prevent the device from wobbling freely when it is not in operation.

[0011] Preferably, the measuring probe is a thickness probe based on the eddy current effect. The eddy current method has high sensitivity for measuring the thickness of conductive films (such as zirconium oxide films on zirconium alloys) on non-conductive substrates and is very suitable for operation in liquid environments, making it a preferred technology for underwater inspection of nuclear power plants.

[0012] Furthermore, the axial feed unit preferably includes a support frame fixedly connected to the drive connection unit, and a limiting buffer structure that enables the multi-stage attitude adaptive mechanism and the width adaptive measurement terminal to move axially relative to the support frame.

[0013] Furthermore, the buffer limiting mechanism preferably includes a first slide bar, a slider slidably mounted on the first slide bar, a compression spring that provides elastic preload to the slider, and a stop plate fixed to the first slide bar to limit the maximum stroke of the slider.

[0014] Furthermore, the first-stage adjustment mechanism preferably includes a first frame rotatably connected to the axial feed unit, and a first balance adjustment member for providing damping or a preset balance position for the lateral rotation of the first frame.

[0015] Furthermore, the first balance adjustment member preferably includes an adjustable elastic abutment member, the abutment end of which acts on the first frame.

[0016] Furthermore, the second-stage adjustment mechanism preferably includes a probe carrier assembly rotatably connected to the first-stage adjustment mechanism, and a second balance adjustment member for providing damping or a preset balance position for the oscillation rotation of the probe carrier assembly.

[0017] Furthermore, the width adaptive measuring terminal preferably also includes an elastic reset element connected between each measuring arm to provide a reset internal force that causes the measuring arms to retract.

[0018] Furthermore, preferably, the probe-bearing assembly is also provided with a guide element for sliding contact with the grid structure when entering the grid. As a preferred embodiment, the guide element is a longitudinal roller, but it can also be an equivalent structure capable of achieving low-friction guidance, such as a bearing, a low-friction slider, or a round-headed pin.

[0019] Furthermore, the measuring probe is preferably a thickness measuring probe based on the eddy current effect.

[0020] Furthermore, preferably, the measuring arm has at least two protruding bosses on the side facing the grid, forming a mounting position for installing and positioning the measuring probe. The height of the bosses is higher than the end face of the measuring probe. The boss structure mechanically and precisely defines the installation position of the probe, ensuring the accuracy of the measurement reference; at the same time, during the advancement and centering of the device, the bosses can contact the grid before the probe, effectively avoiding scratches and collisions to the sidewalls of the probe, playing a crucial protective role for the expensive measuring probe.

[0021] The present invention also provides a method for measuring the oxide film on a fuel assembly grid using the above-described apparatus, comprising the following steps: Remote preliminary positioning is performed using the aforementioned observation module; The axial feed unit is controlled to drive the measuring device forward. The width adaptive measurement terminal passively adapts to the grid width, and the multi-level attitude adaptive mechanism passively adjusts the contact attitude of the measurement probe. When the measuring probe contacts the grid surface and reaches a preset contact state, it stops moving forward and begins data acquisition; The external drive mechanism is controlled to drive the measuring device to retract and reset.

[0022] Compared with the prior art, the present invention has the following significant advantages: This invention, through the organic integration of the drive connection unit and the external drive system, achieves fully automated remote operation in high-radiation environments, fundamentally solving the technical challenge of personnel being unable to approach strong radiation areas for measurement. The axial feed unit enables the measuring device to accurately approach and move away from the grid under test along the axial direction, providing fundamental motion assurance for the measurement process. The observation module in the sensing and positioning unit enables remote visual positioning, providing a reliable basis for the initial alignment of the device.

[0023] In particular, the two-stage adjustment design of the multi-stage attitude adaptive mechanism compensates for the attitude deviations of the fuel assembly in the vertical and horizontal planes through nodding and swaying movements, respectively. This ensures that the measuring probe can form stable contact with the grid surface at the optimal angle, thereby guaranteeing the accuracy and reliability of the measurement data. The width-adaptive measuring terminal, through its laterally sliding measuring arm structure, achieves adaptation to grid elements of different sizes. The opening mechanism of the measuring arm under external force and the retraction mechanism under internal force ensure both the adaptability of the measurement and the smooth withdrawal of the device.

[0024] The coordinated operation of all functional units enables the entire device to operate stably in extreme environments, providing an efficient and reliable technical means for in-service inspection of nuclear power plant fuel assemblies. The precise oxide film thickness data obtained through this device is of great value in assessing fuel assembly performance and predicting their remaining lifespan, directly serving the safe operation and technological advancement of the nuclear energy industry. Attached Figure Description

[0025] Figure 1 This is a three-dimensional structural schematic diagram of an embodiment of the fuel assembly grid oxide film measuring device of the present invention; Figure 2 yes Figure 1 A schematic diagram of the three-dimensional structure from another angle; Figure 3 yes Figure 1 Another perspective on the three-dimensional structure; Figure 4 This is a schematic diagram of the measuring device of the present invention measuring the fuel assembly grid. Detailed Implementation

[0026] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0027] This invention provides a fuel assembly grid oxide film measuring device. Through an integrated measuring terminal that integrates axial feeding, visual preliminary positioning, mechanical limiting, multi-level attitude adaptation and width adaptation measurement, the device automatically completes the entire process of approaching, positioning, contacting and measuring the fuel assembly grid under the control of a remote drive system.

[0028] Specifically, the present invention provides a fuel assembly grid oxide film measuring device, such as... Figures 1-3As shown, the device includes several core components: a drive connection unit 10, an axial feed unit 20, a sensing and positioning unit 30, a multi-level attitude adaptive mechanism, and a width adaptive measurement terminal 60. The drive connection unit 10 is used to connect to an external drive mechanism. The axial feed unit 20, connected to the drive connection unit 10, is configured to move the measuring device axially towards or away from the grid of the fuel assembly to be measured. The sensing and positioning unit 30, disposed on the axial feed unit 20, includes an observation module for visual positioning. The multi-level attitude adaptive mechanism, connected to the execution end of the axial feed unit 20, includes: a first-level adjustment mechanism 40, configured to cause the measuring terminal to nod around an axis parallel to the forward direction to accommodate the tilt of the fuel assembly in the vertical plane; and a second-level adjustment mechanism 50, connected to the first-level adjustment mechanism 40, configured to cause the measuring terminal to swing around an axis perpendicular to the forward direction to accommodate the deflection of the fuel assembly in the horizontal plane. The width adaptive measurement terminal 60, connected to the second-level adjustment mechanism 50, includes at least one laterally sliding measurement arm 61 and a measurement probe 62 fixed on the measurement arm 61. The measurement arm 61 is configured to open laterally under external force or retract under internal force.

[0029] The drive connection unit 10 serves as the mounting base and force transmission interface for the entire device. It can be a high-rigidity mounting plate with standardized mechanical interfaces for quick and reliable connection to an external six-degree-of-freedom robotic arm or other forms of automated mobile platform end effectors. The design of this unit ensures that the motion of the external drive mechanism is accurately transmitted to the measuring device, while providing a stable mounting platform for other functional modules. This enables rapid docking and precise force transmission between the measuring device and the external drive system, laying the foundation for the modular design and rapid deployment of the entire measuring system.

[0030] The axial feed unit 20 is connected to the drive connection unit 10 and is configured to bring the measuring device closer to or further away from the grid of the fuel assembly to be measured along its axial direction. Further, the axial feed unit 20 is constructed to have buffering and limiting functions. The axial feed unit 20 is provided with a buffer limiting mechanism 22. The buffer limiting mechanism 22 allows for a small, controllable continued displacement of the device after the measuring terminal contacts the grid. This displacement serves both as a buffer to absorb kinetic energy and avoid rigid impact, and as a mechanical preparation to trigger the next operating command. The buffer limiting mechanism 22 can be a mechanical clearance, an elastic element, or a guide mechanism. This design allows the device to achieve flexible contact rather than rigid collision when contacting the measuring surface. On the one hand, the buffering function effectively absorbs the impact energy during the device's forward movement, preventing potential damage to the fuel assembly; on the other hand, the limiting function ensures that each measurement is performed at the same precise position, guaranteeing the consistency and repeatability of the measurement data.

[0031] In one specific embodiment, the axial feed unit 20 includes a support frame 21 fixedly connected to the drive connection unit 10, and a guide and clearance structure that allows the support frame 21 and its subsequent mechanisms to undergo limited axial sliding relative to the drive connection unit 10.

[0032] In one specific embodiment, the axial feed unit 20 includes a support frame 21 fixedly connected to the drive connection unit 10, and a buffer limiting mechanism 22 that enables the multi-stage attitude adaptive mechanism and the width adaptive measurement terminal 60 to move axially relative to the support frame 21. This allows the entire measurement terminal to generate a small elastic displacement relative to the base when the measuring probe 62 contacts the grid surface, achieving both a buffering effect and creating conditions for precise limiting.

[0033] In one specific embodiment, the buffer limiting mechanism 22 includes a first slide rod 221 disposed on the support frame 21, a slider 222 slidably mounted on the first slide rod 221, and a compression spring 223 providing elastic preload to the slider 222. The buffer limiting mechanism 22 also includes a stop plate 224 fixed to the first slide rod 221 to limit the maximum stroke of the slider. The slider 222 can move axially relative to the drive connection unit 10 to approach or move away from the grid of the fuel assembly to be tested along its axial direction. This embodiment has the advantages of simple structure and high reliability. The first slide rod 221 and the slider provide precise linear guidance, the compression spring 223 provides controllable contact pressure, and the stop plate 224 ensures the reliability of mechanical hard limiting. This purely mechanical buffer limiting scheme is particularly suitable for use in strong radiation environments, avoiding potential failures of electronic sensors.

[0034] The sensing and positioning unit 30 is mounted on the axial feed unit 20, constituting the sensory system of the device, and is used to provide remote visual feedback. It includes an observation module for visual positioning. The observation module can consist of a radiation-resistant underwater camera and an auxiliary lighting source, responsible for providing remote visual feedback in the initial measurement stage, achieving preliminary identification of the position of the grid to be measured and coarse positioning correction of the device. This realizes preliminary positioning and status monitoring before measurement, allowing operators to observe the relative positions of the device and fuel assembly in real time in a remote control room, providing visual guidance for subsequent automatic precise positioning. The sensing and positioning unit 30 may also include a limit module for limiting the maximum feed stroke. The limit module (such as a mechanical limit switch) triggers a stop signal when the device reaches the precise measurement position. As a critical safety barrier, the limit module can employ a highly reliable mechanical limit switch or a non-contact sensor, mounted on the drive connection unit 10 or the support frame 21, to limit the maximum permissible stroke of the axial feed unit 20. When the relative displacement of the buffer structure reaches the preset critical value, the limit module is triggered and immediately sends a stop signal to the control system, thereby precisely terminating the forward movement and preventing overtravel from damaging the fuel assembly.

[0035] A multi-stage attitude adaptive mechanism is connected to the execution end of the axial feed unit 20 and is the core of this invention for achieving intelligent flexible contact. The multi-stage attitude adaptive mechanism adopts a series design, containing two independent rotational degrees of freedom, together forming a passive adjustment system simulating a universal joint function. It includes a first-stage adjustment mechanism 40 and a second-stage adjustment mechanism 50. The first-stage adjustment mechanism 40 is configured to cause the measuring terminal to nod around an axis parallel to the forward direction to adapt to the tilt of the fuel assembly in the vertical plane, effectively compensating for the attitude deviation of the fuel assembly in the vertical plane and ensuring that the probe can contact the measuring surface at the correct angle. The second-stage adjustment mechanism 50 is configured to cause the measuring terminal to swing around an axis perpendicular to the forward direction to adapt to the deflection of the fuel assembly in the horizontal plane, compensating for the directional deviation of the fuel assembly in the horizontal plane and ensuring the alignment accuracy between the probe and the measuring surface. The coordinated operation of these two adjustment mechanisms allows the fixed measuring device to passively adapt to the tilt and deflection of the fuel assembly in both spatial directions. This effectively compensates for various attitude deviations that may exist in the fuel assembly, ensuring that the measuring probe 62 ultimately achieves stable and uniform contact with the grid measuring surface in the correct normal orientation. When the fuel assembly exhibits installation tilt or irradiation deformation, this mechanism can passively adjust the spatial orientation of the probe, ensuring that the probe end face always contacts the measuring surface at the optimal angle, thereby guaranteeing measurement accuracy.

[0036] In some specific embodiments, the first-stage adjustment mechanism 40 includes a first frame 41 rotatably connected to the axial feed unit 20 via a first rotating shaft 44, and a first balance adjustment member 42 for providing damping or a preset balance position for the pitch rotation of the first frame 41; the axis of the first rotating shaft 44 is parallel to the forward direction of the device, allowing the first frame 41 to rotate around the axis of the rotating shaft; this ensures both necessary movement flexibility and sufficient stability, avoiding free swaying in non-measuring states. The first balance adjustment member 42 may be a balance bracket with an adjustable knob plunger. Preferably, the first balance adjustment member 42 includes an adjustable elastic abutment member, the abutting end of which acts on the first frame 41, so that the rotation has both the necessary flexibility to adapt to attitude changes and sufficient stability to avoid unnecessary swaying.

[0037] In some specific embodiments, a guide element 43 is installed on the first-stage adjustment mechanism 40, which is mounted on the contact surface of the fuel assembly grid. The guide element 43 is a longitudinal roller, and the contact point between the measuring device and the fuel assembly grid is on the roller (excluding the probe). Because the grid is uneven, the probe needs to be adjusted up and down to a flat position on the grid surface during measurement. This ensures that the contact point between the measuring device and the fuel assembly is rolling friction rather than sliding friction, preventing scratches and snagging between the two during adjustment and protecting the fuel assembly. The guide element 43 is oriented towards the fuel assembly and can be fixed to the end of the first frame 41 of the first-stage adjustment mechanism 40 via an axle, or installed on the probe-bearing assembly 51 of the second-stage adjustment mechanism 50. The axle is perpendicular to the direction of travel of the device, allowing the roller to rotate freely around its axis. The guide element 43 is located at the end of the first frame 41 of the first-stage adjustment mechanism 40, and its rolling generatrix maintains contact with the reference upper surface of the worktable or workpiece; its position is behind the measuring probe 62, i.e., on the side closer to the operator. When fine-tuning is performed up and down via the first-stage adjustment mechanism 40, the guide element 43 acts as a rolling fulcrum, continuously contacting the working surface. This effectively suppresses the pitching or tilting tendency that may be caused by changes in the center of gravity of the mechanism, ensuring the stability and accuracy of the probe during vertical adjustment.

[0038] In some specific embodiments, the second-stage adjustment mechanism 50 includes a probe-bearing assembly 51 rotatably connected to the first-stage adjustment mechanism 40, and a second balance adjustment component for providing damping or a preset balance position for the rotation of the probe-bearing assembly 51, providing stable rotational support and ensuring the smoothness of the head-swinging motion and repeatability of the positioning accuracy. This first-stage adjustment mechanism works in conjunction with the first-stage adjustment mechanism 40 to form a complete spatial attitude adaptive system.

[0039] The probe carrier assembly 51 includes a first slider mounting bracket 511, a second slider mounting bracket 512, and a second slide bar 513 mounted between them. The second slider mounting bracket 512 is connected to the first frame 41 of the first-stage adjustment mechanism 40 via a second rotating shaft 53. The axis of the second rotating shaft 53 is perpendicular to the forward direction of the device, allowing the second slider mounting bracket 512 to swing around the axis of the rotating shaft, thereby driving the first slider mounting bracket and the width adaptive measuring terminal 60 mounted thereon to rotate. The width adaptive measuring terminal 60 is slidably sleeved on the second slide bar 513, allowing the width adaptive measuring terminal 60 to slide laterally along the second slide bar 513 to adapt to the workpiece width, and to change its horizontal orientation with the swinging motion of the second slider mounting bracket 512. The guide element 43 of the first-stage adjustment mechanism 40 can also be installed between the first slider mounting bracket 511 and the second slider mounting bracket 512. In other words, under the width-adaptive operating condition, the measuring arm 61 can independently slide laterally along the axis of the fixed second slide rod 513, thereby adjusting the lateral distance between the measuring probe and the workpiece being measured. Under the tilting adjustment condition, the second slider mounting bracket 512 is driven to rotate around the axis of the second rotating shaft. This movement forces one end of the second slide rod 513 (the end connected to the second slider mounting bracket 512) to undergo a circular motion, thereby changing the orientation of the entire second slide rod 513 in the horizontal plane. The measuring arm 61 fitted onto it also changes its horizontal angle accordingly, achieving fine adjustment of the probe's orientation. The two movements are decoupled from each other and do not interfere with each other, jointly ensuring that the measuring probe 62 can flexibly adapt to complex workpiece contours and dimensional changes.

[0040] In one specific embodiment, the second-stage adjustment mechanism 50 includes a C-shaped frame resembling a C-shape, which surrounds the second slider mounting bracket 512 from above or the side. A vertically arranged second pivot shaft passes sequentially through both arms of the C-shaped frame and the second slider mounting bracket 512 located therein, thereby rotatably suspending the second slider mounting bracket 512 within the C-shaped frame, forming a stable pivot for head movement.

[0041] In a specific embodiment, the guide element 43 of the first-stage adjustment mechanism 40 can be a longitudinal roller, which is mounted on a mounting position formed between the first slider mounting bracket 511 and the second slider mounting bracket via a wheel axle. When the device is finely adjusted up and down, it contacts the worktable surface as a stable rolling fulcrum, ensuring the smoothness of the adjustment process.

[0042] The width-adaptive measuring terminal 60, connected to the second-stage adjustment mechanism 50, includes at least one laterally sliding measuring arm 61 and a measuring probe 62 fixed to the measuring arm 61. The measuring arm 61 is configured to open laterally under external force or retract under internal force, enabling the device to adapt to different grid cell widths. When the device enters the grid, the grid strips compress the measuring arm 61, causing it to automatically open to a suitable width; when the device exits, the measuring arm 61 automatically retracts under the retraction force. This passive adaptive mechanism eliminates the need for an additional drive unit, simplifying the structure and improving reliability.

[0043] In some specific embodiments, the width adaptive measuring terminal 60 also includes an elastic reset element 63, such as a tension spring, connected between each measuring arm 61, providing a reset force to retract the measuring arms 61. This includes a sliding mechanism that guides the sliding motion and an elastic element that provides the reset internal force. The elastic reset element 63 is typically a tension spring, whose preload is precisely calculated to ensure that the measuring arms 61 can smoothly open when encountering resistance and quickly reset after the resistance disappears.

[0044] In one specific embodiment, the measuring probe 62 is a thickness probe based on the eddy current effect. Eddy current detection technology has high sensitivity for measuring the thickness of conductive film layers on non-conductive substrates and is very suitable for operation in liquid environments. It realizes non-contact or micro-contact measurement of oxide film thickness, avoiding the damage to the oxide film that may be caused by traditional contact measurement, while ensuring the accuracy and repeatability of the measurement.

[0045] As the device advances into a grid cell, the grid strips exert a lateral force on the measuring arm 61, overcoming the initial tension of the elastic reset element 63 (such as a tension spring), forcing the measuring arm 61 to slide outwards and thus adaptively pass through grid cells of different widths. When the device retracts, the external force disappears, and under the action of the internal force of the elastic reset element 63, the measuring arm 61 automatically retracts towards the center, returning to its initial state. The measuring probe 62 fixed thereon is preferably a thickness probe based on the eddy current effect, because it has high sensitivity to changes in the thickness of the zirconium oxide insulating film layer on the zirconium alloy substrate and good environmental adaptability, making it particularly suitable for underwater measurement environments.

[0046] The present invention also provides a method for measuring the oxide film on a fuel assembly grid using the above-described apparatus, comprising the following steps: Remote preliminary positioning is performed using the aforementioned observation module; The axial feed unit 20 is controlled to drive the measuring device forward. The width adaptive measurement terminal 60 passively adapts to the grid width, and the multi-level attitude adaptive mechanism passively adjusts the contact attitude of the measurement probe 62. When the measuring probe contacts the grid surface and reaches a preset contact state, it stops moving forward and begins data acquisition; =Control the external drive mechanism to drive the measuring device to retract and reset.

[0047] In one specific embodiment, see Figures 1-4 This embodiment provides a fuel assembly grid oxide film measuring device 100.

[0048] The base of the device is the drive connection unit 10, which in this embodiment is a rigid mounting plate made of radiation-resistant and high-strength materials such as stainless steel. It is equipped with a standard mechanical interface for connecting to the end flange of an external drive mechanism.

[0049] The axial feed unit 20 is connected to the drive connection unit 10 and includes a support frame 21 and a buffer limiting mechanism 22. The support frame 21 is fixedly connected to the drive connection unit 10. The buffer limiting mechanism 22 includes a slider 222 fixed to a first slide rod 221, a slider 222 slidably mounted on the first slide rod 221, a compression spring 223 providing elastic preload to the slider 222, and a stop plate 224 fixed to the first slide rod to limit the maximum stroke of the slider; the slider can move axially relative to the support frame 21.

[0050] The sensing and positioning unit 30 is mounted on the axial feed unit 20 and includes an observation module for visual positioning. The observation module includes a radiation-resistant camera and an illumination source, and is fixed on the drive connection unit 101.

[0051] A multi-stage attitude adaptive mechanism is connected to the slider of the axial feed unit 20. The first-stage adjustment mechanism 40 includes a first frame 41 connected to the support frame via a transverse rotating shaft placed parallel to the forward direction, and a first balance adjustment member 42 for providing damping or a preset balance position for the pitch rotation of the first frame 41. The first balance adjustment member 42 includes a knob plunger mounted on the first balance support, the top end of which abuts against the first frame 41.

[0052] The second-stage adjustment mechanism 50 is connected to the first-stage adjustment mechanism 40 and includes a probe carrier assembly rotatably connected to the first frame 41, and a second balance adjustment component for providing damping or a preset balance position for the rotation of the probe carrier assembly. The probe carrier assembly 51 consists of a first slider mounting bracket and a second slider mounting bracket fixedly connected to each other, and is rotatably connected to the first frame via a second rotating shaft. The second balance adjustment component includes a knob plunger mounted on the second slider mounting bracket, the top end of which abuts against the second slider mounting bracket.

[0053] The width adaptive measuring terminal 60 is connected to the second-stage adjustment mechanism 50, and includes two measuring arms 61 slidably mounted on the second slide rod 513, a measuring probe 62 fixed to the measuring arms 61, and an elastic reset element 63 connecting each measuring arm 61. The measuring arms 61 cooperate with the second slide rod 513 through linear bearings to achieve lateral sliding. The elastic reset element 63 is a tension spring, fixed to the measuring arms 61, providing a retracting reset force for the measuring arms 61. The measuring probe 62 is a thickness measuring probe based on the eddy current effect, fixed to the inside of the measuring arms 61.

[0054] In one specific embodiment, a method for measuring the oxide film on a fuel assembly grid using the aforementioned apparatus, combined with... Figures 1-4 Detailed explanation.

[0055] Step S101: Preparation and Initial Positioning: The remote operator controls the drive mechanism to move the entire measuring device 100 to the vicinity of the fuel assembly 200 to be tested. The operator observes the relative position of the measuring device and the target grid of the fuel assembly through real-time images transmitted from the observation module. By adjusting the attitude of the drive mechanism, the axis of the measuring device is roughly aligned with the center hole of the target grid, completing the initial visual correction. At this point, the device is in its initial position, and the measuring arm is in a retracted state under the action of the tension spring.

[0056] Step S102: Approaching and Entering the Grille: The operator or automatic program controls the drive mechanism to propel the entire measuring device smoothly and slowly toward the fuel assembly along its axial direction. As the front measuring arm begins to enter the grille cell, the grille strips apply an outward force to the inside of the measuring arm. This force overcomes the tension of the tension spring, forcing the two measuring arms to slide laterally along the second slide bar, achieving width adaptation and allowing the device to smoothly enter the grille.

[0057] Step S103: Contact and Multi-level Attitude Adjustment: As the device penetrates the grid, due to the potential slight tilt of the fuel assembly, the measuring device passively adapts through its multi-level attitude adaptive mechanism. The first-level adjustment mechanism nods around an axis parallel to the direction of travel to accommodate the tilt of the fuel assembly in the vertical plane; the second-level adjustment mechanism swings around an axis perpendicular to the direction of travel to accommodate the deflection of the fuel assembly in the horizontal plane. The synergistic effect of these two adjustment mechanisms ensures that the measuring probe 62 can approach the grid surface to be measured with the correct attitude.

[0058] Step S104: Buffer Feed, Trigger Limit and Data Acquisition: The device continues to advance slowly until the end face of the measuring probe is in complete contact with the surface of the strip to be measured in the grid and remains stable. At this time, the drive mechanism is still advancing slightly, pushing the slider to compress the spring and slide along the first slide bar to achieve a buffering effect. When the slider slides to contact the stop plate, the limit is triggered, and the control system commands the drive mechanism to stop advancing. The measuring instrument begins to acquire data and records the thickness value of the oxide film.

[0059] Step S105: Exit and Reset: After the measurement is completed, the control system controls the drive mechanism to slowly reverse the entire measuring device along the original path. During the retraction process, the pressure of the grid on the measuring arms gradually decreases, and under the tension of the tension springs, the measuring arms on both sides gradually retract towards the center. At the same time, the attitude adjustment mechanisms at each level gradually return to their initial equilibrium positions under the action of their respective balance adjustment components. The device completely exits the fuel assembly grid and returns to its safe initial position.

[0060] Compared with existing technologies, this invention has several significant advantages. First, by organically combining the drive connection unit with the external drive system, fully automated remote operation is achieved in high-radiation environments, completely solving the technical problem that personnel cannot enter areas with strong radiation for operation. The buffering and limiting design of the axial feed unit not only provides a reliable overload protection mechanism but also ensures a high degree of repeatability of the measurement position, laying a solid foundation for obtaining accurate and reliable measurement data.

[0061] The introduction of the sensing and positioning unit enables the entire measurement process to achieve "vision-mechanical" collaborative positioning capabilities. Coarse positioning is first performed through vision, followed by fine positioning through mechanical structure. This hierarchical positioning strategy greatly improves the system's reliability and fault tolerance. The innovative design of the multi-level attitude adaptive mechanism gives the device a flexible adjustment capability similar to that of a human wrist, enabling it to automatically compensate for the position and attitude deviations of the workpiece. This feature is particularly important when dealing with fuel assemblies with complex geometries due to irradiation deformation.

[0062] The unique configuration of the width-adaptive measurement terminal enables the device to intelligently adapt to grid cells of different sizes, eliminating the need for hardware replacements or complex adjustments for different fuel assembly specifications, thus greatly enhancing the equipment's versatility and efficiency. The entire system adopts a modular design, with each functional unit working both relatively independently and collaboratively. This design not only facilitates manufacturing and maintenance but also reserves space for future functional expansion and technological upgrades.

[0063] Most importantly, this invention, through the organic coordination of its various functional units, constructs a complete and highly reliable measurement system capable of long-term stable operation in extreme environments, providing a powerful technical means for in-service inspection of nuclear power plant fuel assemblies. The precise oxide film thickness data obtained through this device is of irreplaceable value for assessing fuel assembly performance, predicting their remaining lifetime, and optimizing reactor operation strategies.

[0064] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A device for measuring the oxide film on a fuel assembly grid, characterized in that, include: A drive connection unit for connecting to an external drive mechanism; An axial feed unit, connected to the drive connection unit, is configured to bring the measuring device toward or away from the grid of the fuel assembly to be measured along its axial direction. A sensing and positioning unit is disposed on the axial feed unit, including an observation module for visual positioning; A multi-stage attitude adaptive mechanism, connected to the execution end of the axial feed unit, includes: The first-stage adjustment mechanism is configured to make the measuring terminal nod about an axis parallel to the direction of travel to accommodate the tilt of the fuel assembly in the vertical plane. The second-stage adjustment mechanism, connected to the first-stage adjustment mechanism, is configured to cause the measuring terminal to swing about an axis perpendicular to the direction of travel in order to accommodate the deflection of the fuel assembly in the horizontal plane. A width-adaptive measurement terminal, connected to the second-level adjustment mechanism, includes at least one laterally sliding measurement arm and a measurement probe fixed to the measurement arm. The measurement arm is configured to open laterally under external force or retract under internal force.

2. The fuel assembly grid oxide film measuring device according to claim 1, characterized in that, The axial feed unit includes a support frame fixedly connected to the drive connection unit, and a buffer limiting mechanism that enables the multi-stage attitude adaptive mechanism and the width adaptive measurement terminal to move axially relative to the support frame.

3. The fuel assembly grid oxide film measuring device according to claim 2, characterized in that, The buffer limiting mechanism includes a first slide bar, a slider slidably mounted on the first slide bar, a compression spring that provides elastic preload to the slider, and a stop plate fixed to the first slide bar to limit the maximum stroke of the slider.

4. The fuel assembly grid oxide film measuring device according to claim 1, characterized in that, The first-stage adjustment mechanism includes a first frame rotatably connected to the axial feed unit, and a first balance adjustment member for providing damping or a preset balance position for the pitch rotation of the first frame.

5. The fuel assembly grid oxide film measuring device according to claim 1, characterized in that, The second-stage adjustment mechanism includes a probe carrier assembly rotatably connected to the first-stage adjustment mechanism.

6. The fuel assembly grid oxide film measuring device according to claim 5, characterized in that, The probe support assembly includes a first slider mounting bracket, a second slider mounting bracket, and a second slide bar mounted between the two. The second slider mounting bracket is connected to the first adjustment mechanism via a second rotating shaft and can swing around the axis of the second rotating shaft; The width adaptive measuring terminal is slidably sleeved on the second slide rod, so that the width adaptive measuring terminal can slide laterally along the second slide rod to adapt to the workpiece width, and can change its horizontal orientation with the swinging movement of the second slider mounting frame.

7. The fuel assembly grid oxide film measuring device according to claim 1, characterized in that, The width adaptive measurement terminal also includes an elastic reset element connected between each measuring arm, used to provide a reset internal force to retract the measuring arm.

8. The fuel assembly grid oxide film measuring device according to claim 1, characterized in that, The first-stage adjustment mechanism includes a guide element mounted on the contact surface with the fuel assembly grid. The guide element is a longitudinal roller used to roll into contact with the workpiece or reference surface during fine-tuning and to prevent the mechanism from tilting.

9. The fuel assembly grid oxide film measuring device according to claim 1, characterized in that, The measuring arm has at least two protruding bosses on the side facing the grid, and the bosses form a mounting position for installing and positioning the measuring probe.

10. A method for measuring the oxide film on a fuel assembly grid using the apparatus as described in any one of claims 1-9, characterized in that, Includes the following steps: Remote preliminary positioning is performed using the aforementioned observation module; The axial feed unit is controlled to drive the measuring device forward. The width adaptive measurement terminal passively adapts to the grid width, and the multi-level attitude adaptive mechanism passively adjusts the contact attitude of the measurement probe. When the measuring probe contacts the grid surface and reaches a preset contact state, it stops moving forward and begins data acquisition; The external drive mechanism is controlled to drive the measuring device to retract and reset.

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