Device and method for measuring thickness of oxidation film of nuclear reactor fuel cladding

Abstract

The invention relates to the technical field of nuclear reactor fuel cladding oxidation film thickness measurement, and discloses a nuclear reactor fuel cladding oxidation film thickness measurement device and method, and the device comprises a femtosecond laser system, an optical parameter adjustment system, a focusing adjustment system, an electrode plate, a micro-channel plate detector and a data acquisition system. The device has the beneficial effects that the thickness of the surface oxide layer can be effectively detected, the device is particularly suitable for detection of trace components, the bottlenecks of a traditional method in detection lower limit and precision are broken through, the device is compact in structure, and reliable and efficient technical support is provided for state monitoring and safety evaluation of the nuclear power station fuel cladding.

Description

Technical Field

[0001] This invention relates to the field of measurement technology of oxide film thickness of nuclear reactor fuel cladding, and more particularly to a device and method for measuring the oxide film thickness of nuclear reactor fuel cladding. Background Technology

[0002] During nuclear power plant operation, an oxide layer forms on the surface of the fuel cladding due to the high temperature and pressure environment. The thickness of this oxide layer directly affects the integrity and safety of the cladding. Therefore, accurate measurement of oxide layer thickness is crucial for nuclear reactor safety assessment and lifespan management. Currently, traditional measurement methods mainly rely on the eddy current effect. While simple to operate, these methods have significant limitations: firstly, they lack sensitivity for detecting low-content components in the material, making it difficult to analyze low-content substances; secondly, their measurement accuracy is limited, especially in the nanometer-scale thickness range, failing to meet the requirements for high-precision analysis. Therefore, there is an urgent need to develop a new oxide layer thickness measurement technology that achieves high precision, high sensitivity, low cost, and controllable contamination to improve the reliability and engineering applicability of nuclear power fuel cladding condition monitoring. Summary of the Invention

[0003] Therefore, it is necessary to address the existing problem of measuring the thickness of the oxide film on the fuel cladding of nuclear reactors, and propose a device and method for measuring the thickness of the oxide film on the fuel cladding of nuclear reactors.

[0004] A device for measuring the thickness of the oxide film on the fuel cladding of a nuclear reactor, the device comprising: Femtosecond laser systems are used to generate ultra-intense, ultra-short laser pulses; An optical parameter adjustment system is used to adjust the optical parameters of the ultra-intense and ultra-short laser pulse to obtain the target laser pulse; A focusing adjustment system, located downstream of the optical parameter adjustment system, is used to control the point of action of the target laser pulse on the surface of the fuel cladding to be tested, so as to generate plasma; Electrode plates are used to place the fuel cladding to be tested and to accelerate ions in the plasma; A microchannel plate detector, positioned downstream of the electrode plate, is used to receive ions; A data acquisition system, connected to the microchannel plate detector, is used to acquire the signal output by the microchannel plate detector and analyze the oxide film thickness of the fuel cladding under test based on the acquired data.

[0005] Furthermore, the device also includes: An optical diagnostic system is positioned on the optical path opposite to the direction in which the target laser pulse enters the focusing adjustment system. It is used to diagnose the position of the point of action based on the beam reflected from the focusing adjustment system by the fuel cladding under test, and to image the surface of the fuel cladding under test.

[0006] Furthermore, the optical diagnostic system includes a lens and a camera, which are sequentially arranged in the optical path opposite to the direction in which the target laser pulse enters the focusing adjustment system.

[0007] Furthermore, the device also includes a beam splitter, which is disposed between the optical parameter adjustment system and the focusing adjustment system for reflecting the target laser pulse.

[0008] Furthermore, the focusing adjustment system includes an off-axis parabolic mirror and a displacement stage. The off-axis parabolic mirror is disposed downstream of the optical parameter adjustment system and is used to receive the target laser pulse and focus the target laser pulse onto the fuel cladding to be tested. The displacement stage is located at the bottom of the off-axis parabolic mirror and connected to the off-axis parabolic mirror, and is used to adjust the position of the off-axis parabolic mirror.

[0009] Furthermore, the displacement stage is a six-dimensional high-precision nano-displacement stage.

[0010] Furthermore, the off-axis parabolic mirror is also provided with a through hole, which is arranged along the ion acceleration direction.

[0011] Furthermore, the device also includes: A vacuum maintenance system is used to provide and maintain the required vacuum environment for the device.

[0012] Furthermore, the optical parameter adjustment system includes at least one optical element selected from polarizer, attenuator, and beam size adjuster.

[0013] A method for measuring the thickness of the oxide film on the cladding of nuclear reactor fuel, implemented using the aforementioned device for measuring the thickness of the oxide film on the cladding of nuclear reactor fuel, the method comprising: An ultra-intense and ultra-short laser pulse is generated by a femtosecond laser system, and the optical parameters of the ultra-intense and ultra-short laser pulse are adjusted by an optical parameter adjustment system to obtain the target laser pulse. The target laser pulse is guided to the surface of the fuel cladding under test by a focusing adjustment system to generate plasma; The current ions in the plasma are accelerated using an electrode plate to move them to the microchannel plate detector. The type of ion is identified by the time difference in arrival of ions at the microchannel plate detector; Adjusting the position parameters in the focusing adjustment system and repeating the target step and the steps after the target step, multiple current ion types are obtained; wherein, the target step is to guide the target laser pulse to the surface of the fuel cladding to be tested through the focusing adjustment system to generate plasma; The oxide film thickness of the fuel cladding under test is analyzed based on the types of multiple current ions.

[0014] The beneficial effects of this invention are as follows: By using a femtosecond laser system to generate ultra-intense and ultra-short pulses, combined with plasma generation and time-of-flight mass spectrometry analysis technology, the point of action of the target laser pulse on the surface of the fuel cladding under test is continuously adjusted, thereby obtaining the elemental types at different depths of the fuel cladding under test, and further analyzing the oxide film thickness of the fuel cladding under test. This method can effectively detect the thickness of the surface oxide layer, and is especially suitable for the detection of trace components. It breaks through the bottlenecks of traditional methods in terms of detection limit and accuracy. The device has a compact structure and provides reliable and efficient technical support for the condition monitoring and safety assessment of fuel cladding in nuclear power plants. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] in: Figure 1 This is a schematic diagram of the structure of a device for measuring the thickness of the oxide film on the fuel cladding of a nuclear reactor in one embodiment; Figure 2 This is a flowchart of a method for measuring the thickness of the oxide film on the fuel cladding of a nuclear reactor in one embodiment.

[0017] Figure 1 The components are: 1. Femtosecond laser system; 2. Optical parameter adjustment system; 3. Beam splitter; 4. Lens; 5. Camera; 6. Electrode plate; 7. Fuel cladding to be tested; 8. Off-axis parabolic mirror; 9. Six-dimensional high-precision nanometer displacement stage; 10. Ions; 11. Microchannel plate detector; 12. Data acquisition system; 13. Vacuum maintenance system; 14. Through hole. Detailed Implementation

[0018] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of systems and methods consistent with those detailed in the appended claims or with some aspects of this application.

[0019] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover descriptions such as non-exclusive inclusion, so that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element. Furthermore, components, features, and elements with the same names in different embodiments of this application may have the same meaning or different meanings, the specific meaning of which must be determined by its interpretation in that specific embodiment or further in conjunction with the context of that specific embodiment.

[0020] It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit this application.

[0021] In the following description, the use of suffixes such as "module," "part," or "unit" to denote elements is solely for the purpose of illustrative purposes and has no specific meaning in itself. Therefore, "module," "part," or "unit" may be used interchangeably.

[0022] like Figure 1 As shown, the present invention provides a measuring device for the oxide film thickness of nuclear reactor fuel cladding 7. The device includes: a femtosecond laser system 1 for generating ultra-intense and ultra-short laser pulses; an optical parameter adjustment system 2 for adjusting the optical parameters of the ultra-intense and ultra-short laser pulses to obtain a target laser pulse; a focusing adjustment system, located downstream of the optical parameter adjustment system 2, for controlling the point of action of the target laser pulse on the surface of the fuel cladding 7 to generate plasma; an electrode plate 6 for placing the fuel cladding 7 to be tested and accelerating ions 9 in the plasma; a microchannel plate detector 11, located downstream of the electrode plate 6, for receiving ions 9; and a data acquisition system 12, connected to the microchannel plate detector 11, for acquiring the signal output by the microchannel plate detector 11 and analyzing the oxide film thickness of the fuel cladding 7 based on the acquired data.

[0023] In this embodiment, the main function of the femtosecond laser system 1 is to generate ultra-intense and ultra-short laser pulses. These laser pulses have extremely high energy density and extremely short pulse widths (typically in the picosecond to femtosecond range), which can efficiently ablate the surface of the material under test. The gain amplification of the laser generation is adjusted using an optical cavity, which generally has a highly reflective mirror configuration. The pulse width is usually in the picosecond or femtosecond range. The laser pulses are transmitted in a vacuum and are configured with mirrors to achieve optimal energy output. This system provides the necessary laser pulses for subsequent plasma generation and is a key initial energy source.

[0024] An optical parameter adjustment system 2 is positioned between the femtosecond laser system 1 and the focusing adjustment system. It is responsible for adjusting the optical parameters of the laser pulse to ensure it adapts to the material properties and surface condition of the fuel cladding 7 under test. The optical parameter adjustment system 2 includes optical components such as polarizers, attenuators, and beam size adjusters. By adjusting the intensity, focus, and direction of the laser, it ensures accurate focusing onto the surface under test. The effective operation of this system guarantees that the laser pulse achieves optimal ablation effects, thereby generating plasma.

[0025] The fuel cladding 7 is the sample to be tested, and its surface is oxidized.

[0026] The focusing adjustment system is located downstream of the optical parameter adjustment system 2. It is mainly used to accurately focus the adjusted target laser pulse onto the surface of the fuel cladding 7 to be tested. In a preferred embodiment, it consists of an off-axis parabolic mirror 8 and a highly precise nano-displacement stage 9. The off-axis parabolic mirror 8 is designed to effectively focus the laser pulse at a large angle, while the nano-displacement stage 9 enables fine-tuning of the laser focus, ensuring that the laser pulse accurately hits the focus and effectively induces plasma generation.

[0027] The electrode plate 6 is placed around the fuel cladding 7 to be tested. Its main purpose is to place the sample to be tested and to form an electric field by applying a high voltage to accelerate the ions 9 generated in the plasma. The electrode plate 6 will accelerate the ions 9 in the plasma formed during the laser ablation process, prompting them to enter the microchannel plate detector 11, thereby enhancing the signal strength and ensuring that the detector can effectively receive and identify various types of ions 9.

[0028] The microchannel plate detector 11 is located downstream of the electrode plate 6 and is responsible for receiving and detecting ions 9 accelerated from the plasma. Its structure consists of multiple tiny channels. When ions 9 pass through these channels, a multiplication effect occurs, generating an electrical signal that can be detected by subsequent systems. The detector can classify different types of ions 9 according to the arrival time and intensity of the signal, which is crucial for analyzing the composition of the fuel cladding 7 under test and the thickness of its oxide film.

[0029] The data acquisition system 12 is connected to the microchannel plate detector 11. By collecting the electrical signals output by the detector, the system performs data analysis and processing. The system is responsible for converting the acquired signals into digital information and deriving the remaining oxide film thickness and composition of the fuel cladding 7 by analyzing the time characteristics and intensity of the signals. This provides necessary data support for subsequent research and engineering applications and helps scientists and engineers make decisions.

[0030] In summary, the interconnected and complementary components together form a highly efficient and accurate device for measuring the oxide film thickness of nuclear reactor fuel cladding. This device offers controllable control over contaminants, low cost, and high measurement accuracy, especially for components with a content below 100 ppm, achieving high-precision thickness measurement.

[0031] In one embodiment, the device further includes: an optical diagnostic system disposed on the optical path opposite to the direction in which the target laser pulse enters the focusing adjustment system, for diagnosing the position of the point of action based on the beam reflected by the focusing adjustment system from the fuel cladding 7 under test, and imaging the surface of the fuel cladding 7 under test.

[0032] In this embodiment, the optical diagnostic system is set in the optical path opposite to the target laser pulse entering the focusing adjustment system. The main components include a lens 4 and a camera 5. The core function of the system is to detect and analyze the beam reflected by the fuel cladding 7 under test, and to determine the actual position of the laser pulse through imaging methods. Because the focusing adjustment system focuses the laser to a specific position through the off-axis parabolic mirror 8, the optical diagnostic system can monitor the changes in the reflected beam in real time and adjust the focusing adjustment system according to the changes to ensure that the laser is accurately focused on the predetermined point of action. This not only improves the measurement accuracy, but also effectively avoids potential errors caused by laser beam deviation.

[0033] The optical diagnostic system and the focusing adjustment system are connected by optical elements (such as optical fibers or optical path mirrors) to guide the focused reflected beam. The system's lens 4 is responsible for collecting and focusing the light signal reflected from the fuel cladding 7 under test, and focusing it onto the sensor of the camera 5. The camera 5 is used to capture the image of the reflected beam. The image processing software analyzes the degree of coincidence between the laser focus and the target point and feeds it back to the focusing adjustment system for more precise adjustment. This feedback mechanism forms a closed-loop control system, which enables the laser pulse to be monitored and adjusted in real time on the surface of the fuel cladding 7, thereby improving the reliability of the measurement.

[0034] During implementation, the optical diagnostic system can continuously monitor the position of the laser focus and, by analyzing the reflected light, help operators adjust the focusing parameters in a timely manner during laser ablation to achieve multiple measurements. This real-time monitoring and adjustment mechanism is the key to achieving high-precision measurement and helps improve the practicality and efficiency of the overall device in nuclear power applications. This enables the device to accurately measure nine types of ions at each point of action, thereby enabling the detection of oxide film thickness.

[0035] In one embodiment, the optical diagnostic system includes a lens 4 and a camera 5, wherein the lens 4 and the camera 5 are sequentially arranged in the optical path opposite to the direction in which the target laser pulse enters the focusing adjustment system.

[0036] In this embodiment, lens 4 is an indispensable optical element in the optical diagnostic system. Its main function is to collect the light signal reflected from the fuel cladding 7 under test and focus it onto the imaging sensor of camera 5. The design of lens 4 is usually to meet specific optical parameters, such as focal length and diameter, to ensure that all reflected light can be effectively captured, thereby improving image clarity and brightness. The material and shape of lens 4 (such as spherical or aspherical lens 4) also directly affect the light focusing efficiency and imaging quality. The precise configuration of lens 4 ensures that the point of action of the laser pulse on the surface of fuel cladding 7 can be accurately recorded, providing a solid foundation for subsequent image analysis.

[0037] Camera 5 mainly consists of an imaging sensor and related processing units, responsible for capturing images of the reflected beam after it has been focused by lens 4 in real time. Modern cameras 5 are usually equipped with highly sensitive sensors (such as CCD or CMOS) that can acquire clear images under low light conditions. Camera 5 can not only save the reflected images, but also convert these data into digital signals and analyze the position and state of the laser point of action through image processing algorithms. This information is crucial for evaluating the degree of fit between the laser focus and the surface under test, the thickness change of the oxide film, and the surface condition of the material.

[0038] In the optical diagnostic system, lens 4 and camera 5 are sequentially positioned on the optical path in the opposite direction of the focusing adjustment system. Specifically, lens 4 and camera 5 are connected in a straight line in the optical path. The front of lens 4 faces the fuel casing 7 to be tested, and is responsible for capturing the reflected light and focusing it into the optical system of camera 5. Camera 5 is positioned behind lens 4 so that it can directly receive the focused light signal. Camera 5 is connected to data acquisition system 12 through a data interface (such as USB or HDMI) to achieve rapid signal transmission and processing, thereby ensuring real-time monitoring and analysis.

[0039] Through this design, the optical diagnostic system can provide extremely high positioning accuracy and real-time feedback capability, ensuring that the laser pulse accurately acts on the predetermined focal point. This precise control is crucial for the safety of the nuclear reactor fuel cladding 7, effectively avoiding erroneous measurements due to laser deviation. At the same time, the combination of lens 4 and camera 5 can also perform multi-dimensional optical analysis on the surface of fuel cladding 7, providing a wider range of material property information to assist engineers in judgment and decision-making. This has a significant promoting effect on enhancing the effectiveness of static and dynamic detection. By continuously optimizing the quality of reflected light acquisition and imaging, the optical diagnostic system will significantly improve the performance and application potential of the entire measurement device.

[0040] In one embodiment, a beam splitter 3 is further included, which is disposed between the optical parameter adjustment system 2 and the focusing adjustment system for reflecting the target laser pulse.

[0041] In this embodiment, the beam splitter 3 is an optical element with specific optical properties, usually made of a semi-reflective and semi-transparent material. It is designed to both reflect and transmit light. The basic function of the beam splitter 3 is to separate light of different wavelengths. In this invention, this component is used to reflect laser pulses of a specific wavelength, thereby guiding them into the subsequent focusing adjustment system. In the application of this invention, the beam splitter 3 ensures that the laser pulse reaches the surface of the fuel cladding 7 at the correct time and position. By reflecting the laser, the beam splitter 3 effectively guides the light path to the off-axis parabolic mirror 8, which is then focused.

[0042] In terms of connection, the beam splitter 3 is positioned between the optical parameter adjustment system 2 and the focusing adjustment system, forming a continuous optical link. After the target laser pulse undergoes necessary adjustments through the optical parameter adjustment system 2, it will first reach the beam splitter 3. Here, the beam splitter 3 will reflect the laser pulse according to its design characteristics and guide it into the optical path of the focusing adjustment system. The beam splitter 3 and the optical parameter adjustment system 2 are closely connected through optical connections (such as lenses or optical fibers) to ensure that the intensity and quality of the transmitted beam are maintained in an optimal state.

[0043] The introduction of beam splitter 3 not only improves the flexibility of the system, but also provides accuracy of reflected light for subsequent focusing and measurement processes by effectively controlling the laser optical path. The reflected laser pulse can be better focused on the specific surface of the fuel cladding 7 to be measured, thereby generating the required plasma and laying the foundation for thickness measurement. In addition, the use of beam splitter 3 can reduce light loss and improve the overall energy efficiency of the system. By optimizing the path and direction of the laser pulse, beam splitter 3 ensures accurate laser positioning and also improves the reliability of the equipment in high-precision measurement.

[0044] In one embodiment, the focusing adjustment system includes an off-axis parabolic mirror 8 and a displacement stage 9. The off-axis parabolic mirror 8 is disposed downstream of the optical parameter adjustment system 2 and is used to receive the target laser pulse and focus the target laser pulse onto the fuel cladding 7 to be tested. The displacement stage 9 is disposed at the bottom of the off-axis parabolic mirror 8 and is connected to the off-axis parabolic mirror 8, and is used to adjust the position of the off-axis parabolic mirror 8.

[0045] The off-axis parabolic mirror 8 is a specially shaped optical reflecting and focusing mirror designed to focus incident light onto a specific point. Its structure is a parabolic part, which ensures that the light rays can converge along the focused beam after reflection, thereby achieving efficient light focusing. In this invention, the off-axis parabolic mirror 8 is used to receive the target laser pulse formed after passing through the optical parameter adjustment system 2 and focus it onto the surface of the fuel cladding 7 to be tested. The purpose of this focusing is to generate a strong local light field to excite the plasma, and then detect the ion composition 9 in the plasma, such as whether oxygen ions are present. Then, the position of the off-axis parabolic mirror 8 is moved, and the detection is continuously performed until it is detected that the excited plasma does not contain oxygen ions, thereby obtaining the thickness of the oxide film and achieving high-precision measurement of the oxide film thickness.

[0046] In terms of connection, the off-axis parabolic mirror 8 is located downstream of the optical parameter adjustment system 2 and is connected to the beam splitter 3 through an optical path to form an effective laser transmission line. The target laser pulse is reflected by the beam splitter 3 and then introduced into the entrance port of the off-axis parabolic mirror 8. This setting ensures that the laser can be accurately focused to the expected target position. In addition, the design of the off-axis parabolic mirror 8 is preferably to be seamlessly connected with other optical components (such as adjustment systems or detectors) to ensure that the laser beam maintains high energy and focus throughout the process.

[0047] The displacement stage 9 serves as the support base for the off-axis parabolic mirror 8. It is typically constructed from high-precision mechanical components and can be fine-tuned in multiple dimensions. The primary function of the displacement stage 9 is to precisely adjust the position of the off-axis parabolic mirror 8 to maintain optimal laser beam focusing under various experimental conditions. By controlling the mirror's height, angle, and lateral position, the displacement stage 9 can achieve nanometer-level displacement, enabling precise positioning of the laser focus on the sample under test. This precise adjustment function is particularly important when processing fuel cladding 7 with varying thicknesses and material properties.

[0048] In terms of connection, the displacement stage 9 is tightly connected to the bottom of the off-axis parabolic mirror 8, allowing for fine adjustments via electric or manual control, while ensuring the stability of the entire system. The displacement stage 9 can be connected to the computer control system via electrical or mechanical means to achieve real-time monitoring and adjustment capabilities. This connection enhances the flexibility of the focusing adjustment system in the precise positioning of the laser action point, allowing the operator to quickly adjust the focusing of the laser pulse according to specific experimental needs.

[0049] The focusing adjustment system precisely focuses the laser pulse onto the fuel cladding 7 under test to ensure the generation of the required plasma, thereby achieving effective ablation of the oxide layer. In addition, the adjustment function of the displacement stage 9 allows the system to flexibly respond to various material properties and experimental environment changes, ensuring the stability and accuracy of the measurement results. Overall, the integration of the focusing adjustment system enables the measuring device of the present invention to not only have efficient energy transmission capabilities, but also enhance its adaptability to complex materials and measurement accuracy.

[0050] In one embodiment, the displacement stage 9 is a six-dimensional high-precision nano-displacement stage.

[0051] In this embodiment, the six-dimensional high-precision nanoscale displacement stage is a high-precision fine-tuning device capable of minute movements in six degrees of freedom. These six degrees of freedom include: translation along the X, Y, and Z directions (i.e., forward / backward, left / right, and up / down movement), rotation around the Z direction, and horizontal and vertical pitch adjustment of the off-axis parabolic mirror frame. This design enables the displacement stage 9 to meet complex optical adjustment requirements, demonstrating its powerful flexibility, especially in scientific research and industrial applications requiring high-precision positioning.

[0052] The six-dimensional high-precision nano-displacement stage consists of multiple precision servo motors and feedback sensors. The servo motors are responsible for driving the motion, while the sensors monitor the actual position of the displacement stage 9 in real time. Through a closed-loop control system, the displacement stage 9 can achieve real-time precise adjustment to ensure that the laser focus is always in the optimal position. This high-precision adjustment capability ensures that accurate and reliable data can be obtained in oxide film thickness measurement, thereby improving the overall performance of the system.

[0053] The six-dimensional high-precision nanometer displacement stage is directly connected to the off-axis parabolic mirror 8 via a stable base. Its design typically incorporates a shock-absorbing structure to reduce external interference and ensure stability during laser focusing. The exit surface of the displacement stage 9 is in close contact with the bottom of the off-axis parabolic mirror 8 to ensure the laser beam does not deviate during adjustment and to maintain optical path consistency. Furthermore, the control system of the displacement stage 9 is interconnected with the main control system of the overall measuring device, typically using interfaces such as USB or Ethernet for data transmission. This connection ensures that adjustment commands from the displacement stage 9 are transmitted in real time, and feedback information is promptly returned to the main control system, enabling efficient control and adjustment.

[0054] In the application of oxide film thickness measurement, the position of the focusing lens is finely adjusted to achieve precise irradiation of the fuel cladding 7 at different depths. Through its high-precision displacement capability, the displacement stage 9 ensures that the laser pulse can automatically adjust the irradiation depth in a short time, ensuring that the plasma generated each time is plasma at a different depth. Its precise control function not only improves the measurement accuracy but also significantly reduces human error, greatly improving the convenience and safety of the operation process. Overall, the introduction of the six-dimensional high-precision nano-displacement stage provides strong and flexible technical support for the measurement device of this invention and is one of the key factors for achieving efficient and reliable oxide film thickness measurement.

[0055] In one embodiment, the off-axis parabolic mirror 8 is further provided with a through hole 14, which is arranged along the acceleration direction of the ions 10.

[0056] The off-axis parabolic mirror 8 is a uniquely shaped optical element designed to focus incident light onto a specific focal point. Its structure is parabolic, unlike traditional centrosymmetric parabolic designs; the optical axis of the off-axis parabolic mirror 8 does not coincide with the optical mirror surface. This design allows the off-axis parabolic mirror 8 to more effectively focus laser pulses, forming a strong local optical field to excite plasma on the surface of the fuel cladding 7 under test. It should be noted that the through-hole 14 is designed to allow ions to pass through, therefore it does not need to be excessively large, and should be designed to maintain the integrity of the optical path.

[0057] The through hole 14 is a unique design element of the off-axis parabolic mirror 8. The through hole 14 is set along the acceleration direction of ions 10, so that ions 10 can pass through to the microchannel plate detector 11. The generated ions 9 can be accelerated by the electrode plate 6 and then pass through the through hole 14 to enter the microchannel plate detector 11 for detection and analysis.

[0058] In one embodiment, the apparatus further includes: Vacuum maintenance system 13 is used to provide and maintain the required vacuum environment for the device.

[0059] A vacuum maintenance system 13 typically includes various devices and technologies used to create and maintain a low-pressure environment. Common components include vacuum pumps, vacuum valves, gas monitors, and vacuum piping. First, the vacuum pump is the core of the system, responsible for extracting gas from inside the measuring device to reduce the pressure in the measuring space to the required vacuum level, typically in the range of a few millibars to microbars. Pump types can include rotary vane pumps, molecular pumps, or turbomolecular pumps, the specific choice depending on the required vacuum level and the specific requirements of the system. Second, vacuum valves control the inflow and outflow of gas, allowing the system to be sealed or opened under different operating conditions. This allows maintenance or sample replacement to be performed without disrupting the vacuum. Furthermore, the gas monitor continuously monitors the vacuum environment, providing pressure data feedback to ensure the system maintains the set vacuum level.

[0060] The vacuum maintenance system 13 is connected to other components via a series of pipes and connectors, forming a complete closed loop. Specifically, the vacuum pump's inlet is connected to the vacuum chamber of the measuring device, allowing the pump's pumping action to directly affect the gas pressure within the device. Simultaneously, a vacuum valve is also connected to the pump and the measuring device, enabling control of the gas passage when needed. Monitoring instruments are connected to the system's main control unit via data cables, providing real-time feedback of environmental pressure data to the operator.

[0061] In terms of design, these components need to work together to ensure that an ideal vacuum is maintained throughout the laser ablation and reactor fuel cladding 7 welding processes. Furthermore, the vacuum maintenance system 13 must have good isolation capabilities to prevent the infiltration of external gases from affecting the accuracy of the measurement process.

[0062] The vacuum maintenance system 13 is particularly important in the oxide film thickness measurement process because laser pulse ablation in a vacuum environment can significantly reduce air interference and improve the interaction efficiency between the laser and the plasma. At the same time, the low-pressure environment can also effectively avoid measurement errors caused by oxidation or contamination of the sample surface.

[0063] Overall, the vacuum maintenance system 13 not only provides the necessary environmental conditions in the implementation of this invention to ensure the accuracy and stability of the measurement process, but also promotes the scientific development of measuring the oxide film thickness of nuclear reactor fuel cladding 7 through its efficient technical implementation.

[0064] In one embodiment, the optical parameter adjustment system 2 includes at least one optical element selected from a polarizer, an attenuator, and a beam size adjuster.

[0065] In this embodiment, the optical parameter adjustment system 2 consists of multiple different optical elements used to adjust the optical characteristics of the laser pulse. These components include at least one of a polarizer, an attenuator, and a beam size adjuster. Each component plays an important role in the entire optical system to ensure that the laser pulse can illuminate the surface of the fuel cladding 7 under test in an optimal state. The following is a detailed explanation of these optical elements, including their structure, function, and connection relationships.

[0066] A polarizer is an optical element used to control the direction of light wave vibration in a beam. It allows light waves in a specific direction to pass through while blocking light waves in other directions. By using a polarizer, the system can filter out unpolarized light or change the polarization state of a laser pulse, thereby improving the coupling efficiency of the laser when it contacts a material surface. In this invention, the polarizer can be placed at a certain position in the optical path to optimize the characteristics of the laser pulse and ensure effective excitation of the sample surface during laser ablation.

[0067] Attenuators are another crucial optical component designed to reduce the energy intensity of laser pulses. This function is particularly important for laser measurements, as excessively strong laser pulses can cause over-ablation of the sample or damage its surface structure. Attenuators absorb a portion of the laser energy, ensuring the laser pulse intensity is suitable for precise measurements. For example, when measuring samples with low content, attenuators effectively prevent over-ablation, ensuring sample integrity.

[0068] The beam size adjuster is primarily responsible for changing the diameter or aspect ratio of the laser beam to suit the characteristics of the material being tested. By adjusting the beam size, the system can ensure that the laser pulse forms a better focused effect when irradiating the sample. Beam adjustment helps improve the uniformity and stability of the optical field, avoiding localized overheating or undercooling, thereby achieving a more uniform ablation effect.

[0069] Each component of the optical parameter adjustment system 2 is connected via an optical interface to form a continuous optical path. Typically, the laser pulse first passes through an attenuator (if present), then a polarizer, and finally a beam size adjuster. Through the adjustment of these components, the target laser pulse is ultimately formed. The flexible configuration of these components allows operators to precisely adjust multiple parameters of the laser by selecting appropriate combinations of optical elements, ensuring that the laser pulse directed at the fuel cladding 7 under test has optimal characteristics.

[0070] In the process of measuring oxide film thickness, the optical parameter adjustment system 2 plays a particularly important role. By precisely adjusting the polarization, intensity, and beam size of the laser pulse, the system can ensure consistent and reliable experimental results on fuel cladding 7 of different materials and thicknesses. This not only improves the accuracy of the measurement but also reduces experimental errors caused by improper optical parameters, thus promoting technological progress in materials testing and evaluation in the nuclear energy industry. Overall, the optical parameter adjustment system 2 is one of the keys to ensuring the effective implementation of this invention. Through the interconnection and cooperation of various optical components, it achieves superior performance of laser measurement technology.

[0071] Reference Figure 2 The present invention also provides a method for measuring the thickness of the oxide film on the nuclear reactor fuel cladding 7, which is achieved by the aforementioned measuring device for the thickness of the oxide film on the nuclear reactor fuel cladding 7, and the method includes: S1: An ultra-intense and ultra-short laser pulse is generated by a femtosecond laser system 1, and the optical parameters of the ultra-intense and ultra-short laser pulse are adjusted by an optical parameter adjustment system 2 to obtain the target laser pulse; S2: The target laser pulse is guided to the surface of the fuel cladding 7 under test by a focusing adjustment system to generate plasma; S3: The current ion 9 in the plasma is accelerated using the electrode plate 6 to move the current ion 9 to the microchannel plate detector 11. S4: The time difference of ion 9 arriving at the microchannel plate detector 11 is used to identify the type of ion 9 at present; S5: Adjust the position parameters in the focusing adjustment system and repeat the target step and the steps after the target step to obtain multiple types of current ions 9; wherein, the target step is to guide the target laser pulse to the surface of the fuel cladding 7 to be tested through the focusing adjustment system to generate plasma; S6: Analyze the oxide film thickness of the fuel cladding 7 to be tested based on the types of multiple current ions 9.

[0072] As described in step S1 above, the femtosecond laser system 1 generates ultra-intense and ultra-short laser pulses by exciting the gain medium. The pulse width of these pulses is typically in the picosecond range (10^6). -12 (seconds) or femtoseconds (10) -15Within a range of seconds, it possesses extremely high energy density. The generated laser energy is highly concentrated, causing the laser to produce a high-intensity light field on the material surface, which can trigger a series of physical processes, including plasma formation. In this process, the optical parameter adjustment system 2 plays a crucial role, as it can adjust the polarization, intensity, and beam size of the laser pulse to ensure that the laser pulse is adapted to the properties of the sample under test. The precise adjustment of this process is particularly critical to the success of subsequent steps, with the aim of obtaining a target laser pulse that meets specific experimental conditions in order to achieve optimal results in the subsequent ablation process.

[0073] As described in step S2 above, the target laser pulse, after optical parameter adjustment, is guided to the surface of the fuel cladding 7 under test by a focusing adjustment system. The focusing adjustment system typically includes an off-axis parabolic mirror 8 and a precision displacement stage 9, capable of focusing the laser pulse to a small focal point, forming a strong optical field. After the laser pulse is focused on the surface of the fuel cladding 7, it causes a rapid rise in the local surface temperature, resulting in intense physical processes on the material surface, including evaporation and plasma generation. This process involves the release of a large amount of energy in a short period. The generated plasma, composed of ions 9 and electrons, has high kinetic energy and temperature, providing a basis for the acceleration of ions 9 in subsequent steps.

[0074] As described in step S3 above, the function of electrode plate 6 is to accelerate ions 9 in the generated plasma. A high voltage is applied around electrode plate 6 to form an electric field, which effectively accelerates ions 9 in the plasma, causing them to move towards the microchannel plate detector 11. By adjusting the voltage applied to electrode plate 6, the speed and energy of the accelerated ions 9 can be precisely controlled, which is crucial for measuring the type and concentration of ions 9. After acceleration, ions 9 will pass through the central hole of off-axis parabolic mirror 8 and move towards the microchannel plate detector 11 along the designed optical path. This process ensures that the generated signal can be effectively captured and analyzed.

[0075] As described in step S4 above, when the microchannel plate detector 11 receives ion 9, it analyzes the arrival time of ion 9 and the signal it generates. Since different types of ion 9 have different mass-to-charge ratios (the ratio of charge to mass of ion 9), the difference in the arrival time of ion 9 can be used as a criterion for distinguishing the type of ion 9. Through precise measurement of arrival time, the system can identify and classify the current type of ion 9 and generate corresponding data. This step not only provides information about the gas phase composition but also helps in the subsequent analysis of oxide film thickness, clarifying the distribution of different elements or compounds in the sample. Since the arrival time of ion 10 is related to the mass-to-charge ratio (m / q), a time-ion type correspondence can be established by calibrating standard samples.

[0076] As described in step S5 above, in order to obtain more ion type 9 data, it is necessary to adjust the position parameters of the focusing adjustment system. By changing the position of the off-axis parabolic mirror 8, the system can move the focal point to different surface regions, thereby exciting plasmas in multiple different regions. This repeated operation allows for the measurement of ion type 9 at multiple different locations. Repeating the above steps can not only obtain ion 9 characteristics at different locations, but also observe changes in elemental composition at different depths, providing more comprehensive data support for the final analysis.

[0077] As described in step S6 above, the oxide film thickness of the fuel cladding 7 is analyzed based on the types and relative abundance of multiple current ions 9. By statistically analyzing and organizing the ion 9 data obtained in the previous steps, and combining known chemical information and quantitative models, the thickness and composition of the oxide film can be calculated. Through quantitative analysis of various ions 9, the concentration distribution and overall thickness information of the oxide film can be obtained. Specifically, this includes the detection of oxygen ions. During repeated measurements, when the laser focus moves to different depth regions, the system monitors the release of ions 9 from the plasma, especially the presence of oxygen ions. By comparing the types of ions 9 at different depth regions, the presence or absence of oxygen ions can be identified. When the concentration of oxygen ions changes from present to absent, it means that the measured depth corresponds exactly to the bottom boundary of the oxide film, and this depth can be recorded as the thickness of the oxide film. By analyzing the characteristics and changing trends of ions 9 at different depth positions, regular patterns or data models can be formed, providing a basis for subsequent material evaluation and processing. Furthermore, by plotting the curve of ion signal intensity versus depth, the depth at which the oxygen ion signal drops to a preset level is the oxide film thickness. This method ensures high-precision measurement of oxide film thickness, reflects the effectiveness and stability of the material under high temperature and high pressure conditions, and provides scientific support for the maintenance and management of nuclear power technology.

[0078] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0079] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A device for measuring the thickness of the oxide film on the fuel cladding of a nuclear reactor, characterized in that, The device includes: Femtosecond laser systems are used to generate ultra-intense, ultra-short laser pulses; An optical parameter adjustment system is used to adjust the optical parameters of the ultra-intense and ultra-short laser pulse to obtain the target laser pulse; A focusing adjustment system, located downstream of the optical parameter adjustment system, is used to control the point of action of the target laser pulse on the surface of the fuel cladding to be tested, so as to generate plasma; Electrode plates are used to place the fuel cladding to be tested and to accelerate ions in the plasma; A microchannel plate detector, positioned downstream of the electrode plate, is used to receive ions; A data acquisition system, connected to the microchannel plate detector, is used to acquire the signal output by the microchannel plate detector and analyze the oxide film thickness of the fuel cladding under test based on the acquired data.

2. The measuring device for the thickness of the oxide film on the nuclear reactor fuel cladding according to claim 1, characterized in that, Also includes: An optical diagnostic system is positioned on the optical path opposite to the direction in which the target laser pulse enters the focusing adjustment system. It is used to diagnose the position of the point of action based on the beam reflected from the focusing adjustment system by the fuel cladding under test, and to image the surface of the fuel cladding under test.

3. The measuring device for measuring the thickness of the oxide film on the nuclear reactor fuel cladding according to claim 2, characterized in that, The optical diagnostic system includes a lens and a camera, which are sequentially arranged on the optical path opposite to the direction in which the target laser pulse enters the focusing adjustment system.

4. The measuring device for the thickness of the oxide film on the nuclear reactor fuel cladding according to claim 1, characterized in that, It also includes a beam splitter, which is disposed between the optical parameter adjustment system and the focusing adjustment system, and is used to reflect the target laser pulse.

5. The measuring device for the thickness of the oxide film on the nuclear reactor fuel cladding according to claim 1, characterized in that, The focusing adjustment system includes an off-axis parabolic mirror and a displacement stage. The off-axis parabolic mirror is disposed downstream of the optical parameter adjustment system and is used to receive the target laser pulse and focus the target laser pulse onto the fuel cladding to be tested. The displacement stage is located at the bottom of the off-axis parabolic mirror and connected to the off-axis parabolic mirror, and is used to adjust the position of the off-axis parabolic mirror.

6. The measuring device for the thickness of the oxide film on the nuclear reactor fuel cladding according to claim 5, characterized in that, The displacement stage is a six-dimensional high-precision nano-displacement stage.

7. The measuring device for measuring the thickness of the oxide film on the nuclear reactor fuel cladding according to claim 5, characterized in that, The off-axis parabolic mirror is also provided with a through hole, which is arranged along the ion acceleration direction.

8. The measuring device for the thickness of the oxide film on the nuclear reactor fuel cladding according to claim 1, characterized in that, Also includes: A vacuum maintenance system is used to provide and maintain the required vacuum environment for the device.

9. The measuring device for the thickness of the oxide film on the nuclear reactor fuel cladding according to claim 1, characterized in that, The optical parameter adjustment system includes at least one optical element selected from polarizer, attenuator, and beam size adjuster.

10. A method for measuring the thickness of the oxide film on the fuel cladding of a nuclear reactor, characterized in that, The method is achieved by the measuring device for measuring the thickness of the oxide film on the nuclear reactor fuel cladding as described in any one of claims 1-9, and the method includes: An ultra-intense and ultra-short laser pulse is generated by a femtosecond laser system, and the optical parameters of the ultra-intense and ultra-short laser pulse are adjusted by an optical parameter adjustment system to obtain the target laser pulse. The target laser pulse is guided to the surface of the fuel cladding under test by a focusing adjustment system to generate plasma; The current ions in the plasma are accelerated using an electrode plate to move them to the microchannel plate detector. The type of ion is identified by the time difference in arrival of ions at the microchannel plate detector; Adjusting the position parameters in the focusing adjustment system and repeating the target step and the steps after the target step, multiple current ion types are obtained; wherein, the target step is to guide the target laser pulse to the surface of the fuel cladding to be tested through the focusing adjustment system to generate plasma; The oxide film thickness of the fuel cladding under test is analyzed based on the types of multiple current ions.

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