A kind of nuclear power plant metal pipeline oblique incidence ultrasonic online cleaning device

Abstract

The application discloses a kind of nuclear power plant metal pipeline oblique incidence ultrasonic online cleaning device, including ultrasonic vibrator module, acoustic wedge and pipeline clamp;Ultrasonic vibrator module is used to excite the longitudinal wave of ultrasonic frequency by longitudinal vibration;Acoustic wedge is used to regulate and control longitudinal wave emitted by ultrasonic vibrator module and is transmitted to the metal pipeline to be cleaned;Pipeline clamp is used to fix acoustic wedge on the metal pipeline to be cleaned.Working time, acoustic wedge makes ultrasonic wave penetrate pipe wall with optimal incidence angle and excite mode conversion, and deposits inside the pipeline are cleaned.The application has high cleaning efficiency, can realize non-destructive cleaning and online cleaning, has the advantages of convenient operation, safety and reliability, less secondary waste, etc., and is especially suitable for application in high requirement environment such as nuclear power plant.

Description

Technical Field

[0001] This invention relates to the field of nuclear facility cleaning technology, and in particular to an online ultrasonic cleaning device for oblique incidence of metal pipes in nuclear power plants, which is suitable for in-situ cleaning of radioactively contaminated pipes such as pressurized water reactor main loop pipes and steam generator heat transfer tubes. Background Technology

[0002] In the field of nuclear power generation and nuclear facility operation, pipelines, as core components for transporting critical fluids such as coolants, fuels, and radioactive waste, are directly related to their internal cleanliness and operational efficiency and safety. The accumulation of deposits, corrosion products, and radioactive contaminants inside nuclear pipelines not only reduces fluid transport efficiency and increases energy consumption but can also corrode pipeline materials, affecting structural integrity and even triggering radioactive leaks, posing a serious threat to environmental and personnel safety. Therefore, regular cleaning and maintenance of nuclear pipelines is a crucial step in ensuring the safe and efficient operation of nuclear facilities.

[0003] Traditional nuclear pipeline cleaning methods mainly include chemical cleaning, high-pressure water jet cleaning, and mechanical scraping. Chemical cleaning involves injecting cleaning agents into the pipeline, using chemical reactions to remove deposits and contaminants. However, chemical cleaning agents are often corrosive, potentially causing secondary damage to pipeline materials, and the waste liquid generated during the cleaning process is difficult to treat, easily leading to environmental pollution problems. High-pressure water jet cleaning uses high-pressure water jets to flush the inner wall of the pipeline to remove deposits. However, this method has high requirements for the pipeline material and structure, is not suitable for all types of nuclear pipelines, and the water mist and splashes generated during the cleaning process may carry radioactive materials, increasing the difficulty of radiation protection. Mechanical scraping removes deposits from the inner wall of the pipeline by physical means, but this method is complex to operate, easily damages the inner wall of the pipeline, and has low cleaning efficiency.

[0004] In recent years, ultrasonic cleaning technology has been widely used in industrial cleaning. It utilizes the physical effects of ultrasonic waves in liquids, such as cavitation, acceleration, and direct flow, to effectively remove dirt from the surface and tiny crevices of workpieces. Ultrasonic cleaning has advantages such as high cleaning efficiency, no pollution, and applicability to workpieces with complex shapes, thus showing broad application prospects in the field of nuclear pipeline cleaning. However, applying ultrasonic cleaning technology to nuclear pipeline cleaning still faces many challenges: Existing ultrasonic cleaning devices have limited decontamination capabilities: nuclear pipelines typically have thick walls, often made of high-strength steel. Ultrasonic waves attenuate as they penetrate the pipe walls, reducing cleaning efficiency. Traditional ultrasonic cleaning techniques often employ a vertical incident method, where ultrasonic waves are emitted perpendicular to the inner wall of the pipeline. This method limits the penetration ability of the ultrasonic waves, making it difficult to effectively clean deep-seated dirt inside the pipeline.

[0005] The cleaning equipment has poor adaptability: Nuclear facilities contain a wide variety of pipes with different diameters, wall thicknesses, and materials, making it difficult for traditional ultrasonic cleaning equipment to meet the cleaning needs of different pipes. In addition, nuclear pipelines are usually located in confined spaces, making the installation and disassembly of the cleaning equipment difficult, which increases the difficulty and cost of cleaning operations.

[0006] Mechanical vibration effects: Mechanical vibrations generated during ultrasonic cleaning may damage pipelines and surrounding structures, especially in nuclear facilities where pipelines are closely connected to surrounding equipment. Vibration transmission may cause equipment to loosen, be damaged, or affect operational stability.

[0007] Online cleaning is challenging: nuclear facilities typically require continuous operation, and shutdown for cleaning would severely impact production efficiency and economic benefits. Therefore, developing an online, non-destructive, and efficient ultrasonic cleaning device is of great significance for ensuring the safe and efficient operation of nuclear facilities.

[0008] To address the aforementioned issues, scholars and engineers both domestically and internationally have conducted extensive research and practical studies, proposing various improvement solutions. For example, optimizing the design of ultrasonic generators and transducers to increase the transmission power and frequency of ultrasonic waves enhances their penetration ability; employing flexible cleaning heads and adaptive clamping mechanisms improves the adaptability of cleaning devices to different pipelines; introducing vibration-damping materials and structures reduces the impact of mechanical vibration on pipelines and surrounding structures; and developing online cleaning technologies and devices to achieve continuous cleaning and maintenance of nuclear pipelines. However, these solutions still have many shortcomings, such as low cleaning efficiency, weak adaptability, poor vibration damping effect, and the difficulty of online cleaning, making it difficult to meet the actual needs of nuclear pipeline cleaning.

[0009] Therefore, developing a novel online ultrasonic cleaning device for nuclear pipelines, overcoming the limitations of traditional ultrasonic cleaning technology, and achieving efficient, non-destructive, online cleaning operations is of great significance for ensuring the safe and efficient operation of nuclear facilities, reducing cleaning costs, and improving economic benefits. Based on this background, this invention proposes an innovative online ultrasonic cleaning device for nuclear pipelines. By employing key technologies such as oblique incidence ultrasonic cleaning technology, acoustic wave control modules, and adaptive clamping systems, it achieves efficient, non-destructive, online cleaning of nuclear pipelines, providing new ideas and solutions for the development of pipeline maintenance technology for nuclear facilities. Summary of the Invention

[0010] The technical problem to be solved by this invention is to address the deficiencies mentioned in the background technology by providing an oblique-incident ultrasonic online cleaning device for nuclear power plant metal pipelines. Through innovative oblique-incident ultrasonic cleaning technology, combined with acoustic wedges and pipeline clamps, it achieves rapid installation on nuclear pipelines and carries out efficient, non-destructive, online cleaning of nuclear pipelines, providing strong technical support for the continuous and safe operation of nuclear facilities.

[0011] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: An online ultrasonic cleaning device for oblique incidence of metal pipes in nuclear power plants includes an ultrasonic transducer module, an acoustic wedge, and a pipe clamp; The ultrasonic transducer module is used to excite longitudinal waves of ultrasonic frequency through longitudinal vibration, and includes a preload bolt, a front cover plate, a rear cover plate, and a piezoelectric component. The front cover plate is cylindrical, and a countersunk through hole for engaging with the pre-tightening bolt is provided at the center of one end face; The rear cover plate is a frustum, the diameter of the smaller end of its end face is equal to the diameter of the cross-section of the front cover plate, and the center of the smaller end face is provided with a first threaded blind hole for cooperating with the preload bolt. The piezoelectric component comprises 2N piezoelectric ceramic sheets; each piezoelectric ceramic sheet is annular in shape, with an outer diameter equal to the diameter of the front cover plate cross-section, and is polarized along the thickness direction; the 2N piezoelectric ceramic sheets are stacked sequentially, with the same polarization direction; The pre-tightening bolt passes through the countersunk hole and 2N piezoelectric ceramic plates in sequence on the front cover plate and is then threaded to the first threaded blind hole on the rear cover plate, clamping the piezoelectric assembly between the front cover plate and the rear cover plate. The acoustic wedge is used to regulate the longitudinal wave emitted by the ultrasonic transducer module and transmit it to the metal pipe to be cleaned. It includes an inclined wall, an upper wall, a bottom wall, and a front wall, a first side wall, a rear wall, and a second side wall that are vertically connected end to end. The bottom wall of the acoustic wedge is provided with a groove for engaging with the metal pipe to be cleaned; The groove is a cylindrical curved surface with its axis perpendicular to the front wall of the acoustic wedge; The inclined wall of the acoustic wedge and the larger end face of the rear cover plate are coaxially fixed together. The first and second sidewalls of the acoustic wedge are respectively connected to the pipe clamp; The pipe clamp is used to fix the acoustic wedge block to the metal pipe to be cleaned, and includes a first shoulder block, a second shoulder block, a first frame, a second frame, a first hinge, a second hinge, a first pad block, a second pad block, and an adjustable hook and loop clamp. The first shoulder block and the second shoulder block have the same structure and are symmetrically arranged on both sides of the acoustic wedge block, respectively perpendicularly fixed to the first side wall and the second side wall of the acoustic wedge block. The first frame and the second frame have the same structure, both being L-shaped and each containing a long plate and a short plate, with one end of the long plate and one end of the short plate being perpendicularly fixed together. The other end of the first frame long plate is connected to the first shoulder block via the first hinge, and the other end of the short plate is connected to one end of the adjustable snap fastener; the other end of the second frame long plate is connected to the second shoulder block via the second hinge, and the other end of the short plate is connected to the other end of the adjustable snap fastener; the axis of rotation of the first hinge and the second hinge is parallel to the circumferential direction of the groove on the bottom wall of the acoustic wedge; The first pad and the second pad are respectively disposed on the inner walls of the first frame and the second frame, and are used to cooperate with the metal pipe to be cleaned; The adjustable snap fastener is used to connect or loosen the short plates of the first frame and the second frame, and to adjust the distance between the short plates of the first frame and the second frame when connecting, so that the groove on the bottom wall of the acoustic wedge, the first pad, the second pad and the metal pipe to be cleaned fit tightly, thereby fixing the acoustic wedge on the metal pipe to be cleaned.

[0012] As a further optimization of the oblique-incidence ultrasonic online cleaning device for metal pipes in nuclear power plants according to the present invention, the piezoelectric ceramic sheet is a PZT-8 piezoelectric ceramic sheet.

[0013] As a further optimization of the oblique-incidence ultrasonic online cleaning device for metal pipes in nuclear power plants according to the present invention, the first pad and the second pad are polyurethane shock-absorbing pads.

[0014] As a further optimization of the oblique-incidence ultrasonic online cleaning device for metal pipes in nuclear power plants according to the present invention, the inner walls of the connection between the long plate and the short plate in the first frame and the second frame are chamfered.

[0015] As a further optimization of the oblique-incidence ultrasonic online cleaning device for metal pipes in nuclear power plants according to the present invention, both the first hinge and the second hinge are butterfly hinges.

[0016] As a further optimization of the oblique-incidence ultrasonic online cleaning device for metal pipes in nuclear power plants according to the present invention, the acoustic wedge is made of brass.

[0017] As a further optimization of the oblique-incidence ultrasonic online cleaning device for metal pipes in nuclear power plants according to the present invention, the center of the oblique wall of the acoustic wedge is provided with a threaded post that is perpendicularly fixed to the oblique wall; the center of the larger end of the rear cover plate is provided with a second threaded blind hole for cooperating with the threaded post; the threaded post and the second threaded blind hole make the rear cover plate and the acoustic wedge block fixedly connected.

[0018] As a further optimization of the oblique-incidence ultrasonic online cleaning device for metal pipes in nuclear power plants according to the present invention, the first shoulder block, the second shoulder block, the first frame, and the second frame are all made of 6061-T6 aluminum alloy.

[0019] Compared with the prior art, the present invention, employing the above technical solution, has the following technical effects: High cleaning efficiency: Experiments show that the cavitation intensity of this invention in DN80 pipelines reaches 1.5 MPa, significantly improving the cleaning efficiency of nuclear pipelines compared to traditional vertical incident cleaning methods. This improvement is mainly due to the mode conversion design of the acoustic wave control module and the tight fit of the adaptive clamping system, which allows the ultrasonic waves to penetrate the pipe wall more deeply and clean the deposits more effectively.

[0020] Non-destructive cleaning: This invention employs a physical cleaning method, avoiding the contaminants and pipeline corrosion problems that may be introduced by chemical cleaning. During the cleaning process, the energy of the ultrasonic waves is mainly concentrated inside the pipeline, causing no damage to the pipeline wall itself. This feature ensures the safe operation of nuclear facilities and extends the service life of the pipelines.

[0021] Online cleaning: This invention features a compact design, is easy to install and disassemble, and allows for online cleaning of nuclear facilities without shutting them down. This function significantly reduces downtime losses and improves the continuous operation capability and economic efficiency of nuclear facilities. Simultaneously, online cleaning can promptly detect and address deposits inside pipelines, preventing safety hazards such as pipeline blockage and corrosion caused by deposit accumulation.

[0022] Wide applicability: The adaptive clamping system enables rapid adaptation and continuous adjustment to different pipe diameters, improving the versatility and practicality of the device. Whether for small or large diameter nuclear pipelines, this invention provides stable and efficient cleaning results. This feature broadens the application range of this invention in nuclear facilities, meeting the cleaning needs of various nuclear facilities.

[0023] In summary, this invention achieves efficient, non-destructive, online cleaning of nuclear pipelines through the innovative combination of oblique incidence ultrasonic cleaning technology, acoustic wave control module, and adaptive clamping system. This invention not only improves cleaning efficiency and quality but also reduces the impact and risks of cleaning operations on nuclear facility operation. In the future, with the continuous development of nuclear power generation and nuclear facility operation, this invention will have even broader application prospects and market value. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a schematic diagram of the structure in which the acoustic wedge and the pipe clamp cooperate in this invention.

[0025] In the figure, 1-pre-tightening bolt, 2-front cover plate, 3-piezoelectric ceramic sheet, 4-rear cover plate, 5-acoustic wedge block, 6-pipe clamp, 7-metal pipe to be cleaned, 8-first shoulder block, 9-first hinge, 10-first frame, 11-second frame, 12-first pad block, 13-second pad block, 14-second shoulder block. Detailed Implementation

[0026] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings: This invention can be implemented in many different forms and should not be considered limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully express the scope of the invention to those skilled in the art. In the drawings, components are enlarged for clarity.

[0027] It should be understood that although the terms first, second, third, etc., may be used herein to describe various elements, components, and / or parts, these elements, components, and / or parts are not limited by these terms. These terms are merely used to distinguish elements, components, and / or parts from one another. Therefore, the first element, component, and / or part discussed below may be a second element, component, or part without departing from the teachings of this invention.

[0028] like Figure 1 As shown, the present invention discloses an online ultrasonic cleaning device for oblique incidence of metal pipes in nuclear power plants, including an ultrasonic transducer module, an acoustic wedge block, and a pipe clamp; The ultrasonic transducer module is used to excite longitudinal waves of ultrasonic frequency through longitudinal vibration, and includes a preload bolt, a front cover plate, a rear cover plate, and a piezoelectric component. The front cover plate is cylindrical, and a countersunk through hole for engaging with the pre-tightening bolt is provided at the center of one end face; The rear cover plate is a frustum, the diameter of the smaller end of its end face is equal to the diameter of the cross-section of the front cover plate, and the center of the smaller end face is provided with a first threaded blind hole for cooperating with the preload bolt. The piezoelectric component comprises 2N piezoelectric ceramic sheets; each piezoelectric ceramic sheet is annular in shape, with an outer diameter equal to the diameter of the front cover plate cross-section, and is polarized along the thickness direction; the 2N piezoelectric ceramic sheets are stacked sequentially, with the same polarization direction; The pre-tightening bolt passes through the countersunk hole and 2N piezoelectric ceramic plates in sequence on the front cover plate and is then threaded to the first threaded blind hole on the rear cover plate, clamping the piezoelectric assembly between the front cover plate and the rear cover plate. like Figure 2 As shown, the acoustic wedge is used to regulate the longitudinal wave emitted by the ultrasonic transducer module and transmit it to the metal pipe to be cleaned. It includes an inclined wall, an upper wall, a bottom wall, and a front wall, a first side wall, a rear wall, and a second side wall that are vertically connected end to end. The bottom wall of the acoustic wedge is provided with a groove for engaging with the metal pipe to be cleaned; The groove is a cylindrical curved surface with its axis perpendicular to the front wall of the acoustic wedge; The inclined wall of the acoustic wedge and the larger end face of the rear cover plate are coaxially fixed together. The first and second sidewalls of the acoustic wedge are respectively connected to the pipe clamp; like Figure 2 As shown, the pipe clamp is used to fix the acoustic wedge block to the metal pipe to be cleaned, and includes a first shoulder block, a second shoulder block, a first frame, a second frame, a first hinge, a second hinge, a first pad block, a second pad block, and an adjustable snap fastener. The first shoulder block and the second shoulder block have the same structure and are symmetrically arranged on both sides of the acoustic wedge block, respectively perpendicularly fixed to the first side wall and the second side wall of the acoustic wedge block. The first frame and the second frame have the same structure, both being L-shaped and each containing a long plate and a short plate, with one end of the long plate and one end of the short plate being perpendicularly fixed together. The other end of the first frame long plate is connected to the first shoulder block via the first hinge, and the other end of the short plate is connected to one end of the adjustable snap fastener; the other end of the second frame long plate is connected to the second shoulder block via the second hinge, and the other end of the short plate is connected to the other end of the adjustable snap fastener; the axis of rotation of the first hinge and the second hinge is parallel to the circumferential direction of the groove on the bottom wall of the acoustic wedge; The first pad and the second pad are respectively disposed on the inner walls of the first frame and the second frame, and are used to cooperate with the metal pipe to be cleaned; The adjustable snap fastener is used to connect or loosen the short plates of the first frame and the second frame, and to adjust the distance between the short plates of the first frame and the second frame when connecting, so that the groove on the bottom wall of the acoustic wedge, the first pad, the second pad and the metal pipe to be cleaned fit tightly, thereby fixing the acoustic wedge on the metal pipe to be cleaned.

[0029] The piezoelectric ceramic sheet is preferably made of PZT-8 piezoelectric ceramic sheet; the first and second pads are preferably made of polyurethane damping pads; the first and second hinges are preferably butterfly hinges; the acoustic wedge is preferably made of brass; the first and second shoulder blocks, the first frame, and the second frame are preferably made of 6061-T6 aluminum alloy. The inner walls at the connection between the long and short plates in the first and second frames are preferably chamfered.

[0030] The acoustic wedge has a threaded post at the center of its inclined wall, which is perpendicularly fixed to the inclined wall; the rear cover plate has a second threaded blind hole at the center of its larger end face for engaging with the threaded post; the threaded post and the second threaded blind hole fix the rear cover plate and the acoustic wedge together.

[0031] When setting the inclination angle of the acoustic wedge, it is numerically equal to the sound wave incident angle. The sound wave incident angle affects the sound intensity transmission coefficient and the propagation distance of the ultrasonic guided wave. According to the law of sound wave reflection and refraction, as the sound wave incident angle increases, the sound intensity transmission coefficient increases, and the ultrasonic guided wave propagation decreases. By plotting the curves of sound intensity transmission coefficient variation and ultrasonic guided wave propagation distance variation under different sound wave incident angles, the optimal sound wave incident angle, which is the inclination angle of the acoustic wedge, can be determined.

[0032] This invention achieves precise and efficient cleaning of deposits inside nuclear pipelines through the collaborative operation of an ultrasonic transducer module, an acoustic wedge, and a pipe clamp.

[0033] The ultrasonic transducer module is the power source of the device of this invention. Through the use of PZT-8 piezoelectric ceramic plates, the resonant frequency of the entire transducer is stabilized within the range of 25kHz ± 1kHz. This design not only ensures stable ultrasonic output but also significantly improves ultrasonic transmission efficiency. During the cleaning process, the ultrasonic transducer module generates strong longitudinal vibrations, which are converted into ultrasonic waves that propagate in the liquid medium, providing sufficient energy for subsequent cleaning operations.

[0034] The acoustic wedge employs a sound velocity gradient matching design, using a brass acoustic wedge to achieve ultrasonic mode conversion. The wedge's inclination angle, calculated according to the law of sound wave refraction, allows the longitudinal wave to penetrate the pipe wall at the optimal incident angle and trigger mode conversion within the pipe wall—that is, the longitudinal wave is converted into a transverse wave. This conversion process significantly improves the propagation efficiency and cleaning effect of the ultrasonic wave within the pipe wall.

[0035] The pipe clamp, through its first and second hinges and adjustable latches, enables rapid assembly, disassembly, and adaptive adjustment for pipes of different diameters. During cleaning, the clamp maintains a tight fit against the pipe surface, ensuring effective ultrasonic wave transmission and cleaning results. Furthermore, the clamp is equipped with polyurethane shock-absorbing pads to effectively attenuate mechanical vibration energy, protecting the pipe and surrounding structures. This design not only improves the versatility and practicality of the device but also reduces the impact of cleaning operations on nuclear facility operations.

[0036] In its specific implementation, this invention first uses a pipe clamp to fix the device to the metal pipe to be cleaned. Then, the ultrasonic transducer module generates ultrasonic waves, which are transmitted into the pipe through an acoustic wedge. Under the action of the acoustic wedge, the ultrasonic waves penetrate the pipe wall at an optimal incident angle and induce mode transitions, cleaning the deposits inside the pipe. During the cleaning process, the pipe clamp can closely conform to the surface of the metal pipe and maintain a stable cleaning effect. Simultaneously, the polyurethane vibration damping pads effectively attenuate mechanical vibration energy, protecting the safety of the pipe and surrounding structures.

[0037] This invention not only ensures the effective transfer of ultrasonic energy but also improves cleaning efficiency and uniformity, supporting online cleaning without downtime and significantly reducing maintenance time and costs for nuclear power plants. Simultaneously, by reducing the use of chemical reagents, it avoids corrosion of pipelines, extending their service life. Furthermore, by utilizing cavitation effects to remove dirt from crevices and deep pores, it effectively removes contaminants from hard-to-reach areas, making it suitable for pipeline cleaning in both active and decommissioned nuclear power plants. This invention offers advantages such as convenient operation, safety and reliability, and minimal secondary waste, making it particularly suitable for applications in demanding environments such as nuclear power plants.

[0038] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein.

[0039] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A nuclear power plant metal pipe oblique incidence ultrasonic online cleaning device, characterized in that, Includes ultrasonic transducer modules, acoustic wedges, and pipe clamps; The ultrasonic transducer module is used to excite longitudinal waves at ultrasonic frequencies through longitudinal vibration, and includes preload bolts, a front cover plate, a rear cover plate, and a piezoelectric assembly. The front cover plate is cylindrical, with a countersunk through hole at the center of one end face for engaging with the pre-tightening bolt; The rear cover plate is a frustum, and the diameter of the smaller end of its end face is equal to the diameter of the cross-section of the front cover plate. The center of the smaller end face is provided with a first threaded blind hole for cooperating with the preload bolt. The piezoelectric component comprises 2N piezoelectric ceramic sheets; the piezoelectric ceramic sheets are in the shape of a ring, with an outer diameter equal to the diameter of the front cover plate cross section, and are polarized along the thickness direction; the 2N piezoelectric ceramic sheets are stacked sequentially, with the same polarization direction; The pre-tightening bolts pass through the countersunk holes and 2N piezoelectric ceramic sheets on the front cover plate in sequence, and are then connected to the first threaded blind hole on the rear cover plate, clamping the piezoelectric assembly between the front cover plate and the rear cover plate. The acoustic wedge is used to regulate the longitudinal wave emitted by the ultrasonic transducer module and transmit it to the metal pipe to be cleaned. It includes an inclined wall, an upper wall, a bottom wall, and a front wall, a first side wall, a rear wall, and a second side wall that are vertically connected end to end. The bottom wall of the acoustic wedge has a groove for mating with the metal pipe to be cleaned; The groove is a cylindrical curved surface, with its axis perpendicular to the front wall of the acoustic wedge; The inclined wall of the acoustic wedge and the larger end face of the rear cover plate are coaxially fixed together; The first and second sidewalls of the acoustic wedge are connected to the pipe clamp, respectively. The pipe clamp is used to fix the acoustic wedge block to the metal pipe to be cleaned, and includes a first shoulder block, a second shoulder block, a first frame, a second frame, a first hinge, a second hinge, a first pad block, a second pad block, and an adjustable snap clamp. The first shoulder block and the second shoulder block have the same structure and are symmetrically arranged on both sides of the acoustic wedge block, respectively perpendicularly fixed to the first side wall and the second side wall of the acoustic wedge block. The first and second frames have the same structure, both being L-shaped and containing a long plate and a short plate, with one end of the long plate and one end of the short plate being perpendicularly fixed together. The other end of the long plate of the first frame is connected to the first shoulder block via the first hinge, and the other end of the short plate is connected to one end of the adjustable snap fastener; the other end of the long plate of the second frame is connected to the second hinge and the second shoulder block, and the other end of the short plate is connected to the other end of the adjustable snap fastener; the axis of rotation of the first hinge and the second hinge is parallel to the circumferential direction of the groove on the bottom wall of the acoustic wedge. The first pad and the second pad are respectively installed on the inner walls of the first frame and the second frame, and are used to cooperate with the metal pipe to be cleaned; The adjustable snap clamp is used to connect or loosen the short plates of the first frame and the second frame, and to adjust the distance between the short plates of the first frame and the second frame when connecting, so that the groove on the bottom wall of the acoustic wedge, the first pad, the second pad and the metal pipe to be cleaned fit tightly, thereby fixing the acoustic wedge on the metal pipe to be cleaned. The acoustic wedge adopts a sound velocity gradient matching design. The acoustic wedge made of brass is used to realize the mode conversion of ultrasonic waves. The inclination angle of the acoustic wedge is calculated by the law of sound wave refraction so that the longitudinal wave can penetrate the pipe wall at the optimal incident angle and excite mode conversion inside the pipe wall, that is, the longitudinal wave is converted into a transverse wave.

2. The nuclear power plant metal pipeline oblique incidence ultrasonic online cleaning device according to claim 1, characterized in that, The piezoelectric ceramic sheet used is PZT-8 piezoelectric ceramic sheet.

3. The nuclear power plant metal pipeline oblique incidence ultrasonic online cleaning device according to claim 1, characterized in that, The first and second pads are made of polyurethane shock-absorbing pads.

4. The nuclear power plant metal pipe oblique incidence ultrasonic online cleaning device according to claim 1, characterized in that, The inner walls at the joints between the long and short plates in the first and second frames are chamfered.

5. The oblique-incidence ultrasonic online cleaning device for metal pipes in nuclear power plants according to claim 1, characterized in that, Both the first and second hinges are butterfly hinges.

6. The nuclear power plant metal pipeline oblique incidence ultrasonic online cleaning device according to claim 1, characterized in that, The acoustic wedge is made of brass.

7. The nuclear power plant metal pipeline oblique incidence ultrasonic online cleaning device according to claim 1, characterized in that, The acoustic wedge has a threaded post at the center of its inclined wall that is perpendicularly fixed to the inclined wall; the rear cover plate has a second threaded blind hole at the center of its larger end face for engaging with the threaded post; the threaded post and the second threaded blind hole fix the rear cover plate and the acoustic wedge together.

8. The nuclear power plant metal pipeline oblique incidence ultrasonic online cleaning device according to claim 1, characterized in that, The first shoulder block, the second shoulder block, the first frame, and the second frame are all made of 6061-T6 aluminum alloy.

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