Vortex detection method and system for foreign matters on secondary side of steam generator, and processing terminal

Abstract

The invention relates to a steam generator secondary side foreign matter eddy current detection method and system and a processing terminal. The method comprises the following steps: acquiring a first eddy current signal; determining whether a suspicious object exists on the secondary side of the steam generator according to the first vortex signal; when the suspicious object exists, the axial position of the suspicious object is determined according to the first eddy current signal, and a second eddy current signal is obtained; determining whether the suspicious object is a foreign object according to the second eddy current signal; when the foreign matter exists, the circumferential fuzzy position of the foreign matter is determined according to the second eddy current signal, and the ferromagnetic type of the foreign matter can be determined according to the first eddy current signal; acquiring a third eddy current signal; and determining the circumferential accurate position of the foreign matter according to the third eddy current signal. Whether the foreign matter exists in the secondary side of the steam generator or not can be efficiently, comprehensively and accurately detected, and the accurate position of the foreign matter can be detected.

Description

Technical Field

[0001] This invention relates to the field of nuclear power plant steam generator maintenance technology, and in particular to a method and system for detecting foreign matter eddy currents on the secondary side of a steam generator, as well as a processing terminal. Background Technology

[0002] Foreign objects can be generated in nuclear power plant steam generators during manufacturing, maintenance, and operation. Foreign objects on the secondary side of the steam generator are one of the main causes of wear and degradation in heat transfer tubes. Therefore, during nuclear power plant shutdowns for maintenance, the secondary side sludge deposits are typically flushed with water first, followed by ITV video inspection. If foreign objects are found, they are removed using specialized tools; if removal is impossible, a technical assessment is conducted. However, flushing is rarely thorough in removing foreign objects. Due to the complex structure and limited space of the inspection area, ITV video inspection has blind spots, such as those around high-level support plates and flow dividers, which may prevent the detection of some foreign objects. Therefore, nuclear power plants urgently need a technical solution that can comprehensively and accurately scan the vicinity of each heat transfer tube for foreign objects and precisely locate them. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method and system for detecting foreign matter eddy currents on the secondary side of a steam generator, and a processing terminal.

[0004] The technical solution adopted by this invention to solve its technical problem is: constructing a method for detecting foreign matter eddy currents on the secondary side of a steam generator, comprising: Acquire a first eddy current signal; wherein, the first eddy current signal is an eddy current signal obtained by the eddy current probe probing the inside of the steam generator at an excitation frequency from low frequency to high frequency; Determine whether there are suspicious objects on the secondary side of the steam generator based on the first eddy current signal; When the suspicious object is present, the axial position of the suspicious object is determined based on the first eddy current signal, and a second eddy current signal is obtained; wherein, the second eddy current signal is the eddy current signal obtained by the eddy current probe detecting the suspicious object with an electromagnetic field that rotates at a low to high frequency and direction of excitation frequency near the axial position; Determine whether the suspicious object is a foreign object based on the second eddy current signal; When the foreign object is present, the circumferential fuzzy position of the foreign object is determined according to the second eddy current signal, and the ferromagnetic type of the foreign object is determined according to the first eddy current signal; Acquire a third eddy current signal; wherein, the third eddy current signal includes eddy current signals detected by the eddy current probe after applying additional magnetic fields in different directions at the circumferential ambiguity position; The precise circumferential position of the foreign object is determined based on the third eddy current signal.

[0005] Preferably, determining whether there are suspicious objects on the secondary side of the steam generator based on the first eddy current signal includes: A similarity analysis is performed between the first eddy current signal and historical eddy current signals to obtain a first similarity score characterizing the degree of similarity between the first eddy current signal and historical eddy current signals; wherein, the historical eddy current signals include the first eddy current signals obtained during previous nuclear power plant overhauls. Determine whether the first similarity is less than the first similarity threshold. If so, determine that there is a suspicious object on the secondary side of the steam generator.

[0006] Preferably, determining whether the suspicious object is a foreign object based on the second eddy current signal includes: A three-dimensional image is generated based on the second eddy current signal; Signal feature recognition is performed on the three-dimensional image to determine whether there are foreign objects.

[0007] Preferably, after determining the ferromagnetic type of the foreign object, the method further includes: Based on the three-dimensional image, the axial length and circumferential angle of the contact area between the foreign object and the corresponding heat transfer tube are determined to generate preliminary dimensional information of the foreign object.

[0008] Preferably, determining the ferromagnetic type of the foreign object includes: Acquire a non-ferromagnetic image library and a ferromagnetic image library; wherein, the non-ferromagnetic image library includes Lissajous figures of foreign objects of various non-ferromagnetic materials under different sizes, shapes and frequencies of excitation, and the ferromagnetic image library includes Lissajous figures of foreign objects of various ferromagnetic materials under different sizes, shapes and frequencies of excitation. In the first eddy current signal, the morphological changes of the eddy current signal acquired near the axial position from a set low frequency value to a set high frequency value are analyzed to obtain response data from the low frequency range to the high frequency range; wherein, the response data includes phase; The response range of the first eddy current signal is determined based on the response data; When the response range is in the low frequency range, the first eddy current signal is subjected to similarity analysis with the Lissajous figures included in the ferromagnetic image library in a polling manner to obtain several second similarities characterizing the degree of similarity between the first eddy current signal and the corresponding Lissajous figures. If at least one of the second similarity values ​​is greater than the second similarity threshold, it is determined that the foreign object contains a ferromagnetic foreign object. When the response range is in the mid-to-high frequency range, the first eddy current signal and the Lissajous figures included in the non-ferromagnetic image library are subjected to similarity analysis in a polling manner to obtain several third similarities that characterize the degree of similarity between the first eddy current signal and the corresponding Lissajous figures. If at least one of the third similarities is greater than the third similarity threshold, it is determined that the foreign object contains a non-ferromagnetic foreign object.

[0009] Preferably, the method for generating the non-ferromagnetic image library and the Lissajous figures in the ferromagnetic image library includes: The eddy current signal of the specimen is obtained by using a axially wound probe to detect the eddy current signal of a foreign object specimen with a specific material and size shape placed on the outer wall of the heat transfer tube of a steam generator at a specific excitation frequency. The Lissajous figure corresponding to the foreign object specimen is generated based on the eddy current signal of the specimen.

[0010] Preferably, determining the precise circumferential position of the foreign object based on the third eddy current signal includes: The intensity of the eddy current signal when the additional magnetic field is applied in different directions is compared based on the third eddy current signal. The orientation of the additional magnetic field when the eddy current signal intensity is at its maximum is determined based on the comparison results. The position between the applied direction and the eddy current probe that outputs the third eddy current signal is determined as the precise circumferential position of the foreign object.

[0011] Preferably, the method for acquiring the first eddy current signal includes: During the process of the axial probe passing through the heat transfer tube at a first set speed, the axial probe is controlled to operate at an excitation frequency from low frequency to high frequency in order to acquire the first eddy current signal. The method for acquiring the second eddy current signal includes: controlling the rotating probe to operate at an excitation frequency from low frequency to high frequency during the process of the rotating probe passing through the heat transfer tube at a second set speed, so as to acquire the second eddy current signal; the second set speed is less than the first set speed; The method for acquiring the third eddy current signal includes: controlling the axial probe placed at the circumferential ambiguity position to work when the magnetic field generating device is placed at different positions of the circumferential ambiguity position each time, so as to acquire the third eddy current signal; wherein, the magnetic field generating device includes an electromagnet or a strong magnetic probe made of permanent magnet material.

[0012] Furthermore, the present invention also constructs a processing terminal, which includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the above-described method for detecting foreign matter eddy currents on the secondary side of a steam generator.

[0013] Furthermore, the present invention also constructs a secondary-side foreign matter eddy current detection system for a steam generator, comprising: The processing terminal described above; A shaft-wound probe is used to acquire the first eddy current signal; A rotating probe is used to acquire the second eddy current signal; A magnetic field generating device is used in conjunction with an axially wound probe to acquire a third eddy current signal; wherein the magnetic field generating device includes an electromagnet or a strong magnetic probe made of permanent magnet material.

[0014] Implementing this invention has the following beneficial effects: it can efficiently, comprehensively, and accurately detect whether there are foreign objects in the secondary side of the steam generator, effectively reduce the risk of foreign object residue, detect the precise location of foreign objects, improve the efficiency of workers in cleaning foreign objects, and help improve the operational reliability and safety of the steam generator. Attached Figure Description

[0015] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings: Figure 1 This is a flowchart of the method for detecting foreign matter eddy currents on the secondary side of a steam generator in some embodiments of the present invention; Figure 2 This is a partial schematic diagram of the presence of foreign objects in a three-dimensional image in some embodiments of the present invention; Figure 3 This is a cross-sectional view of the axially wound probe and magnetic field generating device when acquiring the third eddy current signal in some embodiments of the present invention; Figure 4 This is a schematic diagram of the structure of the steam generator secondary side foreign object eddy current detection system in some embodiments of the present invention. Detailed Implementation

[0016] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0017] It should be noted that the flowcharts shown in the accompanying drawings are merely illustrative and do not necessarily include all content and operations / steps, nor do they necessarily have to be performed in the described order. For example, some operations / steps can be broken down, while others can be combined or partially combined; therefore, the actual execution order may change depending on the specific circumstances.

[0018] The block diagrams shown in the accompanying drawings are merely functional entities and do not necessarily correspond to physically independent entities. That is, these functional entities can be implemented in software, in one or more hardware modules or integrated circuits, or in different network and / or processor devices and / or microcontroller devices.

[0019] Figure 1This is a flowchart illustrating the eddy current detection method for foreign objects on the secondary side of a steam generator in some embodiments of the present invention. This eddy current detection method for foreign objects on the secondary side of a steam generator efficiently, comprehensively, and accurately detects the presence of foreign objects on the secondary side, effectively reducing the risk of foreign object residue, and accurately detecting the location of foreign objects, thereby improving the efficiency of personnel in cleaning foreign objects and enhancing the operational reliability and safety of the steam generator.

[0020] like Figure 1 As shown, the method for detecting foreign matter eddy currents on the secondary side of a steam generator may include steps S10 to S70.

[0021] Step S10: Acquire the first eddy current signal. The first eddy current signal is the eddy current signal obtained by the eddy current probe detecting the inside of the steam generator at excitation frequencies ranging from low to high frequency.

[0022] In some embodiments, the eddy current probe for acquiring the first eddy current signal can be an existing shaft-wound probe found in nuclear power plants. Shaft-wound probes are conventional tools for inspecting heat transfer tubes in steam generators, capable of quickly passing through the heat transfer tubes and performing eddy current detection during this process. Accordingly, the method for acquiring the first eddy current signal can include: controlling the shaft-wound probe to operate at an excitation frequency ranging from low to high frequency as it passes through the heat transfer tube at a first set speed, in order to acquire the first eddy current signal.

[0023] In this embodiment, an existing pusher (including an electric pusher, a pneumatic pusher, and a manual pusher) can be used to propel the axially wound probe through any heat transfer tube of the steam generator at a relatively fast speed (i.e., a first set speed). During the passage, the axially wound probe can simultaneously generate an alternating magnetic field ranging from a set low frequency value (e.g., 20kHz) to a set high frequency value (e.g., 700kHz), and detection is performed under the above conditions. The eddy current signal output by the axially wound probe during this period is recorded, thus obtaining the first eddy current signal. The purpose of this step is to achieve a rapid scan around the heat transfer tube that has been passed through, providing data support for subsequent steps to determine whether there are any suspicious objects.

[0024] Step S20: Determine whether there are any suspicious objects on the secondary side of the steam generator based on the first eddy current signal.

[0025] In some embodiments, steps S201 and S202 can be performed to determine whether there are suspicious objects on the secondary side of the steam generator.

[0026] Step S201: Perform a similarity analysis between the first eddy current signal and historical eddy current signals to obtain a first similarity score characterizing the degree of similarity between the first eddy current signal and historical eddy current signals. Historical eddy current signals include first eddy current signals acquired during previous nuclear power plant overhauls.

[0027] In this step, the first eddy current signal and the historical eddy current signal can be converted into curves respectively. Then, the existing algorithm is used to perform overlap analysis on the two curves to obtain the overlap degree (i.e., the first similarity) that can characterize the similarity between the first eddy current signal and the historical eddy current signal.

[0028] Alternatively, existing image analysis methods are used to compare the first eddy current signal with historical eddy current signals to extract abnormal waveforms in the first eddy current signal that differ from historical eddy current signals. The waveform with the largest peak value among all abnormal waveforms is extracted, and the negative number of the absolute value of the peak value of the waveform with the largest peak value is used as the first similarity.

[0029] Step S202: Determine whether the first similarity is less than the first similarity threshold. If so, determine that there is suspicious material on the secondary side of the steam generator. It should be noted that the first eddy current signal is the eddy current signal obtained by the eddy current probe scanning the inside of the steam generator (i.e., around the heat transfer tubes) at a relatively fast speed. It may be affected by external factors such as noise and sludge, and may result in false detections. Therefore, this step determines that there is suspicious material on the secondary side of the steam generator, which will be further confirmed in subsequent steps.

[0030] Step S30: When a suspicious object is present, determine the axial position of the suspicious object based on the first eddy current signal and obtain the second eddy current signal. The second eddy current signal is obtained by detecting the suspicious object passing through the heat transfer tube using an electromagnetic field with an excitation frequency and direction ranging from low to high frequency, near the axial position of the eddy current probe.

[0031] In this step, the eddy current probe can be placed within a range of 50mm in front to 50mm behind the axial position for scanning, thereby obtaining the second eddy current signal.

[0032] In some embodiments, the axial position of the suspect can be determined by: calculating the amplitude of the eddy current signal at each sampling point based on the first eddy current signal, taking the amplitude of the suspect signal (as an absolute value); and determining the axial position by the location of the eddy current probe that collected the first eddy current signal when the maximum amplitude was collected.

[0033] In some embodiments, the eddy current probe for acquiring the second eddy current signal can be an existing rotating probe in a nuclear power plant, namely a rotating field eddy current probe, which can automatically generate a rotating electromagnetic field. Accordingly, the method for acquiring the second eddy current signal includes: controlling the rotating probe to operate at an excitation frequency from low frequency to high frequency during the process of the rotating probe passing through the heat transfer tube at a second set speed, so as to acquire the second eddy current signal; the second set speed is less than the first set speed.

[0034] In this embodiment, a rotating probe can be moved at a slower speed (i.e., a second set speed) through a range of the axial position of the heat transfer tube traversed by the axial probe during the acquisition of the first eddy current signal (approximately 50 mm before and after the axial position). During this passage, the rotating probe can simultaneously generate an electromagnetic field ranging from a set low frequency value to a set high frequency value, and detection is performed under the aforementioned conditions. The eddy current signal output by the rotating probe during this period is recorded, thus obtaining the second eddy current signal. The purpose of this step is to achieve precise screening around the heat transfer tube through which the probe passes, to further determine whether the suspected object is a real foreign object or a false alarm, and to provide data support for the preliminary determination of the size, shape, and location of the foreign object. It should be noted that the acquisition of the second eddy current signal is time-consuming. However, this invention first acquires and determines the presence of a suspected object based on the first eddy current signal before acquiring the second eddy current signal. When it is determined based on the first eddy current signal that there is no suspected object around the corresponding heat transfer tube, the steps after S30 can be omitted, which helps to improve detection efficiency.

[0035] Step S40: Determine whether the suspicious object is a foreign object based on the second eddy current signal.

[0036] In some embodiments, steps S401 and S402 can be performed to determine whether the suspect is a foreign object.

[0037] Step S401: Generate a three-dimensional image based on the second eddy current signal.

[0038] In this step, the second eddy current signal is a three-dimensional eddy current signal, so it can be converted into a three-dimensional image using existing methods.

[0039] Step S402: Perform signal feature recognition on the three-dimensional image to determine whether there is a foreign object.

[0040] Figure 2 This is a partial schematic diagram showing the presence of foreign objects in a three-dimensional image in some embodiments of the present invention. In this step, the three-dimensional image can be compared with a three-dimensional image without foreign objects (such as a historical three-dimensional image or a three-dimensional image after the last removal of foreign objects) using existing image comparison methods to determine whether foreign objects are present.

[0041] Alternatively, a pre-trained foreign object recognition model can be used to identify signal features in 3D images to determine the presence of foreign objects. The training process for the foreign object recognition model may include: establishing an initial model based on a convolutional neural network; acquiring training data (including multiple 3D images with foreign objects and multiple 3D images without foreign objects); dividing the training data into a training set and a validation set according to a set ratio; training the initial model on the training set and validation set with the aim of learning how to identify whether foreign objects exist in 3D images, until the accuracy of the initial model's output reaches a preset accuracy threshold, thus obtaining a foreign object recognition model capable of identifying whether foreign objects exist in 3D images.

[0042] Step S50: When a foreign object is present, determine the circumferential fuzzy position of the foreign object based on the second eddy current signal, and determine the ferromagnetic type of the foreign object based on the first eddy current signal.

[0043] In this step, determining the ferromagnetic type of the foreign object provides important reference information for the method of removing it. For example, if the foreign object contains ferromagnetic material, its magnetism can be used to attract the foreign object out. Conversely, if the foreign object contains non-ferromagnetic material, clamping tools or other relevant tools are needed to clamp the foreign object out as much as possible.

[0044] In addition, the ferromagnetic types of foreign objects include those composed of ferromagnetic materials, those composed of non-ferromagnetic materials, and those composed of a mixture of ferromagnetic and non-ferromagnetic materials.

[0045] In some embodiments, the circumferential blur position of a foreign object can be determined by analyzing a three-dimensional image to determine the relative position of the foreign object, and then determining the circumferential blur position of the foreign object based on the relative position.

[0046] Alternatively, the circumferential fuzzy position of the foreign object can be determined by the following method: during the slow heat transfer process of the rotating probe, the intensity change amplitude of the second eddy current signal is monitored in real time, and when the intensity change amplitude (absolute value) of the second eddy current signal is greater than the set change threshold, the current position of the rotating probe is determined as the circumferential fuzzy position of the foreign object.

[0047] To improve the accuracy of the circumferential fuzzy position, after initially determining the circumferential fuzzy position, the rotating probe can be controlled to move forward and backward at the initially determined circumferential fuzzy position. During the forward and backward movement, the rotating probe is controlled to work. During this working period, the position where the amplitude of the second eddy current signal intensity change is the largest is determined as the final circumferential fuzzy position.

[0048] In some embodiments, the ferromagnetic type of the foreign object can be determined by performing steps S501 to S507.

[0049] Step S501: Obtain a non-ferromagnetic image library and a ferromagnetic image library. The non-ferromagnetic image library includes Lissajous figures of various non-ferromagnetic materials under different sizes, shapes, and frequencies of excitation. The ferromagnetic image library includes Lissajous figures of various ferromagnetic materials under different sizes, shapes, and frequencies of excitation.

[0050] In this step, each Lissajous figure is associated with a specific material, a specific size and shape, and a specific excitation frequency. That is, at least one of the following is different between different Lissajous figures: material (non-ferromagnetic or ferromagnetic), size and shape, and excitation signal frequency.

[0051] In some embodiments, Lissajous figures in the non-ferromagnetic and ferromagnetic libraries can be generated by: acquiring eddy current signals when a foreign object specimen with a specific material and size is placed on the outer wall of a heat transfer tube in a steam generator using an eddy current probe at a specific excitation frequency (20kHz to 700kHz), and obtaining the specimen eddy current signal; and generating the Lissajous figure corresponding to the foreign object specimen based on the specimen eddy current signal.

[0052] In the secondary side of a steam generator, common foreign matter includes materials such as iron, nickel, stainless steel, copper, aluminum, titanium, tin, zinc, and tungsten. Correspondingly, foreign matter test specimens can include specimens of various sizes and shapes made from these materials. By testing and collecting data from each of these specimens, non-ferromagnetic and ferromagnetic image libraries can be constructed. Furthermore, the conversion of eddy current signals to Lissajous figures is a mature technology, and existing conversion methods can be used to convert the eddy current signals of the test specimens into Lissajous figures.

[0053] Step S502: In the first eddy current signal, the morphological changes of the eddy current signal acquired at the axial position from a set low frequency value to a set high frequency value are analyzed to obtain response data from the low frequency range to the high frequency range; wherein, the response data includes phase.

[0054] In this step, the eddy current signal segment collected by the axial probe near the axial position of the foreign object can be captured first; then the morphological changes of the eddy current signal segment from the set low frequency value to the set high frequency value can be analyzed; finally, response data used to characterize the response degree from the low frequency range to the high frequency range can be obtained based on the analysis results.

[0055] Furthermore, the low-frequency range can be 20kHz to 100kHz, the mid-to-high frequency range can be 100kHz to 700kHz, with the high-frequency range being 300kHz to 700kHz and the mid-frequency range being 100kHz to 300kHz. Most non-ferromagnetic foreign matter exhibits a more pronounced response in the 100kHz to 300kHz range compared to the 300kHz to 700kHz range. This setting helps improve analytical accuracy, reduces the workload required for analysis, and increases analytical efficiency.

[0056] Step S503: Determine the response range of the first eddy current signal based on the response data.

[0057] In some embodiments, the step of determining the response range of the first eddy current signal based on the response data may include: determining whether the phase difference between the phase of the response data in the low-frequency range and the set phase is within the set phase deviation range; if so, determining that the response range of the first eddy current signal is in the low-frequency range; otherwise, determining that the response range of the first eddy current signal is in the mid-to-high frequency range.

[0058] Alternatively, the response data may also include amplitude. Accordingly, the step of determining the response range of the first eddy current signal based on the response data may further include: determining whether the amplitude of the response data in the low-frequency range is greater than a set amplitude; if so, determining that the response range of the first eddy current signal is in the low-frequency range; otherwise, determining that the response range of the first eddy current signal is in the mid-to-high frequency range.

[0059] Step S504: When the response interval is in the low frequency range, perform similarity analysis between the first eddy current signal and the Lissajous figures included in the ferromagnetic image library in a polling manner to obtain several second similarities that characterize the degree of similarity between the first eddy current signal and the corresponding Lissajous figures.

[0060] In this step, the method for determining the second similarity is similar to that for the first similarity. For details, please refer to the above text, which will not be repeated here.

[0061] Step S505: When there is at least one second similarity greater than the second similarity threshold, it is determined that the foreign object contains a ferromagnetic foreign object.

[0062] Step S506: When the response range is in the mid-to-high frequency range, perform similarity analysis between the first eddy current signal and the Lissajous figures included in the non-ferromagnetic image library in a polling manner to obtain several third similarity values ​​that characterize the degree of similarity between the first eddy current signal and the corresponding Lissajous figures.

[0063] In this step, the method for determining the third similarity is similar to that for the first similarity. For details, please refer to the above text, which will not be repeated here.

[0064] Step S507: When there is at least one third similarity greater than the third similarity threshold, it is determined that the foreign object contains a non-ferromagnetic foreign object.

[0065] Furthermore, when the foreign object contains only ferromagnetic foreign objects, it is determined that the foreign object is composed of ferromagnetic materials; when the foreign object contains only non-ferromagnetic foreign objects, it is determined that the foreign object is composed of non-ferromagnetic materials; when the foreign object contains both ferromagnetic and non-ferromagnetic foreign objects, it is determined that the foreign object is composed of a mixture of ferromagnetic and non-ferromagnetic materials; when the foreign object contains neither ferromagnetic nor non-ferromagnetic materials, a false positive signal indicating that the suspicious object is a misjudgment is output.

[0066] In some embodiments, after determining the ferromagnetic type of the foreign object, the method further includes the following step: determining the axial length and circumferential angle of the contact area between the foreign object and the corresponding heat transfer tube based on a three-dimensional image, to generate preliminary dimensional information of the foreign object. This preliminary dimensional information can assist personnel in selecting more suitable cleaning tools to remove the foreign object.

[0067] Step S60: Acquire the third eddy current signal. The third eddy current signal includes the eddy current signals detected by the eddy current probe after applying additional magnetic fields at different orientations at the circumferentially ambiguous position.

[0068] In some embodiments, a third eddy current signal can be acquired using a axially wound probe. Accordingly, the method for acquiring the third eddy current signal may include: controlling the axially wound probe positioned at a different orientation of the circumferential ambiguity position each time the magnetic field generating device is positioned, in order to acquire the third eddy current signal.

[0069] In this embodiment, the axially wound probe is first moved to the circumferentially ambiguous position of the heat transfer tube being tested. Then, the axially wound probe is controlled to operate at a specific frequency (if the foreign object contains only ferromagnetic material, the frequency in the low-frequency range is preferred; if the foreign object contains only non-ferromagnetic material, the frequency in the mid-frequency range is preferred). Then, the magnetic field generating device is placed in the heat transfer tube at least in four positions closest to the heat transfer tube being tested, and the magnetic field generating device is made as close as possible to the circumferentially ambiguous position. Then, after each placement of the magnetic field generating device, eddy current signals are collected by the axially wound probe. The eddy current signals collected when the magnetic field generating device is placed in different positions are combined to obtain the third eddy current signal.

[0070] In some embodiments, the magnetic field generating device includes an electromagnet or a strong magnetic probe made of a permanent magnet material (such as neodymium iron boron), which can generate a strong magnetic field.

[0071] It should be noted that in step S60, the shaft-wound probe performs data acquisition with a fixed excitation voltage and a fixed excitation frequency.

[0072] Step S70: Determine the precise circumferential position of the foreign object based on the third eddy current signal.

[0073] In some embodiments, steps S701 to S703 may be performed to determine the precise circumferential position of the foreign object.

[0074] Step S701: Compare the intensity of the eddy current signal when the additional magnetic field is applied in different directions based on the third eddy current signal.

[0075] In one specific embodiment, when acquiring the third eddy current signal, the magnetic field generating device is placed in four different orientations, as detailed in [reference needed]. Figure 3 , Figure 3 In the diagram, 2 represents a wound-rotor probe, 4 represents a magnetic field generating device, 5 represents a foreign object, and 6 represents a heat transfer tube. Figure a shows a cross-sectional view of the first placement orientation, Figure b shows a cross-sectional view of the second placement orientation, Figure c shows a cross-sectional view of the third placement orientation, and Figure d shows a cross-sectional view of the fourth placement orientation. Understandably, the function of step S701 is to compare the intensity of the eddy current signals detected by the wound-rotor probe under the four test environments shown in Figures a to d.

[0076] In some embodiments, the magnetic field generating device can be moved within the heat transfer tube by a pusher to the desired position for acquiring the third eddy current signal.

[0077] Step S702: Determine the application orientation of the additional magnetic field when the eddy current signal intensity is maximum based on the comparison results. In this step, among all eddy current signals collected under different orientations where additional magnetic fields are applied, the location of the magnetic field generating device corresponding to the signal with the maximum eddy current signal intensity is determined as the application orientation.

[0078] Step S703: Determine the precise circumferential position of the foreign object by the position between the applied direction and the eddy current probe that outputs the third eddy current signal.

[0079] It should be noted that, in Figure 3 In the embodiment shown, under the influence of an additional magnetic field, the eddy current signal measured by the axial probe is the largest under the test environment shown in Figure d. Therefore, it can be determined that the foreign object is sandwiched between the axial probe and the magnetic field generating device.

[0080] In some embodiments, when the first similarity is greater than or equal to the first similarity threshold or a false alarm signal is obtained, it is determined that there are no suspicious objects around the heat transfer tube through which the axial probe passes when the first eddy current signal is obtained. Further, when it is determined that there are no suspicious objects around the current heat transfer tube, another heat transfer tube can be selected as the detection target, and steps S10 to S60 are executed.

[0081] The present invention also provides a processing terminal, such as Figure 4As shown, the processing terminal includes a memory, a processor, and a computer program stored in the memory and capable of running on the processor. When the processor executes the computer program, it implements the steam generator secondary side foreign object eddy current detection method provided in this embodiment of the invention.

[0082] This invention also provides a secondary-side foreign object eddy current detection system for steam generators, such as... Figure 4 As shown, the system includes a axially wound probe 2, a rotating probe 3, a magnetic field generating device 4, and a processing terminal 1 provided in this embodiment of the invention.

[0083] The axial-wound probe 2 is used to acquire the first eddy current signal. The rotating probe 3 is used to acquire the second eddy current signal. The magnetic field generating device 4 is used in conjunction with the axial-wound probe to acquire the third eddy current signal.

[0084] In some embodiments, the magnetic field generating device includes an electromagnet or a strong magnetic probe made of permanent magnet material.

[0085] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0086] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0087] The steps of the methods or algorithms described in conjunction with the embodiments disclosed herein can be implemented directly by hardware, a software module executed by a processor, or a combination of both. The software module can be located in random access memory (RAM), main memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art.

[0088] It is understood that the above embodiments only illustrate preferred embodiments of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can freely combine the above technical features without departing from the concept of the present invention, and can also make several modifications and improvements, all of which fall within the protection scope of the present invention. Therefore, all equivalent transformations and modifications made with respect to the scope of the claims of the present invention should fall within the scope of the claims of the present invention.

Claims

1. A method for detecting foreign matter eddy currents on the secondary side of a steam generator, characterized in that, include: Acquire a first eddy current signal; wherein, the first eddy current signal is an eddy current signal obtained by the eddy current probe probing the inside of the steam generator at an excitation frequency from low frequency to high frequency; Determine whether there are suspicious objects on the secondary side of the steam generator based on the first eddy current signal; When the suspicious object is present, the axial position of the suspicious object is determined based on the first eddy current signal, and a second eddy current signal is obtained; wherein, the second eddy current signal is the eddy current signal obtained by the eddy current probe detecting the suspicious object with an electromagnetic field that rotates at a low to high frequency and direction of excitation frequency near the axial position; Determine whether the suspicious object is a foreign object based on the second eddy current signal; When the foreign object is present, the circumferential fuzzy position of the foreign object is determined according to the second eddy current signal, and the ferromagnetic type of the foreign object is determined according to the first eddy current signal; Acquire a third eddy current signal; wherein, the third eddy current signal includes eddy current signals detected by the eddy current probe after applying additional magnetic fields in different directions at the circumferential ambiguity position; The precise circumferential position of the foreign object is determined based on the third eddy current signal.

2. The method for detecting foreign matter eddy currents on the secondary side of a steam generator according to claim 1, characterized in that, The step of determining whether there are suspicious objects on the secondary side of the steam generator based on the first eddy current signal includes: A similarity analysis is performed between the first eddy current signal and historical eddy current signals to obtain a first similarity score characterizing the degree of similarity between the first eddy current signal and historical eddy current signals; wherein, the historical eddy current signals include the first eddy current signals obtained during previous nuclear power plant overhauls. Determine whether the first similarity is less than the first similarity threshold. If so, determine that there is a suspicious object on the secondary side of the steam generator.

3. The method for detecting foreign matter eddy currents on the secondary side of a steam generator according to claim 1, characterized in that, The step of determining whether the suspicious object is a foreign object based on the second eddy current signal includes: A three-dimensional image is generated based on the second eddy current signal; Signal feature recognition is performed on the three-dimensional image to determine whether there are foreign objects.

4. The method for detecting foreign matter eddy currents on the secondary side of a steam generator according to claim 3, characterized in that, After determining the ferromagnetic type of the foreign object, the process further includes: Based on the three-dimensional image, the axial length and circumferential angle of the contact area between the foreign object and the corresponding heat transfer tube are determined to generate preliminary dimensional information of the foreign object.

5. The method for detecting foreign matter eddy currents on the secondary side of a steam generator according to claim 1, characterized in that, Determining the ferromagnetic type of the foreign object includes: Acquire a non-ferromagnetic image library and a ferromagnetic image library; wherein, the non-ferromagnetic image library includes Lissajous figures of foreign objects of various non-ferromagnetic materials under different sizes, shapes and frequencies of excitation, and the ferromagnetic image library includes Lissajous figures of foreign objects of various ferromagnetic materials under different sizes, shapes and frequencies of excitation. In the first eddy current signal, the morphological changes of the eddy current signal acquired near the axial position from a set low frequency value to a set high frequency value are analyzed to obtain response data from the low frequency range to the mid-high frequency range; wherein, the response data includes phase; The response range of the first eddy current signal is determined based on the response data; When the response range is in the low frequency range, the first eddy current signal is subjected to similarity analysis with the Lissajous figures included in the ferromagnetic image library in a polling manner to obtain several second similarities characterizing the degree of similarity between the first eddy current signal and the corresponding Lissajous figures. If at least one of the second similarity values ​​is greater than the second similarity threshold, it is determined that the foreign object contains a ferromagnetic foreign object. When the response range is in the mid-to-high frequency range, the first eddy current signal and the Lissajous figures included in the non-ferromagnetic image library are subjected to similarity analysis in a polling manner to obtain several third similarities that characterize the degree of similarity between the first eddy current signal and the corresponding Lissajous figures. If at least one of the third similarities is greater than the third similarity threshold, it is determined that the foreign object contains a non-ferromagnetic foreign object.

6. The method for detecting foreign matter eddy currents on the secondary side of a steam generator according to claim 5, characterized in that, The method for generating the nonferromagnetic image library and the Lissajous figures in the ferromagnetic image library includes: The eddy current signal of the specimen is obtained by using a axially wound probe to detect the eddy current signal of a foreign object specimen with a specific material and size shape placed on the outer wall of the heat transfer tube of a steam generator at a specific excitation frequency. The Lissajous figure corresponding to the foreign object specimen is generated based on the eddy current signal of the specimen.

7. The method for detecting foreign matter eddy currents on the secondary side of a steam generator according to claim 1, characterized in that, Determining the precise circumferential position of the foreign object based on the third eddy current signal includes: The intensity of the eddy current signal when the additional magnetic field is applied in different directions is compared based on the third eddy current signal. The orientation of the additional magnetic field when the eddy current signal intensity is at its maximum is determined based on the comparison results. The position between the applied direction and the eddy current probe that outputs the third eddy current signal is determined as the precise circumferential position of the foreign object.

8. The method for detecting foreign matter eddy currents on the secondary side of a steam generator according to any one of claims 1 to 7, characterized in that, The method for acquiring the first eddy current signal includes: During the process of the axial probe passing through the heat transfer tube at a first set speed, the axial probe is controlled to operate at an excitation frequency from low frequency to high frequency in order to acquire the first eddy current signal. The method for acquiring the second eddy current signal includes: controlling the rotating probe to operate at an excitation frequency from low frequency to high frequency during the process of the rotating probe passing through the heat transfer tube at a second set speed, so as to acquire the second eddy current signal; the second set speed is less than the first set speed; The method for acquiring the third eddy current signal includes: controlling the axial probe placed at the circumferential ambiguity position to work when the magnetic field generating device is placed at different positions of the circumferential ambiguity position each time, so as to acquire the third eddy current signal; wherein, the magnetic field generating device includes an electromagnet or a strong magnetic probe made of permanent magnet material.

9. A processing terminal comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steam generator secondary side foreign object eddy current detection method as described in any one of claims 1 to 8.

10. A secondary-side foreign object eddy current detection system for a steam generator, characterized in that, include: The processing terminal as described in claim 9; A shaft-wound probe is used to acquire the first eddy current signal; A rotating probe is used to acquire the second eddy current signal; A magnetic field generating device is used in conjunction with an axially wound probe to acquire a third eddy current signal; wherein the magnetic field generating device includes an electromagnet or a strong magnetic probe made of permanent magnet material.

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