Eddy current device and method for performing fuel channel inspection

Abstract

A device and method for performing eddy current testing of a fuel channel. The eddy current testing device includes an array of eddy current sensors positioned along the outer circumference of a non-rotating section. The device is inserted into the pressure tube, and the active coils of the eddy current sensors are driven in a certain operating pattern, and data is collected from a reference coil of the eddy current sensors in a certain collection pattern. The relative arrangement of the eddy current sensors, the relative arrangement of the active coil and reference coil of each eddy current sensor, the operating pattern, and the collection pattern may be configured to reduce crosstalk and / or to maximize sensor coverage of the pressure tube area between adjacent eddy current sensors.

Description

Technical Field

[0001] Related Application Data This application claims priority to U.S. Provisional Patent Application No. 63 / 495,900, a related application filed on April 13, 2023. The provisional patent application is incorporated herein by reference.

[0002] The present disclosure relates to devices and methods for non-destructive inspection of metal conduits, and more particularly to devices and methods for non-destructive inspection of nuclear fuel channels using eddy current sensors.

Background Art

[0003] Non-destructive methods for inspecting metallic materials are known in the art and have been used for inspecting pipes and other conduits, including metallic fuel channels used in nuclear power plants. Eddy current sensors (also known as gap sensors or eddy current transducers) are a known technique for determining various characteristics of a conduit based on the electrical and magnetic properties of a local region of the metallic conduit. Conventional eddy current inspection uses a conductive coil ("active coil") carrying an alternating current that is positioned in a spatially proximate relationship to a local region of the conduit. This coil generates a magnetic field that varies over time corresponding to the alternating current. The time-varying magnetic field induces eddy currents in the local region of the conduit, and a second coil ("reference coil") detects changes in the phase and amplitude of these eddy currents.

[0004] Alternatively, changes in the amount of current flowing through the active coil can be monitored. Depending on the conductivity and / or permeability of the conduit material, changes over time in the phase and amplitude of the current flowing through the active coil can occur.

[0005] In the context of nuclear fuel channel inspection, existing approaches to eddy current inspection use a tool fitted with a rotating eddy current sensor array to inspect the inside of the fuel channel. Each fuel channel comprises a pressure tube (PT) supported inside a calandria tube (also called a sleeve) by end fitting modules and a centering module. The rotating tool is inserted into the pressure tube, and the eddy current sensors, positioned on the external surface of the tool facing the internal surface of the pressure tube, rotate along the inner circumference of the pressure tube as the tool is inserted or withdrawn axially, sensing eddy currents in a helical pattern along the inner circumference of the pressure tube as it moves along the axial direction of the pressure tube. [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, the rotational motion of this tool used in existing approaches generates certain artifacts, which limit the accuracy of the inspection data generated by the tool and restrict data acquisition efficiency. Firstly, the rotational motion of the tool may cause vibrations of the tool within the pressure tube. Secondly, the rotational motion of the tool may cause vibrations of the pressure tube within the calandria tube. Thirdly, the rotational design of the tool limits the number of eddy current sensors that can be incorporated, which may result in spatial gaps in the data and / or slower data acquisition.

[0007] Therefore, it is desirable to provide a device for performing eddy current testing of fuel channels that overcomes one or more of the limitations of existing approaches. [Means for solving the problem]

[0008] This disclosure describes devices and methods for performing eddy current testing of fuel channels in various examples. In some embodiments, the eddy current testing device comprises an array of eddy current sensors positioned along the outer periphery of a non-rotating section. Each eddy current sensor comprises an active coil and one or more reference coils. The device is inserted into the pressure tube, the active coil of the eddy current sensor is driven in a certain operating pattern, and data is collected from the reference coil of the eddy current sensor in a certain collection pattern. The relative arrangement of the eddy current sensors, the relative arrangement of the active coil and reference coil of each eddy current sensor, the operating pattern, and the collection pattern may be configured to reduce crosstalk and / or to maximize sensor coverage of the pressure tube area between adjacent eddy current sensors.

[0009] In some embodiments, the device uses a reference coil to detect several characteristics of the back electromotive force (EMF) caused by the wall thickness and resistivity of the pressure tube and / or calandria tube. By measuring the impedance change with the reference coil, the wall thickness, wall material, and / or the gap distance between the outer surface of the pressure tube and the inner surface of the calandria tube can be determined.

[0010] In some embodiments, the device may be equipped with more eddy current sensors along the lower arc of the device's circumference than along the upper arc of the device's circumference, in order to improve the resolution of the data collected with respect to the lower part of the pressure tube. Such improved resolution helps to detect the deflection of the pressure tube within the calandria tube, which would pose a risk of the lower outer surface of the pressure tube coming into contact with the lower inner surface of the calandria tube.

[0011] In some embodiments, the active coil of the eddy current sensor may be equipped with a ferrite core for concentrating the magnetic field, which may allow the magnetic field to penetrate deeper into and through the pressure pipe material.

[0012] This disclosure describes a device for inspecting a metal conduit in several exemplary embodiments. The device comprises a body configured to be inserted into an internal cavity of a pressure tube along the axial direction of the pressure tube of a fuel channel; a plurality of eddy current sensors, each eddy current sensor comprising an active coil fixed to the body at a respective circumferential position along the circumference of the body and oriented to induce eddy currents in each operating circumferential portion of the internal surface of the pressure tube, and one or more reference coils, each oriented to measure a magnetic field with respect to each reference circumferential portion of the pressure tube; a control circuit configured to actuate the active coils according to an operating pattern so that each active coil induces eddy currents at each of a plurality of axial positions of each operating circumferential portion of the pressure tube; and a data acquisition circuit configured to acquire magnetic field data from each reference coil according to an acquisition pattern so that magnetic field data is collected from each reference coil with respect to each of a plurality of axial positions of each reference circumferential portion of the pressure tube.

[0013] In another embodiment, the device has a plurality of centering modules, each fixed to the main body at a circumferential position along the circumference of the main body, and these centering modules are configured to cooperate to radially center the device with respect to the inner surface of the pressure tube.

[0014] The operating and acquisition patterns may be configured to mitigate crosstalk from multiple active coils in the magnetic field data acquired from the reference coil. These patterns may be configured to generate magnetic field data that can be processed to interpolate the magnetic field data relating to the circumferential portion of the pressure tube between a pair of eddy current sensors.

[0015] In one embodiment, the data acquisition circuit is further configured to determine the wall thickness of the pressure tube at one or more locations by processing magnetic field data acquired from a reference coil. In another embodiment, the data acquisition circuit is further configured to determine the wall material composition based on the resistivity of the pressure tube at one or more locations by processing magnetic field data acquired from a reference coil. In a further embodiment, the data acquisition circuit is further configured to determine one or more distances between the device and one or more locations on the inner surface of the pressure tube by processing magnetic field data acquired from a reference coil.

[0016] The device may be configured to be positioned within the internal cavity of the calandria tube of the fuel channel, and the data acquisition circuit may be further configured to determine the width of the gap between the outer surface of the pressure tube and the inner surface of the calandria tube by processing magnetic field data acquired from a reference coil.

[0017] A tether may be attached to the main unit and comprises a communication link operably coupled to the control circuit and data acquisition circuit, and a power link for supplying power to the active coil. The communication link may include an optical communication link. The control circuit may be configured to receive control data from the communication link and to actuate the active coil according to an operating pattern based on the control data. The control data may be multiplexed control data. The control circuit may include an optical demodulator for receiving the multiplexed optical control data.

[0018] The data acquisition circuit may be configured to process magnetic field data acquired from a reference coil to generate inspection data and transmit the inspection data over a communication link. The inspection data may include multiplexed inspection data. The data acquisition circuit includes an optical modulator for transmitting the multiplexed optical inspection data.

[0019] Furthermore, a method for inspecting a fuel channel is taught. The method includes inserting a device having a plurality of eddy current sensors into an internal cavity of a pressure tube of the fuel channel along an axial direction of the pressure tube, each eddy current sensor being fixedly oriented toward a respective circumferential portion of an inner surface of the pressure tube; displacing the device in the axial direction; operating each active coil according to an operating pattern such that each active coil of each eddy current sensor induces eddy currents at respective ones of a plurality of axial positions along each circumferential portion of the pressure tube during this step of displacing the device in the axial direction; and collecting magnetic field data from at least one reference coil of each eddy current sensor according to a collection pattern such that the magnetic field data is collected from each reference coil at respective ones of a plurality of axial positions along each circumferential portion of the pressure tube.

[0020] Hereinafter, reference will be made by way of example to the accompanying drawings showing exemplary embodiments of the present application.

Brief Description of the Drawings

[0021] [Figure 1] A left front perspective view of an eddy current inspection device according to an example of the present disclosure. [Figure 2] A front cross-sectional elevation view of an eddy current sensor section of the eddy current inspection device of FIG. 1. [Figure 3A] A front cross-sectional elevation view of an eddy current sensor section of a second example of the eddy current inspection device of FIG. 1. [Figure 3B] A front cross-sectional elevation view of an eddy current sensor section of a third example of the eddy current inspection device of FIG. 1. [Figure 4] A front cross-sectional elevation view of a calandria tube, a pressure tube, and an eddy current sensor section of FIG. 2 showing an eddy current inspection device inserted inside the pressure tube. [Figure 5A] A front view of a first example of an eddy current sensor according to an example of the present disclosure. [Figure 5B] A front view of a second example of an eddy current sensor according to an example of the present disclosure. [Figure 6]A flowchart showing steps of an example method for performing an eddy current inspection of a fuel channel according to an example of the present disclosure. **DETAILED DESCRIPTION OF THE INVENTION**

[0022] Like reference numerals may be used to indicate like components in different figures.

[0023] The present disclosure describes examples of devices and methods for performing an eddy current inspection of a fuel channel using a device having a plurality of eddy current sensors disposed along a circumferential portion of a non-rotating section.

[0024] FIG. 1 shows an eddy current inspection device 100. The device 100 has a body comprising a front section 106, an eddy current sensor section 104, and a rear section 102. The device 100 has an elongate shape and is configured to be inserted into the internal cavity of the pressure tube of the fuel channel with the front section 106 leading.

[0025] The illustrated device 100 includes a tether 114 that extends from a rear opening of the pressure tube for communicating with a device outside the fuel channel. The tether 114 may include a communication link (e.g., an electrical communication link or an optical communication link, etc.) for bidirectional communication with an external data processing device and / or a power link for supplying power from an external power source.

[0026] The illustrated device 100 includes a centering module 110 on a front section 106 and a rear section 102. Multiple centering modules 110 may be provided at each of one or more axial positions, for example, three centering modules 110 may be provided at three positions equidistant in the circumferential direction around a first axial position of the rear section 102, and the other three centering modules 110 may be provided at three positions equidistant in the circumferential direction around a second axial position of the front section 106. The centering modules 110 may be operable to center the device 100 radially within the circular internal cavity of the pressure pipe, for example, by extending radially outward from the device body using an actuator, or by being biased radially outward by a biasing means such as a spring. The centering module 110 may include rollers 112 to assist in the axial displacement of the device 100 within the pressure pipe, and in some embodiments, the rollers 112 can be actuated (e.g., using an electric motor or hydraulics) to actively displace the device 100 axially within the pressure pipe. In some embodiments, the front section 106 may be absent, and the eddy current sensor section 104 may constitute the head (i.e., the foremost portion) of the device 100. In some such embodiments, a set of centering modules 110 may be positioned at two or more axially spaced positions on the rear section 102 to assist in centering and stabilizing the tool within the conduit.

[0027] The eddy current sensor section 104 of device 100 comprises a plurality of eddy current sensors 108. Each eddy current sensor 108 is fixed to the eddy current sensor section 104 at its respective circumferential position around the body of device 100. Such positioning of the eddy current sensors 108 allows each sensor 108 to sense the resulting magnetic field in the corresponding circumferential portion inside the pressure tube or other metal conduit that is to be inspected for inducing eddy currents. When device 100 is displaced axially (i.e., along the length of the pressure tube or conduit) within the conduit without rotation, each sensor 108 generates magnetic field data for the axial strip or multiple axial positions of each circumferential portion of the conduit, traversing the axial length of each circumferential portion of the inner surface of the conduit.

[0028] Figure 2 is a front cross-sectional view of an eddy current sensor section 104 of an example eddy current inspection device. Section 104 includes a measurement core 202 which has a circuit for controlling the eddy current sensors 108 and collecting magnetic field data from the eddy current sensors 108. In the example of the embodiment shown in Figure 2, the eddy current sensors 108 are uniformly arranged along the circumference of the device 100 so that each eddy current sensor 108 is positioned to inspect a circumferential portion of a conduit of the same size (i.e., an equilateral arc).

[0029] Each eddy current sensor 108 comprises an active coil and one or more reference coils (i.e., passive sensing coils or receiving coils). In a preferred embodiment, each eddy current sensor 108 comprises one active / transmitting coil and two passive / receiving / reference coils. These active coils are actuated by passing current through some or all of the active coils to induce eddy currents in each circumferential portion of the inner surface of the pressure tube. The actuation of the active coils may be carried out according to a time-varying actuation pattern, which may be controlled using an electrical control signal. Similarly, the passive coils may collect magnetic field data from each circumferential portion of the inner surface of the pressure tube according to a time-varying collection pattern. Depending on the configuration of each sensor 108, as described hereafter with reference to Figures 5A to 5B, the circumferential portion of the conduit stimulated by the active coil of a given sensor 108 may be the same section or a different section of the circumferential portion of the conduit monitored by one or more passive coils of that given sensor 108.

[0030] The electrical link 206 connects each sensor 108 to the measurement core 202. The measurement core 202 may include a circuit configured to transmit control signals to the active coils of the sensors 108 via the electrical link 206 according to an operating pattern. Similarly, the measurement core 202 may include a circuit configured to collect magnetic field data from the passive coils of the sensors 108 via the electrical link 206 according to an acquisition pattern.

[0031] The measurement core 202 may comprise one or more circuit components, such as one or more printed circuit boards (PCBs) and / or application-specific integrated circuits (ASICs). In some embodiments, the measurement core 202 comprises optical modulators and / or optical demodulators, such as electro-optical modulators (EOMs) and / or photodiodes, for performing conversions between electrical signals and the optical domain. In some embodiments, the communication link of the tether 114 (see Figure 1) may be an optical link. In some examples, the measurement core 202 may comprise a control circuit, which may be configured to receive control data (such as multiplexed optical signal data) from the tether 114 and to actuate an active coil according to an operating pattern based on the received control data. In some examples, the measurement core 202 may comprise a data acquisition circuit configured to receive magnetic field data from a reference coil according to an acquisition pattern and to transmit test data (such as multiplexed optical signal data) via the tether 114 based on the magnetic field data. The control data may be generated by a control device located outside the conduit and transmitted to the device 100 via the tether 114. The inspection data is received via the tether 114 by a data processing device located outside the conduit and can be processed for analysis. In some embodiments, the control data and inspection data are multiplexed and communicated bidirectionally (i.e., control data to device 100 and inspection data from device 100) via a multiplexed communication link or bidirectional communication link, such as an optical communication link or a telecommunications link.

[0032] In some embodiments, the tether 114 may further include a power link for supplying external power from an external power source to the sensor 108 and / or other powered components of the device 100 (e.g., to the actuated centering module 110 and / or roller 112). In some embodiments, the device 100 may include an internal power source for supplying power to one or more of its powered components.

[0033] The example device 100 shown in Figure 2 comprises 24 eddy current sensors 108 uniformly arranged along the circumference of the eddy current sensor section 104. By providing a large number of eddy current sensors 108, such as 12 or more sensors 108 or 24 or more sensors 108, the device 100 can eliminate the need to rotate while inspecting the conduit, thereby eliminating the undesirable ration artifacts mentioned above and improving the accuracy of the inspection data.

[0034] Figure 3A shows an eddy current sensor section 104A of a second example of the eddy current inspection device 100. Here, the eddy current sensors 108 are unevenly arranged along the circumference of the device 100. In some embodiments, the lower portion 304 of the device 100 may have a higher density of sensors 108 than the upper portion 302 of the device 100. A greater number of sensors 108 along the lower portion 304 allows for the generation of higher resolution and more accurate inspection data with respect to the corresponding lower part of the conduit. This can be desirable for detecting pressure tube deflection in a calandria tube, as will be further detailed later with reference to Figure 4. Pressure tube deflection can be caused by a combination of gravity, misalignment of the centering module within the calandria tube, and degradation of the pressure tube material, which poses a risk of the pressure tube coming into contact with the calandria tube, and furthermore, this can cause serious safety and integrity issues if not detected and mitigated.

[0035] Figure 3B shows an eddy current sensor section 104A of a third example of the eddy current inspection device 100. Here again, the eddy current sensors 108 are unevenly distributed along the circumference of the device 100. In some embodiments, the lower 90-degree arc portion 305 of the device 100 may have a higher density of sensors 108 than the lateral 90-degree arc portion 306 of the device 100, and the upper 90-degree arc portion 308 of the device 100 may have a lower density of sensors 108 than the lateral 90-degree arc portion 306 of the device 100. A greater number of sensors 108 located along the lower portion 304 allows for the generation of higher resolution and more accurate inspection data with respect to the corresponding lower part of the conduit. This can be desirable for detecting the deflection of a pressure tube within a calandria tube, as will be further detailed later with reference to Figure 4. Pressure tube deflection can be caused by a combination of gravity, misalignment of the centering module within the calandria tube, and degradation of the pressure tube material, posing a risk of the pressure tube coming into contact with the calandria tube, which, if not detected and mitigated, could lead to serious safety and integrity issues.

[0036] Figure 4 is a front cross-sectional view of the eddy current testing device 100, showing the calandria tube 402, pressure tube 404, and eddy current sensor section 104 of the eddy current testing device 100 inserted inside the pressure tube 404. When in operation, a centering module 110 (not shown) of the device 100 centers the device 100 radially within the pressure tube 404 so that the eddy current sensor 108 is in contact with or very close to the inner surface 408 of the pressure tube 404. When the active coil of the sensor 108 is activated according to the operating pattern and magnetic field data is collected by the reference coil of the sensor 108, an inverse EMF is generated due to the wall thicknesses and resistivity of the pressure tube 404 and the calandria tube 402. The magnetic field data collected by the reference coil and / or changes in current passing through the active coil can be used to detect multiple characteristics of the pressure tube 404 and / or the calandria tube based on changes in impedance. For example, it is possible to detect changes in the wall thickness, material composition, and shape of the pressure tube 404 and / or the calandria tube 402, and furthermore, to detect the width of the gap 406 between the inner surface 412 of the calandria tube 402 and the outer surface 410 of the pressure tube 404.

[0037] In some examples, an eddy current inspection device 100, such as the embodiment shown in Figure 3A, may be used to inspect a fuel channel. Because the eddy current sensor section 104A of the device 100 has more eddy current sensors 108 in its lower portion 304 than in its upper portion 302, the resolution of the magnetic field data collected with respect to the lower portion 416 of the pressure tube 404, the gap 406, and the calandria tube 402 may be higher than the resolution of the magnetic field data collected with respect to the upper portion 414 of the pressure tube 404. This may improve the device 100's ability to detect deflection of the pressure tube 404 located inside the calandria tube 402.

[0038] Figure 5A shows the configuration of a first example of a single eddy current sensor 108 having a single active coil 502 and two reference coils 504 and 506. In this embodiment, the first reference coil 504 is spaced apart from the second reference coil 506 with respect to the circumferential direction 510. Furthermore, both coils of the reference coils 504 and 506 are displaced from the position of the active coil 502 with respect to the circumferential direction 510. Thus, the centerline 514 of the first reference coil 504 (i.e., the line passing through the axial center of the coil 504) defines the first circumferential portion of the pressure tube or other conduit having its center at the centerline 514. The magnetic field data collected by the first reference coil 504 can be considered as spatial data relating to the circumferential region centered at the centerline 514. Similarly, the centerline 516 of the second reference coil 506 (i.e., the line passing through the axial center of the coil 506) defines a second circumferential portion of a pressure pipe or other conduit centered on the centerline 516, and the magnetic field data collected by the second reference coil 506 can be considered as spatial data relating to a circumferential region centered on the centerline 516. The active coil 502 has a centerline 512, which defines the center point of the circumferential region of the conduit stimulated by the magnetic field 508 generated by the active coil 502, thereby generating eddy currents and creating a unique magnetic field that can be sensed by the reference coils 504, 506 and / or by current fluctuations in the active coil 502.

[0039] Figure 5B shows the configuration of a second example of an eddy current sensor 108 having a single active coil 502 and a single reference coil 504. In this embodiment, the reference coil 504 shares a common centerline 512 with the active coil 502, and therefore the circumferential portion of the conduit stimulated by the active coil 502 and the circumferential portion of the conduit monitored by the reference coil 504 are the same circumferential portion.

[0040] In addition to the configurations shown in Figures 5A and 5B, it will be understood that other configurations of the eddy current sensor 108 are also possible. For example, in some embodiments, the two reference coils 504 and 506 of the sensor 108 may be displaced from each other radially rather than circumferentially (with respect to the conduit). That is, the active coil 502 and both reference coils 504 and 506 share a common centerline 512, and the first reference coil 504 may be positioned closer to the inner surface 408 of the pressure tube than the second reference coil 506.

[0041] The reference coils of adjacent eddy current sensors 108 can be positioned to maximize the circumferential coverage of the magnetic field measurement. In some examples, the magnetic field measurement between adjacent reference coils of eddy current sensors 108 can be estimated by interpolating the magnetic field measurement of the reference coil as represented in the magnetic field data.

[0042] In some examples, the operating pattern of the active coils 502 of the set of sensors 108 is configured to reduce or minimize crosstalk from multiple active coils 502. For example, this operating pattern may operate only active coils 502 that are not adjacent at a given time point. In a device 100 having 24 sensors 108 numbered sequentially from 0 to 23 in a clockwise direction along the circumference of the device 100, this operating pattern may first operate all odd-numbered active coils 502 in the first epoch, then deactivate all odd-numbered active coils 502 in the second epoch to allow the magnetic field to attenuate, then operate all even-numbered active coils 502 in the third epoch, then deactivate all even-numbered active coils 502 in the fourth epoch, and then displace the device 100 axially to perform a new set of measurements at a new axial position of the device 100 (e.g., using an actuated roller 112). Similarly, the reference coil acquisition pattern may be configured to acquire magnetic field data from all or a subset of reference coils during each epoch, depending on the possibility that a given subset of reference coils may encounter interference during a given epoch of the operating pattern, the need for more magnetic field data in a given subset of the circumferential portion of the conduit, and limitations on data compression and transmission of the measurement core 202 and tether 114. In some examples, depending on factors such as the spacing between sensors 108, sensors 108 may be activated every three or every four instead of every other sensor 108 during a given epoch.

[0043] In some examples, multiple different electrical signal frequencies may be used to drive the active coil 502 during some or all epochs of this operating pattern. Both high and low frequencies may be used in the same or different epochs. For example, one operating pattern may increase the resolution of the magnetic field data by driving a subset of the active coil 502 with a high-frequency sinusoidal signal (e.g., 6 kHz or 8 kHz) during a first epoch, but at the cost of reduced penetration into the material of the pressure tube 404. This operating pattern may achieve deeper penetration into the material of the pressure tube 404 by driving a subset of the active coil 502 with a low-frequency sinusoidal signal (e.g., 2 kHz or 4 kHz) during a second epoch, but at the cost of some reduction in the resolution of the magnetic field data. In some embodiments, it will be understood that by using multiple different frequencies, such as sinusoidal signals of 2, 4, 6, and 8 kHz, multiple different trade-offs between penetration and resolution can be achieved.

[0044] In some embodiments, the active coil 502 can penetrate further into the material of the pressure tube 404 and / or calandria tube 402 by using a ferrite core to concentrate or focus the magnetic field 508.

[0045] In some embodiments, the operation patterns and acquisition patterns, and more generally the operation of the measurement core 202 and sensor 108, are configured to compensate for various types of interference. The local resistivity of the pressure tube 404 varies, which affects the induced eddy currents, and therefore the secondary impedance of the pressure tube 404 is measured. In some examples, variations in secondary impedance can be compensated for by using a higher frequency drive signal (e.g., 32 kHz) as part of the operation pattern to measure variations in the secondary impedance and / or local resistivity of the pressure tube 404 (and / or calandria tube). The wall thickness of the pressure tube 404 also affects the perceived impedance variation. Variations in the wall thickness of the pressure tube 404 may be detected using other techniques, such as ultrasonic testing, which may be incorporated into the device 100 in some embodiments. The impedance changes caused by the material resistance and wall thickness of the pressure tube 404 may be compensated for the interaction of multiple operating patterns and collection patterns, for example, compensation may be performed for both the interaction between the operation of the active coil 502 and the measurement by the first reference coil 504, and the interaction between the operation of the active coil 502 and the measurement by the second reference coil 506. Other changes in the impedance of both coil pairs (502 and 504, 502 and 506) can be inferred to be caused by the proximity of the calandria tube 402 to the pressure tube 404 (i.e., reduction in the width of the gap 406). This inference may be calibrated against a baseline by using a calibration sample (e.g., a fuel channel having a pressure tube and a calandria tube having known material composition, shape, and spacing, and therefore having a gap 406 of known width between these two objects 404, 408).

[0046] In some embodiments, the active coil 502 and / or reference coil may be relatively large in size. The relatively large size of these coils, combined with the spacing of those coils along the circumference of the eddy current sensor section 104, allows for the use of various drive frequencies and coil operation / acquisition combinations that maintain spatial resolution despite the axial movement of the device 100 in the conduit to be inspected, while also achieving accurate measurements.

[0047] In some embodiments, coils in adjacent sensors 108 in the circumferential direction may be used to obtain additional impedance measurements in the circumferential direction, i.e., between individual sensors 108, for example, by interpolating between measurements obtained from individual sensors 108.

[0048] In some examples, an operating pattern utilizing the alternating operation of a subset of active coils 502 and / or alternating acquisition from a subset of reference coils within a given epoch may be used to assist in the multiplexing of signals used to drive the active coils and / or data acquired from the reference coils. In some embodiments, this multiplexing of control data and / or magnetic field data may allow for a reduction in the number of conductors in the device 100 (e.g., the number of electrical links 206 and / or the number of conductors in the measurement core 202). However, in some such embodiments, since the system impedance is inherent to each electrical link 206 and can affect high eddy currents, the measurements processed by the measurement core 202 may need to be balanced with each change in the operating pattern and / or acquisition pattern (e.g., after each epoch).

[0049] Figure 6 shows the steps of an example method 600 for performing eddy current testing of a fuel channel. This method 600 is described with reference to the eddy current testing device 100. However, it will be understood that other means may be used to carry out the steps of method 600.

[0050] In step 602, the device 100, which includes multiple eddy current sensors 108, is inserted into the internal cavity of the pressure tube 404 of the fuel channel along the axial direction of the pressure tube 404. Each eddy current sensor 108 is fixedly oriented toward its respective circumferential portion of the internal surface 408 of the pressure tube 404.

[0051] In step 604, the device is displaced in the axial direction (i.e., either pulled out or inserted).

[0052] In step 606, the active coil 502 of each eddy current sensor 108 is operated according to an operating pattern so as to induce eddy currents at each of several axial positions along each circumferential portion of the pressure tube 404.

[0053] In step 608, magnetic field data is collected from at least one reference coil 504, 506 of each eddy current sensor 108 according to a collection pattern, so that magnetic field data is collected from each reference coil 504, 506 for each of a plurality of axial positions along each circumferential portion of the pressure tube 404.

[0054] This disclosure describes methods and processes having steps performed in a particular order, but one or more steps of these methods and processes may be omitted or modified as appropriate. One or more steps may be performed in a different order than those described as appropriate.

[0055] While this disclosure describes a method at least in part, it will be understood by those skilled in the art that it also describes various components for carrying out at least some of the aspects and features of the described method. Furthermore, these various components may be implemented by hardware components, software, or any combination thereof. Thus, the technical solutions of this disclosure may be embodied in the form of a software product. A suitable software product may be stored on a pre-recorded storage device or other similar non-volatile or non-temporary computer-readable medium, including, for example, a DVD, CD-ROM, USB flash disk, removable hard disk, or other storage medium. The software product tangibly stores instructions that cause a processing device (e.g., a personal computer, server, or network device) to execute an example of the method disclosed herein.

[0056] This disclosure may be embodied in other specific forms without departing from the subject matter of the claims. The exemplary embodiments described should be considered in all respects to be illustrative and not limiting. Alternative embodiments not expressly described may be produced by combining features selected from one or more of the embodiments described above, and features suitable for such combinations will be understood within the scope of this disclosure.

[0057] Any numerical values ​​and partial ranges within the disclosed scope are also disclosed. Furthermore, while the systems, devices, and processes disclosed and illustrated herein may comprise a certain number of elements / components, these systems, devices, and assemblies may be modified to comprise additional or reduced numbers of such elements / components. For example, while any element / component in this disclosure may be referred to as singular, embodiments disclosed herein may be modified to comprise multiple such elements / components. The subject matter described herein is intended to encompass and include any appropriate technical modifications. [Explanation of Symbols]

[0058] 100 Eddy Current Testing Devices 102 Rear section 104 Eddy current sensor section 104A Eddy Current Sensor Section 106 Front Section 108 Eddy current sensor 110 Centering Module 112 Laura 114 Tether 202 measurement cores 206 Electrical Link 302 Upper part 304 Lower part 402 Calandria tube 404 pressure pipe 406 Gap 408 Inner surface of a pressure tube 410 External surface 412 Internal surface 414 Upper part 416 Lower part 502 Active Coil 504 First reference coil 506 Second reference coil 508 Magnetic field 510 Circumferential direction 512 Center line 514 Center line 516 Centerline

Claims

1. A device for inspecting metal conduits, A main body configured to be inserted into the internal cavity of the pressure pipe along the axial direction of the pressure pipe of the fuel channel, Multiple eddy current sensors, each eddy current sensor being fixed to the main body at its respective circumferential position along the circumference of the main body, An active coil oriented to induce eddy currents in each operating circumferential portion of the inner surface of the pressure tube, and One or more reference coils, each oriented to measure the magnetic field with respect to each reference circumferential portion of the pressure tube. Multiple eddy current sensors equipped with, A control circuit is configured to operate the active coils according to an operating pattern such that each active coil induces an eddy current at each of a plurality of axial positions in the respective operating circumferential portion of the pressure tube, A data acquisition circuit configured to acquire magnetic field data from a reference coil according to an acquisition pattern such that magnetic field data is collected from each reference coil with respect to each of a plurality of axial positions of each of the reference circumferential portions of the pressure tube, and A device equipped with the following features.

2. A plurality of centering modules, each fixed to the main body at a circumferential position along the circumference of the main body, configured to cooperate in centering the device radially with respect to the inner surface of the pressure tube. The device according to claim 1, further comprising:

3. The one or more reference coils of each eddy current sensor are Two reference coils oriented to measure the magnetic field with respect to each of the two reference circumferential portions of the pressure tube. The device according to claim 1 or 2, comprising:

4. The device according to any one of claims 1 to 3, wherein the operating pattern and the acquisition pattern are configured to reduce crosstalk from a plurality of active coils in the magnetic field data acquired from the reference coil.

5. The device according to any one of claims 1 to 4, wherein the operating pattern and the collection pattern are configured to generate magnetic field data that can be processed to interpolate magnetic field data relating to the circumferential portion of the pressure tube between a pair of eddy current sensors.

6. The device according to any one of claims 1 to 5, wherein at least one of the active coils comprises a ferrite core.

7. The lower part of the main body defining the 180-degree arc portion below the pressure tube is equipped with a first number of eddy current sensors, The upper portion of the main body defining the 180-degree arc portion above the pressure pipe is equipped with a second number of eddy current sensors. The device according to any one of claims 1 to 6, wherein the second number is less than the first number.

8. The lower part of the main body defining the 90-degree arc portion below the pressure pipe is equipped with a first number of eddy current sensors, The upper part of the main body defining the 90-degree arc portion above the pressure pipe is equipped with a second number of eddy current sensors, Each of the two lateral portions of the main body that define the 90-degree arc portion to the side of the pressure pipe is equipped with a third number of eddy current sensors. The device according to any one of claims 1 to 6, wherein the second number is less than the third number, and the third number is less than the first number.

9. The device according to any one of claims 1 to 8, wherein the plurality of eddy current sensors comprises approximately 24 eddy current sensors.

10. The device according to any one of claims 1 to 9, wherein each of the plurality of eddy current sensors comprises one transmitting coil and two receiving coils.

11. The device according to any one of claims 1 to 10, wherein the data acquisition circuit is further configured to determine the wall thickness of the pressure tube at one or more locations by processing the magnetic field data acquired from the reference coil.

12. The device according to any one of claims 1 to 11, wherein the data acquisition circuit is further configured to determine the wall material composition based on the resistivity of the pressure tube at one or more locations by processing the magnetic field data acquired from the reference coil.

13. The device according to any one of claims 1 to 12, wherein the data acquisition circuit is further configured to determine one or more distances between the device and one or more locations on the inner surface of the pressure tube by processing magnetic field data acquired from the reference coil.

14. The device is configured to be positioned within the internal cavity of the calandria tube of the fuel channel, The device according to any one of claims 1 to 13, wherein the data acquisition circuit is further configured to determine the width of the gap between the outer surface of the pressure tube and the inner surface of the calandria tube by processing the magnetic field data acquired from the reference coil.

15. A tether attached to the aforementioned main unit, A communication link operably coupled to the control circuit and the data acquisition circuit, A power link for supplying power to the active coil Equipped with a tether The device according to any one of claims 1 to 14, further comprising the above.

16. The device according to claim 15, wherein the communication link includes an optical communication link.

17. The aforementioned control circuit is The control data is received from the aforementioned communication link. The active coil is operated according to the operating pattern based on the control data. The device according to claim 15 or 16, further configured as follows.

18. The device according to claim 17, wherein the control data includes multiplexed control data.

19. The aforementioned communication link includes an optical communication link. The multiplexed control data includes multiplexed optical control data, The device according to any one of claims 15 to 18, wherein the control circuit includes an optical demodulator that receives the multiplexed optical control data.

20. The aforementioned data acquisition circuit is The magnetic field data collected from the reference coil is processed to generate inspection data. The inspection data is transmitted over the aforementioned communication link. The device according to any one of claims 1 to 19, configured as follows.

21. The device according to claim 20, wherein the inspection data includes multiplexed inspection data.

22. The aforementioned communication link includes an optical communication link. The multiplexed inspection data includes multiplexed optical inspection data, The device according to claim 21, wherein the data acquisition circuit includes an optical modulator for transmitting the multiplexed optical inspection data.

23. A method for inspecting fuel channels, A step of inserting a device including a plurality of eddy current sensors into the internal cavity of the pressure tube of the fuel channel along the axial direction of the pressure tube, wherein each eddy current sensor is fixedly oriented toward the respective circumferential portion of the internal surface of the pressure tube; A step of displacing the device in the axial direction, During the step of displacing the device in the axial direction, The steps include: operating each active coil of each eddy current sensor according to an operating pattern such that each active coil of each eddy current sensor induces eddy currents at each of a plurality of axial positions along each circumferential portion of the pressure pipe; The steps include: collecting magnetic field data from at least one reference coil of each eddy current sensor according to a collection pattern, such that magnetic field data is collected from each reference coil for each of a plurality of axial positions along each circumferential portion of the pressure tube; Methods that include...

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