Zirconium-based cladding substrate thickness and conductivity measurement method based on sweep frequency eddy current

Abstract

The invention provides a frequency sweep eddy current-based zirconium-based cladding substrate thickness and conductivity measurement method, which comprises the following steps of: establishing an eddy current analysis theoretical model based on two manufactured detection coils, parameters of a zirconium-based cladding and inductive reactance change measurement data of the coils; high-frequency inductive reactance changes of the coils under different lift-off distances are obtained, and the lift-off value of each detection coil is calculated according to the lift-off distance fitting curve; setting a lift-off value, obtaining low-frequency inductive reactance changes of the coil under different substrate thicknesses, and calculating the substrate thickness according to a substrate thickness fitting curve; and setting the thickness of the substrate, obtaining the low-frequency inductive reactance change of the coil under different substrate conductivities, and calculating the substrate conductivity according to the substrate conductivity fitting curve. According to the method, the thickness and the conductivity of the zirconium-based cladding substrate can be measured at the same time, the accuracy and the diversity of zirconium-based cladding measurement results are improved, and the corrosion state of the zirconium-based cladding can be effectively evaluated.

Description

Technical Field

[0001] The present application relates to the technical field of electromagnetic eddy current detection, and in particular to a method for measuring the thickness and electrical conductivity of a zirconium-based cladding substrate based on swept-frequency eddy current. Background Art

[0002] Currently, zirconium-based fuel cladding serves as the first pressure boundary and safety barrier in nuclear reactors, effectively preventing the escape of nuclear fission products while dissipating heat and protecting the fuel from cooling corrosion. Although zirconium-based cladding exhibits excellent corrosion resistance, prolonged service in the extreme environments of high temperature, high pressure, strong neutron irradiation, and high cooling water velocity can lead to the formation of heterogeneous film structures such as oxide films and hydrogen absorption layers on its surface. These structures can even cause fuel defects, severely impacting the structural strength and performance of fuel assemblies and potentially leading to nuclear fuel assembly failure. Therefore, regular inspection of the condition of in-service zirconium-based nuclear fuel cladding is a crucial step in ensuring its safe operation.

[0003] In the prior art, zirconium-based fuel cladding inspections typically focus solely on measuring the thickness of the oxide film on the cladding. However, the complex heterogeneous film structure and electromagnetic properties of zirconium-based cladding significantly impact the inspection methods used in prior art. Consequently, the inspection results can be subject to significant errors, and the resulting data is often relatively unreliable, making it difficult to meet practical requirements.

[0004] Therefore, how to accurately and comprehensively measure the zirconium-based cladding to achieve an effective evaluation of its status has become an urgent problem that needs to be solved. Summary of the Invention

[0005] The present application aims to solve one of the technical problems in the related art at least to a certain extent.

[0006] To this end, the first purpose of this application is to propose a method for measuring the base thickness and conductivity of zirconium-based cladding based on swept-frequency eddy current. This method evaluates the corrosion state of the zirconium-based cladding by measuring the thickness and conductivity of the zirconium-based cladding layer, and improves the accuracy and diversity of the zirconium-based cladding measurement results through non-contact and high-sensitivity detection means.

[0007] The second object of this application is to propose a device for measuring the thickness and conductivity of the zirconium-based cladding substrate based on swept-frequency eddy current;

[0008] A third object of the present application is to provide a non-transitory computer-readable storage medium.

[0009] To achieve the above objectives, the first aspect of the present application is to propose a method for measuring the thickness and conductivity of a zirconium-based cladding substrate based on swept-frequency eddy current, the method comprising the following steps:

[0010] Two coaxial eddy current detection coils with identical geometric parameters were fabricated and placed above the zirconium-based cladding and in the air, respectively. A swept frequency excitation signal was applied to the two detection coils, and the change in inductive reactance was calculated based on the measurement results.

[0011] Based on the parameters of the two detection coils and the zirconium-based cladding, as well as the inductive reactance change measurement data, a multi-layer structure eddy current analytical theoretical model is established;

[0012] The model is used to obtain the change in high-frequency inductive reactance of the coil at different lift-off distances, and a linear fit is performed on the lift-off distance and the real part logarithm of the high-frequency inductive reactance change. The lift-off value of each detection coil is calculated based on the obtained lift-off distance fitting curve;

[0013] Setting the lift-off value in the model, obtaining the change in low-frequency inductive reactance of the coil under different substrate thicknesses, performing exponential fitting on the ratio of the substrate thickness to the imaginary part of the change in low-frequency inductive reactance, and calculating the substrate thickness of the zirconium-based cladding based on the obtained substrate thickness fitting curve;

[0014] The substrate thickness is set in the model, the low-frequency inductive reactance change of the coil under different substrate conductivities is obtained, and a linear fit is performed on the substrate conductivity and the imaginary part of the current low-frequency inductive reactance change. The substrate conductivity of the zirconium-based cladding is calculated based on the obtained substrate conductivity fitting curve.

[0015] Optionally, in one embodiment of the present application, calculating the change in inductive reactance based on the measurement results includes: measuring the impedance of each of the detection coils, and calculating the inductive reactance of each of the detection coils based on the impedance and the frequency of the swept frequency excitation signal; and performing differential processing on the calculated inductive reactance data to obtain the change in inductive reactance.

[0016] Optionally, in one embodiment of the present application, the low-frequency inductive reactance change is calculated in the model by the following formula:

[0017]

[0018] Where ΔL0 is a variable related to the coil size, ω is the excitation frequency, μ0 is the vacuum permeability, σ is the substrate conductivity, α0 is the spatial resolution, and c is the substrate thickness.

[0019] Optionally, in one embodiment of the present application, obtaining the high-frequency inductive reactance change of the coil at different lift-off distances includes: setting a high-frequency frequency and a plurality of lift-off distance values of the detection coil; respectively calculating the coil inductive reactance change corresponding to each lift-off distance value at the high-frequency frequency; and the lift-off distance fitting curve is expressed by the following formula:

[0020] ln(ReΔL(ω1))=al+b

[0021] Where ω1 is the high-frequency frequency, ΔL(ω1) is the change in high-frequency inductive reactance of the coil, and a and b are real numbers, a<0, b<0.

[0022] Optionally, in one embodiment of the present application, obtaining the low-frequency inductive reactance change of the coil under different substrate thicknesses includes: setting the low-frequency frequency and multiple substrate thicknesses of the zirconium-based cladding; respectively calculating the ratio of the imaginary part of the low-frequency inductive reactance change corresponding to each substrate thickness at the low-frequency frequency; the substrate thickness fitting curve is expressed by the following formula:

[0023] |ImΔL1(ω2) / ImΔL2(ω2)|=k1e αt +m1

[0024] Where ω2 is the low-frequency frequency, ΔL1(ω2) is the low-frequency inductive reactance change of the upper coil, ΔL2(ω2) is the low-frequency inductive reactance change of the lower coil, k1, α, and m1 are real numbers, k1>0, α<0, m1>0.

[0025] Optionally, in one embodiment of the present application, obtaining the low-frequency inductive reactance change of the coil under different substrate conductivities includes: setting multiple substrate conductivities of the zirconium-based cladding, and respectively calculating the imaginary part of the low-frequency inductive reactance change of the upper coil corresponding to each substrate conductivity at the low frequency; the substrate conductivity fitting curve is expressed by the following formula:

[0026] ImΔL1(ω2)=k2σ+m2

[0027] Among them, k2 and m2 are real numbers, k2<0, m2<0.

[0028] Optionally, in one embodiment of the present application, the high frequency is used to reduce the eddy current skin depth, the low frequency is used to increase the eddy current skin depth, the high frequency is greater than or equal to 1 MHz, and the low frequency is less than or equal to 1 kHz.

[0029] Optionally, in one embodiment of the present application, the geometric parameters of the detection coil include the inner diameter, outer diameter, height and number of turns of the coil.

[0030] Optionally, in one embodiment of the present application, the substrate and coating of the zirconium-based cladding are both non-ferromagnetic conductive materials, and the thickness of the substrate is much greater than the thickness of the coating.

[0031] To achieve the above objectives, the second aspect of the present application further proposes a device for measuring the thickness and conductivity of a zirconium-based cladding substrate based on swept-frequency eddy current, comprising the following modules:

[0032] A setting module is used to make two coaxial eddy current detection coils with the same geometric parameters, place the two detection coils above the zirconium-based cladding and in the air respectively, apply a swept frequency excitation signal to the two detection coils, and calculate the change in inductive reactance based on the measurement results;

[0033] Establishing a module for establishing a multi-layer structure eddy current analytical theoretical model based on the parameters of the two detection coils and the zirconium-based cladding, and the inductive reactance change measurement data;

[0034] a lift-off calculation module, configured to obtain the change in high-frequency inductive reactance of the coil at different lift-off distances using the model, perform a linear fit on the lift-off distance and the real part logarithm of the change in high-frequency inductive reactance, and calculate the lift-off value of each detection coil based on the obtained lift-off distance fitting curve;

[0035] a thickness measurement module, configured to set the lift-off value in the model, obtain the change in low-frequency inductive reactance of the coil under different substrate thicknesses, perform exponential fitting on the ratio of the substrate thickness to the imaginary part of the change in low-frequency inductive reactance, and calculate the substrate thickness of the zirconium-based cladding based on the obtained substrate thickness fitting curve;

[0036] A conductivity measurement module is used to set the substrate thickness in the model, obtain the low-frequency inductive reactance change of the coil under different substrate conductivities, perform linear fitting on the substrate conductivity and the imaginary part of the current low-frequency inductive reactance change, and calculate the substrate conductivity of the zirconium-based cladding based on the obtained substrate conductivity fitting curve.

[0037] To achieve the above-mentioned purpose, the third aspect embodiment of the present application further proposes a non-temporary computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, it implements the method for measuring the thickness and electrical conductivity of the zirconium-based cladding substrate based on swept-frequency eddy current as described in any one of the above-mentioned first aspects.

[0038] The technical solution provided by the embodiment of the present application brings at least the following beneficial effects: the present application first uses the high-frequency band of the sweep frequency excitation to measure the lift-off distance from the coil to the surface of the zirconium-based cladding, which is not affected by the properties of the zirconium-based cladding such as the conductivity; and then further measures the thickness and conductivity of the zirconium-based cladding layer in the low-frequency band. The adopted measurement method is highly operable and accurate. Therefore, the present application can simultaneously measure the thickness and conductivity of the zirconium-based cladding layer, can directly reflect the corrosion state of the cladding body, avoids the decoupling analysis of the complex characteristics of the heterogeneous film layer, is easy to operate, and has reliable detection results, which has practical engineering value. Therefore, the present application improves the accuracy and diversity of the zirconium-based cladding measurement results, can effectively evaluate the state of the zirconium-based cladding, and is conducive to the normal operation of the zirconium-based cladding.

[0039] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0041] Figure 1 A flow chart of a method for measuring the thickness and conductivity of a zirconium-based cladding substrate based on swept-frequency eddy currents proposed in an embodiment of the present application;

[0042] Figure 2 A schematic diagram of a coil inductive reactance change curve under a swept frequency excitation according to an embodiment of the present application;

[0043] Figure 3 A schematic diagram of a lift-off distance relationship curve proposed in an embodiment of the present application;

[0044] Figure 4 A schematic diagram of a substrate thickness relationship curve proposed in an embodiment of the present application;

[0045] Figure 5 A schematic diagram of a substrate conductivity relationship curve proposed in an embodiment of the present application;

[0046] Figure 6 A flowchart of a specific method for measuring the thickness and conductivity of a zirconium-based cladding substrate based on swept-frequency eddy currents proposed in an embodiment of the present application;

[0047] Figure 7 This is a schematic diagram of the structure of a device for measuring the thickness and electrical conductivity of a zirconium-based cladding substrate based on swept-frequency eddy currents proposed in an embodiment of the present application. DETAILED DESCRIPTION

[0048] The following describes embodiments of the present invention in detail, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and are not to be construed as limiting the present invention.

[0049] It should be noted that eddy current testing is a nondestructive testing method based on the principle of electromagnetic induction. By applying an alternating magnetic field to the metal conductor being tested, eddy currents are generated within it. The distribution and changes of these eddy currents are then analyzed to assess the material's properties and structural integrity. This technology offers advantages such as fast testing speed and high sensitivity. Therefore, this application utilizes swept-frequency eddy current testing for zirconium-based cladding testing.

[0050] The following describes in detail with reference to the accompanying drawings a method and device for measuring the thickness and electrical conductivity of a zirconium-based cladding substrate based on swept-frequency eddy currents proposed in an embodiment of the present application.

[0051] Figure 1 This is a flow chart of a method for measuring the thickness and conductivity of a zirconium-based cladding substrate based on swept-frequency eddy currents proposed in an embodiment of the present application, as shown in FIG. Figure 1 As shown, the method includes the following steps:

[0052] Step S101 , manufacturing two coaxial eddy current detection coils with the same geometric parameters, placing the two detection coils above the zirconium-based cladding and in the air respectively, applying a swept frequency excitation signal to the two detection coils, and calculating the inductive reactance change based on the measurement results.

[0053] Specifically, two coaxial eddy current detection coils are made. The geometric parameters of the two coils are exactly the same, and only the distance from the zirconium-based cladding is different. Therefore, when a sweep frequency excitation signal is applied to the coils at the same time, eddy currents can be induced on the surface of the zirconium-based cladding.

[0054] In one embodiment of the present application, the geometric parameters of the detection coil include the inner diameter r1, outer diameter r2, height h1 and number of turns N of the coil. The zirconium-based cladding substrate and coating are both non-ferromagnetic conductive materials, and the substrate thickness is much greater than the coating thickness.

[0055] For example, the outer diameter and inner diameter of the coil designed in this embodiment are 2.6 mm and 1.4 mm respectively, the coil height is 1 mm, the number of turns is 100, and the relative positions of the two coils are fixed; the bottom layer of the zirconium-based cladding is zirconium alloy with a conductivity of 1.43 MS / m and a thickness of 570 μm, the metal coating has a conductivity of 7.57 MS / m and a thickness of 15 μm, and the swept frequency excitation range is 500 Hz to 5 MHz.

[0056] Furthermore, the detection coils were placed above the zirconium-based cladding and in the air for measurement, and the inductive reactances of the two coils were calculated based on the measurement results to be L(ω) and L A (ω), and further differential processing can be used to obtain the change in inductive reactance.

[0057] In one embodiment of the present application, the change in inductive reactance is calculated based on the measurement results, including: measuring the impedance of each detection coil, calculating the inductive reactance of each detection coil based on the impedance and the frequency of the swept frequency excitation signal; and performing differential processing on the calculated inductive reactance data to obtain the change in inductive reactance.

[0058] Specifically, in this embodiment, the coil inductive reactance can be calculated using the following formula: L(ω) = Z(ω) / jω, where Z(ω) is the impedance of the coil, which can be directly measured. Then, the inductive reactance change is obtained by performing differential processing using the following formula: ΔL(ω) = L(ω) - L A (ω).

[0059] Step S102 : establishing a multi-layer structure eddy current analytical theoretical model based on the parameters of the two detection coils and the zirconium-based cladding, as well as the inductive reactance change measurement data.

[0060] Specifically, a multi-layer structure eddy current analytical theoretical model is established, the geometric parameters of the coil and the zirconium-based cladding parameters are set, and after a sweep frequency excitation signal is given, the inductive reactance change ΔL(ω)=L(ω)-L is calculated. A (ω).

[0061] It should be noted that this application establishes an analytical theoretical model of eddy currents in a multilayer structure based on the parameters of the zirconium-based cladding to be measured, the geometric parameters of the two detection coils, and the inductive reactance change data actually measured and calculated in the previous step. Specifically, the theoretical model is constructed based on the determined actual data, ensuring that the established analytical theoretical model is consistent with the corresponding actual situation, so that subsequent calculations within the theoretical model can yield realistic measurement results.

[0062] In one embodiment of the present application, the low-frequency inductive reactance change can be calculated using the following formula in the established model:

[0063]

[0064] Where ΔL0 is a variable related to the coil size, ω is the excitation frequency, μ0 is the vacuum permeability, σ is the substrate conductivity, α0 is the spatial resolution, and c is the substrate thickness.

[0065] That is, the change in coil inductance ΔL(ω) in the low frequency band (ω≤1kHz) can be calculated using the above formula, ensuring that the result calculated using this formula under the same parameters is consistent with the actual result obtained in the previous step.

[0066] As an example, the present application can obtain Figure 2 The coil inductive reactance change curve under swept frequency excitation is shown.

[0067] In step S103, the high-frequency inductive reactance change of the coil at different lift-off distances is obtained through the model, and a linear fit is performed on the lift-off distance and the real part logarithm of the high-frequency inductive reactance change, and the lift-off value of each detection coil is calculated based on the obtained lift-off distance fitting curve.

[0068] Specifically, only the lifting distance l of the coil is changed, and the above step S102 is repeatedly performed to obtain the high-frequency inductive reactance change ΔL(ω1) under different lifting distances. Linear fitting is performed on l and ln(ReΔL(ω1)) to obtain ln(ReΔL(ω1))=F1(l). According to the lifting distance fitting curve, the lifting values l1 and l2 of each coil are calculated.

[0069] In one embodiment of the present application, obtaining the high-frequency inductive reactance change of the coil at different lift-off distances includes: setting a high-frequency frequency and detecting multiple lift-off distance values of the coil; respectively calculating the coil inductive reactance change corresponding to each lift-off distance value at the high-frequency frequency; and the lift-off distance fitting curve obtained by fitting is expressed by the following formula:

[0070] ln(ReΔL(ω1))=al+b

[0071] Where ω1 is the high-frequency frequency, ΔL(ω1) is the change in high-frequency inductive reactance of the coil, and a and b are real numbers, a<0, b<0.

[0072] For example, in this embodiment, a single coil is used in the established analytical theoretical model, and 29 lift-off values are uniformly selected from the range of 0.085 mm to 1.5 mm. The corresponding inductive reactance change at the frequency ω1 = 1 MHz is extracted, and the fitted lift-off distance curve is shown as follows: Figure 3 As shown, data processing and analysis show that this curve can be expressed by the following formula: ln(ReΔL(ω1)) = -1720.41 - 11.0509. Experimentally, the inductive reactance change of the lower coil is ln(ReΔL1(ω1)) = -12.0573, while the inductive reactance change of the upper coil is ln(ReΔL1(ω1)) = -15.498. Based on the lift-off distance curve, the lift-off values for the lower coil are 0.585 mm, and the lift-off values for the upper coil are 2.585 mm.

[0073] In one embodiment of the present application, the high frequency is used to reduce the eddy current skin depth, and the high frequency is greater than or equal to 1 MHz.

[0074] Specifically, in the calculation of high-frequency inductive reactance changes in this application, high frequency refers to a frequency ω1 ≥ 1 MHz, which can reduce the eddy current skin depth, thereby ignoring the influence of the conductivity and thickness of the zirconium-based cladding on the lift-off distance measurement and improving the accuracy of the calculation results.

[0075] Step S104: Set the lift-off value in the model, obtain the low-frequency inductive reactance change of the coil under different substrate thicknesses, perform exponential fitting on the ratio of the substrate thickness and the imaginary part of the low-frequency inductive reactance change, and calculate the substrate thickness of the zirconium-based cladding based on the obtained substrate thickness fitting curve.

[0076] Specifically, the coil lift-off values in the model are set to l1 and l2 respectively, and only the substrate thickness t of the zirconium-based cladding is changed. The above step S102 is repeatedly performed to obtain the low-frequency inductive reactance changes ΔL1(ω2) and ΔL2(ω2) under different substrate thicknesses. Exponential fitting is performed on t and |ImΔL1(ω2) / ImΔL2(ω2)| to obtain |ImΔL1(ω2) / ImΔL2(ω2)|=F2(t); the substrate thickness t of the zirconium-based cladding is calculated according to the substrate thickness fitting curve.

[0077] In one embodiment of the present application, obtaining the low-frequency inductive reactance change of the coil under different substrate thicknesses includes: setting the low-frequency frequency and multiple substrate thicknesses of the zirconium-based cladding; calculating the ratio of the imaginary part of the low-frequency inductive reactance change corresponding to each substrate thickness at the low-frequency frequency; and the substrate thickness fitting curve obtained by fitting is expressed by the following formula:

[0078] |ImΔL1(ω2) / ImΔL2(ω2)|=k1e αt +m1

[0079] Where ω2 is the low-frequency frequency, ΔL1(ω2) is the low-frequency inductive reactance change of the upper coil, ΔL2(ω2) is the low-frequency inductive reactance change of the lower coil, k1, α, and m1 are real numbers, k1>0, α<0, m1>0.

[0080] For example, in this embodiment, the lift-off values of the two coils are set to 0.585 mm and 2.585 mm respectively in the analytical theoretical model, 57 thickness values of the substrate thickness parameter are uniformly selected from 0.002 mm to 3 mm, and 57 corresponding |ImΔL1(ω2) / ImΔL2(ω2)| values at ω2=1 kHz are extracted. The substrate thickness curve obtained by fitting is as follows: Figure 4 As shown, the specific expression of the curve is |ImΔL1(ω2) / ImΔL2(ω2)|=1.4254e -925.5917t Through experiments and subsequent calculations, we obtained |ImΔL1(ω2) / ImΔL2(ω2)|=4.0118. According to the substrate thickness curve, the substrate thickness can be obtained to be 571μm, with a relative error of 0.18%.

[0081] In one embodiment of the present application, the low frequency is used to increase the eddy current skin depth, and the low frequency is less than or equal to 1 kHz.

[0082] Specifically, in the calculation of low-frequency inductive reactance changes in this application, low frequency refers to a frequency ω2≤1kHz, which can make the eddy current skin depth larger, thereby realizing the measurement of substrate thickness and conductivity.

[0083] Step S105: Set the substrate thickness in the model, obtain the low-frequency inductive reactance change of the coil under different substrate conductivities, perform linear fitting on the substrate conductivity and the imaginary part of the current low-frequency inductive reactance change, and calculate the substrate conductivity of the zirconium-based cladding based on the obtained substrate conductivity fitting curve.

[0084] Specifically, after setting the lift-off value and substrate thickness in the model to the actual values calculated in the above steps, the substrate conductivity σ of the zirconium-based cladding is changed, and the above step S102 is repeatedly performed to obtain the low-frequency inductive reactance change ΔL1(ω2) under different substrate conductivities. Linear fitting is performed on σ and ΔL1(ω2) to obtain ImΔL1(ω2)=F3(σ), and the substrate conductivity σ of the zirconium-based cladding is calculated based on the fitted substrate conductivity fitting curve.

[0085] In one embodiment of the present application, obtaining the low-frequency inductive reactance change of the coil under different substrate conductivities includes: setting multiple substrate conductivities of the zirconium-based cladding, and calculating the imaginary part of the low-frequency inductive reactance change of the upper coil corresponding to each substrate conductivity at the low frequency; the substrate conductivity fitting curve obtained by fitting is expressed by the following formula:

[0086] ImΔL1(ω2)=k2σ+m2

[0087] Among them, k2 and m2 are real numbers, k2<0, m2<0.

[0088] For example, in this embodiment, after setting the lift-off value and substrate thickness to the above-mentioned calculated measured values in the analytical theoretical model, 19 conductivity values of the substrate conductivity parameter are uniformly selected from 1MS / m to 10MS / m, and 19 corresponding ImΔL1(ω2) at ω2=1kHz are obtained. The conductivity curve obtained by fitting is as follows: Figure 5 As shown, the specific expression of the curve is ImΔL1(ω2)=-2.2923×10 -14 σ-6.7427×10 -9 H. Through experiments and subsequent calculations, we get ImΔL1(ω2)=-4.825×10 -8 H, according to the conductivity curve, the substrate conductivity is 1.42MS / m, with a relative error of 0.7%.

[0089] In summary, the method for measuring the thickness and conductivity of the zirconium-based cladding base based on swept-frequency eddy current in the embodiment of the present application first uses a high-frequency band measurement of the swept-frequency excitation to measure the lift-off distance from the coil to the surface of the zirconium-based cladding, which is not affected by the conductivity and other properties of the zirconium-based cladding; and then further measures the thickness and conductivity of the zirconium-based cladding layer in the low-frequency band. The adopted measurement method is highly operational and accurate. Therefore, this method can simultaneously measure the thickness and conductivity of the zirconium-based cladding layer, can directly reflect the corrosion state of the cladding body, avoids the decoupling analysis of the complex characteristics of the heterogeneous film layer, is easy to operate, and has reliable test results, and has practical engineering value. Therefore, this method improves the accuracy and diversity of the zirconium-based cladding measurement results, can effectively evaluate the state of the zirconium-based cladding, and is beneficial to the normal operation of the zirconium-based cladding.

[0090] Based on the above embodiments, in order to more clearly describe the specific implementation process of substrate thickness and conductivity measurement in the present application, the measurement method in a specific embodiment is exemplified below. Figure 6 A flow chart of a specific method for measuring the thickness and conductivity of a zirconium-based cladding substrate based on swept-frequency eddy currents proposed in an embodiment of the present application is shown in FIG. Figure 6 As shown, the method includes the following steps:

[0091] Step S1: Two coaxial eddy current detection coils are manufactured. The coil geometric parameters are exactly the same, and only the distance from the zirconium-based cladding is different. A sweep frequency excitation signal is applied to the coils at the same time to induce eddy currents on the surface of the zirconium-based cladding.

[0092] Step S2: The detection coil is placed above the zirconium-based cladding and in the air respectively to measure the coil inductance, and further differential processing is performed to obtain the inductance change.

[0093] Step S3: Establish a simplified eddy current analytical theoretical model of a multi-layer structure, set the geometric parameters of the coil and the parameters of the zirconium-based cladding, and calculate the change in inductive reactance after a sweep frequency excitation signal is given.

[0094] Step S4: Only the lifting distance of the coil is changed to obtain the change of high-frequency inductive reactance under different lifting distances, linearly fit the real part logarithmic data of the lifting distance and the high-frequency inductive reactance change, and calculate the lifting value based on the lifting distance fitting curve.

[0095] Step S5: setting the corresponding lift-off value, changing the substrate thickness of the zirconium-based cladding, obtaining the ratio of the imaginary part of the low-frequency inductive reactance under different substrate thicknesses, performing exponential fitting on the substrate thickness and the ratio of the imaginary part of the low-frequency inductive reactance, and calculating the substrate thickness of the zirconium-based cladding based on the substrate thickness fitting curve.

[0096] Step S6: After setting the lift-off value and substrate thickness to actual values, the substrate conductivity of the zirconium-based cladding is changed to obtain the change in the imaginary part of the low-frequency inductive reactance of the lower coil under different substrate conductivities. A linear fit is performed on the substrate conductivity and the imaginary part of the low-frequency inductive reactance change data. Based on the substrate conductivity fitting curve, the substrate conductivity of the zirconium-based cladding is calculated.

[0097] In order to implement the above embodiment, the present application also proposes a device for measuring the thickness and conductivity of the zirconium-based cladding substrate based on swept-frequency eddy current. Figure 7 This is a schematic diagram of a device for measuring the thickness and conductivity of a zirconium-based cladding substrate based on swept-frequency eddy currents proposed in an embodiment of the present application. Figure 7 As shown, the apparatus includes: a setting module 100, a building module 200, a lift-off calculation module 300, a thickness measurement module 400 and a conductivity measurement module.

[0098] Among them, the setting module 100 is used to make two coaxial eddy current detection coils with the same geometric parameters, place the two detection coils above the zirconium-based cladding and in the air respectively, apply a swept frequency excitation signal to the two detection coils, and calculate the change in inductive reactance based on the measurement results.

[0099] The module 200 is established to establish a multi-layer structure eddy current analytical theoretical model based on the parameters of the two detection coils and the zirconium-based cladding, and the inductive reactance change measurement data.

[0100] The lift-off calculation module 300 is used to obtain the high-frequency inductive reactance change of the coil at different lift-off distances through a model, and to perform a linear fit on the real logarithm of the lift-off distance and the high-frequency inductive reactance change, and to calculate the lift-off value of each detection coil based on the obtained lift-off distance fitting curve.

[0101] The thickness measurement module 400 is used to set the lift-off value in the model, obtain the low-frequency inductive reactance change of the coil under different substrate thicknesses, perform exponential fitting on the ratio of the substrate thickness and the imaginary part of the low-frequency inductive reactance change, and calculate the substrate thickness of the zirconium-based cladding based on the obtained substrate thickness fitting curve.

[0102] The conductivity measurement module 500 is used to set the substrate thickness in the model, obtain the low-frequency inductive reactance change of the coil under different substrate conductivities, and perform a linear fit between the substrate conductivity and the imaginary part of the current low-frequency inductive reactance change. The substrate conductivity of the zirconium-based cladding is calculated based on the obtained substrate conductivity fitting curve.

[0103] It should be noted that the above explanation of the embodiment of the method for measuring the thickness and conductivity of the zirconium-based cladding substrate based on swept-frequency eddy current is also applicable to the device of this embodiment. The specific implementation method of each mode to realize its function can refer to the relevant description in the above embodiment and will not be repeated here.

[0104] In summary, the device for measuring zirconium-based cladding substrate thickness and conductivity based on swept-frequency eddy currents, as described in the embodiments of this application, can simultaneously measure the thickness and conductivity of the zirconium-based cladding layer, directly reflecting the corrosion state of the cladding itself and avoiding the need for decoupling analysis of the complex properties of heterogeneous film layers. It is easy to operate, provides reliable test results, and possesses practical engineering value. Consequently, this device improves the accuracy and diversity of zirconium-based cladding measurement results, enables effective assessment of the cladding's condition, and facilitates its normal operation.

[0105] In order to implement the above-mentioned embodiments, the present application also proposes a non-temporary computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, it implements the method for measuring the thickness and electrical conductivity of the zirconium-based cladding substrate based on swept-frequency eddy current as described in any of the above-mentioned first aspect embodiments.

[0106] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0107] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of such features. Throughout the description of this application, "plurality" means at least two, for example, two, three, etc., unless otherwise specifically defined.

[0108] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, segment or portion of code comprising one or more executable instructions for implementing the steps of a custom logical function or process, and the scope of the preferred embodiments of the present application includes alternative implementations in which functions may be performed out of the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by those skilled in the art to which the embodiments of the present application belong.

[0109] The logic and / or steps represented in the flowcharts or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing the logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (e.g., a computer-based system, a system including a processor, or other system that can fetch and execute instructions from an instruction execution system, apparatus, or device). For purposes of this specification, a "computer-readable medium" can be any device that can contain, store, communicate, propagate, or transport a program for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include the following: an electrical connection with one or more wires (electronic devices), a portable computer disk cartridge (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and programmable read-only memory (EPROM or flash memory), fiber optic devices, and a portable compact disc read-only memory (CDROM). Furthermore, the computer-readable medium may even be paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium and then editing, interpreting or processing it in another suitable manner if necessary, and then storing it in a computer memory.

[0110] It should be understood that various parts of the present application can be implemented using hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented using software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented using hardware, as in another embodiment, any one of the following technologies known in the art or a combination thereof can be used to implement: a discrete logic circuit having a logic gate circuit for implementing a logic function on a data signal, an application-specific integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0111] Those skilled in the art will understand that all or part of the steps in the method of the above embodiment can be completed by instructing related hardware through a program, and the program can be stored in a computer-readable storage medium. When the program is executed, it includes one or a combination of the steps of the method embodiment.

[0112] In addition, the functional units in the various embodiments of the present application may be integrated into a processing module, or each unit may exist physically separately, or two or more units may be integrated into a module. The above-mentioned integrated module may be implemented in the form of hardware or in the form of a software functional module. If the integrated module is implemented in the form of a software functional module and sold or used as an independent product, it may also be stored in a computer-readable storage medium.

[0113] The storage medium mentioned above may be a read-only memory, a magnetic disk, or an optical disk, etc. Although the embodiments of the present application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present application. Persons skilled in the art may make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present application.

Claims

1. A method for measuring the thickness and conductivity of a zirconium-based cladding substrate based on swept frequency eddy current, characterized in that: The following steps are involved: Two coaxial eddy current detection coils with identical geometric parameters were fabricated and placed above the zirconium-based cladding and in the air, respectively. A swept frequency excitation signal was applied to the two detection coils, and the change in inductive reactance was calculated based on the measurement results. Based on the parameters of the two detection coils and the zirconium-based cladding, as well as the inductive reactance change measurement data, a multi-layer structure eddy current analytical theoretical model is established; The model is used to obtain the change in high-frequency inductive reactance of the coil at different lift-off distances, and a linear fit is performed on the lift-off distance and the real part logarithm of the high-frequency inductive reactance change. The lift-off value of each detection coil is calculated based on the obtained lift-off distance fitting curve; Setting the lift-off value in the model, obtaining the change in low-frequency inductive reactance of the coil under different substrate thicknesses, performing exponential fitting on the ratio of the substrate thickness to the imaginary part of the change in low-frequency inductive reactance, and calculating the substrate thickness of the zirconium-based cladding based on the obtained substrate thickness fitting curve; The substrate thickness is set in the model, the low-frequency inductive reactance change of the coil under different substrate conductivities is obtained, and a linear fit is performed on the substrate conductivity and the imaginary part of the current low-frequency inductive reactance change. The substrate conductivity of the zirconium-based cladding is calculated based on the obtained substrate conductivity fitting curve.

2. The method according to claim 1, characterized in that Calculating the change in inductive reactance according to the measurement result includes: measuring the impedance of each detection coil, and calculating the inductive reactance of each detection coil according to the impedance and the frequency of the swept frequency excitation signal; The calculated inductive reactance data is differentially processed to obtain the inductive reactance change.

3. The method according to claim 1, characterized in that In the model, the low-frequency inductive reactance change is calculated by the following formula: Where ΔL0 is a variable related to the coil size, ω is the excitation frequency, μ0 is the vacuum permeability, σ is the substrate conductivity, α0 is the spatial resolution, and c is the substrate thickness.

4. The method according to claim 1, wherein The obtaining of the high-frequency inductive reactance change of the coil at different lifting distances includes: Setting the high frequency and multiple lift-off distance values of the detection coil; respectively calculating the change in coil inductance corresponding to each lift-off distance value at the high frequency; The lift-off distance fitting curve is expressed by the following formula: ln(ReΔL(ω1))=al+b Where ω1 is the high-frequency frequency, ΔL(ω1) is the change in high-frequency inductive reactance of the coil, and a and b are real numbers, a<0, b<0.

5. The method according to claim 4, characterized in that The obtaining of the low-frequency inductive reactance change of the coil under different substrate thicknesses includes: Setting low-frequency frequencies and multiple substrate thicknesses for zirconium-based cladding; Calculating the ratio of the imaginary part of the low-frequency inductive reactance change corresponding to each substrate thickness at the low-frequency frequency respectively; The substrate thickness fitting curve is expressed by the following formula: |ImΔL1(ω2) / ImΔL2(ω2)|=k1e αt +m1 Where ω2 is the low-frequency frequency, ΔL1(ω2) is the low-frequency inductive reactance change of the upper coil, ΔL2(ω2) is the low-frequency inductive reactance change of the lower coil, k1, α, and m1 are real numbers, k1>0, α<0, m1>0.

6. The method according to claim 5, characterized in that The obtaining of the change in low-frequency inductive reactance of the coil under different substrate conductivities includes: Setting multiple base conductivities of the zirconium-based cladding, and respectively calculating the imaginary part of the low-frequency inductive reactance change of the upper coil corresponding to each base conductivity at the low frequency; The substrate conductivity fitting curve is expressed by the following formula: ImΔL1(ω2)=k2σ+m2 Among them, k2 and m2 are real numbers, k2<0, m2<0.

7. The method according to claim 5, characterized in that The high frequency is used to reduce the eddy current skin depth, and the low frequency is used to increase the eddy current skin depth. The high frequency is greater than or equal to 1 MHz, and the low frequency is less than or equal to 1 kHz.

8. The method according to claim 1, characterized in that The geometric parameters of the detection coil include the inner diameter, outer diameter, height and number of turns of the coil.

9. The method according to claim 1, characterized in that The substrate and coating of the zirconium-based cladding are both made of non-ferromagnetic conductive materials, and the thickness of the substrate is much greater than the thickness of the coating.

10. A device for measuring the thickness and conductivity of a zirconium-based cladding substrate based on swept frequency eddy current, characterized in that: Includes the following modules: A setting module is used to make two coaxial eddy current detection coils with the same geometric parameters, place the two detection coils above the zirconium-based cladding and in the air respectively, apply a swept frequency excitation signal to the two detection coils, and calculate the change in inductive reactance based on the measurement results; Establishing a module for establishing a multi-layer structure eddy current analytical theoretical model based on the parameters of the two detection coils and the zirconium-based cladding, and the inductive reactance change measurement data; a lift-off calculation module, configured to obtain the change in high-frequency inductive reactance of the coil at different lift-off distances using the model, perform a linear fit on the lift-off distance and the real part logarithm of the change in high-frequency inductive reactance, and calculate the lift-off value of each detection coil based on the obtained lift-off distance fitting curve; a thickness measurement module, configured to set the lift-off value in the model, obtain the change in low-frequency inductive reactance of the coil under different substrate thicknesses, perform exponential fitting on the ratio of the substrate thickness to the imaginary part of the change in low-frequency inductive reactance, and calculate the substrate thickness of the zirconium-based cladding based on the obtained substrate thickness fitting curve; A conductivity measurement module is used to set the substrate thickness in the model, obtain the low-frequency inductive reactance change of the coil under different substrate conductivities, perform linear fitting on the substrate conductivity and the imaginary part of the current low-frequency inductive reactance change, and calculate the substrate conductivity of the zirconium-based cladding based on the obtained substrate conductivity fitting curve.

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