Radiation-resistant ball-passing detection sensor coil and design method thereof

Abstract

The invention relates to the technical field of nuclear power, and discloses an irradiation-resistant ball-passing detection sensor coil which comprises a hollow-square-shaped base film, a middle supporting piece is arranged at the hollow-out position of the center of the base film, the base film adopts a polyimide flexographic plate, two soldering tin plates are arranged at the top and the bottom of one side of the base film respectively, and the two soldering tin plates are connected with the middle supporting piece. A coil is wound on the top face of the base film from one soldering tin disc in a one-way multi-circle mode, then penetrates through the via hole and is wound on the bottom face of the base film in a one-way multi-circle mode to the other soldering tin disc, then film covering is conducted, and film covering is conducted through polyimide. According to the invention, the structure is simple, the manufacturing process is simple, winding with accurate coil size and coil number is carried out through the PCB printing technology, and the reliability of the winding is greatly improved; the consistency of batch production is good, and the method is suitable for industrial mass production.

Description

Technical Field

[0001] The invention relates to the field of nuclear power, and in particular to a radiation-resistant ball-passing detection sensor coil and a design method thereof. Background Art

[0002] The HTGR is a fourth-generation reactor that uses spherical fuel elements (fuel balls) and has a very high core outlet temperature. Before the fuel balls reach the predetermined burnup depth, they pass through the reactor core an average of 15 times. Then, the elements that exceed the burnup depth limit will be marked as spent fuel elements and sent to the spent fuel storage system through the ball pipeline system. In addition, fresh fuel balls are added through the ball pipeline system.

[0003] The eddy current detection method is currently used to detect the passage of fuel balls in the pipeline in high-temperature gas-cooled reactors. The eddy current detection method requires the use of coils to generate and detect alternating electromagnetic fields. The current sensor manufacturing method uses the method of winding coil metal wires, which has the following defects:

[0004] 1. The winding process requires strict control of process consistency, and the production process is very cumbersome.

[0005] 2. The winding is not flexible, and the loose coil reduces the reliability of the winding. Interference that cannot be filtered out occurs during vibration, causing the ball counter to miss or over-record.

[0006] 3. The wound multi-turn coils need to be dipped in varnish and bonded after winding. If the reliability of the dipping process cannot meet the standard requirements, it will directly affect the reliability of the sensor's detection. Summary of the invention

[0007] In order to overcome or alleviate one or more of the above technical problems, the present invention aims to provide a radiation-resistant ball-passing detection sensor coil and a design method thereof.

[0008] The present invention provides the following technical solutions:

[0009] The present invention provides a radiation-resistant ball-passing detection sensor coil, which includes a U-shaped base film, an intermediate support piece is provided at the hollow center of the base film, the base film adopts a polyimide flexible plate, and two solder disks are respectively arranged at the top and bottom of one side of the base film. The coil starts from one of the solder disks, surrounds the top surface of the base film in one direction for multiple turns, passes through a via hole, surrounds the bottom surface of the base film in one direction for multiple turns to the other solder disk, and then is coated. The coating adopts a polyimide coating.

[0010] The present invention also provides a design method for the above-mentioned radiation-resistant ball detection sensor coil, comprising the following steps:

[0011] S1: Optimize the design of coil parameters, design the wire diameter, number of turns, and coil center spacing parameters of the radiation-resistant ball detection sensor coil, and use the vector magnetic potential method to perform low-frequency electromagnetic field theoretical analysis on the radiation-resistant ball detection;

[0012] S2: setting boundary conditions, selecting different parameters for calculation and analysis, including different wire diameters, different coil turns, and different wire spacings, selecting one set of coil parameters, calculating the magnetic potential distribution in the target field, and then obtaining the magnetic field distribution and its coil parameters;

[0013] S3: Coil production: According to the calculation result of step S2, the flexible circuit board of the base film is produced, including the production of the flexible coil and the corresponding solder plate;

[0014] S4: Coil quality verification. According to the coil parameters obtained in S1, when making the coil, select coils with different numbers of turns and different coil center spacings to verify whether the signal is a double sine waveform, the signal-to-noise ratio of the signal, the peak-to-peak value of the signal, the amplitude of the signal and the average value of the signal.

[0015] According to some implementation methods, step S1 uses a vector magnetic potential method to perform a low-frequency electromagnetic field theoretical analysis on the radiation-resistant ball detection.

[0016] According to some implementation methods, step S3 specifically includes the following steps:

[0017] S31: Flexible coil production, first drilling holes on the base film to ensure that the hole wall is smooth, then copper plating the hole wall and the circuit surface after drilling, and then transferring the designed circuit diagram to the copper foil through exposure and development photolithography technology, and using chemical etching technology to remove excess copper foil to form a conductive circuit, i.e., a coil, and finally attaching the cover film to the etched circuit surface to form a protective layer, and the other side of the base film through the via hole is also made in the same way, thereby completing the double-sided flexible circuit production;

[0018] S32: Production of solder pad for flexible circuit board: first, evenly apply photoresist on the solder pad, then develop and etch to form the solder pad, and finally treat the surface of the solder pad to ensure the reliability of subsequent welding.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. The radiation-resistant ball detection sensor coil provided by the present invention has a simple structure and a simple manufacturing process. The coil size and number of turns can be precisely wound through PCB printing technology, which greatly improves the reliability of the winding. The batch production has good consistency and is suitable for industrial mass production.

[0021] 2. The base film used in the present invention has a certain structural strength, and the winding has a certain toughness, which overcomes the influence of winding and varnishing and the reliability of varnishing; the winding is flexible and can adapt to different shapes of pipes, and can be used for installation in straight pipes and curved pipes.

[0022] 3. The present invention adopts a flexible PCB manufacturing method, which is suitable for manufacturing more precise windings. The annular winding is wound on the ball-passing pipe and is suitable for forming annular single-turn and multi-turn windings;

[0023] 4. The sensor coil provided by the present invention is wrapped around the outside of the ball pipe to form an equivalent annular coil.

[0024] 5. In the manufacturing process of the sensor coil provided by the present invention, the base film used is made of a radiation-resistant material, so that the winding can withstand a radiation resistance of not less than 1E6 Gy, significantly improving the radiation aging resistance of the winding. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic structural diagram of a radiation-resistant ball-passing detection sensor coil provided in an embodiment of the present invention.

[0026] Figure 2 A winding cross-sectional view of a radiation-resistant ball detection sensor coil provided in an embodiment of the present invention.

[0027] Figure 3 A schematic diagram of the working state of a radiation-resistant ball-passing detection sensor coil provided in an embodiment of the present invention.

[0028] Figure 4 The test data is obtained by measuring the center spacing of 80 turns of 80 mm provided in the embodiment of the present invention.

[0029] Figure 5 The test data is obtained by measuring the center spacing of 80 turns of 40 mm provided in the embodiment of the present invention.

[0030] Figure 6 The test data is obtained by measuring the center spacing of 40 turns of 40 mm provided in the embodiment of the present invention.

[0031] Figure 7 The test data is obtained for the 20 turns with a center spacing of 40 mm provided in the embodiment of the present invention.

[0032] In the figure:

[0033] 1. Base film; 2. Intermediate support; 3. Coil; 4. Solder plate; 5. Via. DETAILED DESCRIPTION

[0034] The present invention will be described in detail below in conjunction with embodiments and the accompanying drawings. It should be understood, however, that the embodiments and the drawings are only used for exemplary description of the present invention and do not constitute any limitation to the protection scope of the present invention. All reasonable transformations and combinations within the scope of the inventive concept of the present invention fall within the protection scope of the present invention.

[0035] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", "front", "rear", etc. is based on the orientation or positional relationship shown in the accompanying drawings. These are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention; the terms "first", "second", "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance. In addition, unless otherwise clearly specified and defined, the terms "set", "installed", "connected", "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, and can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0036] The present invention will be further described below in conjunction with the accompanying drawings.

[0037] Embodiment 1

[0038] As Figures 1-2 , this embodiment provides a radiation-resistant over-ball detection sensor coil, the structure of which includes a loop-shaped base film 1, and an intermediate support 2 is provided to support the hollow part in the center of the base film 1. The base film 1 is made of polyimide flexible plate. As Figure 1 , solder pads 4 are arranged at the top and bottom on the left side of the base film 1. The coil 3 is wound around the loop-shaped base film 1 in a single direction for multiple turns, starting from one solder pad 4 on the outer side of the base film 1 and winding clockwise around the inner side of the base film 1 one by one until the fixed position, passing through the via hole 5 to the back side, and then winding counterclockwise around the inner side of the base film 1 one by one until the other solder pad 4 on the outer side of the base film 1. Copper is plated on the front and back sides of the base film 1 to form a square-hole ring-shaped winding, and then film coating is carried out. The film coating uses polyimide film coating to ensure the radiation resistance of the winding through the polyimide material.

[0039] As Figure 3, this embodiment is folded three-dimensionally when in use, folded into a cylindrical shape, supported on both sides by the middle support 2 and the base film 1 on the left and right sides, the center of the cylinder is the ball passing pipe, and the winding works around the ball passing pipe. 2. The winding is wrapped around the ball passing pipe to form a cylindrical shape, which is supported by the middle support 2 and the two sides of the base film 1 to form a three-dimensional radiation-resistant ball passing detection sensor coil.

[0040] Example 2

[0041] This embodiment is a design method for the radiation-resistant ball detection sensor coil provided in Embodiment 1, and uses PCB printing on the base film 1 to perform winding with more precise size and number of turns. The design method includes the following steps:

[0042] Step 1: Optimize the design of coil parameters. Since the conductivity of graphite balls is low, about 1x10 -5 Ω.m, the eddy current effect generated under a certain magnetic field strength is relatively weak. The main reason is that the impedance change rate of the sensor coil caused by the eddy current effect of the graphite ball is very small. Therefore, in order to improve the signal-to-noise ratio and anti-interference ability of the sensor, the optimization design of the coil parameters is particularly important, specifically optimizing the coil wire diameter, number of turns, coil center spacing and other parameters. The vector magnetic potential method is used to perform a low-frequency electromagnetic field theoretical analysis of the sensor coil, as follows:

[0043] Maxwell equations for low-frequency electromagnetic fields:

[0044]

[0045] in, is the curl operator, is the divergence operator, H is the magnetic field intensity vector, J S and J e They represent the current density vector of the external excitation source and the electromagnetic induced eddy current density vector respectively, E is the electric field intensity vector, and B is the magnetic induction intensity vector.

[0046] Introducing the vector magnetic potential A, we get the following formula:

[0047]

[0048] The relationship between the vector magnetic potential A and the electric field E is obtained as follows:

[0049]

[0050] Then we can obtain the Maxwell equations combined with the constitutive equations:

[0051]

[0052] Where μ is the magnetic permeability, H / m.

[0053] The relevant physical parameters in the calculation model can be set using equations (1)-(5);

[0054] Step 2: Set boundary conditions, select different parameters for calculation and analysis (including different wire diameters, different coil turns, different wire spacing and other parameters) to select a set of coil parameters, and then obtain the magnetic potential distribution in the target field, and then obtain the magnetic field distribution and its coil parameters.

[0055] Step 3: Coil production: According to the calculation results of the above steps, the flexible circuit board is produced, including the production of flexible coils and corresponding pads:

[0056] (1) Flexible coil production: First, drill holes on the base film 1 to ensure that the hole wall is smooth, then copper-plated the hole wall and circuit surface after drilling, and then transfer the designed circuit diagram to the copper foil through photolithography techniques such as exposure and development, and use chemical etching technology to remove excess copper foil to form a conductive circuit, i.e., coil 3. Finally, the cover film-polyimide material is attached to the etched circuit surface to form a protective layer. The above steps are performed in sequence on the other side of the base film through the via 5 to complete the double-sided flexible circuit production;

[0057] (2) Production of soldering tray for flexible circuit board: First, place the soldering tray at the designated position (see attached Figure 1 4) Evenly apply photoresist on the solder pad, then perform development, etching and other steps to form a solder pad, and finally treat the surface of the solder pad to ensure the reliability of subsequent welding.

[0058] Step 4: Verify the quality of the coils. According to the theoretical calculation results in step 1, select coils with 80 turns of 80mm center spacing, 80 turns of 40mm center spacing, 40 turns of 40mm center spacing, and 20 turns of 40mm center spacing for testing. Wrap the above coils around the test pipe and conduct actual simulation tests. Except for the above coil parameters, which have certain differences, all other parameters are the same. The test results are shown in Figures 4 to 7 ,in Figure 4 This is the test waveform of 80 turns of coil with a center spacing of 80mm. Figure 5 This is the test waveform of 80 turns of coil with a center spacing of 40mm. Figure 6 This is the test waveform with 40 turns of coil and 40mm center spacing. Figure 7 The test waveform is a 20-turn coil with a center spacing of 40mm. The coil performance can be evaluated from five aspects: whether the signal is a double sine waveform, the signal-to-noise ratio of the signal, the peak-to-peak value of the signal, the amplitude of the signal and the signal average value. The 80-turn coil with a center spacing of 40mm is preferred, and the theoretical analysis results described in step 1 are verified at the same time.

[0059] When in use, the sensor coil is wound around the ball pipe to form a cylindrical shape. The intermediate support 2 and the two sides of the base film 1 are used together to form a three-dimensional cylindrical structure, which is easy to wrap the ball pipe.

[0060] The above embodiments are only preferred implementations of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A radiation-resistant ball detection sensor coil, characterized in that: It includes a U-shaped base film, an intermediate support is provided at the hollow center of the base film, the base film adopts a polyimide flexible plate, two solder disks are respectively arranged at the top and bottom of one side of the base film, the coil starts from one of the solder disks, surrounds the top surface of the base film in one direction for multiple turns, passes through the via hole, surrounds the bottom surface of the base film in one direction for multiple turns to the other solder disk, and then is coated with a polyimide coating.

2. A design method for the radiation-resistant ball detection sensor coil according to claim 1, characterized in that: The following steps are involved: S1: Optimizing the design of coil parameters, designing the wire diameter, number of turns, and coil center spacing parameters of the radiation-resistant ball detection sensor coil, and using the vector magnetic potential method to perform low-frequency electromagnetic field theoretical analysis on the radiation-resistant ball detection; S2: setting boundary conditions, selecting different parameters for calculation and analysis, including different wire diameters, different coil turns, and different wire spacings, selecting one set of coil parameters, calculating the magnetic potential distribution in the target field, and then obtaining the magnetic field distribution and its coil parameters; S3: Coil production: According to the calculation result of step S2, the flexible circuit board of the base film is produced, including the production of the flexible coil and the corresponding solder plate; S4: Coil quality verification. According to the coil parameters obtained in S1, when making the coil, select coils with different numbers of turns and different coil center spacings to verify whether the signal is a double sine waveform, the signal-to-noise ratio of the signal, the peak-to-peak value of the signal, the amplitude of the signal and the average value of the signal.

3. The design method according to claim 2, characterized in that: Step S1 uses a vector magnetic potential method to perform a low-frequency electromagnetic field theoretical analysis on the radiation-resistant ball detection.

4. The design method according to claim 2, characterized in that: Step S3 specifically includes the following steps: S31: Flexible coil production, first drilling holes on the base film to ensure that the hole wall is smooth, then copper plating the hole wall and the circuit surface after drilling, and then transferring the designed circuit diagram to the copper foil through exposure and development photolithography technology, and using chemical etching technology to remove excess copper foil to form a conductive circuit, i.e., a coil, and finally attaching the cover film to the etched circuit surface to form a protective layer, and the other side of the base film through the via hole is also made in the same way, thereby completing the double-sided flexible circuit production; S32: Production of solder pad for flexible circuit board: first, evenly apply photoresist on the solder pad, then develop and etch to form the solder pad, and finally treat the surface of the solder pad to ensure the reliability of subsequent welding.

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