A sensor for controlling the thickness of an oxide film on the inner wall of a guide tube for control rods

Abstract

The application relates to a sensor for measuring the thickness of an oxidation film on the inner wall of a control rod guide tube, which comprises a main skeleton, a plurality of coil skeletons, a center hole is formed in the main skeleton, the center line of the center hole is consistent with the axial line of the main skeleton, a reference coil is arranged in the main skeleton; the plurality of coil skeletons are circumferentially arranged around the outer periphery of the main skeleton, the outer peripheral wall of the coil skeleton at least partially protrudes from the outer peripheral wall of the main skeleton, a plurality of accommodating grooves are formed on the side of the coil skeleton facing the main skeleton, the accommodating grooves are sequentially distributed along the axial direction of the main skeleton, the accommodating grooves are penetrated by the center hole, a detection assembly is arranged in the accommodating groove, and the detection assembly is connected with the reference coil. The sensor provided by the application is provided with the plurality of coil skeletons, the plurality of coil skeletons are circumferentially arranged around the outer periphery of the main skeleton, the detection assembly is arranged in each coil skeleton, the thickness of the oxidation film at a plurality of positions in one circle at the same height of the guide tube can be detected in one-time scanning, and the detection efficiency is greatly improved.

Description

Technical Field

[0001] This invention relates to a sensor for measuring the thickness of the oxide film on the inner wall of a control rod guide tube. Background Technology

[0002] Most pressurized water reactor nuclear power plants in China use AFA-3G type fuel assemblies, and the guide tubes are a crucial component of these fuel assemblies. Each fuel assembly has 24 control rod guide tubes, which provide guiding channels for the insertion and withdrawal of control rods. During normal operation, they are used to regulate reactor power and, in accident conditions, to rapidly introduce negative reactivity, enabling emergency reactor shutdown and ensuring nuclear safety. Therefore, maintaining the cleanliness and unobstructed flow of the guide tubes is essential. However, the guide tubes are exposed to high temperature, high pressure, and strong radiation for extended periods, making their inner surfaces highly susceptible to oxidation. In severe cases, this can hinder control rod insertion and withdrawal, affecting the safe operation of the reactor. Therefore, measuring the oxide film thickness on the inner wall of the irradiated guide tubes is of great significance in ensuring the safe operation of fuel assemblies.

[0003] Currently, there are no domestic inspection procedures for measuring the oxide film thickness on the inner wall of the control rod guide tube. In recent years, with the localization of fuel assembly production, ensuring nuclear safety requires understanding whether the operating conditions of each component of the fuel assembly under in-service inspection conditions match expectations, or whether any changes might affect safe operation. Furthermore, as the service life of older fuel assemblies increases, measuring the oxide film thickness on the inner wall of the control rod guide tube becomes increasingly necessary and important.

[0004] See Figure 14 The control rod guide tube 13 includes a first non-buffered section 131, a first transition section 132, a buffer section 133, a second transition section 134, and a second non-buffered section 135, which are sequentially distributed along its axial direction. The inner diameters of the first non-buffered section 131 and the second non-buffered section 135 are the same. The inner diameter of the first transition section 132 gradually decreases from the first non-buffered section 131 to the buffer section 133, forming a tapered shape. The inner diameter of the second transition section 134 gradually decreases from the second non-buffered section 135 to the buffer section 133, also forming a tapered shape. The inner diameter of the buffer section 133 is the smallest. The portion of the lower end of the existing guide tube between the first and second grids is the buffer section, with a reduced diameter. Below the buffer section, at the height of the bottom positioning grid, the tube diameter is expanded to the normal tube diameter. Conventional fixed probes of the same diameter cannot penetrate the entire guide tube, making it difficult to detect the oxide film thickness of the entire tube. Summary of the Invention

[0005] The purpose of this invention is to provide a sensor for measuring the thickness of the oxide film on the inner wall of a control rod guide tube.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A sensor for measuring the thickness of the oxide film on the inner wall of a control rod guide tube includes a main frame and multiple coil frames. The main frame has a central hole, the center line of which is aligned with the axis of the main frame. A reference coil is disposed inside the main frame.

[0008] Multiple coil frames are arranged circumferentially around the outer periphery of the main frame. Multiple receiving grooves are formed on the side of the coil frame facing the main frame. The multiple receiving grooves are distributed sequentially along the axial direction of the main frame. The outer peripheral wall of the receiving groove of the coil frame protrudes from the outer peripheral wall of the main frame. The receiving groove communicates with the central hole. A detection component is arranged in the receiving groove. The detection component is connected to the reference coil.

[0009] According to some embodiments of the present invention, the sensor further includes an elastic element, one end of which abuts against the coil frame, and the other end of which abuts against the main frame.

[0010] According to some embodiments of the present invention, the detection assembly includes a detection coil, a first bushing, and a second bushing. The detection coil is connected to the reference coil, the detection coil is located inside the first bushing, and the second bushing is sleeved outside the first bushing. The first bushing is made of plastic, and the second bushing is made of metal.

[0011] According to some embodiments of the present invention, the outer peripheral wall of the coil frame is convex and arc-shaped away from the main frame.

[0012] According to some embodiments of the present invention, the coil frame includes a first segment, a second segment, and a third segment connected in sequence, the first segment, the second segment, and the third segment being distributed sequentially along the axial direction of the main frame, the outer peripheral wall of the second segment protruding from the outer peripheral walls of the first segment and the second segment, and the receiving groove being provided on the second segment.

[0013] According to some embodiments of the present invention, the sensor further includes a first guide and a second guide, the main body frame has a first end and a second end opposite to each other, the first guide is disposed at the first end of the main body frame, the second guide is disposed at the second end of the main body frame, and the coil frame is located between the first guide and the second guide.

[0014] According to some embodiments of the present invention, the first guide member and the second guide member each include a top surface and an annular side surface perpendicular to the top surface. The top surface and the annular side surface are connected and surround to form an accommodating space with an opening. The annular side surfaces of the first guide member and the second guide member are respectively threaded to the first end and the second end of the main frame.

[0015] According to some embodiments of the present invention, when the first guide and the second guide are respectively disposed at the first end and the second end of the main body frame, one end of the first segment and one end of the second segment of the coil frame abut against the inner wall of the annular side of the first guide and the second guide to restrict the coil frame from detaching from the main body frame.

[0016] According to some embodiments of the present invention, the outer periphery of the main frame is provided with a plurality of mounting grooves recessed toward its center, the mounting grooves are provided with openings communicating with the central hole, the coil frame is disposed in the mounting grooves, the outer periphery of the coil frame is located outside the mounting grooves away from the outer wall of the main frame, and the receiving groove communicates with the opening; one end of the main frame is provided with a slot, the slot communicating with the central hole, the slot being used to receive the reference coil.

[0017] According to some embodiments of the present invention, three receiving slots are provided on one side of the coil frame facing the main frame.

[0018] Due to the application of the above-mentioned technical solution, the present invention has the following advantages compared with the prior art:

[0019] The sensor provided by this invention for measuring the oxide film thickness on the inner wall of a control rod guide tube has multiple coil frames arranged circumferentially around the outer periphery of a main frame. Each coil frame contains a detection component, which is equivalent to setting multiple detection points. In a single scan, the oxide film thickness at multiple locations within the same height of the guide tube can be detected, greatly improving detection efficiency and providing more reference value. Attached Figure Description

[0020] Appendix Figure 1 This is a first-view overall structural diagram of the sensor provided by the present invention for measuring the thickness of the oxide film on the inner wall of the control rod guide tube;

[0021] Appendix Figure 2 This is a second-view overall structural diagram of the sensor provided by the present invention for measuring the thickness of the oxide film on the inner wall of the control rod guide tube;

[0022] Appendix Figure 3This is a front sectional view of the sensor provided by the present invention for measuring the thickness of the oxide film on the inner wall of a control rod guide tube;

[0023] Appendix Figure 4 A top sectional view of the sensor provided by the present invention for measuring the thickness of the oxide film on the inner wall of a control rod guide tube;

[0024] Appendix Figure 5 A first-view structural diagram of the main frame of the sensor for measuring the oxide film thickness on the inner wall of the control rod guide tube provided by the present invention;

[0025] Appendix Figure 6 A second-view structural diagram of the main frame of the sensor for measuring the oxide film thickness on the inner wall of the control rod guide tube provided by the present invention;

[0026] Appendix Figure 7 A third-view structural diagram of the main frame of the sensor for measuring the thickness of the oxide film on the inner wall of the control rod guide tube provided by the present invention.

[0027] Appendix Figure 8 This is a top view of the main frame of the sensor for measuring the oxide film thickness on the inner wall of the control rod guide tube provided by the present invention.

[0028] Appendix Figure 9 An exploded view from a first perspective of the three coil frames of the sensor for measuring the oxide film thickness on the inner wall of the control rod guide tube provided by the present invention.

[0029] Appendix Figure 10 An exploded view from a second perspective of the three coil frames of the sensor for measuring the oxide film thickness on the inner wall of the control rod guide tube provided by the present invention.

[0030] Appendix Figure 11 A first-view structural diagram of the coil frame of the sensor for measuring the oxide film thickness on the inner wall of the control rod guide tube provided by the present invention;

[0031] Appendix Figure 12 A second-view structural diagram of the coil frame of the sensor for measuring the oxide film thickness on the inner wall of the control rod guide tube provided by the present invention;

[0032] Appendix Figure 13 A third-view structural diagram of the coil frame of the sensor for measuring the oxide film thickness on the inner wall of the control rod guide tube provided by the present invention;

[0033] Appendix Figure 14 This is the front view of the control rod guide tube.

[0034] In the attached diagrams above:

[0035] 1-First guide component; 2-Main frame; 21-Mounting slot; 22-Slot; 23-Groove; 24-Opening;

[0036] 3-Coil frame, 31-First section, 32-Second section, 33-Third section, 34-Receiving groove;

[0037] 4-Second bushing; 5-First detection coil; 6-First bushing; 7-Second detection coil; 8-Elastic element; 9-Third detection coil; 10-Second guide element; 11-Reference coil; 12-Reference plate;

[0038] 13-Guide tube, 131-First non-buffered section, 132-First transition section, 133-Buffered section, 134-Second transition section, 135-Second non-buffered section. Detailed Implementation

[0039] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0041] See Figures 1 to 13 The sensor shown for measuring the oxide film thickness on the inner wall of the control rod guide tube 13 includes a main frame 2 and multiple coil frames 3. The main frame 2 is a hollow cylindrical structure, that is, a central hole is opened on the main frame 2, and the center line of the central hole is consistent with the axis of the main frame 2. A slot 22 is opened at one end of the main frame 2. The slot 22 is used to accommodate the reference coil 11 and the reference plate 12. The material of the reference plate 12 is the same as that of the guide tube. The reference plate 12 is close to the reference coil 11, which can better balance the signal.

[0042] The outer periphery of the main frame 2 has multiple recessed mounting grooves 21 along its circumferential direction, and each mounting groove 21 has an opening 24 that communicates with the central hole. Multiple coil frames 3 are arranged circumferentially around the outer periphery of the main frame 2. The coil frames 3 are positioned within the mounting grooves 21, and at least part of the outer peripheral wall of the coil frame 3 protrudes beyond the outer peripheral wall of the main frame 2. Specifically, the outer peripheral wall of the coil frame 3 away from the main frame 2 is located outside the mounting grooves 21. The outer peripheral wall of the coil frame 3 with receiving grooves 34 protrudes beyond the outer peripheral wall of the main frame. Multiple receiving grooves 34 are provided on the side of the coil frame 3 facing the main frame 2, and these grooves 34 are sequentially distributed along the axial direction of the main frame 2. Each receiving groove 34 communicates with the opening 24 of the main frame 2, and a detection component is disposed within the receiving groove 34. The detection component is connected to the reference coil 11.

[0043] When the sensor in this example is inserted into the guide tube of the control rod to detect the thickness of the oxide film on its inner wall, the outer periphery of the coil frame 3 is in contact with the inner wall of the guide tube. Multiple coil frames 3 are arranged around the outer periphery of the main frame 2, which is equivalent to setting multiple detection points. In one scan, the oxide film thickness at multiple positions within the same height of the guide tube can be detected, which greatly improves the detection efficiency.

[0044] Referring to the figure, the detection assembly includes a detection coil, a first bushing 6, and a second bushing 4. The detection coil is located inside the first bushing 6, and the second bushing 4 is fitted outside the first bushing 6. The first bushing 6 is made of plastic material, such as nylon, and the second bushing 4 is made of metal material. The advantage of setting the first bushing 6 is that it protects the detection coil from the influence of the stainless steel sleeve while enhancing the coil inductance.

[0045] In one embodiment, the coil frame 3 includes a first segment 31, a second segment 32, and a third segment 33 connected in sequence. The first segment 31, the second segment 32, and the third segment 33 are distributed sequentially along the axial direction of the main frame 2. The outer peripheral wall of the second segment 32 protrudes from the outer peripheral walls of the first segment 31 and the second segment 32, that is, the thickness of the second segment 32 is greater than the thickness of the first segment 31 and the second segment 32. The second segment 32 is provided with a receiving groove 34 for accommodating the detection component. When detecting the guide tube, the second segment 32 can correspond to the transition section of the guide tube, so as to better detect the transition section.

[0046] See Figure 1-2 The sensor also includes a first guide 1 and a second guide 10. The main frame 2 has a first end and a second end. The first guide 1 is disposed at the first end of the main frame 2, and the second guide 10 is disposed at the second end of the main frame 2. The coil frame 3 is located between the first guide 1 and the second guide 10. The first guide 1 and the second guide 10 are provided to guide the sensor to move forward and backward smoothly in the guide tube. The first guide 1 and the second guide 10 are made of plastic, preferably nylon.

[0047] See Figure 1-2 Both the first guide member 1 and the second guide member 10 include a top surface and an annular side surface perpendicular to the top surface. The top surface and the annular side surface are connected and surround to form an accommodating space with an opening. The inner part of the annular side surface is provided with threads. The first end and the second end of the main body frame 2 are both provided with threads. The annular side surface of the first guide member 1 and the second guide member 10 are respectively threaded to the first end and the second end of the main body frame 2 for easy installation and disassembly.

[0048] See Figure 3 When the coil frame 3 is placed in the mounting groove 21 of the main frame 2, one end of the annular side of the first guide 1 and the second guide 10 extends above the opposite ends of the coil frame 3, that is, there is a gap between the inner wall of the annular side of the first guide 1 and the second guide 10 and the mounting groove 21 of the main frame 2. The annular side of the first guide 1 and the second guide 10 can abut against the opposite ends of the coil frame 3 to restrict the coil frame 3 from leaving the mounting groove 21 of the main frame 2, so that the coil frame 3 is fixed in position on the main frame 2.

[0049] In this example, the outer peripheral wall of the coil frame 3, which is far from the main frame 2, is convex and arc-shaped, which can better guide the inner wall of the tube to fit together.

[0050] In this example, the number of detection coils in a coil frame 3 is equal to the number of reference coils 11. In a preferred embodiment, three coil frames 3 are provided and three reference coils 11 are provided. Each coil frame 3 has three receiving slots 34 on the side facing the main frame 2. The oxide film thickness of three points at the same height of the guide tube with a 120° interval can be detected in one scan. In this configuration, the first detection coil 5, the second detection coil 7, and the third detection coil 9 are respectively installed in the three receiving slots 34 opened on the side of the coil frame 3 facing the main frame 2. The first detection coil 5, the second detection coil 7, and the third detection coil 9 in one coil frame 3 are distributed sequentially along the axial direction of the main frame 2. The first detection coil 5 of the three coil frames 3 are arranged along one circle, the second detection coil 7 of the three coil frames 3 are arranged along another circle, and the third detection coil 9 of the three coil frames 3 are arranged along yet another circle. When the detection coils are connected to the reference coil 11: the three first detection coils 5 in the three coil frames 3 at one loop position of the main frame 2 are connected to one reference coil 11, the three second detection coils 7 in the three coil frames 3 at another loop position of the main frame 2 are connected to another reference coil 11, and the three third detection coils 9 in the three coil frames 3 at yet another loop position of the main frame 2 are connected to yet another reference coil 11. When testing the guide tube, the first detection coil 5 and the third detection coil 9 are respectively engaged with the first transition section 132 and the second transition section 134 of the guide tube to ensure the detection accuracy of the oxide film thickness of the transition section; the second detection coil 7 is engaged with the buffer section 133 of the guide tube, and the coil frame 3 corresponding to the second detection coil 7 is in elastic contact with the inner surface of the buffer section 133 of the guide tube.

[0051] The sensor also includes an elastic element 8. One end of the elastic element 8 abuts against the coil frame 3, and the other end abuts against the bottom of the mounting groove 21 of the main frame 2. The elastic element 8 ensures that the outer periphery of the coil frame 3 elastically fits against the inner wall of the guide tube, resulting in more accurate detection. (See also...) Figure 12 A large-diameter receiving groove 34 is located in the middle of the coil frame 3. The detection coil is located in the receiving groove 34. One end of the elastic member 8 is located in the receiving groove 34. A groove 23 is provided on the corresponding main frame 2. The other end of the elastic member 8 is located in the groove 23.

[0052] The sensor provided by this invention for measuring the oxide film thickness on the inner wall of a control rod guide tube has multiple coil frames arranged circumferentially around the outer periphery of a main frame. Each coil frame contains a detection component, which is equivalent to setting multiple detection points. In a single scan, the oxide film thickness at multiple locations within the same height of the guide tube can be detected, greatly improving detection efficiency and providing more reference value.

[0053] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A sensor for measuring the thickness of the oxide film on the inner wall of a control rod guide tube, characterized in that, It includes a main frame and multiple coil frames. The main frame has a central hole, the center line of which is consistent with the axis of the main frame. A reference coil is provided inside the main frame. Multiple coil frames are arranged circumferentially around the outer periphery of the main frame. Multiple receiving slots are opened on the side of the coil frame facing the main frame. The multiple receiving slots are distributed sequentially along the axial direction of the main frame. The outer peripheral wall of the coil frame with the receiving slot protrudes from the outer peripheral wall of the main frame. The receiving slot communicates with the central hole. A detection component is arranged in the receiving slot. The detection component is connected to the reference coil. The detection assembly includes a detection coil, a first bushing, and a second bushing. The detection coil is connected to the reference coil and is located inside the first bushing. The second bushing is sleeved outside the first bushing. The first bushing is made of plastic and the second bushing is made of metal. The outer peripheral wall of the coil frame, away from the main frame, is convex and arc-shaped. The coil frame includes a first section, a second section, and a third section connected in sequence. The first section, the second section, and the third section are distributed sequentially along the axial direction of the main frame. The outer peripheral wall of the second section protrudes from the outer peripheral walls of the first section and the second section. The second section is provided with the receiving groove. The sensor further includes a first guide and a second guide. The main frame has a first end and a second end opposite to each other. The first guide is disposed at the first end of the main frame, and the second guide is disposed at the second end of the main frame. The coil frame is located between the first guide and the second guide. The first guide and the second guide each include a top surface and an annular side surface perpendicular to the top surface. The top surface and the annular side surface are connected and surround to form an accommodating space with an opening. The annular side surfaces of the first guide and the second guide are respectively threaded to the first end and the second end of the main frame.

2. The sensor for measuring the oxide film thickness on the inner wall of the control rod guide tube according to claim 1, characterized in that, The sensor also includes an elastic element, one end of which abuts against the coil frame, and the other end of which abuts against the main frame.

3. The sensor for measuring the oxide film thickness on the inner wall of the control rod guide tube according to claim 1, characterized in that, When the first guide and the second guide are respectively disposed at the first end and the second end of the main body frame, one end of the first segment and one end of the second segment of the coil frame abut against the inner wall of the annular side of the first guide and the second guide to restrict the coil frame from detaching from the main body frame.

4. The sensor for measuring the oxide film thickness on the inner wall of the control rod guide tube according to claim 1, characterized in that, The outer periphery of the main frame is provided with a plurality of mounting grooves that are recessed toward the center. The mounting grooves are provided with openings that communicate with the central hole. The coil frame is disposed in the mounting grooves. The coil frame is located outside the mounting grooves away from the outer periphery of the main frame. The receiving groove communicates with the opening. The main frame has a slot at one end, which is connected to the central hole and is used to accommodate the reference coil.

5. The sensor for measuring the oxide film thickness on the inner wall of the control rod guide tube according to claim 1, characterized in that, The coil frame described herein has three receiving slots on one side facing the main frame.

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