Ultralow-frequency oscillation demagnetization self-cleaning device for control rod screw of nuclear power station

Abstract

The invention relates to the technical field of nuclear power station maintenance equipment, and particularly discloses an ultralow-frequency oscillation demagnetization self-cleaning device for a control rod screw of a nuclear power station. Aiming at the problems of high dirt relapse rate, low cleaning efficiency and long downtime caused by residual magnetism on the surface of a screw in the prior art, the device realizes efficient maintenance through a collaborative demagnetization and cleaning mechanism. The demagnetizing device adopts a synergistic effect of an alternating gradient magnetic field and mechanical oscillation, and a magnetic field attenuation coefficient is dynamically matched with oscillation amplitude, so that magnetic adsorption of dirt is weakened; the ultrasonic cleaning device and mechanical oscillation keep a phase difference of + / -90 degrees, dirt is stripped through an alternating shearing force peak value, and the efficiency is improved. The self-adaptive control module adjusts the frequency ratio based on real-time residual magnetism data, and energy consumption is reduced. The device has the advantages of efficient cleaning and prolonged equipment maintenance period, and is suitable for maintenance of the control rod screw of the nuclear power station.

Description

Technical Field

[0001] This application belongs to the technical field of nuclear power plant maintenance equipment, and particularly relates to an ultra-low frequency oscillation demagnetization and self-cleaning device for the control rod screw of a nuclear power plant. Background Art

[0002] The control rod screw of a nuclear power plant is in an underwater operating environment for a long time, and its surface is prone to adsorb iron oxide particles, boric acid crystals, and radioactive dust. The accumulation of these contaminants will cause the friction coefficient of the screw to increase by 30%-50%, leading to control rod jamming accidents.

[0003] In the prior art, Chinese Patent CN115213160A discloses a cleaning device for a control rod drive mechanism of a nuclear reactor, adopting a technical solution of single ultrasonic cleaning, which cannot eliminate the residual magnetism generated on the surface of the screw due to long-term magnetization. Experiments show that the residual magnetism will increase the adsorption force of contaminants by 2-3 times, resulting in an increase in the re-adsorption rate of contaminants after cleaning, and the screw needs to be cleaned and maintained frequently. In addition, high-frequency oscillation demagnetization is likely to damage the screw. Traditional manual cleaning requires the shutdown of the machine for more than 8 hours and there is a risk of radiation exposure. Summary of the Invention

[0004] The technical problem to be solved by the present invention is: to provide an ultra-low frequency oscillation demagnetization and self-cleaning device for the control rod screw of a nuclear power plant to solve the deficiencies in the prior art, aiming to solve at least one of the above technical problems.

[0005] The technical solution adopted by the present invention to solve its technical problems is: An ultra-low frequency oscillation demagnetization and self-cleaning device for the control rod screw of a nuclear power plant, comprising: A cavity, in which the control rod screw is coaxially clamped; An ultra-low frequency oscillation demagnetization device, which is arranged in the cavity in a liftable manner, including an axial oscillation module and a gradient demagnetization coil. The axial oscillation module generates an axial mechanical oscillation of 0.1-1 Hz and 5-50 μm. The gradient demagnetization coil is coaxially nested outside the screw and passes through an alternating current of 0.05-0.5 Hz to generate an axially decaying alternating magnetic field, and the attenuation coefficient is 0.1-0.5 / mm; An ultrasonic cleaning device, which is arranged in a liftable linkage with the ultra-low frequency oscillation demagnetization device. The ultrasonic cleaning device includes a plurality of piezoelectric transducers distributed along the axial direction of the screw, with a working frequency of 20-40 kHz, and maintains a fixed phase difference of ±90° with the axial mechanical oscillation module, and cooperates through shear force to peel off contaminants; A magnetic force detection device, including an annular Hall sensor array, for real-time detection of the residual magnetic intensity on the surface of the screw.

[0006] Preferably, in the ultra-low frequency oscillation demagnetization self-cleaning device for control rod screw of a nuclear power plant of the present invention, the synergistic effect of the phase difference of ±90° enables the shear force peak of ultrasonic cleaning and the displacement peak of mechanical oscillation to act alternately, so as to improve the efficiency of dirt stripping.

[0007] Preferably, in the ultra-low frequency oscillation demagnetization self-cleaning device for the control rod screw of a nuclear power plant of the present invention, the alternating magnetic field attenuation coefficient and the mechanical oscillation amplitude satisfy the following relationship: ; Among them, A is the amplitude, α is the attenuation coefficient, L is the screw length, and k is the proportional constant.

[0008] Preferably, the ultra-low frequency oscillation demagnetization self-cleaning device for control rod screw of a nuclear power plant of the present invention further comprises a driving mechanism, wherein the driving mechanism has a built-in adaptive control module for: a. Adjust the lifting stroke of the ultra-low frequency oscillation demagnetization device and the ultrasonic cleaning device according to the length of the screw; b. Based on the real-time data of the magnetic detection device, dynamically match the alternating current frequency and the mechanical oscillation frequency to keep the ratio between the two constant at 1:1~1:5.

[0009] Preferably, in the ultra-low frequency oscillation demagnetization self-cleaning device for the control rod screw of a nuclear power plant of the present invention, the adaptive control module dynamically adjusts the parameters based on the detection data of the Hall sensor: When the residual magnetic intensity is greater than 10 Gauss, the alternating current frequency is increased and the oscillation amplitude is increased; When the residual magnetic intensity is ≤10 Gauss, start the ultrasonic cleaning device.

[0010] Preferably, in the ultra-low frequency oscillation demagnetization self-cleaning device for control rod screw of a nuclear power plant of the present invention, the outer layer of the gradient demagnetization coil is coated with a μ-metal high magnetic permeability shielding layer, and the magnetic field leakage intensity is less than 1 Gauss.

[0011] Preferably, in the ultra-low frequency oscillation demagnetization self-cleaning device for control rod screw of a nuclear power plant of the present invention, the axial oscillation module and the gradient demagnetization coil are driven by a piezoelectric ceramic stack driver, and the piezoelectric ceramic stack driver is encapsulated in a silicon nitride ceramic housing and can withstand temperatures greater than 300°C and radiation doses greater than 10^6Gy.

[0012] Preferably, the ultra-low frequency oscillation demagnetization self-cleaning device for the control rod screw of a nuclear power plant of the present invention further comprises a high-pressure flushing device, which is arranged to be lifted and lowered in linkage with the ultrasonic cleaning device to flush attached dirt on the surface of the screw.

[0013] Preferably, the ultra-low frequency oscillation demagnetization self-cleaning device for control rods and screws of a nuclear power plant of the present invention further comprises a waste recovery system, wherein the waste recovery system comprises: A conical collection bin is arranged at the bottom of the cavity for collecting dirt, and a deep water pump is connected to the bottom. A filter screen is arranged on the inner wall of the cavity to prevent dirt from overflowing from the cavity to the external water body.

[0014] Preferably, in the nuclear power plant control rod screw ultra-low frequency oscillation demagnetization and self-cleaning device of the present invention, an electromagnetic shielding layer is further arranged on the inner wall of the cavity.

[0015] The beneficial effects of the present invention are as follows: (1) Demagnetization and efficient cleaning are coordinated: Through the synergistic effect of ultra-low frequency oscillation and gradient demagnetization coils, and through the phase difference design (±90°) of ultrasonic cleaning and mechanical oscillation, the peak shear force and peak displacement act alternately, greatly improving the dirt removal rate, reducing the re-absorption rate, and extending the maintenance time. (2) Adaptive energy-saving mode: The dynamic frequency matching technology (R = 1:1~1:5) reduces the energy consumption by 30%-50%, while avoiding mechanical overload and extending the equipment life. (3) Operational safety: It is linked with the nuclear power plant control system, shortening the operation time and reducing the risk of radiation exposure. (4) Environmentally friendly design: The dirt recycling system (deep water pump + filter screen) prevents pollutants from overflowing and meets safety standards. Description of the Drawings

[0016] The technical solutions of the present application will be further described below in conjunction with the drawings and embodiments.

[0017] Figure 1 It is a schematic diagram of the overall structure of the device in Embodiments 1-3 of the present application; Figure 2 It is a schematic cross-sectional view of the overall structure of the device in Embodiments 1-3 of the present application; Figure 3 It is a schematic diagram of the structure of the lifting mechanism in the cavity in Embodiments 1-3 of the present application; Figure 4 It is a schematic diagram of the structure of the driving mechanism in Embodiments 1-3 of the present application; Figure 5 It is a control flow chart of dynamic frequency matching in Embodiments 1 and 2 of the present application; Figure 6 It is a schematic diagram of the demagnetization rate and energy consumption curve structure at different R values in Embodiments 1 and 2 of the present application; Figure 7 It is a schematic diagram of the response curve generated based on a simplified PID model in Embodiments 1 and 2 of the present application; Figure 8 It is a schematic diagram of the control logic flow of the operation process in Embodiments 1 and 2 of the present application; The reference numerals in the drawings are: Cavity 10, control rod screw 20, ultra-low frequency oscillation demagnetization device 30, drive mechanism 40, ultrasonic cleaning device 50, magnetic force detection device 60, high-pressure flushing device 70, dirt recovery system 80; Guide rail 11, lifting frame 12, gradient demagnetization coil 31, transmission shaft 41, driving gear set 42, driven gear set 43, conical collection bin 81, deep water pump 82. Specific implementation mode

[0018] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments may be combined with each other.

[0019] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application 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, and thus should not be construed as limiting the protection scope of the present application. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, the meaning of "a plurality" is two or more.

[0020] In the description of the present application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected, or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood through specific situations.

[0021] The technical solutions of the present application will be described in detail below with reference to the drawings and in combination with the embodiments.

[0022] This embodiment provides an ultra-low frequency oscillation demagnetization and self-cleaning device for the control rod screw of a nuclear power plant. Refer to Figure 1-3The structure includes a cavity 10, which is connected by multiple octagonal pipes, and is provided with a full-through side door for easy assembly and maintenance of the equipment inside the cavity. A cylinder is hingedly provided between the side door and the outer wall of the cavity to drive the switch of the side door. The inner wall of the cavity 10 is provided with a high-temperature resistant electromagnetic shielding layer and a guide rail 11 arranged along the length direction. A lifting frame 12 is slidably installed on the guide rail 11. The lifting frame 12 is driven to lift by a driving mechanism 40. The lifting frame 12 is sequentially installed with a hollow structure ultra-low frequency oscillation demagnetization device 30, an ultrasonic cleaning device 50 and a high-pressure flushing device 70 from top to bottom, wherein the magnetic detection device 60 includes a ring A Hall sensor array is provided for real-time detection of the residual magnetic intensity on the surface of the screw. The magnetic detection device 60 is installed on the inner wall of the shaft hole of the ultra-low frequency oscillation demagnetization device 30. The high-pressure flushing device 70 is provided with four high-pressure nozzles surrounding the outer surface of the screw 20, and water is supplied by a high-pressure pump to flush the attached dirt on the surface of the screw. The dirt recovery system 80 includes a conical collection bin 81 provided at the bottom of the cavity 10, with an inclination angle of ≥45°, and a deep water pump 82 is connected to the bottom to absorb the stripped dirt. A filter screen (not marked in the figure) is provided on the inner wall of the cavity, with a mesh diameter of 0.5-1mm, which is used to prevent dirt from overflowing from the cavity to the external water body.

[0023] During operation, the screw 20 is hoisted into the cavity from the top, passes through the center holes of the above devices in sequence, and is coaxially clamped at the axis of the cavity through the upper and lower center limit sleeves in the cavity.

[0024] Preferably, the ultra-low frequency oscillation demagnetization self-cleaning device for the control rod screw of a nuclear power plant of this embodiment is as follows: Figure 4 The driving mechanism 40 includes a driving gear set 42 and a driven gear set 43 which are respectively arranged on both sides of the top of the cavity 10 and have the same transmission coefficient. A transmission shaft 41 is arranged between the driving gear set 42 and the driven gear set 43 for the synchronous action of the two sprocket transmission mechanisms. The power input shaft of the driving gear set 42 is connected to the external rotation drive device through a pair of helical gear sets. When working, the motor arranged above the water body is connected to the driving gear of the helical gear set through the transmission shaft, thereby driving the driving gear set 42 to move. A driving sprocket of the same size is connected to the power output shaft of the driving gear set 42 and the driven gear set 43, respectively. A driven sprocket of the same size as the driving sprocket is rotatably arranged on both sides of the bottom of the inner cavity of the cavity 10. The driving sprocket and the driven sprocket on the same side are driven by a chain. The two chains move at the same speed and are fixedly connected to the two sides of the lifting frame 12, respectively, to drive the lifting frame 12 to move smoothly.

[0025] Preferably, the ultra-low frequency oscillation demagnetization self-cleaning device for the control rod screw of a nuclear power plant in this embodiment, the ultra-low frequency oscillation demagnetization device 30 comprises an axial oscillation module and a gradient demagnetization coil 31, the axial oscillation module generates axial mechanical oscillation of 0.1-1 Hz and 5-50 μm, and this low frequency oscillation assists in dirt removal through two mechanisms: Inertia effect: Due to the acceleration difference between the dirt particles and the screw surface, an inertial shear force is generated, weakening the adhesion force. Fatigue failure: Periodic stress loading causes microcracks to form at the interface between the dirt and the substrate, eventually leading to fracture.

[0026] The outer layer of the gradient demagnetizing coil 31 is coated with a μ-metal high magnetic permeability shielding layer, and the magnetic field leakage intensity is < 1 gauss. The gradient demagnetizing coil 31 is energized with an ultra-low frequency alternating current of 0.05 - 0.5 Hz to generate an alternating magnetic field that decays exponentially along the axial direction of the screw, with an attenuation coefficient of 0.1 - 0.5 / mm; the axial oscillation module and the gradient demagnetizing coil 31 are driven by a piezoelectric ceramic stack actuator, and the piezoelectric ceramic stack actuator is encapsulated in a silicon nitride ceramic housing, with a tolerance temperature > 300 °C and a radiation dose > 10^6 Gy.

[0027] Preferably, for the ultra-low frequency oscillation demagnetization and self-cleaning device of the control rod screw of a nuclear power plant in this embodiment, the following relationship is satisfied between the attenuation coefficient of the alternating magnetic field and the mechanical oscillation amplitude: ; where A is the amplitude in μm, α is the attenuation coefficient in / mm, L is the length of the screw in m, and k is a proportionality constant with 10 ≤ k ≤ 50.

[0028] Preferably, for the ultra-low frequency oscillation demagnetization and self-cleaning device of the control rod screw of a nuclear power plant in this embodiment, the drive mechanism 40 is signal-linked with the control rod drive system of the nuclear power plant and is equipped with an adaptive control module for: a. Adjust the lifting stroke of the demagnetization device 30 and the cleaning device 50 according to the length of the screw; Specifically, the adaptive control module generates a lifting command based on the stroke = L + ΔL (L is the length of the screw, preset by the system, and ΔL is the safety redundancy, set to 0.2 m), and drives the sprocket drive system to drive the lifting frame 12 to move along the guide rail 11 to ensure that the demagnetizing coil 31, the magnetic force detection device 60, and the ultrasonic transducer cover the entire length of the screw.

[0029] b. Based on the real-time data detected by the Hall sensor of the magnetic force detection device 60, dynamically adjust the ratio (R = fm:fv) of the alternating current frequency (fm) to the mechanical oscillation frequency (fv) so that it always remains within the range of 1:1 to 1:5, referring to Figure 5 。

[0030] When the remanent magnetic intensity > 10 gauss, it is marked as the "high remanent magnetic region", and the alternating current frequency is increased to and the oscillation amplitude is increased; When the remanent magnetic intensity ≤ 10 gauss, start the operation of the ultrasonic cleaning device 50.

[0031] where, referring to Figure 6, the implementation of dynamic frequency matching adopts a fuzzy PID control algorithm, combining proportional-integral-derivative regulation with fuzzy logic to achieve a balance between fast response and stability.

[0032] Step 1: Set the target ratio Rtarget If Bavg > 10 Gauss → Rtarget = 1:1; If Bavg ≤ 10 Gauss → Rtarget = 1:5.

[0033] Step 2: Calculate the current ratio Rcurrent ; Step 3: Adjust the frequency parameters If Rcurrent > Rtarget → Decrease fm or increase fv; If Rcurrent < Rtarget → Increase fm or decrease fv.

[0034] Parameter adjustment rules: Proportional term P: Linearly adjust the frequency according to the difference ΔR = Rtarget - Rcurrent; Integral term I: Accumulate historical differences to eliminate steady-state errors; Derivative term D: Predict the change trend to prevent overshoot.

[0035] This design is based on the following principle, the synergistic effect of magnetic field and mechanical energy. The alternating magnetic field is responsible for eliminating residual magnetism, and mechanical vibration destroys the attachment of dirt. The reasonable matching of the frequencies of the two can avoid energy conflict and improve the demagnetization efficiency.

[0036] Preferably, for the nuclear power plant control rod screw ultra-low frequency oscillation demagnetization and self-cleaning device of this embodiment, the ultrasonic cleaning device 50 includes a plurality of piezoelectric transducers distributed along the axial direction of the screw, with a working frequency of 20 - 40 kHz, and maintains a fixed phase difference of ±90° with the axial mechanical oscillation module, and cooperates to peel off dirt through shear force.

[0037] Specifically, when the phase difference is +90°: The peak value of the ultrasonic shear force leads the peak value of the mechanical displacement by 1 / 4 cycle; when the phase difference is -90°: The peak value of the ultrasonic shear force lags the peak value of the mechanical displacement by 1 / 4 cycle.

[0038] This device adopts a ±90° phase difference to stagger the action time of the two forces, avoid energy cancellation, and at the same time form an alternating impact.

[0039] Taking the mechanical oscillation frequency of 0.5 Hz, period T = 2 s, and ultrasonic frequency of 30 kHz as an example: Peak stage of mechanical displacement (t = 0.5 s): The displacement of the screw reaches +50 μm. At this time, the ultrasonic signal is at the trough (the shear force is the smallest); the inertial force of mechanical vibration "pushes" the dirt "away" from the substrate surface, but it is not completely peeled off.

[0040] Stage of mechanical displacement returning to zero (t = 1.0 s): The ultrasonic shear force reaches the peak (about 500 N / cm²), and the cavitation bubbles collapse in the gap between the dirt and the substrate, generating a local high-pressure impact; at this time, the dirt has been loosened due to mechanical vibration, and the ultrasonic impact force directly acts on the bottom of the dirt to complete the peeling.

[0041] Experiments show that the synergistic effect of the phase difference can increase the effective energy acting on the dirt per unit time by more than 40%. For example: Without phase difference: The ultrasonic wave and mechanical vibration reach the peak simultaneously, and part of the energy cancels each other out, and the dirt peeling efficiency is only 65%; When the phase difference is ±90°: The energy utilization rate is maximized, and the dirt peeling efficiency is increased to 95%.

[0042] Specific implementation methods of the synergistic effect of phase difference 1. Realization and control of phase difference Configure hardware: Signal generator: Use a high-precision digital signal generator to output two synchronous signals: Channel 1: 0.1 - 1 Hz sine wave, driving the mechanical vibration module; Channel 2: 20 - 40 kHz square wave (converted to sine wave after filtering), driving the ultrasonic transducer.

[0043] Phase-locked circuit: Through the phase-locked loop (PLL) technology, ensure that the phase difference between the two signals is stable at ±90°, with an error < 1°.

[0044] The adaptive control module dynamically adjusts the direction of the phase difference so that different types of dirt can be effectively peeled off.

[0045] When using a -90° phase difference, it is preferred to use mechanical vibration to break the interface bond, and the peeling effect of hard dirt (such as iron oxide particles) is good; when using a +90° phase difference, it is preferred to give full play to the ultrasonic cavitation effect, and the peeling effect of soft dirt (such as boric acid crystals) is good.

[0046] 2. Quantitative analysis of shear force and displacement (1) Shear force calculation model The shear force (Fs) generated by the ultrasonic wave can be approximately expressed as: ; Among them: ρ: Liquid density (1000 kg / m³ for water); c: Sound velocity (1500 m / s for water); υ: Sound particle vibration velocity ; A: Acting area.

[0047] Taking ultrasonic waves at 30 kHz and amplitude of 5 μm as an example: ; ; (Note: The actual value of F S can be amplified by the cavitation effect to reach above 500 N / cm²) (2) Stress contribution of mechanical oscillation The inertial force (Fm) generated by mechanical oscillation is:

[0048] Wherein: m: Mass of the dirt (assumed to be 1 g); f: Oscillation frequency of 0.5 Hz; A: Amplitude of 50 μm.

[0049]

[0050] Although Fm is small, its periodic action can significantly reduce the adhesion of dirt.

[0051] 3. Experimental verification of the synergistic effect (1) Comparative experiment design Control group: Only use ultrasonic cleaning (30 kHz), without mechanical oscillation; Experimental group: Synergy of ultrasonic cleaning (30 kHz) and mechanical oscillation (0.5 Hz, 50 μm), with a phase difference of ±90°.

[0052] (2) Refer to Table 1 for the experimental results Dirt type Removal rate of the control group Removal rate of the experimental group Efficiency improvement Iron oxide particles (100μm) 68% 95% 39.7% Boric acid crystals (lamellar) 52% 89% 71.2% Radioactive dust (sticky) 45% 82% 82.2% Table 1: Comparison of the removal rate effects of different dirt (3) Analysis of the action mechanism Iron oxide particles: Mechanical oscillation preferentially destroys the mechanical interlocking between the particles and the substrate, and the ultrasonic shear force removes the residual debris; Boric acid crystals: The ultrasonic cavitation effect penetrates into the crystal layers, and mechanical oscillation accelerates the interlayer peeling; Radioactive dust: The phase difference synergistic effect overcomes the van der Waals force and prevents the dust from reabsorbing.

[0053] It should be noted that referring to Figure 7 , this device also includes a ground receiving control unit and a wireless transmission unit. The wireless transmission unit transmits the data of the underwater device to the ground in real time, supports manual remote adjustment of parameters (such as forced switching of the demagnetization / cleaning mode), and forms a closed loop of "detection - decision - execution - re - detection" based on the feedback data of the magnetic force detection device 60.

[0054] The working principle and operation process of this device will be further described below in combination with specific data.

[0055] Example 1: Structure and basic operation process of this device.

[0056] Step 1: Device assembly and screw clamping Installation of cavity 10: The cavity is composed of multiple sections of octagonal pipes spliced together, and the inner wall is sprayed with a high-temperature electromagnetic shielding layer (the material is silicon carbide composite material, with a temperature resistance of ≥500°C). The ultra-low frequency oscillation demagnetization device 30, magnetic force detection device 60, ultrasonic cleaning device 50, and high-pressure flushing device 70 are sequentially installed on the lifting frame 12, and the lifting frame 12 is installed on the guide rail 11 and is controlled by the driving mechanism 40 to lift.

[0057] The control rod screw 20 (taking the length L = 6m and diameter φ = 80mm as an example) is hoisted into the cavity from the top through the hoisting device and is coaxially fixed by the upper and lower limit sleeves.

[0058] Step 2: Demagnetization stage Generation of ultra-low frequency alternating magnetic field: An alternating current of 0.1Hz is passed through the annular demagnetization coil 31 to generate an alternating magnetic field with an initial magnetic field intensity of 200 gauss, which decays exponentially along the axial direction of the screw (α = 0.3 / mm).

[0059] The axial oscillation module drives the axial displacement of the screw at a frequency of 0.5Hz (amplitude A = 30μm), and the mechanical oscillation and magnetic field attenuation coefficient satisfy the formula: ; where k = 20, L is 6m, and after calculation, α = 0.3 / mm.

[0060] Adaptive adjustment: The initial detected residual magnetic intensity is 20 gauss, belonging to a high-residual magnetic screw (Bavg = 20 gauss).

[0061] Initial parameter setting: fm = 0.1Hz, fv = 0.2Hz (R = 1:2); Detection and determination: Bavg = 20 gauss → trigger R = 1:1 mode; Adjustment process: Gradually increase fm to 0.5Hz (hardware upper limit), and simultaneously increase fv to 0.5Hz; The demagnetization rate increases from 2 gauss / minute to 5 gauss / minute; Result: After 15 minutes, Bavg ≤ 10 gauss, switch to R = 1:5 mode (fm = 0.1Hz, fv = 0.5Hz), and trigger the cleaning stage.

[0062] Step 3: Cleaning stage Ultrasonic assisted cleaning: The ultrasonic transducer operates at a frequency of 35 kHz and maintains a -90° phase difference with the mechanical oscillation module.

[0063] The mechanical oscillation frequency is set to 0.8 Hz with an amplitude of 40 μm, alternating with the peak value of ultrasonic shear force. Experiments show that after 30 minutes, the dirt removal rate is 98.5%; the surface roughness decreases from Ra 3.2 μm to Ra 0.8 μm.

[0064] High-pressure flushing and dirt collection: The high-pressure flushing device 70 sprays water at a pressure of 60 MPa. The flushed and peeled dirt is intercepted by a 200-mesh filter screen and enters the cavity, and is discharged into the externally connected waste collection device through self-gravity sedimentation and adsorption by the deep water pump 82 from the conical collection bin 81 at the bottom.

[0065] Step 4: Effect verification Residual magnetism elimination: The residual magnetism intensity on the screw surface ≤ 2 Gauss (far lower than the 10 Gauss threshold).

[0066] Cleaning efficiency: The dirt removal rate ≥ 95%, and the re-suction rate < 5% (the re-suction rate of traditional technology > 30%).

[0067] Time cost: The whole process takes 45 minutes.

[0068] Example 2: Different from Example 1, after the demagnetization stage in Step 2, the initial detected residual magnetism intensity is 8 Gauss, belonging to a low-residual magnetism screw (Bavg = 8 Gauss).

[0069] Initial parameter settings: fm = 0.05 Hz, fv = 0.25 Hz (R = 1:5); Energy-saving effect: The energy consumption is reduced by 40% compared with the R = 1:1 mode, and the demagnetization rate remains at 1 Gauss / minute; Stability verification: Continuously operate for 2 hours, and the frequency fluctuation < ±0.01 Hz.

[0070] The effect of the dynamic frequency matching mode and the fixed frequency mode is shown in Table 2.

[0071] Working mode Demagnetization rate (Gauss / minute) Energy consumption (kW·h) Dirt stripping efficiency Fixed R = 1:1 4.5 2.8 92% Fixed R = 1:5 1.2 0.7 85% Dynamic matching (1:1~1:5) 3.8~5.0 1.2~2.0 95% Table 2: Effect verification of the dynamic frequency matching mode and the fixed frequency mode Refer to Figure 5 , while ensuring the demagnetization efficiency, the dynamic frequency matching mode reduces the energy consumption by 30% - 50%, and avoids mechanical overload through adaptive adjustment, extending the equipment life.

[0072] Example 3: Different from Example 1 and Example 2, in this example, during the demagnetization stage, the ultra-low frequency oscillation demagnetization device is driven by the driving mechanism to demagnetize the entire length of the screw in the R = 1:1 mode (or other modes, manually set according to the screw maintenance cycle and operating environment). (The coil moves from the bottom up at a speed of 6 to 12 meters per minute, demagnetizing while moving). After demagnetization is completed, then the magnetic force detection device detects the residual magnetism. The coil moves from top to bottom (at a speed of 0.5 m / s) to measure whether the residual magnetism is qualified. If it is qualified, the operation is completed. If it is not qualified, repeat the above demagnetization operation process and then measure the residual magnetism until the residual magnetism reaches the set threshold. The operation process of this example is simple and fast, with high stability, and has low requirements for the control ability of the device, and is suitable for complex operating environments.

[0073] Taking the above ideal embodiment based on this application as an inspiration, through the above description, relevant staff can completely make various changes and modifications without departing from the technical idea of this application. The technical scope of this application is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. The demagnetization and self-cleaning device for the ultra-low frequency oscillation of the control rod screw of a nuclear power plant, characterized in that, include: A cavity (10), wherein a control rod screw (20) is coaxially clamped in the cavity (10); The ultra-low frequency oscillation demagnetization device (30) is arranged in a liftable manner in the cavity (10), and comprises an axial oscillation module and a gradient demagnetization coil (31), wherein the axial oscillation module generates an axial mechanical oscillation of 0.1-1 Hz and 5-50 μm, and the gradient demagnetization coil (31) is coaxially nested on the outside of the screw (20), and an alternating current of 0.05-0.5 Hz is passed through to generate an axially attenuated alternating magnetic field with an attenuation coefficient of 0.1-0.5 / mm; An ultrasonic cleaning device (50) is arranged to be lifted and lowered in conjunction with the ultra-low frequency oscillation demagnetization device (30), wherein the ultrasonic cleaning device (50) comprises a plurality of piezoelectric transducers distributed along the axial direction of the screw (20), has an operating frequency of 20-40 kHz, and maintains a fixed phase difference of ±90° with the axial mechanical oscillation module, thereby cooperatively removing dirt through shear force; The magnetic force detection device (60) comprises a ring-shaped Hall sensor array and is used for detecting the residual magnetic intensity on the surface of the screw in real time.

2. The demagnetization and self-cleaning device for the control rod screw of a nuclear power plant with ultra-low frequency oscillation according to claim 1, characterized in that, The synergistic effect of the phase difference of ±90° enables the shear force peak of ultrasonic cleaning and the displacement peak of mechanical oscillation to act alternately, thereby improving the dirt stripping efficiency.

3. The demagnetization and self-cleaning device for the control rod screw of a nuclear power plant with ultra-low frequency oscillation according to claim 1, characterized in that, The attenuation coefficient of the alternating magnetic field and the mechanical oscillation amplitude satisfy the following relational expression: ; Where A is the amplitude, α is the attenuation coefficient, L is the screw length, and k is the proportional constant (10≤k≤50).

4. The demagnetization and self-cleaning device for the control rod screw of a nuclear power plant with ultra-low frequency oscillation according to any one of claims 1-3, characterized in that It also includes a driving mechanism (40), wherein the driving mechanism (40) has a built-in adaptive control module for: a. adjusting the lifting stroke of the ultra-low frequency oscillation demagnetization device (30) and the ultrasonic cleaning device (50) according to the length of the screw; b. Based on the real-time data of the magnetic force detection device (60), dynamically match the alternating current frequency and the mechanical oscillation frequency so that the ratio between the two is constant at 1:1~1:

5.

5. The demagnetization and self-cleaning device for the control rod screw of a nuclear power plant with ultra-low frequency oscillation, as described in claim 4, is characterized in that, The adaptive control module dynamically adjusts parameters based on the detection data of the Hall sensor: When the residual magnetic intensity is greater than 10 Gauss, the alternating current frequency is increased and the oscillation amplitude is increased; When the residual magnetic intensity is ≤10 Gauss, the ultrasonic cleaning device (50) is started to operate.

6. The demagnetization and self-cleaning device for the control rod screw of a nuclear power plant with ultra-low frequency oscillation, as described in claim 1, is characterized in that, The outer layer of the gradient demagnetization coil (31) is coated with a μ-metal high magnetic permeability shielding layer, and the magnetic field leakage intensity is less than 1 Gauss.

7. The demagnetization and self-cleaning device for the control rod screw of a nuclear power plant with ultra-low frequency oscillation, according to claim 1 or 6, is characterized in that, The axial oscillation module and the gradient demagnetization coil (31) are driven by a piezoelectric ceramic stack driver, which is packaged in a silicon nitride ceramic housing and has a tolerance temperature of >300°C and a radiation dose of >10^6Gy.

8. The demagnetization and self-cleaning device for the control rod screw of a nuclear power plant with ultra-low frequency oscillation, as claimed in claim 5, is characterized in that It also comprises a high-pressure flushing device (70), which is arranged to be lifted and lowered in conjunction with the ultrasonic cleaning device (50) and is used to flush dirt attached to the surface of the screw.

9. The demagnetization and self-cleaning device for the control rod screw of a nuclear power plant with ultra-low frequency oscillation according to claim 8, characterized in that It also includes a waste recovery system (80), the waste recovery system (80) comprising: A conical collecting bin (81) disposed at the bottom of the cavity (10) and used to collect waste, the bottom of which is connected to a deep water pump (82); The filter screen arranged on the inner wall of the cavity is used to prevent dirt from overflowing from the cavity into the external water body.

10. The demagnetization and self-cleaning device for the control rod screw of a nuclear power plant with ultra-low frequency oscillation according to claim 1, characterized in that, The inner wall of the cavity (10) is also provided with an electromagnetic shielding layer.

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