Device for diagnosing abnormalities in a control rod drive mechanism and method for diagnosing abnormalities in a control rod drive mechanism

Abstract

To provide an abnormality diagnosis device and an abnormality diagnosis method, which detect an abnormality in a control rod drive mechanism driven by a magnet motor or a stepping motor by a feature amount other than "the magnitude of an electric current" obtained from an electric motor current.SOLUTION: An abnormality detection device includes: a current acquisition unit 14 that acquires at least one phase current of an electric motor 1; zero-cross section extraction units 15, 15A that determine a zero-cross section including a zero-cross point from time-series data of the phase current acquired in the current acquisition unit 14 and extract current waveforms in the zero-cross section; a feature amount calculation unit 16 that calculates a feature amount for detecting an abnormality of a control rod drive mechanism 11 from the current waveforms in the zero-cross section; an abnormality diagnosis unit 17 that uses the feature amount to diagnose the abnormality; and a transmission unit 18 that transmits a diagnosis result by the abnormality diagnosis unit 17.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a technique for detecting an abnormality in a control rod drive mechanism driven by an electric motor in an apparatus related to nuclear power generation. [Background technology]

[0002] Patent Document 1 describes a control rod drive mechanism for reactor power that is provided within a housing in the lower part of the reactor and transmits the rotation of an electric motor to a hollow piston lifting mechanism to lift and lower the hollow piston and insert and extract the control rod into the core. The mechanism includes a spool piece provided at the lower end of the housing, an outer yoke connected to the rotating shaft of the electric motor, an outer magnet provided in the outer yoke, an inner yoke provided inside the spool piece, an inner magnet provided in the inner yoke, and a rotation detection means for the inner magnet. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 10-10264 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, the spread of IoT (Internet of Things), advances in AI (Artificial Intelligence), and a declining working population have all coincided, and attention is being paid to technology that actively uses information obtained from sensors and other devices in maintenance work, with the aim of improving the efficiency of maintenance work and reducing the number of people required.

[0005] Among these, diagnostic methods using sensor information have been proposed for the control rod drive mechanisms of nuclear power plants in order to reduce the amount of inspection work.

[0006] Typical types of sensors include vibration sensors and position sensors, but a method using current sensors is particularly noteworthy due to its ease of installation.

[0007] For example, Patent Document 1 proposes a method of detecting slippage in a magnetic coupling caused by an increase in load exceeding a tolerable value, based on the magnitude of the current in the motor.

[0008] However, the method of Patent Document 1 may not be applicable when the drive source of the control rod drive mechanism is other than an induction motor. Regardless of the type of control or the presence or absence of control, when a load change occurs in an induction motor, a phenomenon called "slip" occurs in which the motor shaft rotates out of sync with the frequency of the motor current, resulting in a large current change. For this reason, Patent Document 1 detects anomalies based on the magnitude of the current.

[0009] However, the above-mentioned "slip" does not occur in motors other than induction motors, such as magnet motors and stepping motors including hybrid types, and when these motors are controlled in an open loop, the effective value and maximum value, which are representative values ​​of the current magnitude, hardly change (less than 1%) even when there is a large load change.

[0010] In other words, in magnet motors and stepping motors, it may not be possible to detect abnormalities based on the "magnitude of current" such as the effective value or maximum value. Therefore, in order to take advantage of the easy-to-use current sensor, a technology is needed that can detect abnormalities in the control rod drive mechanism based on something other than the magnitude of the current.

[0011] The present invention has been made in consideration of the above-mentioned problems in the conventional technology and in order to solve these problems.

[0012] Therefore, an object of the present invention is to provide an abnormality diagnosis device and an abnormality diagnosis method that detect an abnormality in a control rod drive mechanism based on a feature other than the "current magnitude" obtained from the motor current.

[0013] The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings. [Means for solving the problem]

[0014] The present invention includes multiple means for solving the above-mentioned problems. One example is an apparatus for diagnosing an abnormality in a control rod drive mechanism that performs control rod insertion and extraction operations by driving a ball screw with an electric motor, the apparatus comprising: a current acquisition unit that acquires at least one phase current of the electric motor; a zero-crossing interval extraction unit that determines a zero-crossing interval including a zero-crossing point from time series data of the phase current acquired by the current acquisition unit and extracts a current waveform in the zero-crossing interval; a feature calculation unit that calculates a feature for detecting an abnormality in the control rod drive mechanism from the current waveform in the zero-crossing interval; an abnormality diagnosis unit that diagnoses an abnormality using the feature; and a transmission unit that transmits the diagnosis result of the abnormality diagnosis unit. Effect of the Invention

[0015] According to the present invention, an abnormality in a control rod drive mechanism driven by a magnet motor or a stepping motor can be detected by a characteristic quantity other than the "current magnitude" obtained from the motor current. Problems, configurations, and effects other than those described above will become apparent from the following description of the embodiments. [Brief description of the drawings]

[0016] [Figure 1] FIG. 2 is a schematic diagram of a control rod drive mechanism. [Diagram 2] FIG. 1 is a configuration diagram of an abnormality diagnosis device for a control rod drive mechanism according to a first embodiment of the present invention. [Diagram 3] FIG. 11 is a diagram showing a processing flow of a zero crossing interval extraction unit. [Figure 4] This is time series data of the motor current. [Diagram 5] FIG. 11 is a diagram supplementing the explanation of a specific section. [Figure 6] FIG. 11 is a diagram supplementing the description of feature amounts. [Figure 7]FIG. 11 is a diagram supplementing the description of feature amounts. [Figure 8] FIG. 11 is a diagram showing a process flow of a zero-crossing interval extraction unit in the control rod drive mechanism abnormality diagnosis device according to the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, an embodiment of the control rod drive mechanism anomaly detection device and control rod drive mechanism anomaly detection method of the present invention will be described with reference to the drawings. In the drawings used in this specification, the same or corresponding components are denoted by the same or similar reference numerals, and repeated description of these components may be omitted.

[0018] Representative embodiments of the present invention disclosed in the present application will be described in detail. Reference numerals in the drawings are merely illustrative of the components included in the concept of the components to which they are attached.

[0019] <Example 1> A first embodiment of an apparatus and method for detecting an abnormality in a control rod drive mechanism according to the present invention will be described with reference to FIGS. 1 to 7. FIG.

[0020] First, the overall configuration of the control rod drive mechanism that is the target of anomaly diagnosis by the anomaly detection device will be described with reference to Fig. 1. In the first embodiment of the present invention, a device that diagnoses anomalies in the control rod drive mechanism using a one-phase motor current as an input will be described. Fig. 1 shows a schematic diagram of the control rod drive mechanism.

[0021] 1 is a device for vertically moving (inserting / withdrawing) the control rod 6 for controlling the output of a nuclear reactor. The device configuration is shown below.

[0022] A power source 7 drives the electric motor 1 by supplying a periodic three-phase rectangular wave voltage (each phase being shifted by 120 degrees) to the electric motor 1 under open loop (feedforward) control.

[0023] In the description of this embodiment, the electric motor 1 is either a stepping motor or a magnet motor, and the description will be limited to a rectangular wave voltage, but the description will be similar even if the electric motor is driven by a sine wave voltage.

[0024] The shaft of the electric motor 1 driven by the power source 7 is connected to the ball screw 3 by the coupler 2 and rotates synchronously. Due to the rotation, the ball nut 4 moves up and down, and the connecting rod 5 and the control rod 6 riding on the ball nut 4 also move up and down.

[0025] In the control rod drive mechanism 11 configured and operating as described above, abnormal changes in sliding resistance may occur due to, for example, the ingestion of foreign matter, insufficient lubrication, contact with the housing, falling off of parts, etc. From here on, the device configuration of the abnormality diagnosis device 13 for detecting abnormalities in the control rod drive mechanism 11 will be explained with reference to Figure 2 etc.

[0026] The operation timing of the abnormality diagnosis device 13 or the execution timing of the method for detecting an abnormality in the control rod drive mechanism is preferably basically during periodic inspection, but it may be configured to perform detection at all times during normal power generation.

[0027] 2 shows an outline of the configuration of the control rod drive mechanism 11 and the abnormality diagnostic device 13. The control rod drive mechanism 11 is the same as in FIG. 1, so a description thereof will be omitted.

[0028] The abnormality diagnosis device 13 shown in Figure 2 is a device that diagnoses abnormalities in the control rod drive mechanism 11, which drives the ball screw 3 using the electric motor 1 to insert and extract the control rod 6, and is composed of a current acquisition unit 14, a zero-crossing interval extraction unit 15, a feature calculation unit 16, an abnormality diagnosis unit 17, and a transmission unit 18.

[0029] Of these, the zero crossing interval extraction unit 15, the feature amount calculation unit 16, the abnormality diagnosis unit 17, and the transmission unit 18 each have a central processing unit (CPU) and a memory connected to the CPU.

[0030] The control processes for the operations to be executed may be integrated into one program, or may be divided into multiple programs, or may be a combination of these.

[0031] Some or all of the programs held by each device may be implemented using dedicated hardware or may be modularized. Furthermore, various programs may be installed in each device via a program distribution server or external storage media, or existing devices may be updated.

[0032] Furthermore, each device may be an independent device connected to a wired or wireless network, or two or more devices may be integrated together.

[0033] The current acquiring unit 14 is configured with a known sensor that acquires at least one phase current of the electric motor 1. The current acquiring unit 14 preferably executes a current acquiring step of acquiring at least one phase current of the electric motor 1.

[0034] The zero-crossing interval extraction unit 15 determines a zero-crossing interval including a zero-crossing point from the time series data of the phase current acquired by the current acquisition unit 14, and extracts a current waveform in the zero-crossing interval. The feature calculation unit 16 is the main unit that executes the zero-crossing interval extraction step of determining a zero-crossing interval including a zero-crossing point from the time series data of the phase current acquired in the current acquisition step, and extracting a current waveform in the zero-crossing interval.

[0035] The feature amount calculation unit 16 calculates a feature amount for detecting an abnormality in the control rod drive mechanism 11 from the current waveform in the zero crossing section. This feature amount calculation unit 16 is the main unit that executes the feature amount calculation step of calculating a feature amount for detecting an abnormality in the control rod drive mechanism 11 from the current waveform in the zero crossing section.

[0036] The abnormality diagnosis unit 17 diagnoses an abnormality using the feature amount. The abnormality diagnosis unit 17 is the main body that executes the abnormality diagnosis step of diagnosing an abnormality using the feature amount.

[0037] The transmission unit 18 transmits the diagnosis result of the abnormality diagnosis unit 17. The transmission unit 18 is the entity that executes the transmission step of transmitting the diagnosis result in the abnormality diagnosis step.

[0038] In the abnormality diagnosis device 13, first, the motor current (time series data) of at least one phase acquired by the current acquisition unit 14 is input, and only the current data of a specific section including the timing at which the current crosses zero is extracted by the zero crossing section extraction unit 15. Next, the current data from the section extraction is used in the feature calculation unit 16 to calculate the feature used for abnormality diagnosis. Then, the calculated feature is input to the abnormality diagnosis unit 17, which performs abnormality diagnosis using machine learning or statistical methods, and the abnormality diagnosis result is transmitted to an operator or other systems by the transmission unit 18.

[0039] From here on, each processing block will be described in detail.

[0040] First, the zero-crossing interval extraction unit 15 will be described with reference to Fig. 3. As shown in Fig. 3, the zero-crossing interval extraction unit 15 is configured with a steady state standby unit 20 and an interval current holding unit 21. In this embodiment, the input motor phase current (data for diagnosis) is input to the steady state standby unit 20. In this manner, in this embodiment, the zero-crossing interval extraction unit 15 extracts the current waveform as the data acquired from the current acquisition unit 14 itself.

[0041] As shown in Fig. 4, the input motor current undergoes transient changes in current frequency and amplitude as the motor accelerates and decelerates immediately after starting operation (starting ball screw drive) and immediately before stopping. In this transient state, the current phase and amplitude may change due to differences in the initial states of the motor, ball screw, etc., so there is a high possibility that more suitable data exists to use for abnormality diagnosis.

[0042] Therefore, it is desirable for the steady state standby unit 20 to wait until the steady state is reached, using as a criterion whether the amplitude or frequency falls within a certain range (for example, within ±1%) or whether a specific time or period has passed since the start of operation, as shown in Fig. 4. The steady state standby unit 20 outputs data from the section in which the steady state is reached to the section current holding unit 21.

[0043] Thereafter, the section current holding unit 21 of the zero cross section extraction unit 15 extracts and holds the current value of a specific section including the zero cross points required for abnormality diagnosis.

[0044] Here, the section current holding unit 21 can extract the zero-crossing section from within a steady state in which the steady state waiting unit 20 has determined that the maximum value or effective value of the current of the motor 1 is within a specified error range with respect to a specified value, or from within a steady state that has been determined to be after a specific time has elapsed since the motor 1 started to operate or after the periodic fluctuation of the phase current has reached a specific number of times.

[0045] Then, the zero-crossing section can be extracted from within a specified range centered on the zero-crossing point, or from a specified section of the current cycle from the time when the phase current is at its maximum value, or a point can be arbitrarily selected within a specified section of the current cycle from the time when the phase current is at its maximum value and determined from within a specified range centered on that point.

[0046] As an extraction method, for example, the zero crossing point (in this example, it refers to the zero crossing point in the direction where the current increases. The same process applies in the opposite direction) calculated from the current data in a normal state can be set as the center of the coordinate (time), and a range of ±M points (M is an integer value equal to or greater than zero. When M=0, only the zero crossing point) from that point can be used as the specific section data. An image is shown in Figure 5. The horizontal axis of the figure is time, and the vertical axis is the current value, with the waveforms in normal and abnormal states overlaid.

[0047] As can be seen from the figure, when an abnormality occurs, the maximum current value and cycle do not change, and the largest difference occurs in the current value near the zero crossing point. Therefore, when diagnosing an abnormality, it is effective to use the current value in this vicinity (the current value near the zero crossing point is not generally referred to as the "magnitude of the current"), so only the current in the section including the zero crossing point is extracted.

[0048] As for the method of extracting the section including the zero-crossing point in the zero-crossing section extractor 15, in addition to the above, as shown in Fig. 5, extraction may be performed in a section that is 4 / 6 to 5 / 6 of the current period from the coordinate (time) where the current is maximum, or a point within the above section may be arbitrarily selected and a range of ±M points from that point may be used as the data for the specific section. Furthermore, when the U-phase current is used, it is possible to use the command value of the voltage applied to the motor 1 to extract from a period where the UV voltage is positive, the VW voltage is zero, and the WU voltage is negative.

[0049] Next, the feature amount calculation unit 16 will be described.

[0050] In the feature calculation unit 16, examples of the feature can be the current value at the coordinate of the zero cross point when the control rod drive mechanism 11 is in a normal state, or the current value of any one point in the zero cross section of the phase current when the control rod drive mechanism 11 is in a normal state, or the integral value of the current in a range equally spaced to the left and right of the coordinate of the zero cross point when the control rod drive mechanism 11 is in a normal state.

[0051] Specifically, if the aforementioned variable M is zero, then as shown in FIG. 6, the measured phase current value (diagnosis data) itself at the zero-crossing point coordinate (time) in a normal state can be used as the feature quantity. Also, the current value itself at any point in a section that is 4 / 6 to 5 / 6 of the current period from the coordinate (time) where the current is at its maximum value can be used as the feature quantity. On the other hand, if M≠0, the integral value of the current value in a specific section can be used as the feature quantity. Also, as shown in FIG. 7, the zero-crossing point coordinate (time) can be calculated for the diagnosis data as well, and the coordinate value (time) from the start point of the specific section can be used as the feature quantity.

[0052] Next, the abnormality diagnosis unit 17 will be described. For example, the abnormality diagnosis unit 17 can determine whether the feature amount is equal to or greater than a threshold value and output binary data of normal / abnormal. In addition, the abnormality diagnosis unit 17 can obtain multiple samples of the feature amount in a normal state, calculate the average value and variance in advance, calculate the Mahalanobis distance (MTD) using the following formula (1), and output the calculated continuous value as the degree of abnormality.

[0053] MTD=(Feature_meas - Feature_normal_ave)2 / Feature_normal_disp … (1) Here, in equation (1), Feature_meas is the feature at the measured current, Feature_normal_ave is the average value of the feature at normal times, and Feature_normal_disp is the variance of the feature at normal times.

[0054] The method for calculating the degree of anomaly is not limited to the above-mentioned method, and machine learning or deep learning methods such as One Class SVM may be used. Furthermore, if the average value and variance of the feature quantities of the normal data and the diagnostic data are both calculated, the average value can be tested, and the test result can be output.

[0055] Finally, the transmission unit 18 will be described.

[0056] The transmission unit 18 is a device that transmits the abnormality diagnosis results to at least one of the control device of the control rod drive mechanism 11, the control device of the electric motor 1, the power plant control system, a display, a speaker, and a lamp, and has the role of informing workers of the status of the control rod drive mechanism 11.

[0057] In addition to the above, the results of the abnormality diagnosis unit 17 can be transmitted to the motor control device, the control device of the control rod drive mechanism 11, or the power plant control device / system, and used as feedback data for equipment control such as emergency shutdown and degenerate operation.

[0058] Next, the effects of this embodiment will be described.

[0059] The abnormality diagnosis device 13 for the control rod drive mechanism 11 of the above-mentioned embodiment 1 of the present invention is a device that diagnoses abnormalities in the control rod drive mechanism 11 that drives the ball screw 3 using the electric motor 1 to insert and extract the control rod 6, and is equipped with a current acquisition unit 14 that acquires at least one phase current of the electric motor 1, a zero-crossing interval extraction unit 15 that determines a zero-crossing interval including a zero-crossing point from the time series data of the phase current acquired by the current acquisition unit 14 and extracts the current waveform of the zero-crossing interval, a feature calculation unit 16 that calculates a feature for detecting abnormalities in the control rod drive mechanism 11 from the current waveform in the zero-crossing interval, an abnormality diagnosis unit 17 that diagnoses abnormalities using the feature, and a transmission unit 18 that transmits the diagnosis result of the abnormality diagnosis unit 17.

[0060] This makes it possible to provide a new device and method for diagnosing an abnormality in the control rod drive mechanism 11, using a feature quantity other than the "magnitude of the current" obtained from the current of the electric motor 1.

[0061] Furthermore, the zero-crossing interval extraction unit 15 extracts the zero-crossing interval from a steady state in which the maximum value or effective value of the current of the motor 1 falls within a predetermined error range with respect to a predetermined value, or from a steady state after a specific time has elapsed since the motor 1 starts to drive, or after the periodic fluctuation of the phase current has reached a specific number of times. This makes it possible to extract the zero-crossing interval from data in a steady state excluding intervals in which the frequency or amplitude of the current changes transiently, thereby enabling more accurate abnormality diagnosis.

[0062] Furthermore, the zero-crossing interval extraction unit 15 extracts the current waveform using the data acquired from the current acquisition unit 14 itself, thereby improving the processing speed.

[0063] In addition, by setting the characteristic quantity to the current value at the coordinate of the zero cross point when the control rod drive mechanism 11 is in a normal state, or the current value of any one point in the zero cross section of the phase current when the control rod drive mechanism 11 is in a normal state, or the integral value of the current in a range equally spaced to the left and right of the coordinate of the zero cross point when the control rod drive mechanism 11 is in a normal state, it is possible to more accurately distinguish between normal and abnormal states.

[0064] Furthermore, by extracting the zero-crossing section from within a specified range centered on the zero-crossing point, or from a specified section of the current cycle from the time when the phase current is at its maximum value, or by arbitrarily selecting a point within a specified section of the current cycle from the time when the phase current is at its maximum value and determining it from within a specified range centered on that point, it is possible to extract as the zero-crossing section a section that reliably includes the current value near the zero-crossing point where the difference between when an abnormality occurs and when normal is large, thereby making it possible to detect abnormalities more reliably.

[0065] In addition, the transmission unit 18 can transmit the abnormality diagnosis result to at least one of the control device of the control rod drive mechanism 11, the control device of the electric motor 1, the power plant control system, a display, a speaker, and a lamp, thereby enabling an operator to reliably grasp the occurrence of an abnormality, or a system can be established in which measures are automatically taken after the system recognizes the detection of an abnormality.

[0066] <Example 2> An apparatus and method for detecting an anomaly in a control rod drive mechanism according to a second embodiment of the present invention will be described with reference to Fig. 8. Note that a description of the same processes as those in the first embodiment will be omitted, and the description will focus on the differences from the first embodiment.

[0067] The difference between the abnormality detection device for the control rod drive mechanism of this embodiment shown in Fig. 8 and the abnormality diagnosis device 13 for the control rod drive mechanism 11 of the embodiment 1 is the processing contents of the zero crossing interval extraction unit 15A. Fig. 8 shows the processing contents.

[0068] In the zero-crossing section extraction unit 15A of this embodiment, first, similarly to the first embodiment, the measured current value (diagnosis data) waits until the steady state, and then identifies a data section including a zero-crossing point (identification section setting unit 31). This makes it possible to avoid a situation in which the actual zero-crossing point becomes unclear due to frequency decomposition in the FFT unit 32, which will be described later, and the zero-crossing point cannot be identified.

[0069] On the other hand, the difference with the zero-crossing interval extraction unit 15 is that in the zero-crossing interval extraction unit 15A, in order to extract a current waveform composed of a part of the frequency components included in the data acquired from the current acquisition unit 14, the measured current value after the steady state is frequency resolved (FFT: Fast Fourier Transform) by the FFT unit 32, and at least one or more frequency components (e.g., 5 and 7 o'clock components of the current waveform) that change significantly when an abnormality occurs are selected by the specific frequency component selection unit 33. Then, the IFFT unit 34 reconverts the data into time series data (IFFT: Inverse Fast Fourier Transform). Finally, the interval data storage unit 35 extracts data of the interval determined by the specific interval setting unit 31 from the output result of the IFFT unit 34.

[0070] The subsequent processing is the same as in the first embodiment.

[0071] The other configurations and operations are substantially the same as those of the control rod drive mechanism anomaly detection device and control rod drive mechanism anomaly detection method of the first embodiment described above, and details thereof will be omitted.

[0072] The control rod drive mechanism anomaly detection device and control rod drive mechanism anomaly detection method of embodiment 2 of the present invention also provide effects substantially similar to those of the control rod drive mechanism anomaly detection device and control rod drive mechanism anomaly detection method of embodiment 1 described above.

[0073] In addition, the zero-crossing section extraction unit 15A extracts a current waveform as data composed of a portion of the frequency components contained in the data acquired from the current acquisition unit 14. This makes it possible to remove frequency components that change little when an abnormality occurs, making it easier to see current changes and enabling diagnosis of even minor abnormalities.

[0074] <Other> The present invention is not limited to the above-mentioned embodiment, but includes various modified examples. The above-mentioned embodiment has been described in detail to explain the present invention in an easily understandable manner, and the present invention is not necessarily limited to the embodiment having all of the described configurations.

[0075] It is also possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. It is also possible to add, delete, or replace part of the configuration of each embodiment with the configuration of another embodiment. [Explanation of symbols]

[0076] 1...Electric motor 2...Coupler 3...Ball screw 4...Ball nut 5...Connecting rod 6…Control rod 7…Power supply 11...Control rod drive mechanism 13...Abnormality diagnosis device 14…Current acquisition section 15...Zero cross section extraction section 15A…Zero cross section extraction section 16…Feature calculation unit 17…Abnormality diagnosis section 18...Transmission section 20...Steady state standby section 21...Section current holding section 31...Specific section setting section 32...FFT section 33...Specific frequency component selection unit 34…IFFT section 35... Section data storage unit

Claims

1. A device for diagnosing an abnormality in a control rod drive mechanism that drives a ball screw by an electric motor to insert and extract a control rod, a current acquisition unit that acquires at least one phase current of the electric motor; a zero-crossing interval extraction unit that determines a zero-crossing interval including a zero-crossing point from the time-series data of the phase current acquired by the current acquisition unit, and extracts a current waveform of the zero-crossing interval; a feature calculation unit that calculates a feature for detecting an abnormality in the control rod drive mechanism from the current waveform in the zero crossing section; an abnormality diagnosis unit that diagnoses an abnormality using the feature amount; A transmission unit that transmits a diagnosis result of the abnormality diagnosis unit. An abnormality diagnosis device for the control rod drive mechanism.

2. 2. The control rod drive mechanism abnormality diagnosis device according to claim 1, The motor is either a stepper motor or a magnet motor. An abnormality diagnosis device for the control rod drive mechanism.

3. 3. The control rod drive mechanism abnormality diagnosis device according to claim 2, The zero-crossing interval extraction unit extracts the zero-crossing interval from a steady state in which a maximum value or an effective value of the current of the motor falls within a predetermined error range with respect to a predetermined value. An abnormality diagnosis device for the control rod drive mechanism.

4. 3. The control rod drive mechanism abnormality diagnosis device according to claim 2, The zero-crossing section extraction unit extracts the zero-crossing section from a steady state after a specific time has elapsed since the motor started to be driven or after the periodic fluctuation of the phase current has reached a specific number of times. An abnormality diagnosis device for the control rod drive mechanism.

5. The control rod drive mechanism abnormality diagnosis device according to claim 3 or 4, The zero-crossing interval extraction unit extracts the current waveform from either the data acquired from the current acquisition unit itself or data composed of a part of frequency components included in the data acquired from the current acquisition unit. An abnormality diagnosis device for the control rod drive mechanism.

6. The control rod drive mechanism abnormality diagnosis device according to claim 3 or 4, The characteristic amount is a current value at the coordinate of the zero cross point when the control rod drive mechanism is in a normal state. An abnormality diagnosis device for the control rod drive mechanism.

7. The control rod drive mechanism abnormality diagnosis device according to claim 3 or 4, The characteristic amount is a current value at any one point in the zero crossing section of the phase current when the control rod drive mechanism is in a normal state. An abnormality diagnosis device for the control rod drive mechanism.

8. The control rod drive mechanism abnormality diagnosis device according to claim 3 or 4, The characteristic amount is an integral value of the current in a range equally spaced to the left and right of the coordinate of the zero crossing point when the control rod drive mechanism is in a normal state. An abnormality diagnosis device for the control rod drive mechanism.

9. The control rod drive mechanism abnormality diagnosis device according to claim 3 or 4, The zero crossing section is determined within a predetermined range centered on the zero crossing point. An abnormality diagnosis device for the control rod drive mechanism.

10. The control rod drive mechanism abnormality diagnosis device according to claim 3 or 4, The zero crossing section is determined by extracting a predetermined section of a current cycle from the time when the phase current is at a maximum value. An abnormality diagnosis device for the control rod drive mechanism.

11. The control rod drive mechanism abnormality diagnosis device according to claim 3 or 4, The zero crossing section is determined by arbitrarily selecting a point within a predetermined section of the current cycle from the time when the phase current is at its maximum value, and determining the zero crossing section from within a predetermined range centered on the point. An abnormality diagnosis device for the control rod drive mechanism.

12. 2. The control rod drive mechanism abnormality diagnosis device according to claim 1, The transmission unit transmits the abnormality diagnosis result to at least one of the control device of the control rod drive mechanism, the control device of the electric motor, the power plant control system, a display, a speaker, and a lamp. An abnormality diagnosis device for the control rod drive mechanism.

13. A method for diagnosing an abnormality in a control rod drive mechanism that performs an inserting and extracting operation of a control rod by driving a ball screw with an electric motor, comprising the steps of: a current acquisition step of acquiring at least one phase current of the electric motor; a zero-crossing section extraction step of determining a zero-crossing section including a zero-crossing point from the time-series data of the phase current acquired in the current acquisition step, and extracting a current waveform in the zero-crossing section; a feature calculation step of calculating a feature for detecting an abnormality in the control rod drive mechanism from the current waveform in the zero crossing section; an anomaly diagnosis step of diagnosing an anomaly using the feature amount; A transmission step of transmitting a diagnosis result in the abnormality diagnosis step. A method for diagnosing an abnormality in a control rod drive mechanism.

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