JPH02304397A - Method and device for deciding frictional resistance of control rod driving system - Google Patents

Abstract

PURPOSE:To shorten the handle time required for the adjustment by dividing a measured pressure differential time history waveform on a time base, and deciding a state of each of its divided pressure differential time history waveforms. CONSTITUTION:A signal from a differential pressure gauge of the upper space 13 and the lower space 12 of a driving piston 5 in the upper space of the driving piston in a control rod driving mechanism housing 9 is inputted extending over the whole stroke of the control rod, and by processing the signal by a signal processor 16, an average value and fluctuation width are derived, compared with an allowable value determined in advance and decided. In this case, a pressure differential time history waveform of the lower space 12 and the upper space 13 of the driving piston 5 measured in the case a control rod driving system is normal becomes as shown in the figure. Subsequently, this pressure differential time history waveform is divided into data P1, P2... Pn at an equal interval, and in each area, an effective value, the maximum value and an average value are calculated. In the case this value exceeds an allowable value determined in advance, it is decided that the control rod driving system is abnormal.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention relates to frictional resistance between a control rod in a control rod drive system of a boiling water reactor and a drive piston connected to the control rod. The present invention relates to a method and device for determining frictional resistance of a control rod drive system.

(Prior Art) In a boiling water reactor, as shown in FIG. 5, a reactor core 2 is housed in a reactor pressure vessel 1, and control rods 3 are inserted into or withdrawn from the reactor core 2. The control rods are driven by a control rod drive mechanism 4 provided at the bottom of the pressure vessel 1. A hydraulic piston type control rod drive mechanism is used, and the control rod 3 is inserted or withdrawn by applying water pressure to the upper or lower surface of the drive piston 5.

A seal ring 6 is installed on the drive piston 5 to seal against water pressure. Pipes 7a and 7b for supplying water pressure are also connected to the control rod drive mechanism housing 9. A guide tube 8 for guiding the movement of the control rod 3 is connected to the upper end of the housing 9.

FIG. 6 shows the usage state of the control rod 3 in the reactor pressure vessel 1. The control rod 3 has a cross shape, and there is a cross-shaped gap formed between four fuel assemblies 10. 11 and is connected to the drive piston 5 of the control rod drive mechanism at its lower end. The control rod 3 is connected to the guide tube 8 by the driving piston 5.
and the gap 11 between the fuel assemblies 10. Therefore, the movable parts in the control rod drive system are the drive piston 5 and the control rod 3. During these movements, frictional resistance occurs between them and the member that guides them. During movement, the driving force that overcomes this generated frictional resistance is applied to the driving piston 5.
must be added to.

By the way, during periodic nuclear reactor inspections, fuel assemblies or control rods are replaced, and control rod drive mechanisms are inspected. In this case, these devices will be removed from the installation and reinstalled after predetermined inspection or parts replacement. In this case, a check is performed to confirm that these operations are performed normally and that the above-mentioned frictional resistance is within a specified value. This is to prevent the control rods 3 from operating normally if a frictional resistance exceeding a specified value occurs, which would cause an inconvenient situation for the reactor.

The frictional resistance confirmation work will be explained with reference to FIG. In FIG. 5, a command is given to the control rod 3 to perform a continuous insertion operation. As a result, a predetermined water pressure is supplied to the lower space 12 of the drive piston 5 through the pipe 7a, and the drive piston 5 begins to move upward, and the water in the upper space 13 of the 1g drive piston is drained through the pipe 7b. At this time, the pressure difference between the lower space 12 and the upper space 13 is measured using a differential pressure gauge (not shown) at a pressure outlet (not shown) provided in the pipes 7a and 7b.

The differential pressure is recorded, for example on an oscilloscope, for the entire insertion stroke of the drive piston 5. The frictional resistance confirmation work is completed when the operator reads and records that the average value and fluctuation range of the recorded pressure waveform are within a predetermined range. If the average value or fluctuation range of the pressure waveform is not within the determined range, the pressure waveform measured based on the relationship between the existing problem location and the pressure waveform at that time is compared with conventional experience. We are working on identifying the problem, estimating the location of the problem, and making corrections.

(Problems to be Solved by the Invention) In the frictional resistance confirmation method described above, the number of control rod drive mechanisms that must be confirmed during periodic inspections of the reactor is approximately 1/4 of the total core. In the current situation where we have a large number of machines, it must be said that the burden on the workers is heavy. Another problem is that when abnormal waveform #1 is measured, the time required to estimate the fault location and recover from the fault largely depends on the experience and knowledge of the operator.

The present invention was made to solve the above problems,
It is an object of the present invention to provide a method and device for determining frictional resistance that can easily confirm the frictional resistance and, if an abnormality occurs, easily estimate the location of the problem.

[Structure of the invention]

(Means for Solving the Problems) The present invention provides a method for converting a measured pressure difference time history waveform over time to a pressure signal measured in a frictional resistance confirmation test conducted to determine the condition of a control rod drive system in a nuclear reactor. By dividing the pressure difference time history waveform on the axis and determining the state of each of the divided pressure difference time history waveforms, the abnormality occurrence position in the control rod drive system is estimated, and the effective value and maximum value of the pressure difference time history waveform are estimated. , a minimum value 5, determining an abnormality from the average value, and an average value for each of the divided pressure difference time history waveforms,
The maximum value, the minimum value, the effective value, the effective value obtained from the deviation from the overall average value, the ratio of the maximum value to the overall average value, the ratio of the minimum value to the overall average value, and the ratio of the average value to the overall average value. The state of each pressure difference time history waveform is determined, and the relationship between this determination result and abnormal events in the control rod drive system is stored in a database in matrix form, and those with a high degree of correlation between the determination result and the database are The feature is that it is estimated as an abnormal event occurring in the control rod drive system.

Additionally, there is a signal converter that inputs the signal from the differential pressure gauge in response to the pressure signal measured in the frictional resistance confirmation test conducted to determine the condition of the control rod drive system in the nuclear reactor, and the output of this signal converter. The present invention is characterized by comprising a signal processing device that inputs a signal and inputs an output signal that is compared with a knowledge database, and a display device that displays the output signal of the signal processing device.

(Function) Signals from the differential pressure gauges in the upper space and lower space of the drive piston in the control rod drive mechanism housing are captured over the entire stroke of the control rod, and the signals are processed by a signal processing device to determine the average value and fluctuation range. Compare and judge with a predetermined tolerance value of 9. Then, if it is outside the allowable value, the frictional resistance is abnormal, and if it is within the allowable value, the frictional resistance is normal. In addition, by comparing the output waveform from the signal processing device with abnormal events known from conventional experience and the correlation between the signal waveform at that time, it is possible to estimate the abnormal location from the measured waveform based on which waveform it resembles. do.

In this way, the judgment of whether the frictional resistance is good or bad is automatically made, and in the event of an abnormality, the abnormal location can be estimated regardless of the level of experience of the operator, and a uniform judgment can be made.

(Example) An example of a method for determining frictional resistance of a control rod drive system according to the present invention will be described with reference to FIGS. 1 to 3 and 5.

As shown in FIG. 5, a command is given to the control rod 3 to perform continuous insertion operations. As a result, a predetermined water pressure is supplied to the lower space 12 of the drive piston 5 through the pipe 7a, and the drive piston 5 starts to move upward.
Water in the upper space is drained through pipe 7b. The pressure difference between the lower space 12 and the upper space 13 at this time is determined by the pressure difference between the pipes 7a and 7.
Measurement is performed using a differential pressure gauge at a pressure outlet (not shown) provided in b, and a pressure difference time history waveform between the lower space 12 and the upper space 13 is created. This pressure difference time history waveform is divided and the effective value, maximum value, minimum value, etc. are calculated for each region.

The relationship between this data and abnormal events obtained in advance is compiled into a database in the form of a matrix, and the cause of the abnormality is estimated by comparing and referring to this database.

Figure 1 shows a time history waveform of the pressure difference between the lower space 12 and the upper space 13 of the drive piston 5, which is measured when the control rod drive system is normal during continuous control rod insertion operations during friction force confirmation work. It is. In Fig. 1, the vertical axis shows the differential pressure, and the horizontal axis shows the time (0 to to).The data of this pressure difference time history waveform is divided into equal intervals of P1゜pz+...Pn. Calculate the effective value, maximum value, minimum value, and average value in each region.

If this value exceeds a predetermined tolerance, it is determined that the control rod drive system is abnormal.

FIG. 2 shows a pressure difference time history waveform when an abnormality occurs in the control rod drive system. Symbols A, B, and C in the figure indicate each measurement example.

Furthermore, the overall average value of the pressure difference time history waveform is calculated, and 1. Find the ratio of the maximum value, minimum value, average value, and overall average value. The relationship between each of these items and abnormal events in the control rod drive system was determined based on the experience of experts and test result data.
Stored in the database as matrix-like knowledge as shown in the figure, data corresponding to the ratio of the maximum value, minimum value, average value, and overall average value for each area determined from the control rod insertion operation. By referring to the database, abnormal events occurring in the control rod drive system can be estimated.

Next, an embodiment of a frictional resistance determination device for a control rod drive system according to the present invention will be described with reference to FIGS. 4 and 5.

Note that, in the present invention, the point of obtaining the pressure difference time history waveform from the differential pressure gauge was previously explained with reference to FIG. 5, so the explanation thereof will be omitted.

FIG. 4 is a block diagram showing a frictional resistance determination device according to the present invention. A signal 14 from the differential pressure gauge is converted by a signal converter 15 and input to a signal processing device 16 using a microprocessor. The signal processing device 16 calculates the average value and the fluctuation range and outputs the results, as well as the waveform itself.

The calculation results of the average value and fluctuation range are compared and determined with preset tolerance values stored in the knowledge database 17, and the results are output to the display device [1g].

On the other hand, the differential pressure waveform is displayed on a display device 18 such as a CRT so that the operator can check it. Also knowledge base 1
In 7, waveforms corresponding to various abnormalities are filed as examples of differential pressure waveforms at the time of an abnormal event, and are output to the display device 18 as required by operator's operation.1 Operator determines that frictional resistance is abnormal. If the waveform is detected as being abnormal, or if an abnormality is detected in the waveform although it is within the allowable value, the waveforms stored in the knowledge database 17 can be sequentially recalled to the display device 18 and compared with the measured waveforms.

〔Effect of the invention〕

According to the present invention, it is not only easier to judge the frictional resistance of the control rod drive system than before, but also the location of the abnormality when the frictional resistance is abnormal can be easily estimated even by a person with little work experience. Therefore, it is possible to reduce the time and effort that was conventionally required for modifications based on the judgment of experienced personnel, and contribute to shortening the period of periodic inspections of nuclear reactors. In addition, by changing the conventional reading of measurement data by a human being to the reading by a signal processor, it is possible to make homogeneous judgments, and it is possible to improve reliability.

[Brief explanation of the drawing]

Figures 1 to 3 are for explaining an embodiment of the method for determining frictional resistance in a control rod drive system according to the present invention. 3 is a knowledge data diagram, FIG. 4 is a configuration diagram showing an embodiment of the frictional resistance determination device according to the present invention, and FIG. 5 is a diagram of a typical boiling water reactor. A vertical cross-sectional view schematically showing the structure;
FIG. 6 is a perspective view showing how the control rod in FIG. 5 is used. DESCRIPTION OF SYMBOLS 1...Reactor pressure vessel 2...Reactor core 3...Control rod 4...Control rod drive mechanism 5...Drive piston 6...Seal rings 7a, 7b...
Piping 8...Guide pipe 9...Control rod drive mechanism housing 10...Fuel assembly 11...Gap 12...
- Lower space 13... Upper space 14... Signal 15... Signal converter 16... Signal processing device 17... Knowledge database 18...
Display device (8733) Representative patent attorney Yoshiaki Inomata (and 1 other person) Figure 1 Figure 2 Figure 3 Fat size Figure 4 Figure 5

Claims (2)

[Claims] (1) Divide the measured pressure difference time history waveform on the time axis with respect to the pressure signal measured in the frictional resistance confirmation test conducted to judge the condition of the control rod drive system in a nuclear reactor, and The position of abnormality in the control rod drive system is estimated by determining the state of each pressure difference time history waveform, and the effective value of the pressure difference time history waveform is estimated.
An abnormality is determined from the maximum value, minimum value, and average value, and the effective value obtained from the deviation from the average value, maximum value, minimum value, effective value, and overall average value for each of the divided pressure difference time history waveforms. The state of each divided pressure difference time history waveform is judged from the ratio of the maximum value to the overall average value, the ratio of the minimum value to the overall average value, and the ratio of the average value to the overall average value. The method is characterized in that relationships with abnormal events in the control rod drive system are stored in a database in a matrix format, and those with a high degree of correlation between the judgment results and the database are estimated as abnormal events occurring in the control rod drive system. Method for determining frictional resistance of control rod drive system. (2) A signal converter that inputs a signal from a differential pressure gauge in response to a pressure signal measured in a frictional resistance confirmation test conducted to determine the condition of the control rod drive system in a nuclear reactor; Frictional resistance determination of a control rod drive system, characterized by comprising a signal processing device that inputs an output signal and inputs the output signal compared with a knowledge database, and a display device that displays the output signal of the signal processing device. Device.