JPS6362684B2 - - Google Patents

Description

[Detailed Description of the Invention] (1) Object of the Invention The present invention relates to a loose parts detection device for a nuclear power plant.

(2) Prior Art A loose parts detection device detects so-called loose parts such as falling off internal structures of a nuclear reactor or peripheral equipment thereof. The detection principle is to detect loose parts by using an acoustic detector installed outside the furnace to detect the impact sound generated when the loose parts collide with the furnace wall or piping.

The configuration of a conventional loose parts detection device is shown in FIG. Acceleration detectors attached to the outer wall of the reactor pressure vessel 1 and main piping (main steam piping 2, water supply piping 3, recirculation inlet piping 4, recirculation outlet piping 5),
A signal from an acoustic detector 6 such as an AE sensor is processed by an amplifier 7 and a bandpass filter 8, and then sent to a full-wave rectifier 9.
It is rectified by This signal is input to an envelope circuit 10 to generate an envelope signal of the rectified signal. The signal No. 10 is input to a threshold circuit 11, and when the envelope signal is above a predetermined set level, it is determined that a loose part has been detected and this is displayed on the display circuit 12.
In the case of this detection device, spike-shaped noise such as electrical noise is generated, and if the amplitude is higher than the set level, the problem is that this noise will be determined to be generated by loose parts and a false alarm will be issued. .

(3) Object of the invention An object of the invention is to eliminate the above-mentioned drawbacks and to provide a device that detects loose parts while minimizing the influence of noise.

(4) Summary of the Invention The present invention, as a means of removing noise and detecting loose parts, passes the output signal of the detector through an envelope circuit, and separately obtains differential outputs at the rise and fall of the envelope waveform. When the output, envelope waveform output and differential output at rise are above the set level,
It is determined that a loose part has occurred when the differential output at the time of falling is below a set level.

(5) Embodiments of the invention The present invention will be explained in detail below based on the drawings.
FIG. 2 shows an embodiment of the present invention. accelerometer or
An acoustic detector 1 such as an AE detector is installed in the target reactor pressure vessel or piping. The signal from the acoustic detector 1 is processed by an amplifier 2 and a bandpass filter 3, and then rectified by a full-wave rectifier 4. This signal is input to the envelope circuit 5 to generate an envelope signal of the rectified signal. The envelope signal No. 5 is input to a threshold circuit 6 and a differentiation circuit 8. 6 is a circuit that outputs a pulse of constant amplitude while an input of a set level or higher is obtained from 5. The falling timing pulse generation circuit 7 is a circuit that generates a pulse with a constant amplitude and a constant time when the output of the pulse generator 6 changes from a constant amplitude value to 0. The output of 8 is input to half wave rectifiers 9 and 12. 9 inputs the positive signal (differential output at the time of rise) of the output of 8 to the peak hold circuit 10 . The threshold circuit 11 outputs a pulse of constant amplitude when the output of 10 exceeds a set level.
12 inputs the negative signal (differential output at the time of falling) of the output of 8 to the peak hold circuit 13. The threshold circuit 14 outputs a pulse of constant amplitude when the output of the threshold circuit 13 exceeds a set level. The inverting circuit 15 outputs a pulse of constant amplitude when there is no output from the inverting circuit 14. AND circuit 18 is 7,1
When the outputs from 1 and 15 exist simultaneously, a signal is output to the display circuit 19. 10 and 13 are OR
A circuit 16 and a timer 17 reset the output after a certain period of time after the output of 10 or 13 exceeds a set level.

This device has an acoustic signal that exceeds the set value.
When the signal waveform rises quickly (the positive output of the differential of the envelope signal is large) and falls slowly (the positive output of the differential of the envelope signal is small), loose parts are detected. An alert is issued if this occurs. The signal waveform of the impact sound caused by loose parts has the above characteristics, but the signal waveform of electrical noise generally has both a steep rise and fall or a slow fall, so this device is not suitable for this purpose. For example, electrical noise will not cause false alarms.

FIG. 3 shows output signal waveforms of each component in FIG. 2. FIG. 3 shows the impact sound caused by loose parts and the case caused by electrical noise.
100 indicates impact sound, 200 indicates noise, and 300 to 700 indicates threshold.

(6) Effects of the invention False alarms caused by electrical noise can be removed and loose parts can be detected.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a conventional loose parts detection device, FIG. 2 is a diagram showing a loose parts detection device according to the present invention, and FIG. 3 is a diagram showing output signal waveforms of each component in FIG. 2. 1...Acoustic detector, 2...Amplifier, 3...Band filter, 4...Full wave rectifier, 5...Envelope circuit,
6... Threshold circuit, 7... Falling timing pulse generation circuit, 8... Differentiator circuit, 9... Half wave rectifier, 10... Peak hold circuit, 11...
Threshold circuit, 12... Half-wave rectifier, 13... Peak hold circuit, 14... Threshold circuit, 15
...Inverting circuit, 16...OR circuit, 17...Timer, 18...AND circuit, 19...Display circuit.

Claims (1)

[Claims] 1. Metal pieces that have fallen off or mixed into the reactor are
In a loose parts detection device that detects by processing a signal from an acoustic detector attached to the outer wall of a reactor pressure vessel or a main pipe, means for obtaining an envelope signal of an output signal of the acoustic detector, and an envelope of one event. A means for separately extracting a differential output at the rising edge of a waveform and a positive differential output at the falling edge of the waveform, and a means for extracting the differential output at the rising edge of the waveform exceeds a predetermined set level, and the differential output at the falling edge of the waveform exceeds a predetermined setting level. 1. A loose parts detection device comprising means for determining that a loose part has been present when the envelope waveform output is equal to or less than a predetermined set level.