JPS6042479B2 - Coolant leakage sound simulation sound source - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sound source that simulates the sound of coolant leakage from a water-cooled nuclear reactor, and more specifically to the design of a device that detects coolant leakage using acoustics, engineering, and sensors. This article relates to a leakage sound simulating sound source used when measuring the necessary leakage sound attenuation rate.

As one of the devices for detecting small leaks of coolant from a water-cooled nuclear reactor, there is a leak detection device that uses an acoustic mechanical sensor (hereinafter abbreviated as “Wasesen”).

The leak detection principle of this device is to detect high-frequency vibrations (100 KHz to 1 MHz) of reactor structures that occur when high-temperature, high-pressure coolant leaks into the atmosphere using a sensor that can detect weak vibrations in the high-frequency band with high sensitivity. ). By the way, when designing such a leakage detector, it is necessary to determine the attenuation rate of leakage sound in advance and understand the detectable range.

However, the attenuation rate when weak vibrations in the high frequency band propagate through a structure depends on the structure's shape, material, support structure, and various other factors. The high frequency generated by flowing the coolant (for example, pressure 70 to 9/Clt and temperature 280°C) in the operating state of the reactor, forming a leak hole at a predetermined position, and actually leaking high temperature and high pressure water. The attenuation rate was determined by measuring the weak vibrations in the band using an AE sensor while changing the distance to the leak point. Therefore, it is necessary to actually leak high-temperature, high-pressure water, and a large number of actual measurements (number of leakage points) are required, making measurements time-consuming, extremely cumbersome, and problematic in terms of safety. .

The purpose of the present invention is to eliminate the drawbacks of the prior art, and to provide safe, quick, and efficient high-temperature, high-pressure water without actually leaking water.
Another object of the present invention is to provide a device that can easily measure the attenuation rate of coolant leakage sound.

In order to achieve this object, the present invention has developed a sound source that simulates the sound of an actual coolant leak, and includes a broadband piezoelectric element that is attached to the expected leakage location, and a pulse with a random pulse width applied to the piezoelectric element. It is configured in combination with a random signal generator that supplies The present invention will be explained in more detail below based on the drawings.

An example of a target for detection of coolant leakage noise is a pressure tube nuclear reactor as shown in FIG. Although the structure of such a nuclear reactor is well known, it will be briefly explained along with the function of each part. The reactor main body is composed of a power tank 1, a pressure pipe 2, a fuel assembly, a shield (not shown), and the like.
The force lander tank 1 is filled with heavy water as a moderator, and the pressure pipes 2 are inserted into the force lander tubes arranged in a square grid. The fuel assembly is located within the pressure chamber 2 and is connected to the inlet pipe 3.
The coolant is heated by nuclear heat and boils, forming a two-phase flow of water and steam, which flows through the riser pipe 4 into the steam drum 5. reach. The steam drum 5 has a steam and water separator for separating steam and water, where the two-phase flow is separated, the steam is sent to the turbine system, and the water is sent via the downcomer 6 to the lower header 8 by the recirculation pump 7. is fed back into each pressure pipe via the The structure of the mock-up used to actually measure the attenuation rate by leaking high-temperature, high-pressure water has almost the same structure as the above-mentioned nuclear reactor, but the cooling water flowing inside the motsu-up device is exposed to nuclear heat in the pressure pipe section. Instead, it is heated to reactor operating conditions using electric heaters.

However, when measuring the attenuation rate using the simulated sound source according to the present invention, room-temperature water is flowed into the motsukup without flowing high-temperature, high-pressure water. It's fine.

Now, as shown in FIG. 2, the simulated sound source consists of a broadband piezoelectric transducer 10 that is attached to a location where leakage is expected, and a random signal generator 11.

The random signal generator 11 randomly generates bipolar pulses. By inputting a random voltage signal generated with a pulse width (minimum 0.6 microseconds) to the piezoelectric transducer 10, a random load change can be caused in the piezoelectric transducer 10. As this broadband piezoelectric transducer 10, a hip sensor can be used. This is because the AE sensor is made of a piezoelectric element that reversibly changes in that it generates a voltage when a load is applied, and a force when a voltage is applied. FIG. 3 shows an example of the configuration of a device for detecting simulated sounds. The signal from the Tsukuda sensor 12 installed at a predetermined location on the Motsukuup is
Main amplifier 1 with built-in filter via preamplifier 13
4 and measured by an effective voltmeter 15. Random load changes generated in the piezoelectric transducer 10 by signals from the random signal generator 11 give weak vibrations to the mockup structure.

The vibration is attenuated by propagating through the structure and reaches the sensor 12, where it is converted into an electrical signal.
The signal is amplified by a preamplifier 13 and a main amplifier 14, and the amplified signal is measured and recorded by an effective voltmeter 15. By determining the amount of attenuation at multiple points at different distances from the simulated sound source, the attenuation rate can be determined, and the detection range can be determined. Next, an example of actual measurement using the device of the present invention will be described.

The AE sensor used in the measurement has a frequency band of 100KHz.
- It is a wideband AE sensor with detection sensitivity at 300 kHz, and the bandpass filter inside the main amplifier has a detection sensitivity of 300 kHz.
-2 MHz, and the preamplifier and main amplifier gains were 40 dB and 0 to 60 c1B, respectively. The results are shown in FIG. Curve B shows high-temperature, high-pressure water (pressure 70k9/Cltl) flowing inside the motsukup.
Attenuation curve when actually leaking water (temperature 280°C),
Curve A shows an attenuation curve when a coolant at room temperature is made to flow using the simulated sound source according to the present invention. The results showed that both curves showed almost the same attenuation, and it was demonstrated that the attenuation rate could be evaluated by placing a simulated sound source at the expected leak location without actually leaking high-temperature, high-pressure water. Since the present invention is a leakage sound simulating sound source configured as described above, by using this device, high-temperature, high-pressure water can be safely and quickly removed without actually leaking.
You can easily evaluate the attenuation rate that determines the leakage sound detection range, and what's more, you only need to flow coolant at room temperature.
This can have excellent effects as it eliminates the need to use an electric heater and saves power.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of a pressure tube nuclear reactor, Fig. 2 is a block diagram of a leakage sound simulating sound source according to the present invention, Fig. 3 is a block diagram of a leakage sound detection device, and Fig. 4 is a conventional method and the present invention. It is a graph showing an actual measured comparative example of a method using the device. 10...Broadband piezoelectric conversion element, 11...
... Random signal generator, 12 ... AE sensor, 14 ... Main amplifier, 15 ... Effective voltmeter.

Claims (1)

[Claims] 1. A simulated sound source for coolant leakage sound, which is formed by combining a broadband piezoelectric transducer that is installed at a predicted leakage location and a random signal generator that supplies pulses with random pulse widths to the piezoelectric transducer.