JPH024846B2 - - Google Patents

Description

[Detailed Description of the Invention] <Technical Classification/Field> The disclosed technology detects leakage of flow-through material due to unexpected rupture of piping in pressure tube nuclear reactors, etc. by detecting ultrasonic waves generated during the leakage. Belongs to the field of surveillance technology.

<Explanation of the gist> Therefore, the present invention is a leak detector equipped with an ultrasonic sensor for detecting an unexpected leakage of leakage from the piping of a pressure tube reactor of a demonstration reactor of a new type of converter reactor. The present invention relates to a detection device in which a device for suppressing noise is attached to the leakage detection device in order to improve the S/N ratio in order to increase the reliability of the leakage detection device, and in particular, to and the noise source by clamping it to the piping,
This invention relates to a pipe leakage detection device in which a diffused reflector is formed on its surface to diffusely reflect ultrasonic waves transmitted through the surface.

<Prior art> As is well known, piping for transporting radioactive fluids or other potentially dangerous fluids is often used in nuclear power plants and chemical plants. Since there is a risk of serious trouble if this occurs, a system is normally installed to constantly monitor this type of rupture. If a rupture occurs in the inlet pipe of a pipe, the coolant will leak and cause serious consequences, so an AE (Acoustic Emission) sensor is installed in the pipe and a designated detection device is installed to monitor the leak. It is electrically connected to detect and monitor the ultrasonic waves emitted as a result of leakage.

In this case, the noise other than the leakage sound, which is the original detection target of the detection sensor, is detected by the above-mentioned AE (Acoustic
(emission) sensor, the detection S/N ratio decreases and the reliability of detection decreases.

In this type of pressure tube reactor, a recirculation pump is installed in the cooling piping, so
The problem is that the recirculation pump becomes a kind of noise source that is transmitted to the AE sensor through the surface of the piping, increasing the noise level and making the detection less reliable.

By the way, in general, as a means to improve the reliability of the S/N ratio, there is a means to increase the S (tonic),
There are ways to reduce N (noise), but since the magnitude of S (tonic sound) is originally determined as a physical phenomenon at the source, in order to improve the S/N ratio,
As a result, it is effective to reduce the noise level by some means.

As mentioned above, in the pressure tube reactor of the demonstration reactor of the new converter reactor, etc., when the above-mentioned AE sensor detects the ultrasonic waves generated when the coolant leaks from the fractured part of the cooling pipe, the above-mentioned noise is detected. The ultrasonic waves from the recirculation pump as a source have the disadvantage of propagating on the surface of the piping and reducing the reliability of detection, especially when the distance to the AE sensor of the recirculation pump is close. There was a problem that the negative effects were large.

Moreover, this kind of problem is often an inconvenience in chemical plants, and it has been desired to solve it.

<Object of the invention> The object of the invention is to improve the noise level when detecting the ultrasonic waves accompanying the emitted sound when the flowing fluid leaks due to an unexpected rupture by providing an AE sensor in the pipe based on the above-mentioned conventional technology. The problem of the condition that hinders the improvement of detection reliability due to the large size of By making effective use of the physical effect of attenuating the sound of pipe breaks by maintaining the It is an object of the present invention to provide an excellent noise suppression device for a pipe leakage detection device that reduces the undetected rate and phenomenon as much as possible and is beneficial to the field of piping application in the energy industry and heavy chemical industry.

<Configuration of the Invention> In order to solve the above-mentioned problems, the configuration of the present invention is such that when a break occurs unexpectedly in any part of the piping during plant operation, the fluid flowing inside leaks and the leakage occurs. The AE sensor detects the accompanying ultrasonic waves at high room temperature, and in that case, if there is a noise source near the fracture site, the ultrasonic noise from the source propagates on the surface of the pipe and the S/N ratio increases. This works to reduce the reliability of the detection of leaked ultrasonic waves from the above-mentioned rupture site by clamping the noise suppression device to the pipe between the noise source and the sensor. The propagating noise ultrasonic wave is diffusely reflected by the diffuse reflector formed on the surface of the noise suppression device, making it difficult to propagate to the sensor, and as a result,
Technical measures have been taken to reduce the noise level of the sensor and improve the S/N ratio, increasing the reliability of detection and making it possible to reliably detect and monitor pipe breaks. It is.

<Embodiment - Configuration> Next, one embodiment of this invention will be described below based on the drawings.

The illustrated embodiment is an embodiment applied to a pressure tube reactor of a demonstration reactor of a new converter reactor, and piping 2 provided between a reactor core (not shown) and a recirculation pump 1 (not shown with the same diameter for illustration convenience) The water drum 3 installed in a predetermined part of the
A sensor 4 is provided and electrically connected to a predetermined known leak detection device 5.

The AE sensor 4 detects an ultrasonic wave emitted from a coolant leak 7 at a break 6 that unexpectedly occurs in any part of the pipe 2, and the detection signal is transmitted to the leak detection device 5. It is supposed to be entered.

However, in the cooling piping 2, the recirculation pump 1 is provided close to the AE sensor 4, and as mentioned above, the recirculation pump 1 is a source of noise. The ultrasonic noise generated from the recirculation pump 1 propagates on the surface of the piping 2 and enters the AE sensor 4 from the water drum 3.
It serves to increase the noise level and lower the signal-to-noise ratio, thereby reducing the reliability of detecting the ultrasonic tonic of the leakage emission sound.

Therefore, in the present invention, a noise suppression device 8 is provided fixed to the piping at a location close to the water drum 3 between the AE sensor 4 and the noise source recirculation pump 1.

As shown in FIG. 4, the noise suppression device 8 is made up of a pair of half-split type, circular shapes of a predetermined length, and has flange portions 9 formed at both longitudinal ends thereof. 9 has a predetermined number of bolt holes 10,1
0... is drilled, and as shown in Fig. 1, a pair of half-shaped noise suppressing devices 8 are integrated and firmly tightened and fixedly clamped to the piping 2 by bolt nuts 11, 11... as clamps. It is becoming more and more common.

Each of the halves of the noise suppression device 8 has an inner surface 12 having the same shape as the outer diameter of the pipe 2 so as to be tightened to the pipe 2, while an outer surface thereof has the same shape as the outer diameter of the pipe 2. As shown in Figures 2 and 3, a concave groove 13 is formed perpendicular to the axial direction, and a relatively convex portion 14 is formed, and together, the surface is formed into a kind of labyrinth shape, resulting in diffused reflection. The ultrasonic piping 2 of the noise of the recirculation pump 1 forms the body 15
The AE sensor 4 is configured to diffusely reflect the amount of light propagating through the surface of the AE sensor 4 and prevent it from entering the AE sensor 4.

Therefore, since ultrasound propagates on the surface of an object,
When a foreign body comes into contact with the surface of the piping, it has the property of being suppressed. Therefore, the concave grooves 13, 13, .
The noise is attenuated by diffusely reflecting the noise ultrasonic waves, and the pitch of the grooves 13, 13... sets the frequency band to be attenuated from f ₁ to f ₂ (Hz).
Assuming that the speed of sound in a solid is α (m/s), the wavelength of the ultrasonic wave is α/f ₂ to α/f ₁ (m), so the axial pitch length of the groove 13 is formed to be shorter than this length. .

Note that the pitches do not have to be equally spaced.

The noise suppression device is made of a material that allows ultrasonic waves to easily enter the device from the piping, for example,
A metal such as SUS shall be selected and used.

Also, according to experiments, it is sufficient that the axial length of the noise suppression device 8 is about 2 to 4 times the diameter of the pipe, and that the depth of the groove is half of the ultrasonic wave of the noise to be suppressed. In this case, a wavelength of about 5 mm is sufficient.

<Example - Effects> In the above configuration, when the pressure tube reactor of the demonstration reactor of the new type converter reactor is in operation and a predetermined coolant is flowing through the cooling pipe 2, a rupture occurs unexpectedly. When this occurs, the flowing coolant leaks 7 to the fractured portion 6, and the emitted sound generates an ultrasonic wave.The AE sensor 4 installed in the water drum 3 detects this, and a predetermined leak detection device 5 detects it. Send a signal.

Meanwhile, the ultrasonic waves generated by the noise generated by the recirculation pump 1 during operation propagate on the surface of the cooling pipe 2 and reach the sensor 3 via the water drum 3.
However, the noise is suppressed by the noise suppression device 8 and reflected diffusely by the diffuse reflector 15 on the surface of the noise suppressor 8, and the noise level is considerably lowered by the sensor 4.
Therefore, the S/N ratio in the sensor becomes relatively large.

Therefore, the reliability of detection by the sensor 4 becomes high, and the leakage portion 6 of the pipe 2 is detected by the leak detection device 5 more reliably.

An experimental example based on the above-mentioned example is shown in Fig. 5. The vertical axis represents the sound pressure V (μV), and the horizontal axis represents the position of the pipe (m).The correct sound pressure on the vertical axis is logarithmic. The horizontal axis is assumed to be displayed on a linear scale.

According to experiments, when the noise suppression device 8 of the present invention is not provided, the graph shown in L shows an attenuation of about 0.3 bB per 1 m in the 100 KHz to 200 KHz band, depending on the detection frequency band. It can be seen that by providing the noise suppressor 8 of the present invention, an attenuation of several bB is produced and the noise level entering the AE sensor 4 is reduced.

Note that the position AB shown in FIG. 5 is the detection position at the position AB before and after the noise suppressor 8 of the present invention shown in FIG. 1 is installed in the pipe 2.

Furthermore, it goes without saying that the embodiments of the present invention are not limited to the above-mentioned embodiments. For example, the pipes to which the noise suppression device is installed are not limited to the pressure tube type nuclear reactor of the demonstration reactor of the new type converter reactor, but are It can also be attached to a piping rupture monitoring device in a processing chemical plant, and can be attached to the piping.Also, as a design change, the above-mentioned diffuse reflector may have a concave groove that is not horizontal but curved inward, or a convex shape. Various embodiments can be adopted such that the distal end thereof can protrude outwardly in a curved manner or in a tapered shape.

<Effects of the Invention> As described above, according to the present invention, basically, ultrasonic waves that are electrically connected to a leakage detection device in a pipe rupture monitoring system of a pressure tube nuclear reactor of a demonstration reactor of a new type converter reactor or a chemical plant. By installing a noise suppression device next to the ultrasonic sensor piping when a sensor is installed in the piping, the ultrasonic noise generated at the bent and reduced part of the piping near the ultrasonic sensor in the piping is suppressed. The noise suppression device attenuates the noise while it propagates on the piping surface, lowers the noise level at the sensor, and as a result, increases the S/N ratio, making it easier to detect the main sound of the leaked sound due to the pipe rupture compared to the ultrasonic wave. The reliability of the system is improved, and as a result, the pipe rupture monitoring efficiency is improved, which is an excellent effect.

Since the noise suppression device is fixed to the piping via a clamp, it is easy to install and does not require maintenance, inspection, maintenance, etc., and does not require maintenance costs. There are also benefits in terms of management.

In addition, since many concave grooves, convex, etc. diffuse reflectors are formed on the surface of the noise suppression device, the components of the ultrasonic waves emitted by the noise source that propagate on the surface of the piping. is diffusely reflected by the diffuse reflector and is suppressed from entering the sensor.As a result, as mentioned above, the noise level is lowered, the S/N ratio is increased, and the error rate of the monitoring system and the undetected rate of decrease are lowered. The excellent effect of being able to do this is achieved.

Therefore, the noise suppression device has a backup function that can more fully demonstrate the original function of the conventional leak detection device, and since it only needs to be installed on the piping of a nuclear power plant or chemical plant, The synergistic effect has the advantage of being significantly more effective.

[Brief explanation of drawings]

The drawings are explanatory diagrams of one embodiment of the present invention, in which Fig. 1 is a schematic perspective view of the whole, Fig. 2 is a half-split plan view of the noise suppression device, Fig. 3 is a side view of the same, and Fig. 4 is an end view. FIG. 5 is a graph of experimental data. 2... Piping, 4... Ultrasonic sensor, 5... Leak detection device, 8... Noise suppression device, 7... Noise source, 11... Clamp, 13, 14, 15... Ultrasonic diffused reflector.

Claims (1)

[Claims] 1. In a noise suppression device for a leak detection device in which an ultrasonic sensor for detecting leakage is installed on a pipe, the ultrasonic sensor is fixed to the pipe between the ultrasonic sensor and the noise source via a clamp, and the surface of the pipe is fixed to the pipe, and the ultrasonic diffused reflection occurs on the surface of the pipe. A noise suppression device for a pipe leak detection device, characterized in that a body is formed.