JP3041728B2 - Ultrasonic detection method for gas phase appearing in liquid phase in room - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to the monitoring of a liquid phase in a room which monitors such a liquid phase in order to ascertain the appearance of air bubbles which may be inside the liquid entering or flowing into the room.
The present invention relates to a method for detecting an ultrasonic wave in a gas phase .

[0002]

BACKGROUND OF THE INVENTION The problem of monitoring is, in certain industrial fields, more precisely and characteristically, that the water of the steam generator is cooled by liquid sodium and the water or steam leaks from the steam generator tubes. This occurs in the case of a steam generator of a fast neutron reactor in which the contact with sodium is displayed as quickly as possible.

In fact, the reaction of sodium to water is a violent chemical reaction, producing hydrogen bubbles, the appearance of which, in conjunction with other phenomena, causes very serious damage to the interior of the steam generator. Cheap. It is therefore essential that once this leak appears, ie as soon as hydrogen bubbles start to appear in the steam generator, before it can cause significant damage, it can be detected.

Heretofore, in the prior art, the presence of a gaseous phase in a liquid was superimposed in direct contact with the liquid so that it was not affected by unwanted signals that would necessarily occur against the walls of the chamber containing the liquid. It has been detected with the help of a sound wave transmitter / receiver system. These systems are described in French patent FR-A-7337233.

[0005]

However, such a method has the serious disadvantage that the walls of the chamber containing the liquid phase must be perforated so that the transducer can be installed. For this reason, the structure is easily broken, and it is also necessary to perform pre-positioning for accurately determining a measurement point.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an apparatus for detecting the appearance of a gas phase in a liquid phase in a room or flowing into the room without entering the interior of the room itself and detecting the gas phase in the liquid phase in the room. Super
It is to provide a sound wave detection method .

[0007]

SUMMARY OF THE INVENTION This method can be used within a very short time of one second and when there is a large amount of background noise, such as the wideband background noise of a steam generator at nominal power. It is easily implemented by disclosing the liquid / gas phase to be installed.

The method comprises the steps of: using at least one ultrasonic transmitter, through a system consisting of a chamber and a liquid, at a frequency above 20 kHz and a short duration of about 10 ^-3 s and a sufficient time interval; Passing a wave train having preferably about 10 ^-1 s to 10 ^-2 s so that the received signals collected at their outlets of the room do not overlap;-using at least one supersonic receiver; Detecting the entire exit signal transmitted through the liquid phase / chamber system; separating the effective part corresponding to the passage of the liquid phase from the whole received signal; Detecting possible attenuation of the amplitude characteristic of the existing gas phase.

As will be seen, the method of the present invention comprises a chamber traversed by a beam of ultrasonic waves and the liquid contained therein to detect the transparency of the liquid phase to ultrasonic radiation periodically several times per second. It is configured with a system.

If there is no leak, and thus no reaction of sodium to water, this is the case for a sodium-cooled reactor steam generator, but the aforementioned clarity is at its maximum. On the other hand, at any point in the liquid medium
Phase / gas phase , ie bubbles in the ultrasonic path in effect
As soon as it appears, these bubbles immediately cause ultrasonic energy
Forfeits are lost and the aforementioned transparency decreases fairly quickly.

According to the method of the invention, it is not necessary at all to penetrate the walls of the chamber before performing the measurement, and the ultrasonic transmitter is, like the ultrasonic receiver, the chamber of the chamber constituting the liquid phase. Because it is installed outside, it relates to non-intrusive active sound detection. Furthermore, each ultrasonic transmitter and receiver can be directly connected to the room by fixing directly to the outer surface of the room wall, or on the other hand, installed at a certain distance from the room, i.e. welded to the room A waveguide can be connected to the chamber wall.

Applicants believe that the frequency exceeds 20 kHz and has a duration of about 10 ^-3 s and a sufficient time interval (preferably 1
It has been demonstrated that the use of a wave train with 0 ^{-1 to} 10 ^-2 s) as the ultrasound source makes it possible to avoid overlapping of the received signals collected at the exit of the room. Furthermore, if the wave train emitted at the entrance of the system has a constant amplitude and is sufficiently far in time from each other, signals will be received at the exit of the chamber and those signals will be received in various environments (chamber, liquid, Due to the various propagation speeds of ultrasonic waves at possible obstacles inside the room, etc.
Second, it shows several different amplitude peaks, each corresponding to a particular ultrasound path in the system. It is then sufficient to separate from these successive amplitude peaks those that correspond to the useful part of the signal, ie those that correspond to the transition of the ultrasound through the liquid phase.

In the particular case of a sodium / water exchange steam generator of a nuclear reactor, said separation of the active ingredients is facilitated by taking advantage of the different ultrasonic velocities in the following three media constituting the system: It can be carried out. 6000 m / s in steel, 2200 m / s in sodium and 15 in water
00 m / s.

According to the invention, the detection of the active component of the signal is synchronized with the start of the emission of each wave train, but with a delay corresponding to the appearance of a particular amplitude peak of the ultrasonic transition in the liquid. Have and do.

By experimentally calibrating the apparatus in advance, by the time when the effective part of the signal appears after the start of injection of each wave train, and secondly, by experimentally injecting gas into the liquid to be monitored, Both the critical amplitude threshold, i.e., the value below which the useful signal collected exhibits a sufficiently wide range of amplitude attenuation so that it is possible to confirm the presence of the gas phase in the path of the ultrasound. It becomes possible to do.

[0016]

In any event, the present invention will be more readily understood by reading an embodiment of the invention, which is illustrated schematically with reference to FIGS. By way of example, and not by way of limitation, this example relates to the case of monitoring a sodium / steam generator of a sodium cooled fast neutron reactor.

FIG . 1a shows the square pulses 2 and 4 which synchronize the course of the method as a function of time expressed on the abscissa. In other words, pulses 2 and 4 are transmitted through a time axis and a system during which wave trains 6 and 8 consist of the steam generator chamber, the sodium entering the chamber, and the water tube traversing the chamber. Defines the strobe to be transmitted and injected.

As can be seen in FIG. 1b, the wave trains 6 and 8
Have a constant amplitude and are the same for both. According to the invention, the wave trains 6 and 8 are at least 20 kHz
And a duration of about 10 ^-3 s, separated by about 10 ^-1 s.

FIG. 1c shows the signal collected at the outlet of the steam generator chamber as it exits the steam generator. This figure also illustrates some phenomena.

First, the time movement of the received wave train 6a corresponds to the wave train 6, and 8a corresponds to the wave train 8. This time movement, of course, corresponds to the transition time of the ultrasonic signal through the transverse structure. Another phenomenon that can be seen in this FIG. 1c is that the received wave trains 6a and 8a are time-stretched with respect to the radiated wave trains 6 and 8. This elongation results from the different propagation velocities of the ultrasonic waves in the various traversing media (steel, sodium,...) And the multiple reflections of the ultrasonic beam from various elements on its path . Finally, the total raw signal received should be as shown in the phase shown in FIG. 1c, adding the background noise visible at 10 to the previous two variants.

Another important observation underlying the practice of the present invention arises from the particular shape of the exit wave trains 6a and 8a shown in FIG. 1c. In fact, each of them is actually composed of an amplitude variation split into three peaks: one inlet peak 12, one intermediate peak 14, and one outlet peak 16. These interpretations are straightforward. The inlet peak 12 corresponds to the transition of the wave train in the steel structure of the steam generator, whose propagation speed of 6000 m / s is effectively the highest. The central amplitude peak 14 corresponds to a signal transmitted by a liquid, in this example, sodium, at a speed of about 2200 m / s. Regarding the third amplitude peak 16, this is due to the various reflections in liquid sodium of the first wave train by the traversed or encountered structure.
As explained earlier, it is composed of three amplitude peaks,
Selection of various frequencies and selection so that continuous wave trains do not overlap
Using this particular form obtained by choosing
This makes it possible to implement a detection method by selecting the part of the signal corresponding to the transmission of ultrasonic waves by the liquid, which makes it possible to detect the appearance of a series of bubbles very quickly.

To achieve this, the procedure is as follows. First, as shown in FIG. 1d, the background noise is removed and a profile of the maximum amplitude of the received signal is constructed, thus the three amplitudes 12, 14, and 16 in the profile representing the actual value of the signal. Just specify.

Next, it is necessary to select one characteristic of the transmission of the liquid phase from these three peaks. Generally speaking and in the example represented in FIGS. 1e and 1f, the central peak is selected. Synchronous detection is performed by opening a selection strobe having a period Δt at the end of time τ that allows the selection of a calibrated pulse having the maximum amplitude of the central peak 14. However, in some cases-for example, if the chamber is large and has a large number of internal structures-it may be advantageous to select a peak 16 due to multiple reflections of the wave train due to the internal structure in liquid sodium. .

Using a device which has been pre-calibrated based on known conditions and by carefully and well-adjusting the gas flow into the liquid, below which the decay of the amplitude 14 necessarily implies a gas phase An alarm threshold 18 signifying occurrence is experimentally determined.

FIG. 2 schematically shows a sodium-cooled reactor sodium / water steam generator which is passed by a metallic steel chamber 22, a liquid sodium phase 24 and water. A heat exchange tube 26 is provided.

The apparatus is used as shown in FIG. 2 to monitor what is occurring inside the steam generator 20, especially the appearance of hydrogen bubbles in the sodium 24.

The synchronization pulse generator 28 generates a pulse such as the pulses (2 and 4) in FIG. 1a. These pulses then control a sine wave generator 30 at the ultrasonic frequency, which generates the wave trains 6 and 8 of FIG. 1b. These trains at the outlet of the generator 30 are amplified by an amplifier 32 and then guided by a waveguide 36 to the outer wall 22 of the steam generator 20.
To excite the radiation transducer 34 coupled to. The wall 22 of the steam generator 20 thus generated
The ultrasonic train carried by the tube spreads through the system described above and is then collected by the waveguide 38 and the receiving transducer 40. The received train is in the form shown in FIG. 1c, but is then preamplified at 42 and 44
Amplified by

The received composite signal is therefore the first, corresponding to the transmission by the structure, ie the wall 22 of the chamber of the generator 20.
, A central portion corresponding to transmission through the liquid, and broadband background noise obtained from the steam generator. This composite signal corresponds to that of FIG.
It is then filtered for a narrow band centered on the emission frequency of the wave train to minimize background noise, and then, as shown in FIG. 1d, a device 46 consisting of a narrow band filter and an actual value shaper. Formed according to the actual value of

Subsequently, when using a window of width Δt
The delay synchronous detection of the interval τ is performed by the synchronous detector 48 operating in synchronization with the synchronous generator 28 . If the signal of FIG. 1f is obtained at the output of this synchronous detector 48, these signals are then compared in a comparator 50 with the alarm threshold 18 of FIG. Is experimentally predetermined. The peak of the signal 14 received by the comparator 50 when the signal amplitude reduction or attenuation is
If so, it is now possible to infer the presence of a gas phase on the ultrasound path that caused this considerable attenuation of the energy of the ultrasound wave train.

The apparatus of FIG. 2 performs detection for a period of about 1 s and for an equivalent water flow of less than 1 g / s, a length of 18 g / s.
m, which made it possible to carry out the method according to the invention, which revealed a water leak from a straight pipe of 0.4 m diameter in less than one second.

For certain applications, for example in the case of large rooms with a large number of internal structures, it may be advantageous to secure some radiating transducers 34, in particular some receiving transducers, to the room.

[0032]

By way of the primary one from the advantages of the detection method of the present invention according to the present invention are as follows, it is possible to draw the very fast response time of less than 1 second, generally predicates
In other words, with regard to the quality of the measurement, the system
Minimal leakage due to minimal background noise
Even so, the leak detection is highly sensitive and does not enter the room through which the monitored liquid phase passes. Furthermore,
Because the transducers are outside the chamber, they are always accessible and can operate without unacceptable overheating when the liquid phase is hot.

[Brief description of the drawings]

1a to 1f show the operating stages of the method from various signals transmitted, received and analyzed.

FIG. 2 shows a simplified diagram of an apparatus for detecting the appearance of hydrogen gas in the sodium of a steam generator with the aid of the present invention by means of ultrasonic waves.

[Explanation of symbols]

 2,4 square pulse 6,8 wave train 10 background noise 12 inlet peak 14 intermediate peak 16 outlet peak 20 steam generator 22 chamber 24 liquid sodium 26 heat exchange tube 28 pulse generator 30 sine wave generator 32,42,44 amplifier 34 Emission Transducer 36,38 Waveguide 40 Receive Transducer 46 Narrow Band Filter and Actual Value Shaper 48 Synchronous Detector 50 Comparator

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-62-115358 (JP, A) JP-A-53-36295 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G21C 17/025 GDF G01N 29/20 JICST file (JOIS)

Claims (7)

(57) [Claims] 1. A method for ultrasonically detecting a gaseous phase appearing in a liquid phase in a room, comprising: using at least one ultrasonic transmitter, having a frequency exceeding 20 kHz and continuing for about 10 ⁻³ s. Passing, through a liquid / chamber system consisting of a chamber and a liquid, a wave train, which is sufficiently spaced apart that the received signals collected at the outlet of the chamber do not overlap; Using, to detect the entire exit signal transmitted through the liquid phase / chamber system; separating the effective portion corresponding to the passage of the liquid phase from the entire received signal; Detecting a possible attenuation of the amplitude characteristic of the gaseous phase present in the gaseous phase in the liquid phase. 2. The sufficient time is about 10 minutes. ^-1 s and 10
^-2 2. The time interval between s and s.
Method for detecting the gas phase appearing in the liquid phase in the room. 3. The wave train at the liquid / chamber inlet.
Having a constant amplitude, at the outlet of the liquid / chamber system
Wave trains are time calibrated and each is in the liquid / chamber system
Have several amplitude peaks corresponding to a particular ultrasound path
The detection is based on the occurrence period of the start of each wave train.
Between, but with the specificity of the ultrasound transition through the liquid phase
Synchronized with the delay corresponding to the appearance of the amplitude peak, this
Allows to select the valid part of the signal
2. Appearing in the liquid phase in the room according to claim 1, characterized in that
Ultrasonic detection method for gas phase. 4. The presence of a gas phase in said liquid phase indicates the presence of said signal.
The amplitude of the effective part causes the gas to be injected into the liquid during calibration.
More experimentally lower than a predetermined threshold
2. The method according to claim 1, wherein the fact is detected.
4. The method for detecting ultrasonic waves of a gas phase appearing in a liquid phase in a room according to 3. 5. The liquid / chamber system at an inlet and an outlet.
The ultrasonic transmitter and / or the ultrasonic receiver,
Being fixed directly to the outer surface of the chamber wall Characterized by
2. Ultrasonic detection of a gas phase appearing in a liquid phase in a room according to claim 1.
How to get out. 6. At the inlet and outlet of the liquid / chamber system.
The ultrasonic transmitter and / or the ultrasonic receiver,
With the waveguide welded to the chamber, the outer surface of the chamber wall
The room according to claim 1, wherein the room is connected.
Ultrasonic detection method of gaseous phase appearing in liquid phase. 7. Reactor steam generation cooled by liquid metal
When monitoring for leaks in livestock, this metal
Said steam generator with a leak in one of the generator water tubes
Of hydrogen gas in the metal by acting on
7. The method according to claim 1, wherein the current is monitored.
Gas phase ultrasonic waves appearing in the liquid phase of a room described in one of the above
Application of detection method.