JPS59214726A - Ultrasonic wave thermometer - Google Patents

Abstract

PURPOSE:To obtain an ultrasonic wave thermometer, which can measure temperature distribution highly accurately, by constituting a sensor itself as a magnetic body in which a notch is not formed, and generating magnetostrictive ultrasonic waves at positions having specified interval in said magnetic body. CONSTITUTION:Permanent magnets 7 are attached to the inner wall surface of a sheath 1 as a material corresponding to a notch position. In this case, a magnetic field formed in a pulse mode. Then, a magnetostriction ultrasonic waves are simultaneously formed at the part of a sensor 6 in the vicinity of each permanent magnet 7, by said magnetic field and the magnetic field of the magnet 7. The magnetostrictive ultrasonic wave is received as a pulse train at one end of the sensor 6. The ultrasonic wave is received by a magnet 11 and a coil 12, which are attached to a sheath 1. A cylinder shaped projection 14 comprising the same material is provided at one end part of the sensor 6. The coil 12 is arranged so that the projection 14 is enclosed in the inside of the coil 12. The magnet 11 is arranged in the vicinity thereof. The cylinder shaped projection 14 is vibrated in the axial direction by the magnetostrictive ultrasonic wave. Thus the magnetostrictive ultrasonic wave can be received by the coil 12.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to an ultrasonic thermometer using magnetostrictive ultrasonic waves.
In particular, the present invention relates to an ultrasonic thermometer suitable for measuring temperature distribution inside a nuclear reactor.

[Background of the invention]

For example, when a nuclear reactor becomes abnormal, it is necessary to understand the condition inside the reactor in detail, so the temperature distribution inside the reactor is measured. Figure 1 shows the configuration of a conventional ultrasonic thermometer that is suitable for measuring temperature distribution, but with this, temperature distribution cannot be measured with great precision. There is.

That is, the cylindrical sensor 2 has notches at regular intervals.
3 are formed, and the sheath 1 protects them. An ultrasonic transmitting/receiving element 4 is attached to one end of the cylindrical sensor 2, and the ultrasonic waves transmitted from the ultrasonic transmitting/receiving element 4 to the cylindrical sensor 2 are reflected at the notch 3 and then sent to the ultrasonic transmitting/receiving transmitter. 4. In this case, since a plurality of notches 3 are formed, the reflected ultrasound is obtained as a pulse train for the ultrasound transmitted in a pulsed manner, and the pulse time interval of this reflected ultrasound is determined by the signal processing device 5. However,
From this and the spacing between the notches 3, the average sound velocity between the notches 3, and the relationship between the sound velocity and the sound intensity, the temperature at each of the notches 3 can be determined.

FIGS. 2(a) and 2(b) schematically show partially omitted vertical and cross sections of the ultrasonic thermometer shown in FIG. 1 with respect to the sheath 1 and the cylindrical sensor 2. By the way, the specific values of the dimensions a to d shown in the diagram are 100 fins, respectively.
10 kan, 0.5 yen, 1.5 frost. This is the smallest sensor unit currently available.

Although the temperature distribution in the axial direction of the cylindrical sensor is thus known, the temperature distribution cannot be measured with great precision. The cause of this is that the ultrasonic waves are multiple-reflected by multiple notches, and the number of reflected ultrasonic waves received by the ultrasonic transmitting/receiving element exceeds the number of notches, or that the ultrasonic waves are disrupted by multiple notches. This is required because the waveform of the reflected ultrasonic wave is disturbed, such as when the sound wave is attenuated and the amplitude of the reflected ultrasonic wave becomes smaller.If we compare the measurement results using an ultrasonic thermometer with those using a thermocouple, we can see the results shown in Figure 3. It is. Figure 3 is based on the experimental results by Gronager et al. at the Sampuia National Laboratory.
There is a variation of about C.

[Purpose of the invention]

Therefore, an object of the present invention is to provide an ultrasonic thermometer that can measure temperature distribution with high accuracy.

[Summary of the invention]

For this purpose, the present invention is such that the sensor itself is constructed as a magnetic body without a notch, and magnetostrictive ultrasonic waves are generated at predetermined spaced positions on the magnetic body.

[Embodiments of the invention]

The present invention will be explained below with reference to FIGS. 4 to 16.

First, the general general structure of the ultrasonic thermometer according to the present invention will be explained. FIG. 4 shows its configuration.

According to this, a hollow cylindrical sensor 6 is disposed inside a cylindrical stainless steel sheath 1, and a copper core wire 13 is disposed on the central axis inside the sensor 6. In this case, the sensor 6 itself is constructed of a magnetic material made of iron-nickel alloy, and dampers 8.9 for preventing ultrasonic reflection are attached to both ends thereof. The core wire 13 is also grounded at one end to the sheath 1 and connected to the electric pulse generator 10 at the other end. When a pulse current is caused to flow through the core wire 13 from the electric pulse generator 10, a circular magnetic field centered around the core wire 13 is generated in the entire interior of the sensor 6 in the form of a pulse. Therefore, if permanent magnets 7 are attached at regular intervals on the inner wall surface of the sheath 1 as equivalent to the notch position, when a pulsed magnetic field is generated, this magnetic field and the magnetic field from the magnets 7 will cause each permanent magnet to Magnetostrictive ultrasonic waves are simultaneously generated in a portion of the sensor 6 near the magnet 7, and these magnetostrictive ultrasonic waves can be received as a pulse train at one end of the sensor 6. In this example, ultrasonic waves are received by a magnet 11 and a coil 12 attached to the sheath 1. A cylindrical projection 1 made of the same material is provided at one end of the sensor 6.
4, the coil 12 is arranged so that the protrusion 14 fits inside the coil 12, and the magnet 11 is arranged near the coil 12 as shown in the figure, then the cylindrical protrusion 14 is moved in the axial direction by magnetostrictive ultrasonic waves. Since the coil 12 vibrates, it is possible to receive magnetostrictive ultrasonic waves. The magnetostrictive ultrasonic reception signal from the coil 12 is processed by the signal processing device 5, which will be described later.

FIGS. 5(a) and 5(b) show a specific manner in which the sensor and the core wire are attached inside the sheath, partially in longitudinal section and in cross section. According to this, the sensor 6 is attached to the sheath 1 by the holding member 15 made of silicone rubber, and the core wire 13 is attached and held to the sensor 6 by the holding member 16 also made of silicone rubber without contacting it. There is. By the way, in this example, 7-south 1 outer diameter, sensor 6
The outer diameter and core wire 13 diameter are 2wn, 0.5mm, and 0.5mm, respectively.
It's 2 fights.

FIG. 6 shows a specific circuit configuration of an example of an electric pulse generator for passing a pulse current through a core wire. As shown in the figure, when the switch 17 is closed by an external control signal, the one-shot circuit 19 is triggered via the inverter 18 at that point, and the reset output of the one-shot circuit 19 is outputted through the transistor 20. A pulse current is output from the terminal 26 with a predetermined pulse width.The pulse width of the pulse current is at least 1
It is adjusted to about 0nS.

Note that numerals 22 to 25 indicate resistances.

FIG. 7 specifically shows some circuits in the signal processing device. According to this, the magnetostrictive ultrasonic reception signal from the coil 12 described above can be obtained as shown in FIG.
This received signal is input to the peak value detection circuit 34 in a suitably preprocessed form. The magnetostrictive ultrasonic reception signal A converted into the form shown in FIG. 8 by preprocessing is inputted to a so-called ideal diode consisting of an operational amplifier 27 and a diode 28 via a resistor 35, and its peak value is determined to be dischargeable. It is detected and held by a capacitor 30. The detected and held peak value signal B can be monitored as the output of the operational amplifier 29 as a buffer, but the point in time when the peak value is obtained is the output of the operational amplifier 27.
The output CjJ of is to be detected. In addition to functioning as part of the ideal diode, the operational amplifier 270″i
When the voltage of the capacitor 30 is lower than the input voltage, the comparator 32 also functions as a comparator and detects the fall of the output C. The fall detection output of the output C is partially obtained as a pulse width, but each time the detection output is obtained, the capacitor 30 is reset and controlled before the next input magnetostrictive ultrasonic signal. By doing so, the time points at which peak values are obtained can be continuously detected. The capacitor 30 is reset by turning on the analog switch 31 using the detection output through the delay circuit 33, but the delay time of the delay circuit 33 is appropriate in order to continuously detect the point at which the peak value is obtained. need to be established.

Now, since the detection output is calculated as 4f at the time when the peak value is obtained, the time interval between the detection output and the detection output can be directly obtained as the time interval of the magnetostrictive ultrasonic reception signal. In the time interval counting/processing circuit 36, a flip-flop 37
is inverted every time a detection output is obtained, and AND gates 39 and 40 are alternately selected by the outputs E and H. While the AND gate 39 is selected, the high rate lock signal from the clock generation circuit 38 is counted by the counter 41 via the AND gate 39, and while the AND gate 40 is selected, the clock signal is It is counted by a counter 42 via a gate 40. The one-shot circuit 43 is for resetting the counters 41 and 42 at a predetermined timing to prepare for the next counting operation. counters 41, 42
The count value (binary) is then converted into a BCD code by a BC'D code converter 44, 45, and is alternately and selectively outputted from a multiplexer 46 under the control of a one-shot circuit 43 for processing. It is something.

The following is an explanation of how the temperature can be determined from the counted time intervals.

That is, if the interval between permanent magnets is L (e) (constant) and the counted time interval between the permanent magnets is τ (S), then the average sound speed U (m/s) between the permanent magnets is It will look like this:

U=, L/τ On the other hand, according to experiments, the relationship between the average sound speed U and temperature (C) is as shown in Figure 10 when an alloy with a 1:1 ratio of iron and nickel is used as a sensor. I realized that. That is, since the speed of sound has temperature dependence, if it is known in advance what kind of temperature dependence the sensor has, the average temperature can be determined from the determined average sound speed. In this case, the material of the sensor may be pure metal, but when it is made of alloy, the speed of sound is low and the time interval, and thus the temperature, must be determined with good precision. When using an alloy as a sensor and suppressing ultrasonic reflection on the sensor itself, the ultrasonic waveform to be received will not be disturbed, so the temperature can be determined with an error of about ±5C. .

Although the present invention is as described above, other embodiments of the present invention will be described next.

First, referring to FIG. 11, a case will be described in which ultrasonic waves are received by a piezoelectric element. As shown in the figure, a piezoelectric element 47 is provided on one end side of the sensor 6, and a damper 48 is provided on the side facing the surface in contact with the sensor 6. The ultrasonic receiving mechanism is simpler than those described above, and is advantageous in terms of cost and failure rate.

Next, the case where the permanent magnet is configured as an electromagnet will be explained with reference to FIGS. 12(a)' and 12(b). Figure 12 (a
).

5(b) corresponds to FIGS. 5(a) and 5(b), but as shown, an electromagnet 5 is placed in place of the permanent magnet 7.
The electromagnet 50 is driven at a constant current by a constant current power source 49.

According to this embodiment, the magnetic field strength can be kept constant, and problems such as temperature dependence of the magnetic field can be solved.

Finally, other aspects of the signal processing device will be explained. 1st grade
Figure 3 shows its configuration. As shown in the figure, the time interval counting/processing circuit is left as it is, and a comparator 51 is provided at the preceding stage. The comparator 51 outputs a pulse signal with a constant pulse width when the magnetostrictive ultrasonic reception signal A exceeds the reference voltage ■r.

According to this aspect, although the time interval is not counted as the interval between peaks, it is possible to simplify the configuration, reduce costs, and reduce the failure rate.

M: Application examples of the ultrasonic thermometer according to the present invention will be explained. FIG. 14 shows the case of measuring the temperature distribution inside the light water reactor pressure vessel, and is 7ζ. Inside the pressure vessel 52, a steam separator 53, a reactor core 55, a jet pump 54, etc. are housed as shown, but in this example, a thin tube 57 housing a neutron detector (not shown) is housed inside the pressure vessel 52. A temperature sensor portion 59 is housed inside the temperature sensor portion 59. The thin tube 57 is connected to the pressure vessel 52, the shidarankama 56, and the steam/water separator 53 via the reactor core 55.
Although the temperature sensor portion 59 is provided over the lower part, if the temperature sensor portion 59 is provided inside the pressure vessel 52, the temperature distribution inside the pressure vessel 52 can be easily determined with good accuracy. Therefore, since the temperature distribution over a height of about 10 m can be easily known, if the ultrasonic thermometer according to the present invention is installed in the pressure vessel in advance, the condition inside the reactor can be accurately grasped in the event of an accident. become. Note that the instrumentation device 58 includes an electric pulse generator, a signal processing device, and the like according to the present invention.

Next, a case where the present invention is applied to a fast breeder reactor will be explained as shown in FIG. As shown in the figure, a reactor core 63 is disposed at the center inside the primary vessel 60, a blanket 64 is arranged around the core 63, and a primary heat exchanger 61 and a pump 62 are arranged between the center and the inner wall of the vessel. It has become a thing. A control driving mechanism 65 is located above the reactor core 63, and the reactor core 63, primary heat exchanger 61, pump 62, etc. are located in a sodium coolant 66, and a temperature sensor according to the present invention is installed in this sodium coolant 66. If the portion 59 is inserted as shown, the temperature distribution inside the container can be known as in the previous case. In particular, in a rapid increase/extinguisher reactor, the low-temperature sodium coolant injected at the time of the accident remains at the bottom of the primary vessel, while the high-temperature sodium coolant stagnates at the top of the vessel, resulting in a large temperature difference between the bottom and top of the primary vessel. Therefore, temperature distribution 611] is necessary for thermal stress evaluation. The ultrasonic thermometer according to the present invention can measure temperature distribution with high accuracy over a height of about 7 m, and is effective in accurately evaluating the strength of structural materials.

Finally, a case where temperature distribution is measured two-dimensionally will be explained. Until now, the temperature sensor portion has been explained and illustrated as having a linear shape, but its shape is not necessarily limited to a linear shape. Figure 16(a)-(C
) are the front and bottom surfaces (611) of an example of the ultrasonic thermometer according to the present invention when the temperature distribution is determined two-dimensionally (611), respectively.
According to this figure, the temperature sensor part 67 is bent into a comb-shaped serpentine shape, and the entire part is mounted and supported by a plate-shaped holding member 68. It has become something that will be done. However, in this example, the above-mentioned permanent magnet or electromagnet is not provided inside the temperature sensor portion 67, and instead, a rectangular bar-shaped permanent magnet 69 mounted on the holding member 68 is used instead. It has become. If the temperature sensor part is configured two-dimensionally ((η), the temperature distribution can be obtained in all two dimensions. Therefore, if we extend this idea and configure the temperature sensor part five-dimensionally, we can obtain the temperature distribution three-dimensionally. It is also possible to determine the temperature distribution based on the sensor (6) itself.If the magnitude of the pulse current applied to the core wire (13) is appropriately set depending on the length of the sensor (6) itself, magnetostrictive It becomes possible to receive ultrasonic waves in good condition.

〔Effect of the invention〕

As explained above, the present invention simultaneously generates magnetostrictive ultrasonic waves in a plurality of predetermined portions of a sensor whose both ends are non-reflective ends, and allows the ultrasonic waves to be received in good condition at one end of the sensor. This is what I did. Therefore, according to the present invention, since ultrasonic waves are received with good waveform conditions, the temperature distribution can be measured with high precision.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of an ultrasonic thermometer according to the prior art, FIGS. 2(a) and 2(b) are partial longitudinal and cross-sectional views of the ultrasonic thermometer, The figure also shows the temperature measurement results by the ultrasonic thermometer along with those by the thermocouple, and Figure 4 schematically shows the configuration of an example of the ultrasonic thermometer according to the present invention as a partially broken piece Figures 5(a) and 5(b) are partial vertical and cross-sectional views of the ultrasonic thermometer, and Figure 6 is an example of the electric pulse generator shown in Figure 4. FIG. 7 is a diagram specifically showing the configuration of an example of a partial circuit of the signal processing device in FIG. 4, and FIG. 8 is a diagram for explaining the circuit operation. FIG. 9 is a diagram showing an example of the input/output signal waveform in the main part of the signal, FIG. 9 is a diagram showing the signal waveform in an example of the magnetostrictive ultrasonic reception signal, and FIG. 11 is a diagram showing the structure of an ultrasonic thermometer according to the present invention in a partially broken state in a case where magnetostrictive ultrasonic waves are received by a piezoelectric element, and FIG. Figures 12(a) and (+) are partial vertical cross-sections of the ultrasonic thermometer according to the present invention when the permanent magnet is configured as an electromagnet (a diagram showing the new surface of the cap), and Figure 13 is a diagram showing the signal processing Figures 14 and 15, which show other configurations of the device M, are diagrams showing the application of the ultrasonic thermometer according to the present invention to light water reactors and fast breeder reactors, and Figures 16 (a) and (b). ) and (c) are views showing the front, partially omitted bottom, and partially omitted right side of an example of the ultrasonic thermometer according to the present invention for two-dimensionally measuring temperature distribution. 1.・Sheath, 5...Signal processing device, 6...Sensor, 7...Permanent magnet, 8,9.48...Damper, 1
0... Electric pulse generator, Engineering 1... Magnet, 12.
... Coil (for ultrasonic reception), 13 ... Core wire (for pulsed magnetic field generation), 47 ... Piezoelectric element, 49 ... Constant current power supply, 50 ...' Electromagnet. Agent Patent Attorney Masamikatsu Akimoto 1 (2) tQ No. 3 εLEVAT10N (>-) No. 4 No. 5 ((1) Cb) No. q. Time 6 1st O figure 2870 29110 211ri θ 2?ρρ meeting (Saki) Kuzu no l (2) 1st l (17) 740th

Claims (1)

[Claims] 1. Signal intervals of ultrasonic reception signals received in pulses and in time series after receiving ultrasonic waves propagating through a thermal sensor by an ultrasonic receiving means attached to one end of the sensor. The temperature sensor is an ultrasonic thermometer whose temperature is determined by a signal processing means based on the signal processing means, and the temperature sensor itself has non-reflective ends at both ends, and the temperature sensor itself is made of a magnetic material. An ultrasonic thermometer characterized by a configuration in which a plurality of pulse magnetic field generating means are arranged at predetermined intervals and are arranged as electromagnets that generate a pulsed magnetic field different from the magnetic field produced by the means. 2. The ultrasonic thermometer according to claim 1, wherein the temperature top/span is an iron-nickel alloy. 3. The ultrasonic thermometer according to claim 1, wherein the DC magnetic field applying means is a permanent magnet. 4. The ultrasonic thermometer according to claim 1, wherein the DC magnetic field applying means is an electromagnet. 5. The ultrasonic thermometer according to claim 1, wherein the pulsed magnetic field generating means is a wire through which a pulsed current is passed. 6. The ultrasonic thermometer according to claim 4, wherein the electromagnet as the DC magnetic field applying means is a coil through which a constant current is passed.