JPH0366602B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an ultrasonic fluoroscope suitable for detecting obstacles and the like existing in the upper part of the core of a sodium-cooled nuclear reactor.

[Technical background of the invention]

Background technology will be explained with reference to FIGS. 1 and 2.

Fig. 1 shows an ultrasonic fluoroscopy system that uses ultrasonic waves to detect obstacles existing above the core of a sodium-cooled reactor, such as fuel assemblies floating above the core, and Fig. 2 shows the - A cross-sectional view along a line is shown. In the figure, 1 is a reactor vessel of a sodium-cooled nuclear reactor that uses liquid metal sodium as a coolant. Inside this reactor vessel 1, a reactor core 2, a core upper mechanism 3, a liquid metal sodium 4, etc. are housed.
The upper part of the furnace vessel 1 is shielded by a shielding plug 5. In addition, a large number (more than 400) of fuel assemblies 6... are loaded into the reactor core 2 so that they can be inserted and removed from above, and the nuclear fuel provided inside these fuel assemblies 6... undergoes a nuclear fission reaction. Generates heat and uses this heat to open the sodium inlet 7 provided at the bottom of the furnace vessel 1.
It is configured to heat the liquid metal sodium 4 that has flowed in. The heated sodium 4 is then flowed out from the sodium outlet 8 provided at the top of the furnace vessel 1, passed through a heat exchanger (not shown), etc. provided outside the furnace vessel 1, and the cooled sodium is returned to the boiling point. The sodium is allowed to flow in through the sodium inlet 7.

Here, inside the reactor vessel 1, the liquid metal sodium 4 flows through the reactor core 2 from the bottom to the top, so that the fuel assemblies 6 are likely to float up from the reactor core 2.
In the figure, 6A indicates a fuel assembly floating above the core 2.

On the other hand, the upper core mechanism 3 located above the reactor core 2 is composed of a control rod drive mechanism, various measuring instruments, etc., and when replacing fuel, the upper core mechanism 3 is horizontally moved to a position where it is removed from above the core 2. , instead, a refueling machine (not shown) must be located above the core 2. However, since the gap between the core 2 and the upper core mechanism 3 (hereinafter referred to as the core gap) is only about 70 mm, the fuel assembly 6 inserted into the core 2 from above using the refueling machine is at the lowest position in the core. If it is not fully inserted, or if some fuel assemblies 6 are floating as shown in 6A due to the flow of liquid metal sodium 4, if the core upper mechanism 3 is moved horizontally, the core will be removed. There is a risk that the fuel assembly 6A that protrudes upward from the fuel assembly 2 may collide with the fuel assembly 6A and destroy that fuel assembly. Therefore, before moving the core upper mechanism, it is necessary to carefully check whether there is any fuel assembly 6A protruding above the core 2. Here, the core 2 is liquid metal sodium 4
In order to examine the state of the fuel assembly submerged in the liquid metal sodium 4, a fluoroscopic device using ultrasonic waves with good visibility even in the liquid metal sodium 4 is required. Therefore, an ultrasonic transducer 9 is installed on a part of the inner circumferential surface of the reactor vessel 1 at a position approximately at the same level as the upper end of the reactor core 2, and an ultrasonic reflector is mounted on the inner circumferential surface of the reactor vessel 1 opposite to the ultrasonic transducer 9. Attach 10. When the ultrasonic transducer 9 emits ultrasonic waves in this way, the ultrasonic waves emitted in the liquid metal sodium 4 will be transmitted by the ultrasonic transducer 9 if there are no obstacles in the core gap. The sound waves are not significantly attenuated while reaching the sound wave reflection plate 10,
Ultrasonic transducer 9 reflected by reflection plate 10
The echo signal is received by the ultrasonic transducer 9 and output as an echo signal. However, if there is any obstacle in the core gap, such as a fuel assembly floating above the core 2, the ultrasonic waves will be attenuated when passing through the core gap, and the echo signal will become extremely small. Therefore, by installing the reflecting plate 10 in a wide arc shape and rotating the ultrasonic transducer 9 in the horizontal direction, it is possible to check the presence or absence of obstacles at each position on the reactor core. If an obstacle exists somewhere on the reactor core, the existence of the obstacle can be known because no echo signal is obtained when the transducer 9 is directed in that direction and ultrasonic waves are emitted. Furthermore, the direction in which the obstacle exists can be determined from the position of the transducer in the turning direction at that time.

The ultrasonic fluoroscopy apparatus that detects the obstacles as described above will be described in more detail as follows.
That is, outside the reactor vessel 1 are a drive mechanism 11 for rotating the ultrasonic transducer 9, a position detection circuit 12 for detecting the rotation angle of the ultrasonic transducer 9, and a position change in the rotation direction of the ultrasonic transducer 9. a pulser 13 that sends an excitation pulse to the ultrasonic transducer 9 in synchronization with the ultrasonic transducer 9; a receiver 14 that detects and amplifies the echo signal; a gate circuit 15 that allows only the echo signal from the ultrasonic reflector to pass; Based on the output of the circuit 12, an excitation pulse is sent to the pulser 13 to excite the ultrasonic transducer 9, and a gate time is set according to the rotation angle of the ultrasonic transducer 9, and a trigger signal is sent to the gate circuit 15. a timing circuit 16 that sends out a peak value of the echo signal that has passed through the gate circuit 15; a peak detection circuit 17 that detects the peak value of the echo signal that has passed through the gate circuit 15; and a peak detection circuit 17 that detects the peak value of the echo signal that has passed the gate circuit 15; An image processing circuit 18 that creates an image signal indicating the state of the core gap from the value, and an image display 19 that displays a perspective image based on the image signal from the image processing circuit 18 are provided.

Further, the ultrasonic reflecting plate 10 is constructed as shown in FIG. That is, the ultrasonic transducer 9
The more excited ultrasonic beam is irradiated with a two-dimensional spread. For this reason, the reflector 10 is a combination of small reflectors subdivided in the circumferential direction, and a step Δl is provided between adjacent small reflectors so that the distance from the ultrasonic transducer 9 changes stepwise. It is arranged so that the reflected waves from each small reflecting plate do not interfere with each other. Here, if the spread angle of the ultrasonic beam (hereinafter referred to as the irradiation angle) is, a plurality of (seven in this example) small reflector plates 1
0A, 10B, ..., 10G are combined in a stepwise manner to cover the above reflection angle, and a plurality of such unit reflectors 10 are installed in the reactor vessel 1. They are arranged in an arc shape on the inner peripheral surface. The number of unit reflectors 10 is determined to be enough to cover the area above the reactor core 2 where ultrasonic waves should be seen through, as shown in FIG. Now, as shown in FIG. 3, if we consider a state in which the center line of the ultrasonic beam emitted from the ultrasonic transducer 9 is on the central small reflector 10D, the pulsar 14 will transmit the ultrasonic beam to each small reflector 10A. ,10B,...
. . , 10G is output, and is further amplified by the receiver 14 to become echo signals Ea, Eb, . . . , Eg as shown in FIG.
At this time, the maximum echo signal is the echo signal Ed corresponding to the reflected wave from the small reflection plate 10D located on the center line of the ultrasonic beam. Therefore, this maximum echo signal Ed is set as a reference measurement value Ep (Ep=Ed in this case), and the size of the core gap is determined from this reference measurement value and displayed on the image display device 19. Note that in order to determine the core gap from the maximum echo signal, the relationship between the echo signal ratio and the core gap ratio, as shown in FIG. .
In other words, Fig. 5 shows the ratio Ep/Ep of the echo signal Ep s and the reference measurement value Ep when no obstacle exists.
s is taken as the echo signal ratio on the horizontal axis, and the ratio G/Gs between the gap Gs between the core 2 and the core upper mechanism 3 and the core gap G is taken as the core gap ratio on the vertical axis.

[Problems with background technology]

In the conventional ultrasonic fluoroscope as described above, when the temperature of the sodium 4 in the reactor vessel 1 changes, the propagation speed of the ultrasonic wave changes, so the gate time of the gate circuit 15 is corrected according to the speed change. The need arose. Therefore, in conventional equipment, a reference reflector is installed at a position where it will not be affected even if there is an obstacle above the reactor core, and the arrival time of the echo signal obtained by reflecting the ultrasonic wave from the reference reflector is The propagation speed of the ultrasonic wave was determined and the gate time was corrected based on that speed.

Therefore, the timing circuit 16 and the gate circuit 1
5, extremely high precision was required. Furthermore, if the sodium temperature inside the reactor vessel 1 differs depending on the location, the above correction will not be performed effectively, and the echo signal from the reflector corresponding to the rotation angle of the ultrasonic transducer 9 will not be detected. There was also the problem of not being able to do so.

[Purpose of the invention]

The present invention was developed based on these circumstances, and its purpose is to maintain the rotation angle of the ultrasonic transducer even when the sodium temperature inside the reactor vessel fluctuates or when the sodium temperature differs from place to place. An object of the present invention is to provide an ultrasonic fluoroscopy device that can reliably detect a corresponding echo signal and does not require highly accurate timing circuits or gate circuits. The fluoroscopic device includes an ultrasonic transducer that is rotatably provided, and a plurality of small reflecting plates that face the ultrasonic transducer and change the distance from the ultrasonic transducer in steps. a position detection circuit for detecting the rotation angle of the ultrasonic transducer of a plurality of ultrasonic reflectors arranged along the rotation direction of the ultrasonic transducer; and a pulser for exciting the ultrasonic transducer. a timing circuit that sends an excitation pulse to the pulser based on the output of the position detection circuit and sets a gate time corresponding to the rotation angle of the ultrasonic transducer; a gate circuit that passes an echo signal from the reflection plate received by the sonic transducer; a peak detection circuit that detects the peak value of the echo signal that has passed through the gate circuit; and an echo signal that has passed through the gate circuit. an echo signal selection circuit that selects an echo signal corresponding to the turning angle of the transducer from the echo signals, and a fluoroscopic image based on the peak value of the echo signal selected by this selection circuit. The present invention is characterized by comprising an image display device that creates signals and displays images.

With this configuration, the rotation angle of the ultrasonic transducer and each small reflector of the reflector can be easily correlated, and the sodium temperature in the reactor pressure vessel fluctuates or the sodium temperature changes. Even if the echo signal differs from place to place, it is possible to reliably detect the echo signal corresponding to the turning angle of the ultrasonic transducer. Furthermore, since the gate time of the gate circuit can be set widely in consideration of the fluctuation range of the sodium temperature, there is no need to make the timing circuit and the gate circuit highly accurate.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described with reference to the drawings from FIG. 6 onwards.

FIG. 6 shows an ultrasonic fluoroscopy system that uses ultrasonic waves to detect obstacles existing above the core of a sodium-cooled nuclear reactor, such as fuel assemblies floating above the core. In the figure, 101 is a reactor vessel of a sodium-cooled nuclear reactor that uses liquid metal sodium as a coolant.
2. Core upper mechanism 103, liquid metal sodium 1
04 etc. are accommodated, and the upper part of the furnace vessel 101 is shielded by a shielding plug 105. In addition, a large number of fuel assemblies 106 are loaded into the core 102 so as to be able to be inserted and removed from above, and these fuel polymer assemblies 106...
The nuclear fuel provided inside 6... generates heat through a nuclear fission reaction, and this heat is configured to heat the liquid metal sodium 104 that flows in from the sodium inlet 107 provided at the bottom of the reactor vessel 101. . And this heated sodium 1
04 flows out from the sodium outlet 108 provided at the top of the furnace vessel 101, passes through a heat exchanger (not shown), etc. provided outside the furnace vessel 101, and cooled sodium flows in again from the sodium inlet 107. That's what I do.

In addition, an ultrasonic transducer 109 is installed on a part of the inner peripheral surface of the reactor vessel 101 at a position approximately at the same level as the upper end of the reactor core 102. Board 110
is installed.

On the other hand, the following equipment is provided outside the furnace vessel 101. First, reference numeral 111 in the figure is a drive mechanism installed on the shielding plug 105, which rotates the ultrasonic transducer 109 in the horizontal direction via a rotating shaft 111A that is vertically suspended within the reactor vessel 101. . 112 in the figure is a position detection circuit, which detects the ultrasonic transducer 10 by inputting a signal from the drive mechanism 111.
This detects the rotation angle of 9. Also, 1 in the figure
A pulser 13 sends an excitation pulse to the ultrasonic transducer 109. In the figure, 114 is a receiver that detects and amplifies the echo signal output from the ultrasonic transducer 109. In the figure, 115 is a gate circuit, which allows only the echo signal output from the receiver 114 to pass through for a certain period of time (gate time). In the figure, reference numeral 116 is a timing circuit, which sends an excitation pulse to the pulser 113 based on the output of the position detection circuit 112 to excite the ultrasonic transducer 109. The gate time is set according to the turning angle, and the gate circuit 1
15 to open the gate circuit 115 for a certain period of time (gate time). In the figure, 117 is a peak detection circuit, which detects the peak value of the echo signal that has passed through the gate circuit 115. In addition, 118 in the figure is a counter;
This is to compare the signal passing through the gate circuit 115 with a predetermined threshold level, receive the signal exceeding the threshold level as an echo signal, and measure the echo time. Reference numeral 119 in the figure is an echo signal selection circuit, which has a memory circuit for storing the peak value of the echo signal and its echo time, and the turning angle of the ultrasonic transducer 109 at which the peak value is maximum for each echo time. This is what we seek. Further, 120 in the figure is an image processing device. This is composed of an image processing circuit 121 and an image display 122, and the position detection circuit 1
The position signal from 12 and the peak value of the echo signal selected by the selection circuit 119 are input to the image processing circuit 121 to create a fluoroscopic image signal, and based on the fluoroscopic image signal, the core 102 and the upper core mechanism 103 are A perspective image of the core gap existing between the two is displayed on the image display 122.

Further, the ultrasonic reflecting plate 110 is as shown in FIG.
A plurality of (seven in this example) small reflecting plates 110A, 110B, . . . are subdivided in the circumferential direction of the furnace vessel 101.
..., 110G are combined, and a constant step Δl is provided in the radial direction of the reactor vessel 101 so that the distance from the ultrasonic transducer 109 changes stepwise between adjacent small reflectors. 110A,
The configuration is such that the reflected waves from 110B, . . . , 110G do not interfere with each other. And these small reflecting plates 110A, 110B, ..., 110G
The spread angle (irradiation angle) of the ultrasonic beam is covered by one ultrasonic reflector 110 composed of a plurality of ultrasonic transducers. Yusa 109
They are arranged along the rotation direction (that is, the circumferential direction of the reactor vessel 101) to cover the range above the reactor core 102 that should be ultrasonic-diagnosed.

Next, the operation of the ultrasonic fluoroscope configured as described above will be explained.

First, it is assumed that the ultrasonic transducer 109 is driven by the drive mechanism 111 and placed in the position shown in FIG. 7, that is, in a position where the center line of the ultrasonic beam coincides with the central small reflecting plate 110D. Here, the position detection circuit 112 receives a signal from the drive mechanism 111 and sends a position signal to the echo signal selection circuit 119. The memory circuit of the echo signal selection circuit 119 stores the relationship between the rotation angle of the ultrasonic transducer 109, that is, the output of the position detection circuit 112, and the echo peak values from each of the small reflectors 110A, 110B, . . . , 110G. remembered. Figure 8 shows the fuel assembly 106 floating above the core 106.
For the case where A is interposed between the small reflection plates 110C to 110E and the ultrasonic transducer 109, the rotation angle (θ ₁ , θ ₂ , ..., θ ₇ ) of the ultrasonic transducer 109, Each small reflector 110A~
The peak values of echo signals Ea to Eg from 110G,
It is a graph three-dimensionally showing the relationship with echo time. In addition, in Fig. 8, the turning angles θ ₁ , θ ₂ , ..., θ ₇
are each small reflecting plate 110A, 110B, ..., 11
It is compatible with 0G, and the echo time is t _o+1
−t _o =t _o −t _o-1 =……=Δt is each echo signal Ea~
This corresponds to the time interval of Eg. Therefore, there is an obstacle (floating fuel rod 106A) between the small reflector 110D and the ultrasonic transducer 109.
exists, the echo signal Ed corresponding to the turning angle θ ₄ of the ultrasonic transducer 109 at that time does not necessarily have the maximum peak value, but the echo time t _{o -1} → t _o → When the value is changed to t _{o +1} , there is an echo time (echo time t in FIG. 9) at which the echo signal Ed reaches its maximum peak value (see FIG. 10). Therefore, echo signal selection circuit 1
At step 19, this peak value is detected and output to the image processing circuit 121.

In the image processing circuit 121, the echo signal selection circuit 1
The position signal from the position detection circuit 112 is input via the echo signal selection circuit 119.
The selected echo peak value is input to create an image signal. Furthermore, the image display 122 uses the ultrasonic transducer 10 based on this image signal.
A perspective image between the ultrasonic reflector 9 and the ultrasonic reflector 110 is displayed.

Therefore, when an obstacle exists between the ultrasonic transducer 109 and the ultrasonic reflector 110 as shown in FIG. 8, and the core gap is narrowed, when the ultrasonic wave passes through the core gap, The echo signal becomes extremely small. The state of the core gap is displayed on the image display 122, and the presence and position of the obstacle can be immediately known. Also, the reactor vessel 10
Even if the sodium temperature within the ultrasonic transducer 109 fluctuates or differs depending on the location, an echo signal corresponding to the rotation angle of the ultrasonic transducer 109 is selected from the echo time measured by the counter 118, Since the fluoroscopic image signal is created based on the echo peak value at that time, the echo signal corresponding to the rotation angle of the ultrasonic transducer 109 can be reliably detected. Then, the gate time of the gate circuit 115 is greatly increased, and the echo peak value and echo time of the echo signal passing through the gate circuit 115 are measured.The echo signal selection circuit 119 calculates the relationship between the echo time and the echo peak value for each turning angle. Therefore, the timing circuit 116 and gate circuit 115 are not required to be highly accurate.

〔Effect of the invention〕

As described above based on the embodiments, the ultrasonic fluoroscope according to the present invention includes an ultrasonic transducer that is rotatably provided, and an ultrasonic transducer that faces the ultrasonic transducer. A plurality of ultrasonic reflectors arranged along the rotation direction of the ultrasonic transducer, each having a plurality of small reflectors that change the distance of the ultrasonic transducer in steps, and detecting the rotation angle of the ultrasonic transducer. a position detection circuit that excites the ultrasonic transducer, a pulser that sends an excitation pulse to the pulser based on the output of the position detection circuit, and a gate time that corresponds to the rotation angle of the ultrasonic transducer. A timing circuit to be set, a gate circuit that receives a trigger signal from this timing circuit and passes an echo signal from the reflection plate received by the ultrasonic transducer, and a peak of the echo signal that has passed through this gate circuit. a peak detection circuit for detecting the value; a counter for measuring the echo time that has passed through the gate circuit; and an echo signal selection circuit for selecting an echo signal corresponding to the rotation angle of the ultrasonic transducer from the echo time; The present invention is characterized by comprising an image display device that creates a fluoroscopic image signal based on the peak value of the echo signal selected by the selection circuit and displays the image. Even when the sodium temperature fluctuates or differs depending on the location, the echo signal corresponding to the rotation angle of the ultrasonic transducer can be reliably detected, making it possible to use highly accurate timing circuits and gate circuits. You can get excellent results without having to do anything.

[Brief explanation of drawings]

Figures 1 to 5 show the background technology.
Figure 1 is a schematic configuration diagram of an ultrasonic fluoroscopy system applied to detect obstacles in the upper part of the core.
3 is a schematic configuration diagram showing the relationship between the ultrasonic transducer and the ultrasonic reflector, FIG. 4 is a timing diagram of the echo signal output from the receiver, and FIG. The figures are diagrams showing the relationship between the echo signal and the core gap, Figures 6 to 1.
Figure 0 shows one embodiment of the present invention, Figure 6 is a schematic configuration diagram of an ultrasonic fluoroscope applied to detect obstacles in the upper part of the reactor core, and Figure 7 shows an ultrasonic transducer and an ultrasonic transducer. A schematic configuration diagram showing the relationship with the reflector, Figure 8 is an explanatory diagram for the case where a small obstacle exists in the core gap, and Figure 9 is a three-dimensional diagram showing the relationship between the turning angle, echo peak value, and echo time. Figure 10 shows the echo time t _o of Figure 9.
FIG. 3 is a diagram showing the distribution of echo peak values in FIG. 109... Ultrasonic transducer, 110...
...Ultrasonic reflector, 111... Drive mechanism, 112...
...Position detection circuit, 113...Ultrasonic generator, 11
4...Amplifier, 115...Gate circuit, 116...
...Timing circuit, 117...Peak detection circuit,
118... Counter, 119... Echo signal selection circuit, 120... Image display device.

Claims (1)

[Claims] 1. An ultrasonic transducer that is rotatably provided, and a plurality of small reflecting plates that face the ultrasonic transducer and change the distance from the ultrasonic transducer in stages. a plurality of ultrasonic reflectors arranged along a rotation direction of the ultrasonic transducer; a position detection circuit for detecting a rotation angle of the ultrasonic transducer; and a position detection circuit for exciting the ultrasonic transducer. a timing circuit that sends an excitation pulse to the pulser based on the output of the position detection circuit and sets a gate time corresponding to the rotation angle of the ultrasonic transducer, and a trigger signal from the timing circuit. a gate circuit for passing the echo signal from the reflection plate received by the ultrasonic transducer; a peak detection circuit for detecting the peak value of the echo signal that has passed through the gate circuit; an echo signal selection circuit that selects an echo signal corresponding to the rotation angle of the ultrasonic transducer from the echo signals; and a peak value of the echo signal selected by the selection circuit. 1. An ultrasonic fluoroscope, comprising: an image display device that generates a fluoroscopic image signal based on the fluoroscopic image signal and displays the image. 2. The echo signal selection circuit has a memory circuit that stores the peak value of the echo signal and its echo time, and determines the maximum peak value for each echo time. Ultrasonic fluoroscope.