JPH0121441B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an ultrasonic fluoroscopy device for confirming the presence or absence of obstacles such as fuel assemblies floating above the core of a fast breeder reactor.

[Technical background of the invention]

Background technology will be explained with reference to FIGS. 1 and 2.
Figure 1 shows an ultrasonic fluoroscopy system that uses ultrasonic waves to detect obstacles present in the upper part of the core of a sodium-cooled reactor, such as fuel assemblies floating above the core. - shows a cross-sectional view along the line. Reference numeral 1 in the figure 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 1 is shielded by a shielding plug 5. In addition, a large number of fuel assemblies 6... are loaded into the reactor core 2 so that they can be inserted and removed from above, and heat is generated by the nuclear fission reaction provided inside these fuel assemblies 6. It is configured to heat fluid metallic sodium 4 that flows in from a sodium inlet 7 provided at the bottom of the furnace vessel 1 . 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 it is conceivable that the fuel assemblies 6 float up from the reactor core 2.
In the figure, 6A indicates a fuel assembly floating from the core 2.

On the other hand, the core upper mechanism 3 located above the reactor core 2 is composed of a control rod drive mechanism and various measuring instruments, and during fuel exchange, the core upper mechanism 3 is
The refueling machine must be moved horizontally to a position where it is removed from above the core 2, and a refueling machine (not shown) must be positioned above the core 2 in its place. 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 assemblies 6 loaded into the core 2 from above using the refueling machine reach the lowest position in the core. If it is not fully inserted, or if some of the 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 2 There is a risk that the fuel assembly 6A, which is protruding further upwards, will 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 floating fuel assembly 6A protruding above the core 2. Here, the reactor core 2 is immersed in the liquid metal sodium 4, and in order to examine the state of the fuel assembly submerged in the liquid metal sodium 4, ultrasonic waves with good visibility even in the liquid metal sodium 4 are used. This requires a fluoroscope. 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. In this way, the ultrasonic transducer 9
When more ultrasonic waves are transmitted, liquid metal sodium 4
If there are no obstacles in the core gap, the ultrasonic waves emitted within the core gap will not be significantly attenuated while traveling from the ultrasonic transducer 9 to the ultrasonic reflector 10, and will be reflected by the reflector 10. The received signal is received by the ultrasonic transducer 9, and is outputted from the ultrasonic transducer 9 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 also 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 furnace vessel 1, there are an ultrasonic transducer drive mechanism 11 for rotating the ultrasonic transducer 9, a position detection circuit 12 for detecting the position of the ultrasonic transducer 9 in the rotation direction, and an ultrasonic transducer. A pulser 13 sends an excitation pulse to the ultrasonic transducer 9 in synchronization with the change in position of the ultrasonic transducer 9 in the rotating direction, a receiver 14 detects and amplifies the echo signal, and only allows the echo signal from the ultrasonic reflector to pass through. A gate circuit 15, a timing circuit 16 that outputs a pulse trigger signal to the pulser 13 and a gate time corresponding to the rotation angle of the ultrasonic transducer 9, and detects the peak value of the echo signal that has passed through the gate circuit 15. an image processing circuit 18 that creates a perspective image signal indicating the state of the core gap from the position signal output from the position detection circuit 12 and the peak value of the echo signal output from the peak value detection circuit 17; This image processing circuit 18
An image display device 19 is provided that displays a perspective image based on a perspective image signal from.

Further, the ultrasonic reflecting plate 10 is constructed as shown in FIG. That is, the ultrasonic transducer 9
The ultrasonic beam excited from the beam is emitted 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. The structure is such that reflected waves from each small reflector do not interfere with each other. Here, if the spread angle of the ultrasonic beam (hereinafter referred to as the irradiation angle) is ψ, then a plurality of (seven in this example) small reflectors 10
A, 10B, ... 10G are combined on a staircase to form a unit reflector 10 that achieves the above illumination angle ψ.
such a unit reflector 1
A plurality of 0's are arranged in an arc shape on the inner peripheral surface of the furnace vessel 1. The number of unit reflectors 10 is determined to be enough to cover the area above the reactor core 2 in which the ultrasonic waves are to be viewed, as shown in FIG. As shown in FIG. 3, the center line of the ultrasonic beam emitted from the ultrasonic transducer 9 is centered on the small reflector 10D.
Considering the above state, pulsar 13
From there, each small reflector 10A as shown in FIG.
_Signals corresponding to the reflected _waves from 10B, _. At this time, the maximum echo signal corresponds to the reflected wave from the small reflector 10D on the center line of the ultrasound beam.
It is E _d . Therefore, this maximum echo signal E _d is set as a reference measurement value E _p (E _p =E _d 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. In order to obtain the core gap from the maximum echo signal, for example, the relationship between the echo signal ratio and the core gap ratio as shown in FIG.
This is a configuration that is calculated by In other words, FIG.
The ratio E _p /E _ps between the echo signal E _ps and the reference measurement value E _p when no obstruction exists is taken as the echo signal ratio on the horizontal axis, and the gap between the core 2 and the upper core mechanism 3 is calculated.
The ratio G/G _s of G _s to the core gap G is plotted on the vertical axis as the core gap ratio.

[Problems with background technology]

According to the above configuration, when the temperature of the sodium 4 changes, the sound speed of the ultrasonic wave changes, so it is necessary to correct the gate time of the gate circuit 15 depending on the temperature of the sodium 4. In other words, a reference reflector is installed in a location that is not affected by obstacles, the arrival time of the echo signal from this reference reflector is measured, and the sound speed of the ultrasonic wave at that temperature is calculated from the measured value. Perform time correction. However, according to such a method, high precision is required for the gate circuit 15 and the timing circuit 16, and if there is a temperature distribution in the reactor vessel 1, the There was a risk that the detection of the echo signal would become impossible.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a highly reliable ultrasonic fluoroscope capable of performing highly accurate measurements even when the temperature of liquid metal changes.

[Summary of the invention]

An ultrasonic fluoroscope according to the present invention includes an ultrasonic transducer installed in a nuclear reactor vessel and capable of rotating in a horizontal direction, and a distance between the ultrasonic transducer and the ultrasonic transducer installed opposite to the ultrasonic transducer. an ultrasonic transducer drive mechanism for rotating the ultrasonic transducer; and an ultrasonic transducer for detecting the rotation angle of the ultrasonic transducer. A position detection circuit, a storage circuit that stores echo signals from each small reflector received by the ultrasonic transducer, and signals from the ultrasonic transducer position detection circuit and the storage circuit are input to generate an image. The image processing circuit includes an image processing circuit that creates data, and a display device that displays a fluoroscopic image based on the image signal from the image processing circuit, and the image processing circuit is located at the center of the ultrasound beam from the ultrasound transducer. The echo arrival time from the small reflector that is hit is measured in advance, and an echo signal corresponding to the echo arrival time is detected from the echo signal of each small reflector stored in the storage circuit, and the ultrasonic transducer This method is characterized by detecting the peak value of the echo signal from the reflection plate corresponding to the turning angle of the user.

In other words, in contrast to the conventional method of detecting the echo signal from a small reflector facing the rotation angle of the ultrasonic transducer among multiple small reflectors by setting the gate time using a gate circuit, By detecting the peak value of the echo signal at each rotation angle with respect to the echo arrival time, the echo signal from the small reflector corresponding to the rotation angle of the ultrasonic transducer is detected. Correcting the gate time of the gate circuit based on temperature eliminates the need for additional work and allows stable measurements to be made without being affected by temperature changes in sodium. Furthermore, since a high-precision gate circuit is not used, the configuration is also simplified. Furthermore, it is not affected by temperature distribution in the furnace vessel.

[Embodiments of the invention]

An embodiment of the present invention will be described with reference to FIGS. 6 to 11. Figure 6 shows an ultrasonic fluoroscopy system that uses ultrasonic waves to detect obstacles present in the upper part of the core of a sodium-cooled nuclear reactor, such as fuel assemblies floating above the core. A reactor vessel for a sodium-cooled nuclear reactor that uses metallic sodium.The reactor vessel 101 houses a reactor core 102, an upper core mechanism 103, liquid metallic sodium 104, etc., and the upper part of the reactor vessel 101 is shielded by a shielding plug 105. has been done. In addition, a large number of fuel assemblies 106... are loaded into the reactor core 102 so as to be freely inserted and removed from above, and the nuclear fuel provided inside these fuel assemblies 106... generates heat due to a nuclear fission reaction. The furnace is configured to heat the liquid metal sodium 104 that flows in from the sodium inlet 107 provided at the bottom of the furnace vessel 101. The heated sodium 104 is then flowed out from the sodium outlet 108 provided at the top of the furnace vessel 101, passed through a heat exchanger (not shown), etc. provided outside the furnace vessel 101, and the cooled sodium is returned again. The sodium is allowed to flow in through the sodium inlet 107.

Here, inside the reactor vessel 101, the liquid metal sodium 104 flows through the reactor core 102 from the bottom to the top, so it is conceivable that the fuel assemblies 106... float up from the reactor core 102. In the figure, 106A indicates a fuel assembly floating above the core 102.

On the other hand, the upper core mechanism 103 located above the reactor core 102 is composed of a control rod drive mechanism, various measuring instruments, etc., and is moved horizontally to a position where it is removed from above the core 102 during fuel exchange. , instead, a refueling machine (not shown) must be located above the core 102 . However, the gap between the core 102 and the core upper mechanism 103 (hereinafter referred to as core gap) is 70
Since it is only about mm, a fuel exchanger is used to
Fuel assembly 106 inserted from above into 02...
If the fuel assembly 106 is not fully inserted to the lowest position in the core, or if some of the fuel assemblies 106 are floating as shown in 106A due to the flow of liquid metal sodium 104, the upper core mechanism 1
When 03 is moved horizontally, it collides with the floating fuel assembly 106A that protrudes upward from the core 102,
There is a risk of destroying the fuel assembly.
Therefore, before moving the core upper mechanism,
It is necessary to carefully check whether there is any fuel assembly 106A that protrudes upward from 2.
Here, the reactor core 102 is liquid metal sodium 104
It is submerged inside, and liquid metal sodium 10
In order to examine the state of the fuel assembly submerged in the liquid metal sodium 104, a fluoroscopy device using ultrasonic waves, which has good visibility even in the liquid metal sodium 104, is required. Therefore, a part of the inner circumferential surface of the reactor vessel 101 has a core 10
An ultrasonic transducer 109 is installed at almost the same level as the upper end of the ultrasonic transducer 2, and an ultrasonic reflector plate 110 is installed on the inner peripheral surface of the reactor vessel 101 facing the ultrasonic transducer 109.
Install it. When the ultrasonic transducer 109 emits ultrasonic waves in this manner, the ultrasonic waves emitted in the liquid metal sodium 104 will be transmitted by the ultrasonic transducer 109 unless there are any obstacles in the core gap. Sound wave reflector 1
10, it is not significantly attenuated and is reflected by the reflector plate 110, and the ultrasonic transducer 10
9 and output as an echo signal from the ultrasonic transducer 109. However, if there is some obstacle in the core gap, for example, the core 10.
If there is a fuel assembly or the like floating above 2, the ultrasonic wave will be attenuated when passing through the core gap, so the echo signal will be extremely small. Therefore,
The reflecting plate 110 is widely installed in an arc shape,
By rotating the ultrasonic transducer 109 in the horizontal direction, the presence or absence of obstacles at each position on the reactor core 102 can be investigated. If an obstacle exists somewhere on the reactor core, the presence of the obstacle can be known because no echo signal is obtained when the transducer 109 is directed in that direction and transmits ultrasonic waves. 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 fluoroscope that detects obstacles as described above will be described in more detail. Outside the furnace vessel 101, there are an ultrasonic transducer drive mechanism 111 that rotates the ultrasonic transducer 109, a position detection circuit 112 that detects the position of the ultrasonic transducer 109 in the rotation direction, and an ultrasonic transducer 109. A pulser 113 that sends an excitation pulse to the ultrasonic transducer 109 in synchronization with a change in position in the rotation direction of the ultrasonic transducer 109
A timing circuit 114 that sends a trigger signal to the pulser 113 in synchronization with the position change in the rotation direction of the pulsar 113, a receiver 115 that detects and amplifies the echo signal, a memory circuit 116 that stores the echo signal waveform, and a position detection circuit 112 that detects the echo signal. An image processing circuit 117 that performs image processing based on the detection signal and the echo signal waveform from the storage circuit 116, and a CRT 118 that serves as a display device that displays the created image data.
is provided.

In the above configuration, first, the echo signal waveform for each rotation angle of the ultrasonic transducer 109 is digitized and stored in the storage circuit 116. Based on the data stored in the memory circuit 116, the image processing circuit 117 creates image data for obtaining a display image as shown in FIG. FIG. 7 shows an image displayed in a matrix, with the horizontal axis representing the turning angle of the ultrasonic transducer 109 and the vertical axis representing the arrival time of the echo signal, where each mesh represents a digital value of the echo signal. Furthermore, this image
When displayed on the CRT 118, echo signal levels are displayed in different colors. Next, based on this image data, an echo level signal of the reflection plate 110 corresponding to the rotation angle of the ultrasonic transducer 109 is determined. This will be explained with reference to FIGS. 8 and 9. Figure 8 shows the ultrasonic transducer 109.
FIG. 3 is a diagram showing the relationship between the echo arrival time and the echo signal level corresponding to the turning angle of the vehicle. The echo signals from each of the small reflectors 110A to 110G are Δt
Detected hourly. For example, if the rotation angle of the ultrasonic transducer 109 is θ _o and it faces the reflector n, then the echo arrival time at the sodium temperature is t _o . This echo arrival time t _o is determined by the plurality of small reflectors 1 of the reflector n.
Small reflector 1 located in the center of 10A to 110G
This is the arrival time of the echo signal from 10D, and is measured in advance when starting measurement. In FIG. 8, if the echo signals at each turning angle corresponding to the echo arrival time t _o are taken, the result will be as shown in FIG. 9, with the echo signal E _o having a peak value. Note that FIG. 9 shows the results when the attenuation is 50%. This echo signal E _o is an echo signal from the reflecting plate 110 corresponding to the turning angle θ _o . In other words, even if the echo arrival time changes due to a change in the temperature of the sodium 104, the echo arrival time t _o from the reflecting plate 10 corresponding to each rotation angle at the changed temperature is calculated in advance, and the echo arrival time t _o
By detecting the peak value of the echo level at each turning angle with respect to the turning angle, it is possible to measure the echo signal from the reflecting plate 110 corresponding to that turning angle. Thereafter, in the same manner, the peak value of the echo signal at each echo arrival time t _o is detected, the echo signal from the reflector 110 corresponding to each turning angle is obtained, and data for creating a display image as shown in FIG. 10 is obtained. Create. The display image shown in FIG. 10 shows the echo level at each turning angle, with the horizontal axis representing the turning angle and the vertical axis representing the echo level. Next, the ratio of these measured data and the data in the state without obstacles is calculated (actual measurement data/data in the state without obstacles), and each turning angle is determined from the uplift characteristics in Fig. 5 used to explain the conventional example. Calculate the amount of elevation of the obstacle at . Then, data for obtaining a display image as shown in FIG. 11 is created.
FIG. 11 shows the core 102 and the upper core mechanism 103.
The amount of lift during that time is displayed for each turning angle, and the presence or absence of an obstacle and the amount of lift can be easily recognized.

According to the ultrasonic fluoroscope of this embodiment, first, the echo signal waveform is digitized and stored, and based on this, an image of echo arrival time and echo level with respect to the turning angle is created. Next, a peak value of the echo level is detected for each echo arrival time at each turning angle calculated in advance, and this peak value is used as an echo signal from the reflecting plate 110 for each turning angle. Therefore, even if the temperature of the sodium 104 changes, it can be measured without being affected by it, and since the structure does not use a high-precision gate circuit as in the past, the temperature of the sodium 104 can be measured without being affected by it.
When the gate time is corrected according to the temperature of Furthermore, even if there is a temperature distribution in the reactor vessel 101, echo signals from the reflector plate 110 corresponding to each rotation angle can be reliably detected.

〔Effect of the invention〕

An ultrasonic fluoroscope according to the present invention includes an ultrasonic transducer installed in a nuclear reactor vessel and capable of rotating in a horizontal direction, and a distance between the ultrasonic transducer and the ultrasonic transducer installed opposite to the ultrasonic transducer. a reflector plate made up of a plurality of small reflectors each having a different angle; an ultrasonic transducer drive mechanism for rotating the ultrasonic transducer; and an ultrasonic transducer for detecting the rotation angle of the ultrasonic transducer. A position detection circuit, a storage circuit that stores echo signals from each small reflector received by the ultrasonic transducer, and signals from the ultrasonic transducer position detection circuit and the storage circuit are input to generate an image. The image processing circuit includes an image processing circuit that creates data, and a display device that displays a fluoroscopic image based on the image signal from the image processing circuit, and the image processing circuit is located at the center of the ultrasound beam from the ultrasound transducer. The echo arrival time from the small reflector that is hit is measured in advance, and the echo signal corresponding to the echo arrival time is detected from the echo signal of each small reflector stored in the storage circuit, and the ultrasonic transducer This method is characterized by detecting the peak value of the echo signal from the reflection plate corresponding to the turning angle of the user.

In other words, in contrast to the conventional method of detecting the echo signal from a small reflector facing the rotation angle of the ultrasonic transducer among multiple small reflectors by setting the gate time using a gate circuit, the echo signal is detected by setting the gate time using a gate circuit. By detecting the peak value of the echo signal at each rotation angle with respect to the echo arrival time, the echo signal from the small reflector facing the rotation angle of the ultrasonic transducer is detected. Therefore, the conventional work of correcting the gate time of the gate circuit based on the temperature of sodium is no longer necessary, and stable measurements can be performed without being affected by changes in the temperature of sodium. Furthermore, since a high-precision gate circuit is not used, the configuration is also simplified. Furthermore, even if there is a temperature distribution in the furnace vessel, it is not affected by it, and the effect is great.

[Brief explanation of drawings]

Figures 1 to 5 are diagrams showing conventional examples.
The figure is a schematic diagram of the ultrasonic fluoroscope, and the second figure is the first
Figure 3 is a diagram showing the relationship between the ultrasonic transducer and the reflector, Figure 4 is a timing diagram of the echo signal output from the receiver, and Figure 5 is the relationship between the echo signal and the core gap. It is a figure showing a relationship. 6 to 11 are diagrams showing one embodiment of the present invention, in which FIG. 6 is a schematic configuration diagram of an ultrasound fluoroscope, FIG. 7 is a diagram showing an image displayed on a CRT, and FIG. FIG. 9 is a diagram showing the relationship between the turning angle, the peak value of the echo signal, and the echo arrival time, and FIGS. 10 and 11 are diagrams showing images displayed on the CRT. 109... Ultrasonic transducer, 110...
... Reflection plate, 111 ... Transducer drive mechanism, 112 ... Ultrasonic transducer position detection circuit, 113 ... Pulser, 115 ... Receiver,
116... Memory circuit, 117... Image processing circuit,
118...Display device.

Claims (1)

[Claims] 1. An ultrasonic transducer installed in the reactor vessel and capable of rotating in the horizontal direction, and a plurality of small reflectors provided opposite to the ultrasonic transducer and each having a different distance from the ultrasonic transducer. an ultrasonic transducer drive mechanism for rotating the ultrasonic transducer; and an ultrasonic transducer position detection circuit for detecting the rotation angle of the ultrasonic transducer;
a memory circuit that stores echo signals from each small reflector received by the ultrasonic transducer; and an image that creates image data by inputting signals from the ultrasonic transducer position detection circuit and the memory circuit. The image processing circuit includes a processing circuit and a display device that displays a fluoroscopic image based on the image signal from the image processing circuit, and the image processing circuit includes a small reflector on which the center of the ultrasound beam from the ultrasound transducer hits. The echo arrival time from the ultrasonic transducer is measured in advance, and an echo signal corresponding to the echo arrival time is detected from the echo signals of each small reflector stored in the storage circuit to adjust the turning angle of the ultrasonic transducer. An ultrasonic fluoroscopy device characterized by detecting the peak value of an echo signal from a corresponding reflecting plate.