JPH0634076B2 - Ultrasound fluoroscope - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Industrial field of application) The present invention detects whether or not there is an abnormality in the loading state of a fuel assembly loaded in a reactor vessel of a liquid metal cooled fast reactor. The present invention relates to an ultrasonic see-through device.

(Prior Art) Generally, in a liquid metal cooled fast reactor, a control rod drive mechanism provided in the upper part of the reactor vessel and a control rod inserted in the core are separated before refueling, and then a core upper part mechanism (hereinafter referred to as UCS That is) and the rotating plug that is integral with the unit is rotated to change the fuel. At this time, if the control rod is not separated and inserted into the core securely, or if the core components such as the fuel assembly float up and interfere with UCS, rotating the rotary plug causes the core to rotate. May cause serious damage.
Therefore, in order to avoid such a problem, it is necessary to confirm the presence or absence of an obstacle in the upper part of the core by some means, and if there is an obstacle, return it to a normal position. However, since liquid metal coolants such as sodium are opaque substances, installation of a fluoroscopic device using ultrasonic waves is desired.

As an ultrasonic see-through device, an ultrasonic transmitter / receiver (hereinafter referred to as a transducer) is placed in the vicinity of the upper end of the core to emit ultrasonic waves into the gap between the core and the UCS, and a reflector provided at an opposing position sandwiching the core The signal is processed by receiving the reflected signal of the ultrasonic wave, and this is repeated by scanning the ultrasonic wave in the horizontal direction, and the presence or absence of obstacles is determined from the intensity of the reflected signal. A method of judging the position of each obstacle depending on the time until the reception of the information is considered (Japanese Patent Laid-Open Nos. 55-90808 and 57-154006).
issue).

To determine the horizontal position of an obstacle, for example, it is necessary to have a position resolution that can identify the floating fuel assembly, and the horizontal spread of ultrasonic waves emitted from the transducer is suppressed as much as possible, but the reflector position Since the spread of ultrasonic waves at depends also on the size of the core, it is sometimes difficult to control this to the desired width. Therefore, the reflector is composed of multiple reflective surfaces in the horizontal direction, the reflectors are attached so that the distance from the transducer to each reflective surface is different, and the reflected waves from the multiple reflective surfaces included in the received wave from the reflector are included. A method of judging an obstacle from each of the above has been considered (JP-A-54-62487).

(Problems to be Solved by the Invention) However, a combination of three conditions of an average distance from the transducer determined by the size of the core to the reflector, a difference in distance between the reflecting surfaces, and spread of ultrasonic waves. In some cases, the reflected waves from the plurality of reflecting surfaces included in the received wave are temporally overlapped, and it becomes difficult to distinguish them. Therefore, there is a demand for the development of an ultrasonic fluoroscope capable of determining an obstacle by subjecting a received wave by a transducer to some signal processing to discriminate reflected waves from a plurality of reflecting surfaces.

The present invention has been made to meet such demands,
The purpose is a liquid that can accurately determine the presence and position of obstacles above the core even if the reflected waves from multiple reflecting surfaces included in the received wave of the transducer are temporally overlapped. An object of the present invention is to provide an ultrasonic see-through device for in-core inspection of a metal-cooled fast reactor.

[Means for Solving the Problems] (Means for Solving the Problems) In order to achieve the above-mentioned object, an ultrasonic see-through device of the present invention is provided in the vicinity of the upper end of the core in a reactor vessel of a liquid metal cooled fast reactor A transducer that transmits and receives an ultrasonic signal that crosses above the core, a drive unit that rotatably holds the transducer in a horizontal direction, and an inner cylinder that is arranged with a gap on the inner peripheral side of the reactor vessel. An ultrasonic reflector comprising a plurality of circumferentially-divided divided bodies arranged at a position facing the transducer on the inner surface, and circumferentially separated from the ultrasonic reflector. A reference reflector having a single reflection surface provided at a position, a control unit that controls the drive unit, an ultrasonic wave transmission and reception unit that transmits ultrasonic waves from the transducer and receives a reflected wave from the reflector, Ultrasonic wave transmission A signal processing unit that determines the presence and position of obstacles above the core by receiving the ultrasonic reception signal sent from the receiving unit and the signal indicating the ultrasonic transmission direction sent from the control unit, and an output display that displays the signal processing result. And a signal processing unit for obtaining an impulse response of a system in which the received signal from the reference reflector is an input signal and the ultrasonic reception signal from the divided reflector is an output signal in the signal processing unit as a normalized reflected signal. The reflected waves from the plurality of reflecting surfaces included in the ultrasonic wave reception signal from the divided reflector are discriminated and evaluated.

(Operation) According to the ultrasonic see-through device of the present invention, even when reflected waves from a plurality of reflecting surfaces are superposed and received by the horizontal spread of ultrasonic waves at the reflector mounting position, individual reflection Since the intensity of the reflected waves from the surface can be discriminated and evaluated, the presence and position of obstacles inside the reactor can be accurately determined.

(Example) The Example of this invention is described with reference to drawings.

FIG. 1 is a vertical cross-sectional view of a liquid metal cooling type fast reactor equipped with an ultrasonic see-through device of the present invention, in which a core 1 in which core components are established and a core barrel 2 supporting the core are housed. A reactor vessel 3 is provided. A shield plug 4 is provided above the reactor vessel 3, and a cover gas space is formed between the shield plug 4 and the liquid surface of the liquid metal coolant 5 filled in the reactor vessel 3. An inner cylinder 6 is provided outside the core barrel 2 so as to surround the core barrel 2. An upper core mechanism 7 is provided on the lower surface of the shielding plug 4 with a gap above the core components.

On the other hand, a drive unit 8 for driving the transducer is provided on the shield plug 4, and a transducer 10 is installed in a holding tube 9 which is connected to the drive unit 8 and penetrates the shield plug 4. Inside the inner cylinder 6, a reflector 11 is attached at a position facing the transducer 10.

The ultrasonic reflectors 11 are arranged along the inner circumferential direction of the inner cylinder 6 in the reactor vessel 3 as shown in the cross-sectional view of the reactor vessel in FIG. 5 of 11a to 11e
It is divided into divided bodies. As shown in the enlarged view of FIG. 3, each of the divided bodies 11a to 11e is fixed to the inner cylinder 6 by a mounting seat 12, and each of the divided bodies 11a to 11e is provided with a plurality of (six in the illustrated example) reflecting surface rows 13. Further, a reference reflector 14 having a single reflecting surface is provided at a position distant from the reflector 11 in the circumferential direction.

With respect to the above mechanical components, as shown in FIG. 1, a control unit 15 that controls the drive unit 8 that scans the transducer 10 in a horizontal fan shape, and the transducer 10 in the horizontal direction by a preset angle. An ultrasonic wave transmission / reception unit 16 is provided for transmitting an ultrasonic wave from the transducer 10 and receiving a reflected wave from the reflector 11 in response to a signal indicating that it has stopped at the rotationally moved position. Further, the signal processing unit 17 for determining the presence and position of an obstacle by receiving the ultrasonic reception signal sent from the ultrasonic transmission reception unit 16 and the ultrasonic transmission angular position signal sent from the control unit 15 and the signal processing result are displayed. Output display section
18 are provided.

Next, the processing procedure in the signal processing unit 17 of the present invention will be described below.

FIGS. 4 (a) and 4 (b) schematically show examples of received waves obtained when ultrasonic waves are emitted to the reflecting surface array 13 composed of four reflecting surfaces 13a to 13d. Reflected wave from the surface S ₁ ~
S ₄ is synthesized, and the strength of S ₂ is 0.8 times that of S _1
3 is 0.8 times S ₂ , and S ₄ is 0.8 times S ₃ . Now, if the received wave actually obtained is always as shown in FIG. 4 (a), it is easy to discriminate the reflected waves S _{1 to} S ₄ from each reflecting surface and evaluate the intensity, but the ultrasonic wave Depending on the difference between the wavelength of and the distance of each reflecting surface, S ₁ to S as shown in Fig. 4 (b)
₄ is received in a superimposed manner, which makes it difficult to discriminate and evaluate this. In order to make it possible to determine an obstacle even in such a case, the signal processing unit 17 of the present invention performs the processing according to the processing procedure shown in FIG. That is, in order to eliminate the influence of the fluctuation of the liquid metal coolant temperature on the propagation speed of ultrasonic waves, the reflected waves obtained by emitting ultrasonic waves at one angle position, for example, 10 times or more are added, and then the average reflected wave is first calculated. Calculate z (t) (Process 10
1). Next, the Fourier transform of the average reflected wave z (t) is performed,
The Fourier coefficient z (jω) is calculated (process 102). Further, the reflected wave y from the single reflecting surface obtained by emitting ultrasonic waves to the reference reflector 14 in advance by the same procedure as above.
The Fourier coefficient Y (jω) of (t) is calculated and held (process 103), and using this Y (jω), y (t) is a virtual input and z (t) is an output of the system. Frequency response H
(Jω) is obtained by calculating H (jω) = Z (jω) / Y (jω) (process 104). Next, the impulse response h (t) is obtained by inverse Fourier transforming H (jω).
Is calculated (process 105).

When the reflected wave y (t) from the reference reflector is as shown in FIG. 4 (c) (the same waveform as S _{1 in} this example), FIG. 4 (a) and FIG. ) And (e), the impulse response h (t) is obtained. As can be seen from these figures, the impulse response h (t) corresponds to the reflected wave from the reflecting surface array 13 standardized with the reflected wave from the reference reflector 14, and the reflected wave from each reflecting surface. The intensity of is also calculated quantitatively and correctly (process 106). The reflected wave intensity thus obtained, the reflected wave intensity when all the internal structures are correctly set, and the gap amount at this time are used to calculate the gap amount at the time of measurement by proportional calculation. The gap amount corresponding to the angular position is displayed on the output display unit 18 (process 107), whereby the presence and position of the obstacle can be easily recognized.

〔The invention's effect〕

As described above, according to the present invention, even when reflected waves from a plurality of reflecting surfaces are superposed and received due to the horizontal spread of ultrasonic waves at the reflector mounting position, even if the reflected waves are received from the individual reflecting surfaces. Since the intensity of the reflected wave can be discriminated and the intensity thereof can be evaluated, it is possible to accurately determine the presence and position of the obstacle. Therefore, it is expected that sufficient positional resolution can be obtained by increasing the number of reflecting surfaces even when the core becomes large. Further, the horizontal spread of ultrasonic waves and the restriction on the wavelength are alleviated, and it is expected that the manufacturing cost of the transducer and the ultrasonic transmitter will be reduced. In addition, since the restriction on the difference in the distance from each transducer on each reflecting surface is alleviated when mounting the reflecting surface array of reflecting bodies, it is expected to reduce the reflector space.

[Brief description of drawings]

1 is a longitudinal sectional view of a liquid metal cooled fast reactor equipped with the ultrasonic see-through device of the present invention, FIG. 2 is a lateral sectional view of the reactor vessel of FIG. 1, and FIG. 3 is a reflection of FIG. Fig. 4 (a) and (b) are enlarged views of the surface row part. Schematic waveform diagram of the received wave when ultrasonic waves are emitted to the reflection surface row having four reflection surfaces, Fig. 4 (c).
Is the basic waveform diagram of the received wave from the reference reflector, (d) and (e) are the impulse response waveform diagrams of (a) and (b) respectively, and FIG. 5 is the signal processing unit of the present invention. 5 is a flowchart showing a processing procedure in. 1 ... Reactor core, 2 ... Reactor barrel, 3 ... Reactor vessel, 4 ... Shielding plug, 5 ... Liquid metal coolant, 6 ... Inner cylinder, 7 ... Core upper mechanism, 8 ... Drive section, 9 ... Holding tube, 10 …… Transducer 11 …… Reflector, 12 …… Mounting seat 13 …… Reflecting surface array, 14 …… Reference reflector 15 …… Control section, 16 …… Ultrasonic wave transmitting / receiving section 17 …… Signal processing Section, 18 ... Output display section

Claims (1)

[Claims] 1. An ultrasonic transmitter / receiver for transmitting / receiving an ultrasonic signal that traverses above the core from a position in the vicinity of the upper end of the core in a reactor vessel of a liquid metal cooled fast reactor, and the ultrasonic transmitter / receiver. Is rotatably held in a horizontal direction, and a plurality of drive units are disposed at a position facing the ultrasonic transmitter / receiver on the inner surface of the inner cylinder positioned with a gap on the inner peripheral side of the reactor vessel. Reference reflection having an array of reflecting surfaces and consisting of a plurality of divided bodies divided in the circumferential direction, and a single reflecting surface provided at a position distant from the ultrasonic reflector in the circumferential direction. A body, a control unit that controls the drive unit, an ultrasonic wave transmission / reception unit that transmits ultrasonic waves from the ultrasonic wave transmission / reception unit and receives a reflected wave from a reflector, and an ultrasonic wave transmission / reception unit. The ultrasonic wave reception signal and the signal indicating the ultrasonic wave transmission direction sent from the control unit A signal processing unit that determines the presence and position of obstacles above the core, and an output display unit that displays the signal processing result, wherein the signal processing unit receives the received signal from the reference reflector as an input signal, and By obtaining the impulse response of the system with the ultrasonic reception signal from the split reflector as the output signal as a normalized reflection signal, the reflected waves from the plurality of reflection surfaces included in the ultrasonic reception signal from the split reflector An ultrasonic see-through device characterized by discriminating and evaluating.