JPS60185106A - Ultrasonic wave fluoroscopic apparatus in atomic reactor - Google Patents

Abstract

PURPOSE:To obtain the picture of the image of the upper end surface of a reactor core at high resolution, by scanning the upper end surface of a fuel assembly, in which many isotropic scattering bodies are arranged, by the fan beam of an ultrasonic wave transducer, thereby receiving the beam positively. CONSTITUTION:An upper mechanism 3 is moved when fuel is replaced. A fan beam is projected on the upper end surface of a fuel assembly 21 in a reactor core 2A from an ultrasonic wave transducer 7A, which is moved in a horizontal plane. The scattered reflected light is received again. A measurement controlling circuit 9A, which controls the timing of transmission and reception, processes the distance direction and the azimuth direction, with the length of synthesized aperture being a processing unit. The image of the upper end surface of the reactor core 2A is made to be a picture. On the upper end surface of a handling head part 22 at the top of the fuel assembly 21, many semispherical convex isotropic bodies 23 having the size that is about the same as or larger than that of the ultrasonic wavelength are arranged. Therefore, the ultrasonic wave beam is scattered in an isotropic pattern. The beam is positively received, and the image of the upper end surface of the reactor core can be made to be a picture at high resolution.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] This invention relates to deformation such as subsidence of the core structure in a nuclear reactor, arrangement of fuel assemblies, presence or absence of defects, identification of fuel assemblies at the time of fuel replacement, etc. The present invention relates to an ultrasonic reactor internal fluoroscopy device as a nuclear reactor internal monitoring device.

[Prior art]

2. Description of the Related Art Conventionally, there has been a device shown in FIG. 1 as this type of ultrasonic nuclear reactor internal fluoroscopy device. In the figure, / is the reactor vessel, C is the reactor core consisting of a large number of fuel assemblies (not shown), 3 is the core upper mechanism, G is the rotating plug, S is the reactor lid, and 6 is the liquid that is the reactor coolant. 7 is the ultrasonic transducer; 1 is the driving mechanism of the ultrasonic transducer;
9 is a measurement control circuit.

Next, the operation will be explained. The conventional ultrasonic reactor interior monitoring device shown in Figure 1 is used as a reactor interior monitoring device to detect deformations such as subsidence of the reactor core structure, the arrangement of combustion assemblies, the presence or absence of defects, and the fuel consumption during refueling. It is used to identify vehicles and when changing fuel during periodic inspections of nuclear reactors.

Therefore, in a state where the upper core mechanism 3 is moved from above the reactor core 2 by eccentrically rotating the rotary plug tray for fuel exchange, the ultrasonic reactor internal fluoroscopy device monitors the condition of the upper part of the reactor core 2. After the upper core mechanism 3 is moved from above the core, the ultrasonic transducer 7 is held in a horizontal position above the core by the membrane arm of the drive mechanism g according to the control signal from the measurement control circuit. By doing so, the ultrasonic beam transmitting surface (receiving surface) of the ultrasonic transducer 7 faces the upper end surface pressure of the reactor core. The ultrasonic beam transmitted from the ultrasonic transducer 7 to the top surface of the core is called a pencil beam (spatially narrow beam) and 1z
L, the emitted ultrasonic beam is reflected at the top of the fuel assembly constituting the reactor core, and the reflected wave is received by the ultrasonic transducer 7. By measuring the time from transmission to reception of the received ultrasonic beam, it is possible to know the distance between the ultrasonic transducer 7 and the part of the fuel assembly in the core that is irradiated with the ultrasonic beam. Furthermore, the position (coordinates) of the irradiated portion of the fuel assembly can be known from the position (coordinates) of the ultrasonic transducer 7. Therefore, the ultrasonic transducer 7 is scanned in a horizontal plane above the core, and the ultrasonic beam is emitted.
By repeating reception, the situation at the upper end of the core can be mapped three-dimensionally. This method is basically exactly the same as the ultrasonic B-scan (or C-scan) method used in medical or non-destructive testing. Therefore, the resolution when imaging the upper end face of the core λ in the above method is determined by the pulse time width of the ultrasonic beam and the spread of the ultrasonic beam. This will be explained using FIG. 2. T is the pulse time width of the ultrasonic beam emitted from the ultrasonic transducer 7, θ in Fig. 2 is the spread angle of the ultrasonic beam, and R in Fig. 2 is the ultrasonic transducer 7. The distance from the upper end surface of the core unit to the part irradiated with the ultrasonic beam, t is the time from transmission to reception of the ultrasonic beam, D is the aperture length of the ultrasonic transducer 7, and C is the liquid that is the propagation medium. Speed of sound in sodium 6, e
If is the carrier frequency of the ultrasonic beam and λ is the wavelength of the ultrasonic wave in liquid sodium 6, then the distance between the ultrasonic transducer 7 and the reflected part of the ultrasonic beam in the core λ is Since the ultrasonic beam propagates, its distance one resolution aR is given by δR=-CT (-0l) Further, the resolution δX in the in-plane direction of the core is determined by the spread of the ultrasonic beam as described above. On the other hand, since the ultrasonic beam spread angle θ is given by the following equation, the resolution δX in the in-plane direction is λ δX−=R·− and 1. From this, the resolution when imaging to monitor the upper part of the core is determined by the shorter the pulse width of the ultrasonic beam and the higher the carrier frequency of the ultrasonic beam. It can be seen that the wider the opening of the circ, the better the performance. That is, horizontal scanning and transmission and reception of ultrasonic beams in the above device are carried out by sequentially repeating scanning 1 transmission and reception over the entire area of the upper end surface of the core 2 above the core at every in-plane direction resolution δX. Image the upper situation.

Since conventional ultrasonic nuclear reactor fluoroscopy systems are constructed based on the above-mentioned principle, it is extremely difficult to obtain high-resolution images for the following reasons. In other words, when trying to shorten the pulse width of an ultrasound beam in order to improve distance resolution, the transmission power is relatively reduced, which requires a short-time high-power transmitter. Ultrasonic transducers and transmitters must be used that do not suffer from the distortions associated with the high power transmission of the outgoing ultrasound beam, or the carrier frequency may be increased to improve in-core resolution. (If you try to do this, the attenuation of the ultrasonic beam in the liquid sodium 6 will be large, resulting in a decrease in the reception efficiency of the reflected ultrasonic beam from the upper end of the core. Also, the aperture of the ultrasonic transducer 7 Even if an attempt is made to improve the resolution in the in-plane direction of the reactor core by increasing the size, the size of the ultrasonic transducer and its driving mechanism g will increase, so other mechanical parts as an ultrasonic reactor in-reactor fluoroscopy system will be required. Furthermore, the resolution in the in-plane direction of the core is the distance R1 between the ultrasonic transducer 7 and the upper end surface of the core.
Because of the dependence on C, there are drawbacks such as deterioration of resolution when attempting to move the ultrasonic transducer arc sufficiently far from the reactor core, which is an extremely high radiation source.

[Summary of the invention]

This invention was made in order to eliminate the drawbacks of the conventional ones as described above, and by providing an isotropic scattering body that scatters ultrasonic waves isotropically at the upper end of the top of the fuel assembly that constitutes the reactor core. The present invention aims to provide an ultrasonic nuclear reactor fluoroscopy system that can use a spatially spread ultrasonic beam, that is, a fan beam, and thereby image the upper part of the reactor core with high resolution using a holographic method based on the synthetic aperture method. be.

[Embodiments of the invention]

First, we will describe the holographic method (9) based on the synthetic aperture method, which is the basic idea of this invention, and will further clarify the features of this invention. I think it is meaningful to keep it, so I do it. As mentioned above, one of the resolutions when imaging the upper core situation according to this invention is the resolution related to the distance between the ultrasonic transducer and the target in the upper core (this is called distance resolution). ).
Another is the positional resolution in the in-plane direction at the upper part of the core (this is called azimuth resolution). In this invention, in order to improve the resolution of these two types, K and M, respectively, are so-called pulse pressures in the field of electromagnetic waves (radar). 1. It is possible to apply the Tombler sharpening method to ultrasonic waves.

First, the pulse compression method will be described below. As shown in Figure 3, the resolution of the signal in the distance direction is different from that of the conventional method in that it uses the time difference Δt of the scattered reflected waves from the target on the object surface after the pulse of the ultrasonic beam is transmitted. It's the same way of thinking. That is, the time t from the ultrasonic transducer to reception after being scattered and reflected by a target on the surface of an object at a distance RK is R, and the resolution δR in the distance direction is δR, where the inclination angle is α. Since the pulse time width of the transmitted ultrasonic beam must be shorter than Δt in the above equation, it is given by Δt, SeCα.

That is, the higher the resolution is sought, the shorter the pulse time width needs to be. It has already been mentioned that this is one of the drawbacks of the conventional example. Here, instead of a constant carrier wave of the transmitted ultrasound beam (often the resonant frequency of the ultrasound transducer), a linear frequency modulated transmission signal (chirp signal) is used. An ultrasonic transducer emits a linearly frequency-modulated signal within the pulse time width T of the transmitted ultrasonic beam, and receives scattered reflected waves from the target on the object surface, which is the opposite of the linear frequency modulation. Pulse compression is performed by passing it through a matched filter that weighs the characteristic frequency vs. delay time characteristic, and the larger the frequency shift Δf, the greater the pulse compression ratio, improving the distance resolution. This is shown in FIG. That is, according to this pulse compression method, the distance resolution can be released from the pulse time width of the transmitted ultrasonic beam, and one of the drawbacks of the conventional method can be overcome.

Next, a Doppler sharpening method for improving the resolution in the azimuth direction will be described below using FIG.

In this case, the ultrasonic transducer transmits an ultrasonic fan beam onto the surface of the object while moving at a speed V in the scanning direction. At this time, when looking at the target on the object surface from the ultrasonic transducer, the target is
It can also be seen that it is moving at a relative speed corresponding to the traveling speed V of . Therefore, the scattered reflected waves from the target on the object surface, which are received by the ultrasonic transducer, exhibit the Doppler effect.

Assuming that the ultrasonic beam emitted from the ultrasonic transducer is unmodulated, the emitted signal U(t) is U(t) =
A(7eXp (, Fat). Here, AO
is the amplitude, ω0 is the carrier angular frequency, and j is the imaginary unit. The ultrasonic transducer is moving at a constant speed V and receives scattered reflected waves from a fixed target (x, r) on the object surface.

The received sign g(t) is expressed as. Here, A is the amplitude of the received signal, R(t
, ) is the distance between the ultrasonic transducer and the target at time t, and C is the speed of sound. Letting the phase of the received signal g(t) be φ(1), φ(t)=ω, t−R(t) λ. However, λ is the wavelength. Further, R(t) is defined as the distance R between the ultrasonic transducer scanning plane and the object surface in the range where the Fresnel approximation is established as shown in Fig. S. In other words, it becomes . Here, it can be seen that the Doppler shift frequency fd is given by. This temporal change in fd provides the phase history of the ultrasound received signal along the ultrasound transducer scanning direction. That is, the Doppler shift width (Doppler bandwidth) that occurs from the moment the target enters the ultrasonic beam from the ultrasonic transuser until it exits.B
d, therefore, the time resolution Δt is B(1-', and as a result, the resolution δ in the azimuth direction is δX = v, Bd' =-. However, D is the ultrasonic transformer. This is the aperture length of the transducer.As is clear from the above equation, the azimuth resolution is basically released not only from the distance R between the ultrasonic transducer and the object surface, but also from the wavelength. It can be seen that the drawbacks seen in the conventional example have been completely overcome.In fact, in contrast to the conventional example, where the resolution improves as the aperture length of the ultrasonic transducer increases. Generally, the smaller the aperture length, the better the resolution is, which is the key to this dog-sharpening method.
It is also a sign. This idea can also be explained by the idea of so-called synthetic aperture. FIG. 6 shows the movement of the ultrasonic beam as seen from the target on the object surface.

While the ultra-high wave transducer moves from A to C in Figure 6, scattered reflected waves from the target on the object surface can be obtained as received waves. This means that the ultrasonic transducers are one element of a virtual one-dimensional array of length L arranged in the direction of travel, and that they occupy the positions of the elements of this virtual array one after another. This is equivalent to irradiating the target with an ultrasonic transducer array having an aperture length of L, and this isometrically synthesized virtual aperture length is called the synthetic aperture length. Here, FIG. 7 illustrates the phase history according to the Doppler shift (K) of the ultrasonic reception signal at the above-mentioned synthetic aperture length. In other words, ``azimuth direction processing is basically the same as distance direction processing, and by passing it through a matched filter with characteristics opposite to the phase history shown in Fig. 7, targets on the surface of objects dispersed in the azimuth direction are We show that more scattered ultrasound energy can be concentrated or compressed at this target location. Therefore, the ultrasonic waves scattered and reflected from the surface of an object, which are sequentially received by the ultrasonic transducer, are distance compressed (pulse compressed), and then the same distance signals are extracted from the distance compressed signals to create an ultrasonic transducer. It is sufficient to rearrange the deusers in the scanning direction and perform azimuth compression using the synthetic aperture length as a unit.If this azimuth compression is performed sequentially for each same distance, an object surface image can be formed.

In the above explanation, azimuthal compression was described using the Doppler sharpening method. That is, the premise is to generate a Doppler phenomenon between a target on an object surface and a target by emitting an ultrasonic beam while continuously scanning an ultrasonic transducer.

On the other hand, it will be described below that this azimuthal compression can also be achieved by using the distance history between the ultrasonic transducer and the target on the object surface, without using the phase history based on the Doppler shift frequency.

In this case, the ultrasonic transducer may emit an ultrasonic beam while continuously scanning, or may emit and scan sequentially. The time from transmission to reception of the ultrasound beam from the same target on the object surface, that is, the distance information included in the ultrasound signals received by the ultrasound transducer at each position on the scanning plane, is the fifth This is obtained as a distance history as shown by the dashed line in the figure. After applying distance compression to each received signal of the ultrasonic transducer, if we aggregate (compress) those on such a distance history curve to the apex (extreme point) of that curve, we can use the Doppler sharpening method. Similarly distributed in the scanline or azimuth direction, ultrasound energy (from the target) can be compressed to the target location.

As mentioned above, the above method has achieved considerable success in the field of ground mapping using electromagnetic waves (radar).

This is because it can be assumed that the surface target (ground target) irradiated by electromagnetic waves has an approximately isotropic scattering pattern compared to the wavelength of the electromagnetic waves. On the other hand, in ultrasonic reactor internal fluoroscopy equipment, the object surface target, that is, the surface of the reactor internal structure, is a metal surface, and when irradiated with a spatially spread ultrasonic beam, the object surface target is obliquely incident on the object surface target. follows the so-called law of reflection, and the reflected component in one direction from the ultrasonic transducer at the position where the sardine sound beam was emitted is extremely small, making it difficult to apply the above method in terms of the S/N ratio (signal-to-noise ratio). I didn't get it. In other words, the importance of one of the basic constituent elements of the invention is that an isotropic scattering body is provided to scatter and reflect ultrasonic beams isotropically on the upper end surface of the top of the fuel assembly constituting the reactor core, which is the object surface. is exactly what this point is.

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 9, l is the reactor vessel, and A is the i-th.

The reactor core consists of the fuel assemblies shown in the figure, 3 to 6 are the same upper core mechanism as shown in Figure 1, the rotating plug, the reactor core, and the liquid reactor coolant. Ultrasonic transducer-1g transmits an ultrasonic beam spread out toward the upper end of the reactor core and receives scattered reflected waves from the upper end surface of reactor core-A. , a drive mechanism for scanning at a constant speed in the horizontal plane above 2A, qA is a measurement control circuit that generates an ultrasonic beam in the ultrasonic transducer 7A, and scatters from the upper end surface of the reactor core. When the reflected waves are received, the position of the ultrasonic transducer 7A, processing in the distance direction from transmission to reception of the ultrasonic beam, and processing of the ultrasonic beam in the direction of travel of the ultrasonic transducer 7A are performed. phase hiss of the received sound wave signal) IJ-
From K to core J
, a measurement calculation unit (MA) for converting the AJ end face image into an image and displaying it on a monitor TV, etc., and a control unit for controlling the drive mechanism for horizontally scanning the ultrasonic transducer 7A according to a predetermined mode. (CO).

Next, the operation will be explained. When exchanging fuel for two people in the reactor core when the reactor output is stopped, the upper core mechanism 3 is moved from above the two people in the core by a rotating plug q that is eccentric from the center of the reactor vessel l, and then the ultrasonic transducer −
Is 7A a 1 measurement control circuit? According to the control signal from A, the drive mechanism g positions the reactor core A above the core A, and its ultrasonic beam transmitting surface (receiving surface) is opposed to the upper end surface of the core two. Up to this point, there is no difference from the conventional device (
・.

Here, not a pencil beam but a spatially expanded fan beam is irradiated from the ultrasonic transducer 7A toward the upper end surface of the two core core members. The scattered reflected waves from the upper end surface of the top of the fuel assembly constituting the upper end surface of the two core core are also received by the ultrasonic transducer 7A. Needless to say, the received signal at this time includes scattered reflected waves from a wide area of the upper end surface of the core two people irradiated by the ultrasonic beam. Ultrasonic transducer = 7
A repeats the transmission and reception of this ultrasonic beam while scanning in a straight line or in a curved line in the horizontal scanning plane above the core A. The measurement control circuit 9A controls the transmission and reception timing of the ultrasonic beam, amplifies the sequentially received ultrasonic reception signals, and performs distance direction processing and azimuth processing using the synthetic aperture length as a processing unit. Directional processing is performed to convert the top view of the core and the two people into an image, which is then displayed on a display device such as a monitor television.

Here, FIG. 10 shows an example of an isotropic stack provided at the top of a fuel assembly that constitutes two reactor cores.

In FIG. 10, 5.2/ is one fuel assembly among the many fuel assemblies that make up the core JA, 22 is a fuel assembly, 2/ is a handling head provided at the top,
3 is an isotropic scattering body provided on the upper end surface of the top of the handling head for isotropically scattering ultrasonic waves. Usually, the fuel assembly 2/ has a large number of fuel pins arranged in a hexagonal wrapper tube, and the upper portion of the wrapper tube is connected to two handling heads. The interior of the two handling heads is hollow so that liquid sodium, which is a coolant, flows from the bottom to the top. Chapter S
The figure shows the top of the handling head 22, including the joint between the trumpet-shaped fuel assembly 21 and the handling head 22, and there is a small A large number of isotropic scatterers 3 each consisting of a hemispherical convex portion having a radius equal to or larger than the ultrasonic wavelength are spread over the surface. These isotropic scatters 23
As a result, the ultrasonic beam is scattered approximately isotropically at the top end surface of the handling head section λ. Therefore, no matter which direction the ultrasonic beam is obliquely incident on, a part of it is surely scattered in the direction of incidence and received by the ultrasonic transducer 7A.

In the above embodiment, the ultrasonic transducer 7A is used for both transmitting and receiving ultrasonic beams, but it is also possible to use two ultrasonic transducers, one for transmitting and the other for receiving. Alternatively, an array configuration consisting of a plurality of ultrasonic transducers may be used.

Further, although the isotropically distributed body 23 on the upper end face of the fuel assembly is made up of a large number of small hemispherical protrusions, it is also possible to use truncated pyramid-shaped pieces having curved outer surfaces.

〔Effect of the invention〕

As described above, according to the present invention, a cubic scatterer is provided on the top end surface of the fuel assembly to scatter the ultrasonic beam almost isotropically, and a spatially spread ultrasonic beam can be used. Since the structure is designed to efficiently receive scattered reflected waves from the top of the fuel assembly, it is possible to image the upper end of the core consisting of many fuel assemblies with high resolution, making it extremely useful as a highly accurate monitor inside the reactor. This has the effect of providing a sonic reactor internal fluoroscopy device.

[Brief explanation of the drawing]

Fig. 1 is a conceptual diagram showing a conventional ultrasonic nuclear reactor internal fluoroscopy system, Fig. 2 is a conceptual diagram illustrating the resolution of the conventional system, and Figs. 3 and 9 show the distance direction resolution of the present invention. Conceptual diagrams for explaining, Figures S to 3 are conceptual diagrams for explaining the azimuth resolution in this invention, and Figure 9 is a conceptual diagram showing an embodiment of the ultrasonic nuclear reactor internal fluoroscopy device according to the invention. The configuration diagram, FIG. 70, is a perspective view showing the top shape of a fuel assembly used in the device of the present invention. /...Reactor vessel 1.2A...Reactor core, 3...Core upper mechanism, Ri...Rotating plug, 5...Reactor lid, 6...Liquid sodium, 7A...Ultrasonic transducer,...
・Drive mechanism? A...Measurement control circuit, 21...Fuel assembly 1. Here: Handling head part, 3: Isotropically distributed body. In addition, in the figures, the same reference numerals indicate the same or equivalent parts. 1 figure, 2 figures of the Asahi figure, 3 figures, 4 figures, 5 figures, 8 sound a, Tranistacer → Shingo-1, 6 figures, 7 figures. 8, 9, 9, 10, procedural amendments (voluntary), Mr. Chief of the Temple Authority □, small incident display Showa! Patent No. 41 (7/!0) Name of the invention Relationship to the ultrasonic reactor fluoroscopy device correction case Patent applicant address ° 2-2-3 Marunouchi, Chiyoda-ku, Tokyo Issue name
Name (601) Mitsubishi Electric Co., Ltd. Representative Hitoshi Katayama Agent Address 4-1 Marunouchi Building 4th Floor 6, 2-1 Marunouchi, Chiyo 111-ku, Tokyo Contents of Amendment (1) Scope of Current Patent Claims Amend the description as shown in the attached sheet. (2) Correct the description of “fuel” on page 6, line 19 of the specification to “fuel” (3) Correct the description of “portion irradiated with ultrasonic beam” on page 6, line 19 of the specification to “fuel” The area irradiated with the ultrasonic beam is corrected. (4) Change the description of “e” on page 7, line 3 of the specification to rfJ
and correct it. (5) The statement "so-called" on page 70, line 77 of the specification is amended to "said to be". (6) The description of "Toppler sharpening method" on page 10, line 1 of the specification is amended to read "Doppler sharpening method." (7) The description of “Fig.
θ diagram”. (9) The description of ``scattering'' on page 23, line 16 of the specification is amended to ``scattering.'' 2. Scope of Claims (1) An ultrasonic nuclear reactor fluoroscopy device for monitoring the inside of a nuclear reactor, especially the upper part of the core, which is an isotropic device that constitutes the core and scatters ultrasonic waves almost isotropically. A scattering body is located above the reactor core and transmits a spatially spread ultrasonic beam to the reactor core from above the reactor core. An ultrasonic beam that irradiates the upper part of the reactor core and sequentially receives scattered waves at regular intervals from a wide area of the upper part of the core irradiated with the ultrasonic beam by scanning in the horizontal direction, that is, from the upper end surfaces of the tops of the numerous fuel assemblies. It includes a sonic transducer and a measurement control circuit that performs transmission, reception, signal processing, and control of the ultrasonic wave, and the position of the ultrasonic transducer, the time from transmission to reception of the ultrasonic wave, and An ultrasonic nuclear reactor in-reactor fluoroscopy system, characterized in that the upper part of the reactor core is imaged by using a phase delay or a time change in phase of an ultrasonic reception signal that is swamped in a horizontal scanning direction. (2) The ultrasonic nuclear reactor fluoroscopy device according to claim 1, wherein the ultrasonic transmission signal transmitted from the ultrasonic transducer is a linear frequency modulated signal, that is, a chirp signal. . (3) When determining the time change in the phase of the ultrasonic reception signal along the horizontal scanning direction of the ultrasonic transducer, when the ultrasonic transducer and the core upper target are moving in the horizontal scanning direction, 3. The ultrasonic nuclear reactor fluoroscopy system according to claim 1 or 2, characterized in that the Doppler shift frequency is determined by the relative velocity occurring between the two. (4) The Doppler shift frequency is calculated within the synthetic aperture length determined by the spatial wave angle of the ultrasonic beam and the distance between the ultrasonic transducer and the top surface of the core. The ultrasonic nuclear reactor fluoroscopy device according to scope 3. (5) When delaying the phase of the ultrasonic received signal in the horizontal scanning direction of the ultrasonic transducer, between the ultrasonic transducer and the upper core target on the scanning line in the horizontal scanning direction. 3. The ultrasonic nuclear reactor internal fluoroscopy system according to claim 1 or 2, characterized in that the distance history generated in the above is used. (6) The distance history is calculated within the synthetic aperture length determined by the spatial spread angle of the ultrasonic beam and the distance between the ultrasonic transducer and the top surface of the core. (7) The isotropically dispersed antibody is , a patent claim characterized in that a large number of small hemispherical convex portions with a radius equal to or larger than the ultrasonic wavelength are arranged on the outer circumference or inner circumference of the top end face of the fuel assembly. Range 1, 2, 3 or 3
Ultrasonic nuclear reactor internal fluoroscopy device described in Section 1. (8) Isotropically dispersed antibodies are small but have a truncated pyramid shape with a curved surface on the outer surface having a curvature comparable to or greater than the ultrasonic wavelength, and are laid in large numbers on the outer or inner circumference of the top of the fuel assembly. An ultrasonic nuclear reactor in-reactor fluoroscopy system according to claim 1, 3, or 5, characterized in that:

Claims (1)

[Scope of Claims] (1) In an ultrasonic reactor in-reactor fluoroscopy device for monitoring the inside of a nuclear reactor and the upper part of the 41 core, an isotropic device that constitutes the core and scatters ultrasonic waves almost isotropically. A scatterer is positioned above the reactor core and transmits a spatially spread ultrasonic beam to form a large number of fuel assemblies thrown onto the upper end surface of the top of each fuel assembly. IFg is irradiated with the ultrasonic beam and is scanned in the horizontal direction to sequentially receive scattered waves from the upper part of the core, that is, the upper end surface of the top of the large number of fuel assemblies, at regular intervals. and a measurement control circuit that performs transmission, reception, signal processing, and control of the ultrasound, and the position of the ultrasound transducer and the time from transmission to reception of the ultrasound. Furthermore, tf! images the upper part of the heart using the time change of the phase delay or phase depression of the received ultrasound signal along the horizontal scanning direction.
ig, an ultrasonic reactor internal fluoroscopy system. (g) Ultrasonic nuclear reactor internal fluoroscopy according to claim 1, characterized in that the ultrasonic transmission signal emitted from the ultrasonic transducer is a linear frequency modulated signal, that is, a chirp signal. Device. (J) When determining the time change in the phase of the ultrasonic reception signal along the horizontal scanning direction of the ultrasonic transducer, the ultrasonic transducer and the core upper target while moving in the horizontal scanning direction are measured. 3. The ultrasonic nuclear reactor fluoroscopy system according to claim 1 or 2, characterized in that the Doppler shift frequency is determined by the relative velocity occurring between the two. (4') The Doppler shift frequency is calculated within the synthetic aperture length determined by the spatial spread angle of the ultrasonic beam and the distance between the ultrasonic transducer and the top surface of the core. The ultrasonic nuclear reactor fluoroscopy device according to scope 3. (-1) When reducing the phase delay of the ultrasonic reception signal along the horizontal scanning direction of the ultrasonic transducer, the ultrasonic transducer traveling in the horizontal scanning direction and the core upper target are The ultrasonic nuclear reactor internal fluoroscopy system according to claim 1 or 2, characterized in that the distance history occurring between the two is used. (6) The distance history is calculated within a synthetic aperture length determined by the spatial spread angle of the ultrasonic beam and the distance between the ultrasonic transducer and the upper end surface of the core. Ultrasonic nuclear reactor internal fluoroscopy device described in Section 1. (iv) Isotropic scatterers consist of small hemispherical protrusions with a radius comparable to or larger than the ultrasonic wavelength, and are spread in large numbers on the outer or inner periphery of the top end face of the fuel assembly. An ultrasonic nuclear reactor fluoroscopy device according to claim 1, 1, 3, or 3, characterized in that: (&) Although the isotropic scatterers are small, they have a trapezoidal shape on the outside with a curved surface with a curvature comparable to or greater than the ultrasonic wavelength, and are spread in large numbers on the outer or inner circumference of the top of the fuel assembly. Claim 1, paragraph a, characterized in that:
3. The ultrasonic nuclear reactor in-reactor fluoroscopy device according to item 3, item S, or item S.