JPH0315129B2 - - Google Patents

Description

[Detailed Description of the Invention] <Field of Application of the Invention> The disclosed technology is a fluoroscopic system for monitoring attitude abnormalities under abnormal conditions of fuel assemblies and control rods of a reactor core set in a container of a nuclear reactor such as a fast breeder reactor. Belongs to the field of transducer device structure technology.

<Prior Art> As is well known, in a nuclear reactor such as a fast breeder reactor, liquid metallic sodium is stored and circulated in a container due to the advantages of heat conduction and heat generation. The fuel assemblies of the reactor core set therein are also immersed in the liquid metal sodium.

However, the lowering of the internal fuel assembly sets and control rods causes the so-called
If the upper drive mechanism is moved laterally and horizontally under an abnormal situation where the upper drive mechanism is not inserted as set due to the core gap interposed therebetween, the fuel assembly interposed between the core gap will interfere and be destroyed. There is a possibility that

Therefore, to ensure that the fuel assembly and control rods are not interposed in the core gap, we constantly monitor whether they are properly set or not.
Detecting abnormalities is essential for safely operating a nuclear reactor.

However, since it is impossible to monitor and detect the inside of the container drive mechanism with the naked eye under the radioactive atmospheric conditions, indirect sodium fluoroscopy using an ultrasonic transducer is usually used as is well known. .

To briefly explain the device as a sodium fluoroscopy means with reference to FIG. 1, liquid metal sodium 3 is stored inside a container 2 of a nuclear reactor 1 and circulates between it and an intermediate heat exchanger (not shown). A reactor core 4 immersed in water is filled with well-known fuel assemblies 5, and an upper drive mechanism 6 having a control and instrumentation mechanism seals the upper part of the vessel 2 with a shielding plug 7.
The shielding plug 7 is provided with a transducer drive mechanism 9, and the lower part of the holder 10 is provided with a transducer 11. A controller 12 and an oscillator 1 are installed outside the container 2.
3, an amplifier 14, and a control circuit 16 having a signal processing circuit 15, and the signal processing circuit 15
The core 4' is connected to the CRT 17 and placed on the CRT 17.
Images of the fuel assembly 5' and the upper mechanism 6' are formed for monitoring purposes.

Then, the transducer 11 was rotated and moved in a horizontal plane via the transducer drive mechanism 9, and the transducer 11 was installed so that the core gap 18 between the reactor core 4 and the upper mechanism 6 faced each other. The transducer 1 with respect to the reflector 19
1 emits an ultrasonic pulse, detects its reflected echo, monitors the detection signal on the CRT 17, monitors fuel assemblies and control rods under abnormal conditions protruding into the core gap 18, and sees through the presence or absence of them. death,
In the event of an abnormality, appropriate measures were taken.

<Problems with the prior art> However, in the sodium fluoroscope of the prior art described above, as shown in FIG.
The detected image of the reflected echo on the CRT 17 obtained by being reflected from the is,
Since no detection signal appears, it is possible to indirectly see through the core gap 18 of the abnormal fuel assembly.

However, as shown in FIG. 2, although indirect abnormal intervening states can be detected by scanning in the horizontal direction, there is a drawback in that the positioning of the ultrasonic pulse emission direction cannot be performed when vector analysis is performed.

In order to deal with this, it is necessary to rotate the rotating plug 8 provided on the shielding plug 7, and the rotation of the rotating plug 8 has disadvantages in terms of airtight sealing of the shielding plug 7. This was difficult to do in terms of interference with the control rod due to the body or improper separation.

<Object of the Invention> The object of the present invention is to have a single transducer of a sodium fluoroscopic device based on the above-mentioned prior art, and by two-dimensional scanning of the transducer, floating fuel assemblies are separated from the core and upper part of the defective control rod. The problem of the interposition in the core gap between the mechanism and the mechanism was considered a technical issue to be solved, and the horizontal angle and its position were determined while taking advantage of two-dimensional monitoring through indirect fluoroscopy using ultrasonic scanning in liquid metal sodium. This is an excellent feature that benefits the field of nuclear power application in the energy industry by making it possible to detect the position of control rods caused by floating fuel assemblies between the core gap and defective disconnection, thereby ensuring safe reactor operation. The purpose of the present invention is to provide a sodium fluoroscopic device with a high degree of accuracy.

<Structure of the Invention> In other words, the present invention provides a reactor core immersed in liquid metal sodium in a reactor vessel and an upper drive mechanism disposed above the reactor core, which are opposed to each other with a core gap in between. In a sodium fluoroscopy device consisting of an ultrasonic transducer and a reflector, a holder extends from a transducer drive mechanism disposed above the container into the container, and a holder is arranged opposite to the holder. A pair of swing arms are attached to the holder so that they can be opened and closed so that the holder can be folded up and down in the direction, and one transducer is attached to the lower end of the holder, and at least one transformer is attached to each swing arm. This sodium fluoroscopy apparatus is characterized in that at least three transducers are arranged at the same horizontal level when a transducer is attached and the swing arm is opened with respect to the holder.

In the above-mentioned apparatus of the present invention, the plurality of swing arms are folded onto a holder that is integrally extended to the transducer drive mechanism, and the shield plug can be easily inserted into the reactor vessel through the insertion hole of the shield plug. During indirect fluoroscopy monitoring, which detects floating fuel assemblies under abnormal conditions and control rods that are not disconnected, which are interposed in the core gap between the upper drive mechanism and the reactor core, Open the swivel arm to the above holder,
At least three transducers provided on the holder and the rotating arm are arranged horizontally in a row to scan a horizontal plane in a predetermined manner, and are faced to each other with the core gap of the ultrasonic pulse to be emitted therebetween. If the reflected echo from the reflector plate is masked by a floating fuel assembly or a control rod that is improperly disconnected between the core gaps, the masking position of the detected reflected echo will be reliably monitored on the CRT. Technical measures have been taken to ensure that the positioning can be determined through a comprehensive analysis of the information and that appropriate measures can be taken.

<Embodiment - Configuration> Next, an embodiment of this invention will be described as follows based on the drawings from FIG. 3 onwards. Furthermore, the first
The same aspects as those in FIGS.

10' is a holder, and as shown in FIGS. 3, 4, and 6, a pair of swing arms 10'', 10'' can be freely opened and closed in opposite directions through bearings 20, 20, . . . at the bottom of the holder. When housed in the holder 10' and closed, it can be inserted into and pulled out of the insertion hole 21 for setting the shielding plug 7 of the vessel 2 of the reactor 1, as in the conventional case. The lower end of a rotating shaft 22 for opening and closing the rotating arms 10'', 10'' extending downward from the lever drive mechanism 9 is connected to one rotating arm 10'' by a bevel gear mechanism 24 on one side via a bevel gear mechanism 23. The rotating arm 10'' on the other side can be freely opened and closed by 90 degrees around the bearing 20, and the swing arm 10'' on the other side can be opened and closed by 90 degrees around the bearing 20 at the same rotational speed by means of an adjustment gear mechanism 26. There is.

Further, rotation shafts 27, 27 for other transducer positioning mechanisms extending downward from the transducer drive mechanism 9 are connected to the respective rotation arms 10'' through other bevel gear mechanisms 28, 28 at their lower ends. ，
Shafts 29, 29 mounted on the lower rotating shaft of 10"
The ball screws 31, 31 are rotatable via bevel gear mechanisms 30, 30 provided in the transducer 11,
11 female threads 33, 33, so that each transducer 11, 11 can be moved forward and backward in a predetermined manner on each swing arm 10'', 10'' along guides 34, 34. .

Another transducer 11 is provided at the inner bottom of the holder 10' at the same level as the pivot arms 10'', 10'', and therefore, there is no space inside the holder 10'. Three transducers 11, 11, 11 are built-in,
Due to the above-mentioned undulation, the swing arms 10'', 10'' can be opened and closed freely, and when the swing arms 10'', 10'' are in the horizontal state in the open state, the left and right transducers 11, 11 on the same level are relative to the center transducer 11. Their positions can be changed and adjusted with respect to each other.

Therefore, when set inside the container 2, the insertion hole 21 of the shielding plug 7 is closed in a retracted state and inserted therein, and when ultrasonic fluoroscopy is performed, it is opened in the open state as shown in Fig. 3. Being able to do the work.

Further, as shown in FIG. 5, each transducer 11, 11, 11 makes the radiation angle of the ultrasonic wave set to α and makes it incident on the reflection plate 19, and the reflected echo is the signal of the control circuit as in the conventional case. It is shown in the form of a CRT 17 via a processing circuit 15.

Furthermore, since each transducer 11, 11, 11 is configured to emit ultrasonic pulses to each other at an angle of α° as shown in FIG. If there is a floating fuel assembly 5'' in the core gap 18 between the two, the reflected echo will be masked and will not appear on the CRT 17, but in this case, as shown in FIGS.
7 Taking the scanning angle θ° from the left side of the longitudinal section and taking the height as its elevation, the three transducers 1
1, 11, 11 horizontally scan with a phase difference, the phase difference is used through the signal processing circuit 15 to determine the angle θx° and the height of the floating fuel assembly 5'', and to determine its accuracy. The correct positioning can be displayed as shown in FIGS. 7 and 8.

<Embodiment - Effect> In the above-described configuration, the rotating arms 10'', 10'' are closed in the holder 10' and set in a straight line state in a stored state, and inserted into the container 2 through the insertion hole 21 of the shielding plug 7 of the container 2, The transducer drive mechanism 9 is operated to rotate the rotation shaft 22, and the bearings 20, 20, . to each swivel arm 10″,
10'' is opened to 90 degrees as shown in FIG. 27 is rotated in a predetermined manner, the ball screws 31, 31 are rotated via the bevel gear mechanisms 28, 28, and 30, 30, and the transducers 11, 11 in the swing arms 10'', 10'' are rotated by the screws 32, 32. Guide in place 3
The left and right transducers 1 are moved forward and backward along the lines 4 and 34 relative to the center transducer 11.
1 and 11 are determined relative to each other.

In this way, each transducer 11, 11, 1
1 is set, an operating ultrasonic wave is emitted as shown in FIG. 9A, and the pulses cause floating fuel assemblies and Scanning is started using three transducers to monitor the intervening state of the fuel rod that has failed to separate.

At that time, if there are no floating fuel assemblies or control rods that are not disconnected between the core gap 18, the emitted ultrasonic monitoring pulse will not be masked and will be normal as shown in Figure 9 (b). The status is displayed on the CRT 17.

However, for example, if the floating fuel assembly 5'' is interposed at the core gap 18 as shown in FIGS. 7 and 8, the ultrasonic wave covering the transducer 11 on the left side of FIG. Since the right side of the monitoring pulse is masked, the reflected echo pulse on the right side is missing as shown in Figure 9 (c).
An image of the CRT 17 is obtained. On the other hand, since the center of the monitoring pulse from the transducer 11 in the middle is masked, an image with no reflected echo in the center appears on the CRT 17, as shown in FIG. 9D. Furthermore, in the rightmost transducer 11, the left side of the monitoring pulse is masked, so that a pattern in which the left side reflected echo is absent is obtained on the CRT 17, as shown in FIG. 9E.

These states are not only visually recognized on the CRT 17, but also processed by the computer in the signal processing circuit 15, and the angles and ultrasonic pulses are displayed on the CRT 17 as shown in FIGS. 7 and 8. The distance in the traveling direction can be clearly visualized and shown, so the image of the floating fuel assembly 5 appears clearly, and its positioning can be determined reliably.

It goes without saying that the phase difference between the masking positions of the monitoring ultrasonic pulses for the floating fuel assembly 5'' of these three transducers in FIG. 5 can be easily calculated using a predetermined circuit. be.

In this way, not only can the angle from the predetermined reference position of the three transducers be easily determined by horizontal operation of the three transducers, but also the directional distance of the monitoring ultrasonic waves can be easily determined.
positioning can be determined reliably.

It goes without saying that the embodiments of the present invention are not limited to the above-mentioned embodiments; for example, four or more transducers may be used, and the target is not limited to floating fuel rods. , it goes without saying that this is also carried out for control rods that have been disconnected incorrectly as described above.

<Effects of the Invention> According to the present invention, basically, floating fuel assemblies and separations that may be present in the core gap between the reactor core and the upper mechanism in the vessel in a transducer such as a fast breeder reactor can be avoided. In a sodium fluoroscopy system using a transducer that indirectly monitors the presence of defective control rods by scanning with ultrasonic pulses, at least 3
By performing horizontal operation using multiple transducers, the distance from each transducer can be reliably detected, and therefore, the positioning of floating fuel assemblies, etc. in the core gap can be reliably determined. Therefore, since this can be dealt with accurately, safety measures in nuclear reactor operation are greatly improved, which is an excellent effect.

In addition, since the shielding plug does not require rotating the rotary plug, an excellent effect is achieved in that indirect monitoring transducer operation using the ultrasonic scanning can be reliably guaranteed.

By installing a swing arm on which a plurality of transducers are attached to a holder installed on the transducer drive mechanism so that the holder can be opened and closed, it is possible to easily set the sodium fluoroscopic device in the container with the holder. There is an advantage that the shielding plug can be inserted and set through the insertion hole provided in the shielding plug.

Also, with the holder set through the small insertion hole set in the container, each swing arm is opened, and at least three transducers are positioned at different positions within the same horizontal level so as to face the reflector. Therefore, during ultrasonic scanning, the ultrasonic pulses of the transducer from different positions are masked by floating fuel assemblies interposed in the core gap, etc.
Therefore, the pulse of the reflected echo will appear as a missing shape on the CRT, which has the effect that its presence can be easily recognized on the CRT, and that different transducers at each position Immediately calculate and detect the image on the CRT horizontally and in all two dimensions as well as height.
In addition, since it can be displayed three-dimensionally and the positioning of the relevant part can be immediately and accurately determined, an excellent safety effect is achieved in that the optimum countermeasure can be quickly taken.

In addition, since both the holder and the swing arm have a certain distance in the longitudinal direction, a gear drive from the transducer drive mechanism, a rotation bar, etc. are provided inside the holder to perform opening and closing operations, as well as to operate the transducer. The mutual relative position to can be changed,
An excellent effect is achieved in that an optimum distance between the transducers can be obtained, which makes it easier to detect accurate positioning of floating fuel assemblies and the like.

[Brief explanation of the drawing]

Fig. 1 is a partial cross-sectional view schematically explaining a general sodium fluoroscopy device, Fig. 2 is a schematic plan view illustrating the positional relationship between a transducer and a reflector based on the conventional technology, and Fig. 3 and the following shows an embodiment of the present invention. It is an explanatory diagram,
Fig. 3 is a side view illustrating the opening/closing state of the swivel arms relative to the holder, Fig. 4 is a side view illustrating the retracted state of each swivel arm housed inside the holder, and Fig. 5 is a side view illustrating the retracted state of each swivel arm housed inside the holder. 6 is a schematic side view illustrating the opening/closing mechanism for each rotating arm and the transducer position adjustment mechanism; 7 is a plan view illustrating an image of a floating fuel assembly on a CRT. , FIG. 8 is a side view illustrating the same height direction, and FIG. 9 is a graph diagram illustrating the relationship between the output intensity of the reflected echo pulse of the monitoring ultrasonic wave and the angle. 2... Container, 4... Core, 18... Core gap, 11... Transducer, 19... Reflector plate, 9... Transducer drive mechanism, 10'...
…Holder, 10″…swivel arm.

Claims (1)

[Scope of Claims] 1. An ultrasonic transformer provided facing each other with a core gap between a reactor core immersed in liquid metal sodium in a reactor vessel and an upper drive mechanism disposed above the reactor core. In a sodium fluoroscopy device consisting of a transducer and a reflector, a holder extends from a transducer drive mechanism disposed above the container so as to be freely inserted into the container, and a holder extends in opposite directions relative to the holder. and a pair of pivoting arms attached to the holder so as to be openable and foldable, one transducer is attached to the lower end of the holder, and at least one transducer is attached to each pivoting arm. A sodium fluoroscope, characterized in that at least three of the transducers are arranged at the same horizontal level when mounted and the pivot arm is opened relative to the holder. 2. The sodium fluoroscopy apparatus according to claim 1, wherein the transducer attached to each of the swing arms is movable in position on the swing arm.