JPH0435001B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an ultrasonic fluoroscopy device for detecting levitation of fuel assemblies inside a fast breeder reactor, particularly between a reactor core and an upper core mechanism.

[Prior Art] In general, in a liquid metal cooled fast breeder reactor, the inside of the reactor cannot be directly inspected, so the inside of the reactor is seen through using ultrasonic waves. This will be explained below with reference to FIGS. 7 to 10. Reference numeral 1 in FIG. 7 is a reactor vessel, which is supported by a reactor building 3 and has an inner cylinder 2 installed on its inner circumferential side. A coolant 4 and a reactor core 5 are housed within the reactor vessel 1 . The reactor core 5 is composed of a plurality of fuel assemblies and control rods (not shown), and is supported by the reactor vessel 1 via a core support mechanism 6. The upper opening 1A of the reactor vessel 1 is closed by a shielding lid 7. Further, a core upper mechanism 8 is installed above the core 5 so as to penetrate through the shielding lid 7 . In a fast breeder reactor having such a configuration, the coolant 4 flows through the reactor core 5 from below to above, and is heated by nuclear reaction heat in the reactor core 5 at this time. The heated coolant 4 is introduced into a heat exchanger (not shown) via a coolant outflow pipe (not shown) connected to the reactor vessel 1, and is cooled by exchanging heat with the secondary coolant in the heat exchanger. The coolant is pressurized by a circulation pump (not shown) and introduced into the reactor vessel 1 via a coolant inflow pipe (not shown) connected to the reactor vessel 1. The same cycle is repeated thereafter.

In the fast breeder reactor having the above configuration, for example, the core 5
It is assumed that an accident may occur if the fuel assembly floats upwards from within. If such a situation is left unaddressed, secondary disasters will occur, which is not desirable in terms of reactor safety. Therefore, the space 11 between the reactor core 5 and the upper core mechanism 8 is monitored using an ultrasonic fluoroscopy device, which will be described later, to detect the above-mentioned floating of the fuel assembly at an early stage, and take prompt action. The aim is to prevent secondary disasters from occurring. This ultrasonic fluoroscope will be explained below.

That is, as shown in FIG. 7, an ultrasonic fluoroscope 20 is inserted into a predetermined position within the reactor vessel 1. As shown in FIG. This ultrasonic fluoroscope 20 includes a main body 0A passing through the shielding lid 7, and a main body 20A.
Ultrasonic transducer 21 fixed to the tip of
and a drive device 20B attached to the upper end of the main body 20A. The ultrasonic transducer 21 is configured to be movable up and down by a main body 20A and a drive device 20B, and also to be rotatable. This ultrasonic transducer 21 emits ultrasonic waves in the horizontal direction and receives the reflected waves. An ultrasonic reflector 22 is installed on the inner wall of the inner cylinder 2 on the extension line of the intermediate part 11 between the reactor core 5 and the upper core mechanism 7, facing the ultrasonic transducer 21. That is, by transmitting ultrasonic waves from the ultrasonic transducer 21 and receiving reflected waves of the ultrasonic waves from the ultrasonic reflector 22,
This detects the floating of fuel assemblies, the presence of foreign objects, and the presence or absence of control rod separation.

As shown in FIG. 8, the transducer 21 is rotated so as to be able to scan ultrasonic waves at a predetermined angle θ ₁ in the horizontal direction, and
It is designed to be able to move up and down so that it can face any position of 1, and can cover a predetermined inspection area. Note that the rotational movement and vertical movement are performed by the main body 20A and the drive device 20B as described above.
It is done by.

In this way, the ultrasonic fluoroscope 20
At an appropriate position in the axial direction, ultrasonic waves are accurately transmitted in the horizontal direction within a predetermined range toward the reflection pair 22, and the reflected waves are received to detect foreign objects such as floating fuel assemblies in the gap 11. It detects the presence. Therefore, in order to perform accurate outflow, it is necessary to accurately set the position of the ultrasonic transducer 21. Therefore, the position of the ultrasonic transducer 21 has conventionally been set as follows.

That is, a reference reflector plate 32 is installed on the ultrasonic transducer 21 side of the tube plate portion 31 of the core upper mechanism 7, and this reference reflector plate 32 is used to set the position. The reference reflector 32 is the ninth
As shown in the figure and FIG. 10, the cross-shaped groove 33
It is a plate 34 with a flat surface 35 formed thereon.
is fixed with a bolt 36 in an inclined state so as not to directly face the ultrasonic transducer 21. The reason why the flat portion 35 is inclined is that the reflected wave from the flat portion 35 is unnecessary for position setting. The groove 33 consists of a vertical groove 33A and a horizontal groove 33B perpendicular to the vertical groove 33A.
3B is used to set the position in the horizontal direction. In other words, since the vertical groove 33A has a cylindrical surface as described above, the ultrasonic transducer 21 receives reflected waves only when the groove axis 33a of the vertical groove 33A and the ultrasonic transducer 21 are parallel to each other. can do. This position is the same position as the reference reflecting plate 32 in the vertical direction. Therefore, the vertical position of the ultrasonic transducer 21 can be set by lowering the ultrasonic transducer 21 a predetermined distance vertically downward from this position. Similarly, in the horizontal direction, since the lateral groove 33B has a cylindrical surface, the ultrasonic transducer 21
The ultrasonic transducer 21 can receive reflected waves only when the groove axis 33b of the lateral groove 33B becomes parallel to the groove axis 33b of the lateral groove 33B. This position is in the same direction as the reference reflecting plate 32, and scanning is performed in the horizontal direction with that direction as a reference. After setting the position of the ultrasonic transducer 21 through the above operations and fixing the position, it emits ultrasonic waves within a predetermined range, and the ultrasonic reflector 2 of the emitted ultrasonic waves
By receiving the reflected waves from 2, the presence of foreign objects such as floating fuel assemblies in the interspace 11 is detected, and the presence or absence of an abnormality is detected.

[Problems with Background Art] The above configuration has the following problems.

(1) First, the reference reflector 32 is fixed to the tube plate 31 by bolts 76 under thermally severe conditions such as thermal striping, and there is a concern that it may deteriorate over a long period of use and thereby reduce accuracy.

(2) Also, the tube plate portion 31 is located 400 degrees above the gap portion 11.
mm or more, and as a result, the ultrasonic transducer 21 is required to have a long vertical stroke, thereby causing the ultrasonic transducer 2
The main body 20A that supports the ultrasonic fluoroscopy device 20 must be made longer, and the handling device (not shown) that inserts and pulls out the ultrasonic fluoroscopy device 20 into the furnace must also be made longer. This leads to increased complexity and complexity.

(3) When setting the position in the horizontal direction using the reference reflector 32, the distance between the ultrasonic transducer 21 and the reference reflector 32 is smaller than the distance between the ultrasonic transducer 21 and the reflector 22. Therefore, there was a problem in that the error when setting the position was magnified by that amount, and the position accuracy was lowered.

(4) Furthermore, since the tube plate portion 32 is placed under severe thermal conditions as described above, there is a problem that the positional accuracy is reduced due to thermal deformation due to temperature distribution and the stopping accuracy of the shielding lid 7. It was hot.

[Object of the invention] The present invention has been made based on the above points, and its purpose is to be able to maintain its soundness even when placed under severe thermal conditions. The present invention also relates to an ultrasonic fluoroscopy device that can set the position of an ultrasonic transducer with high precision and can accurately detect obstacles, etc. in the upper part of a reactor core.

[Summary of the Invention] That is, the ultrasonic fluoroscope according to the present invention includes an ultrasonic transducer that is installed in a nuclear reactor vessel so as to be movable and rotatable and that emits ultrasonic waves in a direction across the reactor core; an ultrasonic reflector disposed in the reactor vessel on an extension of the space between the reactor core and the upper core mechanism facing the sonic transducer; A reference reflector for vertical movement, which is installed on the outer surface of the straightening tube of the upper core mechanism to face the ultrasonic transducer and is used to set the vertical position of the ultrasonic transducer; The device is characterized in that it includes a reference reflector for horizontal scanning that is installed at the end and is used to set the position of the ultrasonic transducer in the horizontal direction.

[Embodiment of the Invention] An embodiment of the present invention will be described below with reference to FIGS. 1 to 6. FIG. 1 is a vertical cross-sectional view showing a schematic configuration of a fast breeder reactor equipped with an ultrasonic fluoroscope according to the present embodiment. The inner cylinder 1 is supported on the inner peripheral side of the inner cylinder 1.
02 is installed. A coolant 104 and a reactor core 105 are housed within the reactor vessel 101 . The reactor core 105 is supported by the reactor vessel 101 via a core support mechanism 106. The reactor core 105 is composed of a plurality of fuel assemblies, control rods, etc. (not shown). Further, the upper opening 101A of the reactor vessel 101 is closed by a shielding lid 107. A core upper mechanism 108 is installed above the core 105, passing through a shielding lid 107. A tube plate 109 and a straightening tube 110 are installed at the lower part of the core upper mechanism 108 .

An ultrasonic fluoroscope 111 is installed at a predetermined position on the inner wall of the reactor vessel 101. The attached ultrasonic transducer 113 and the drive unit 114 connected to the upper end of the main body 112
It is composed of. The ultrasonic transducer 113 can be rotated in the horizontal direction by the drive section 114, and can also be moved up and down, and its elevation angle can be adjusted. By emitting ultrasonic waves using the ultrasonic transducer 113 having such a configuration and receiving the reflected waves, the presence or absence of an obstacle in the space 116 between the reactor core 105 and the upper core mechanism 108 is detected.

An ultrasonic reflector 115 is installed on the inner wall of the inner cylinder 102 at a position facing the ultrasonic transducer 113. This ultrasonic reflector 11
5 is installed on the opposite side of the ultrasonic transducer 113 across the bottom part 116 between the core 105 and the core upper mechanism 108, and as shown in FIG. is provided within a predetermined range.

Some of the rectifying cylinders 110 located on the ultrasonic transducer 113 side are the third rectifying cylinders 110.
As shown in the figure, it is a reference reflector 121 for vertical movement that has both the functions of a rectifying cylinder and a reference reflector. This reference reflector 121 for vertical movement has cylindrical reference reflecting surface areas A and B that reflect the ultrasonic waves from the ultrasonic transducer 113 in the direction of the ultrasonic transducer 113, as shown in FIG.
and, conversely, tapered mask regions C, C inclined at a predetermined angle (α=2 degrees) or more so as not to reflect the ultrasound from the ultrasound transducer 113. Then, the ultrasonic transducer 113 moves up and down to face any area among the reference reflective surface areas A, B and mask areas C, C.

On the other hand, as shown in FIG. 6, a reference reflector 131 for horizontal scanning is installed at the end sector portion of the ultrasonic reflector 115. This horizontal scanning reference reflector 131 is provided with a reference reflector area a, a scanning reflector area b, and a mask area c provided between the reference reflector area a and the scanning reflector area b. . The width of the mask area c is greater than the spread diameter of the ultrasonic beam emitted from the ultrasonic transducer 113. By scanning the ultrasonic transducer 113 within the range of θ ₁ shown in FIG. 2, the horizontal scanning reference reflector 131 and the ultrasonic reflector 115 are continuously scanned.

The operation will be explained based on the above configuration. First, the position of the ultrasonic transducer 113 is set. The ultrasonic transducer 113 is located near the straightening tube 110 of the upper core mechanism 108. Next, the drive section 114 is activated to rotate the ultrasonic transducer 113 to emit ultrasonic waves. At this time, if the reflected wave from the reference reflector 121 for vertical movement cannot be received, the elevation angle of the ultrasonic transducer 113 is changed and rotated again to transmit ultrasonic waves. This operation is repeated to set the ultrasonic transducer 113 at a predetermined position. If the reflected wave still cannot be received, the driving device 114 is driven to move the ultrasonic transducer 113 in the vertical direction and the above-described operation is repeated. Then, by performing the vertical movement within a predetermined range, the reflected waves from the reference reflective surface areas A and B of the reference reflector 121 for vertical movement and the reflected waves from the mask areas C and C are detected, and the reflected waves from the mask areas C and C are detected. The ultrasonic transducer 113 is lowered vertically downward by a predetermined dimension from
The ultrasonic transducer 113 is positioned at a predetermined position between 116 and 116.

Next, the horizontal position of the ultrasonic transducer 113 is set. First, the ultrasonic transducer 113 is rotated in the direction of the horizontal scanning reflector 131 to detect the reference reflector area a. In this case, the reflected wave from the reference reflector area a means that the mask area c exists in a predetermined range (the reflected wave cannot be received within this range), and then the reflected wave is received. This is confirmed by After detecting the reference reflector a, the ultrasonic transducer 113 is rotated by a predetermined angle θ ₁ based on the detected position, so that the ultrasonic reflector 115 is scanned with ultrasonic waves, and the core 105 and the core The presence or absence of a foreign object in the space 116 between the upper mechanism 106 and the upper mechanism 106 is detected. If there is a foreign object in the space 116, the ultrasonic waves emitted from the ultrasonic transducer 113 will not reach the ultrasonic reflector 115.
As a result, this can be confirmed from the fact that the reflected waves from the ultrasonic reflector 115 cannot be received.

As described above, according to the ultrasonic fluoroscope 111 according to the present embodiment, the following effects can be achieved.

(1) The vertical position of the ultrasonic transducer 113 is set using the reference reflector 121 for vertical movement.
1 has a simple cylindrical structure, and
It has a structure that is integrated with the rectifier tube 110 and has the same strength as the rectifier tube 110, so that its integrity can be maintained for a long time even under severe thermal conditions such as thermal striping. This enables highly accurate position setting.

(2) The horizontal position of the ultrasonic transducer 113 is set using the horizontal scanning reference reflector 131, and the horizontal scanning reference reflector 131 is placed on the horizontal extension of the ultrasonic reflector 115. Because it is installed, the conventional tube sheet 10
9, the difference in distance does not increase the error during position setting, and highly accurate position setting is possible. The area where the horizontal scanning reference reflector 131 is installed is a place where thermal conditions such as thermal striping are relatively gentle.
Therefore, its structural integrity can be maintained over a long period of time, and it becomes possible to effectively prevent a decrease in positioning accuracy due to long-term use.

(3) Furthermore, the reference reflector 121 for vertical movement is installed directly above the intervening part 116, and thus the ultrasonic transducer 113
It is not necessary to lengthen the stroke of the ultrasonic fluoroscopy device 111, and the structure of the ultrasonic fluoroscopy device 111 can be simplified, and the structure of the device for moving the device in and out of the furnace can also be simplified, which reduces costs. It is extremely effective in terms of achieving this goal.

[Effects of the Invention] As detailed above, the fluoroscopic device according to the present invention has the following effects:
An ultrasonic transducer that is installed in the reactor vessel in a movable and rotatable manner and emits ultrasonic waves in a direction across the reactor core; an ultrasonic reflector disposed in the reactor vessel on an extension of the lower part between the two; A reference reflector for vertical movement is installed facing the ultrasonic transducer and is used to set the vertical position of the ultrasonic transducer; The present invention is characterized in that it includes a horizontal scanning reference reflector used for setting.

Therefore, the structural integrity of each device used for positioning the ultrasonic transducer can be maintained over a long period of time, making it possible to provide highly accurate positioning over a long period of time. . In addition, it is possible to simplify the configuration of not only the ultrasonic fluoroscopy device but also the device for moving the device into and out of the furnace, which not only improves reliability but also reduces costs.

[Brief explanation of drawings]

1 to 6 are diagrams showing one embodiment of the present invention, in which FIG. 1 is a cross-sectional view showing a schematic configuration of a fast breeder reactor, FIG. 2 is a view taken along the - arrow in FIG. The figure is an enlarged cross-sectional view of the part in Figure 1, and Figure 4 is a cross-sectional view showing the part in Figure 3.
5 is a cross-sectional view of FIG. 4, FIG. 6 is an enlarged view of the portion shown in FIG. 2, and FIGS. 7 to 10 show conventional examples. In the figure,
Figure 7 is a vertical cross-sectional view showing the schematic configuration of a fast breeder reactor;
8 is a cross-sectional view taken from FIG. 7, FIG. 9 is an enlarged view of the portion shown in FIG. 7, and FIG. 10 is a perspective view of the reference reflector. 101... Reactor vessel, 102... Inner cylinder, 10
4... Coolant, 105... Core, 106... Core support mechanism, 107... Shielding lid, 108... Core upper mechanism, 109... Tube plate, 110... Straightening tube, 1
11... Ultrasonic fluoroscope, 112... Main body, 11
3... Ultrasonic transducer, 114... Drive mechanism, 121... Reference reflector for vertical movement, 131
...Reference reflector for horizontal scanning.

Claims (1)

[Scope of Claims] 1. An ultrasonic transducer that is movable and rotatably installed in the reactor vessel and emits ultrasonic waves in a direction across the reactor core; An ultrasonic reflector disposed within the reactor vessel on the extension of the space between the reactor core and the upper core mechanism, and an ultrasonic reflector disposed within the reactor vessel on the extension of the lower part between the reactor core and the upper core mechanism, and an ultrasonic reflector disposed on the ultrasonic transducer side and outside of the straightening tube of the upper core mechanism. A reference reflector for vertical movement is installed on the surface facing the ultrasonic transducer and is used to set the vertical position of the ultrasonic transducer, and an ultrasonic transformer is installed at the end of the ultrasonic reflector row. 1. An ultrasonic fluoroscopy device comprising: a reference reflector for horizontal scanning used to set the horizontal position of a diaphragm. 2 The reference reflector for vertical movement has a specular reflection surface that reflects the ultrasonic waves emitted from the ultrasonic transducer in the direction of the ultrasonic transducer, and a specular reflection surface that reflects the ultrasonic waves emitted from the ultrasonic transducer in the direction of the ultrasonic transducer. The ultrasonic fluoroscope according to claim 1, further comprising a mask surface that is inclined with respect to the user. 3. Claim 1, wherein the horizontal scanning reference reflector includes a reference reflector area and a horizontal scanning reference reflector area on both sides of a mask area having no reflective surface. Ultrasonic fluoroscopy device described in Section 1.