JPH068809B2 - Ultrasonic flaw detector - Google Patents

Description

Detailed Description of the Invention

TECHNICAL FIELD OF THE INVENTION The present invention relates to an apparatus for performing ultrasonic flaw detection from the inside of a reactor pressure vessel in order to confirm the soundness of a welded portion of the reactor pressure vessel and the internal structure of the reactor. [Technical background of the invention and its problems] Generally, in a nuclear power plant, an ultrasonic flaw detection (hereinafter abbreviated as UT) is performed on a welded portion of a reactor pressure vessel (hereinafter abbreviated as RPV) during its service period. Is obligatory. Therefore, for example, in a pressurized water nuclear power plant, the internal equipment can be taken out, and the size is smaller than the RPV of a boiling water reactor (hereinafter abbreviated as BWR),
UT is performed from the inside of the RPV by using a UT device as shown in FIG. 8 because it is structurally impossible to approach from the outside of the RPV. This UT device is exclusively for a pressurized water reactor (hereinafter abbreviated as PWR), and has a support ring 101 at the center of which a support 102 is provided.
The column 102 is provided with a flaw detection arm 103 that is horizontally expandable and contractable and is rotatable and vertically movable. An ultrasonic transducer 104 is provided at the tip of the flaw detection arm 103, and UT is configured to be performed by pressing the ultrasonic transducer 104 against the inner surface of the RPV by the flaw detection arm 103. Further, the UT device is positioned by fixing the support leg 105 to the flange surface of the RPV. On the other hand, in a boiling water nuclear power plant, it is possible to approach from the outside of the RPV, so UT is performed from the outside of the RPV using a small UT device compatible with the inspection unit.
In the plant constructed before the (in-service inspection) was introduced, it was difficult to UT from the outside because the heat insulating material was in close contact with the outer surface of the RPV. Therefore, using the UT device shown in FIG. A method of performing UT from the inside of RPV has been considered. However, in the BWR, since there are core internal structures such as shrouds and jet pumps that cannot be taken out to the outside in the core region below the RPV, it is true that UT is performed using the PUT dedicated UT device shown in FIG. It's extremely difficult. In addition, the RPV of BWR is longer than that of PWR (for example, 1.1 million kw class PWR, and the distance between the flange bottoms of RPV is about 10 m).
However, in the case of a BWR of 500,000 kW class, it is 10 meters or more), and the inspection part is a narrow place like the core area (the maximum distance between the RPV and the shroud is about 400 mm).
In such a case, the method of supporting the flange surface has a problem in accuracy of the apparatus body. Further, since the UT device shown in FIG. 8 is large, it is difficult to carry it in and out of the plant and the assembling work, and a considerable assembling space is also required. Also, R
Because the structure covers the entire circumference of the flange surface of the PV, it interferes with other operation work, which becomes a critical path and causes another operation flow to be delayed. [Object of the Invention] The object of the present invention has been made in view of such circumstances, and it is possible to perform UT from the inside to the RPV of the BWR that is difficult to approach from the outside, and further, the inspection unit has a core region. Stable and highly accurate UT even in a narrow place like
It is to provide a UT device that is compact and has good operability. [Summary of the Invention] That is, an ultrasonic flaw detector of the present invention is an apparatus body mounted on the upper end of a shroud forming the core of a boiling water nuclear reactor, and is connected to both sides of the apparatus body via joint arms. A circumferential movement mechanism that is movable in the circumferential direction of the shroud, a multi-stage rod that is hung downward from the device body and is vertically expandable and contractible, and rotatable about an axis, and a multi-stage rod of this multi-stage rod. A horizontal arm provided at the lower end, a horizontal slide mechanism for horizontally sliding the horizontal arm, a probe unit rotatably provided at both ends of the horizontal arm, and an atomic unit for the probe unit. And a pressing mechanism for pressing against the inner surface of the furnace pressure vessel,
The circumferential movement mechanism has a pair of rollers that sandwich an upper end portion of the shroud, and at least one of the rollers is rotated to move in the circumferential direction of the shroud. [Embodiment of the Invention] An embodiment of the present invention will be described below with reference to FIGS. 1 to 7. FIG. 1 is a diagram showing a configuration of a UT device according to the present invention, (a) is a front view, (b) is a side view, and (c) is a plan view. This UT device includes a device body 1 set on the upper end of a shroud 30 in the RPV, a circumferential movement mechanism 2 for moving the device body 1 in the circumferential direction of the RPV (arrow α in the figure), and the device body 1 described above. It is rotatably installed vertically and in the RPV axial direction (arrow X in the figure).
A multi-stage rod 3 that is extendable and retractable, a horizontal arm 4 provided at the lower end of the multi-stage rod 3, a horizontal slide mechanism 5 that slides the horizontal arm 4 in the horizontal direction (arrow Y in the figure), and The horizontal arm 4 includes probe unit portions 6A and 6B provided at both ends thereof, and a pressing mechanism 7 for pressing the probe unit portions 6A and 6B together with the horizontal arm 4 onto the inner surface of the RPV. The apparatus body 1 has a hook 11 on the upper surface, and is hung from the upper end of the shroud 30 by a wire rope or the like. As shown in FIG. 2, the stepping motor 1 for driving the multistage rod is provided inside the apparatus main body 1.
2 is provided, and the driving gear 1 is driven by this stepping motor 12.
The rotary gear 14 provided at the upper end of the multi-stage rod 3 is driven via the motor 3. As shown in FIGS. 3 and 4, the circumferential moving mechanism 2 comprises a driving roller 16 and a guide roller 17, and the driving roller 16 is driven by a hydraulic turbine 18 via a gear mechanism 19. There is. The guide roller 17 is pressed against the inner wall side of the shroud 30 by the spring 20, and the guide roller 17 and the drive roller 16 are pressed against each other.
It has a structure in which the upper end portion of 0 is sandwiched so that there is no play. The circumferential movement mechanism 2 is connected to the apparatus main body 1 via a joint arm 15 as shown in FIG. The horizontal slide mechanism 5 is shown in FIGS.
As shown in the figure, a support roller 21 that supports the horizontal arm 4
a, 21b, 21c and 21d and a drive motor 22. Support rollers 21a to 21d are provided so as to slide in guide grooves 23 formed in the upper and lower surfaces of the horizontal arm 4. Further, the motor 22 is provided so as to drive a rack portion 25 provided at a rear portion of the horizontal arm 4 via a drive gear 24. As shown in FIG. 5, the probe unit portions 6A and 6B are composed of a probe unit 8 and a probe unit rotating mechanism 9, and the probe unit 8 is 0 ° and 45 ° with respect to the surface to be inspected, respectively.
Three probes 10a, 10 having an incident angle of °, 60 °
b, 10c. The probe unit rotating mechanism 9 has a function of rotating the probe unit 8 by 270 ° or more, and the rotation angle can be detected by an encoder (not shown). The circumferential movement mechanism 2, the multistage rod 3, the horizontal slide mechanism 5, the pressing mechanism 7, the probe unit rotating mechanism 9 and the like are the RPV.
The drive is controlled by a controller (not shown) installed outside. Next, the operation of this embodiment will be described. When inspecting the welded part of the RPV, as shown in FIG. 6, the device body 1 is set on the upper end of the shroud 30 by using a heat exchanger or the like, and the device 1 is moved to the vicinity of the surface to be inspected by the circumferential movement mechanism 2. To move. At this time, the multistage rod 3 is kept in a contracted state in order to prevent interference with the jet pump 31 (see FIG. 7). When the apparatus body 1 reaches the vicinity of the surface to be inspected, the driving of the circumferential movement mechanism 2 is stopped, the multistage rod 3 is extended and guided to the inspection location, and the probe unit 6
A and 6B are opposed to the surface to be inspected. Then, the pressing unit 7 presses the probe unit portions 6A and 6B against the inner surface of the RPV 32 as shown in FIG. At this time, the probe units 6A and 6B are scanned in the vertical direction by the multistage rod 3, and the horizontal scan is performed by the horizontal slide mechanism 5 or the circumferential movement mechanism 2. When inspecting the shroud portion, the motor 12 is used as shown in FIG. 7 (b).
After rotating the multistage pad 3 by 180 °, the same operation as described above may be performed. As described above, according to the present invention, when the apparatus main body attached to the upper end of the shroud is moved in the circumferential direction of the shroud, the probe unit moves to the inner peripheral surface of the reactor pressure vessel. When the inspection unit is located in a narrow space such as the core region of the BWR, the probe unit moves up and down in the reactor pressure vessel when the multi-stage rod is expanded and contracted in the vertical direction. However, ultrasonic flaw detection can be performed from the inside of the welded portion of the reactor pressure vessel. Further, by mounting the apparatus main body on the upper end portion of the shroud, the distance from the main body to the inspection unit is shortened, and the position control accuracy of the probe unit in the inspection can be further improved.

[Brief description of drawings]

1 to 7 are views showing an embodiment of the present invention, FIG. 1 (a) is a front view of the UT device, and FIG. 1 (b) is a side view thereof.
2C is a plan view thereof, FIG. 2 is a view taken along the line II-II of FIG. 1, FIG. 3 is a view taken along the line III-III of FIG. 1, and FIG. -IV arrow view, FIG. 5 is a VV arrow view of FIG. 1, FIG. 6 is a perspective view showing a state in which the UT device is set on the upper end of the shroud, and FIG. 7 is a probe unit to be inspected. FIG. 8 is an explanatory view showing a state of being pressed against a surface, and FIG. 8 is a perspective view showing a conventional UT device. 1 ... Device body, 2 ... Circumferential movement mechanism, 3 ... Multistage rod, 4 ... Horizontal arm, 5 ... Horizontal slide mechanism, 7 ...
Pressing mechanism, 8 ... Probe unit, 9 ... Probe unit rotating mechanism, 10a-10c ... Probe.

Claims (1)

[Claims] 1. An apparatus body mounted on an upper end portion of a shroud forming a core of a boiling water reactor, and connected to both sides of the apparatus body via joint arms and movable in the circumferential direction of the shroud. A circumferential movement mechanism, a multi-stage rod vertically extending downward from the main body of the apparatus and rotatable in the vertical direction, and a horizontal arm provided at the lower end of the multi-stage rod, A horizontal slide mechanism that horizontally slides the horizontal arm, a probe unit that is rotatably provided at both ends of the horizontal arm, and a pressing mechanism that presses the probe unit against the inner surface of the reactor pressure vessel. The circumferential movement mechanism has a pair of rollers that sandwich the upper end of the shroud, and at least one of the rollers is rotated to rotate the shroud around the shroud. Ultrasonic flaw detection apparatus characterized by moving countercurrent.