JPS593255A - Method and apparatus for ultrasonic flaw detection - Google Patents

Abstract

PURPOSE:To carry out inspection works simply and rapidly, by a method wherein a transparent radiation shielding liquid layer is formed at the outside of the inspection part of an object to be inspected and an ultrasonic flaw detecting probe is immersed in said liquid layer to be scanned along the outside of the above mentioned inspection part for flaw detection. CONSTITUTION:A transparent container 3 is provided to an ultrasonic flaw detection apparatus so as to include a welding part 2 and to surround an arranged pipe 1 while a transparent radiation shielding liquid (l) is poured in the container 3 from the upper opening thereof to fill the same and a transparent radiation shielding liquid layer 8 covering the outside of the arranged pipe 1 is formed. In this state, two ultrasonic flaw detecting probes 15 are immersed in said liquid layer 8. By this constitution, the shielding liquid layer can be easily formed and surface finishing of an object to be inspected becomes unnecessary and flaw detecting work can be carried out simply and rapidly.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasonic flaw detection method and apparatus for radioactive test objects such as atomic couplant piping, and particularly,
The present invention relates to an ultrasonic flaw detection method and apparatus that can significantly reduce radiation exposure during flaw detection and simplify inspection work.

To ensure the safety of nuclear power plant piping, etc., strict ultrasonic testing is required during the service period to check for defects such as scratches, cracks, and voids in the welded parts of the piping. However, conventional ultrasonic flaw detection for this type of piping has been carried out using the direct contact method. That is, first, approximately 10 to 20
Perform surface finishing such as smoothing and cleaning to ensure good contact between the ultrasonic flaw detection probe and the piping, then apply a couplant such as glycerin, and then apply the couplant to the welding area on the contact surface coated with this couplant. The weld was detected by sliding an ultrasonic flaw detection glove along the weld.

Approximately 10 to 20 meters around the welded area, which is the area to be inspected.
It was not possible to shield the can from radiation with lead materials, and workers were exposed to a large amount of radiation during surface finishing work and ultrasonic flaw detection. Furthermore, surface finishing operations such as surface polishing require a lot of effort, leading to a prolonged flaw detection inspection.

The present invention has been devised to effectively solve the above-mentioned conventional problems, and an object of the present invention is to reduce the exposure dose received during ultrasonic flaw detection of radioactive test objects such as atomic couplant piping. can be significantly reduced, and
It is an object of the present invention to provide an ultrasonic flaw detection method and an apparatus therefor, which can simplify and speed up inspection work.

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. This example shows ultrasonic flaw detection for a welded part of a pipe.

In FIGS. 1 and 2, reference numeral 1 denotes a pipe through which fluid containing radioactive materials of a nuclear power plant passes, and the pipe 1 is arranged vertically and is highly contaminated with radioactivity. Also,
2 is an annular welded part when the pipes 1 are connected and welded, and one is in the ultrasonic flaw detection inspection section. A transparent container 3 is provided so as to surround the pipe 1 including the welded portion 2. As shown in Fig. 3, the transparent container 3 consists of two divided pieces 4 obtained by cutting a bottomed cylinder in half in the axial direction, and by butting the divided pieces 4 against each other, the outside of the pipe 1 is made liquid-tight. A semicircular notch 4b is provided in the bottom plate 4a of the divided piece 4 so that it can be enclosed, and a rubber backing 5 is provided on the joint surface. Transparent container 4
is molded from materials such as acrylic resin with excellent translucency,
The inside of the container 3 can be visually observed.

The transparent container 3 is still fixedly attached to the pipe 1 by tightening the fixing bands 6 wound around the upper and lower parts thereof with bolts 7. A transparent radiation shielding liquid 1 is injected into the container 3 through its upper opening to form a transparent radiation shielding liquid layer 8 covering the outside of the pipe 1 . As the transparent radiation shielding liquid 2, a liquid that is transparent, has a high radiation shielding effect, and has low attenuation of ultrasonic waves, such as water, glycerin, or an aqueous solution of a heavy metal compound such as lead (lead acetate, lead nitrate, etc.) is used. The inner diameter of the transparent container 3 has a dimension that allows a predetermined radiation attenuation to be obtained by the transparent radiation shielding liquid layer 8.

An annular rotating table 9 is placed on the transparent container 3. The rotary table 9 is formed into two parts so as to surround the pipe 1, and as shown in FIG. 2, they are connected by a connecting fitting 10. Similarly, a two-split bevel gear 11 is attached to the inner peripheral portion of the annular rotary table 9, so that the rotary table 9 can be rotated horizontally by the rotation of the bevel gear 110. The bevel gear 11 is provided with a bevel gear 12 that meshes with the bevel gear 11, and the bevel gear 12 is rotatably supported by a support base 13 attached to the transparent container 3. Still on bevel gear 12,
A servo motor 14 for rotationally driving this is connected via a shaft. The servo motor 14 also supports the support base 1
3, and by the operation of the servo motor 14,
The rotary table 9 is configured to be rotated horizontally and smoothly via bevel gears 12 and 11.

On the other hand, two ultrasonic flaw detection probes 15 for detecting flaws in the welded part 2 are generally cut into the shielding liquid p of the transparent container 3, but in order to guide and move these probes 15 in the downward direction, , two rods 16 are disposed for each probe 15 in the axial direction of the container 3. A pair of rods 16, 16 for each probe 15 are provided with a predetermined gap in the radial direction of the container 3.

As shown in an enlarged view in FIG. 4, the rod 16 passes through the rotary table 9 and is connected to a servo motor 17 on the rotary table 9.
The rod 16 is configured to be rotationally driven by the operation of the servo motor 17. In addition, on the outer peripheral surface of the rod 16,
As shown in FIGS. 4 and 5, the rod 16 has a threaded hole 18a into which the rod 16 is threaded.
A horizontal plate 18 is provided which can be moved up and down by forward and reverse rotation.

This horizontal plate 18 and an elongated frame 19 to which the ultrasonic flaw detection probe 15 is attached at its tip are rotatably connected by a pin 20. On the side of frame 19,
Although an insertion hole is provided through which the pin 20 is inserted, the container 3
The inner insertion hole 21 is formed in a long hole shape along the longitudinal direction of the frame 19. Therefore, for example, by rotating only the rod 16 inside the container 3, the frame 19 is rotated up and down about the pin 20 on the container 3 side, and the inclination angle of the frame 19 is changed from the probe 15 to the welding part 2. The structure is such that the angle of incidence can be changed freely. Note that the servo motor 14 and the servo motor 17 are rotationally controlled by the controller 22, and the probe 1
Ultrasonic transmission from the glove 15 is also controlled by the controller 22, and the echo signal received by the glove 15 is transmitted to the controller 2.
It is now sent to 2.

Next, an ultrasonic flaw detection method using the apparatus of this embodiment will be described.

First, the welded part 2 to be inspected and the piping 1 on both its upper and lower sides
The portion is surrounded by overlapping the two divided pieces 4, 4 of the transparent container 3, and the upper and lower parts thereof are fastened and fixed with fixing bands 6. Next, water is poured from the upper opening of the transparent container 3.
Inject the necessary amount of transparent radiation shielding liquid 2 such as glycerin or a high-density aqueous solution such as lead acetate, and place the welded part 2 in the container 3.
A transparent radiation-shielding liquid layer 8 is formed to cover the outside of the piping 1 including. Furthermore, before attaching the transparent container 3 to the piping 1, the piping 1 portions on both the upper and lower sides of the container 3 are shielded with shielding rings 23 made of lead or the like, if necessary.

Next, the transparent container 3 is covered with the two-split rotary table 9 and the bevel gear 11, the rotary table 9 is connected and fixed with the connecting fittings 10, and the bevel gear 12 is meshed with the bevel gear 11 to complete the container 3.
It is rotatably attached to a support stand 13 attached to.

Then, the controller 22 operates the servo motor 17 to set the vertical position and incidence angle of the probe 15 with respect to the welding part 2.

If both the servo motors 17 on the inside of the container 3 and on the side of the container 3 are rotated in the same rotation direction and at the same rotation speed, the horizontal plate 18.18
At the same time, the frame 19 is translated vertically. Further, by rotating either the servo motor 17 inside the container 3 or on the side of the container 3, the angle of inclination of the frame 19 can be changed.

The relationship between the number of rotations of the servo motor 17 and the position of the bin 20, etc. is input to the controller 22 in advance, and
- On the roller 22, the vertical position and incidence angle of the globe 15 are displayed on a vertical position display 24 and an incidence angle display 25, as shown in FIG.

Once the vertical position and angle of incidence of the probe 15 relative to the welding part 2 are set in this manner, the controller 22 operates the servo motor 14 to rotate the rotary table 9 via the bevel gears 12 and 11.

As the rotary table 9 rotates, the flaw detection probe 15
Rotation scanning is performed along the welding part 2 in the 0 circumferential direction. Under the control of the controller 22, the probe 15 emits ultrasonic waves during this rotational scanning, and the reflected waves from the welding part 2 are input to the controller 22 as electrical signals.
A computer built into 2 analyzes the presence, size, and location of defects and performs ultrasonic flaw detection.

As described above, in the present invention, the pipe 1 including the welded part 2 is covered with the transparent radiation shielding liquid layer 8, and ultrasonic flaw detection is performed by remote control from outside the transparent container 3. Exposure doses can be significantly reduced and worker safety can be improved. Furthermore, for radiation shielding, it is only necessary to cover the pipe 1 with a transparent container 3 and fill the container 3 with the shielding liquid 1. Furthermore, the ultrasonic waves from the probe 15 are transmitted through the shielding liquid to the welded part 2 and the piping in its vicinity. 1, there is no need for surface finishing in the conventional direct contact method, simplifying and speeding up the work.

Furthermore, since the flaw detection probe 15 is provided in the radiation shielding liquid 1, the incident angle of the ultrasonic waves to the flaw detection inspection section can be freely changed, improving flaw detection performance and also being able to be used not only for the piping 1 but also for complex shapes. It can also be applied to inspection objects. Since the inspection part is still covered by the transparent container 3 and the transparent radiation shielding liquid layer, the inspection target part can be visually seen from the outside of the container 3, making it easy to confirm the inspection and speeding up the inspection. Furthermore, as in this embodiment, if the position of the probe 15 (vertical position and rotation angle of one pipe) and angle of incidence are detected by the controller 22, defects in the inspection section can be automatically recorded.・Be able to establish a computer system for analysis.

By the way, nuclear %--1 is a particular problem with atomic couplants.
0- Species include cobalt-60, but cobalt-60
γ-rays of about IMeV are emitted from the The radiation shielding effect is generally expressed by the thickness at which the intensity is halved, that is, the half-value layer, but the half-value layer for gamma rays is approximately 1
2 cm, approximately 9.2 Cn'L for glycerin, and approximately 8 Cn'L for an aqueous solution of a lead compound. Therefore, the thickness of the radiation shielding liquid layer 80 needs to be thick enough to have a partial shielding effect (eg, 10 to 20 cTrL of water).

In addition, in the above embodiment, flaw detection was shown for the welded part 2 of the pipe 1 disposed in the vertical direction, but in the case of flaw detection for the welded part 2 of the pipe 1 disposed in the horizontal direction, FIG. As shown in FIG. 2, the pipe 1 is liquid-tightly covered with a transparent container 3 which is a sealed cylindrical body cut in half in the axial direction, and a servo motor 14 is provided on the upper surface of the container 3. This allows it to move left and right along the rod 27. In the above embodiment, the bevel gears 11, 12, etc. are used to rotate the probe 15 around the pipe 1, but a moving means that can run along the upper edge of the transparent container 3 is provided, and the moving means is equipped with a rod. 16 may be connected.

As is clear from the above description, according to the present invention, the following excellent effects can be exhibited.

(1) By forming a transparent radiation-shielding liquid layer to shield radioactive objects such as atomic couplant piping from radiation, the radiation dose during ultrasonic flaw detection can be significantly reduced, and the radiation dose for workers can be significantly reduced. Safety can be improved.

(2) In addition, a shielding liquid layer can be easily formed by enclosing the object to be inspected, including the inspection part, in a transparent container and injecting and filling the transparent container with a transparent radiation shielding liquid, and there is no need to finish the surface of the object to be inspected. This makes flaw detection work simple and quick. It is still possible to shorten the flaw detection inspection period and improve the operating efficiency of atomic couplants, etc.

(3) Since the ultrasonic flaw detection probe is installed in the shielding liquid layer, the angle of incidence of the ultrasonic waves from the probe on the object to be inspected can be changed freely, improving the flaw detection performance, and the object to be inspected has a complex shape. Flaw detection can also be easily performed.

(4) Since the inspection part is visible from the outside of the transparent container, it is easy to confirm the inspection contents and the inspection can be carried out quickly.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing one embodiment of the device according to the present invention, FIG. 2 is a plan view of the same, FIG. 3 is a perspective view showing divided pieces of a transparent container of the device, and FIG. 4 is the same as the one shown in FIG. FIG. 5 is a plan view of the frame having the ultrasonic flaw detection glove shown in FIG. 4, FIG. 6 is a front view of the operating section of the controller, and FIG. 7 shows another embodiment of the present invention. FIG. In the figure, 1 is piping (tested object), 2 is welded part (inspection part),
3 is a transparent container, 4 is a divided piece of the transparent container, 6 is a fixing band, 8 is a transparent radiation shielding liquid layer, 9 is a rotary table, 11.12 is a bevel gear, 14.17 is a servo motor, 15 is an ultrasonic flaw detection 16 is a rod, and 22 is a controller. Patent Applicant Ishikawajima Harima Heavy Industries Co., Ltd. Representative Patent Attorney Nobuo Kinutani Figure 1 Figure 6 4 25 Figure 7 311

Claims (1)

[Claims] 1. In a method for ultrasonic flaw detection of a radioactive inspection object such as atomic couplant piping, a transparent radiation-shielding liquid layer is formed outside the inspection section of the inspection object, and the shielding liquid layer An ultrasonic flaw detection method characterized by immersing an ultrasonic flaw detection probe inside the glove and scanning the outside of the inspection part with the glove. 2. In an apparatus for ultrasonic flaw detection of radioactive test objects such as atomic couplant piping, there is a transparent container surrounding the test section of the test object, and the test object including the test section is placed inside the transparent container. An ultrasonic flaw detection device comprising a transparent radiation shielding liquid layer filled and formed to shield radiation, an ultrasonic flaw detection glove provided in the shielding liquid layer, and a scanning means for scanning the probe. .