JPH08292177A - Flaw detection device - Google Patents

Abstract

PURPOSE: To obtain a flaw detection device capable of enhancing the accuracy of detection of a flaw. CONSTITUTION: A flaw detection device 3 is inserted into a heat-transmitting pipe 15 to be heated and both of copper mirrors of a laser heater 4 are provided in opposition to a position to be subjected to flaw detection. Next, a laser light emitted from a laser source 5 is emitted to the both of the mirrors and the laser reflected thereby is emitted by nipping a crack 17 to form two laser- emitted regions. At that time, an inner wall 15a of the heat-transmitting pipe is heated and a compressing stress is generated on the inner wall of the heat- transmitting pipe 15 at the both of laser-emitted regions. A tensile stress is generated on the outer face of the heat-transmitting pipe 15, then it is expanded as a whole. Therefore, the tensile stress which is not so inclined and roughly constant is generated in a lengthwise direction on the inner wall in both of the laser-emitted regions of the heat-transmitting pipe 15 so that the crack is opened. After that, the flaw detection device is lowered and an ultrasonic sensor 3 (ultrasonic flaw detection probe) is opposed to the crack, thereby executing the flaw detection of the crack 17 by using the ultrasonic wave from the ultrasonic wave sensor 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flaw detection apparatus for inspecting cracks existing along the circumferential direction on the outer peripheral portion of a pipe, for example, a heat transfer pipe of a steam generator of a pressurized water reactor (PWR). .

[0002]

2. Description of the Related Art FIGS. 5A and 5B show a conventional mirror rotation type ultrasonic flaw detection probe. This mirror rotation type ultrasonic flaw detection probe is inserted into a heat transfer tube (refer to 15 in FIG. 1 and FIG. 4), and the ultrasonic wave oscillated from the ultrasonic sensor 3 at the height position of the flaw detection portion is reflected by the mirror 2 and To the heat transfer tube to scan for cracks existing along the circumferential direction on the outer circumference of the heat transfer tube. The flaw detection area in the circumferential direction is covered by rotating the mirror 2.

In this mirror rotation type ultrasonic flaw detection probe, a mirror 2 and a mirror rotation motor 1 for rotating the mirror 2 are installed. A water seal 9 is provided below the ultrasonic flaw detection probe, and water is stored on the upper surface of the water seal 9. In addition, 8 is a stabilizer and 10 is a guide cylinder.

[0004]

[Problems to be Solved by the Invention] Pressurized water reactor (PW)
In the flaw detector for inspecting the heat transfer tube of the steam generator of R) for cracks, it is necessary to improve the precision of flaw detection detectability. The ultrasonic flaw detection probe has a limit in improving the precision of flaw detection detectability.

The present invention is proposed in view of the above problems, and an object thereof is to provide a flaw detection device capable of improving the precision of flaw detection detectability.

[0006]

In order to achieve the above-mentioned object, the present invention provides a flaw detector for inspecting cracks generated along the circumferential direction on the outer peripheral portion of a pipe, and The heating mechanism includes a heating mechanism for heating and generating tensile stress in the longitudinal direction of the pipe to open a crack, and an ultrasonic flaw detector for irradiating the crack with ultrasonic waves.

[0007]

The flaw detector of the present invention is configured as described above, and the flaw detector is inserted into the heat transfer tube and raised, and the heating mechanism is opposed to the flaw detection point of the heat transfer tube to transfer the laser light. Irradiate the inner wall of the pipe and generate tensile stress in the longitudinal direction of the heat transfer pipe where the crack has occurred to open the crack, enhance the divergence and diffraction of ultrasonic waves at the crack tip, and enhance the reflectivity of the crack surface. After that, the flaw detector is lowered, the ultrasonic flaw detector is made to face the crack, and the flaw is detected by ultrasonic waves.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the flaw detector of the present invention will be described with reference to an embodiment shown in FIGS. 1 to 4. In FIG. 1, 1 is a mirror rotation motor, 2 is a mirror rotation motor 1, and 3 is a mirror rotation motor. Ultrasonic sensor (ultrasonic flaw detector), 4 is a laser heater,
Reference numeral 5 is a laser source for generating a laser beam 13 which will be described later, 6 is an ultrasonic device for generating ultrasonic waves, 7 is a controller, 8 is a stabilizer, 9 is a water seal, and 10 is a guiding cylinder.

2 and 3, 11 is a copper mirror of the laser heater 4, 12 is a laser fiber, 13 is a laser beam from the laser source 5, and 14 is a divergence angle of the laser beam 13. Has a copper mirror 11 and a laser fiber 12, and the heating mechanism is composed of a laser heater 4 and a laser source 5. 2 and 3, 15 is a heat transfer tube, 15a is an inner wall of the heat transfer tube 15, and 16 of FIG. 4 is a heat transfer tube inner wall 15a.
Laser irradiation area 17 is a crack generated in the outer peripheral portion of the heat transfer tube 15 along the circumferential direction, and the copper mirror 1 of the laser heater 4 is
One and one laser fiber 12 and one laser fiber 12 are installed at the symmetrical positions 180 ° apart from each other in the guiding cylinder 10 below the water seal 9.

Next, the operation of the flaw detector shown in FIGS. 1 to 4 will be specifically described. The flaw detector is inserted into the heat transfer tube 15 and raised to make both copper mirrors 11 of the laser heater 4 face the flaw detection portion of the heat transfer tube 15, and then the laser light 13 generated by the laser source 5 is passed through both laser fibers 12. Irradiate both copper mirrors 11 with a divergence angle 14 of ± 12 °. At that time, the laser fiber 12 and the copper mirror 11 are separated from each other by about 24 mm, and the irradiation area on the copper mirror 11 is a circle having a diameter of about 10 mm (see FIG. 3).

Both copper mirrors 11 are tilted at 45 ° with respect to the optical axis, and the laser light 13 reflected from the copper mirrors 6 is 6
The heat transfer tube inner wall 15a separated by about mm is irradiated with the crack 17 sandwiched therebetween to form two laser irradiation areas 16 (see FIG. 4). At this time, the heat transfer tube inner surface wall 15a is heated, and in both laser irradiation regions 16, compressive stress is generated on the heat transfer tube 15 inner surface and tensile stress is generated on the heat transfer tube 15 outer surface, resulting in a so-called bending stress distribution. However, since it expands as a whole, the inner surface wall 15a of the heat transfer tube 15 between both laser irradiation regions 16 has
A substantially uniform tensile stress with little slope is generated in the longitudinal direction of the pipe.

In the calculation example, when the tube inner diameter is about 20 mm and the tube wall thickness is about 1 mm, 240,000 kal / in both laser irradiation areas 16.
When a heat flow rate of m ² h ° C is applied for about 10 seconds, the temperature of the inner surface of the heat transfer tube 15 rises to about 400 ° C, which is not a material problem, and at the center between both laser irradiation areas 16, the heat transfer tube 15
A tensile stress of 200 MPa or more is generated on the outer surface in the pipe longitudinal direction. The temperature of the 17th crack is about 200 ° C. The tensile stress of 200 MPa is much larger than the assumed bending stress amplitude of the heat transfer tube 15 in service, and cracks 1
This is a value sufficient to plastically open No. 7.

Thereafter, the flaw detector is lowered, the ultrasonic sensor (ultrasonic flaw detector) 3 is made to face the crack 17, and the crack 17 is flaw-detected by the ultrasonic wave from the ultrasonic sensor 3.
Thus, the crack 17 generated in the heat transfer tube 15 is opened to perform flaw detection, but the opened crack 17 has higher divergence / diffraction of ultrasonic waves at the crack tip than the crack 17 before opening, The reflectivity of the surface of the crack 17 is enhanced.

[0014]

As described above, the flaw detector according to the present invention inserts the flaw detector into the heat transfer tube and raises it so that the heating mechanism faces the flaw detection portion of the heat transfer tube and the laser beam is directed to the inner wall of the heat transfer tube. Irradiate, generate tensile stress in the tube longitudinal direction in the heat transfer tube part where the crack has occurred, open the crack, enhance the divergence and diffraction of ultrasonic waves at the crack tip, and enhance the reflectivity of the crack surface, Since the flaw detector is lowered, the ultrasonic flaw detector is made to face the crack, and the flaw is detected by ultrasonic waves, the precision of flaw detection detectability can be improved.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional side view showing an embodiment of a flaw detection device of the present invention.

FIG. 2 is a vertical sectional side view showing a heating mechanism of the flaw detection apparatus.

FIG. 3 is an operation explanatory view of a heating mechanism of the flaw detection apparatus.

FIG. 4 is a side view showing an irradiation area (heating area) of the heating mechanism.

FIG. 5A is a side view showing a conventional flaw detector, and FIG.
Is a vertical side view.

[Explanation of symbols]

 1 Mirror Rotation Motor 2 Mirror 3 Ultrasonic Sensor (Ultrasonic Flaw Detector) 4 Laser Heater (Heating Mechanism) 5 Laser Source 6 Ultrasonic Device 7 Controller 11 Copper Mirror of Laser Heater 4 12 Laser Fiber of Laser Heater 4 15 Heat transfer tube 16 Irradiation area (heating area) of laser heater 4 17 Crack of heat transfer tube 15

Claims (1)

[Claims] 1. A flaw detection device for inspecting a crack generated along the circumferential direction at the outer peripheral portion of a pipe, wherein the cracked pipe portion is heated to generate tensile stress in the longitudinal direction of the pipe to open the crack. A flaw detection device comprising a heating mechanism and an ultrasonic flaw detector that radiates ultrasonic waves to the crack.