JPH05209864A - Ultrasonic flaw detector - Google Patents

Abstract

PURPOSE:To improve reliability of inspection by a method wherein a flaw detector is compressed when it is inserted into a hollow frustum of cone and opens until it is extended against an inner face of the structure by remote control in the vicinity of the bottom. CONSTITUTION:A slider 18 provided on a pole 8 is positioned downward when it is inserted from a top opening of a structure, while a movable arm 16 and a rim 17 stay hung downward. After the insertion, the slider 18 is pulled up by pulling up a rope 19 so that the arm 16 coupled to it is pulled up to be extended against an inner face of the structure. That is, a rotation center axis of a probe 14 and an axis of the structure are made to match each other, so that distances from the probes 14 to structure bottom welded portions 6, 7 can be kept constant. Ultrasonic waves generated from the probes 14 propagate in the water to be incident from inside the structure. One of the probes 14 is a normal type which searches for a signal from cracking or the like produced at the welded portions 6, 7 or their vicinity while the other is a high frequency probe which searches for a noise signal from the welded portions 6, 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention remotely controls a circumferential welded portion (hereinafter referred to as a jet pump diffuser bottom welded portion) near the bottom portion of a jet pump diffuser mounted inside a boiling water reactor pressure vessel, for example. Relates to a device for automatically performing ultrasonic flaw detection.

[0002]

2. Description of the Related Art Conventionally, inspection is performed from the outside of a structure by an underwater television camera, and not by an ultrasonic flaw detector.

[0003]

In the above-mentioned prior art, even if a defect such as a crack has occurred in the welded portion and its vicinity, it cannot be detected unless it is opened to the outside. In order to detect defects that are not opened to the outside and improve the reliability of the inspection, it is necessary to enable ultrasonic flaw detection, which is known to be able to detect defects inside the metal. There are a method of injecting ultrasonic waves from the outside of the structure and a method of injecting ultrasonic waves from the inside thereof. The present invention relates to a method of injecting ultrasonic waves from the inside to inspect.

When an ultrasonic wave is incident from the inside of the structure for inspection, it is necessary to dispose a probe inside the structure and drive it in the circumferential and vertical directions. Further, during the driving operation, in order to keep the distance between the probe and the welded portion uniform, the center axis of rotation of the probe and the axis of the structure are aligned, and the probe is driven. It is necessary to prevent runout. By providing a guide that fits in the opening at the top of the structure, it is possible to easily support the weight of the device to be inserted inside, attach the vertical drive mechanism, and align the axis in the opening. However, near the bottom of the inspection object, the distance from the top is more than ten times the inner diameter of the opening, and the inner diameter is larger than the inner diameter of the opening. There is a difficulty in rating.

An object of the present invention is to inject an ultrasonic wave from the inside of a hollow truncated cone structure, inspect a circumferential weld near the bottom, and detect defects such as cracks that have not been opened to the outside. It is to provide an apparatus for improving the reliability of inspection.

[0006]

Among the above-mentioned problems, regarding the axial alignment and the steady rest, in the device to be inserted inside the structure, at the time of inserting from the top opening, the shrinkage is made to fit into the opening. In the vicinity of the bottom, by remote control before the start of inspection, it is opened until it is in a tensioned state with the inner surface of the structure, and the rotation center axis of the probe and the axis of the conical structure are matched, The problem can be solved by applying a supporting mechanism having a structure capable of ensuring the function of a steady rest accompanying the drive of the probe.

On the other hand, it is known that when ultrasonic waves are incident on a welded portion of austenitic stainless steel using a high frequency probe, a myriad of noise signals are detected from within the weld metal. Therefore, the position of the welded portion can be evaluated by driving the high frequency probe to detect whether or not the noise signal is detected.

[0008]

According to the present invention, in the vicinity of the bottom portion of the structure, before the flaw detection operation, the center axis of rotation of the probe is aligned with the axis of the structure, and the probe is driven. A supporting mechanism having an accompanying steady rest function can be set. Therefore, it is possible to maintain a constant distance between the probe and the welded portion, prevent a shake due to driving of the probe, and perform an appropriate inspection. still,
Since the welding position can be evaluated from the presence or absence of a noise signal by driving the high-frequency probe, it is possible to accurately evaluate the relative relationship between the defect position and the welding position.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 2 is a sectional view of a pressure vessel and a jet pump diffuser of a boiling water reactor.

The jet pump mixer 2 and the jet pump diffuser 3 are connected to the pressure vessel 1 as shown on the left side of FIG.
Assembled underneath. Of these, the jet pump diffuser 3 has a hollow truncated cone structure as shown on the right side of the figure. A lower ring 4 is welded to a bottom portion of the jet pump diffuser 3 via a welded portion 5. The lower ring 4 is welded to the baffle plate 5 via the welded portion 6.

When the welds 6 and 7 near the bottom of the hollow truncated cone structure are inspected, since the inside of the pressure vessel 1 is filled with reactor water, according to the prior art, the water is injected from the outside of the structure. I was inspecting with a TV camera. However, even if a defect such as a crack has occurred in the welded portion and the vicinity thereof, it cannot be detected unless it is opened to the outside.
To improve the reliability of this inspection, an ultrasonic flaw detection that can detect even unopened defects is adopted. The ultrasonic flaw detection method employs a method in which the jet pump mixer is removed, the probe is placed inside the jet pump diffuser, and ultrasonic waves are incident from the inner surface side of the welded portion.

FIG. 1 shows a cross section of an ultrasonic flaw detector.

A pole 8 penetrates the center axis of a guide 9 fitted in the top opening of the structure, and the tip of the pole 8 has a probe holder 13, a circumferential drive mechanism 11 and the like, a movable arm 16 and the like. The support mechanism of is attached.

A vertical drive mechanism 10 incorporating an electric motor is attached to the guide 9. A rack is cut in a range where the pole 8 is meshed with the vertical drive mechanism 10 so that the pole 8 can move up and down.

The guide 9 and the probe holder 13 are preassembled so that the dimensions from the top of the structure to the welds 6 and 7 are approximately the same. The circumferential drive mechanism 11 has a built-in electric motor, and can rotate the shaft 12 and the probe holder 13 connected thereto in the circumferential direction.

A fastener 15 is fixed to the circumferential drive mechanism 11, and a movable arm 16 attached to the fastener 15 and a slider 18 attached to the pole 8 are connected by a rim 17. The slider 18 is slidable in the vertical direction, and is below when the structure 18 is inserted from the top opening of the structure.
6 and the rim 17 are in a state of hanging downward. That is,
Even if these are attached to the tips of the poles 8, they do not interfere with each other when they are inserted from the top opening of the structure. on the other hand,
After the insertion, when the rope 19 is pulled up, the slider 18 is pulled up, and the movable arm 16 connected to this is pulled up to be in a tensioned state with the inner surface of the structure. That is,
The rotational center axis of the probe and the axial center of the structure are made to coincide with each other, and shake due to the drive of the probe is prevented, and during the drive operation,
The distance between the probe and the weld can be kept constant at all times. In addition, when removing these after the inspection, the rope 19 is loosened and the pole 8 is pulled upward, so that the movable arm 16
The rim 17 hangs downward and can be pulled out from the top opening of the structure without trouble.

A probe 14 is attached to the probe holder 13 and is connected to an ultrasonic flaw detector 21. One of the two illustrated probes 14 is a defect inspection probe, and the other is a high frequency probe (5 to 10 MHz). The ultrasonic waves transmitted from the probe 14 propagate in water and enter from the inside of the hollow truncated cone structure. The high frequency probe detects a noise signal from the welded portion, and the defect inspection probe detects a signal from a defect such as a crack generated in the welded portion or in the vicinity thereof.

The controller 20, the ultrasonic flaw detector 21, and the recorder 22 are arranged outside the furnace. The vertical drive mechanism 10 and the circumferential drive mechanism 11 operate and stop according to commands from outside the furnace of the controller 20, and scan the probe 14 in a predetermined range. The recorder 22 is an ultrasonic flaw detector 21.
The ultrasonic signals emitted and received by the probe 14 and the operating position signals transmitted from the vertical drive mechanism 10 and the circumferential drive mechanism 11 are processed and recorded as inspection data.

[0020]

EFFECTS OF THE INVENTION According to the present invention, ultrasonic waves are incident from the inside of the hollow truncated cone structure, the circumferential welded portion near the bottom is inspected, and defects such as cracks that have not been opened to the outside can be detected. Becomes Further, by providing the high frequency probe together with the defect inspection probe, the position of the welded portion can be detected and the relative relationship between the defect position and the welded portion position can be accurately evaluated.

[Brief description of drawings]

FIG. 1 is a block diagram of an ultrasonic flaw detector for a jet pump diffuser bottom welded portion according to an embodiment of the present invention.

FIG. 2 is a sectional view of a hollow truncated cone structure of a jet pump diffuser.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Pressure vessel, 2 ... Jet pump mixer, 3 ... Jet pump diffuser, 4 ... Lower ring, 5 ... Baffle plate, 6, 7 ... Welding section, 8 ... Pole, 9 ... Guide, 10 ... Vertical drive mechanism, 11 ... Circumferential drive mechanism,
12 ... Shaft, 13 ... Probe holder, 14 ... Probe, 15 ...
Fasteners, 16 ... Movable arm, 17 ... Rim, 18 ... Slider, 19 ... Rope, 20 ... Controller, 21 ... Ultrasonic flaw detector, 22 ... Recorder.

Claims (3)

[Claims] 1. A device for ultrasonically inspecting a circumferential welded portion near the bottom of a hollow truncated cone structure that is submerged in water by remote control, wherein the hollow truncated cone structure is opened from the opening to the hollow part. Ultrasonic flaw detection characterized by inserting a probe, a probe driving mechanism and a mechanism for supporting them inside the truncated cone structure and injecting ultrasonic waves from the inner surface side of the welded portion for inspection. apparatus. 2. The function according to claim 1, which has a function of aligning a central axis of rotation of the probe with an axis of a conical structure, and a function of precession accompanying driving of the probe, An ultrasonic flaw detector, which is contracted to a size that can be inserted through the opening at the time of insertion from the opening, and is capable of ensuring the function by remote control before the flaw detection operation. 3. An ultrasonic flaw detector according to claim 1, comprising a normal type probe and a high frequency type probe, wherein the high frequency type probe detects the position of a welded portion.