JPH0119094B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasonic flaw detection method for a nozzle portion of a nuclear reactor pressure vessel, etc., and particularly to an ultrasonic flaw detection method for a nozzle portion suitable for performing flaw detection from a saddle-shaped portion on the outer surface of the nozzle.

Conventionally, there are the following three methods of ultrasonic flaw detection from the outer surface of the nozzle corner of a reactor pressure vessel.

(1) Flaw detection from the pressure vessel side (2) Flaw detection from the flat surface of the nozzle reinforcement part (3) Flaw detection from the saddle-shaped part on the outer surface of the nozzle However, regarding (1) and (2) above, (i) The flaw detection distance is long and the sensitivity is poor.

(ii) The angle between the defect surface and the ultrasonic beam becomes an acute angle, resulting in poor reflection efficiency.

(iii) It is difficult to inject the ultrasonic beam into the saddle-shaped portion on the outer surface of the nozzle.

(iv) Inefficient due to unidirectional flaw detection There were other drawbacks.

Regarding (3) above, (i) the position of the defect is determined from the position of the probe in the nozzle axis direction, the angle of incidence, the path length, etc., and the accuracy is low.

(ii) Inefficient due to unidirectional flaw detection.

There were other drawbacks.

The present invention has been made for the purpose of improving the above-mentioned drawbacks, and it is an object of the present invention to provide a flaw detection method for a nozzle portion that improves defect positioning accuracy and efficiency with respect to flaw detection from the saddle-shaped portion on the outer surface of the nozzle. .

The method of the present invention provides a method for forming an outer saddle-shaped part of a nozzle in which the radius of curvature R of the outer surface of the saddle-shaped part of the nozzle and the distance F between the nozzle axis and the center of curvature of the outer surface of the saddle-shaped part of the nozzle are known. Rotate the ultrasonic probe of an ultrasonic flaw detection device with a known refraction angle θ to the normal to the ultrasonic beam, which is determined by the settings of the ultrasonic probe shoe, around the center of curvature along the surface. An ultrasonic beam is scanned so as to intersect the inner surface of the nozzle, a reflected beam from a reflection source in the nozzle material is received, and the received data is processed by a processing device of the ultrasonic flaw detection device to at least In an ultrasonic flaw detection method in which a distance T between an ultrasonic wave incidence point and a reflection point is calculated and the position of the reflection source is displayed on a display device, a saddle-shaped portion of the nozzle of the ultrasonic probe is provided. An angle φ of rotation along the curved surface of the outer surface is detected by a rotation angle detection mechanism, and the detected angle φ and each of the known data R, F, θ, T are set in the processing device, and the coordinate system is set as the coordinate system. With the axial direction of the nozzle being X, the radial direction of the nozzle including the ultrasonic beam incident point being Y, and the radial direction of the nozzle orthogonal to the Y direction being Z, the processing device:
The coordinate position [X, Y] of the reflection source on the cross-sectional diagram is defined as [(Rsinφ+Tcosθ・sinφ), (F−Rcosθ−
The processing device calculates the coordinate position [Z, Y] of the reflection source on the side view as [(Tsinφ), (F−Rcosθ−Tcosθ・
cos φ)], and then displays the coordinate position obtained by the calculation on the display device as the coordinates of the reflection source. According to the method, even if the ultrasonic beam is incident in a direction tilted in a three-dimensional direction from the ultrasonic beam incidence point and made as perpendicular to the reflection source as possible, the coordinate position on the cross-sectional view and the coordinate position on the side view are different. By determining this, the three-dimensional position of the reflection source can be determined.

FIG. 1 shows an explanation of the ultrasonic flaw detection method for a nozzle portion of the present invention.

Reference numeral 1 denotes a body including a nozzle portion of a reactor pressure vessel, etc., and 2 a nozzle, which is welded to the pressure vessel body 1. 3 is an ultrasonic probe installed on the curved surface of the saddle-shaped portion on the outer surface of the nozzle.

Now, as a coordinate system, if we take the axial direction of the nozzle as X, the radial direction as Y and Z, and take the center of curvature N of one of the saddle-shaped parts of the nozzle outer surface on the Y axis, the angle φ between them is the ultrasonic wave. This is the rotation angle of the probe.

The ultrasonic probe 3 injects an ultrasonic beam at point P, and its direction is a direction that includes the three-dimensional element shown in FIG.

In FIG. 2, is the normal line, and the angle θ between and is the refraction of the ultrasound wave in the subject.

Therefore, if there is an ultrasonic reflection source at point U, it will be at position Q in the cross-sectional view, and
It is displayed at the W position in the side view.

This relationship is shown below.

The given numerical values include F, R, φ, θ, and T.

F: Distance between the nozzle axis and the center of curvature of the saddle-shaped portion on the outer surface of the nozzle, which is given for each nozzle.

R: Radius of curvature of the nozzle saddle, given for each nozzle.

φ: An angle at which the ultrasonic probe rotates along the curved surface of the saddle-shaped portion on the outer surface of the nozzle, and is detected by a rotation angle detection mechanism.

θ: refraction angle with respect to the normal of the ultrasound beam,
Determined by selection of ultrasound probe.

T: distance between the ultrasound incident point P and the reflection source U,
The round-trip propagation time of the ultrasonic wave is t, and the sound speed is Vs, Vl.
Then, it is expressed as T=t/2Vs...(1) T=t/2Vl...(2).

Using these values, the reflection source Q on the cross section is (x, y) _Q = [(Rsinφ+Tcosθ・sinφ), (F−
Rcosφ−Tcosθ・cosφ)]……(3) Also, the reflection source W on the side view is (z, y) _W = [(Tsinθ), (F−Rcosφ−Tcosθ
・cosφ)]...(4)

As described above, according to the method of the present invention for determining the positions Q and W of the ultrasonic reflection sources by detecting the rotation angle φ of the ultrasonic probe on the curved surface of the saddle-shaped portion on the outer surface of the nozzle, it is possible to easily and accurately obtain the positions Q and W of the ultrasonic reflection sources. I can do it well.

In Fig. 1, the case where the number of ultrasonic probes 3 is one was explained, but if the case where there are multiple ultrasonic probes is shown, the third
or Fig. 4.

In Figure 3, three ultrasonic probes 3, 4, and 5 are provided independently, and the ultrasonic beam 6 sent out from the ultrasonic probe 3 is sent out from the ultrasonic probe 4 in a counterclockwise direction. This is a case where the ultrasonic beam 7 is set to be directed clockwise. The ultrasound beams are set to move away from each other. However, the beam of the ultrasonic probe 5 is applied vertically.

FIG. 4 shows a case where the ultrasonic probes 3 and 4 are interchanged. In this way, the ultrasound beams 6 and 8 come closer to each other.

As described above, according to the method of installing a plurality of ultrasonic probes of the present invention, flaw detection in two directions, clockwise and counterclockwise, can be performed in one scan, and efficiency can be greatly improved. .

The ultrasonic beam sent out from the probe 5 is thrown on the normal line, but if the bottom surface is not parallel to the incident surface, no bottom echo will return.

Therefore, in Figure 1, the bottom echo can be observed when the rotation angle φ of the ultrasonic probe is 0°, when the ultrasonic wave is injected into the nozzle corner, and when the rotation angle φ is 90°. There are three points in this case.

Therefore, by observing the echoes of the vertically applied ultrasonic beam, it is possible to know whether or not the ultrasonic beam has reached the nozzle corner, which is very effective.

Furthermore, since the nozzle is cylindrical and has a thick wall, a special flaw detection method is required as shown in FIG.

In other words, when a transverse ultrasonic beam is applied so as to cross the inner surface of the nozzle, the
It is also injected into the longitudinal ultrasound beam'.

Therefore, in the present invention, both of these beams are actively used for flaw detection.

Now, as shown in FIG. 6, for example, if the incident angle θi is θi ₁ , the refraction angle θr of the transverse wave S becomes θrs ₁ , and the refraction angle θr of the longitudinal wave L becomes θrl ₁ .

Therefore, when testing the cylindrical part of the nozzle, an ultrasonic beam with a transverse wave S is used, and when testing the body side of the nozzle corner, an ultrasonic beam with a longitudinal wave L is used as shown in Figure 7.
using an ultrasonic beam.

In this way, it becomes possible to perform flaw detection over a wide range from a relatively thin cylindrical part like the nozzle side to a range close to a flat plate like the body side without changing the ultrasonic probe.

Note that the appropriate time to switch from the ultrasonic beam of the transverse wave S to the ultrasonic beam of the longitudinal wave L is when the ultrasonic beam passes through the nozzle corner.

In the present invention, as shown in FIGS. 2 and 3, multiple ultrasound probes are used to send out ultrasound beams in clockwise, vertical, and counterclockwise directions, and the ultrasound beams cross or approach each other. The case where the ultrasonic beam moves further away is shown above, but the number of ultrasonic probes may be increased to 4 or 5, a probe for the body side may be added, or one probe may be Similar effects can be obtained using a type probe.

An example of the configuration of an apparatus for implementing the above-described method of the present invention will be described below.

8 and 9, an annular track 10 is attached to the safe end 11 of the nozzle 2. As shown in FIGS. A drive device 12 is installed on this track 10 so as to be able to run freely around the safe end 11 in the Y direction.
The drive device 12 is equipped with an arm 13 that is movable in the X direction, which is the axial direction of the nozzle 2, by a motor (not shown) within the drive device 12. An adjustment mechanism 14 is attached to the left end of the arm 13 to adjust the height of a rotation center shaft 16 that is the rotation center N of the probes 3, 4, and 5. A rotation center shaft 16 is attached to a frame 21 that projects horizontally from the adjustment mechanism 14. This frame 21 has a motor 1
9 is attached, and the drive pinion 18 of this motor 19 connects to the gear 1 attached to the rotation center shaft 16.
It is intertwined with 7. For this reason, the motor 19
When driven, the rotation center shaft 16 is rotated, and the pressing air cylinder 15 as well as the probes 3, 4,
5 can be rotated in the direction of the arrow φ angle. Further, an encoder 20 is attached to the end of the motor rotation shaft of the motor 19 on the side opposite to the drive pinion 18 as a rotation angle detection mechanism in order to detect the rotation angles of the probes 3, 4, and 5. The rotation center shaft 16 further includes a probe 3,
The upper ends of the pressing air cylinders 15 4 and 5 are fixed, and the pressing air cylinders 15 press the probes 3 , 4 , and 5 against the nozzle 2 . Reference numeral 22 denotes a contact type sensor, whose detection direction is horizontal, and a contact tactile end protrudes from the tip of the frame 21. 30 is an ultrasonic flaw detector that supplies electrical pulses to the probes 3, 4, and 5, amplifies reflected echo signals from defects, etc., and outputs a wave height value 31 and a path value 32 to a data recording device 34. do. A drive control device 33 controls drive in the X, Y, Z, and φ directions, and outputs position signals related to the X, Y, and φ directions to the data recording device 34. Data recording device 34
Then, the trigger signal 35 and the gain correction signal 36 of the ultrasonic flaw detector 30 are sent out to obtain a wave height value of 31 and a path value of 3.
2. Record position signals in the X, Y, and φ directions.
A storage medium 37 stores the flaw detection data recorded by the data recording device 34. 40 is a data processing device which inputs the flaw detection data of the storage medium 37, analyzes and processes it, and outputs various chart data. 41 is a terminal, and data processing device 4
Inputs 0 flaw detection data, analyzes, processes, outputs results, etc. A graphic display 42 displays various charts such as a flaw detection cross-sectional view, a side view, and an evaluation list based on the output contents from the data processing device 40. Reference numeral 43 denotes a hard copy, in which various charts such as a flaw detection cross-sectional view, a side view, and an evaluation list are drawn on paper based on the output contents from the data processing device 40.

FIG. 10 shows flaw detection data in waveforms in such an apparatus. Figure 10 3
5 is a trigger signal 35, which is shown here in the order of 0°, clockwise (CW), and counterclockwise (CCW). 31 and 32 are the peak values of the echo signals A ₁ , A ₂ ,
The travel distance values are expressed as T ₁ and T ₂ . In this way,
Multiple echoes are captured for each ultrasound beam. FIG. 11 is a flowchart of data recording. Reference numeral 51 denotes a gain control for correcting distance amplitude characteristics. Reference numeral 52 denotes data capture, which captures the wave height value, path value, and probe position of the echo signal of each beam. 53 is a locus display, which displays the locus of the probe, and if there is an echo whose distance amplitude characteristic correction exceeds 100%, the brightness is changed and displayed. 54 is data recording, for example, recorded on a floppy disk or the like.
FIG. 12 is a flowchart of data processing. At 60, flaw detection data is input from a floppy disk or the like. At 61, in grouping, input data is grouped for each reflection source. At 62, the grouped data is positioned and converted into coordinates regarding the cross section or side surface of the nozzle. 63,6
4 and 65 output a sectional view, side view, and evaluation list.

According to the present invention, automatic flaw detection is possible from the nozzle saddle section, which has a complicated shape.In particular, when applied to the nozzle section of a nuclear reactor pressure vessel, reliability is improved and the amount of radiation exposure for inspectors is significantly reduced. It is expected that there will be great industrial benefits, such as the ability to reduce the amount of water used and greatly improve efficiency.

[Brief explanation of drawings]

Figures 1a, b and 2 are conceptual explanatory diagrams of the ultrasonic flaw detection method of the nozzle part of the present invention, Figures 3a and b and Figures 4a and b are diagrams showing different embodiments, respectively. 5 to 7 are diagrams showing an example of an ultrasonic flaw detection method using two ultrasonic beams, a transverse wave and a longitudinal wave, and FIG. 8 is an overall view of a flaw detection apparatus that implements the method of the present invention. Figure 9 is a view taken along arrow A-A in Figure 8.
Figure 10 shows flaw detection data in waveforms, Figure 11
The figure is a flowchart of recorded data, and FIG. 12 is a flowchart of data processing. 2... Nozzle, 3-5... Ultrasonic probe, 6-8...
Ultrasonic beam.

Claims (1)

[Scope of Claims] 1. A saddle-shaped portion of a nozzle in which the radius of curvature R of the outer surface of the saddle-shaped portion of the nozzle and the distance F between the axis of the nozzle and the center of curvature of the outer surface of the saddle-shaped portion of the nozzle are known. with the center of curvature as the center of rotation along the outer surface of
The ultrasonic probe of an ultrasonic flaw detection device whose refraction angle θ with respect to the normal to the ultrasonic beam determined by the settings of the ultrasonic probe is known is rotated and scanned so that the ultrasonic beam intersects the inner surface of the nozzle. is incident,
A reflected beam from a reflection source in the nozzle material is received, and the received data is processed by a processing device of the ultrasonic flaw detection device to calculate at least a distance T between an ultrasonic incident point and a reflection point, and the reflection source is In an ultrasonic flaw detection method that performs processing up to displaying the position of the nozzle on a display device, a rotation angle detection mechanism detects an angle φ of rotation along a curved surface of an outer surface of a saddle-shaped portion of the nozzle of the ultrasonic probe. Then, the detection angle φ and the known data R, F, θ, and T are set in the processing device, and the axial direction of the nozzle is set to X as a coordinate system, and the nozzle including the ultrasonic beam incident point is set as a coordinate system. Assuming that the radial direction is Y and the radial direction of the nozzle perpendicular to the Y direction is Z, the processing device converts the coordinate position [X, Y] of the reflection source on the cross-sectional view into [(Rsinφ+
Tcosθ・sinφ), (F−Rcosθ−Tcosθ・cosφ)]
The processing device calculates and calculates the coordinate position [Z, Y] of the reflection source on the side view as [(Tsinφ), (F−Rcosθ−Tcosθ・cosφ)], and then An ultrasonic flaw detection method for a nozzle portion, characterized in that the coordinate position obtained by the calculation is displayed on the display device as a coordinate of a reflection source.