JPS63315943A - Ultrasonic flaw detector for plate spring - Google Patents

Abstract

PURPOSE:To simultaneously execute a single probe method and a two-probe method, to make up each other even a defect which cannot be detected by one flaw detecting method, by both the methods, and also, to reduce the rate for overlooking the defect by a scan of once. CONSTITUTION:An ultrasonic probe 1 is a transmitter-receiver whose vibrator diameter is a small aperture and whose directional characteristic is narrow, and an ultrasonic probe 2 is a receiver whose aperture is large and whose directional characteristic is wide. These probes, 1, 2 are supported so as to be opposed at an incident angle of 15-25 deg. to the side face of each plate spring (a)-(c) from the outside of the upper nozzle 10 in a prescribed direction by a scanner 3, without changing each relative position. Subsequently, they are moved as they are along the length direction of the plate spring to the lower part from the upper part of an inclination, shifted upward and downward by a thickness portion of each plate spring, and also, while changing the direction to match an inclination angle of each plate, a scan is executed repeatedly by a piece number portion of the plate spring.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present study relates to a T11 sonic flaw detection device for leaf springs, more specifically, it is installed at the top of the upper nozzle of a fuel assembly for a pressurized water reactor to detect coolant flow. This invention relates to a device that performs deep ultrasonic waves under water by remote control, with several leaf springs constituting a pressed left spring for preventing the fuel assembly from surfacing in the water while still attached to the upper nozzle. .

[Conventional technology]

At the top of the upper nozzle of the fuel assembly for pressurized water reactors, there is a hold gouge pointing downward against the upper core plate to prevent the fuel assembly from floating due to the flow of coolant flowing from below upwards. A stack of two or three leaf springs is attached as a pressure spring to apply the knock. Inspection of this compressed spring is carried out using an underwater drying camera for the loaded fuel, and periodic inspection of the spring force. The reality was that there was a desire to develop a method that would

[Problem that the invention seeks to solve]

The object of the present invention is to be compatible with general working conditions for handling nuclear materials, to be able to perform search operations efficiently by remote control, and to attach pressure springs to the roots of fuel assemblies for pressurized water reactors. To provide an ultrasonic flaw detection device for striking springs that can identify the occurrence of cracks in each leaf spring and reliably detect flaws.

・[Means for solving the problem] According to this research, a presser spring is installed at the top of the upper nozzle of a fuel assembly for a pressurized water reactor to prevent the fuel assembly from floating against the flow of coolant. An apparatus is provided for underwater ultra-A wave flaw detection in which a plurality of leaf springs constituting a stack of leaf springs are attached to the upper nozzle. a first probe with a relatively narrow directional characteristic to enable each plate of the leaf spring to be identified; and a relatively wide directional characteristic arranged substantially parallel to the same directional direction as the first probe. a second probe having a
scanning means that scans each leaf spring in the length direction by directing these door tentacles at a predetermined large pull angle to the side surface of the leaf spring;
The device includes means for supplying a transmission pulse to the first probe, and flaw detection display means for signal processing and displaying echo signals received by the first and second probes.

In a preferred embodiment of the present invention, the scanning means has a drive device for remotely adjusting the angle of incidence of the double door probe; Due to its narrow directivity characteristics, the second probe is in charge of the flaw detection area near both ends of the leaf spring in the width direction, and the second probe is in charge of the flaw detection area in the remaining middle part in the width direction. It has a large-diameter receiving surface, and the Ichikawa display means extracts and displays the received echo signal within the time axis range corresponding to the scratch area, which each one is responsible for, from among the three received signals from these double door touchers. It has a time axis gate circuit.

According to another preferred embodiment of the present invention, the angle of incidence is set within the range of ~25°.

According to yet another embodiment of the present invention, the flaw detection display means has a 282 flaw display that separately displays the results of the first and second probes.

[Effect]

J11 of this investigation? In particular, the flaw detection device detects several stacked leaf springs, which make up the presser spring of the pressurized water reactor fuel fJS combination, underwater by automatically scanning each leaf spring by remote control while still attached to the upper nozzle. Perform ultrasonic flaw detection. The first probe and the second probe are directed at a predetermined angle of incidence onto the collar surface of the leaf spring by a scanning device, and scan each probe in the length direction of the leaf spring. In this case, the first probe has a relatively narrow directivity characteristic in order to make it possible to identify each plate in the stack of several plates, and the first probe has a relatively narrow directivity characteristic to enable identification of each plate in the stack of several plates. A second probe with a relatively wide directivity is placed almost parallel to the first probe in the same pointing direction.
The probe is for reception only, and serves as a receiver for oblique flaw detection using two probes, with the first probe serving as a transmitter.

The ultrasonic pulse incident from the first probe on one side of the leaf spring at a predetermined angle of incidence is refracted into the leaf spring at a refraction angle mainly determined by the incident angle and the material of the temporary spring. Spring-loaded springs return as echoes through scratches such as cracks on the root and reflections on the other side of the leaf spring.The echoes received by the first probe mainly contain the echoes of the first probe. It includes echoes from flaws in the flaw detection area near the leaf spring 11G direction (,,:8), which is determined by the beam width of the directional characteristic. An oblique probe is carried out using a single probe.On the other hand, a range of depth exceeding the number from the surfaces of both sides of the leaf spring, that is, both sides of the temporary spring,
) Echoes from the width in the remaining intermediate area other than the flaw detection area near j4 are similarly reflected by the other side surface of the leaf spring r! and then received by the second probe. In order to capture echoes from this intermediate region, the second probe has a correspondingly relatively wide directivity characteristic. The conditions for forming a continuous deep easy region over the entire width in the width direction of the leaf spring are the beam width of the directional characteristics of both probes, the distance between the probes, the first width dimension of the leaf, and the incident It can be defined geometrically, such as by corners.

In a preferred embodiment of the invention, the scanning means has a drive for remotely adjusting the angle of incidence of both probes, so that the angle of refraction is preferably 45''. The angle should be adjusted to 15 to 25 degrees.The presser spring of the upper nozzle of a fuel assembly for a pressurized water reactor is generally composed of a flat spring with a parallel width.
The transmitting direction and the receiving direction can be made parallel by 5 degrees, and both probes are fixedly arranged in parallel to simplify relative direction adjustment.

As mentioned above, the first probe is in charge of the detection area near both ends of the leaf spring in the width direction due to its narrow directivity, and the second probe is in charge of the detection area in the middle part of the leaf spring in the width direction. For this purpose, the second probe preferably has a receiving surface with a larger diameter than the first probe.1 The display means amplifies and detects the received echo signal output from the double door touch. Then, synchronization with the transmitted wave pulse (based on No. 3, the time axis game I circuit detects received echoes within the time fill range corresponding to the respective flaw detection areas from among the received signals from both the first contactors) The signal is extracted, and the echo signals received by the first and second probes are displayed separately on the same screen using, for example, a two-way image display device that divides the screen into upper and lower sections.

In order to further clarify the features and advantages of the present invention, preferred embodiments of the present invention will be described below with reference to the drawings.

〔Example〕

Fig. 1 is a plan view showing the center and bottom parts of an ultrasonic flaw detection device according to an embodiment of the present invention placed opposite to the upper nozzle of a fuel assembly for a pressurized water reactor, and Fig. 2 is the same (a side view thereof). be.

The upper nozzle 10 is pressed by springs 11A, I In, and I IC on its top four sides A, B, C, and D, respectively.

As shown in Figure 2, each presser spring is a three-layer temporary structure with a width of 19 mm and a thickness of about 3,9 + nm, each with its base bent at its root and supported cantilevered in the shape of an incline. Consists of springs a, b, and c.

The main target of the 17 islands is defects (cracks) that occur at the bending part X of the root of each leaf spring, and it also includes the detection point of which leaf spring has the crack. There are six types of plates f and l in each fuel assembly, a total of 12 plates, and cracks can occur in any of them, and the size is usually about 0.20111.

In this embodiment, as shown in FIG. 2, the limited range Y extending about 40+ nm at the lower part of the slope including the root X is the scanning range of 17 scratches.

The first tI3 probe 1 is a transmitter/receiver with a small diameter transducer having a diameter of 1/4 (approximately 6.35 mm) and narrow directivity characteristics, and the second ultrasonic probe 2 is a large-diameter receiver with a transducer diameter of 374 inches (approximately 19 In+++) and a wide directional characteristic. These probes 1 and 2 are oriented in a predetermined direction by the scanner 3 without changing their relative positions, that is, parallel to each other, from the outside of the upper nozzle 10 to the side surfaces of the plates a, b, and c. While supported so that they face each other at an incident angle of 25°, move them along the length of the leaf spring from the top to the bottom of the slope, and shift this up and down by the thickness of each leaf spring. , and scanning is performed by repeating as many times as the number of leaf springs while changing the direction according to the inclination angle of each leaf spring.

For this reason, the scanner 3 has a positioning fixation (not shown) to the upper nozzle/L, as well as scanning direction adjustment! ! It has a mechanism and a probe direction adjustment mechanism, and the scanning direction and mounting direction of one of the probes can be adjusted remotely.

Incidentally, as shown in FIG. 1, similar combinations of probes and scanners may be added to perform simultaneous scanning to improve inspection efficiency.

What is shown as block 4 in FIG. 1 is an ultrasonic transmitting/receiving unit, and an example of its detailed configuration is shown in FIG.

In FIG. 1, the ultrasonic transmitter/receiver unit 4 includes a synchronization control circuit 46 and a transmission pulse generation time? 847, the drive pulse synchronized with the synchronous pano L from the synchronous control circuit 46 and the first
The probe 1 is supplied with ultrasonic wave transmitting light, and the ultrasonic wave transmitting light is emitted from the probe 1. Unit 4 is also equipped with a signal processing circuit for receiving echo signals from each probe.
This includes a reception amplifier circuit 141, a detection circuit 142, a time width gate circuit 143, and a video amplifier circuit 144 for the first probe l, and for the second probe 2. , a reception amplifier circuit 241, a detection circuit 242, a time width gate 1 circuit 243, and a video amplifier circuit 244.

Unit 4 further includes these video amplifier circuits, 144, 24.
The display device 45 has a video image 1↑ display device 45 for displaying video outputs of 4 video outputs, and this display device 45 has 2 p-divided surfaces for separately displaying video signals from each video amplifier circuit. The configuration of such a unit 4 itself is basically the same as the conventional one, but in this case, the time width gate circuit #1
43.243 sets the gate starting point and gate time range after a predetermined period of time has elapsed from immediately after the transmission pulse using a synchronization signal from the synchronization control circuit 46 in order to extract only the echoes from the respective flaw detection areas of the probes 1 and 2. Two locations are set for each.

FIG. 4 shows the positional relationship between the temporary spring a of the presser spring and the probe 1.degree. 2, viewed from the top of the spring. In the figure, 12 is a screw hole for temporarily fixing the spring. The object to be measured is in water and the probes 1, 2 are also submerged in water, so in this case the ultrasonic propagation medium between the object to be measured and the probe is water.

Select the leaf spring to be tested first from among the three leaf springs, adjust the height of the probe to the leaf spring when the spring is 40m+a from the root, and adjust the scanning direction of the scanning device 3 and the detection position.
Remotely adjust the angle of incidence of the tentacle. Thereafter, without transmitting the ultrasonic pulse, the probe is moved to the base of the temporary spring and scanned, and the received echoes are captured by both probes 1 and 2.

If this is done for three temporary springs, the flaw detection for one set of pressed springs is completed, and this is done for four sets of pressed springs.

Now, the ultrasonic huff 1 emitted from the transmitter/receiver A3 retainer 1
♀ on the outer surface of temporary spring II at an incident angle of 15 to 25 degrees.
゛] and is refracted at the boundary between the medium and the leaf spring. In this case, flaw detection with the best sensitivity occurs when the refraction angle is around 45°, and therefore the incident angle is set to 15 to 25°. In FIG. 4, T is a transmission pulse, S is a surface reflected wave, F is a defect echo, and W is an echo from the inner wall of the screw hole 12.

Figure 5 shows that the attachment of the leaf spring corresponds to the scanning position expressed by the distance from the root, and the path of the transmitted wave pulse T and defect echo F is related to the deep flaw area of each probe. This is what was shown. As can be seen from this figure, in the present invention, there is a deep method in which transmission and reception are performed with a single probe 1, and a 17-incision method in which transmission (3) is performed with one probe 1 and reception is performed separately with the other J7 probe 2. As shown in Figure 5 (a) and (e), an area of about 3.4+++a at each end in the width direction of the temporary spring is detected using a single probe method of n''[. Then, as shown in FIG. 5 (b l (d)), by using the latter two-pressing contact method, the remaining intermediate area excluding the area of about 3.0++ ua of the 18 parts is If f175.
In the figure, the route map in (b) is for L-28, and the route map in (d) is for L-611IIi.

In the case of FIG. 5, the display of the time axis gate by the time axis gate circuits 143, 243 of FIG. The ΔEcho 9 display 145 of the flaw detection result by the 10th deep touch 1 at the bottom of the screen of the device 45 shows data Gn and Gc corresponding to FIGS. 5(a) and 5(C), and the 2 probe 2 171 Chi Song A slow 1 display 2
45, the gate indications Gb and Gdrz corresponding to dl in FIG. 5(b) (first square LL+!, respectively),
(or elevation modulation may also be used). Received echoes that appear within the display range of these gates should be identified as defects such as cracks in the base of the leaf spring.

[Efficacy of invention]

According to the present invention, as mentioned above, eco-friendly! Since flaw detection by the l'-probe method and the two-probe method is performed simultaneously and the received echoes of both are displayed on the same screen, defects that cannot be detected with only one method (371 method) can be compensated for by both methods. Since a receiving qI probe with a wide directional characteristic is used, the probability of overlooking defects in a single scan is extremely low.Also, by using a transmitting/receiving 43 probe with a narrow directional characteristic, a set of 3-ply probes is used. Ultrasonic transmission pulses can be selectively applied to individual leaf springs, and individual leaf springs can be identified, so it is possible to determine which leaf spring has a defect.Furthermore, the scanning device can be placed underwater. As long as it is positioned at the upper nozzle/L of the fuel I4 assembly, everything else can be controlled remotely, making it possible to realize an apparatus configuration that satisfies nuclear material handling standards.

[Brief explanation of drawings]

FIG. 1 shows a tester section of an ultrasonic flaw detection device according to an embodiment of the present invention. The upper part of the body [
The second figure is also a side view, and the first figure is a plan view shown from the top.
The figure is a block diagram showing an example of the configuration of an ultrasonic transceiver unit.
Fig. 4 is an explanatory diagram showing the positional relationship between the temporary spring and the probe in the 17 vortex along with the path of the ultrasonic wave, and Fig. 5 shows the attachment of the leaf spring corresponding to the scanning position expressed by E 21 L from the root. FIG. 6 is an explanatory diagram showing the paths of the transmitted wave pulse T and the defect echo F in relation to the flaw detection area assigned to each probe, and FIG. 6 is an explanatory diagram showing an example of the display screen of the display device. 1: First probe, 2: Second j7 probe, 3: Scanning device, 4: Ultrasonic transmitting/receiving unit nod, 10, upper part, nozzle,
11Δ, IIB, IIC, 111): Pressing spring, a
, b, C: leaf spring, 12 varnish screw hole, 141,2
41: Amplification circuit, 142, 242: Detection circuit, 143,
243: Time axis game 1 circuit, 144.244: Video amplifier circuit, 45: 2-video display device, 46:
Synchronous control circuit, 47. Transmission pulse generation circuit.

Claims (1)

[Scope of Claims] 1. A multi-ply leaf spring that is attached to the top of the upper nozzle of a fuel assembly for a pressurized water reactor and constitutes a pressing spring for preventing the fuel assembly from floating against the flow of coolant. This is an apparatus for performing ultrasonic flaw detection underwater while attached to the upper nozzle, the first probe having a relatively narrow directivity characteristic in order to be able to identify each leaf of a stack of several leaf springs. and a second probe with a relatively wide directivity that is arranged substantially parallel to the same direction as the first probe, and both probes are placed on the side surface of the leaf spring at a predetermined angle of incidence. scanning means for scanning each leaf spring in the longitudinal direction by directing them; means for supplying transmission pulses to the first probe; and means for supplying transmission pulses to the first probe; 1. An ultrasonic flaw detection device for a leaf spring, comprising a flaw detection and display means for processing and displaying flaws. 2. The ultrasonic flaw detection apparatus for a leaf spring according to claim 1, wherein the scanning means has a drive device that remotely adjusts the angle of incidence of both probes. 3. The first probe is in charge of the flaw detection area near both ends of the leaf spring in the width direction due to its narrow directivity, and the second probe is in charge of the flaw detection area in the middle part of the remaining width direction. The display means extracts received echo signals within a time axis range corresponding to the flaw detection area that each probe is responsible for from among the received signals from both of the probes. 2. The ultrasonic flaw detection device for a leaf spring according to claim 1, further comprising a time axis gate circuit for displaying a time axis. 4. The ultrasonic flaw detection device for a leaf spring according to claim 1, wherein the incident angle is set within a range of 15 to 25 degrees. 5. The blade spring according to claim 1, wherein the flaw detection display means has a two-phenomenon display that separately displays echo signals received by the first and second probes. Sonic flaw detection equipment.