KR102225562B1 - A testing device for nuclear fuel cladding using ultra-sonic wave - Google Patents

Abstract

The present invention relates to an apparatus for inspecting cracks in a nuclear fuel rod cladding using ultrasonic waves, and more particularly, generating ultrasonic waves to inspect whether there are cracks or cavities at the end of the cladding of a metallic material protecting the nuclear fuel rod, and passing through the cladding. The present invention relates to an apparatus for inspecting cracks in nuclear fuel rod cladding using ultrasonic waves to accurately identify the presence and location of defects by analyzing waveforms of ultrasonic waves.
According to the present invention, it is possible to accurately and quickly check defects such as cracks or cavities existing inside by inspecting the nuclear fuel rod cladding in a non-destructive method.

Description

Nuclear fuel rod cladding inspection device using ultrasonic waves{A TESTING DEVICE FOR NUCLEAR FUEL CLADDING USING ULTRA-SONIC WAVE}

The present invention relates to an apparatus for inspecting cracks in a nuclear fuel rod cladding using ultrasonic waves, and more particularly, generating ultrasonic waves to inspect whether there are cracks or cavities at the end of the cladding of a metallic material protecting the nuclear fuel rod, and passing through the cladding. The present invention relates to an apparatus for inspecting cracks in nuclear fuel rod cladding using ultrasonic waves to accurately identify the presence and location of defects by analyzing waveforms of ultrasonic waves.

Nuclear fuel rods containing uranium or plutonium as the main components of the nuclear reactor are used as fuel for the fission reaction, and cylindrical nuclear fuel pellets in small pieces are put inside the cylindrical cladding and injected into the reactor.

The nuclear fuel rod cladding is made of a metal material, and zirconium alloy materials with high transmission efficiency, strong corrosion resistance, and robust properties are widely used.

However, since the nuclear fuel rod cladding is used as the first shielding means to seal radioactive materials generated during the fission process of nuclear fuel from the outside, it is necessary to prevent defects in the cladding. If cracks or cavities occur in the cladding, radioactive material may flow into the primary cooling water system as cracks or cracks open at high temperatures. Therefore, inspection devices have been disclosed to check whether defects occur in the cladding of nuclear fuel rods, including major components of a nuclear reactor.

1 is a view showing a control rod driving device of a nuclear reactor, FIG. 2 is a view provided for explanation of cracking and leakage of a welding part of a control rod driving device of a nuclear reactor, and FIG. 3 is a welding part of a through-tube welding part of a reactor upper head control rod driving device according to the prior art. It is a cross-sectional view showing the structure of a non-destructive inspection device.

As shown in (a) of FIG. 1, the control rod drive mechanism (CRDM) of a nuclear reactor includes a reactor vessel head (RVH) and a plurality of penetration nozzles provided therein. The through pipes of the control rod driving device are installed on the upper head of the reactor through heterogeneous welding, as shown in FIG. 1(b).

And Fig. 3(a) shows a system configuration of a non-destructive inspection device. As shown in (a) of Figure 3, the non-destructive inspection apparatus, LMS (Laser Mirror Scanner) 110, QL (Q-switched diode-pumped solid state laser) 120, QL controller 130, PC 140, an ultrasonic sensor 150 and a sensor system 160.

Due to the nature of the reactor vessel, it is essential to avoid direct human access. To this end, the ultrasonic sensor 150 is brought into contact with the inner surface of the reactor vessel head using the robot arm 170 under the open reactor vessel head as shown in FIG. 3B. In (d) of FIG. 3, a mechanism for the end portion of the robot arm 170 for contacting the ultrasonic sensor 150 to the inner surface of the reactor vessel head is shown in detail.

The ultrasonic sensor 150 can be implemented as an amplifier-integrated PZT sensor having a diameter of 4 mm and a center frequency of 350 kHz. In order to increase the ultrasonic transmission rate, a gel contact medium is used for the protective film of the sensor. The ultrasonic sensor 150 may be implemented in both a contact type sensor type or a short distance non-contact type sensor type.

Meanwhile, as shown in (c) of FIG. 3, the ultrasonic sensor 150 may be replaced with the ultrasonic receiver 180. In this case, it is useful in that the robot arm 170 is not required.

Next, the LMS 110 performs high-speed laser scanning around the heterogeneous welding part. To this end, a Q-switched diode-pumped solid state laser (QL) 120 having a wavelength of hundreds to thousands of nm generates a laser beam pulse for 8 ns under the control of the QL controller 130, and LMS ( 110) scan and irradiate the inner surface of the reactor vessel head with a laser beam at equal intervals. The laser beam irradiated to the scanning grating point generates ultrasonic waves.

The LMS 110 is provided with a pair of laser mirrors including the wavelength of the laser beam as an operating wavelength, and these mirrors are fixed to two orthogonal galvano-motors having a maximum angular velocity of several tens to several hundred rad/s. Each mirror can be rotated ±20 degrees from top to bottom or from left to right.

By synchronizing the movement of the galvano motors with the pulse repetition frequency (PRF) of the QL controller 130, the laser pulse is irradiated once to each grid point. Specifically, as shown in (e) of FIG. 3, the laser beam is irradiated to each point along the scan path in an area having a width LH and a length LV of a predetermined interval Δ.

Ultrasonic waves are generated at each point by the laser beam, and the generated ultrasonic waves are detected by the ultrasonic sensor 150 and signal-processed by the sensor system 160, and then stored in the PC 140 for data acquisition and image processing. do.

However, even in the case of using such a device, it is difficult to perform the inspection in an appropriate manner while changing the structure and position of the distal end of the cladding, and thus there is a problem in that an expensive and complex device must be used several times.

KR 10-1210815 B1 KR 10-2014-0064425 A KR 10-2014-0110140 A

The present invention for solving the above problem is to install a probe that generates ultrasonic waves inside a water tank, allow ultrasonic waves generated from the probe to pass through the distal end of the cladding, and detect and analyze the waveform of ultrasonic waves that have passed through the cladding. An object of the present invention is to provide an apparatus for inspecting cracks in a nuclear fuel rod cladding using ultrasonic waves to check a portion where a peak value appears to check defects present in the cladding.

The present invention conceived to solve the above-described problem is to pass ultrasonic waves to the distal end of the nuclear fuel rod cladding 10 to protect the nuclear fuel rod, and analyze the waveform of the ultrasonic waves passing through the nuclear fuel rod cladding 10 to determine the presence of defects and An inspection device for checking a position, comprising: a body 202; A control unit 204 for determining characteristics and an irradiation angle of ultrasonic waves irradiated to the nuclear fuel rod cladding 10, and analyzing a waveform of the ultrasonic waves passing through the nuclear fuel rod cladding 10; A water tank 206 for storing water; A rotation motor 208 installed on the front surface of the body 202 and rotating about a longitudinal central axis while the nuclear fuel rod cladding 10 is fixed; A probe 210 installed on the bottom surface of the water tank 206 to irradiate ultrasonic waves toward the distal end of the nuclear fuel rod cladding 10; And an ultrasonic sensor 212 that surrounds the distal end of the nuclear fuel rod cladding 10 and detects ultrasonic waves generated from the probe 210 and passed through the nuclear fuel rod cladding 10.

The probe 210 is characterized in that it is installed so that the angle with respect to the inner bottom surface of the water tank 206 can be changed.

According to the present invention, it is possible to accurately and quickly check defects such as cracks or cavities existing inside by inspecting the nuclear fuel rod cladding in a non-destructive method.

1 is a view showing a control rod driving device of a nuclear reactor.
2 is a view provided for explanation of cracking and leakage of a welding portion of a control rod driving device of a nuclear reactor.
3 is a cross-sectional view showing a structure of a non-destructive inspection device for a welding portion of a through-tube welding part of a reactor upper head control rod driving device according to the prior art.
4 is a perspective view schematically showing the structure of an inspection apparatus according to an embodiment of the present invention.
Figure 5 is a front view of the external structure of the inspection device of Figure 4;
6 is a conceptual diagram showing a method of obtaining an angle of incidence when a 37 degree defect occurs.
7 is a conceptual diagram showing a method of obtaining an angle of incidence when a 20 degree defect occurs.

Hereinafter, a "crack inspection apparatus for cladding a nuclear fuel rod using ultrasonic waves" (hereinafter referred to as a'test apparatus') according to an embodiment of the present invention will be described with reference to the drawings.

4 is a perspective view schematically showing the structure of an inspection apparatus according to an embodiment of the present invention, and FIG. 5 is a front view of the external structure of the inspection apparatus of FIG. 4.

The inspection apparatus 200 of the present invention detects the output waveform while irradiating ultrasonic waves at the distal end while rotating it around the longitudinal central axis in a state where the nuclear fuel rod cladding 10 is placed in a water tank and fixed, and analyzes the waveform to obtain a normal peak value. It is a device that identifies defects inside the nuclear fuel rod cladding 10 by checking whether there are any parts that are not.

A means for fixing and rotating the nuclear fuel rod cladding 10 is provided inside the body 202, and in addition, a power supply unit, a communication device, an analysis device, and the like may be included.

The controller 204 performs an algorithm such as detection of ultrasonic characteristics, irradiation angle, and waveform analysis of ultrasonic waves that have passed through the nuclear fuel rod cladding 10 while performing a non-destructive inspection using ultrasonic waves.

The water tank 206 is a space in which the distal end of the nuclear fuel rod cladding 10 to be inspected is submerged, and has a storage space sufficient for ultrasonic waves to reach and pass through the distal end of the nuclear fuel rod cladding 10 in water.

A rotating motor 208 is provided on the front of the body 202 to rotate while the nuclear fuel rod cladding 10 is fixed. The nuclear fuel rod cladding 10 rotates along the longitudinal central axis by the rotary motor 208. In addition, a moving means may be provided for moving the nuclear fuel rod cladding 10 to be inspected up and down to obtain an appropriate inspection position.

A probe 210 is installed on the bottom surface of the water tank 206. The probe 210 is a means for generating and emitting ultrasonic waves, and irradiates ultrasonic waves in a state close to the distal end of the nuclear fuel rod cladding 10. Due to the structural characteristics of the distal end of the nuclear fuel rod cladding 10, it is necessary to prevent the irradiation angle of ultrasonic waves from being parallel to the longitudinal central axis.

In addition, the probe 210 additionally has a configuration for detecting the nuclear fuel rod cladding 10. Through this, it is configured to operate the ultrasonic emission function only in the state in which the nuclear fuel rod cladding 10 is inserted. In addition, a means for adjusting the height of the probe 210 to adjust the distance to the nuclear fuel rod cladding 10 is further provided.

An ultrasonic sensor 212 for detecting a waveform of ultrasonic waves is provided at an upper portion of the inside of the water tank 206. The ultrasonic sensor 212 is configured to surround the distal end of the nuclear fuel rod cladding 10, and detects ultrasonic waves generated from the probe 210 and passed through the nuclear fuel rod cladding 10 to display a waveform as an image. .

In order to inspect the defects of the nuclear fuel rod cladding 10, water is filled into the water tank 206, and the end of the nuclear fuel rod cladding 10 is fixed to the rotary motor 208, and the ultrasonic sensor inside the water tank 206 Lower it to enter (212).

Then, by the operation of the control unit 204, the probe 210 generates ultrasonic waves, and the waveform of the ultrasonic waves passing through the nuclear fuel rod cladding 10 is displayed as an image.

When the peak value of the waveform of the ultrasonic wave is higher than the value normally generated at the interface of the heterogeneous medium, it can be considered that cracks or cavities have occurred in that part. In the present invention, it is possible to precisely check the presence or absence of an abnormality in the nuclear fuel rod cladding 10 by checking the location of the portion where such an ideally high peak value occurs.

6 is a conceptual diagram illustrating a method of obtaining an incidence angle when a 37 degree defect occurs, and FIG. 7 is a conceptual diagram illustrating a method of obtaining an incidence angle when a 20 degree defect occurs.

In order to execute the defect approach method, first, the distance to the specimen is set in consideration of the focal length of the probe 210.

Then, by calculating Snell's Law, the probe 210 is tilted and inspected at an appropriate angle of incidence.

While the nuclear fuel rod cladding 10 rotates, the supersonic charge generated by the probe 210 passes through the inside and goes straight, or undergoes changes such as reflection and refraction. The ultrasonic sensor 212 detects this change and transmits it to the control unit 204.

If there are defects such as cavities, cracks, foreign substances, etc. inside the nuclear fuel rod cladding 10, as the ultrasonic waves pass through, a sudden change in frequency, wavelength, and output occurs. It can be seen that a defect has occurred at the location where the peak value of the ultrasonic sensing value occurs.

Although a relatively small peak value may occur on the surface of the cladding 10 and the acrylic or cladding, which has a different medium from that of the nuclear fuel rod cladding 10, there is a significant difference from the size of the peak value that occurs in defects in the material. In addition, since the size of the peak value is proportional to the size of the defect space, the size of the defect area can be predicted according to the detection of the peak value.

As shown in Figs. 6 and 7, if the difference between the sound speed inside the water in which the nuclear fuel rod cladding 10 and the probe 210 are immersed and the sound speed inside the cladding 10 is substituted into Snell's law, the defect angle is The incident angle can be obtained accordingly. And from these values, the location and relative size of the defect can be calculated.

In addition, since there is a possibility that factors different from the calculated theoretical value are embedded, the optimum waveform is detected by adjusting the tilting angle and the probe distance.

Finally, the inspection is performed at an angle of 5° to 6°, which was previously inspected by the nuclear power plant manager.

Although preferred embodiments of the present invention have been described above with reference to the accompanying drawings, the technical configuration of the present invention described above is another specific form without changing the technical spirit or essential features of the present invention by those skilled in the art. It will be appreciated that it can be implemented with. Therefore, the above-described embodiments are to be understood as illustrative and non-limiting in all respects, and the scope of the present invention is indicated by the claims to be described later rather than the detailed description, and the meaning and scope of the claims and All changes or modified forms derived from the equivalent concept should be construed as being included in the scope of the present invention.

10: nuclear fuel rod cladding 200: inspection device
202: body 204: control unit
206: water tank 208: rotary motor
210: probe 212: ultrasonic sensor

Claims (2)

As an inspection device that passes ultrasonic waves to the distal end of the nuclear fuel rod cladding 10 that protects the nuclear fuel rod, and analyzes the waveform of the ultrasonic wave that has passed through the nuclear fuel rod cladding 10 to confirm the presence and location of the defect,
A body 202;
A control unit 204 for determining characteristics and an irradiation angle of ultrasonic waves irradiated to the nuclear fuel rod cladding 10, and analyzing a waveform of the ultrasonic waves passing through the nuclear fuel rod cladding 10;
A water tank 206 for storing water in which the distal end of the nuclear fuel rod cladding 10 is submerged;
A rotation motor 208 installed on the front surface of the body 202 and rotating about a longitudinal central axis while the nuclear fuel rod cladding 10 is fixed;
It is installed on the bottom surface of the water tank 206 so that the angle with respect to the inner bottom surface can be changed to irradiate ultrasonic waves toward the distal end of the nuclear fuel rod cladding 10, and the nuclear fuel rod cladding 10 using a sensing means A probe 210 that detects whether it is inserted;
The nuclear fuel rod cladding using ultrasonic waves including; an ultrasonic sensor 212 that surrounds the distal end of the nuclear fuel rod cladding 10 and detects ultrasonic waves generated from the probe 210 and passed through the nuclear fuel rod cladding 10. Crack inspection device. delete

Images