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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Korean Society for Nondestructive Testing
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Journal DOI :
The Korean Society for Nondestructive Testing
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Volume & Issues
Volume 30, Issue 6 - Dec 2010
Volume 30, Issue 5 - Oct 2010
Volume 30, Issue 4 - Aug 2010
Volume 30, Issue 3 - Jun 2010
Volume 30, Issue 2 - Apr 2010
Volume 30, Issue 1 - Feb 2010
Selecting the target year
Assessment of Pipe Wall Loss Using Guided Wave Testing
Joo, Kyung-Mun ; Jin, Seuk-Hong ; Moon, Yong-Sig ;
Journal of the Korean Society for Nondestructive Testing, volume 30, issue 4, 2010, Pages 295~301
Flow accelerated corrosion(FAC) of carbon steel pipes in nuclear power plants has been known as one of the major degradation mechanisms. It could have bad influence on the plant reliability and safety. Also detection of FAC is a significant cost to the nuclear power plant because of the need to remove and replace insulation. Recently, the interest of the guided wave testing(GWT) has grown because it allows long range inspection without removing insulation of the pipe except at the probe position. If GWT can be applied to detection of FAC damages, it will can significantly reduce the cost for the inspection of the pipes. The objective of this study was to determine the capability of GWT to identify location of FAC damages. In this paper, three kinds of techniques were used to measure the amplitude ratio between the first and the second welds at the elbow area of mock-ups that contain real FAC damages. As a result, optimal inspection technique and minimum detectability to detect FAC damages drew a conclusion.
A Study on Bagging Neural Network for Predicting Defect Size of Steam Generator Tube in Nuclear Power Plant
Kim, Kyung-Jin ; Jo, Nam-Hoon ;
Journal of the Korean Society for Nondestructive Testing, volume 30, issue 4, 2010, Pages 302~310
In this paper, we studied Bagging neural network for predicting defect size of steam generator(SG) tube in nuclear power plant. Bagging is a method for creating an ensemble of estimator based on bootstrap sampling. For predicting defect size of SG tube, we first generated eddy current testing signals for 4 defect patterns of SG tube with various widths and depths. Then, we constructed single neural network(SNN) and Bagging neural network(BNN) to estimate width and depth of each defect. The estimation performance of SNN and BNN were measured by means of peak error. According to our experiment result, average peak error of SNN and BNN for estimating defect depth were 0.117 and 0.089mm, respectively. Also, in the case of estimating defect width, average peak error of SNN and BNN were 0.494 and 0.306mm, respectively. This shows that the estimation performance of BNN is superior to that of SNN.
Pipeline Defects Detection Using MFL Signals and Self Quotient Image
Kim, Min-Ho ; Rho, Yong-Woo ; Choi, Doo-Hyun ;
Journal of the Korean Society for Nondestructive Testing, volume 30, issue 4, 2010, Pages 311~316
Defects positioning of underground gas pipelines using MFL(magnetic flux leakage) inspection which is one of non-destructive evaluation techniques is proposed in this paper. MFL signals acquired from MFL PIG(pipeline inspection gauge) have nonlinearity and distortion caused by various external disturbances. SQI(self quotient image), a compensation technique for nonlinearity and distortion of MFL signal, is used to correct positioning of pipeline defects. Through the experiments using artificial defects carved in the KOGAS pipeline simulation facility, it is found that the performance of proposed defect detection is greatly improved compared to that of the conventional DCT(discrete cosine transform) coefficients based detection.
Procedure Development and Qualification of the Phased Array Ultrasonic Testing for the Nuclear Power Plant Piping Weld
Yoon, Byung-Sik ; Yang, Seung-Han ; Kim, Yong-Sik ; Lee, Hee-Jong ;
Journal of the Korean Society for Nondestructive Testing, volume 30, issue 4, 2010, Pages 317~323
The manual ultrasonic examination for the nuclear power plant piping welds has been demonstrated by using KPD(Korean Performance Demonstration) generic procedure. For automated ultrasonic examination, there is no generic procedure and it should be qualified by using applicable automated equipment. Until now, most of qualified procedures used pulse-echo technique and there is no qualified procedure using phased array technique. In this study, data acquisition and analysis software were developed and phased-array transducer and wedge were designed to implement phased array technique for nuclear power plant in-service inspection. The developed procedure are qualified for performance demonstration for the flaw detection, length sizing and depth sizing. The qualified procedure will be applied for the field examination in the nuclear power plant piping weld inspection.
X-Ray Tomography Based Simulation Feasibility Analysis of Nuclear Fuel Pellets
Kim, Jae-Joon ;
Journal of the Korean Society for Nondestructive Testing, volume 30, issue 4, 2010, Pages 324~329
Fuel rods using in nuclear power plants consist of uranium dioxide pellets enclosed in zirconium alloy(zircaloy) tubes. It is vitally important for the pellet surface to remain free from pits, cracks and chipping defects after it is loaded into the tubes to prevent local hot spots during reactor operation. This paper investigates the feasibility study for detecting surface flaws of pellets contained within nuclear fuel rod through X-ray tomography simulation. Reconstructed images used by parallel and fan-beam filtered back projection method were presented and confirmed the accessibility between simulation data and MPS(missing pellet surface) image data.
Characteristic Analysis of Eddy Current Array Probe Signal in Combo Calibration Standard Tube Using Electromagnetic Numerical Analysis
Kim, Ji-Ho ; Lee, Hyang-Beom ;
Journal of the Korean Society for Nondestructive Testing, volume 30, issue 4, 2010, Pages 330~337
In this paper, 3-dimensional electromagnetic numerical analysis is performed about the eddy current(EC) array probe characteristic which is the next generation probe for accurate diagnosis of steam generator(SG) in nuclear power plants(NPPs). ASME(American Society of Mechanical Engineers) Standard and X-probe combo calibration standard tube are selected for acquisition of eddy current testing(ECT) signals and this result of compared with the real test signals for reasonability of result. Based on the analysis result of calibration standard tube, ECT signals that are about the defects of pitting, stress corrosion cracking(SCC), multiple SCC and wear is obtained. Material of specimen was Inconel 600 which is usually used for SG tubes in NPPs. The operation frequency of 300 kHz were used. The signal characteristics could be observed according to the various defects. The results in this paper can be helpful when the ECT signals from EC array probe are evaluated and analyzed.
Development of Double Rotation C-Scanning System and Program for Under-Sodium Viewing of Sodium-Cooled Fast Reactor
Joo, Young-Sang ; Bae, Jin-Ho ; Park, Chang-Gyu ; Lee, Jae-Han ; Kim, Jong-Bum ;
Journal of the Korean Society for Nondestructive Testing, volume 30, issue 4, 2010, Pages 338~344
A double rotation C-scanning system and a software program Under-Sodium MultiVIEW have been developed for the under-sodium viewing of a reactor core and in-vessel structures of a sodium-cooled fast reactor KALIMER-600. Double rotation C-scanning system has been designed and manufactured by the reproduction of double rotation plug of a reactor head in KALIMER-600. Hardware system which consists of a double rotating scanner, ultrasonic waveguide sensors, a high power ultrasonic pulser-receiver, a scanner driving module and a multi channel A/D board have been constructed. The functions of scanner control, image mapping and signal processing of Under-Sodium MultiVIEW program have been implemented by using a LabVIEW graphical programming language. The performance of Under-Sodium MultiVIEW program was verified by a double rotation C-scanning test in water.
Oblique Incidence Technique for Ultrasonic Nonlinear Characterization in SUS316L Alloy
Baek, Seung-Hyun ; Lee, Tae-Hun ; Kim, Chung-Seok ; Jhang, Kyung-Young ;
Journal of the Korean Society for Nondestructive Testing, volume 30, issue 4, 2010, Pages 345~351
The oblique incidence technique for ultrasonic nonlinear characterization was studied in stainless steel 316L alloy subjected to high cycle fatigue. A dog-bone plate specimen was prepared to make different faitgue-driven deformation at each position where the stress concentration could occur in the middle of specimen. In addition to the normal transmission technique, the oblique incidence technique which is newly suggested in this study, was used to measure ultrasonic nonlinear parameter. The fatigued specimen shows higher ultrasonic nonlinear parameter than the virgin specimen for both techniques. Ultrasonic nonlinear parameter highly increases in the middle of test specimen where the stress concentration existes. Relative nonlinear parameter has strong correlation with fatigue damage. Consequently, the oblique incidence technique with longitudinal wave can be potential to characterize high cycle fatigue damage.
Nondestructive Imaging of an Object Using the Compact Continuous-Wave Sub-Terahertz Imaging System
Jang, Jin-Seok ; Kwon, Il-Bub ; Yoon, Dong-Jin ; Seo, Dae-Cheol ;
Journal of the Korean Society for Nondestructive Testing, volume 30, issue 4, 2010, Pages 352~358
This paper presented compact CW sub-THz imaging system using the terahertz transmitter(Tx) that generating 0.34 THz electromagnetic wave on based electronic device. Using 0.34 THz electromagnetic wave generated by Tx, we transmitted to sample by point by point scan method and measured transmitting terahertz wave magnitude and phase information respectively with terahertz receiver(Rx) based on sub harmonic mixer. This paper measured and compared images of several samples to obtain better imaging results by changing time delay and step distance of scanning stage which affect image resolution. Also, through the imaging measurement of various samples, we were able to assure possibility of application of terahertz wave.
Quantitative Estimation of Transmitted and Reflected Lamb Waves at Discontinuity
Lim, Hyung-Jin ; Sohn, Hoon ;
Journal of the Korean Society for Nondestructive Testing, volume 30, issue 4, 2010, Pages 359~366
For the application of Lamb wave to structural health monitoring(SHM), understanding its physical characteristic and interaction between Lamb wave and defect of the host structure is an important issue. In this study, reflected, transmitted and mode converted Lamb waves at discontinuity of a plate structure were simulated and the amplitude ratios are calculated theoretically using Modal decomposition method. The predicted results were verified comparing with finite element method(FEM) and experimental results simulating attached PZTs. The result shows that the theoretical prediction is close to the FEM and the experimental verification. Moreover, quantitative estimation method was suggested using amplitude ratio of Lamb wave at discontinuity.
Development of Automated Ultrasonic Testing System for Partial Joint-Weld of Heat Exchanger's Header to Tube in Power Plant
Lee, Jin-Hyuk ; Lim, Seong-Jin ; Park, Ik-Keun ; Kim, Dae-Hyun ;
Journal of the Korean Society for Nondestructive Testing, volume 30, issue 4, 2010, Pages 367~372
A power plant's heat exchangers work under poor conditions, such as high temperature, high pressure, corrosion, mechanical stress and vibration. Especially, partial joint-weld of heat exchanger's header to stub-tube is the place where incomplete penetration flaws can easily occur. But, it is hard to evaluate the safety of the structure by conventional nondestructive testing techniques. So it is necessary to test integrity of the weld inside and to develop testing technique and equipment that can detect the flaws at the weld point in order to enhance reliability of the test result. In this study, we developed a suitable automated ultrasonic testing system that can inspect the partial joint-weld of header to stub-tube of power plant. Finally, we showed the efficiency of the automated ultrasonic-testing-system from the application.
Fabrication of Phased Array EMAT and Its Characteristics
Ahn, Bong-Young ; Cho, Seung-Hyun ; Kim, Young-Joo ; Kim, Ki-Bok ;
Journal of the Korean Society for Nondestructive Testing, volume 30, issue 4, 2010, Pages 373~379
EMAT has been applied in various fields for flaw detection and material characterization because it has noncontact property in wave generation and a good mode selectivity. Unfortunately, however, EMAT shows low signal to noise ratio relative to commercial contact transducer because of low energy conversion efficiency. If the phase matching through the control of time delay between each coil consisting of the array EMAT is accomplished, it is expected that it will be a solution for the improvement of low signal to noise ratio. In this experiment, the phased array EMATs which consists of 3 or 4 meander coils and one big magnet were fabricated for surface and vertical shear wave generation. Effect of phased delay control on signal directivity and amplitude enhancement was verified. A slit with the depth of 0.5 mm and a side-drill hole of 0.5 mm diameter were clearly detected by fabricated phased array EMATs, respectively.
Safety Regulation of Enhanced In-Service Inspection(ISI) in Nuclear Power Plant
Shin, Ho-Sang ;
Journal of the Korean Society for Nondestructive Testing, volume 30, issue 4, 2010, Pages 380~385
The integrity of components and piping of operating nuclear power plants has been identified by in-service inspection(ISI) requirements and activities commensurate with standards and codes such as KEPIC MI or ASME Code Section XI. However, the other various degradation mechanisms not considered during design stage of nuclear power plants have been checked by enhanced ISI. The requirements of enhanced ISI have been voluntarily developed by the industry itself or strickly issued by regulatory body. Even though the requirements were developed by the industry, they should be reviewed by regulatory body for their application in nuclear power plants. The enhanced ISI activities and requirements of non-destructive examination(NDE) which reflect the degradation issues in nuclear power industry will be primarily discussed in this paper.
Characteristics Testing of the ECT Bobbin Probe for Steam Generator Tube Inspection of Nuclear Power Plant
Nam, Min-Woo ; Lee, Hee-Jong ; Cho, Chan-Hee ; Yoo, Hyun-Joo ;
Journal of the Korean Society for Nondestructive Testing, volume 30, issue 4, 2010, Pages 386~395
The steam generator management program(SGMP) has recently defined the procedures for the qualification of eddy current hardware and technique. These procedures provide two basic methods for qualification. The first way is to qualify the equipment or the probe by using the flaw mechanism and method of the pulled tubes from the heat exchangers or the artificial flawed tubes. The second way is to verify the equivalency with the characteristics of the qualified equipment or probe. In this case, the qualified equipment or probe may be modified to substitute or replace instruments or probes without re-qualification provided that the range of essential variables defined in the examination technique specification sheet are met. This study is to describe the result of the comparative performance evaluation of bobbin coil eddy current probes manufactured by KEPCO Research Institute and probes manufactured by a foreign manufacturer. As a result of this study, although there were minor differences between the two kinds of probes, it was evaluated that the two kinds of probes were almost identical in the significant performance characteristics described in the KEPCO Research Institute guideline.