Papers by Author: Chang Hwan Kim

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Authors: Sung Jin Song, Chang Hwan Kim, Deok Hyun Lee, Myung Sik Choi, Do Haeng Hur, Jung Ho Han
Abstract: Through-wall axial cracks occurred by primary water stress corrosion are one of the serious defects in steam generator (SG) tubes (made of alloy 600) in pressurized water reactors. Therefore, it is necessary to detect and size them by eddy current testing (ECT) conducted during in-service inspection of SG tubes. To address this issue, it has been recently proposed an effective method, namely „M-shape profile“ approach, which relies on the difference in the amplitude between the pancake and plus point coils in a MRPC probe. Even though the M-shape curve approach is straightforward in principle, it requires time-consuming data processing if performed by human operators. In order to get rid of this tedious task, an automated system is developed in the present work. This paper addresses the principle of the M-shape approach together with the automated system and its performances for the detection of natural axial cracks in SG tubes. The results observed in the present work demonstrate the high potential of the developed system as a very promising tool for detecting through-wall cracks in many practical field applications.
Authors: Joo Young Yoo, Sung Jin Song, Chang Hwan Kim, Hee Jun Jung, Young Hwan Choi, Suk Chull Kang, Hyun Kyu Jung
Abstract: In the present study, the synthetic signals from the combo tube are simulated by using commercial electromagnetic numerical analysis software which has been developed based on a volume integral method. A comparison of the simulated signals to the experiments is made for the verification of accuracy, and then evaluation of five deliberated single circumferential indication signals is performed to explore a possibility of using a numerical simulation as a practical calibration tool. The good agreement between the evaluation results for two cases (calibration done by experiments and calibration made by simulation) demonstrates such a high possibility.
Authors: Hee Jun Jung, Sung Jin Song, Chang Hwan Kim, Joo Young Yoo, Young Hwan Choi, Suk Chull Kang, Myung Ho Song
Abstract: For inspection of steam generator tubes in nuclear power plants using eddy current testing, it is a very crucial task to extract the flaw signal from signals compounded by flaws and supporting structures. To perform such an important task, the multifrequency eddy current testing method is widely adopted. In this study, we explore the performance of a linear mixing technique based on the discrete cosine transform method by experiments. The results obtained using the DCT based method agree very well to those obtained by commercial software demonstrating the effectiveness of the approach.
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