• Proceedings of the Korean Nuclear Society Conference
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• 2005.10a
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• pp.947-948
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• 2005

• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.702-704
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• 2003

In this paper, analysis of bobbin probe signal in steam generator tube with bulge defect on CE system 80 nuclear power plant is represented. The CE system 80 steam generator is adopted in ULJIN-4 nuclear power plant. From Maxwell's equation, the electromagnetic governing equation for eddy current problem is derived and by performing the finite element formulation the 3-dimensional finite element code with brick element is developed. For the ease of the comparison the numerical results with experimental ones, the calculated signals are adjusted by using the ASME standard 100[%] through hole signal. For analysis of the effect of variation of the bulge depth on the impedance signal 0.2[mm] and 0.4[mm] depth of bulge defect signals are calculated and analyzed. As the depth of the bulge defect is increased, the magnitude of the signal is increased, too. But the rate of the increment of the signal is less than that of the depth of defect. From the result of this paper, we can obtained the information of the effect of bulge defect on the impedance signal.

• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.2
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• pp.184-190
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• 2008

Various ECT techniques have been applied basically to assess the integrity of steam generator tithing in nuclear power plant. Among these techniques, the bobbin probe technique is applied generally to examine the volumetric flaws such as a crack-like defect and wear which is generally occurred on steam generator tubing, and additionally MRPC probe is used to examine closely tile top of tubesheet and bending regions due to the high possibility of cracking. Dent and bulge also may be formed on tube during installation process and operation of steam generator, but the dent and bulge indications greater than specific size criteria are recorded on examination report because these indications are not considered as flaw. These indications can be easily detected with bobbin probe and approximately sized with profile bobbin probe, but the size and shape can not be accurately verified. Accordingly, in this study, the $8{\times}1$ multi-array EC probe was designed to increase the measurement accuracy of the sectional profiling EC testing of tube. As a result, we would like to propose the application of $8{\times}1$ multi-array EC probe for the measurement of size and shape of profile change on steam generator tube in OPR-1000 nuclear power plant.

• Journal of the Korean Society for Nondestructive Testing
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• v.30 no.4
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• pp.386-395
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• 2010

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.

• Journal of Magnetics
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• v.14 no.2
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• pp.97-100
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• 2009

A new eddy current testing probe was developed to separate the eddy current signal distortion caused by permeability variation clusters and ordinary defects created in steam generator tubes. Signal processing circuits were inserted into the probe to increase the signal-to-noise ratio and allow digital signal transmission. The new probe could measure and separate the magnetic phases created in the steam generator tubes in the operating environment of a nuclear power plant. Furthermore, the new eddy current testing probe can measure the defects in steam generator tubes as rapidly as a bobbin probe with enhanced testing speed and reliability of defect detection.

• Proceedings of the Korean Nuclear Society Conference
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• 2005.10a
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• pp.957-958
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• 2005

• Journal of the Korean Society for Nondestructive Testing
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• v.36 no.4
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• pp.295-299
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• 2016

Residual foreign objects at the secondary side (top of the tubesheet and tube support plates) of a steam generator are likely to cause a leak by causing wear in the tube. The extent of wear is significantly affected by the material, shape, and size of the foreign object, and the corrosion properties of the tube. The presence of foreign objects at the top of the tubesheet and tube support plates has been identified using remote visual inspection methods such as the foreign object search and retrieval and eddy current test (ECT). The detection of the residual foreign object at the secondary side of a steam generator has limitations that depend on the material properties and the condition of contact with the tube. In this study, which is vertical and horizontal from the upper tubesheet, the corresponding bobbin ECT signals were collected and analyzed to measure its ability to detect foreign objects.

• Journal of the Korean Society for Nondestructive Testing
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• v.33 no.6
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• pp.519-523
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• 2013

A steam generator (SG) tube is an important component of a nuclear power plant (NPP). It works as a pressure boundary between the primary and secondary systems. The integrity of a SG tube can be assessed by an eddy current test every outage. The eddy current technique(adopting a bobbin probe) is currently the main technique used to assess the integrity of the tubing of a steam generator. An eddy current signal analyst for steam generator tubes continuously analyzes data over a given period of time. However, there are possibilities that the analyst conducting the test may get tired and cause mistakes, such as: missing indications or not being able to separate a true defect signal from one that is more complicated. This error could lead to confusion and an improper interpretation of the signal analysis. In order to avoid these possibilities, many countries of opted for automated analyses. Axial ODSCC (outside diameter stress corrosion cracking) defects on the tubes of OPR1000 steam generators have been found on the tube that are in contract with tube support plates. In this study, automated analysis software called CDS (computer data screening) made by Zetec was used. This paper will discuss the results of introducing an automated analysis system for an axial ODSCC on the tubes of an OPR1000 steam generator.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.10 no.1
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• pp.75-81
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• 2014

A simulation of eddy current testing has been utilized for predicting the signal characteristics to the various defects and developing the probes. Especially, CIVA which is a simulation tool dedicated to nondestructive testing has a good accuracy and speed, and provides a three-dimensional graphical user interface for improved visualization and familiar data displays consistent with NDE technique. Although internal validations have been performed by the CIVA software development specialists, an independent validation study is necessary for the accuracy assessment of the software prior to practical use. For this purpose, in this study, eddy current testing signals of ASME FBH calibration standard tube for bobbin probe were simulated using CIVA and the results were compared to the experimental inspected signals based on the relationship between each flaw signal in terms of amplitude and phase, and the shape of the Lissajous curve. And then we verified the accuracy of the simulated signals and the possible range for simulation. Overall, there is a good qualitative agreement between the CIVA simulated and experimental results in the absolute and differential modes at the two inspection frequencies.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.4 no.2
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• pp.34-39
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• 2008

Steam Generator(SG) tubes are classified as one of the key components in nuclear power plants, and they should be periodically examined by the intensified management program for the assurance and diagnosis of their structural integrity. In this study, we use the optimum analysis technique to draw the detection and categorization of bowing(BOW) signals; abnormal tube-to-tube proximity in the SG upper bundle free span area. The locations in which BOW signals are detected likely have latent degradation of ODSCC(Outer Diameter Stress Corrosion Cracking). For the sake of timely and correct detection of BOW signals and diagnosis of ODSCC, we carried out the experimental demonstrations using a reduced mock-up. And we validated the MRPC(Motorized Rotating Pancake Coil) analysis technique is better than the bobbin. Hence, it comes to conclusion that the optimum analysis technique can be a good alternative for the reliable SG tube examination.