• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.7
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• pp.1014-1020
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• 2004

The present work complies the elastic stress concentration factor for a pipe with local wall thinning, based on detailed three-dimensional elastic FE analysis. To cover practically interesting cases, a wide range of pipe and defect geometries are considered, and both internal pressure and global bending are considered. Resulting values of stress concentration factors are tabulated for practical use, and the effect of relevant parameters such as pipe and defect geometries on stress concentration factors are discussed. The present results would provide valuable information to estimate fatigue damage of the pipe with local wall thinning under high cycle fatigue.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.616-621
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• 2001

Flow-accelerated corrosion(FAC) is a phenomenon that results in metal loss from piping, vessels, and equipment made of carbon steel. FAC occurs only under certain conditions of flow, chemistry, geometry, and material. Unfortunately, those conditions are in much of the high-energy piping in nuclear and fossil-fueled power plants. Also, for domestic NPP secondary pipings whose operating time become longer, more evidences of FAC have been reported. The authors are studying on FAC management using CHECWORKS, computer code developed by EPRI. This paper is on the prediction results of metal loss by FAC in the one of CANDU type NPP secondary piping systems.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.27-28
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• 2006

This study performs to investigate deformation of wall thinning pipe and to find out the position of the internal thinning defect by shearography. Shearography is one of optical methods those have applied to nondestructive testing (NDT) and the strain/stress analysis. This technique has the merit of the directly measuring the first derivative of displacement, sensitivity of which can be adjusted by the handling of optical component in interferometer. In this paper, we tested carbon steel pipe locally wall thinned and loaded internal pressure and developed the nondestructive out-of-plane deformation analysis technique fur internal thinning defect of elbow by shearography. From the results, it was confirmed that this technique is proper to the practical application on the pipe line system with internal defect.

• Proceedings of the Korean Society of Computer Information Conference
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• 2022.07a
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• pp.11-14
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• 2022

본 논문에서는 회귀 문제에서 예측값들의 분산을 줄이기 위한 딥뉴럴 네트워크 구조를 제안한다. 일반적인 회귀 문제에서 딥뉴럴 네트워크 학습 시, 하나의 입력에 대한 레이블 값을 이용하여 학습한다. 본 눈문에서는 하나의 입력에 대한 레이블 값뿐만 아니라 두 입력에 대한 레이블 값들의 차이를 학습시키는 딥뉴럴 네트워크 구조를 제안한다. 통계학 이론을 통하여 예측값들의 분산이 줄어든다는 것을 증명한다. 또한, 배관 곡관의 감육두께를 예측하는 문제를 통해 제안된 네트워크의 성능을 검증한다. 일반적인 딥뉴럴 네트워크 구조를 이용하였을 때에 비하여 제안한 네트워크 구조를 이용하였을 때, 회귀 문제의 예측값들의 분산이 감소함을 확인한다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.06a
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• pp.119-120
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• 2007

• Corrosion Science and Technology
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• v.15 no.3
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• pp.135-140
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• 2016

Piping and equipment are degraded by flow-accelerated corrosion (FAC) in nuclear power plants. FAC causes numerous problems and nuclear utilities maintain programs to control FAC. The key parameters influencing FAC are hydrodynamic conditions, water chemistry, and effect of materials. Recently, a nuclear utility has planned slight power uprates in Korea. Operating conditions need to be changed in the secondary system according to power uprates. This study analyzed the effect of wall-thinning caused by power uprates. The change of operation data in the secondary cycle is reviewed, and wall-thinning rates are analyzed in the main lines. As a result, two phase (mixture of water and steam) lines have a greater impact than a water line under power uprate conditions. Also, the quality of steam is the most important factor for FAC in two phase lines.

• Corrosion Science and Technology
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• v.14 no.6
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• pp.325-330
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• 2015

Pipe wall-thinning by flow-accelerated corrosion (FAC) is a significant and costly damage of secondary system piping in nuclear power plants (NPPs). All NPPs have their management programs to ensure pipe integrity from wall-thinning. This study analyzed the pipe wall-thinning caused by changing the amine, which is used for adjusting the water chemistry in the secondary system of NPPs. The pH change was analyzed according to the addition of amine. Then, the wear rate calculated in two different amines was compared at the steam cycle in NPPs. As a result, increasing the pH at operating temperature (Hot pH) can reduce the rate of FAC damage significantly. Wall-thinning is affected by amine characteristics depending on temperature and quality of water.

• Corrosion Science and Technology
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• v.11 no.4
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• pp.129-134
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• 2012

UT(Ultrasonic Test), one of the non-destructive tests, is the most common thickness measurement method for evaluating the wear rate in NPPs(Nuclear Power Plants). UT is used widely because it is easy and safe for use. However some amount of error inevitably occurs in attempting to measure the thickness. The error, that could make the thickness data thicker or thinner, may affect estimation of wear rate in pipes. NPPs are composed of a lot of pipes and components. Some of them are tested to check the current status during RFO(Re-Fueling Outage). Reliability analysis of UT is essential for evaluating pipe wear rate and establishing the long-term management plan in NPPs. This paper reviewed the cause of error occurrence and presented the UT data reliability analysis method. Also, this paper shows the application result of reliability analysis to the UT data acquired in NPPs.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.6 no.2
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• pp.47-53
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• 2010

In this research project, development of methodology to measure the thickness of pipes in the wide range using magnetic field. The magnetic field spreading in the sensor and the plate was modeled in the cases of the various thicknesses in plate. Based on the analysis, sensors were designed, manufactured and tested to optimize the specifications of the sensor. The sensor can be used in high temperature through calibration. And the uncertainty of the sensor was estimated.

• Corrosion Science and Technology
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• v.15 no.6
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• pp.320-325
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• 2016

To perform ultrasonic testing (UT) thickness measurement of the secondary side piping installed in nuclear power plants, the insulation for preventing heat loss should be removed. The type of insulation can be divided into fixed and removable insulation. Fixed and removable insulation have their own strengths and weaknesses. Removable insulation has been installed in the components susceptible to wall thinning caused by FAC and erosion from Shin-Kori unit 1, which commenced its commercial operation in 2011. In this paper, the number of repeated inspections of components and the number of replacements of fixed insulation were estimated and a more economical way was identified based on the manufacturing and installation costs for fixed and removable insulation.