• Title/Summary/Keyword: Corrosion detection

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Simulation Based Investigation of Focusing Phased Array Ultrasound in Dissimilar Metal Welds

  • Kim, Hun-Hee;Kim, Hak-Joon;Song, Sung-Jin;Kim, Kyung-Cho;Kim, Yong-Buem
    • Nuclear Engineering and Technology
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    • v.48 no.1
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    • pp.228-235
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    • 2016
  • Flaws at dissimilar metal welds (DMWs), such as reactor coolant systems components, Control Rod Drive Mechanism (CRDM), Bottom Mounted Instrumentation (BMI) etc., in nuclear power plants have been found. Notably, primary water stress corrosion cracking (PWSCC) in the DMWs could cause significant reliability problems at nuclear power plants. Therefore, phased array ultrasound is widely used for inspecting surface break cracks and stress corrosion cracks in DMWs. However, inspection of DMWs using phased array ultrasound has a relatively low probability of detection of cracks, because the crystalline structure of welds causes distortion and splitting of the ultrasonic beams which propagates anisotropic medium. Therefore, advanced evaluation techniques of phased array ultrasound are needed for improvement in the probability of detection of flaws in DMWs. Thus, in this study, an investigation of focusing and steering phased array ultrasound in DMWs was carried out using a time reversal technique, and an adaptive focusing technique based on finite element method (FEM) simulation. Also, evaluation of focusing performance of three different focusing techniques was performed by comparing amplitude of phased array ultrasonic signals scattered from the targeted flaw with three different time delays.

A Study on the Development and the Verification Experiment of ECDA Equipment (외면부식직접평가 장비 개발 및 실증 시험에 관한 연구)

  • Ryou, Young-Don;Lee, Jin-Han;Jung, Sung-Won;Park, Kyeong-Wan
    • Journal of the Korean Institute of Gas
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    • v.20 no.5
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    • pp.72-81
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    • 2016
  • When the coatings of buried steel pipelines are damaged, corrosion could be occurred on the surface of the damaged areas. Moreover the pinhole occurred by corrosion of pipelines may cause accidents due to gas leakage. To prevent these accidents, foreign countries including UK and USA have carried out coating defect detection on the buried gas pipelines by using a DCVG or a ACVG and have conducted direct assessment of pipelines through digging the ground, and if necessary, have repaired the pipelines. That is called ECDA i.e External Corrosion Direct Assessment which is regulated by NACE standards(SP 0502) and etc. In Korea, the ECDA provisions were included in KGS FS551 in 2014 when the regulations of Safety Validation in Detail for the medium-pressure piping were introduced. We have developed the equipment which can be used to detect external corrosion of the buried gas pipelines. We have also constructed pipeline test bed for empirical test of the developed equipment. In addition, we have carried out the verification experiments of the developed equipment on the test bed to demonstrate the performance of the equipment. The experiments were conducted by comparison tests of the developed equipment and other equipments which have been introduced and used in Korea. As the result, we have found the developed equipment is easier to use and has far superior performance compared to other equipment being used in Korea.

Power spectral density method performance in detecting damages by chloride attack on coastal RC bridge

  • Mehrdad, Hadizadeh-Bazaz;Ignacio J., Navarro;Victor, Yepes
    • Structural Engineering and Mechanics
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    • v.85 no.2
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    • pp.197-206
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    • 2023
  • The deterioration caused by chloride penetration and carbonation plays a significant role in a concrete structure in a marine environment. The chloride corrosion in some marine concrete structures is invisible but can be dangerous in a sudden collapse. Therefore, as a novelty, this research investigates the ability of a non-destructive damage detection method named the Power Spectral Density (PSD) to diagnose damages caused only by chloride ions in concrete structures. Furthermore, the accuracy of this method in estimating the amount of annual damage caused by chloride in various parts and positions exposed to seawater was investigated. For this purpose, the RC Arosa bridge in Spain, which connects the island to the mainland via seawater, was numerically modeled and analyzed. As the first step, each element's bridge position was calculated, along with the chloride corrosion percentage in the reinforcements. The next step predicted the existence, location, and timing of damage to the entire concrete part of the bridge based on the amount of rebar corrosion each year. The PSD method was used to monitor the annual loss of reinforcement cross-section area, changes in dynamic characteristics such as stiffness and mass, and each year of the bridge structure's life using sensitivity equations and the linear least squares algorithm. This study showed that using different approaches to the PSD method based on rebar chloride corrosion and assuming 10% errors in software analysis can help predict the location and almost exact amount of damage zones over time.

Prevention of Soil Contamination from Underground Storage Facilities (유류저장시설로 인한 토양오염 예방대책)

  • 배우근;홍종철;정진욱;강우재
    • Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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    • 1998.11a
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    • pp.169-173
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    • 1998
  • The practice of the construction and management of the underground petroleum storage facilities in Korea was investigated extensively, and the problems were identified. The advanced technologies in the U.S.A was comparatively studied. Considering the effectiveness of leak prevention and technology applicability, the following measures were suggested. To prevent corrosion of the tank, a clad tank, an interior-lining tank, or a double-wall tank was appropriate and appeared to be most cost effective. For piping, non-metalic material was suggested. To prevent spill, a catchment basin can be effective. For monitoring of leak, construction of more than one of one or combination of an automatic leak-detection device, a vapor-detection system, a ground water-monitoring system, and a double-wall detection system was recommended.

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Reliability Analysis of Prestress Concrete Box Girder Bridges Considering Inspection Cost (검측비용을 고려한 PC박스 거더의 신뢰성 분석)

  • Nguyen, Van Son;Jeong, Min-Chul;Kong, Jung-Sik
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2010.04a
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    • pp.476-479
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    • 2010
  • In recent years, the deterioration of infrastructures is especially considered. In prestress concrete bridges, one of the important mechanisms of deterioration is the corrosion of the post-tensioned tendon due to environmental agents. In this study, the reliability analysis is performed for a prestress concrete box girder bridge under the pitting corrosion attack with considering the inspection and failure cost. The variation of life-time performance depending on inspection methods have to be quantified. The inspection methods with different accuracy of corrosion detection are presented and applied for model of reliability analysis. The computer program for analysis reliability index of the structure as well as updating process is obtained. An existing bridge is applied for illustrating the influence of inspection cost on the behaviors of structure. Subsequently, the benefit of inspection has shown to predict the time to failure of structure.

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A Study on The Detection of Stress Corrosion Cracking Of SCM-4 by Acoustic Emission Method (AE 法 에 의한 高强度鋼 ( SCM - 4 ) 의 應力腐식균열進展 의 檢出 에 관한 硏究)

  • 서창민;문용식
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.6 no.4
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    • pp.377-383
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    • 1982
  • Acoustic emission (AE) of a high strength steel (SCM-4) was measured under stress corrosion cracking(SCC) test at a constant displacement in 3.5% artificial NaCl solution of 18.deg.C, 45.deg.C and 60.deg.C, respectively. The results are as follows; During the SCC test, AE is detected and AE count rate is approximately proportional to the crack growth rate. Even though crack is not propagated macroscopically, AE is detected. The crack growth rate of SCC and the AE count rate are higher for the solution of higher temperature, 45.deg.C and 60.deg.C, than for the solution of lower temperature, 18.deg.C. In the early stage of SCC, AE total counts mostly depend on crack growth. In the later stage, however, AE mostly depends on the film fracture and the dissolution of anode.

PFM APPLICATION FOR THE PWSCC INTEGRITY OF Ni-BASE ALLOY WELDS-DEVELOPMENT AND APPLICATION OF PINEP-PWSCC

  • Hong, Jong-Dae;Jang, Changheui;Kim, Tae Soon
    • Nuclear Engineering and Technology
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    • v.44 no.8
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    • pp.961-970
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    • 2012
  • Often, probabilistic fracture mechanics (PFM) approaches have been adopted to quantify the failure probabilities of Ni-base alloy components, especially due to primary water stress corrosion cracking (PWSCC), in a primary piping system of pressurized water reactors. In this paper, the key features of an advanced PFM code, PINEP-PWSCC (Probabilistic INtegrity Evaluation for nuclear Piping-PWSCC) for such purpose, are described. In developing the code, we adopted most recent research results and advanced models in calculation modules such as PWSCC crack initiation and growth models, a performance-based probability of detection (POD) model for Ni-base alloy welds, and so on. To verify the code, the failure probabilities for various Alloy 182 welds locations were evaluated and compared with field experience and other PFM codes. Finally, the effects of pre-existing crack, weld repair, and POD models on failure probability were evaluated to demonstrate the applicability of PINEP-PWSCC.

Zinc Loss Detection in ACSR Power Lines using the Removable Type of Eddy Current Sensor (착탈형 와류센서를 이용한 ACSR전선의 아연손실량 검출)

  • Jang, T.I.;Jo, S.B.;Kang, J.W.;Kang, Y.W.;Yang, B.M.
    • Proceedings of the KIEE Conference
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    • 2000.07c
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    • pp.1963-1965
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    • 2000
  • This paper deals with a problem of detecting the inner corrosion of the ACSR(Aluminum Conductor Steel Reinforced) power lines using a detector which consists of an ECT(Eddy Current Test) sensor, a constant current service, a signal processing unit, and a RF transmitter/receiver unit. The detector runs on the ACSR transmission line and inspects the corrosion of the conductor using the technic of the nondestructive eddy current test. The experimental result shows this detector can efficiently find the zinc loss in ACSR power lines.

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Detection of Low Cycle Fatigue in Type 316 Stainless Steel using HTS-SQUID

  • Park, D.G.;Kim, D.W.;Timofeev, V.P.;Hong, J.H.
    • Corrosion Science and Technology
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    • v.3 no.5
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    • pp.222-225
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    • 2004
  • A portable RF HTS SQUID-based susceptometer was applied to the measurement of fatigue behavior for type 316L(N) stainless steel containing 0.04% to 0.15% nitrogen content. Strain-controlled low cycle fatigue (LCF) tests were conducted at RT and $600^{\circ}C$ in air an atmosphere, and the magnetic moments were measured after the fatigue test using HTS SQUID. The magnetic moment of an as-received sample is higher than that of a fatigued sample in all the temperature ranges irrespective of the nitrogen content. The fatigue life decreased with an increasing test temperature up to $500^{\circ}C$, but increased at $600^{\circ}C$. The change of the magnetic moments by LCF test is attributed to the stress induced micro defects.

Effect of oxide film on ECT detectability of surface IGSCC in laboratory-degraded alloy 600 steam generator tubing

  • Lee, Tae Hyun;Ryu, Kyung Ha;Kim, Hong Deok;Hwang, Il Soon;Kim, Ji Hyun;Lee, Min Ho;Choi, Sungyeol
    • Nuclear Engineering and Technology
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    • v.51 no.5
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    • pp.1381-1389
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    • 2019
  • Stress corrosion cracking (SCC) widely found in both primary and secondary sides of steam generator (SG) tubing in pressurized water reactors (PWR) has become an important safety issue. Using eddy-current tests (ECTs), non-destructive evaluations are performed for the integrity management of SG tubes against intergranular SCC. To enhance the reliability of ECT, this study investigates the effects of oxide films on ECT's detection capabilities for SCC in laboratory-degraded SG tubing in high temperature and high pressure aqueous environment.