• 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.

• Journal of the Society of Naval Architects of Korea
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• v.50 no.2
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• pp.104-110
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• 2013

In this paper, the design procedure and results for 'Residual Life Prediction System Considering Corrosion and Coating' are explained, which is one module of 'Life-cycle Management System of Ship and Offshore Plant's' Operation. This 'Residual Life Prediction System' has two main functions; one is residual life prediction function based on probability processing using corrosion measurement data of ship's major structural members, and another is rust rate prediction function based on visual image processing of inspection photos. The analysis of system user requirements and functions are introduced, and the structure and environment of the developed system are explained.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2001.05a
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• pp.213-218
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• 2001

These days, corrosion condition of a underground objects is measured by the electric potential between the subject and ground. But this method is implemented by means of manual work with analog voltmeter, which is uneconomic and inefficient. So, We developed real-time On-Line cathodic protection monitoring system that is able to detect corrosion potential conditions of metal objects or various steel structures in the ground continuously, display them with the graphic screen, construct a database, and analyze them simultaneously. Since the data of corrosion and corrosion protection of all underground objects is processed automatically, not manually in this system, It is possible to reduce the manipulated error, and perform precise safety management, maintenance and inspection. As as result, this system can not only guarantee long-life operation, reduction of manpower and cost, but prevent large accidents in advance.

• Corrosion Science and Technology
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• v.14 no.1
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• pp.1-11
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• 2015

Local wall thinning and integrity degradation caused by several mechanisms, such as flow accelerated corrosion (FAC), cavitation, flashing and/or liquid drop impingements, are a main concern in carbon steel piping systems of nuclear power plant in terms of safety and operability. Thinned pipe management program (TPMP) had been developed and optimized to reduce the possibility of unplanned shutdown and/or power reduction due to pipe failure caused by wall thinning in the secondary side piping system. This program also consists of several technical elements such as prediction of wear rate for each component, prioritization of components for inspection, thickness measurement, calculation of actual wear and wear rate for each component. Decision making is associated with replacement or continuous service for thinned pipe components. Establishment of long-term strategy based on diagnosis of plant condition regarding overall wall thinning is also essential part of the program. Prediction models of wall thinning caused by FAC had been established for 24 operating nuclear plants. Long term strategies to manage the thinned pipe component were prepared and applied to each unit, which was reflecting plant specific design, operation, and inspection history, so that the structural integrity of piping system can be maintained. An alternative integrity assessment criterion and a computer program for thinned piping items were developed for the first time in the world, which was directly applicable to the secondary piping system of nuclear power plant. The thinned pipe management program is applied to all domestic nuclear power plants as a standard procedure form so that it contributes to preventing an accident caused by FAC.

• Journal of the Korean Society for Heat Treatment
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• v.36 no.3
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• pp.153-160
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• 2023

The use of biogas is an industrially necessary means to achieve resource circulation. However, since biogas obtained from waste frequently causes corrosion in pipes, it is important to elucidate corrosion mechanisms of the pipes used for biogas transportation. Recently, corrosion failure occurred in a pipe which supplied for the biogas at the speed of 12.5 m/s. Pinholes and pits were found in a straight line along the seamline of the pipe. By using corrosion-damaged samples, residual thickness, microstructure, and composition of oxide film and inclusion were examined to analyze the cause of the failure. It was revealed that the thickness reduction of biogas pipe was ~0.11 mm per year. A thin sulfuric acid film was formed on the surface of the interior of a pipe due to moisture and hydrogen sulfide contained in a biogas. Near the seamline, microstructure was heterogeneous and manganese sulfide (MnS) was found. Pits were generated by micro-galvanic corrosion between the manganese sulfide and the matrix in the interior of the pipe along the seamline. In addition, microcracks formed along the grain boundaries beneath the pits revealed that hydrogen-induced cracking (HIC) also contributed to accelerating the pitting corrosion.

• Journal of Korean Society on Water Environment
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• v.28 no.4
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• pp.615-623
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• 2012

In this study, we evaluate the corrosion indexes (CI) such as Langelier Index (LI), Larson ratio (LR), Ryznar saturation index (RSI), Aggressiveness index (AI) of water quality for raw water, treated water and water in distribution reservoir at major eight drinking water treatment plants (DWTPs) in Korea. By analyzing secondary contamination of tap water, the variation of secondary contaminants was investigated with regard to pipe materials, aging and corrosion index (CI). In addition, we suggested an appropriate CI applicable water quality and the management plan for CI monitoriing. All CI showed corrosive water quality, and they did not change significantly in the distribution network. However, Copper (Cu), iron (Fe) and zinc (Zn) concentrations as secondary contaminants increased through the distribution network. Among CI, LI was most sensitive to changes in raw water quality and drinking water treatment. Also, it has high correlations with other indexes such as RSI, AI. Therefore, LI is considered as an appropriate CI to the domestic water quality. Based on these result, we propose LI as a drinking water quality standard to control the pipe corrosion from DWTPs.

• Environmental Engineering Research
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• v.14 no.3
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• pp.195-199
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• 2009

A series of laboratory-scale corrosion experiments was carried out to observe the effect of dissolved oxygen (DO) in the presence of other water quality parameters, such as hardness, Cl-, and pH using various pipe materials. In addition, a simulated loop system was installed at a water treatment plant for pilot-scale experiment. Laboratory-scale experiment showed that corrosion rates for galvanized steel pipe (GSP), carbon steel pipe (CSP), and ductile cast iron pipe (DCIP) were decreased to 72%, 75%, and 91% by reducing DO concentration from 9${\pm}$0.5 mg/L to 2${\pm}$0.5 mg/L. From the pilot scale experiment, it was further identified that the average ionization rate of zinc in GSP decreased from 0.00533 to 0.00078 mg/$cm^2$/d by controlling the concentration of DO. The reduction of average ionization rate for copper pipe (CP) and stainless steel pipe (SSP) were 71.4% for Cu and 63.5% for Fe, respectively. From this study, it was concluded that DO could be used as a major parameter in controlling the corrosion of water pipes.

• Structural Engineering and Mechanics
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• v.61 no.6
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• pp.693-700
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• 2017

Concrete cover cracking due to the corrosion of steel reinforcing bars is one of the main causes of deterioration in Reinforced Concrete (RC) structures. The oxidation level of the bars causes varying levels of expansion. The rebar expansions could lead to through-thickness cracking of the concrete cover, where depending on the cracking characteristics, the service life of the structures would be affected. In this paper, the effect of geometrical and material parameters, i.e., concrete cover thickness, reinforcing bar diameter, and concrete tensile strength, on the required pressure for concrete cover cracking due to corrosion has been investigated through detailed numerical simulations. ABAQUS finite element software is employed as a modeling platform where the concrete cracking is simulated by means of eXtended Finite Element Method (XFEM). The accuracy of the numerical simulations is verified by comparing the numerical results with experimental data obtained from the literature. Using a previously proposed empirical equation and the numerical model, the time from corrosion initiation to the cover cracking is predicted and then compared to the respective experimental data. Finally, a parametric study is undertaken to determine the optimum ratio of the rebar diameter to the reinforcing bars spacing in order to avoid concrete cover delamination.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.18 no.spc
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• pp.51-62
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• 2020

In this paper, an approach developed by the Finnish nuclear waste management organization, Posiva, for the construction license of a geological repository was reviewed. Furthermore, a computer program based on the approach was developed. By using the computer program, the lifetime of a copper disposal canister, which was a key engineered barrier of the geological repository, was predicted under the KAERI Underground Research Tunnel (KURT) geologic conditions. The computer program was developed considering the mass transport of corroding agents, such as oxygen and sulfide, through the buffer and backfill. Shortly after the closure of the repository, the corrosion depths of a copper canister due to oxygen in the pores of the buffer and backfill were calculated. Additionally, the long-term corrosion of a copper canister due to sulfide was analyzed in two cases: intact buffer and eroded buffer. Under various conditions of the engineered barrier, the corrosion lifetimes of the copper canister due to sulfide significantly exceeded one million years. Finally, this study shows that it is necessary to carefully characterize the transmissivity of rock and sulfide concentration during site characterization to accurately predict the canister lifetime.

• Corrosion Science and Technology
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• v.16 no.5
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• pp.235-240
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• 2017

Regional cathodic protection has significant impact on pipeline integrity management. After risk analyses of a newly built gas distribution station constructed in an area with large dwelling density, risk score was high because of potential threat caused by galvanic corrosion. Except reinforced steel in concrete, there are four kinds of metal buried under earth: carbon steel, galvanized flat steel, zinc rod and graphite module. To protect buried pipeline from external corrosion, design and construction of regional cathodic protection was proposed. Current density was measured with potential using potential dynamic test and boundary element method (BEM) was used to calculate current requirement and optimize best anode placement during design. From our calculation on the potential, optimized conditions for this area were that an applied current was 3A and anode was placed at 40 meters deep from the soil surface. It results in potential range between $-1.128V_{CSE}$ and $-0.863V_{CSE}$, meeting the $-0.85V_{CSE}$ criterion and the $-1.2V_{CSE}$ criterion that no potential was more negative than $-1.2V_{CSE}$ to cause hydrogen evolution at defects in coating of the pipeline.