• Title/Summary/Keyword: corrosion area

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A Flow Analysis in the surroundings of the Impingement Baffle of the Extracting Nozzle for Shell Wall Thinning of a Feedwater Heater (추기노즐 충격판 주변의 급수가열기 동체 감육에 대한 유동해석)

  • Jung, Sun-Hee;Kim, Kyung-Hoon
    • Proceedings of the KSME Conference
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    • 2007.05b
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    • pp.2977-2982
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    • 2007
  • Feedwater heaters of many nuclear power plants have recently experienced severe wall thinning damage, which will increase as operating time progresses. Several nuclear power plants in Korea have experienced wall thinning damage in the area around the impingement baffle - installed downstream of the high pressure turbine extraction steam line - inside number 5A and 5B feedwater heaters. At that point, the extracted steam from the high pressure turbine is two phase fluid at high temperature, high pressure, and high speed. Since it flows in reverse direction after impinging the impingement baffle, the shell wall of the number 5 high pressure feedwater heater may be affected by flow-accelerated corrosion. This paper describes the comparisons between the numerical analysis results using the FLUENT code and the down scale experimental data which effect on disclosing of the shell wall thinning of the high pressure feedwater heaters by porous plate.

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Evaluation of Strengthening Capacity of Deteriorated RC Beams using Finite Element Method (유한요소법에 의한 열화된 철근콘크리트 보의 보강성능평가)

  • 이창훈;송하원;변근주
    • Proceedings of the Korea Concrete Institute Conference
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    • 1999.04a
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    • pp.756-761
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    • 1999
  • The objective of this study is to develop finite element analysis technique to predict the strength reduction of deteriorated reinforced concrete beams and their strengthening capacity. In order to consider the effect of rebar corrosion, a tension stiffening model is proposed and area reduction of rebars due to corrosion is considered. For the analysis of strengthened deteriorated RC beams, one dimensional truss element and an interface element are introduced for models of the strengthening composite and the interface between concrete and composite to simulate delamination or discontinuous behavior at the interface. Then, analyses for deteriorated RC beams strengthened with glass fiber reinforced epoxy panel (GFREP) are carried out to predict both flexural failure and plate-end delamination failure. Finally, analysis results are verified with experimental results.

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Effect of Deicer on the Concrete and Steel (제설제가 콘크리트 및 강재에 미치는 영향)

  • Lee Byung Duck;Yun Byung Sung;Lee Chan Young;Chung Young Hwan
    • Proceedings of the Korea Concrete Institute Conference
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    • 2005.11a
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    • pp.375-378
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    • 2005
  • In this study, calcium chloride($CaCl_2$), sodium chloride (NaCl), organic acids-containing deicer(NS 40, NS 100), mixed deicier($NaCl\;70\%\;+\;CaCl_{2}\;30\%,\;NS\;40\;70\%\;+\;CaCl_{2}\;30\%,\;NaCl\;70\%\;+\;NS\;40\;30\%,\;NS\;40\;70\%\;+\;NaCl\;30\%$) is investigated based on the laboratory test for freez-thaw resistance of concrete and corrosion of metal. As a test results, in case of the use chloride-containing deicier in area that concrete structures has subjected to freez-thaw reaction in winter season, it showed desirable method that use deicing chemicals mixed with optimum ratio rather than use one deicing chemicals when is consider to deicing performance and effects, corrosion of steel materials, freez-thaw resistance of concrete. When use various deicing chemicals mixed, NS40($70\%$)+Calcium chloride($30\%$) showed the best effective method.

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Experimental Study on Bonding Properties of Reinforced Concrete with Water-Cement Ratio and Blending of Mineral Admixture (물-시멘트비 및 혼화재 혼입에 따른 철근콘크리트의 부착 특성에 관한 연구)

  • Choi, Yoon-Suk;Kim, Myung-Yu;Yang, Eun-Ik;Yi, Seong-Tae
    • Proceedings of the Korea Concrete Institute Conference
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    • 2006.05b
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    • pp.225-228
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    • 2006
  • To clarify the one body behavior of reinforcing bar and concrete, it is important to investigate bond characteristics between two materials. Bond strength is decided by applied force and interface area between reinforcing bar and concrete. And, the resultant force of chemical adhesive force, frictional force, and mechanical interaction are to be main factors. Property of concrete influences on chemical adhesive force and frictional force; bond strength is decreased by corrosion of reinforcing bar, as the result, durability is also decreased. In this study, to confirm bond characteristics with property of concrete, w/c ratio and blending of mineral admixture were selected as the main test parameters. The results obtained from this study will be used as the basic data for bond characteristics with corrosion.

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Development of Deterioration Detecting System for Aged ACSR-OC Conductors in HV Overhead Distribution Lines (고압 가공배전선의 노화된 ACSR-OC 도체에 대한 열화검출시스템 설계)

  • Kim, Sung-Duck;Lee, Seung-Ho
    • Proceedings of the KIEE Conference
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    • 2000.11a
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    • pp.232-235
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    • 2000
  • Design and experiments of a nondestructive system to inspect deterioration of ACSR-OC (ACSR Outdoor Cross-linked Polyethylene Insulated Wire usually used in HV overhead distribution lines presented in this paper. ACSR-OC conductor built to pollutants air for a long period would be easily progress to corrode so that it may lead to the reduction of the effective cross section area of conductors. A fault diagnosis system consisting of a solenoid sensor, a constant current source with RF frequency signal processing unit and a motor driver/controller designed and implemented. This instrument can dot the sensor output variation due to deterioration corrosion, continuously. As a result, it was shown such corrosion detector can readily be utilized estimating the diameter change due to deterioration overhead distribution lines and in giving an warning or inform before severe aged conductor lead to fail.

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The Novel Concepts for Reliability Technology

  • Ryu, DongSu
    • Corrosion Science and Technology
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    • v.4 no.5
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    • pp.201-206
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    • 2005
  • Starting with the meaning of the word quality, diverse concepts connoted by the term are examined. Instead of a bathtub curve, the desirable shape of a failure rate covering the entire life of a good product, which might be called hockey-stick line, is introduced. From the hockey-stick line and the definition of reliability, two measurements are extracted. The terms r-reliability (failure rate) and durability (product life) are explained. The conceptual analysis of failure mechanics explains that reliability technology pertains to design area. The desirable shape of hazard rate curve of electronic items, hockey-stick line, clarifies that Mean-Time-to-failure (MTTF) as the inverse of failure rate can be regarded a nominal life. And Bx life, different from MTTF, is explained. Reliability relationships between components and set products are explained. Reshaped definitions of r-reliability and durability are recommended. The procedure to improve reliability and the reasons for failing to identify failure mode are clarified in order to search right solutions. And generalized Life-Stress failure model is recommended for the calculation of acceleration factor.

THE APPLICATION OF ALUMINUM SHEET FOR THE PROTECTIVE HEAT SHIELD (ALLMINUM PROTECTIVE HEAT SHIELD 적용연구)

  • 이중윤;이호기;이경남
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 1996.10a
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    • pp.166-173
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    • 1996
  • There are kinds of materials for protective heat shield, i.e.Zn-coated steel, AI-coated steel and aluminum alloy sheets. This study compare formability, corrosion resistance, heat protectability, weight, and cost of these materials for heat protective shield. Generally aluminum alloy sheets are less formable than steel sheets, but A1100 alloy sheet shows almost same press quality of steel parts, using the press dies which producing steel parts. The heat shields using aluminum alloy sheet and steel sheet show almost same heat protectibility. It is the conclusion that Zn-coated merit, and AI-coated steel sheet and aluminum alloy sheet can be used to protect functional corrosion in severely corrosive market area. The material cost of AI-coated steel sheet and aluminum alloy sheet for a mid-size car is almost same, so aluminum alloy sheet is more recommendable in the point of weight reduction of vehicle.

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Bioinspired Nanoengineering of Multifunctional Superhydrophobic Surfaces

  • Choi, Chang-Hwan
    • Proceedings of the Korean Institute of Surface Engineering Conference
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    • 2015.11a
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    • pp.102-133
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    • 2015
  • Nature, such as plants, insects, and marine animals, uses micro/nano-textured surfaces in their components (e.g., leaves, wings, eyes, legs, and skins) for multiple purposes, such as water-repellency, anti-adhesiveness, and self-cleanness. Such multifunctional surface properties are attributed to three-dimensional surface structures with modulated surface wettability. Especially, hydrophobic surface structures create a composite interface with liquid by retaining air between the structures, minimizing the contact area with liquid. Such non-wetting surface property, so-called superhydrophobicity, can offer numerous application potentials, such as hydrodynamic drag reduction, anti-biofouling, anti-corrosion, anti-fogging, anti-frosting, and anti-icing. Over the last couple of decades, we have witnessed a significant advancement in the understanding of surface superhydrophobicity as well as the design, fabrication, and applications of superhydrophobic coatings/surfaces/materials. In this talk, the designs, fabrications, and applications of superhydrophobic surfaces for multifunctionalities will be presented, including hydrodynamic friction reduction, anti-biofouling, anti-corrosion, and anti-icing.

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Nanotube Morphology Change of Ti-6Al-4V Alloys by Heat Treatment

  • Kim, Sung-Hwan;Choe, Han-Cheol
    • Proceedings of the Korean Institute of Surface Engineering Conference
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    • 2013.05a
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    • pp.194-194
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    • 2013
  • In order to investigate nanotube morphology change of Ti-6Al-4V alloys by heat treatments, the Ti-6Al-4V alloys were used in this study. In non-treated Ti-6Al-4V alloy case, nanotubes only exhibited at ${\alpha}$ phase region with dissolved V-oxide area of ${\beta}$ phase. However, in Ti-6Al-4V alloy at $800^{\circ}C$ WQ case, nanotubes exhibited at both ${\alpha}$ and ${\beta}$ phase region. Electrochemical corrosion studies showed that the nanotubular alloy at $800^{\circ}C$WQ possesses slightly higher corrosion resistance than non-treated nanotubular alloy.

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Analysis of Local Wall Thinning around the Extraction Steam Entrance for the 6th Feedwater Heater Shell in the Nuclear Power Plants (원전 6단 급수가열기 추기증기 입구노즐 주변의 동체 국부 감육 원인 분석)

  • Song, Seok-Yoon;Kim, Hyung-Nam
    • The KSFM Journal of Fluid Machinery
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    • v.12 no.4
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    • pp.54-62
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    • 2009
  • The feedwater heaters are Critical components in a nuclear power plant. As the operation years of heaters go by, the maintenance costs required for continuous operation increase. When the carbon steel components in nuclear make contact with running fluid, the wall thinning caused by FAC (flow accelerated corrosion) can be generated. Local wall thinning is inevitable at the area around wet steam entrance to be attacked due to the long term operation. Sometimes the shell with thinned wall is eventually ruptured. To identify the relationship between the local wall thinning and fluid behavior of the feedwater heater, the practical data of a plant, which were based on ultrasonic thickness measurement tests, were analyzed and CFD(Computed Fluid Dynamics) analyses were performed.