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  • Page : 33 - 39 DOWNLOAD
  • 원전 배관의 두께 측정 데이터에 대한 신뢰도 분석 방법 및 적용
  • Pipe wall-thinning by flow-accelerated corrosion and various types of erosion is significant damage in secondary system piping of nuclear power plants(NPPs). All NPPs in Korea have management programs to ensure pipe integrity from degradation mechanisms. Ultrasonic test(UT) is widely used for pipe wall thickness
    measurement. Numerous UT measurements have been performed during scheduled outages. Wall-thinning rates are determined conservatively according to several evaluation methods developed by Electric Power Research Institute(EPRI). The issue of reliability caused by measurement error should be considered in the process of evaluation. The reliability analysis method was developed for single and multiple measurement data in the previous researches. This paper describes the application results of reliability analysis method to real measurement data during scheduled outage and proved its benefits.
  • KEYWORDs : wall thinning, ultrasonic thickness measurement, reliability analysis
  • AUTHORs : 윤 훈·황 경 모·이 효 승·문 승 재†
  • Page : 25 - 32 DOWNLOAD
  • 탄소강의 유동가속부식에 미치는 크롬의 영향
  • The alloy content of structural materials of nuclear power plants has been recognized an important factor in predicting flow accelerated corrosion (FAC). In particular, many literature data reported that chromium content is one of the most important alloying element and even a small amount of chromium is effective
    to suppress FAC. This report reviewed and compared chromium models of Ducreux, Bouchacourt, and Kastner which were used in predicting FAC rates. The plant data indicate that Ducreux model may be conservative for the specimen containing 0.15 wt% chromium. The related articles were reviewed as follows. Combined effects of chromium content, pH, temperature, dissolved oxygen (DO), flow velocity, test time,
    and kinds of amine on the FAC rate were described. 0.1 wt% chromium in steel did not affect the FAC rate with changes in pH. The FAC rates pronounced with higher flow rate and increased with increasing test duration(600 d) for 0.013 wt% chromium. The FAC rates in mixed amine chemistry were higher than in ammonia chemistry, which may be lessened by the addition of chromium to the steel.
  • KEYWORDs : flow accelerated corrosion, nuclear power plant, environmental factors, Cr, pH
  • AUTHORs : 이 은 희·김 경 모·김 홍 표·김 동 진
  • Page : 19 - 24 DOWNLOAD
  • 마그네타이트 (Fe₃O₄) 전극의 제조와 전기화학 특성
  • Flow Accelerated Corrosion (FAC) causes unexpected accidents in a secondary side of a nuclear power plant. The secondary side pipes are mainly carbon steel tubes that have a protective magnetite (Fe₃O₄) layer on the inner surface. The stability of the protective magnetite layer depends on the parameters related
    to the FAC phenomena such as pH, temperature, flow rate, surface roughness etc. The dissolution of magnetite is basically the electrochemical reaction, but the most of the experiments of magnetite dissolution were carried out thermodynamically to determine the solubility of magnetite. The knowledge of the electrochemical
    properties of magnetite is required to understand the dissolution process of magnetite. This paper reviews the manufacture of the magnetite (Fe₃O₄) electrode, and summaries the electrochemical properties of the magnetite.
  • KEYWORDs : magnetite, Fe3O4, electrode, electrochemical property, solubility
  • AUTHORs : 김 명 진†·김 동 진·김 홍 표
  • Page : 12 - 18 DOWNLOAD
  • REAL-TIME CORROSION CONTROL SYSTEM FOR CATHODIC PROTECTION OF BURIED PIPES FOR NUCLEAR POWER PLANT
  • Since the operation period of nuclear power plants has increased, the degradation of buried pipes gradually increases and recently it seems to be one of the emerging issues. Maintenance on buried pipes needs high quality of management system because outer surface of buried pipe contacts the various soils but inner surface reacts with various electrolytes of fluid. In the USA, USNRC and EPRI have tried to manage the degradation of buried pipes. However, there is little knowledge about the inspection procedure, test and manage program in the domestic nuclear power plants. This paper focuses on the development and build-up of real-time monitoring and control system of buried pipes. Pipes to be tested are tape-coated carbon steel
    pipe for primary component cooling water system, asphalt-coated cast iron pipe for fire protection system, and pre-stressed concrete cylinder pipe for sea water cooling system. A control system for cathodic protection was installed on each test pipe which has been monitored and controlled. For the calculation of protection
    range and optimization, computer simulation was performed using COMSOL Multiphysics (Altsoft co.).
  • KEYWORDs : nuclear power plant, buried pipe, cathodic protection, design, computer simulation
  • AUTHORs : Ki Tae Kim, Hae Woong Kim, Young Sik Kim,†, Hyun Young Chang, Bu Taek Lim, and Heung Bae Park
  • Page : 1 - 11 DOWNLOAD
  • THINNED PIPE MANAGEMENT PROGRAM OF KOREAN NUCLEAR POWER PLANTS
  • 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.
  • KEYWORDs : flow accelerated corrosion, wall thinning, prediction model, integrity assessment
  • AUTHORs : S. H. Lee†, Y. S. Lee, S. K. Park, and J. G. Lee