• Title/Summary/Keyword: primary water

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PWSCC and System Engineering Development of Internal Inspection and Maintenance Methodology for RCS

  • Abdallah, Khaled Atya Ahmed;Mesquita, Patricia Alves Franca de;Yusoff, Norashila;Nam, GungIhn;Jung, JaeCheon;Lee, YoungKwan
    • Journal of the Korean Society of Systems Engineering
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    • v.12 no.1
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    • pp.89-103
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    • 2016
  • Due to safety of the plant, it became very clear the importance of study occurrence reactor coolant system (RCS) issues specially the primary water stress corrosion cracking (PWSCC). The Systems Engineering (SE) approach is characterized by the application of a structured engineering methodology for the design of a complex system or component. Robotic devices have been used for internal inspection, maintenance and performing remote welding and inspection in high-radiation areas. In this paper, PWSCC overview and inlay and over lay welding methodology introduced, concept of robotic device that can be inserted into the piping via Steam Generator (SG) main way to access to primary piping of pressurized water reactor (PWR) is developed based on SE methodology. A 3D model of the inspection system was developed along with the APR1400 (Advanced Power Reactor)reactor coolant systems (RCS) and internals with virtual 3D simulation of the operation for visualization to prove the validity of the concept.

ENHANCED ARCTIC PRIMARY PRODUCTIVITY FOLLOWING SEA ICE RAPID DECLINE

  • Comiso, Josefino C.
    • Proceedings of the KSRS Conference
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    • v.2
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    • pp.1019-1022
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    • 2006
  • Satellite sea ice data from 1978 to the present reveal that the perennial ice (or ice that survives the summer) has been rapidly declining at almost 10% per decade. Warming due to increases in greenhouse gases in the atmosphere is now also being reflected in winter with drastic reductions in the maximum extent observed in 2005 and 2006. The retreat of the perennial ice also exposes more open water and has revealed an asymmetric distribution of chlorophyll a pigment concentration in the Arctic basin. Phytoplankton blooms are most dominant at high latitudes, partly on account of sea ice, but in the Arctic basin, it appears that pigment concentrations in the Eastern (Laptev Sea) Region are on the average three times higher than those in the Western (Beaufort Sea) Region. Such asymmetry suggests that despite favorable conditions provided by the melt of sea ice, there are other factors that affects the productivity of the region. The asymmetry is likely associated with much wider shelf areas in the East than in the West, with sea ice processes that inhibits the availability of nutrients near the surface in deep water regions, and river run-off that affects nutrient availability. The primary productivity in the pan-Arctic region have been estimated using the pigment concentrations and PAR derived from SeaWiFS data and the results show large seasonal as well as interannual variability during the 1998 to 2005 period. The data points towards increasing productivity for later years but with only 9 years of data it is too early to tell the overall effect of the sea ice retreat.

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A Study on Linear Energy Transfer and Specific Primary lonizaton for Charged Particles Incident on Water (대전 입자들의 초기 이온화비에 관한 연구 I)

  • 남궁미선;김부길;김정홍
    • Progress in Medical Physics
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    • v.6 no.1
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    • pp.39-47
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    • 1995
  • In order to accurate treat damage induced by ionizing radiation in biological system on the cellular or subcellular level with physical parameters characterising the radiation, specific primary ionization (SPI) is introduced as the parameter which does not suffer from limitation of linear energy transfer (LET). In this present study, we calculate specitic primayt ionization with total ionization cross section (TICS) of electrons, protons and alppa particles incident on water. The used energy ranges cover those that have been freqently used in radiobioligical experiments. For electrons above 1 keV, we have relativistic corrections and also compare the results with other data. For electrons energies below 100keV, our results are in excellent agreement with theoretical calculations published recently by (perris and zarris 1987). These results may be easily applied by the interested radiobiogists.

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A Numerical Study On Various Energy and Environmental Systems(Ⅰ) : LPG dispersion, Lake flow, Primary clarifier, Hood ventilation, Cyclone combustor, Dow chlorination reactor. (에너지$\cdot$환경 제반 시스템에 관한 수치 해석적 연구 (Ⅰ) : LPG 확산, 호소 유동, 일차침전조, 국소 환기용 후두, 싸이클론 연소로, Dow 화학 반응로)

  • Jang Dong-Sun;Kim Gyeong-Mi;Lee Eun-Ju;Park Byeong-Su;Kim Bok-Sun
    • Journal of computational fluids engineering
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    • v.2 no.1
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    • pp.93-108
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    • 1997
  • This paper describes several computational results on the various energy and environmental problems using Patankar's SIMPLE method. The specific problems included in this study are : pollutant and flammable material dispersions in open and confined areas, buoyancy-driven flow in a lake, primary clarifier for water and waste water treatment, hood ventilation in workplace. cyclone combustor and Dow chlorination reactor. A control-volume based finite-difference method is employed together with the power-law scheme. The pressure-velocity coupling is resolved by the use of the revised version of SIMPLE, says SIMPLER and SIMPLEC. The Reynolds stresses are closed using the standard or RNG κ-ε models. A nonequilibrium turbulent reaction model is developed for the application of the chlorination process in the Dow thermal reactor. Other important empirical models and physical insights appeared in this study are presented and discussed in a brief note. The computational method developed in this study is considered, in general, as a viable tool for the design and determination of the optimal operating condition of various environmental engineering system of interest.

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Prediction of Welding Residual Stress of Dissimilar Metal Weld of Nozzle using Finite Element Analyses (유한요소해석을 이용한 노즐 이종금속용접부의 용접잔류응력 예측)

  • Huh, Nam-Su;Kim, Jong-Wook;Choi, Suhn;Kim, Tae-Wan
    • Proceedings of the KSME Conference
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    • 2008.11a
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    • pp.83-84
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    • 2008
  • The primary water stress corrosion cracking (PWSCC) of dissimilar metal weld based on Alloy 82/182 is one of major issues in material degradation of nuclear components. It is well known that the crack initiation and growth due to PWSCC is influenced by material's susceptibility to PWSCC and distribution of welding residual stress. Therefore, modeling the welding residual stress is of interest in understanding crack formation and growth in dissimilar metal weld. Currently in Korea, a numerical round robin study is undertaken to provide guidance on the welding residual stress analysis of dissimilar metal weld. As a part of this effort, the present paper investigates distribution of welding resisual stress of a ferritic low alloy steel nozzle with dissimilar metal weld using Alloy 82/182. Two-dimensional thermo-mechanical finite element analyses are carried out to simulate multi-pass welding process on the basis of the detailed design and fabrication data. The present results are compared with those from other participants, and more works incorporating physical measurements are going to be performed to quantify the uncertainties relating to modelling assumptions.

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Failure Analysis of Top Nozzle Holddown Spring Screw for Nuclear Fuel Assembly (핵연료상단고정체 누름스프링 체결나사의 파손해석)

  • Koh, S.K.;Ryu, C.H.;Lee, Jeong-Jun;Na, E.G.;Baek, T.H.;Jeon, K.L.
    • Proceedings of the KSME Conference
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    • 2003.11a
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    • pp.1234-1239
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    • 2003
  • A failure analysis of holddown spring screw was performed using fracture mechanics approach. The spring screw was designed such that it was capable of sustaining the loads imposed by the initial tensile preload and operational loads. In order to investigate the cause of failure, a stress analysis of the top nozzle spring assembly was done using finite element analysis and a life prediction of the screw was made using a fracture mechanics approach. The elastic-plastic finite element analysis showed that the local stresses at the critical regions of head-shank fillet and thread root significantly exceeded than the yield strength of the screw material, resulting in local plastic deformation. Primary water stress corrosion cracking life of the Inconel 600 screw was predicted by using integration of the Scott model and resulted in 1.42 years, which was fairly close to the actual service life of the holddown spring screw.

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Determination of Optimal Coagulation Condition for Coagulation-UF Water Treatment Process (응집-UF 정수공정을 위한 칠적응집조건의 결정)

  • Lee, Chul-Woo;An, Su-Kyong;Kang, Lim-Seok
    • Journal of Korean Society of Environmental Engineers
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    • v.27 no.8
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    • pp.799-806
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    • 2005
  • Applying coagulation process before membrane filtration showed not only reducing membrane fouling, but also improving the removal of dissolved organic materials that might otherwise not be removed by the membrane alone. Also, slow mixing didn't affect the reduction of membrane fouling, and rapid mixing using an in-line static mixer was more effective than using backmixer. In addition, only 11 percent of dissolved organic matter in raw water was the primary cause of fouling. Furthermore, tile primary foulant of UF membrane was hydrophobic substance, which can easily be removed by coagulation.

A Study of Residual Stress Measurement in the Weld of Nuclear Materials (원전재료 모재 및 용접부 잔류응력측정 연구)

  • Lee, Kyoung-Soo;Lee, Jeong-Keun;Lee, Seong-Ho;Park, Jae-Hak
    • Transactions of the Korean Society of Pressure Vessels and Piping
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    • v.7 no.1
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    • pp.9-16
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    • 2011
  • Primary water stress corrosion cracking (PWSCC) has been found in the weld region of the nuclear power plant. Welding can produce tensile residual stress. Tensile residual stress contributes to the initiation and growth of PWSCC. It is important to estimate weld residual stress accurately to predict or prevent the initiation and growth of PWSCC. This paper shows the results of finite element analysis and measurement experiment for weld residual stress. For the study, four kinds of specimen were fabricated with the materials used in the nuclear power plant. Residual stresses were measured by four kinds of methods of hole drilling, x-ray diffraction, instrumented indentation and sectioning. Through the study, numerical analysis and measurement results were compared and the characteristics of each measurement technique were observed.

ROLE OF GRAIN BOUNDARY CARBIDES IN CRACKING BEHAVIOR OF Ni BASE ALLOYS

  • Hwang, Seong Sik;Lim, Yun Soo;Kim, Sung Woo;Kim, Dong Jin;Kim, Hong Pyo
    • Nuclear Engineering and Technology
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    • v.45 no.1
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    • pp.73-80
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    • 2013
  • The primary water stress corrosion cracking (PWSCC) of Alloy 600 in a PWR has been reported in the control rod drive mechanism (CRDM), pressurizer instrumentation, and the pressurizer heater sleeves. Recently, two cases of boric acid precipitation that indicated leaking of the primary cooling water were reported on the bottom head surface of steam generators (SG) in Korea. The PWSCC resistance of Ni base alloys which have intergranular carbides is higher than those which have intragranular carbides. Conversely, in oxidized acidic solutions like sodium sulfate or sodium tetrathionate solutions, the Ni base alloys with a lot of carbides at the grain boundaries and shows less stress corrosion cracking (SCC) resistance. The role of grain boundary carbides in SCC behavior of Ni base alloys was evaluated and effect of intergranular carbides on the SCC susceptibility were reviewed from the literature.

Design of an Organic Simplified Nuclear Reactor

  • Shirvan, Koroush;Forrest, Eric
    • Nuclear Engineering and Technology
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    • v.48 no.4
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    • pp.893-905
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    • 2016
  • Numerous advanced reactor concepts have been proposed to replace light water reactors ever since their establishment as the dominant technology for nuclear energy production. While most designs seek to improve cost competitiveness and safety, the implausibility of doing so with affordable materials or existing nuclear fuel infrastructure reduces the possibility of near-term deployment, especially in developing countries. The organic nuclear concept, first explored in the 1950s, offers an attractive alternative to advanced reactor designs being considered. The advent of high temperature fluids, along with advances in hydrocracking and reforming technologies driven by the oil and gas industries, make the organic concept even more viable today. We present a simple, cost-effective, and safe small modular nuclear reactor for offshore underwater deployment. The core is moderated by graphite, zirconium hydride, and organic fluid while cooled by the organic fluid. The organic coolant enables operation near atmospheric pressure and use of plain carbon steel for the reactor tank and primary coolant piping system. The core is designed to mitigate the coolant degradation seen in early organic reactors. Overall, the design provides a power density of 40 kW/L, while reducing the reactor hull size by 40% compared with a pressurized water reactor while significantly reducing capital plant costs.