• Title/Summary/Keyword: Downcomer

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Scaling Analysis of Thermal Hydraulics Phenomena in the Nuclear Reactor Vessel Downcomer during the Reflood Phase of LBLOCA (대형냉각재 상실사고 재관수 기간 동안, 차세대 원자로 강수부 내의 열수력 현상 모의를 위한 실험장치 척도해석)

  • Yun, B.J.;Song, C.H.;Kwon, T.S.;Euh, D.J.;Chu, I.C.;Yoon, Y.J.
    • Proceedings of the KSME Conference
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    • 2001.06d
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    • pp.821-827
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    • 2001

  • As one of the advanced design features of the Korea next generation reactor, direct vessel injection (DVI) system is being considered instead of conventional cold leg injection (CLl) system. It is known that the DVI system greatly enhances the reliability of the emergency core cooling (ECC) system. However, there is still a dispute on its performance in terms of water delivery to the reactor core during the reflood period of a large-break loss-of-coolant accident (LOCA). Thus, experimental validation is under progress. In this paper, a new scaling method, using time and velocity reduced linear scaling law, is suggested for the design of a scaled-down experimental facility to investigate the direct ECC bypass phenomena in PWR downcomer.

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Direct ECC Bypass Phenomena in the MIDAS Test Facility During LBLOCA Reflood Phase

  • B.J. Yun;T.S. Kwon;D.J. Euh;I.C. Chu;Park, W.M.;C.H. Song;Park, J.K.
    • Nuclear Engineering and Technology
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    • v.34 no.5
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    • pp.421-432
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    • 2002

  • As one of the advanced design features of the APR1400, direct vessel injection (DVI) system is being considered instead of conventional cold leg injection (CLI) system. It is known that the DVI system greatly enhances the reliability of the emergency core cooling (ECC) system. However, there is still a dispute on its performance in terms of water delivery to the reactor core during the reflood phase of a large-break loss-of-coolant accident (LOCA). Thus, experimental validation is under progress. In this paper, test results of direct ECC bypass performed in the steam-water test facility tailed MIDAS (Multi-dimensional Investigation in Downcomer Annulus Simulation) are presented. The test condition is determined, based on the preliminary analysis of TRAC code, by applying the ‘modified linear scaling method’with the l/4.93 length scale . From the tests, ECC direct bypass fraction, steam condensation rate and information on the flow distribution in the upper annulus downcomer region are obtained.

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MODELING OF A BUOYANCY-DRIVEN FLOW EXPERIMENT IN PRESSURIZED WATER REACTORS USING CFD-METHODS

  • Hohne, Thomas;Kliem, Soren
    • Nuclear Engineering and Technology
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    • v.39 no.4
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    • pp.327-336
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    • 2007

  • The influence of density differences on the mixing of the primary loop inventory and the Emergency Core Cooling (ECC) water in the downcomer of a Pressurised Water Reactor (PWR) was analyzed at the ROssendorf COolant Mixing (ROCOM) test facility. ROCOM is a 1:5 scaled model of a German PWR, and has been designed for coolant mixing studies. It is equipped with advanced instrumentation, which delivers high-resolution information for temperature or boron concentration fields. This paper presents a ROCOM experiment in which water with higher density was injected into a cold leg of the reactor model. Wire-mesh sensors measuring the tracer concentration were installed in the cold leg and upper and lower part of the downcomer. The experiment was run with 5% of the design flow rate in one loop and 10% density difference between the ECC and loop water especially for the validation of the Computational Fluid Dynamics (CFD) software ANSYS CFX. A mesh with two million control volumes was used for the calculations. The effects of turbulence on the mean flow were modelled with a Reynolds stress turbulence model. The results of the experiment and of the numerical calculations show that mixing is dominated by buoyancy effects: At higher mass flow rates (close to nominal conditions) the injected slug propagates in the circumferential direction around the core barrel. Buoyancy effects reduce this circumferential propagation. Therefore, density effects play an important role during natural convection with ECC injection in PWRs. ANSYS CFX was able to predict the observed flow patterns and mixing phenomena quite well.

  • https://doi.org/10.5516/NET.2007.39.4.327 인용 PDF KSCI

최적 노심입구온도 분포모형을 이용한 고리 1호기 주증기관 파단사고 분석

  • 엄길섭;이병일;김정진;김희철;박군철
    • Proceedings of the Korean Nuclear Society Conference
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    • 1996.05b
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    • pp.556-561
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    • 1996

  • 주증기관 파단사고가 발생하여 서로 다른 온도 및 유속을 갖는 냉각재가 원자로 용기에 유입 될 때 downcomer 및 lower plenum 에서의 혼합현상을 3차원 열수력 분석코드 COMMIX-lB［1］로 모사하여 노심입구에서의 온도분포를 결정하고, 결정된 온도분포를 이용하여 주증기관 파단사고에 대한 열적여유도를 분석하였다. 분석은 주증기관 파단사고시 노심입구온도의 비대칭성이 가장 큰 고리 1호기를 선택하여 수행되었으며, 15주기 교체노심 설계 결과와 비교하여 열적 여유도가 다소 증가함을 확인하였다.

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