• Title/Summary/Keyword: Core inlet

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DNBR Sensitivities to Variations in PWR Operating Parameters (가압경수로의 운전변수 변화에 대한 DNBR의 민감도)

  • Hyun Koon Kim;Ki In Han
    • Nuclear Engineering and Technology
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    • v.15 no.4
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    • pp.236-247
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    • 1983
  • Analyzed are the the DNBR(Departure from Nucleate Boiling Ratio) sensitivities to variations in various PWR operating parameters utilizing the Korea Nuclear Unit 1(KNU-1) design and operating data. Studied parameters in the analysis are core power level, system pressure, core inlet flow rate, core inlet temperature, enthalpy rise hot channel factor, and axial power peaking factor and axial offset. The calculations are performed using the steady state and transient thermal-hydraulics computer program, COBRA-IV-K, which is the revised version of COBRA-IV-i that has been adapted, partially modified and verified at KAERI. A reference case is established based on the design and operating condition of the KNU-1 reactor core, and this provides a basis for the subsequent sensitivity analysis. From the calculation results it is concluded that the most sensitive parameter in the DNBR thermal design is the coolant core inlet temperature while the axial power peaking factor is the least sensitive.

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The Analytic Analysis of Suppressing Jet Flow at Guide Tube of Circular Irradiation Hole in HANARO (하나로 원형 조사공의 안내관 제트유동 억제에 대한 해석)

  • Park Y. C.;Wu S. I.
    • 한국전산유체공학회:학술대회논문집
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    • 2004.03a
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    • pp.214-219
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    • 2004
  • The HANARO, a multi-purpose research reactor of 30 MWth, open-tank-in-pool type, has been under normal operation since its initial criticality in February, 1995. The HANARO is composed of inlet plenum, grid plate, core channel with flow tubes and chimney. The reactor core channel is located at about twelve m (12 m) depth of the reactor pool and cold by the upward flow that the coolant enters the lower inlet of the plenum, rises up through the grid plate and the core channel and exit through the outlet of chimney. A guide tube is extended from the reactor core to the top of the reactor chimney for easily un/loading a target under the reactor normal operation. But active coolant through the core can be Quickly raised up to the top of the chimney through the guide tube by jet flow. This paper is described an analytical analysis to study the flow behavior through the guide tube under reactor normal operation and unloading the target. As results, it was conformed through the analysis results that the flow rate, about fourteen kilogram per second (14 kg/s) suppressed the guide tube jet and met the design cooling flow rate in a circular flow tube, and that the fission moly target cooling flow rate met the minimum flow rate to cool the target.

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THE ANALYTIC ANALYSIS OF SUPPRESSING JET FLOW AT GUIDE TUBE OF CIRCULAR IRRADIATION HOLE IN HANARO (하나로 원형 조사공의 안내관 제트유동 억제에 대한 해석)

  • Park Y.C.;Wu S.I.
    • Journal of computational fluids engineering
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    • v.10 no.2
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    • pp.1-6
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    • 2005
  • The HANARO, a multi-purpose research reactor of 30 MWth, open-tank-in-pool type, has been under normal operation since its initial criticality in February, 1995. The HANARO is composed af inlet plenum, grid plate, core channel with flow tubes and chimney. The reactor core channel is located at about twelve meters (12 m) depth of the reactor pool and cooled by the upward flow that the coolant enters the lower inlet of the plenum, rises up through the grid plate and the core channel and comes out from the outlet of chimney. A fission moly guide tube is extended from the reactor core to the top of the reactor chimney for easily loading a fission moly target under the reactor normal operation. But active coolant through the core can be quickly raised up to the top of the chimney through the guide tube by jet flow. This paper describes an analytical analysis that is the study of the flow behavior through the guide tube under reactor normal operation and unloading the target. As results, it was conformed through the analysis results that the flow rate, reduced to about fourteen kilogram per second (14 kg/s) from the original flow rate of sixteen point three kilogram per second (16.3 kg/s) did not show the guide tube jet.

ASSESSMENT OF CORE BYPASS FLOW IN A PRISMATIC VERY HIGH TEMPERATURE REACTOR BY USING UNIT-CELL EXPERIMENT AND CFD ANALYSIS (단위-셀 실험과 전산유체해석을 통한 블록형 초고온가스로의 노심우회유량 평가)

  • Yoon, S.J.;Jin, C.Y.;Kim, M.H.;Park, G.C.
    • Journal of computational fluids engineering
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    • v.14 no.2
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    • pp.59-67
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    • 2009
  • An accurate prediction of the bypass flow is of great importance in the VHTR core design concerning the fuel thermal margin. Nevertheless, there has not been much effort in evaluating the amount and the distribution of the core bypass flow. In order to evaluate the behavior and the distribution of the coolant flow, a unit-cell experiment was carried out. Unit-cell is the regular triangular section which is formed by connecting the centers of three hexagonal blocks. Various conditions such as the inlet mass flow rate, block combinations and the size of bypass gap were examined in the experiment. CFD analysis was carried out to analyze detailed characteristics of the flow distribution. Commercial CFD code FLUENT 6.3 was validated by comparing with the experimental results. In addition, SST model and standard k-$\varepsilon$ model were validated. The results of CFD simulation show good agreements with the experimental results. SST model shows better agreement than standard k-$\varepsilon$ model. Results showed that block combinations and the size of the bypass gap have an influence on the bypass flow ratio but the inlet mass flow rate does not.

Flow Characteristics for Guide Tube of Circular Irradiation Hole in HANARO (하나로 원형 조사공의 안내관 유동특성)

  • Park, Y.C.;Wu, J.S.
    • Proceedings of the KSME Conference
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    • 2004.04a
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    • pp.1835-1840
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    • 2004
  • The HANARO, a multi-purpose research reactor of 30 MWth, open-tank-in-pool type, has been under normal operation since its initial criticality in February, 1995. The HANARO is composed of inlet plenum, grid plate, core channel with flow tubes and chimney. The reactor core channel is located at about twelve meters (12 m) depth of the reactor pool and cooled by the upward flow that the coolant enters the lower inlet of the plenum,. rises up through the grid plate and the core channel and comes out from the outlet of chimney. A guide tube is extended from the reactor core to the top of the reactor chimney for easily un/loading a target under the reactor normal operation. But active coolant through the core can be quickly raised up to the top of the chimney through the guide tube by a jet flow. This paper describes an analytical analysis that is the study of the flow behavior through the guide tube under reactor normal operation and unloading the target. As results, it was conformed through the analysis results that the guide jet is suppressed under the top of the chimney after modifying the orifice diameter of 37.5 mm to 31 mm.

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Effects of the Inlet Boundary Layer Thickness on the Loss Mechanism in an Axial Compressor (입구 경계층 두께가 축류 압축기 손실에 미치는 영향)

  • Choi, Minsuk;Baek, Jehyun
    • 유체기계공업학회:학술대회논문집
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    • 2004.12a
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    • pp.419-426
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    • 2004
  • A three-dimensional computation was conducted to understand effects of the inlet boundary layer thickness on the loss mechanism in a low-speed axial compressor operating at the design condition(${\phi}=85\%$) and near stall condition(${\phi}=65\%$). At the design condition, the flow phenomena such as the tip leakage flow and hub comer stall are similar independent of the inlet boundary layer thickness. However, when the axial compressor is operating at the near stall condition, the large separation on the suction surface near the casing is induced by the tip leakage flow and the boundary layer on the blade for thin inlet boundary layer but the hub corner stall is enlarged for thick inlet boundary layer. These differences of internal flows induced by change of the boundary layer thickness on the casing and hub enable loss distributions of total pressure to be altered. When the axial compressor has thin inlet boundary layer, the total pressure loss is increased at regions near both casing and tip but decreased in the core flow region. In order to analyze effects of inlet boundary layer thickness on total loss in detail, using Denton's loss models, total loss is scrutinized through three major loss categories in a subsonic axial compressor such as profile loss, tip leakage loss and endwall loss.

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Numerical Analysis of the Effect of Hole Size Change in Lower-Support-Structure-Bottom Plate on the Reactor Core-Inlet Flow-Distribution (하부지지구조물 바닥판 구멍크기 변경이 원자로 노심 입구 유량분포에 미치는 영향에 관한 수치해석)

  • Lee, Gong Hee;Bang, Young Seok;Cheong, Ae Ju
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.39 no.11
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    • pp.905-911
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    • 2015
  • In this study, to examine the effect of a hole size change(smaller hole diameter) in the outer region of the lower-support-structure-bottom plate(LSSBP) on the reactor core-inlet flow-distribution, simulations were conducted with the commercial CFD software, ANSYS CFX R.15. The predicted results were compared with those of the original LSSBP. Through these comparisons, it was concluded that a more uniform distribution of the mass flow rate at the core-inlet plane could be obtained by reducing the hole size in the outer region of the LSSBP. Therefore, from the nuclear regulatory perspective, design change of the hole pattern in the outer region of the LSSBP may be desirable in terms of improving both the mechanical integrity of the fuel assembly and the core thermal margin.

Numerical Analysis for the Effect of Flow Skirt Geometry on the Flow Distribution in the Scaledown APR+ (유동 덮개 형상이 축소 APR+ 내부 유동분포에 미치는 영향에 대한 수치해석)

  • Lee, Gong Hee;Bang, Young Seok;Woo, Sweng Woong;Kim, Do Hyeong;Kang, Min Ku
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.25 no.5
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    • pp.269-278
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    • 2013
  • In this study, in order to examine the applicability of computational fluid dynamics with the porous model to the analysis of APR+ (Advanced Power Reactor Plus) internal flow, simulation was conducted with the commercial multi-purpose computational fluid dynamics software, ANSYS CFX V.14. In addition, among the various reactor internals, the effect of flow skirt geometry on reactor internal flow was investigated. It was concluded that the porous model for some reactor internal structures could adequately predict the hydraulic characteristics inside the reactor in a qualitative manner. If sufficient computation resource is available, the predicted core inlet flow distribution is expected to be more accurate, by considering the real geometry of the internal structures, especially located in the upstream of the core inlet. Finally, depending on the shape of the flow skirt, the flow distribution was somewhat different locally. The standard deviation of the mass flow rate (${\sigma}$) for the original shape of flow skirt was smaller, than that for the modified shape of flow skirt. This means that the original shape of the flow skirt may give a more uniform distribution of mass flow rate at the core inlet plane, which may be more desirable for the core cooling.

A Study about Flow Characteristics of Impinging Jet for Thermal Control (I) (전열제어를 위한 충돌제트의 유동특성에 관한 연구(I))

  • 김동균;김정환;배석태;김시범;이영호
    • Journal of Advanced Marine Engineering and Technology
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    • v.25 no.6
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    • pp.1330-1335
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    • 2001
  • A present study is the flow characteristics of impinging jet by PIV measurement and numerical analysis. The flow characteristics of impinging jet flow are affected greatly by nozz1e inlet velocity An circular sharp edged nozzle type($45^{\circ}$ ) was used to achieve uniform mean velocity at the nozz1e inlet, and its diameter is 10 mm(d). Therefore, the flow characteristics on the impinging jet can be changed largely by the control of main flow In this parent study, we investigate the effects of inlet velocity, its variable is nozzle inlet Reynolds numbers (Re=1500, 3000, 4500, 6000 and 7500)

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A Study about Flow Characteristics of Impinging Jet for Thermal Control (전열제어를 위한 충돌제트의 유동특성에 관한 연구)

  • 김동균;김정환;배석태;김시범;이영호
    • Proceedings of the Korean Society of Marine Engineers Conference
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    • 2001.05a
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    • pp.34-39
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    • 2001
  • A present study is the flow characteristics of impinging jet by PIV measurement and numerical analysis. The flow characteristics of impinging jet flow are affected greatly by nozzle inlet velocity. An circular sharp edged nozzle type($45^{\circ}$) was used to achieve uniform mean velocity at the nozzle inlet, and its diameter is 10mm(d). Therefore, the flow characteristics on the impinging jet can be changed largely by the control of main flow. In this parent study, we investigate the effects of inlet velocity, its variable is nozzle inlet Reynolds numbers(Re=1500m 3000, 4500, 6000 and 7500)

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