Research Highlight
Total : 36
게시물 검색
  • 21
    • NUCLEAR SAFETY AND ENERGY CONVERSION Steam explosion   2017.02.07
        Steam explosion is one of the risk significant phenomena at the severe accident. It often occurs if hot liquid material comes into contact with cold coolant and the coolant boils at a local area of hot liquid-coolant interaction producing rapid vapor generation. The steam explosion is developed following four steps: premixing, triggering, propagation, and expansion. 
  • 20
    • NUCLEAR SAFETY AND ENERGY CONVERSION Melt jet breakup   2017.02.07
      In severe accident, the ex-vessel corium coolability is one of risk-significant issues and there are still significant uncertainties in the coolability in terms of the debris bed characteristics even in the case the cavity flooding system is utilized. The coolability of debris particle bed which is important because of the possibility of molten core concrete interaction is related with debris size, distribution and so on. These components depend on the earlier phase such as melt-jet injection, break up, fragmentat…
  • 19
      In-Vessel Retention by External Reactor Vessel Cooling (IVR-ERVC) is one of the severe accident management strategies to terminate or mitigate the severe accident (SA) which is also called ‘core-melt accident’. The reactor vessel which is containing molten core material in the lower head is cooled by flooding coolant. The molten core mixture is expected to be divided into some layers due to the density difference. Fig.2 shows the conventional two layered configuration of IVR. It has light metal layer of Fe-Zr and …
  • 18
    • NUCLEAR SAFETY AND ENERGY CONVERSION Siphon breaking   2017.02.07
      Research reactors are nuclear reactors which were developed for neutron based research industry rather than for power generation. Water in the reactor pool acts as the moderator, reflector, and shielding barrier to radioactivity from the nuclear reactor fuel rods. Moreover, the coolant in the reactor pool provides the ultimate heat sink during accidents in which the pump of primary cooling system stops working. The quantity of coolant is strongly related to the length of time for which safety can be maintained between…
  • 17
    • NUCLEAR SAFETY AND ENERGY CONVERSION Condensation   2017.02.07
      Condensation phenomenon occurs when vapor is subcooled below the saturation temperature at given pressure. And condensation is a phase change phenomenon which is very efficient heat transfer using latent heat. Many industries use condensation heat exchanger, namely condenser. Thus, it is important to study the condensation heat transfer characteristics in various conditions and find the way to enhance the condensation heat transfer performance 
  • 16
    • NUCLEAR SAFETY AND ENERGY CONVERSION Quenching & Film boiling   2017.02.07
      We used the basic two experimental methods to understand the Film Boiling Heat Transfer; quenching and leidenfrost experiment. The major points able to achieve are below, 1) Efficient core-cooling strategy under the severe accident of nuclear power plant 2) Phenomenological investigation during phase-change on the modulated heat transfer surface under high temperature condition 3) Development of technical methodology to identify the phase-change motion at th…
  • 15
    • NUCLEAR SAFETY AND ENERGY CONVERSION Flow boiling   2017.02.07
      The flow boiling, which has heat transfer with flow, is the one of the phase change phenomena but not well understood due to the complexity. In many industries including power plants, flow boiling is the core technology in heat transfer because it is an efficient method in comparison to other techniques. Specially, flow boiling is more complex than pool boiling, so flow regime is one of the means to divide physical phenomena for understanding 
  • 14
    • NUCLEAR SAFETY AND ENERGY CONVERSION Pool boiling   2017.02.07
      As one of a key phenomenon in thermal hydraulics system, nucleate boiling has been widely studied by numerous researchers to improve efficiency and safety of the system (i.e, nuclear power plant, refrigerating system etc.). In general, the evaluation of the boiling performance mainly focus on two physical parameters: boiling heat transfer (BHT) and critical heat flux (CHF). Since both BHT and CHF contribute the thermal system efficiency and safety, respectively many new approaches to enhance the boiling performance co…
  • 13
    • NUCLEAR PHYSICS AND PLASMA 플라즈마 관측용 고압 챔버 / Chamber for h…   2017.02.07
      대부분의 플라즈마 실험이나 응용에서는 진공과 대기압 사이의 압력에서 발생한 플라즈마를 관측하거나 처리한다. 본 연구실은 대기압 보다 높은 압력에서의 플라즈마 특성을 연구할 수 있는 고압 챔버를 구축하였다. 100 기압 이상의 압력에서 단순히 아크방전을 일으키지 않고 지속해서 방전을 일으킬 수 있는 고주파수 플라즈마 장치를 개발 중이다. 플라즈마 장치 개발 후 본 연구실의 전문화된 진단 방법을 통해 고압 플라즈마 특성을 분석할 계획이다.Since most plasma experiments and applications are carried out at the pressure of 1 atm or less, our group found research in the characteristics of plasmas at high pressure indispensable, thus the chamber for high pressure plasma observation has been constructed. Instead of dischargin…
  • 12
  • 11
    • NUCLEAR PHYSICS AND PLASMA 새로운 플라즈마 임피던스 측정법: 이중 주파수 방법 /…   2017.02.07
      기존에 사용됐던 싱글 주파수를 이용한 S11 측정을 본 연구실이 이중 주파수 방법 (Two frequency method)을 사용해 플라즈마의 불확실했던 임피던스 값을 구하는 방법을 고안해냈다.The laboratory has introduced a novel method of measuring S11 called ‘two frequency method’. The conventional method of S11 measurement leaves the impedance value in uncertainty whereas ‘two frequency method’ accurately determines the plasma impedance based on an equivalent circuit model. 
  • 10
    • NUCLEAR PHYSICS AND PLASMA 플라즈마 표면 처리 / Plasma Surface tr…   2017.02.07
      금속산화물 표면처리는 대기압 플라즈마 응용분야 중 하나이다. 본 연구실은 고주파수 플라즈마를 이용해 금속산화물의 산화 환원 반응실험을 한 후 X-ray Diffraction (XRD), Photo-Emission Spectroscopy (PES) 또는 Raman spectroscopy 등의 진단 방법을 통해 처리된 금속산화물을 분석한다.Surface treatment on metal oxide is one of the industrial applications of nonthermal atmospheric pressure plasmas. Our surface treatment group uses high frequency plasmas to generate oxidation and reduction reactions on metal oxides, and then analyze them through X-ray Diffraction (XRD), Photo-Emission Spectroscopy (PES), or Raman spectros…
  • 9
    • NUCLEAR PHYSICS AND PLASMA 플라즈마 소스와 전극 개발 / Development o…   2017.02.07
      본 연구실은 공진의 특성을 이용하는 Coaxial Transmission Line Resonator (CTLR)을 보유하고 있으며 이로부터 생성되는 플라즈마 제트를 사용해 표면처리, 살균, 씨앗 발아 등 다양한 분야에 응용시킨다.동시에 CTLR 외 다른 형태의 플라즈마 전극의 디자인을 구상 및 제작하며, 크고 무거운 벤치탑 플라즈마 전력원을 소형화시키고 전극을 파워모듈과 일체화시켜 휴대성이 있는 플라즈마 시스템을 만드는 연구를 하고 있다.The laboratory applies the plasma jet generated from a resonator type of plasma electrode called Coaxial Transmission Line Resonator (CTLR) for surface treatments, sterilization, seed germination, etc. The laboratory conceptually designs and manufactures many configurations of plasm…
  • 8
    • NUCLEAR PHYSICS AND PLASMA MHD instabilities   2017.02.07
      자기 유체 역학 (Magnetohydrodynamics, MHD)는 플라즈마와 같은 전기 전도성 유체의 자기적 특성에 대해 연구하는 학문이다. 아래는 KSTAR ECEI 장치로 관측한 MHD 불안정성 현상들의 대표적 예다.(1) 플라즈마 내부 불안정성 현상아래의 quasi-3D 이미지는 KSTAR 내에 설치된 ECEI 장비를 이용하여 측정한 영상이다 [2].플라즈마 중심 영역에서 전자 사이클로트론 주파수 가열 혹은 유도 전류로 발생하는 tearing instability를 통해 여러 개의 플럭스 관이 형성된다. 현재의 연구는 multiple tearing mode에 대한 3D 섭동 구조의 영향에 중점을 두고 있으며, 이는 sawtooth와 같은 불안정성을 제어하는데 중요한 역활을 할 것으로 보고있다.(2) 플라즈마 경계면 불안정성 현상 (Edge Localized Mode: ELM)High confinement mode (H-mode)는 플라즈마 가둠 상태를 향상시키는 것으로 알려져 있고, 가장자리 부근에 가파른 압력 경사가 형성되어 …
  • 7
    • NUCLEAR PHYSICS AND PLASMA 플라즈마 파동 진단 시스템 / Plasma wave d…   2017.02.07
      자기 재결합 과정에서 발생하는 플라즈마 파동을 실험적으로 관측하고 연구하기 위해 광대역, 고해상도 RF 측정 시스템을 개발하였다. 이를 통해 whistler 파 등 다양한 plasma wave의 주파수 특성 및 편광을 측정하는 것을 목표로 하고 있다. A broadband rf spectrometer has been developed to study plasma waves generated during the catastrophic collapse or crash of MHD instabilities. In combination with ECEI, the rf diagnostic provides a unique opportunity to study the role of plasma waves in the magnetic reconnection physics and thereby the crash mechanism of MHD instabilities. The rf spectrometer was motivated by the theore…
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