• Journal of Welding and Joining
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• 제32권4호
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• pp.1-9
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• 2014

A quantitative understanding on the effect of the welding conditions on weld joint dimensions and weld thermal cycle is difficult through experimental studies alone. The experimental realization of temperature distribution in the weld pool is proved to be extremely difficult due to the small size of welds, high peak temperature and steep temperature gradients in weld pool. This review deals with the heat transfer and fluid flow analysis to understand the parametric influence of a single wire submerged arc welding (SAW) and multi-wire SAW processes on the weld bead dimensions, temperature and fluid flow distribution in the weldment.

• Nuclear Engineering and Technology
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• 제32권5호
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• pp.425-432
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• 2000

It has been an essential part for the safety assessment of nuclear power plants to understand various phenomena associated with the molten core-concrete interaction(MCCI) under severe accidents. In this study, the severe accident analysis code MELCOR was used to simulate the MCCI experiments such as SWISS and SURC test series which had been performed in Sandia National Laboratories(SNL). The calculation results were compared with corresponding experimental data such as melt temperature, concrete ablation distance, gas generation rate, and aerosol release rate. Good agreements were observed between MELCOR calculation and experimental data. The melt pool was sustained within the range of high temperature and the concrete ablation occurred continuously. The gas generation and aerosol release were under the influence of melt temperature and overlying water pool, respectively.

• 방사선산업학회지
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• 제17권3호
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• pp.283-292
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• 2023

Spent nuclear fuel corresponds to high-level radioactive waste that has high decay heat and radioactivity. Accordingly, Spent nuclear fuel withdrawn from the reactor core is primarily stored and managed in a spent nuclear fuel pool in the nuclear power plant to reduce decay heat and radioactivity. In Korea, most nuclear power plant store all spent nuclear fuel in a spent nuclear fuel pool. For wet storage, there are no defense in depth different with reactor core. The study related to spent nuclear fuel pool accident should be carried out to ensure safety. Therefore, it is necessary to analyze previous study cases related to safety of spent nuclear fuel pool and accident cases to build foundational knowledge. The Objective of this study is to analyze study cases of safety assessment and cases for spent nuclear fuel pool accident. For analyzing study cases of safety assessment, possible phenomena when spent nuclear fuel pool accident occurring identified, Subsequently, study cases for safety assessment about each phenomena were investigated, and materials & methods and results for each study are analyzed. For analyzing cases for spent nuclear fuel pool accident, we analyzed accident cases caused by loss of cooling and loss of coolant in spent nuclear fuel pool. Subsequently, causes and change of water level and temperature by each accident case are analyzed. As a result of the analysis on study cases of spent nuclear fuel pool accident, the results of the study conducted by each research institute were vary depending on the computer code, materials & methods of experiment and major assumptions used in the study. As a result of analyzing cases for spent nuclear fuel pool accident, it was found that accident cases for loss of cooling is more than cases for loss of coolant accident. Even though the types of accident in spent nuclear fuel pool were similar, the specific causes were different by each accident case. All the accident cases analyzed did not lead to severe accidents, such as nuclear fuel being exposed to the air. The result of this study will be used as fundamental data for study on spent nuclear fuel pool accident that will be conducted in the future.

• 한국화재소방학회논문지
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• 제21권3호
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• pp.78-83
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• 2007

석유류 중에서도 차량, 선박, 보일러 등에 많이 사용되고 있는 디젤유는 휘발유나 등유보다도 연소시에 발열량이 높기 때문에, 화재 발생시에 큰 피해를 초래한다. 따라서 본 연구는 시중에 판매중인 디젤유을 이용하여 액면화재 실험을 하였으며, 연소시에 화염의 내부온도와 화염으로부터 발생되는 복사열에 대해서 측정하였다. 디젤유의 순간 최대화염온도는 $900^{\circ}C$ 이상되는 것으로 나타났으며, 평균 최대화염온도는 $800^{\circ}C$ 이상으로 나타났다. 또한 최대화염온도는 가연성 액체의 표면으로부터 5 H/D에서 나타났으며, 이 거리 보다 멀어질 수로 화염의 온도는 낮아졌다. 복사열의 경우 저장용기의 크기와 시료의 량에 따라서 크게 달라지는 것을 알 수 있었으며, 실험 용기의 크기가 0.5 m이고, 시료량이 13 mm와 20 mm에서는 각각 92.29 kW와 117.43 kW로 나타났으며, 크기가 1.0 m의 용기에서는 각각 364.35 kW와 405.88 kW로 나타났다.

• 한국화재소방학회논문지
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• 제19권3호
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• pp.13-19
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• 2005

본 논문에서는 금속염 첨가제를 함유한 미분무수의 소화성능을 연구하고자 아세트산 나트륨을 함유한 단일 액적의 증발속도를 측정하였으며, small-scale 챔버내에서의 헵탄 pool fire에 대한 소화실험을 실시하여, 화염의 온도를 분석함으로써 첨가제에 의한 미분무수 소화특성을 분석하였다. 순수물과 수용액의 증발특성을 비교한 결과 핵비등 영역에서 온도가 높을수록 용해된 첨가제의 석출 및 표면장력의 변화 등 물리적 영향으로 순수물에 비해 수용액의 증발속도가 현저히 느리게 나타났다. 소화실험 결과, 저압에서는 물 액적이 화염의 플림을 뚫지 못하기 때문에 소화는 이루어지지 않았고 단순히 화염의 크기를 작아지게 하였다. 중압에서는 첨가제를 넣었을 경우 액적의 운동량 증가에 따른 물리적 소화효과와 첨가제의 화학적 소화효과가 상승작용을 하여 화염을 억제하였고, 고압에서는 미분무수 시스템의 주요 소화 메커니즘 이외에도 blowing효과에 의해서 화염이 소화되는 것을 관찰할 수 있었다.

• 한국지리정보학회지
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• 제15권3호
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• pp.91-102
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• 2012

본 연구는 환경생태학적 하천관리의 기초가 되는 것으로서, 어류분포 특성을 파악할 수 있는 하천서식처 분류에 영상정보를 활용하기 위한 기법을 개발하고 이에 대한 적용 가능성을 평가하였다. 먼저 서식처별 특성자료를 파악하기 위해 지형측량, 유량 및 수온관측 등을 실시하였으며 현지관측 시점에 해당하는 하천의 영상을 얻기 위해 무인항공촬영을 실시하였다. 어류 분포특성을 파악하기 위한 서식처로는 크게 riffle, pool, glide를 선정하였으며, riffle 영역은 빠른 물의흐름으로 인해 RGB의 표준편차가 pool과 glide에 비해 크게 나타났다. 이러한 RGB의 표준편차 특성을 이용하여 riffle 영역의 해상도와 kernel 크기별 분류 정확도를 평가한 결과, 해상도가 30cm이고 kernel 크기가 11일때의 분류 정확도가 77.17%로 가장 높게 나타났다. 또한 적외선 카메라를 이용하여 pool과 glide 영역에 대한 수온을 관측한 결과 각각 $19.6{\sim}21.3^{\circ}C$와 $15.5{\sim}16.5^{\circ}C$로서 약 $4{\sim}5^{\circ}C$의 차이를 보였으며, 이러한 적외선 사진정보를 통해 pool과 glide 영역에 대한 분류가 가능하게 되었다. 향후 RGB와 적외선 밴드를 탑재한 무인항공촬영시스템이 활용될 경우 어류 분포 파악을 위한 서식처 분류가 보다 효과적으로 수행될 것으로 판단된다.

• Journal of Mechanical Science and Technology
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• 제18권6호
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• pp.990-1001
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• 2004

The retention of a molten pool vessel cooled by internal vessel reflooding and/or external vessel reactor cavity flooding has been considered as one of severe accident management strategies. The present numerical study investigates the effect of both internal and external vessel mixed cooling on an internally heated molten pool. The molten pool is confined in a hemispherical vessel with reference to the thermal behavior of the vessel wall. In this study, our numerical model used a scaled-down reactor vessel of a KSNP (Korea Standard Nuclear Power) reactor design of 1000 MWe (a Pressurized Water Reactor with a large and dry containment). Well-known temperature-dependent boiling heat transfer curves are applied to the internal and external vessel cooling boundaries. Radiative heat transfer has been considered in the case of dry internal vessel boundary condition. Computational results show that the external cooling vessel boundary conditions have better effectiveness than internal vessel cooling in the retention of the melt pool vessel failure.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.76-81
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• 2002

The dramatic increase in the depth of a weld bead penetration has been demonstrated by welding a stainless steel in GTA (Gas-Tungsten-Arc) process with activating flux which consists of oxides and halides. However, there is no commonly agreed mechanism fer the effect of flux on the process. In order to make clear the mechanism, each behavior of the arc md the weld pool in GTA process with activating flux is observed in comparison with a conventional GTA process. A constricted anode root is shown in GTA process with the activating flux, whereas a diffuse anode root is shown in the conventional process. These anode roots are related strongly to metal vapor from the weld pool and the metal vapor is also related to temperature distributions on the weld pool surface. Furthermore, it is suggested that a balance between the Marangoni force and the drag force of the cathode jet should dominate the direction of re-circulatory flow in the weld pool. The electromagnetic force encourages the inward re-circulatory flow due to the constricted anode root in the case with flux. The difference in flow direction in the weld pool changes the geometry or depth/width ratio of weld bead penetration.

• 설비공학논문집
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• 제25권3호
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• pp.143-149
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• 2013

In this work, nucleate pool boiling heat transfer coefficients (HTCs) of R134a and R1234yf are measured, on flat plain, 26 fpi low fin, Turbo-B, Turbo-C and Thermoexcel-E surfaces. All data are taken at the liquid pool temperature of $7^{\circ}C$, on a small square copper plate ($9.53mm{\times}9.53mm$), at heat fluxes from $10kW/m^2$ to $200kW/m^2$, with an interval of $10kW/m^2$. Test results show that nucleate boiling HTCs of all enhanced surfaces are greatly improved, as compared to that of a plain surface. Nucleate pool boiling HTCs of R1234yf are very similar to those of R134a, for the five surfaces tested.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 하계학술발표대회 논문집
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• pp.1332-1337
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• 2008

Fire model shall be verified and validated to reliably predict the consequences of fires within its limitations. This study aims to predict pool fire with two rooms using FDS and to coompare FDS simulation results with PRISME experimental data which can be applicable to the fire of nuclear power plant facility. Four different sizes of grid (0.08m, 0.1m, 0.125m, 0.2m) are used in the simulation and the simulated results of specific quantities such as temperature, chemical composition, heat flux and heat release rate are compared to the experimental data. From this study, the FDS simulation results with the finer grid resolution show better similarity and trend with pool fire experimental data. The sensitivity analysis and the selection of the proper size grid are essential to predict the consequences of pool fire with two rooms reliably.