• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2007년 추계학술발표대회 개요집
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• pp.203-205
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• 2007

A spacer grid assembly, which is an interconnected array of slotted grid straps and is welded at the intersections to form an egg crate structure, is one of the main structural components of the nuclear fuel assembly for pressurized water reactors(PWRs). The spacer grid assembly is structurally required to have enough buckling strength under various kinds of lateral loads acting on the nuclear fuel assembly so as to keep the nuclear fuel assembly straight. And also, the spacer grid assembly is hydraulically required to have less hydraulic resistance of coolant. To meet this requirement, it is necessary to weld the welding parts carefully and precisely. In this study, weld qualities such as, weld bead size and spatter manufactured by various welders were compared and analyzed. And performance parameters such as impact strength of spacer grid and hydraulic resistance of coolant were also compared and analyzed. Comparison results show that the weld qualities could be improved by selecting the optimal welding condition and also improving the welding technique.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2012년도 제38회 춘계학술대회논문집
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• pp.424-428
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• 2012

공기흡입형 추진기관은 운용의 단순함, 저비용, 저장의 용이성 등의 장점으로 각광받고 있는 추진 기관이다. 본 논문에서는 Boron을 이용한 공기흡입형 추진기관의 가스발생기에 사용될 추진제 연구를 수행하였다. 이를 위하여, Amorphous Boron Powder를 적용한 추진제에 다양한 첨가제를 사용하여 연소특성을 파악하였고, Boron bead를 제조하여 추진제에 적용하여 Amorphous Boron Power를 적용한 추진제와의 차이점을 비교 분석 하였다.

• 한국안전학회지
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• 제27권1호
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• pp.20-25
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• 2012

The purpose of the study is to assess the extinguishing concentration of inert gases in engine nacelle fire. The experiment was performed with a two dimensional rectangular bluff body stabilized flames, where the fuel was ejected to counter flow and co-flow against an oxidizer stream. Two inert gases, $CO_2$ and $N_2$, were used for extinguishing agent in the oxidizer and methane was used for fuel. The main experimental parameters were the direction of injecting fuel, the kinds of agent and the velocity ratio between air and fuel streams, which controlled the mixing characteristic near bluff body and the strength of recirculation zone in the downstream. The result shows the flame structure and the mode were strongly dependent with fuel/air ratio and the fuel jet direction. For both flow configurations, the extinguishing concentration of $CO_2$ was smaller than the $N_2$ because of the large heat capacity of $CO_2$. However, the concentration of inert gasesat blowout was much smaller than those in the cup burner and coflow jet diffusion flames, which implies that the extinction mechanism of bluff body stabilized flames was mainly due to the aerodynamic aspect. Compared to co-flow fuel injection, the extinguishing concentration of inert gases under counter flow configuration was lower. The effect of direction might result from the mixing characteristic and strength of recirculation zonearound a bluff body. More details should be investigated for the characteristic of recirculation zone in the wake of bluff body using the LES(Large Eddy Simulation).

• 대한기계학회논문집B
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• 제29권2호
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• pp.180-188
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• 2005

It is well known that a lean burn engine caused by stratified mixture formation has many kinds of advantages to combustion characteristics, such as higher thermal efficiency and lower CO, NOx levels than conventional homogeneous mixture combustion. Although this combustion can achieve low fuel consumption technology, it produces much unburned hydrocarbon and soot because of heterogeneous equivalence ratio in the combustion chamber. Therefore, the stratified mixture formation technology is very important to obtain the stable lean combustion. In this paper, fundamental studies for stratified combustion were carried out using a constant volume combustion chamber. The local effect of mixture formation according to control air-fuel distribution in the chamber was examined experimentally. In addition, the effect of turbulence on stratified charge combustion process was observed by schlieren photography. From this study, we found that the flame propagation speed increase with swirl flow and the swirl promotes the formation of fuel and air mixture.

• 한국수소및신에너지학회논문집
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• 제14권1호
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• pp.35-45
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• 2003

Polymer electrolyte fuel cells(PEFC) have been considered to be a suitable candidate for residential, portable and mobile applications, due to their high efficiency and power density, even at low operating temperature. KIER developed a 5kW class PEFC system for residential application and operated the system for over 1,000 hours. To develop a 5kW PEFC system, performance of a cell was improved through successive tests of single cell of small and large area. Fabrication of three 2,5 kW class stacks, design and fabrication of natural gas reformer, design of auxiliary equipments such as DC/DC converter, DC/AC inverter and humidifying units were carried out along with integration of components, operation and evaluation of total system. During the development period from 1999 to 2001, MEA(membrane electrode assembly) fabrication technologies, design and fabrication technologies for separators, stacking technologies and so on were developed, thereby providing basis for developing stacks of higher efficiency and power density in the future. Experience of development of natural gas reformer opened possibilities to use various kinds of fuels. Main results obtained from the development of a 5kW class PEFC system for residential application are summarized.

• Korean Chemical Engineering Research
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• 제53권2호
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• pp.231-235
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• 2015

저등급석탄을 건조하고 무결합제로 성형하는 경우에 대한 조건별 특성 연구를 수행하였다. 인도네시아 산 두 종류의 저등급석탄을 전기오븐에서 건조시킨 후 성형에 사용하였으며, 석탄의 수분별, 입도별, 성형압력별, 보관일수별로 압축강도를 측정하여 성형특성을 비교하였다. 석탄의 수분별로는 10~15 wt%에서 가장 높은 강도를 나타내었으며, 석탄의 종류에 따라 가장 높은 강도를 갖는 수분 함량의 차이가 있었다. 석탄의 입도는 적을수록 높은 강도를 나타내며 입도가 증가할수록 수렴하는 경향을 나타내었다. 성형압력이 높아질수록 성형 강도가 높게 나타났으나, 약 300 kN 이상에서는 크게 차이를 보이지 않았다. 보관일수별로는 약 일주일 동안 강도가 급격히 감소한 후 수렴하는 경향을 보였다. 이상의 결과는 저등급석탄의 산지에서 고품위화시킨 석탄을 국내 반입하는 경우에 대한 성형석탄 제조 및 관리의 지침으로 활용될 수 있다.

• 한국수소및신에너지학회논문집
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• 제30권6호
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• pp.531-539
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• 2019

The development of cost-effective electrocatalysts with high durability is one of the most important challenges for the commercialization of polymer electrolyte fuel cells (PEFCs). The durability of the electrocatalyst has been studied in terms of structural change in the active metal and the support. In particular, in fuel cell vehicles, degradation of the carbon-based support is known to have a significant effect on the electrocatalyst deterioration since the start-up/shut-down cycle is frequently repeated. The requirements for the support of the electrocatalyst include high surface area, electrical conductivity, chemical stability, and so on. In this study, we propose the evaluation methods for choosing better support materials and present the physicochemical properties that promising carbon supports should have. Three kinds of carbon materials with different crystallinity are compared. From in-depth study using X-ray diffraction, Raman spectroscopy, thermogravimetric analysis, and accelerated stress test, it is clearly confirmed that the durability of carbon-supported electrocatalysts is closely related to the physicochemical properties of the carbon supports.

• 한국수소및신에너지학회논문집
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• 제25권6호
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• pp.620-628
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• 2014

Direct Carbon Fuel Cell(DCFC) is one of new power generation that the chemical energy of solid carbon can be converted into electrical energy directly. At the high temperature, the electrochemical reaction of the carbon takes place and the carbon reacts with oxygen to produce carbon dioxide as followed overall reaction ($C+O_2{\rightarrow}CO_2$). However, in case of using the raw coals as a fuel of DCFC, the volatile matter containing carbon, hydrogen, and oxygen produces at operating temperature. In this study, the electrochemical reaction of Adaro coal was compared with Graphite. This work focused on the electrochemical reaction of two kinds of solid carbon by Electrochemical Impedance Spectroscopy(EIS). The EIS results were estimated by equivalent circuit analysis. The constant phase element(CPE) was applied in Randle circuit to explain an electrode and fuel interface. The correlation between the fuel characteristic and electrochemical results was discussed by elements of equivalent circuit of each fuel.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1995년도 추계학술발표회논문집(2)
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• pp.623-629
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• 1995

To investigate the effects of powder shape on U loading density of fuel meat, two kinds of fuel meats were prepared with atomized and comminuted U$_3$Si$_2$ powders by extrusion or rolling process. Extruded fuel meats with atomized spherical U$_3$Si$_2$ powder appeared to have much less porosity than those with comminuted irregular U$_3$Si$_2$ powder at higher U$_3$Si$_2$ fraction- The U$_3$Si$_2$ particles with spherical shape are less fractured in extrusion than in rolling. Most of atomized particles on the whole maintained to have spherical shapes in the extrusion. It has been shown that atomized spherical particles are expected to approach similar upper loading limits comparing with comminuted particles in rolled plates, but exceed comminuted powder loading limits in extruded rods.

• Nuclear Engineering and Technology
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• 제40권4호
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• pp.319-326
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• 2008

To transport process wastes efficiently from the Advanced Spent Fuel Conditioning Pyro-process Facility (ACPF) at the Korea Atomic Energy Research Institute (KAERI), a new hot cell cask has been designed based on an existing hot cell padirac transport cask, with not only a neutron absorber for improved shielding capability, but also a docking facility for an easy docking system. In the new hot cell cask, two kinds of materials have been considered as shielding materials, polyethylene and resin. To verify the transport compatibility of the waste and spent fuel for the ACPF, neutron and photon shielding calculations were performed using the MCNPX code. The source term was evaluated by the ORIGEN-ARP code system based on spent PWR fuel. From the calculation, it was found that the maximum surface dose rates of the hot cell cask with the two candidates were estimated within the limit (2 mSv/hr).