• Nuclear Engineering and Technology
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• v.20 no.1
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• pp.19-26
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• 1988

The low leakage leading pattern has features as the placement of some fresh fuel assemblies in the core interior to reduce the neutron fluence on the pressure vessel and to enhance the neutron economics. But as fresh fuel assemblies are loaded in the core interior, the local power tends to exceed safety limit due to the high reactivity of the fresh assemblies. Therefore, a large number of burnable poisons must be utilized in a low leakage scheme to suppress the high assembly power as well as the excess reactivity. In this study the effects of burnable poisons are treated as a perturbation on the power distribution, and the 'Power Sensitivity Coefficient' concept is adopted. An application study is performed for cycle 1 of the Korea Nuclear Unit-7 (KNU-7) to justify the usefulness of the reverse depletion method coupled with the above concept. To obtain the optimal burnable poision distribution at the given burnup step, the linear programming technique is adopted. The result shows maximum 4.5% error in the amount of burnable poisons between the calculated and the reference values. It is concluded that the design methodology which consists of the reverse depletion, the power sensitivity coefficient concept, and the linear programming technique can be used to find the optimal turnable poison distribution.

• Korean Journal of Materials Research
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• v.9 no.7
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• pp.680-687
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• 1999

Fe-Al intermetallic compounds were manufactured by using the field-activated combustion synthesis process. Effects of chemical composition(Fe:Al= 3: 1,2:1, 1:1, 1:2, 1:3), Compaction pressure(150, 250, 350MPa) and electrical resistance on the reaction were investigated in this system. As the molar ratio of Al, compaction pressure and electric field increased, the combustion temperature and velocity were increased. The influences for reaction with current adjust way were investigated in this system. But in the absence of a electric field, the reaction could sustain a nonsteady combustion wave and was not completed. The reaction products were characterized with X-ray, SEM and EDXS to determine the structure and composition.

• The Journal of Engineering Research
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• v.2 no.1
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• pp.133-138
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• 1997

The conventional process in synthesizing mullite powder required high temperature ($1300^{\circ}C$) and long chemical reaction time. Thus the combustion process was used to synthesize the mullite powder in order to reduce the reaction time and temperature. The mixture of metal nitrate, fine silica, and fuel was used as the redox compounds under various experimental conditions. The combustion fire in hot plate experiment in rich, lean and stoichiometry fuel does not produce mullite. However, the obvious mullite, small amount of alumina and cristobalite was observed in the $500^{\circ}C$ pre-heat treatment furnace experiment. The components such as silica, urea, aluminm nitrate should be stoichiometry in order to make a perfect mullite crystal.

• Fire Science and Engineering
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• v.30 no.5
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• pp.124-129
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• 2016

According to the current law, on-site flame resistant-treated interior decorations should pass the flame resistant performance test through a 45 degree combustion test from the district fire department. Although a 45 degree combustion test is the most accurate method for determining the flame resistant performance, it can be unreliable when tested on unauthorized samples. To avoid unauthorized sampling, this study suggests on-site flame resistant inspection by X-ray fluorescence spectrometer. Ten types of flame resistant paint were spread on plywoods and MDFs and the components were analyzed by X-ray fluorescence spectrometer. As a result, due to a difference amounts of substances in each paint, each flame resistant paints showed its own characteristic spectrum and the contents of each substance could be determined. On-site flame resistant inspections can be used efficiently when institutional procedures are created.

• Fire Science and Engineering
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• v.33 no.5
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• pp.1-6
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• 2019

The recent development of biofuel production technology facilitates the widespread use of bioethanol and biodiesel by mixing them with fossil fuels. However, the use of these new blended fuels in combustion could result in severe safety problems, such as fire and explosion. In this study, numerical simulation was performed on the well-stirred reactor (WSR) to simulate the autoignition temperature (AIT) in homogeneous combustion and clarify the effect of ethanol addition on the AIT, the most important property for assessing the potential for fire and explosion. Response surface methodology (RSM) was introduced as a design of experiment (DOE), enabling the AIT to be predicted and optimized systematically with respect to three independent variables: ethanol mole fraction, equivalence ratio, and pressure. The results show that the autoignition temperature primarily depends on the ethanol mole fraction and pressure, while the effects of the equivalence ratio are independent of the AIT. RSM accurately predicted the experimental AIT, indicating that this method can be used to effectively predict the key properties involved in fires and explosions.

• Journal of Korean Society of Forest Science
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• v.78 no.4
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• pp.419-424
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• 1989

To obtain relative effectiveness in fire resistance among fire retardant chemicals, oxygen indices were determined for 3.5 mm thick, three-ply, meranti plywoods, treated with 5 commercial chemicals and water and then press-dried, through Up and Down method following oxygen index test of ASTM D 2863-77. The oxygen indices obtained were 28.4 for ammonium sulfate, 26.9 for monoammonium phosphate, 43.4 for diammonium phosphate, 30.1 for borax-boric acid, 32.4 for minalith, and 25.5 for water. Therefore, diammonium phosphate was found to rank first in fire-retardant effectiveness, followed by minalith, borax-boric acid, ammonium sulfate, and monoammonium phosphate in turn, judging from the fact that highly flammable materials are likely to have a low oxygen index.

• Korean Journal of Materials Research
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• v.4 no.5
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• pp.566-573
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• 1994

The diamond synthesis by combustion flame method is considerably affected by the substrate surface temperature and its distribution which are mainly controlled by the ratio of mixed gas, $O_2/C_2H_2$. In order to elucidate the role of gas ratio in the diamond synthetic process by combustion flame, under various gas ratios (R=0.87~0.98; R=ratio of flow-rate of $O_2/C_2H_2$ gas) the substrate temperature was measured by using thermal video system and the morphological change of diamond crystals was analysed by using SEM, Raman spectroscope, and X-ray diffraction method. With increasing the gas ratio, i.e., decreasing the hydrocarbon content, the nucleation rate of diamond crystal was lowerd. It was also found that the morphology of diamond crystals changed from the cubo-octahedron type consisting of (100), (111) plane to the octahedron type of (111) plane. The increase of the substrate temperature consistently resulted in the increase of the nucleation rate as well as the growth rate of diamond crystals in which the surface of diamond crystal dominantly consisting of (100) plane.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.481-481
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• 2016

하천퇴적물은 물의 순환과정에서 유역으로부터 유입되는 물질에 따라 조성이 변하게 된다. 특히 입자가 작은 토양과 유기성 물질들은 물순환과정에 이동성이 크게 나타나며, 인간에 의해 개발된 지역은 자연상태에 비해 이동하는 물질이 많이 나타나곤 한다. 본 연구에서는 하천에 건설된 보에 대한 퇴적물 조사를 실시함으로서 향후 수질관리에 필요한 기초 자료를 수집하고자 하였다. 본고에서는 금강과 낙동강에 건설된 보의 주요지점에 대한 퇴적물 조사를 실시하고 수질영향을 평가하였다. 조사는 홍수기전과 홍수기후로 구분하여 2회에 걸쳐 실시하였으며 물리적 성상과 화학적 항목에 대한 분석을 실시하였다. 입도분석 결과 금강 주요 10개 지점의 퇴적물 조성은 Sand, Silt와 Clay 성분이 혼합되어 있는 것으로 분석되었으며, 삼각좌표 분류법에 의한 토성은 대부분의 지점이 실트질양토(SiL)로 평가되었다. 완전연소가능량은 0.35~1.37로 전 지점에서 하천 호소 퇴적물 오염평가 기준의 유기물 함량기준 13%보다 높지 않은 것으로 나타났으며 홍수기 전 후에도 거의 유사하였다. 금강에서는 중금속뿐만 아니라 유기물 및 영양염류도 기준보다 낮게 나타났으며, 모든 항목에서 환경부예규인 하천 호소퇴적물 오염평가 기준보다 낮게 평가되었다. 하상 퇴적물이 수질에 미치는 영향을 평가하는 용출실험에서도 유기물 및 중금속 모두 수질에 미치는 영향은 거의 없는 것으로 평가되었다. 낙동강 주요 26지점의 입도분석 결과 퇴적물 조성은 대부분 Sand로 구성되어 삼각좌표 분류법에 의한 토성은 사토(S)로 평가되었다. 홍수기 전 후에 조사한 결과 완전연소가능량은 0.27~2.85으로 전 지점에서 하천 호소 퇴적물 오염평가 기준의 유기물 함량 기준보다 낮았으며 홍수기 전 후에도 거의 유사하였다. 화학적 성상 분석 결과 모든 항목에서 환경부예규인 하천 호소퇴적물 오염평가 기준보다 낮게 평가되었으며, 용출실험에서도 유기물 및 중금속 모두 수질에 영향을 거의 미치지 않는 것으로 평가되었다. 이번 조사는 4대강 건설 후 하상이 안정화 되지 않은 상태로 인해 지점간 특별한 경향성은 확인할 수 없었으며 보다 정확한 결과 도출을 위해서는 장기적인 조사를 통해 평가해야 할 것으로 판단되었다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.545-550
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• 2012

High Energy density metal powder has high melting point of oxide film. By this, the ignition source that can make a thermal effect of high-temperature during short time is needed to overcome ignition disturbance mechanism by oxide film. So effective ignition does not occurred with hydrocarbon ignitor, $H_2-O_2$ ignitor, high power laser. But steam plasma can be generate about 5000 K temperature field in short order. Because a steam plasma uses steam as the working gas, it is environmental-friendly and economical. Therefore in this study, we analyze steam plasma temperature field and radical species with optical emission spectroscopy method in order to apply steam plasma ignitor to metal combustion system and cloud particle ignition was identified in visual.

• Prospectives of Industrial Chemistry
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• v.22 no.5
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• pp.25-40
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• 2019

전 세계적으로 환경문제를 해결하기 위한 방안으로 환경규제를 강화시키며 특히 다양한 대기오염 물질 중 최근 큰 이슈인 초미세먼지 저감을 위해 전구물질로 알려진 질소산화물을 제어하기 위한 다양한 기술개발이 가속화되고 있다. 특히, 다양한 처리기술 중에 기술적·경제적인 이점을 갖춘 선택적 촉매환원법(selective catalytic reduction, SCR) 기술을 통하여 질소산화물 제거를 위해 암모니아를 환원제로 반응에 참여시켜 인체에 무해한 H₂O, N₂로 전환하는 기술이 대표적이다. 최근 전 세계적으로 다양한 산업군에서 질소산화물이 배출되고 있으며, 점오염원뿐만이 아니라 비점오염원(mobile sources)에 대한 규제가 강화되고 있다. 디젤엔진이 장착된 선박 배가스 처리장치 내 SCR 기술이 주목을 받고 있으며, NH₃-SCR에 사용되는 촉매는 주로 VO_x/TiO₂, VO_x/W/TiO₂ 촉매가 대표적이다. 한편 선박 디젤엔진에 사용되는 연료에 따라 연소배가스 특성이 다르다. 이러한 연료가 연소됨에 따라 SO₂, SO₃가 발생되고 환원제인 NH₃와 결합하여 황산암모늄염((NH₄)₂SO₄), ABS (ammonium bisulfate, NH₄HSO₄)과 같은 염을 형성시켜 탈질촉매의 비활성화 문제가 발생된다. 이러한 비활성화 물질이 침적된 탈질촉매를 재활성화 시키기 위하여 열 산화를 통해 재생시키고 있다. 이처럼 선박용 SCR 촉매는 강화되는 배출규제 및 엔진기술의 발달로 저감되는 운전 온도에 대비하여 저온 활성 재생이 가능한 고활성, 고내구성 촉매기술 개발이 필요하다.