• 터널과지하공간
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• 제23권2호
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• pp.141-149
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• 2013

경수로 사용 후 핵연료의 파이로 공정 처리를 통해 예상되는 고준위폐기물 처분시스템을 대상으로 열적 성능평가를 수행하였다. 처분방식으로 수평 처분터널 처분시스템을 고려하였다. 수평 처분터널 간격 25 미터와 처분공 간격 2미터를 대상으로 평가하였다. 세라믹폐기물 수평 처분터널 주변의 다양한 위치에 대해 장기간 동안 열 해석을 통하여 온도 변화를 해석하였다. 열 해석은 ABAQUS 프로그램을 이용하였다. 열 해석 결과에 의하면 처분시스템 중 어느 부분에서도 최고 온도가 $100^{\circ}$를 넘지 않아, 열적 성능 기준을 만족하였다. 열 해석 결과에 따르면, 처분시스템 중앙에 위치한 처분용기 주변이 외곽에 위치한 것의 주변보다 최고 온도 기준으로 약 $3^{\circ}$정도 높았다. 이것은 처분시스템 설계시 가능한 외곽에 위치한 처분용기가 많도록 설계하는 것이 처분밀도를 향상시킬 수 있음을 시사하였다.

• 한국해양공학회지
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• 제29권6호
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• pp.418-426
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• 2015

Recently, shipping operators have been making efforts to reduce the fuel cost in various ways, such as trim optimization and bulb re-design. Furthermore, IMO restricts the hydro-dioxide emissions to the environment based on the EEDI (Energy Efficiency Design Index), EEOI (Energy Efficiency Operational Indicator), and SEEMP (Ship Energy Efficiency Management Plan). In particular, ship speed is one of the most important factors for calculating the EEDI, which is based on methods suggested by ITTC (International Towing Tank Conference) or ISO (International Standardization Organization). Many shipbuilding companies in Korea have carried out speed trials around the Korea Straits. However, the conditions for these speed trials have not been exactly the same as those for model tests. Therefore, a ship’s speed is corrected by measured environmental data such as the seawater temperature, density, wind, waves, swell, drift, and rudder angle to match the conditions of the model tests. In this study, fundamental research was performed to evaluate the ship resistance performance due to changes in the water temperature and salinity, comparing the ISO method and numerical simulation. A numerical simulation of a KCS (KRISO Container ship) with a free-surface was performed using the commercial software Star-CCM+ under three conditions that were assumed based on the water temperature and salinity data in the Korea Straits. In the simulation results, the resistance increased under low water temperature & high salinity conditions, and it decreased under high water temperature & low salinity conditions. In addition, the ISO method showed the same result as the simulation.

• 청정기술
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• 제14권1호
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• pp.61-68
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• 2008

연료전지기술은 환경적으로 유해한 오염물질을 발생시키지 않으려, 높은 에너지 밀도를 가지는 청정에너지기술이다. 특히 고분자전해질 연료전지(Polymer electrolyte membrane fuel cell, PEMFC)는 넓은 응용분야로 인해 최근 큰 관심을 받고 있으며, 폭넓은 연구가 진행되고 있다. 본 연구에서는 단위전지 내 연료극(anode) 및 공기극(cathode) 촉매 층을 대상으로 고분자전해질연료전지의 운전시간 경과에 대한 성능변화 및 안정성을 예측하는 모델링을 수행하였다 촉매층에서 발생하는 단위전지의 주요한 성능감소 원인으로 연료극에서의 일산화탄소 피독 현상을 고려하였다. 전지의 장기간 운전모델링 결과 연료극에 공급되는 기체 내의 일산화탄소 비율이 클수록 단위전지성능의 안정성이 크게 감소되는 것으로 나타났다. 또한 장기 운전시 공기극의 느린 산소환원반응과 백금의 용해와 소결에 의해 전지의 성능이 감소되는 것으로 나타났다. 이들을 극복하는 방안으로 연료극에 공급되는 수소의 비율을 높이고 공기극의 촉매층 내에 있는 백금양을 높이는 것을 제안하고자 한다.

• 한국세라믹학회지
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• 제29권11호
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• pp.900-904
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• 1992

High temperature electrical conductivity was measured for perovskite La0.98Sr0.02MnO3 at 200~130$0^{\circ}C$ as a function of Po2 and 1/T. Perovskite La1-xSrxMnO3 system is the typical oxygen electrode in solid oxide fuel cell (SOFC). Acetate precursors were used for the preparation of mixed water solution and the calcined powders were reacted with Na2CO3 flux in order to obtain highly reactive powders of perovskite La0.98Sr0.02MnO3. The relative density was greatly increased above 90% because of the homogeneous sintering. From the conductivity ($\sigma$)-temperature and conductivity-Po2 at constant temperature, the defect structure of La0.98Sr0.02MnO3 was discussed. From the slope of 1n($\sigma$) vs 1/T, the activation energy of 0.069 and 0.108eV were evaluated for above 40$0^{\circ}C$, respectively. From the relationship between $\sigma$ and Po2, it was found that the decomposition of La0.98Sr0.02MnO3 was occurred at 10-15.5 atm(97$0^{\circ}C$) and 10-11 atm(125$0^{\circ}C$). It is supposed that the improvement of p-type conductivity may be leaded by the increase of Mn4+ concentration through the substitution of divalent/monovalent cations for La site in LaMnO3.

• 한국분무공학회지
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• 제16권3호
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• pp.152-158
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• 2011

Fast pyrolysis of biomass is one of the most promising technologies for converting biomass to liquid fuels. The pyrolysis oil, also known as the bio crude oil (BCO), have been regarded as an alternative fuel for petroleum fuels to be used in diesel engine. However, the use of BCO in diesel engine requires modifications due to low energy density, high water contents, low acidity, and high viscosity of the BCO. One of the easiest way to adopt BCO to diesel engine without modifications is the use of BCO/diesel emulsions. In this study, a diesel engine operated with diesel, bio diesel (BD), and BCO/diesel emulsion was experimentally investigated. Performance and emission characteristics of a diesel engine fuelled by BCO/diesel emulsion were examined. Results showed that stable engine operation was possible with emulsion and engine output power was comparable to diesel and bio diesel operation. Long term validation of adopting BCO in diesel engine is still needed because the oil is acid, with consequent problems of corrosion especially in the injection system.

• 방사성폐기물학회지
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• 제15권3호
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• pp.199-206
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• 2017

고준위폐기물을 처분하기 위한 심층 처분시설은 지하 500~1,000 m 깊이의 암반층에 설치된다. 심층 처분시스템의 구성 요소로는 처분용기, 완충재, 뒷채움 및 근계 암반이 있다. 이 중 완충재는 심층 처분시스템에 있어 필수적인 요소인데, 완충재는 지하수 유입으로부터 처분용기를 보호하고, 방사성 핵종 유출을 저지한다. 처분용기에서 발생하는 고온의 열량은 완충재로 전파되기에 완충재의 열물성은 처분시스템의 안정성 평가에 상당히 중요하다고 할 수 있다. 완충재의 열전도도 규명에 대한 연구는 많이 진행되고 있는 반면, 비열에 대한 연구는 미진한 상태이다. 따라서 본 연구에서는 국내 경주산 압축 벤토나이트 완충재(KJ-II)에 대한 비열 추정 모델을 개발하고자 하였다. 압축 벤토나이트 완충재의 비열은 이중 탐침법을 이용하여 다양한 포화도와 건조밀도에 따라 측정하였으며, 총 33개의 실험 데이터를 토대로 회귀분석을 이용하여 경주 압축 벤토나이트의 비열을 추정할 수 있는 모델을 제시하였다.

• 대한방사선기술학회지:방사선기술과학
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• 제43권6호
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• pp.481-487
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• 2020

Radiation measurement technology has steadily improved and its usage is expanding in various industries such as nuclear medicine, security search, satellite, nondestructive testing, environmental industries and the domain of nuclear power plants (NPPs). Especially, the simultaneous measurements of gamma rays and neutrons can be even more critical for nuclear safety management of spent nuclear fuel and monitoring of the nuclear material. A semiconductor detector comprising cadmium, zinc, and tellurium (CZT) enables to detect gamma-rays due to the significant atomic weight of the elements via immediate neutron and gamma-ray detection. Semiconductor sensors might be used for nuclear safety management by monitoring nuclear materials and spent nuclear fuel with high spatial resolution as well as providing real-time measurements. We aim to introduce a portable nuclide-analysis device that enables the simultaneous measurements of neutrons and gamma rays using a CZT sensor. The detector has a high density and wide energy band gap, and thus exhibits highly sensitive physical characteristics and characteristics are required for performing neutron and gamma-ray detection. Portable nuclide-analysis device is used on NPP-decommissioning sites or the purpose of nuclear nonproliferation, it will rapidly detect the nuclear material and provide radioactive-material information. Eventually, portable nuclide-analysis device can reduce measurement time and economic costs by providing a basis for rational decision making.

• 한국수소및신에너지학회논문집
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• 제26권6호
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• pp.541-546
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• 2015

Global energy shortage problem is expected to increase driven by strong energy demand growth from developing countries. Nuclear fusion power offers the prospect of an almost infinite source of energy for future generations. Hydrogen isotope storage and delivery system is a important subsystem of a nuclear fusion fuel cycle. Metal hydride is a method of the high-density storage of hydrogen isotope. For the safety storage of hydrogen isotope, depleted uranium (DU) has been widely proposed. But DU needs a safe test because It is a radioactive substance. The authors studied a small-scale DU bed and a medium-scale DU bed for the safety test. And then we made a large-scale DU bed and stored hydrogen isotopes in the bed. Before the hydriding/dehydriding, we tested it's heating and cooling properties and carried out an activation procedure. As a result, Reaction rate of DU-$H_2$ is more rapid than the other metal hydride ZrCo. Through the successful storage result of our large bed, the development possibility of the hydrogen isotope storage technology seems promising.

• 방사성폐기물학회지
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• 제8권1호
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• pp.49-56
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• 2010

Pyroprocessing에 의한 사용후핵연료 처리 과정에서 방사성 희토류 염화물이 포함된 폐용융염이 발생된다. 이러한 폐 용융염 내에 존재하는 방사성 희토류 염화물을 산화물로 침전시켜 회수함으로서 용융염을 재생할 수 있다. 최종적으로 발생되는 방사성 희토류 산화물의 저장과 처분에 적합한 monolithic 고화체를 제조하기 위한 연구를 수행하였다. 본 연구에서는 고상 소결에 의해 붕규산 유리에 의한 고화체 제조, 희토류 산화물을 모나자이트로 합성한 후 붕규산 유리에 의한 고화체 제조를 수행하였다. 또한 zinc titanate 세라믹이 주요성분인 고화 매질(ZIT)을 개발하여 고화체를 제조하였으며 각각의 고화체에 대한 침출 및 물리화학적 특성을 비교 평가하였다. 고상 소결에 의해 제조된 ZIT 매질 고화체는 내 침출성이 크며 밀도가 크고 열전도도가 우수한 특성을 나타내었다.

• 세라미스트
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• 제21권4호
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• pp.378-387
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• 2018

The optimal fabrication conditions for $Gd_{0.1}Ce_{0.9}O_{2-{\delta}}$(GDC) buffer layer and $La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_{3-{\delta}}$ (LSCF) cathode on 1mol% $CeO_2-10mol%\;Sc_2O_3$ stabilized $ZrO_2$ (CeScSZ) electrolyte were investigated for application of IT-SOFCs. GDC buffer layer was used in order to prevent undesired chemical reactions between LSCF and CeScSZ. These experiments were carried out with $5{\times}5cm^2$ anode supported unit cells to investigate the tendencies of electrochemical performance, Microstructure development and interface reaction between LSCF/GDC/CeScSZ along with the variations of GDC buffer layer thickness, sintering temperatures of GDC and LSCF were checked, respectively. Electrochemical performance was analyzed by DC current-voltage measurement and AC impedance spectroscopy. Microstructure and interface reaction were investigated by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Although the interfacial reaction between these materials could not be perfectly inhibited, We found that the cell, in which $6{\mu}m$ GDC interlayer sintered at $1200^{\circ}C$ and LSCF sintered at $1000^{\circ}C$ were applied, showed good interfacial adhesions and effective suppression of Sr, thereby resulting in fairly good performance with power density of $0.71W/cm^2$ at $800^{\circ}C$ and 0.7V.