• 비파괴검사학회지
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• 제16권1호
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• pp.29-33
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• 1996

핵연료봉의 결함 탐상을 위하여 차동환상형 와전류시험 탐촉자를 설계 및 제작하여, 핵연료봉 시험을 위한 최적 시험 조건을 구하였다. 관통결함, 내부결함, 외부결함을 낸 표준시편에 대하여 와전류시험을 수행함으로써 시험 주파수와 출력 신호의 위상 및 크기에 대한 상관 관계를 구하였다. 이를 토대로 하여 고리원자력 1호기에서 연소한 핵연료봉 G33-N2에 대하여 와전류시험을 수행하여 관통결함 신호를 얻었다. 와전류시험에서 관통결함으로 예측된 위치에서 금속조직시험을 수행하여 얻은 결과는 와전류시험 결과와 잘 일치하였다. 따라서 와전류시험법은 조사핵연료봉의 피복관에 대한 건전성을 평가하는 도구로써 그 신뢰성이 양호함을 실증하였다.

• 한국자동차공학회논문집
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• 제22권4호
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• pp.65-71
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• 2014

As an important component of a fuel cell, the bipolar plate comprises a large proportion in the fuel cell's volume, weight and price. The bipolar plate is the most widely used; however, graphite bipolar plate is large in volume, brittle and therefore easily broken during assembling. In addition, due to its poor machinability, production costs a lot, unless mass production. Compared with the graphite bipolar plate, the metal bipolar plate has good machinability, high electric conductivity and strong mechanical strength; however, it corrodes easily and has a high contact resistance, so in order to prevent corrosion and reduce the contact resistance, the basic metal needs to be processed by use of electro polishing and coating. The water which is produced by electrochemical reactions in the fuel cell must be discharged smoothly. In this study, in order to prevent corrosion the processes of electro polishing and CrN coating were used. According to the presence or absence of these processes, the contact angles can be measured and different metal bipolar plates can be made, these plates can be used for comparing and analyzing the performance of the fuel cell.

• 한국재료학회지
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• 제20권4호
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• pp.187-193
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• 2010

Chromium nitride (CrN) samples with two different layer structures (multilayer and single layer) were coated on bipolar plates of polymer electrolyte membrane fuel cells (PEMFC) using the reactive sputtering method. The effects with respect to layer structure on corrosion resistance and overall cell performance were investigated. A continuous and thin chromium nitride layer ($Cr_{0.48}\;N_{0.52}$) was formed on the surface of the SUS 316L when the nitrogen flow rate was 10 sccm. The electrochemical stability of the coated layers was examined using the potentiodynamic and potentiostatic methods in the simulated corrosive circumstances of the PEMFC under $80^{\circ}C$. Interfacial contact resistance (ICR) between the CrN coated sample and the gas diffusion layer was measured by using Wang's method. A single cell performance test was also conducted. The test results showed that CrN coated SUS316L with multilayer structure had excellent corrosion resistance compared to single layer structures and single cell performance results with $25\;cm^2$ in effective area also showed the same tendency. The difference of the electrochemical properties between the single and multilayer samples was attributed to the Cr interlayer layer, which improved the corrosion resistance. Because the coating layer was damaged by pinholes, the Cr layer prevented the penetration of corrosive media into the substrate. Therefore, the CrN with a multilayer structure is an effective coating method to increase the corrosion resistance and to decrease the ICR for metallic bipolar plates in PEMFC.

• 동력기계공학회지
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• 제19권3호
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• pp.16-21
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• 2015

Nitrous oxide($N_2O$) concentration in the atmosphere has been constantly increased by the human activities with industrial growth after the industrial revolution. One of factors to increase $N_2O$ concentration in the atmosphere is the $N_2O$ emission caused by the combustion of marine fuel. Especially, a sulfur component included in marine fuel oils is known as increasing the $N_2O$ formation in diesel combustion. Form this point of view, $N_2O$ emission from a ship is not negligible. On the other hand, Exhaust gas recirculation(EGR) that have thermal, chemical and dilution effect is effective method for reducing the NOx emission. In this study, an author investigated $N_2O$ reduction by using EGR on a direct injection diesel engine. The test engine was a 4-stroke diesel engine with maximum output of 12 kW at 2600rpm, and operating condition of the engine was a fixed load of 75%. The experimental oil was a blend-fuel that were adjusted with sulfur ratio of 3.5%, and EGR ratio of 0%, 10%, 20% and 30%. In conclusion, diesel fuel that contained 3.5% sulfur component increased $SO_2$ emission in exhaust gas, and increment of EGR ratio reduced NO emission. Moreover, $N_2O$ emission was decreased as over 50% at EGR ratio of 10% and reduced 100% at EGR ratio of 30% compared with $N_2O$ emission of 0% EGR ratio.

• 공업화학
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• 제22권5호
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• pp.447-452
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• 2011

석유자원의 고갈이 에너지 및 화학원료물질로 재생 가능한 바이오매스의 이용성을 증가시키고 있다. 본 총설에서는 바이오에너지 및 바이오화학원료인 C4-C6 생산에 관해 논하고자 한다. 주요한 C4 물질인 n-butanol과 n-butyric acid를 다량 생산하는 미생물은 Clostridium tyrobutyricum, Clostridium beijerinckii, Clostridium acetobutylicum이다. 대표적인 C6 물질인 n-hexanoic acid는 Clostridium kluyveri와 Megasphaera elsdenii가 다량 생산한다. 미생물 발효에 의해 보고된 n-butanol, n-butyric acid, n-hexanoic acid의 최대 생산량은 각각 21, 55, 19 g/L이었다. 배양과정에서 이들 생산물의 제거는 최종산물억제의 감소로 미생물에 의한 n-butanol, n-butyric acid, n-hexanoic acid의 생산량을 증가시켰다. 특히 C6 물질인 n-hexanoic acid는 n-hexanol로 될 수 있는 고 부가가치 물질로 생물학적 생산 연구가 꾸준히 진행 중인데, 신규한 미생물인 Clostridium sp. BS1은 galactitol을 이용하여 5 g/L의 n-hexanoic acid를 생산하였다.

• Journal of Welding and Joining
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• 제30권1호
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• pp.59-63
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• 2012

The spacer grid is one of the main structural components in a fuel assembly. It supports fuel rods, guides cooling water and maintains geometry from external impact load and cyclic stress by the vibration of nuclear fuel rod, it is necessary to have sufficient strength against dynamic external load and fatigue strength. In this study, the mechanical properties and fatigue characteristics of laser beam welded zircaloy thin sheet are examined. The material used in this study is a zirconium alloy with 0.66 mm of thickness. The fatigue strength under cyclic load was evaluated at stress ratio R=0.1. S-N curves are presented with statistical testing method recommend by JSME- S002 and compared with S-N curves at R.T. and $315^{\circ}C$. As a result of the experimental approach, the design guide of fatigue strength is proposed and the results obtained from this study are expected to be useful data for spacer gird design.

• Nuclear Engineering and Technology
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• 제47권1호
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• pp.85-93
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• 2015

Background: $^{241}Am$, $^{243}Am$, and $^{237}Np$ isotopes are among the most radiotoxic components of spent nuclear fuel. Recently, researchers have planned different incineration scenarios for the highly radiotoxic elements of nuclear waste in critical reactors. Computational methods are widely used to predict burnup rates of such nuclear wastes that are used under fuel matrixes in critical reactors. Methods: In this work, the Monte Carlo N-particle transport code was used to calculate the neutronic behavior of a transuranic (TRU)-bearing CANada Deuterium Uranium 6 reactor. Results: The computational data showed that the 1.0% TRU-containing thorium-based fuel matrix presents higher proliferation resistance and TRU depletion rate than the other investigated fuel Matrixes. The fuel matrix includes higher negative temperature reactivity coefficients as well. Conclusion: The investigated thorium-based fuel matrix can be successfully used to decrease the production of highly radiotoxic isotopes.

• Journal of Mechanical Science and Technology
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• 제19권6호
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• pp.1358-1365
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• 2005

Flue gas recirculation (FGR) is widely adopted to control NO emission in combustion systems. Recirculated flue gas decreases flame temperature and reaction rate, resulting in the decrease in thermal NO production. Recently, it has been demonstrated that the recirculated flue gas in fuel stream, that is, the fuel induced recirculation (FIR), could enhance much improved reduction in NO per unit mass of recirculated gas, as compared to conventional FGR in air. In the present study, the effect of dilution methods in air and fuel sides on NO reduction has been investigated numerically by using $N_2$ and $CO_2$ as diluent gases to simulate flue gases. Counterflow diffusion flames were studied in conjunction with the laminar flamelet model of turbulent flames. Results showed that $CO_2$ dilution was more effective in NO reduction because of large temperature drop due to the larger specific heat of $CO_2$ compared to $N_2$. Fuel dilution was more effective in reducing NO emission than air dilution when the same recirculation ratio of dilution gas was used by the increase in the nozzle exit velocity, thereby the stretch rate, with dilution gas added to fuel side.

• 한국추진공학회지
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• 제23권2호
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• pp.13-20
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• 2019

본 연구에서는 석유계항공유와 혼합하여 사용이 가능한 바이오항공유의 혼합 비율에 따른 점화지연 특성의 변화를 확인하기 위하여, 두 항공유를 일정한 비율로 혼합한 시료의 점화지연시간을 측정하여 분석하였다. 측정한 모든 온도 조건에서 Bio-6308의 점화지연시간이 Jet A-1의 점화지연시간보다 짧게 나타났으며, 두 항공유를 일정한 비율로 혼합한 경우에도 Bio-6308의 함량이 증가할수록 점화지연시간은 짧아지는 경향을 보였는데, 이는 Jet A-1을 구성하는 방향족 화합물의 영향 때문임을 n-heptane/Toluene의 점화지연시간 측정을 통해 확인하였다.

• Journal of Electrochemical Science and Technology
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• 제15권2호
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• pp.207-219
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• 2024

Metal-N-C (MNC) catalysts have been anticipated as promising candidates for oxygen reduction reaction (ORR) to achieve low-cost polymer electrolyte membrane fuel cells. The structure of the M-N_x moiety enabled a high catalytic activity that was not observed in previously reported transition metal nanoparticle-based catalysts. Despite progress in non-precious metal catalysts, the low density of active sites of MNCs, which resulted in lower single-cell performance than Pt/C, needs to be resolved for practical application. This review focused on the recent studies and methodologies aimed to overcome these limitations and develop an inexpensive catalyst with excellent activity and durability in an alkaline environment. It included the possibility of non-precious metals as active materials for ORR catalysts, starting from Co phthalocyanine as ORR catalyst and the development of methodologies (e.g., metal-coordinated N-containing polymers, metal-organic frameworks) to form active sites, M-N_x moieties. Thereafter, the motivation, procedures, and progress of the latest research on the design of catalyst morphology for improved mass transport ability and active site engineering that allowed the promoted ORR kinetics were discussed.