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GNP법을 이용한 고체산화물 연료전지의 공기극용 La<sub>0.75</sub>Sr<sub>0.25</sub>FeO<sub>3</sub>의 제조 및 특성
박주현,손희정,임탁형,이승복,윤기석,윤순길,신동열,송락현,Park, Ju-Hyun,Son, Hui-Jeong,Lim, Tak-Hyoung,Lee, Seung-Bok,Yun, Ki-Seok,Yoon, Soon-Gil,Shin, Dong-Ryul,Song, Rak-Hyun 한국전기화학회 2007 한국전기화학회지 Vol.10 No.1
Glycine Nitrate Process(GNP)를 이용하여 $La_{0.75}Sr_{0.25}FeO_3$를 합성하였다. 이때, GNP의 글리신의 함량은 화학양론식으로 계산하여 3.17mol을 첨가하였다. ICP-AES분석으로 각각의 조성 함량을 조사하고, XRD, SEM분석으로 합성된 분말의 결정성과 입자크기를 분석하였다. 이렇게 분석한 분말은 일축가압 성형으로 펠렛을 제조하였으며, 이 시편은 $1200^{\circ}C$에서 소결하였다. 소결된 시편은 아르키메데스 법을 이용하여 소결밀도를 측정히였다. 전기화학적 성능을 평가하기 위해 AC impedance spectroscopy로 측정하였으며, GNP 법으로 합성된 LSF가 기존의 LSM 보다 낮은 Ohmic resistance및 Polarization resistance를 보임을 확인하였다. 또한 합성된 LSF를 양극으로 사용하여 연료극 지지체식 고체산화물 연료전지의 단위전지를 제작하였으며, 그 성능은 $750^{\circ}C$에서 $342mW/cm^2(0.7V,\;488mA/cm^2)$을 나타내었다. 마지막으로 임피던스 분석에 의하여 단위전지의 전기화학적 분극저항을 평가하였다. We synthesized and investigated $La_{0.75}Sr_{0.25}FeO_3$ by Glycine Nitrate Process(GNP) method used as cathode materials for SOFC(solid oxide fuel cell). Optimized amount of glycine is 3.17 mol. ICP elemental composition analysis indicated that the stoichiometry of the synthesized powders have nearly nominal values. SEM images and XRD patterns reveal that the synthesized powder has uniform size distribution and high degree of crystallinity. The sample powders were isostatically pressed to form a pellet. The green body was sintered at $1200^{\circ}C$ and the relative density of the sintered specimens were measured by Archimedes mettled. We measured electrochemical performance of LSF by AC impedance spectroscopy. Resistance of LSF shows lower value than that of LSM throughout all temperature region. The anode-supported solid oxide fuel cell showed a performance of $342mW/cm^2(0.7V,\;488mA/cm^2)$ at $750^{\circ}C$. The electrochemical characteristics of the single cell were examined by at impedance method.
김종민(Jong-min Kim),배재현(Jae-hyun Bae),손갑헌(Gap-heon Sohn),윤기석(Ki-seok Yoon),최택상(Taek-sang Choi) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.11
The probabilistic fracture analysis is used to determine the effects of uncertainties involved in material properties, location and size of flaws, etc, which can not be addressed using a deterministic approach. In this paper the probabilistic fracture analysis is applied for evaluating the RV(Reactor Vessel) under PTS(Pressurised Thermal Shock). A semi-elliptical axial crack is assumed in the inside surface of RV. The selected random parameters are initial crack depth, neutron fluence, chemical composition of material (copper, nickel and phosphorous) and RTNDT. The deterministically calculated KI and crack tip temperature are used for the probabilistic calculation. Using Monte Carlo simulation, the crack initiation probability for fixed flaw and PNNL(Pacific Northwest National Laboratory) flaw distribution is calculated. As the results show initiation probability of fixed flaw is much higher than that of PNNL distribution, the postulated crack sizes of 1/10t in this paper and 1/4t of ASME are evaluated to be very conservative.
용접부 잔류응력에 기인한 경로의존성 J-적분의 측정에 대한 연구
강선예(Seon-Ye Kang),유완(One Yoo),박성호(Sung-Ho Park),윤기석(Ki-Seok Yoon),최택상(Taek-Sang Choi),이봉상(Bong-Sang Lee) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5
The J-integral is an important fracture mechanics parameter applicable for many areas which provide the integrity evaluation methods. Fracture of welding structure usually starts at weld region due to high weld residual stress and defects easily found in it. However, it is difficult to calculate the correct J-integral of the structure containing weld because J-integral is path dependent due to the residual stress. It is also true that there are no evidence that the J-integral measuring methods suggested by the ASTM or others are appropriate for J-integral specimens with the residual stress. Therefore, in this paper, the J-integral measuring methods suggested by the ASTM or others were evaluated and the CMOD based J-integral measuring method is suggested as an appropriate method for measuring J-integral of specimens containing weld residual stress.
국제공동연구 PARTRIDGE를 통한 확률론적 건전성 평가 기술 개발 현황
김선혜,박정순,김진수,이진호,윤은섭,양준석,이재곤,박홍선,오영진,강선예,윤기석,박재학,Kim, Sun Hye,Park, Jung Soon,Kim, Jin Su,Lee, Jin Ho,Yun, Eun Sub,Yang, Jun Seog,Lee, Jae Gon,Park, Hong Sun,Oh, Young Jin,Kang, Sun Yeh,Yoon, Ki Seok,P 한국압력기기공학회 2013 한국압력기기공학회 논문집 Vol.9 No.1
A probabilistic assessment code, PRO-LOCA ver. 3.7 which was developed in an international co-operative research program, PARTRIDGE was evaluated by conducting sensitivity analysis. The effect of some variables such as simulation methods (adaptive sampling, iteration numbers, weld residual stress model), crack features(Poisson's arrival rate, maximum numbers of cracks, initial flaw size, fabrication flaws), operating and loading conditions(temperature, primary bending stress, earthquake strength and frequency), and inspection model(inspection intervals, detectable leak rate) on the failure probabilities of a surge line nozzle was investigated. The results of sensitivity analysis shows the remaining problems of the PRO-LOCA code such as the instability of adaptive sampling and unexpected trend of failure probabilities at an early stage.
〈응용논문〉 : 가압기 밀림배관에 대한 환경피로계수 감소 방안 고찰
강선예(Sun-Yeh Kang),김규완(Kyu-Wan Kim),송민섭(Min-Sup Song),양준석(Jun-Seog Yang),윤기석(Ki-Seok Yoon),최택상(Taek-Sang Choi) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
가동원전을 계속운전하기 위한 심사시 규제기관에서는 NUREG/CR-6260에 기술된 위치를 포함한 피로취약 부위에 대해 원자로냉각재 환경을 고려한 피로평가를 수행할 것을 요구하고 있다. 가압기 밀림관은 환경피로평가결과 ASME 허용값을 만족시키기 어려운 부위중 하나이다. 밀림관에서 환경보정계수값은 최대 15.35까지 계산되므로 환경피로계수는 ASME Code 허용값(1.0)을 초과할 수 있다. 본 논문에서는 NUREG/CR-5704에 기술된 방법을 적용한 환경보정계수 계산 방법론, 가동원전 WEC형 가압기 밀림관 용접부에 대해 보수적인 피로해석 방법론을 적용한 환경피로계수 계산, ASME Code 요건을 만족시키기 위한 환경피로계수 감소 방안에 대해 논의하였다. 결론적으로, 본 논문에서 제안한 환경피로 계수 감소방안을 적용할 경우 가동원전 WEC형 가압기 밀림관 용접부의 환경피로계수는 크게 감소하는 것으로 평가되었다. For the plant life extension, the regulatory body requires the assessing of reactor coolant environmental impact on a critical components that includes, as a minimum, those selected in NUREG/CR-6260. The pressurizer surge line is the most difficult to meet the ASME code limit for fatigue evaluations considering the effects of LWR environments. The environmental usage factor values can exceed allowable limit(1.0) of the ASME Code because the cumulative usage factor increase by a factor of maximum 15.35. This paper describes Methodology of the environmental correction factor calculation using the method described in NUREG/CR-5704, the calculation of environmental fatigue usage factor based on a conservative approach for ASME fatigue evaluation, and five(5) proposed schemes to reduce the environmental CUF to below the ASME Code limit. Finally, the environmental CUF at WEC Type surge line welding locations could be reduced considerably by using the proposed schemes.