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월성1호기 계속운전 관련 결함연료위치탐지계통 배관의 열화관리평가
송명호,김홍기,이영호,Song, Myung Ho,Kim, Hong Key,Lee, Young Ho 한국압력기기공학회 2011 한국압력기기공학회 논문집 Vol.7 No.2
The end of design lifetime for Wolsong unit 1 will be reached on 20th November in 2012. So the license renewal documents for the continuous operation of Wolsong unit 1 is under reviewing now. Major components of primary system such as pressure tubes, feeder pipes including delayed neutron monitoring system tubing are being replaced and many components of secondary system are also being repaired. In this paper, the assessment on the wear degradation of delayed neutron monitoring system tubing(on the other hand, DN tube was called) was performed for the ageing management of the same component. The wear defects of this component was one of causes that resulted in heavy water leakage accidents. Therefore design specifications of Wolsong uint 1 and heavy water leakage accidents of pressurized heavy water reactors were reviewed and causes of wear defect for DN tubes were analyzed. Wear propagation equations based on the heavy water leakage history were made and the proper repairing time was possible to be expected if the continued operation was considered. Finally design change items of DN tubes that were conducted for the long term operation of Wolsong unit 1 are introduced.
송명호,김홍기,이정민,Song, Myung Ho,Kim, Hong Key,Lee, Jung Min 한국압력기기공학회 2010 한국압력기기공학회 논문집 Vol.6 No.2
As a part of license renewal for the continued operation of Wolsong unit 1, the periodic safety review report was submitted near the end of design lifetime, 2012, and now is under reviewing. Major components of primary system such as pressure tubes, feeder pipes and so on are being replaced and many components of secondary system are also being repaired. So the license renewal of Wolsong unit 1 is expected to be acquired without significant issues. But on the other hand, steam generators of Wolsong unit 1 had the good performance and therefore the replacement and repair for the steam generator are not needed. Recently it is reported that some cracks were detected in a few of european steam generator with Alloy 800 tubes and the cause of cracks was the outer diameter stress corrosion cracking(ODSCC) due to the concentration of chemical impurities on the outer surface of tube. Accordingly the overall review on this issue was performed. The long-term operation is likely to results to form the concentration mechanism for the tube corrosion as the sludge build-up in the secondary side of steam generator and the crack in the crevice between tube and tube-sheet and expansion transitions is apt to be occurred. In this paper, the history of steam generator inspection and operation of Wolsong unit 1 are reviewed and the reliability of steam generator tube is evaluated and the steam generator aging management program for Wolsong unit 1 is introduced.
Nb이 첨가된 주조 2상 스테인리스강의 열취성에 관한 연구
송명호,김용규,Song, Myeong-Ho,Kim, Yong-Gyu 한국재료학회 1997 한국재료학회지 Vol.7 No.7
본 연구에서는 주조 2상 스테인리스강의열시효에 대한 시효온도, 시효시간 및 Nb함유량의 영향을 관찰하기 위해 기계적 성질 및 조직을 조사하였으며 Nb을 함유한 주조 2상 스테인리스강의 파괴기구를 규명하기 위해 SEM에 의한 파단면 관찰과 WDS성분분석을 통해 파괴기구의 특성을 고찰하였다. 시효온도와 시효시간이 증가함에 따라 페라니트으 미소경도가 증가하였으며 항복강도의 경우 시효온도와 시효시간에는 영향을 받지 않았으나 Nb을 함유한 재료들이 Nb을 함유치 않은 재료들에 비해 다소 낮은 항복강도 값을 보였다. 충격흡수에너지 값은 시효시간 및 시효온도의 증가에 따라 시험된 모든 재료에서 저하되었는데 0.4% Nb을 함유하는 경우 Nb을 약간 함유하거나 함유치 않은 재료들에 비해 시효시간에 따라 급격한 감소 경향을 보였다. 파단면 관찰결과 페라이트 기지 또는 페라이트/오스테나이트 상경계에서 석출된 VbC를 비롯한 탄화물들이 취성저항성을 낮추는데 크게 기여했음을 알 수 있었다.
A Study on the Pitting Corrosion Resistance of Laser Surface Treated Nickel-Base Alloy
송명호,김용규,Song, Myeong-Ho,Kim, Yong-Gyu Materials Research Society of Korea 1999 한국재료학회지 Vol.9 No.2
The effect on the pitting corrosion resistance of laser welding and surface treatment developed as a repair method of stream generator tubing material that was a major component of primary system at nuclear power plant was observed. Some heat-treated Alloy 600 tubing materials used at domestic nuclear power plants were laser-surface observed. Some heat-treated Alloy 600 tubing materials used at domestic nuclear power plants were laser-surface melted and the microstructural characteristics were examined. The pitting corrosion resistance was examined through Ep(pitting potential) and degree of pit generation by means of the electrochemical tests and the immersion tests respectively. The pit formation characteristics were investigated through microstructural changes and the pit initiation site and pit morphology. The test results showed that the pitting corrosion resistances was increased in the order of the followings; sensitized Alloy 600, solution annealed alloy600, and laser surface melted Alloy 600. Pits were initiated preferably at Ti-containing inclusions and their surroundings in all tested specimens and it is believed that higher pitting resistance of laser-surface treated Alloy 600 was caused by fine, homogeneous distribution of non-soluble inclusions, the disappearance of grain boundary, and the formation of dense, stable oxide film. The major element of corrosion products filled in the pit was Cr. On the other hand, Fe was enriched in the deposit formed on the pit.
송명호(Myeongho Song),김경연(Kyoungyoun Kim),손영준(Young-Jun Sohn),양태현(Tae-Hyun Yang) 한국추진공학회 2014 한국추진공학회 학술대회논문집 Vol.2014 No.12
연료전지 시스템 내의 스택의 냉각은 연료전지 성능에 많은 영향을 미친다. 스택 냉각이 원활히 이루어 지지 않으면, 스택내부의 온도분포의 불균형이 생기거나 과열로 인한 부품 손상 및 성능저하 문제가 발생한다. 본 연구에서는 고고도 무인기 연료전지 시스템 내의 스택 적정 온도를 얻기 위한 송풍기의 조건을 알아보기 위해 전산해석을 수행하였다. 속도의 크기, 냉각채널 단면 종횡비와 분리판의 종횡비에 따른 냉각 효과를 조사하였다. 냉각 채널의 유동 진행 방향을 줄이는 분리판 형상을 채택하고 냉각 채널의 단면 형상비를 증가시키면 냉각효과가 증가함을 확인하였다. Proper cooling of PEM fuel cell stack is essential for high performance operation of fuel cell system. Insufficient cooling of the stack can cause significant damage of components due to overheating and also can decrease cell performance by dehydration of the polymer electrolyte. In the present study, we performed a computational analysis to assess the condition of the cooling system to secure the proper temperature in fuel cell stack system for high altitude long endurance (HALE) unmanned aerial vehicle (UAV). Effects of flow velocity from the cooling fan and the cooling channel cross-sectional aspect ratio on the stack temperature and required power input were examined. The present numerical results showed that the cooling efficiency significantly increase with cooling channel cross-sectional aspect ratio. Futhermore, it was shown that replacement of the square bipolar plates to rectangular ones can also reduce the required input power by the cooling system.