• Nuclear Engineering and Technology
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• 제45권5호
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• pp.625-636
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• 2013

Pressing demands of economic competitiveness, the need for large-scale deployment, minimizing the need of human intervention, and experience from the past events and incidents at operating reactors have guided the evolution and innovations in reactor technologies. Indian innovative reactor 'AHWR' is a pressure-tube type natural circulation based boiling water reactor that is designed to meet such requirements, which essentially reflect the needs of next generation reactors. The reactor employs various passive features to prevent and mitigate accidental conditions, like a slightly negative void reactivity coefficient, passive poison injection to scram the reactor in event of failure of the wired shutdown systems, a large elevated pool of water as a heat sink inside the containment, passive decay heat removal based on natural circulation and passive valves, passive ECC injection, etc. It is designed to meet the fundamental safety requirements of safe shutdown, safe decay heat removal and confinement of activity with no impact in public domain, and hence, no need for emergency planning under all conceivable scenarios. This paper examines the role of the various passive safety systems in prevention and mitigation of severe plant conditions that may arise in event of multiple failures. For the purpose of demonstration of the effectiveness of its passive features, postulated scenarios on the lines of three major severe accidents in the history of nuclear power reactors are considered, namely; the Three Mile Island (TMI), Chernobyl and Fukushima accidents. Severe plant conditions along the lines of these scenarios are postulated to the extent conceivable in the reactor under consideration and analyzed using best estimate system thermal-hydraulics code RELAP5/Mod3.2. It is found that the various passive systems incorporated enable the reactor to tolerate the postulated accident conditions without causing severe plant conditions and core degradation.

• Nuclear Engineering and Technology
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• 제47권1호
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• pp.26-32
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• 2015

During the course of a severe accident in a light water nuclear reactor, large amounts of hydrogen can be generated and released into the containment during reactor core degradation. Additional burnable gases [hydrogen ($H_2$) and carbon monoxide (CO)] may be released into the containment in the corium/concrete interaction. This could subsequently raise a combustion hazard. As the Fukushima accidents revealed, hydrogen combustion can cause high pressure spikes that could challenge the reactor buildings and lead to failure of the surrounding buildings. To prevent the gas explosion hazard, most mitigation strategies adopted by European countries are based on the implementation of passive autocatalytic recombiners (PARs). Studies of representative accident sequences indicate that, despite the installation of PARs, it is difficult to prevent at all times and locations, the formation of a combustible mixture that potentially leads to local flame acceleration. Complementary research and development (R&D) projects were recently launched to understand better the phenomena associated with the combustion hazard and to address the issues highlighted after the Fukushima Daiichi events such as explosion hazard in the venting system and the potential flammable mixture migration into spaces beyond the primary containment. The expected results will be used to improve the modeling tools and methodology for hydrogen risk assessment and severe accident management guidelines. The present paper aims to present the methodology adopted by Institut de Radioprotection et de $S{\hat{u}}ret{\acute{e}}$ $Nucl{\acute{e}}aire$ to assess hydrogen risk in nuclear power plants, in particular French nuclear power plants, the open issues, and the ongoing R&D programs related to hydrogen distribution, mitigation, and combustion.

• 대한임상독성학회지
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• 제7권2호
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• pp.77-82
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• 2009

Purpose: In highly doses, endosulfan lowers the seizure threshold and elicits central nervous system stimulation, which can result in seizures, respiratory failure, and death. Management of seizure control is essential for survival and prognosis of intoxicated patients. This study assessed whether seizure time was an independent predictor mortality in patients with endosulfan poisoning. Methods: This retrospective study enrolled patients with endosulfan poisoning presenting to Masan Samsung Hospital and Gyeongsang National University Hospital from January 2003 to December 2008. The data were collected from clinical records and laboratory files. Using a multivariate logistic analysis, data on the total population was retrospectively analyzed for association with mortality. Results: Of the 24 patients with endosulfan poisoning, nineteen (79.1%) experienced seizure. The patients in the seizure group showed significantly lower Glasgow coma scale score, base excess, bicarbonate, and significant existence of mechanical ventilation, as compared to the non seizure group (n=5). Seizure, Glasgow coma scale score, systolic blood pressure, bicarbonate level, need for respiratory support, pulse rate, respiratory rate, pH, base excess, and seizure time were associated with mortality. The fatality rate of endosulfan poisoning was 54.1% with higher mortality among patients experiencing. Longer seizure time was associated with higher mortality. Conclusion: Seizure time can be a significant independent predictor of mortality in patients with acute endosulfan poisoning. Physicians should aggressively treat for seizure control in patients with acute endosulfan poisoning.

• Journal of Welding and Joining
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• 제26권4호
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• pp.85-91
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• 2008

The grooving corrosion is caused mainly by the different microstructures between the matrix and weld which is formed during the rapid heating and cooling cycle in welding. By this localized corrosion reaction of pipes, it evolves economic problems such as the early damage of industrial facilities and pipe lines of apartment, and water pollution. So lots of researches were carried out already about grooving corrosion mechanism of ERW carbon steel pipe but there is seldom study for water hammer happened by fluid phenomenon and corrosion rate by flow velocity. In this study, the analysis based on hydrodynamic and fracture mechanics was carried out. ANSYS, FLUENT and STAR-CD were used for confirmation of flow phenomenon and stress on the pipe. As the results, fatigue failure is able to be happened by water hammer and grooving corrosion rate is increased cause by turbulent. Grooving corrosion is happened on the pipe, then friction loss of fluid is occurred from corroded part. Erosion can be happened enough in corroded region of microscopic size that wear "V" form. Also pipe is able to be damaged by water hammer effects because of corroded region is general acting as a notch effects. Corrosion depth was more than half of total thickness, it can be damaged from water hammer pressure.

• 한국지반공학회지:지반
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• 제4권1호
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• pp.17-28
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• 1988

흙의 역학적거동을 파악하기 위한 요소시험중 공시체의 주응력방향을 회전시킬 수 있는 비틀림 전단시험기의 기능에 대하여 검토하였다. 본 연구에서는 이 비틀림전단시험기가 점토시료에 사용 될 수 있게 개량제작되었다. 이 시험기를 사용하여 반죽성형된 Ko-견밀점토시료에 대한 약간의 비배수 비틀림전단시험을 실시하여 혼의 거동에 미치는 주수력축의 회전영향이 조사되었다. 우선, torque없이 비틀림전단시험기를 사용하여 얻은 흙의 역학적 거동이 통상의 축대칭삼축압 축시험에 의한 결과와 비교검토됐다. 흙의 응력일변형거동, 문극수압및 주응력비는연직하중과 torque에 의한 응력경로에 크게 영향을 받았으며 전단변형률의 증가에 따라 주응력회전각과 주응력의 상대적 크기, b(=o2-o3)/(o1-o3)) 값토 점진적으로 커져 파괴시의 값에 수렴하였다.

• 대한토목학회논문집
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• 제7권4호
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• pp.91-102
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• 1987

Boussinesq 지반형(地盤型)의 탄소성체지반(彈塑性體地盤)위에 놓인 원형평판(圓形平板)이 축대칭하중(軸對稱荷重)을 받았을 경우의 거동을 파악하기 위하여 8절점(節點) 등매개변수요소(媒介變數要素)를 사용한 유한요소해석(有限要素解析) 방법(方法)을 이론적(理論的)으로 발전시키고 이를 수행하기 위한 컴퓨터 프로그램을 개발하였다. 이론(理論)의 정당성을 입증하기 위해 모형실험을 수행한 결과 지반(地盤)의 항복조건으로 Mohr-Coulomb 강복이론(降伏理論)을 적용한 수치해(數値解)의 결과(結果)와 실험결과(實驗結果)가 근사함을 확인하였다. Mohr-Coulomb의 파괴이론(破壞理論)을 적용한 비선형해석(非線型解析)을 수행한 예제(例題)의 결과로 부터, 지반의 소성영역(塑性領域)이 원판(圓板)의 녹단부근(綠端附近)에서 발생하기 시작하여 중심축둘레로 연결되었을 때 접지압(接地壓)이 급격히 변하여 전단파괴(剪斷破壞)의 위험성(危險性)이 있다고 판단되고 이 때의 외부작용하중(外部作用荷重)을 임계하중(臨界荷重)으로 정의하였다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제35회 추계학술대회논문집
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• pp.713-716
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• 2010

헬기의 급격한 기동은 연료탱크 내부연료의 출렁임 현상을 발생시키며 연료가 한쪽으로 쏠리는 경우에는 연료탱크 내부 구성품 및 장착부에 큰 하중을 가하게 된다. 이는 연료탱크의 손상(소재의 찢어짐 등) 및 내부 구성품 파손을 유발한다. 이는 항공기 조종사 및 승무원의 생존성 문제와 직결되는 사안으로써, 미 군사규격(MIL-DTL-27422D)에서는 Slosh & Vibration 인증시험을 통하여 연료탱크 및 내부 구성품 장착의 건전성을 검증하도록 규정하고 있다. 본 논문은 미 군사규격의 요구조건을 만족시키는 한국형 기동헬기 용으로 개발된 연료탱크의 Slosh & Vibration 시험설비 구축결과 및 연료탱크 Slosh & vibration 인증시험 결과를 제시한다.

• Smart Structures and Systems
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• 제26권3호
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• pp.319-329
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• 2020

Structural damage to an arch dam is often of major concern and must be evaluated for probable rehabilitation to ensure safe, regular, normal operation. This evaluation is crucial to prevent any catastrophic or failure consequences for the life time of the dam. If specific major damage such as a large crack occurs to the dam body, the assessments will be necessary to determine the current level of safety and predict the resistance of the structure to various future loading such as earthquakes, etc. This study investigates the behavior of an arch dam cracked due to water pressure. Safety factors (SFs), of shear and compressive tractions were calculated at the surfaces of the contraction joints and the cracks. The results indicated that for cracking with an extension depth of half the thickness of the dam body, for both cases of penetration and non-penetration of water load into the cracks, SFs only slightly reduces. However, in case of increasing the depth of crack extension into the entire thickness of the dam body, the friction angle of the cracked surface is crucial; however, if it reduces, the normal loading SFs of stresses and joints tractions reduce significantly.

• Elastomers and Composites
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• 제34권2호
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• pp.128-134
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• 1999

타이어 코드용 강철선을 RF 플라즈마를 이용한 acetylene 및 butadiene 가스의 플라즈마 중합으로 코팅하였으며, 타이어용 고무와의 접착력을 TCAT 또는 T-test로 측정하였다. 강철선의 접착력은 사용된 gas, plasma power, 코팅시간 및 가스 압력에 따라 측정하였으며, 플라즈마 중합에 앞서 Ar 플라즈마 에칭으로 타이어 코드를 세척하였다. 또한 $80^{\circ}C$의 증류수에서 7일간 노화시켜 접착력 저하를 고찰하였으며, 접착력 시험 후 타이어 코드 표면을 SEM으로 분석하여 파괴거동을 규명하고자 하였다. 가장 우수한 접착력은 acetylene의 경우 20W, 2분, 25mtorr에서, 그리고 butadiene의 경우는 l0W, 4분, 25mtorr에서 얻을 수 있었으며, Ar 에칭에 의한 접착력 변화는 없었다. 노화에 의한 접착력 저하는 없었으며, 도리어 증가하는 현상을 보였다. SEM 분석에서 강철선의 높은 거칠기와 플라즈마 코팅의 얇은 두께로 인하여 파괴거동 규명에는 한계가 있었다.

• 한국전산구조공학회논문집
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• 제22권6호
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• pp.541-548
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• 2009

본 논문은 샤르피 충격실험과 유한요소법를 이용하여 노치위치에 따른 파괴거동과 흡수에너지의 영향을 평가하였다. 본 연구자는 쉴드메탈아크 용접방법으로 두께가 25mm인 압력용기용강(SA-516 Gr. 70)을 용접하였고, 이 용접된 평판으로 샤르피 시편을 제작하였다. 샤르피 충격실험에서는 용접열영향부(HAZ)에서 노치위치가 다른 시편이 사용되었다. 그리고 본 연구자는 유한요소법을 이용하여 샤르피 충격실험에서의 균열진전을 모사하였다. 용접열영향부(HAZ)의 기계적 물성을 유한요소해석에 적용하기 위해 HAZ를 2개 영역, 3개 영역 그리고 4개 영역으로 나누었다. 본 연구결과에서는 샤르피 충격실험의 흡수에너지가 노치위치에 의존적이라는 것을 보여주었다. 또한 샤르피 용접시편에서 신뢰성 있는 유한요소해석 결과를 얻기 위해서는 용접열영향부를 적어도 3개 이상의 영역으로 나누어야 한다는 결과를 얻었다.