• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1998.05a
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• pp.159-165
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• 1998

The RCM strategies are considered as an effective maintenance tool in nuclear power plants to allocate limited resource efficiently. In this paper, the importances of HPSI system on the CDF were analyzed with PSA model of Yonggwang units 1,2. The HPSI system was chosen because it is of one of the pilot system for the study of Yonggwang units 1,2 RCM. With the remodeling of the HPSI system, the total CDF of 16 initiating events was quantified and the importance of 74 basic events of HPSI was analyzed.

• Journal of the Korean Society of Safety
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• v.30 no.3
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• pp.100-106
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• 2015

A module or independent subtree is a part of a fault tree whose child gates or basic events are not repeated in the remaining part of the fault tree. Modules are necessarily employed in order to reduce the computational costs of fault tree quantification. This quantification generates fault tree solutions such as minimal cut sets, minimal path sets, or binary decision diagrams (BDDs), and then, calculates top event probability and importance measures. This paper presents a new linear time algorithm to detect modules of large fault trees. It is shown through benchmark tests that the new method proposed in this study can very quickly detect the modules of a huge fault tree. It is recommended that this method be implemented into fault tree solvers for efficient probabilistic safety assessment (PSA) of nuclear power plants.

• Proceedings of the Korean Reliability Society Conference
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• 2000.04a
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• pp.161-168
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• 2000

고리 3,4호기 및 영광 1,2호기의 원자로보호계통 및 공학적안전설비작동계통의 정기점검주기와 허용정지시간에 대하여 계통의 신뢰도와 노신손상빈도를 평가하여 안전성이 저해되지 않는 범위에서 합리적인 정기점검주기와 허용정지시간을 도출하였다. 이를 위하여 원자로보호계통의 17개 원자로정지신호와, ESFAS계통의 11개의 안전설비작동신호에 대해서 고장수목을 작성하였고, 정기점검주기 변화에 따른 신뢰도를 평가하였다. 또한 계통의 신뢰도가 발전소의 안전성에 어떤 영향을 미치는가를 파악하기 위하여 노심손상빈도를 분석하였다. 분석 결과 현행 1개월의 점검주기를 3개월로 연장한다 하더라도 신뢰도는 20%미만 노심손상빈도는 2%정도 저하되는 것으로 나타났다. 이런 정도의 신뢰도와 위험도가 변화는 원자력발전소의 안전성에 거의 영향을 주지 못하기 때문에 점검주기를 연장하는 안이 타당한 것으로 나타났다.

• Transactions of the Korean hydrogen and new energy society
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• v.25 no.6
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• pp.609-619
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• 2014

In the present study, the frequency of the undesired accident was estimated for a quantitative risk assessment of a large-scale hydrogen liquefaction plant. As a representative example, the hydrogen liquefaction plant located in Ingolstadt, Germany was chosen. From the analysis of the liquefaction process and operating conditions, it was found that a $LH_2$ storage tank was one of the most dangerous facilities. Based on the accident scenarios, frequencies of possible accidents were quantitatively evaluated by using both fault tree analysis and event tree analysis. The overall expected frequency of the loss containment of hydrogen from the $LH_2$ storage tank was $6.83{\times}10^{-1}$times/yr (once per 1.5 years). It showed that only 0.1% of the hydrogen release from the $LH_2$ storage tank occurred instantaneously. Also, the incident outcome frequencies were calculated by multiplying the expected frequencies with the conditional probabilities resulting from the event tree diagram for hydrogen release. The results showed that most of the incident outcomes were dominated by fire, which was 71.8% of the entire accident outcome. The rest of the accident (about 27.7%) might have no effect to the population.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2019.05a
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• pp.230-231
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• 2019

This study is a development on condition based maintenance(CBM) technology which is a core item of future autonomous ships. It is developing to design & installation of condition monitoring system and acquisition & processing of data from ongoing ships for fault prediction & prognosis of engine in operation. The ultimate goal of this study is to develop a predicts and decision support software for marine engine faults. To do this, the FMEA and fault tree analysis of the main engine should be accompanied by the analysis of classification of system, identification of the components, the type of faults, and the cause and phenomenon of the failure. Finally, the CBM system solution software could predict and diagnose the failure of main engine through integrated analysis for bid-data of ongoing ships and engineering knowledge. Through this study, it is possible to pro-actively cope with abnormal signals of engine and to manage efficiently, and as a result, expected that marine accident and ship operation loss during navigation will be prevented in advance.

• Nuclear Engineering and Technology
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• v.25 no.4
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• pp.515-528
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• 1993

In a Passive PWR, the successful actuation of Automatic Depressurization System (ADS) is essentially required so that no core damage is occurred following small LOCA. But it has been shown in the previous studies that Core Damage Frequency (CDF) from small LOCA is significantly caused by unavailability of ADS. In this study, the design vulnerabilities impacting the ADS unavailability have been identified and the design improvement items have been proposed through the system reliability assessment using the fault tree methodology The impacts on CDF according to the change of system unavailability have also been analyzed. In addition, small LOCA simulation using RELAP5/MOD3 code has been performed to show the thermal-hydraulic feasibility of the suggested design enhancements.

• Nuclear Engineering and Technology
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• v.19 no.3
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• pp.186-191
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• 1987

In this paper, we suggest the simple and practical direct simulation method for the system reliability calculation In the aspect of system unavailability calculation, this method can simplify the calculation process by applying the hard-wired system fault tree. For the calculation purpose, we use the ESCAF which is developed by Mr. Laviron in France. As a consequence, we estimate the unavailability of OP$\Delta$T & OT$\Delta$T channel in W PWR plants as a value of 8.17576$\times$10$^{-9}$ from IEEE std. 500-1977's reference data. In our calculation, the processing time is no more than 25 sec.

• Journal of Advanced Navigation Technology
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• v.13 no.1
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• pp.19-26
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• 2009

Air Traffic Management (ATM) system requires extremely high reliability for the safe and dependable operations in the airport. This paper reports a study on the reliability of the prototype ATM hardware system including the servers and local area networks. Reliability Block Diagram and Fault Tree Analysis on the prototype ATM hardware were performed.

• Transactions of the Korean hydrogen and new energy society
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• v.17 no.3
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• pp.272-278
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• 2006

This study is quantitatively assessing of safety about dispenser of hydrogen station because it is hydrogen energy to efficient safety use. The large leakage of hydrogen gas is the most important accident among others occurrence possibility in hydrogen station. It had written FT by top event and calculated unavailability, m-cutsets, leakage frequency, etc with FTA after each base event collect reliability data by reliability data handbook, THERP-HRA and estimation of the engineering.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.227-228
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• 2005

사용중인 OC의 사고가 외물접촉, 자연현상, 일반인 과실 등으로 인하여 전체 배전선로 일시고장의 대부분을 차지하고 있음으로, 피복의 트래킹 성능을 개선하여 수목 및 조류와의 접촉으로 인한 접촉부 전개 집중 시 또는 지지금구의 바인더부에 고전계 인가 시 트래킹에 의한 절연물의 탄화, 침식 등에 의하여 발생할 수 있는 절연파괴 등의 사고 위험을 줄이기 위하여 개발된 제품으로 산악지역 등에서 내트래킹, 내부식성, 수밀성 및 전기적인 특성이 우수하다. 본 평가기술에서는 알루미늄 묘|복강선, 연선 및 절연체의 일반적인 특성과 트래킹성, 도체수밀, 내후성, 밀착도, 교류파괴전압 등의 주요한 평가시험에 대한 방법을 검토하여 평가시험에 적용하여 평가시험시 문제점을 도출하고 평가시험방법을 정립하고자 한다.