• Proceedings of the Korean Nuclear Society Conference
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• 1997.05a
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• pp.606-610
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• 1997

울진 원전 3,4 호기 확률론적 안전성 평가 (PSA) 모델을 risk monitor 모델로 변환하여 한국원자력연구소에서 개발한 risk monitor인 Risk Monster[1]에 설치하였으며 이를 이용하여 필수냉각수 계통(ESW;Essential Service Water) 펌프의 가동중 정비(on-line maintenance)의 가능성 여부를 연구하였다. ESW 펌프를 가동중 정비하더라도 안전성 측면에서 별 문제가 없으며 경제성 여부는 보다 정확한 검토가 요구되나 상당히 있는 것으로 판단된다. 한편 ESW펌프 한대의 고장이 원전 가동중에 미치는 위험도를 분석하였으며 그 결과 ESW펌프 한대의 고장에도 불구하고 원전 계속 가동에는 큰 문제가 없었다.

• Economic and Environmental Geology
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• v.42 no.4
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• pp.357-366
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• 2009

Since weathering weakens the rock fabric and exaggerates any structural weakness, it affects mechanical properties as well as physical and chemical properties of rock. Weathering leads to a decrease in density, strength, friction angle and cohesion, and subsequently it affects negatively on the stability of rock slope. The purpose of the study is to investigate the changes of the rock slope stability caused by discontinuities which have different weathering grades. For that, the discontinuity samples which are divided into two different weathering grades are obtained from the field and tested their mechanical properties such as JCS, JRC and residual friction angle. In order to evaluate the effects on the stability of slope due to weathering, the deterministic analysis is carried out. That is, the factors of safety for planar failure are calculated for rock masses which have two different weathering grades, such as fresh and weathered rock mass. However, since the JRC and friction angle values are widely scattered and the deterministic analysis cannot consider the variation, the factors of safety cannot represent properly the stability of the rock slope. Therefore, the probabilistic analysis has been used to consider the scattered values. In the deterministic analysis, the factors of safety for the fresh discontinuity and weathered discontinuity are 1.25 and 1.0, respectively. The results indicate the fresh discontinuities are stable for planar failure and the weathered discontinuities are marginally stable. However, the probabilities of failure for the fresh discontinuity and weathered discontinuity are 25.6% and 45.9%, respectively. This shows that both discontinuities are analyzed as unstable in the probabilistic analysis.

• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.1 s.47
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• pp.63-74
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• 2006

The seismic fragility analysis method has been used as a quantitative seismic safety evaluation method for the NPP(Nuclear Power Plant) structures and equipments. The seismic fragility analysis gives a realistic seismic capacity excluding the convertism included in the design stage. The conservatism is considered as the probabilistic parameters related to the response and capacity in the seismic fragility analysis. In this study, the displacement based seismic fragility analysis method was proposed based on the nonlinear dynamic analysis results. In this study, the seismic safety of the prestressed concrete containment building of KSNP(Korean Standard Nuclear Power Plant) was evaluated for the scenario earthquakes, neat-fault, far-fault, design earthquake and probability based scenario earthquake, which can be occurred in the NPP sites.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2013.04a
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• pp.27-28
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• 2013

이 논문에서는 신화재 확률론적 안전성평가 (PSA) 방법 중 정성적 분석 방법을 울진 3호기 원전에 적용한 결과를 기술하였다. 지금까지 대부분의 국내 원전 에서는 EPRI 화재 PSA 방법을 이용하여 화재 PSA를 수행해 왔었다. 최근 미국 규제기관과 산업체에서는 신화재 PSA 방법으로 NUREG/CR-6850을 개발하였다. 신화재 PSA 방법을 이용하여 울진 3호기를 정성적으로 분석한 결과 150개의 방화지역 중 75개 지역이 정량적 분석 대상으로 파악되었다. 이는 기존 EPRI 화재 PSA 방법으로 수행한 방화지역 수보다 23개 많았다. 또 화재 PSA 수행을 위한 기기 수는 770여개이고 케이블 수는 6,000여개로 나타났다.

• Journal of the Korea Society of Computer and Information
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• v.11 no.6 s.44
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• pp.261-267
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• 2006

In order to perform a probabilistic safety assessment (PSA), it requires a large number of data for various fields. And the quality of a PSA results have become more important thing of the risk assessment. As part of enhancing the PSA qualify, Korea Atomic Energy Research Institute is developing a full power Human Reliability Analysis (HRA) calculator to manage human failure events (HFEs) and to calculate the diagnosis human error probabilities and execution human error probabilities. This paper introduces the development process and an overview of a standard HRA method for nuclear power plants. The study was carried out in three stages; 1) development of the procedures and rules for a standard HRA method. 2) design of a system structure, 3) development of the HRA calculator.

• Nuclear industry
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• v.23 no.6 s.244
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• pp.48-56
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• 2003

본 연구의 목표는 원전의 안전성 확보에 기여할 수 있는 조직 및 인적 요인의 평가에 대한 시스템 다이나믹스(System Dynamics) 모델을 만드는데 있다. 기존의 연구는 크게 인간 공학 혹은 확률론적 안전성 평가와 같은 공학적 방법과 조직 사회학적 접근으로 구분할 수 있다. 양 방법은 조직 및 인적 요인이 무엇인지를 밝혀주고 인적 실수를 줄이기 위한 지침을 제공해 준다. 그러나 인자들간의 상호 독립성의 가정은 원전에서 일어나고 있는 요인들간의 상호 작용을 설명하는데 어려움을 지닌다. 이러한 제약 사항을 극복하기 위해서 조직 및 인적 요인 사이의 인과 관계를 보여줄 수 있는 시스템 다이나믹스 모델을 개발하였다. 개발된 모델을 통하여 리더십, 직원 수의 조정, 각 부서별 업무량의 조정 등을 조작하면서 모델의 사용자들은 조직 측면에서 원전의 안전성이 어떻게 변화하는가를 확인할 수 있다. 시뮬레이션을 통해서 사용자들은 관리적인 시사점을 얻을 수 있을 것이다.

• Computational Structural Engineering
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• v.2 no.4
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• pp.89-98
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• 1989

In order to take account of the statistical properties of random variables used in the structural analysis, the conventional approach usually adopts the safety factor based on past experiences for the qualitative assessment of structural safety problem. Recently, new approach based on the probabilistic concept has been applied to the assessment of structural safety in order to circumvent the difficulties of the conventional approach in choosing the appropriate safety factor. Thus, computer program called "Probabilistic finite element method" is developed by incorporating the probabilistic concept into the conventional matrix method in order to investigate the effects of the random variables on the final output of the structural analysis. From the comparison of some examples, it can be concluded that the PFEM developed in this study deals consistently with the uncertainty of random variables and provides the rational tool for the assessment of structural safety of plane frame.

• 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 Society of Naval Architects of Korea
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• v.28 no.2
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• pp.251-267
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• 1991

Plastic strength analysis using plastic failure mode as a limit state is adopted instead of a conventional elastic structural analysis to predict the ultimate strength of Web frame idealized by a plane frame. Linear programming arid Compact procedure are developed for determining the collapse load factor. It is found that the final results are good agreement with the results of Elasto-plastic analysis. Besides, the redundant structures like Web frame is known to have multiple failure modes. Web frame may collapse under any of the possible failure modes. Thus, the identification of these possible failure modes is necessary and very important in the reliability analysis of Web frame. In order to deal with multiple failure modes, automatic generation method of all failure modes and basic failure modes is used for selecting the dominant failure modes. The probability of failure pastic collapse of Web frame is calculated using these dominant failure modes. The safety of Web frame is asscssed and compared by performing the deterministic and probabilistic analysis.

• Journal of the Society of Naval Architects of Korea
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• v.30 no.1
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• pp.115-124
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• 1993

A structural system reliability analysis is studied for the safety assessment of midship section. Probabilistically dominant collapse modes are generated by Element Replacement Method and Incrimental Load Method. In order to avoid generating the same modes repeatedly, it is branched at final plastic hinge. Using first and second order bound methods, system failure probability of midship section is computed and compared with deterministic load factor method to show the usefulness of the proposed method.