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허균영,권도훈 한국원자력학회 2024 Nuclear Engineering and Technology Vol.56 No.10
The PSA (Probabilistic Safety Assessment) is presented as a method of comprehensively evaluating the types of accidents that can occur at nuclear power plants. One of the key components to obtain technical success was the introduction of event tree analysis, and its strength and weakness has been reviewed and enhanced with the term, for instance, Integrated Deterministic-Probabilistic Safety Assessment (IDPSA) since 1980s. However, the technical and policy maturity of IDPSA appears to have room for improvement: the terminologies need to be arranged internationally, and there are no official standards or guidelines for the method itself. Due to a misperception of IDPSA, there are even concerns that appropriate contribution in risk assessment cannot be made. For this reason, surveys and focus group interviews, sharing development experiences, and the direction of regulation and R&D on IDPSA were conducted targeting PSA experts in Korea. In order to support such process, authors have structured an overview of the development history and technical features of IDPSA. Finally, we will explore the ways to achieve synergy between the deterministic safety analysis and PSA, which may the origin of motivation how to deal with dynamic variability more properly such that an undue risk can be minimized
INTERACTIVE SYSTEM DESIGN USING THE COMPLEMENTARITY OF AXIOMATIC DESIGN AND FAULT TREE ANALYSIS
허균영,이태식,SUNG-HEE DO 한국원자력학회 2007 Nuclear Engineering and Technology Vol.39 No.1
To efficiently design safety-critical systems such as nuclear power plants, with the requirement of high reliability, methodologies allowing for rigorous interactions between the synthesis and analysis processes have been proposed. This paper attempts to develop a reliability-centered design framework through an interactive process between Axiomatic Design (AD) and Fault Tree Analysis (FTA). Integrating AD and FTA into a single framework appears to be a viable solution, as they compliment each other with their unique advantages. AD provides a systematic synthesis tool while FTA is commonly used as a safety analysis tool. These methodologies build a design process that is less subjective, and they enable designers to develop insights that lead to solutions with improved reliability. Due to the nature of the two methodologies, the information involved in each process is complementary: a success tree versus a fault tree. Thus, at each step a system using AD is synthesized, and its reliability is then quantified using the FT derived from the AD synthesis process. The converted FT provides an opportunity to examine the completeness of the outcome from the synthesis process. This study presents an example of the design of a Containment Heat Removal System (CHRS). A case study illustrates the process of designing the CHRS with an interactive design framework focusing on the conversion of the AD process to FTA.
김현민,허균영,장윤석,이상환,김형대,박준석 한국원자력학회 2015 Nuclear Engineering and Technology Vol.47 No.2
Probabilistic safety assessment (PSA) has had a significant role in quantitative decisionmakingby finding design and operational vulnerabilities and evaluating cost-benefit inimproving such weak points. In particular, it has been widely used as the core methodologyfor risk-informed applications (RIAs). Even though the nature of PSA seeks realistic results,there are still “conservative” aspects. One of the sources for the conservatism is the assumptionsof safety analysis and the estimation of failure frequency. Surveillance, diagnosis,and prognosis (SDP), utilizing massive databases and information technology, isworth highlighting in terms of its capability for alleviating the conservatism in conventionalPSA. This article provides enabling techniques to solidify a method to provide timeandcondition-dependent risks by integrating a conventional PSA model with conditionmonitoring and prognostics techniques. We will discuss how to integrate the results withfrequency of initiating events (IEs) and probability of basic events (BEs). Two illustrativeexamples will be introduced: (1) how the failure probability of a passive system can beevaluated under different plant conditions and (2) how the IE frequency for a steamgenerator tube rupture (SGTR) can be updated in terms of operating time. We expect thatthe proposed model can take a role of annunciator to show the variation of core damagefrequency (CDF) depending on operational conditions