• 한국안전학회지
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• 제32권3호
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• pp.160-171
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• 2017

US national research laboratories developed the first Vital Area Identification (VAI) method for the physical protection of nuclear power plants that is based on Event Tree Analysis (ETA) and Fault Tree Analysis (FTA) techniques in 1970s. Then, Korea Atomic Energy Research Institute proposed advanced VAI method that takes advantage of fire and flooding Probabilistic Safety Assessment (PSA) results. In this study, in order to minimize the burden and difficulty of VAI, (1) a set of streamlined VAI rules were developed, and (2) this set of rules was applied to PSA fault tree and event tree at the initial stage of VAI process. This new rule-based VAI method is explained, and its efficiency and correctness are demonstrated throughout this paper. This new rule-based VAI method drastically reduces problem size by (1) performing PSA event tree simplification by applying VAI rules to the PSA event tree, (2) calculating preliminary prevention sets with event tree headings, (3) converting the shortest preliminary prevention set into a sabotage fault tree, and (4) performing usual VAI procedure. Since this new rule-based VAI method drastically reduces VAI problem size, it provides very quick and economical VAI procedure. In spite of an extremely reduced sabotage fault tree, this method generates identical vital areas to those by traditional VAI method. It is strongly recommended that this new rule-based VAI method be applied to the physical protection of nuclear power plants and other complex safety-critical systems such as chemical and military systems.

• 식물분류학회지
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• 제36권1호
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• pp.21-40
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• 2006

본 연구에서는 한국산 여뀌속 Persicaria절 분류군들에 대학 핵 리보오솜 (nrDNA)의 ITS 염기서열 분석을 수행하여 본 절 분류군들의 유연관계를 추정하고자 하였다, 본 연구결과 본 절 분류군의 nrDNA ITS 구간 염기서열은 본 절 분류군의 분류학적 타당성, 한계 및 계급설정 및 분류군 간의 계통적 유연관계를 추정하는 데 있어 유용한 것으로 나타났다. ITS 염기서열 분석결과 얻어진 neighbor-joining tree에서 본 절 한국산 분류군들은 크게 P.amphibium과 나머지 분류군들을 포함하는 ground의 2개의 계열로 구분되었다. 나머지 분류군들을 포함하는 두번째 계열은 다시 (1) P. lapathifolium, (2) P. persicaria와 P. viscoferum, (3) P. orientale 및 P. viscosum, (4) P. japonicum 및 (5) P. longisetum, P. erecto-minus var. koreense, P. caespitosum var. laxiflorum, P. hydropiper, P. pubescence, P. tinctorium, P. foliosum, P. trigonocarpum을 포함하는 group으로 세분되었다. 이러한 결과는 과거 형태적 식별형질에 의해 제안되었던 본 절 분류군간의 유연관계와 근본적으로 일치하였다.

• Nuclear Engineering and Technology
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• 제39권1호
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• pp.51-62
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• 2007

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.

• 생명과학회지
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• 제26권11호
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• pp.1341-1344
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• 2016

보길도에서 자라고 있는 황칠나무(Dendropanax morbifera)를 구입하여, 캘러스로 유도한 후, ribosomal DNA(nrDNA)의 internal transcribed spacer (ITS) region의 염기서열을 결정하였다 보길도의 황칠나무(Dendropanax morbifera)의 ITS region의 염기서열을 분석한 결과, 총 689염기를 결정하였다. 결정된 689염기 중에서 ITS1은 222 개염기, 5.8S rDNA는 160염기, ITS2는 233염기인 것으로 판명되었다. GenBank의 BLAST 프로그램(http://www.ncbi.nlm.nih.BLAST)을 사용하여 GenBank/EMBL/DDBJ에 등록되어 있는 Dendropanax 속 33의 염기서열을 수집한 후 multiple alignment를 수행한 결과, 유사도는 99.7%(D. chevalieri)에서 92.6%(Dendropanax arboreus)로 나타났으며, 일본황칠나무(D. trifidus)와는 유사도가 99.4%로 판명되었다.

• Nuclear Engineering and Technology
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• 제40권5호
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• pp.397-408
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• 2008

This paper describes the application of a software fault tree analysis (FTA) as one of the analysis techniques for a software safety analysis (SSA) at the design phase and its analysis results for the safety-critical software of a digital reactor protection system, which is called the KNICS RPS, being developed in the KNICS (Korea Nuclear Instrumentation & Control Systems) project. The software modules in the design description were represented by function blocks (FBs), and the software FTA was performed based on the well-defined fault tree templates for the FBs. The SSA, which is part of the verification and validation (V&V) activities, was activated at each phase of the software lifecycle for the KNICS RPS. At the design phase, the software HAZOP (Hazard and Operability) and the software FTA were employed in the SSA in such a way that the software HAZOP was performed first and then the software FTA was applied. The software FTA was applied to some critical modules selected from the software HAZOP analysis.

• Nuclear Engineering and Technology
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• 제30권1호
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• pp.58-74
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• 1998

A PC window-based computer code, CONPAS (CONtainment Performance Analysis System), has been developed to integrate the numerical, graphical, and results-operation aspects of Level 2 probabilistic safety assessments (PSA) for nuclear power plants automatically. As a main logic for accident progression analysis, it employs a concept of the small containment phenomenological event tree (CPET) helpful to trace out visually individual accident progressions and of the detailed supporting event tree (DSET) for its detailed quantification. For the integrated analysis of Level 2 PSA, the code utilizes five distinct, but closely related modules. Its computational feasibility to real PSAs has been assessed through an application to the UCN 3&4 full scope Level 2 PSA. Compared with other existing computer codes for Level 2 PSA, the CONPAS code provides several advanced features: (1) systematic uncertainty analysis / importance analysis / sensitivity analysis, (2) table / graphical display & print, (3) employment of the recent Level 2 PSA technologies, and (4) highly effective user interface. The main purpose of this paper is to introduce the key features of CONPAS code and results of its feasibility study.

• Nuclear Engineering and Technology
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• 제54권12호
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• pp.4560-4570
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• 2022

Dynamic fault tree (DFT) and its related research methods have received extensive attention in safety analysis and reliability engineering. DFT can perform reliability modelling for systems with sequential correlation, resource sharing, and cold and hot spare parts. A technical modelling method of DFT is proposed for modelling ship collision accidents and loss-of-coolant accidents (LOCAs). Qualitative and quantitative analyses of DFT were carried out using the cutting sequence (CS)/extended cutting sequence (ECS) method. The results show nine types of dynamic fault failure modes in ship collision accidents, describing the fault propagation process of a dynamic system and reflect the dynamic changes of the entire accident system. The probability of a ship collision accident is 2.378 × 10^-9 by using CS. This failure mode cannot be expressed by a combination of basic events within the same event frame after an LOCA occurs in a marine nuclear reactor because the system contains warm spare parts. Therefore, the probability of losing reactor control was calculated as 8.125 × 10^-6 using the ECS. Compared with CS, ECS is more efficient considering expression and processing capabilities, and has a significant advantage considering cost.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1996년도 춘계학술발표회논문집(2)
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• pp.493-498
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• 1996

A PC window-based computer code, CONPAS(CONtainment Performance Analysis System), has been developed to integrate the numerical, graphical and results-operation aspects of Level 2 probabilistic safety assessments (PSA) for nuclear power plants automatically. As a main logic for accident progression analysis, it employs a concept of the small containment phenomenological event tree(CPET) helpful to trace out visually individual accident progressions and of the large supporting event tree(LSET) for its detailed quantification. Compared with other existing computer codes for Level 2 PSA, the CONPAS code provides several advanced features: computational aspects including systematic uncertainty analysis, importance analysis, and sensitivity analysis, reporting aspects including tabling and graphic, and user-friend interface.

• Nuclear Engineering and Technology
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• 제53권2호
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• pp.498-508
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• 2021

Micro reactors are increasingly being considered for utilization as distributed power sources. Hence, the probabilistic safety assessment (PSA) of a direct supercritical-CO₂-cooled fast reactor, called micro modular reactor (MMR), was performed in this study; this reactor was developed using innovative design concepts. It adopted a modular design and passive safety systems to minimize site constraints. As the MMR is in its conceptual design phase, design weaknesses and valuable safety insights could be identified during PSA. Level 1 internal event PSA was carried out involving literature survey, system characterization, identification of initiating events, transient analyses, development of event trees and fault trees, and quantification. The initiating events and scenarios significantly contributing to core damage frequency (CDF) were determined to identify design weaknesses in MMR. The most significant initiating event category contributing to CDF was the transients with the power conversion system initially available category, owing to its relatively high occurrence frequency. Further, an importance analysis revealed that the safety of MMR can be significantly improved by improving the reliability of reactor trip and passive decay heat removal system operation. The findings presented in this paper are expected to contribute toward future applications of PSA for assessing unconventional nuclear reactors in their conceptual design phases.

• 생명과학회지
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• 제22권3호
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• pp.285-292
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• 2012

조팝나무속(genus Spiraea) 식물은 다년생 목본으로 주로 아시아와 유럽에 분포하고 있다. 한국의 14종을 포함한 전 세계 38분류군에 대해 핵 내 리보솜 전사 서열(ITS)로 이 속의 유전적 관계를 평가하였다. 이 분자생물학적 자료로 분류군의 분지군은 잘 분리되었다. 47 계통(38 분류군: 14개 한국 분류군, 33개 세계 분류군, 9개 중복 분류군). 전체 689 bp 중에서452자리는 절약-정보적이었고, 527자리는 변이를 나타내었으나 절약-비정보적이었고, 159자리는 분류군 전체에서 변이가 전혀 없었다. 비록 계통도에서 잘 분리되었지만 형태적 특성과 지리적 분포와는 일치하지 않았다. 분리되는 자리수는 430이었으며 핵산 다양도(${\pi}$)는 0.281이였다. 중립가설 하에서 Tajima 검증 통계값(D) 은 0.5보다 큰 2.325였다. 따라서 자연 도태가 유전적 변이를 증가시키는 방향으로 작용하고 있었다.