• Nuclear Engineering and Technology
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• 제50권8호
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• pp.1217-1233
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• 2018

Following a surge of interest in multi-unit risk in the last few years, many recent studies have suggested methods for multi-unit probabilistic safety assessment (MUPSA) and addressed several related aspects. Most of the existing studies though focused on two-unit nuclear power plant (NPP) sites or used rather simplified probabilistic safety assessment (PSA) models to demonstrate the proposed approaches. When considering an NPP site with three or more units, some approaches are inapplicable or yield very conservative results. Since the number of such sites is increasing, there is a strong need to develop and validate practical approaches to the related MUPSA. This article provides several detailed approaches that are applicable to multi-unit Level 1 PSA for sites with up to six or more reactor units. To validate the approaches, a multi-unit Level 1 PSA model is developed and the site core damage frequency is estimated for each of four representative multi-unit initiators, as well as for the case of a simultaneous occurrence of independent single-unit initiators in multiple units. For this purpose, an NPP site with six identical OPR-1000 units is considered, with full-scale Level 1 PSA models for a specific OPR-1000 plant used as the base single-unit models.

• Nuclear Engineering and Technology
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• 제52권5호
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• pp.975-983
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• 2020

Since the Fukushima Daiichi accident in 2011, concerns for the safety of multi-unit Nuclear Power Plant (NPP) sites have risen. This is because more than 70% of NPP sites are multi-unit sites that have two or more NPP units and a multi-unit accident occurred for the first time. After this accident, Probability Safety Assessment (PSA) has been considered in many countries as one of the tools to quantitatively assess the safety for multi-unit NPP sites. One of the biggest concerns for a multi-unit accident such as Fukushima is that the consequences (health and economic) will be significantly higher than in the case of a single-unit accident. However, many studies on multi-unit PSA have focused on Level 1 & 2 PSA, and there are many challenges in terms of public acceptance due to various speculations without an engineering background. In this study, two kinds of multi-unit Level 3 PSA for multi-unit site have been carried out. The first case was the estimation of multi-unit risk with conservative assumptions to investigate the margin between multi-unit risk and QHO, and the other was to identify the effect of time delays in releases between NPP units on the same site. Through these two kinds of assessments, we aimed at investigating the level of multi-unit risk and understanding the characteristics of risk in a multiunit context.

• Nuclear Engineering and Technology
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• 제44권5호
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• pp.437-452
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• 2012

The Tohoku earthquake (Mw9.0) occurred on March 11, 2011 and caused a large tsunami. The Fukushima Dai-ichi NPP (F1-NPP) were overwhelmed by the tsunami and core damage occurred. This paper describes the overview of F1-NPP accident and the usability of tsunami PRA at Tohoku earthquake. The paper makes reference to the following current issues: influence on seismic hazard of gigantic aftershocks and triggered earthquakes, concepts for evaluating core damage frequency considering common cause failure with correlation coefficient against seismic event at multi units and sites, and concepts of "seismic-tsunami PSA" considering a combination of seismic motion and tsunami effects.

• 대한교통학회지
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• 제17권2호
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• pp.41-53
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• 1999

공동주택 입주자들의 자동차 보유율의 급증으로 인한 공동주택 단지에서의 주차란에 대하여 정부에서는 그간 주차장 공급강화 정책으로 일관하였다. 하지만 주차장 공급강화는 기존 공동주택에서의 주차란 완화보다는 신규 공동주택 주차장 공급에 치중되어 있으며, 일률적 공급규정은 다양한 개발여건에서의 주차 수요에 대처하기에는 한계가 있고, 공동주택 단지의 녹지 면적 감소를 초래하고 있다. 또한 차량을 보유치 않은 입주자와 차량을 2대 이상을 보유한 입주자들과의 주차장 사용 형평상에 문제가 제기되고 있으며 지하 주차장 건설에 따른 주택원가 상승의 가장 큰 요인으로 작용하여 저소득층의 주택구매에 큰 걸림돌이 되고 있다. 본 연구는 국내·외 공동주택 단지에서의 다양한 주차장 공급 및 수요관리방안 분석을 통하여 다가오는 21세기의 국내 공동주택 주차장 정책 방향을 제시에 목적이 있다. 연구결과 전국의 공동주택에서는 도시규모, 주택평형, 단지규모, 준공년도 변화에 차이 없이 다양한 주차공급방식 도입, 주차전용제 실시, 1가구 2차량 주차 이용료부과, 단지내 주차장 증 가 및 단지주변 민영·공영주차장 활성화 외부차량 불법주차단속 강화를 통하여 현재의 공동주택 주차란에 대처하기를 원하고 있다. 특히 주차란이 매우 심각한 중형 및 소형 공동주택과 중소도시 소재 공동주택에서는 대도시 소재 공동주택 및 대형 공동주택보다 지자체에 의한 다양한 주차장 공급방식 적용과 철저한 불법주차단속을 통하여 현재의 주차란에 대처하기를 적극적으로 원하고 있어 주택규모 및 도시규모 변화에 따른 차별적 공동주택 주차장 공급 및 관리방안시행이 요망된다.

• Nuclear Engineering and Technology
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• 제53권2호
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• pp.386-392
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• 2021

MACCS (MELCOR Accident Consequence Code System), WinMACCS, and MelMACCS now facilitate a multi-unit consequence analysis. MACCS evaluates the consequences of an atmospheric release of radioactive gases and aerosols into the atmosphere and is most commonly used to perform probabilistic safety assessments (PSAs) and related consequence analyses for nuclear power plants (NPPs). WinMACCS is a user-friendly preprocessor for MACCS. MelMACCS extracts source-term information from a MELCOR plot file. The current development can combine an arbitrary number of source terms, representing simultaneous releases from a multi-unit facility, into a single consequence analysis. The development supports different release signatures, fission product inventories, and accident initiation times for each unit. The treatment is completely general except that the model is currently limited to collocated units. A major practical consideration for performing a multi-unit PSA is that a comprehensive treatment for more than two units may involve an intractable number of combinations of source terms. This paper proposes and evaluates an approach for reducing the number of calculations to be tractable, even for sites with eight or ten units. The approximation error introduced by the approach is acceptable and is considerably less than other errors and uncertainties inherent in a Level 3 PSA.

• Nuclear Engineering and Technology
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• 제49권2호
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• pp.286-294
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• 2017

The events at the Fukushima Daiichi Nuclear Power Station in March 2011 point out, among other matters, that concurrent accidents at multiple units of a site can occur in reality. Although site risk has been deterministically considered to some extent in nuclear power plant siting and design, potential occurrence of multi-unit accident sequences at a site was not investigated in sufficient detail thus far in the nuclear power community. Therefore, there is considerable worldwide interest and research effort directed toward multi-unit site risk assessment, especially in the countries with high-density nuclear-power-plant sites such as Korea. As the technique of probabilistic safety assessment (PSA) has been successfully applied to evaluate the risk associated with operation of nuclear power plants in the past several decades, the PSA having primarily focused on single-unit risks is now being extended to the multi-unit PSA. In this paper we first characterize the site risk with explicit consideration of the risk associated with spent fuel pools as well as the reactor risks. The status of multi-unit risk assessment is discussed next, followed by a description of the emerging issues relevant to the multi-unit risk evaluation from a practical standpoint.

• 한국실내디자인학회논문집
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• 제24권1호
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• pp.169-177
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• 2015

The study aimed to classify the types of domestic dormitory furniture, and analyze the characteristics of each furniture type based on the empirical research methodology. The study consisted of literature review and field visit followed by survey and in-depth interview. The researchers collected 140 images of furniture from the web sites of 87 universities. Using affinity diagram, the dormitory furniture was classified into four different types: single fixed type, single semi-fixed type, multi fixed type, and multi semi-fixed type. The finding showed that the use of single fixed type was dominant in the domestic dormitory room, which had competitive price and easy maintenance. Both single fixed type and multi fixed type turned out to be lack of storage space. Meanwhile, both single semi-fixed type and multi semi-fixed type got the high value on the space efficiency due to the multi function. However, these two types could only be applied to a wide space enough for the furniture to be transformed and extended. The study analyzed the main characteristics of the dormitory furniture according to the type classification, and it is expected that this empirical study could work as a medium and database for the upcoming dormitory furniture design studies.

• Imaging Science in Dentistry
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• 제42권2호
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• pp.65-70
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• 2012

Purpose : The aim of this study was to compare the effective dose for imaging of mandible between multi-detector computed tomography (MDCT) and cone-beam computed tomography (CBCT). An MDCT with low dose technique was also compared with them. Materials and Methods : Thermoluminescent dosimeter (TLD) chips were placed at 25 organ sites of an anthropomorphic phantom. The mandible of the phantom was exposed using 2 different types of MDCT units (Somatom Sensation 10 for standard-dose MDCT, Somatom Emotion 6 for low-dose MDCT) and 3 different CBCT units (AZ3000CT, Implagraphy, and Kavo 3D eXaM). The radiation absorbed dose was measured and the effective dose was calculated according to the ICRP 2007 report. Results : The effective dose was the highest for Somatom Sensation 10 (425.84 ${\mu}Sv$), followed by AZ3000CT (332.4 ${\mu}Sv$), Somatom Emotion 6 (199.38 ${\mu}Sv$), and 3D eXaM (111.6 ${\mu}Sv$); it was the lowest for Implagraphy (83.09 ${\mu}Sv$). The CBCT showed significant variation in dose level with different device. Conclusion : The effective doses of MDCTs were not significantly different from those of CBCTs for imaging of mandible. The effective dose of MDCT could be markedly decreased by using the low-dose technique.

• 국제학술발표논문집
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• The 4th International Conference on Construction Engineering and Project Management Organized by the University of New South Wales
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• pp.304-310
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• 2011

The populations of major cities in Australia are increasing rapidly and facing an acute housing shortage. Traditional apartment procurement techniques involve lengthy lead-times and factory-based, or offsite manufactured (OSM) multi-storey apartment buildings may offer the opportunity to help fulfill the need by significantly reducing build times. Other advantages of OSM may include superior quality, low weight ratios, economies of scale achieved through repetition of prefabricated units, use on infill sites, sustainable design standards and better occupational health and safety. There are also positive labour and training implications, which may help to alleviate an industry-wide shortage of skills through use of semi-skilled labour. Previous uncertainties about the adoption of offsite due to the high capital costs and perception issues were generally based on pre-cast concrete structures, which are quite a different building type in terms of flexibility, construction, delivery and finishes. Identification of drivers and constraints assists in the determination of current industry status, allows for a benchmark to be established and future opportunities and directions for OSM to be determined.

• 토지주택연구
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• 제15권3호
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• pp.129-140
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• 2024

본 연구는 매입임대주택을 시공하는데 모듈러 공법을 활용할 수 있는 가능성을 탐구했다. 특히 규모가 작은 매입임대주택을 중심으로 조사하여, 이러한 주택이 기획부터 시공까지의 공급 기간을 단축하고 거주자의 요구를 유연하게 수용할 수 있는 장점을 가지고 있음을 확인했다. 이러한 민관 협력은 지역사회 계획에도 확장되어 전통적인 임대주택 모델을 벗어나 지역 수요에 맞는 맞춤형 모델을 구축하는데 활용될 수 있다. 현재 매입임대주택은 대도시에서 수요와 공급이 많으며, 주로 다세대 주택, 다가구주택, 연립주택으로 구성되어 있다. 상자형 모듈러주택을 활용할 때에는 모듈 크기와 운반성을 고려하는 것이 중요하며, 이러한 공장 제작 방식을 활용하면 공급 효율성과 품질 향상을 도모할 수 있다. 본 연구에서는 모듈러주택 모델을 계획하고 건설 및 철거 효율성을 높일 수 있는 세 가지 건설기술을 제안했다. 중간에 기둥이 없는 세대 평면, 상자형 모듈러 공법을 활용한 코어 제작, 건축 구성재의 공업화 및 건식 공법 등이 그 예이다. 이러한 공법을 활용하여 노후화된 주택 정비와 수요 대응을 위해 모듈러 공법을 활용한 매입임대주택의 신축 모델을 제시했다. 이 모델은 36m²과 54m² 크기의 16세대로 구성되었으며, 대지의 규모가 660m² 이상이고, 6m 이상 도로에 접한 경우에는 다른 대지에서도 활용할 수 있다. 근거리의 여러 필지에 신축할 경우 클러스터형 개발도 고려하여 건설 효율성을 높일 수 있다.