• Nuclear Engineering and Technology
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• 제51권6호
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• pp.1540-1553
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• 2019

A nuclear power plant (NPP) is a highly complex system-of-systems as manifested through its internal systems interdependence. The negative impact of such interdependence was demonstrated through the 2011 Fukushima Daiichi nuclear disaster. As such, there is a critical need for new strategies to overcome the limitations of current risk assessment techniques (e.g. the use of static event and fault tree schemes), particularly through simulation of the nonlinear dynamic feedback mechanisms between the different NPP systems/components. As the first and key step towards developing an integrated NPP dynamic probabilistic risk assessment platform that can account for such feedback mechanisms, the current study adopts a system dynamics simulation approach to model the thermal dynamic processes in: the reactor core; the secondary coolant system; and the pressurized water reactor. The reactor core and secondary coolant system parameters used to develop system dynamics models are based on those of the Palo Verde Nuclear Generating Station. These three system dynamics models are subsequently validated, using results from published work, under different system perturbations including the change in reactivity, the steam valve coefficient, the primary coolant flow, and others. Moving forward, the developed system dynamics models can be integrated with other interacting processes within a NPP to form the basis of a dynamic system-level (systemic) risk assessment tool.

• 한국건설관리학회논문집
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• 제20권5호
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• pp.125-136
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• 2019

본 연구는 국내 대형 건설 기업이 수행한 124건의 해외사업에 대해 입찰 전 예측 리스크, 수주 후 실제 리스크, 예비비 반영률, 원가 상승률 등을 조사하였다. 이를 기반으로 플랜트, 건축, 토목 공종별 예측 리스크 수준, 실제 리스크 수준, 입찰 전 예측 리스크와 예비비 간 관계, 실제 리스크와 원가 상승률의 상관성을 분석하여 다음과 같은 결론을 얻었다. 첫째, 플랜트와 토목 사업은 건축 사업에 비해 예측 리스크와 실제 리스크 수준이 높았다. 특히, 플랜트와 토목 사업에서는 국가 리스크가 가장 높았으나 건축사업에서는 프로젝트 리스크가 가장 높았던 것으로 나타났다. 둘째, 플랜트와 토목 사업이 건축 사업보다 예비비를 많이 설정하였으나 입찰 전 예측 리스크 수준과는 상관성이 없었다. 이는 우리 기업의 예비비 산정에 문제가 있음을 내포하고 있다. 셋째, 세 개 공종 모두 실제 리스크 발생 수준과 원가 상승률 사이에 유의미한 상관성이 존재하는 것으로 나타났다. 이는 리스크 관리가 실행원가 관리에 중요한 요소임을 보여준다. 본 연구에서 도출된 결과는 국내 기업들의 공종별로 차별화된 보다 실전적인 리스크 관리를 지원할 것으로 기대된다.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1998년도 추계학술발표회요약집
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• pp.113-113
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• 1998

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1997년도 추계학술발표회논문집(1)
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• pp.713-718
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• 1997

In the TMI-2 accident, approximately twenty(20) tons of molten core material drained into the lower plenum. Early advanced light water reactor (LWR) designs assumed a lower head failure and incorporated various measures for ex-vessel accident mitigation. However, one of the major findings from the TMI-2 Vessel Investigation Project was that one part of the reactor lower head wall estimated to have attained a temperature of 1100$^{\circ}C$ for about 30 minutes has seemingly experienced a comparatively rapid cooldown with no major threat to the vessel integrity. In this regard, recent empirical and analytical studies have shifted interests to such in-vessel retention designs or strategies as reactor cavity flooding, in-vessel flooding and engineered gap cooling of the vessel Accurate thermohydrodynamic and creep deformation modeling and rupture prediction are the key to the success in developing practically useful in-vessel accident/risk management strategies. As an advanced in-vessel design concept, this work presents the COrium Attack Syndrome Immunization Structures (COASIS) that are being developed as prospective in-vessel retention devices for a next-generation LWR in concert with existing ex-vessel management measures. Both the engineered gap structures in-vessel (COASISI) and ex-vessel (COASISO) are demonstrated to maintain effective heat transfer geometry during molten core debris attack when applied to the Korean Standard Nuclear Power Plant(KSNPP) reactor. The likelihood of lower head creep rupture during a severe accident is found to be significantly suppressed by the COASIS options.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2019년도 춘계 학술논문 발표대회
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• pp.230-231
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• 2019

The nuclear power plant construction project is large-scale, has various stakeholders and computer system, and is produced and managed a large amount of information. The domestic nuclear power plant construction project has accumulated data based on many years of experience in the system. It has the competitiveness to suggeest alternatives that meet the requirement of the client in the overseas nuclear power plant project. Earned value management, which integrates schedule and cost, is possible to risk management. It was developed the earned value management system considering the the actual data properties and types of the preceding nuclear power plant construction projects. It will be able to increase the nuclaer power plant export competieiveness. Therefore, it was palned to carry out future stuies so that it be able to complement the measure to integrate cost and schedule in consideration of actual data(quantity of activity, etc.).

• Nuclear Engineering and Technology
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• 제12권3호
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• pp.194-213
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• 1980

The paper describes and quantifies the wastes arising in the nuclear fuel cycle for Light Water Reactors, Heavy Water Reactors and Fast Breeder Reactors. The management and disposal technologies are indicated, together with their environmental impacts. Both once-through and uranium-plutonium recycle systems are evaluated, and comparisons are made on the basis of tingle reference technologies for waste management, and for one gigawatt/year of electricity generation. Environmental impacts are assessed, particularly that of health and safety, and a reference costing system is applied purely as a basis for comparing the fuel cycles. From this study it call be concluded generally that the relative differences of the impacts of waste management and disposal between the selected fuel cycles are not decisive factors in choosing a fuel cycle. Employing the technologies assumed, the radioactive wastes from any of the fuel cycles studied can be managed and disposed of with a high degree of safety and without undue risk to man or the environment. The cost of waste management and disposal is only a few percent of the value of the electricity generated and does not vary greatly between fuel cycles.

• Nuclear Engineering and Technology
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• 제44권5호
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• pp.453-458
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• 2012

A major issue for all nuclear stakeholders is to keep the probability of circumstances that could lead to core damage as low as possible. In addition, for NPP, appropriate accident management provisions are to be implemented to limit the consequences associated with an accident. Development and application of L2 PSA is a structured way to demonstrate that such objectives are achieved. The paper presents the efforts recently done in Europe to harmonize some best-practices in that field, from research area to risk assessment. The Fukushima Daiichi accident reiterated the importance of these activities and the need to efficiently reinforce the NPP safety based on risk assessment conclusions. New perspectives in Europe are briefly presented.

• Nuclear Engineering and Technology
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• 제40권5호
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• pp.327-348
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• 2008

A risk-informed regulatory approach implies that risk insights be used as supplement of deterministic information for safety decision-making purposes. In this view, the use of risk assessment techniques is expected to lead to improved safety and a more rational allocation of the limited resources available. On the other hand, it is recognized that uncertainties affect both the deterministic safety analyses and the risk assessments. In order for the risk-informed decision making process to be effective, the adequate representation and treatment of such uncertainties is mandatory. In this paper, the risk-informed regulatory framework is considered under the focus of the uncertainty issue. Traditionally, probability theory has provided the language and mathematics for the representation and treatment of uncertainty. More recently, other mathematical structures have been introduced. In particular, the Dempster-Shafer theory of evidence is here illustrated as a generalized framework encompassing probability theory and possibility theory. The special case of probability theory is only addressed as term of comparison, given that it is a well known subject. On the other hand, the special case of possibility theory is amply illustrated. An example of the combination of probability and possibility for treating the uncertainty in the parameters of an event tree is illustrated.

• Nuclear Engineering and Technology
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• 제51권8호
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• pp.2034-2041
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• 2019

Public acceptance has become the most critical question for sustainable development of nuclear energy in recent decades. Many researches concentrated on risk and benefit perception, which were deemed as the most influential factors of Public Acceptance of Nuclear Energy (PANE). But few researches focused on psychological factors including regulatory focus. Therefore, this paper aimed to explore the moderating effect of regulatory focus on PANE based on Regulatory Focus Theory in order to find ways to increase/decrease PANE. An Internet-based survey had been carried out in China nationwide. The results indicated that trust in government was positively related to PANE and this relationship was mediated by risk and benefit perception. In addition, the strength of the associations between risk and benefit perception and PANE were moderated by regulatory focus, consisting of prevention focus and promotion focus. Prevention focus strengthened the negative relationship between risk perception and PANE, while promotion focus weakened. Moreover, promotion focus weakened the positive relationship between benefit perception and PANE, but no significant moderating effect of prevention focus was founded on the relationship between benefit perception and PANE. Some policy implications were also proposed on the basis of above-mentioned findings.

• Nuclear Engineering and Technology
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• 제45권6호
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• pp.791-794
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• 2013

Since the Fukushima accident in 2011, the importance of the electrical systems in nuclear power plants (NPPs) has been emphasized. The result has been that NPP regulators are enhancing their monitoring of loss of offsite power (LOOP) events. Korea Hydro & Nuclear Power Co. (KHNP) is reviewing the status and issues related to LOOPs, and is attempting to establish specific countermeasures to prevent LOOPs, because they can have severe consequences in the complicated maintenance schedule during an outage. A starting point for preventing LOOPs is the control of the loss of voltage (LOV)-initiating components. In order to reflect this in the risk assessment program, an LOV monitor is being developed for use during plant outages.