• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.4
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• pp.25-36
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• 2021

This study analyzed the causes of flood accidents, such as isolation and lost footing accidents in Dorimcheon, to provide legal and institutional improvements. For cause analysis, Field Investigation, Stakeholder Interview, Report, manual, Law et al. Review, Analysis of water level change characteristics, automatic alarm issuance standard level analysis, and evacuation time according to river control were evaluated. Dorimcheon has the characteristics of a typical urban river, which is disadvantageous in terms of water control. In addition, the risk of flood accidents is high because the section where fatal accidents occur forms sharply curved channels. Tripping and isolation accidents occur in the floodplain watch and evacuation stage, which is the stage before the flood watch and warning is issued. Because floodplain evacuation is issued only when the water level rises to the floodplain, an immediate response according to the rainfall forecast is essential. Furthermore, considering that the rate of water level rise is up to 2.62 cm/min in Sillimgyo 3 and Gwanakdorimgyo, sufficient evacuation time is not secured after the floodplain watch is issued. Considering that fatal accidents occurred 0.46 m below the standard water level for the flood watch, complete control is very important, such as blocking the entry of rivers to prevent accidents. Based on these results, four improvement measures were suggested, and it is expected to contribute to the prevention of Tripping and Isolation Accidents occurring in rivers.

• Nuclear Engineering and Technology
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• v.47 no.2
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• pp.157-164
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• 2015

Nuclear power plants have logical loop structures in their system configuration. This paper explains the method to solve a loop structure in reliability analysis. As examples of loop structured systems, the reactor core isolation cooling system and high-pressure core injection system of a boiling water reactor are considered and analyzed under a station blackout accident condition. The analysis results show the important role of loop structures under severe accidents. For the evaluation of the safety of nuclear power plants, it is necessary to accurately evaluate a loop structure's reliability.

• Nuclear Engineering and Technology
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• v.55 no.3
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• pp.814-826
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• 2023

Sensor faults in nuclear power plant instrumentation have the potential to spread negative effects from wrong signals that can cause an accident misdiagnosis by plant operators. To detect sensor faults and make accurate accident diagnoses, prior studies have developed a supervised learning-based sensor fault detection model and an accident diagnosis model with faulty sensor isolation. Even though the developed neural network models demonstrated satisfactory performance, their diagnosis performance should be reevaluated considering real-time connection. When operating in real-time, the diagnosis model is expected to indiscriminately accept fault data before receiving delayed fault information transferred from the previous fault detection model. The uncertainty of neural networks can also have a significant impact following the sensor fault features. In the present work, a pilot study was conducted to connect two models and observe actual outcomes from a real-time application with an integrated system. While the initial results showed an overall successful diagnosis, some issues were observed. To recover the diagnosis performance degradations, additive logics were applied to minimize the diagnosis failures that were not observed in the previous validations of the separate models. The results of a case study were then analyzed in terms of the real-time diagnosis outputs that plant operators would actually face in an emergency situation.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.174-176
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• 2007

Because of accident or leak of electricity, high voltage electricity can be conducted to vehicle chassis and damage human. Therefore the unit for detecting ground fault is necessary to minimize loss of life or equipment damage. Isolation resistance must be monitored for detecting ground fault. GFD(Ground Fault Detection) unit continually generate the pulse voltage between high voltage network and chassis. This will be sensing the returned current, calculate the isolation resistance and make decision the ground fault. This paper describes the method detecting ground fault.

• Journal of the Korean Society of Safety
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• v.32 no.2
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• pp.59-65
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• 2017

Calculation of the damage impact of chemical accidents is an important element in site, and the initial isolation distance and the protective action distances are significant factors in coping the chemical accident. In this study, three major cities that represent each Province were selected, and the safety distances were calculated considering regional climate conditions. The results were compared with the prescribed values in Emergency Response Guidebook. It is concluded that the regional meteorological conditions such as temperature, vapour pressure, relative humidity, wind speed, and cloud cover should be reflected in estimating the initial isolation distance and the protective action distance.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.7 no.3
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• pp.30-39
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• 2011

URANUS (Ubiquitous, Robust, Accident-forgiving, Non-proliferating, Ultra-lasting and Sustainer) has been developed with 35MWe (100MWth) operating without primary coolant pump, capitalizing on natural circulation capability of lead-bismuth eutectic (LBE) for long-life small and robust power units. To ensure the structural integrity, the large safety margin against Safe Shutdown Earthquake, 0.3g, and furthermore the cost effectiveness for URANUS, three-dimensional seismic base isolation design has been developed. The analytical model has been developed and seismic time history analyses have been carried out. The advantage for using three-dimensional seismic base isolation for URANUS has been discussed.

• Nuclear Engineering and Technology
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• v.15 no.4
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• pp.219-228
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• 1983

The blowdown history of the TMI-2 accident up to the isolation of the relief valve associated with a small break LOCA is reviewed briefly. An analysis is made to determine what instruments should be added in the core in order to prevent core damage in the case of the TMI-2 accident. With the added instruments a procedure is presented on how to predict the uncovered level of the core and how to calculate operator time margin. Sample calculations are done for the TMI-2 accident to determine the uncovered level and operator time margin. Finally, the map to show the uncovered level of the core and operator time margin is drawn with measurable parameters by the above methods.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.26 no.6
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• pp.415-421
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• 2013

In order to extend the service life of a nuclear power plant(NPP) ensuring the structural safety, effective and efficient management of NPP considering structural deteriorations and various natural hazard risks has been treated as a significant tool(IAEA 1998). The systemic efforts is required to prevent the potential loss of NPPs resulting from the natural hazard including earthquakes, hurricane and flooding since the Fukushima accident. Earthquake risk of building structures can be mitigated through appropriate seismic isolation system installation. It has been known that a seismic isolation system can lead to reduction of the deleterious effect on ground motion induced by earthquakes, and structural safety can be improved. In this paper, the NPP life-cycle management is reviewed. Furthermore, effect of seismic isolation on the NPP life-cycle cost analysis with earthquake, and cost-benefit analysis in terms of life-cycle cost when applying the seismic isolation systems to NPP are introduced.

• Nuclear Engineering and Technology
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• v.31 no.6
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• pp.66-82
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• 1999

The national long-term R&D program, updated in 1997, requires Korea Atomic Energy Research Institute(KAERI) to complete by the year 2006 the basic design of Korea Advanced Liquid Metal Reactor(KALIMER), along with supporting R&D work, with the capability of resolving the issue of spent fuel storage as well as with significantly enhanced safety. KALIMER is a 150 MWe pool-type sodium cooled prototype reactor that uses metallic fuel. The conceptual design is currently under way to establish a self-consistent design meeting a set of major safety design requirements for accident prevention. Some of the current emphasis includes those for inherent and passive means of negative reactivity insertion and decay heat removal, high shutdown reliability, prevention of and protection from sodium chemical reaction, and high seismic margin, among others. All of these requirements affect the reactor design significantly and involve extensive supporting R&D programs. This paper summarizes some of the results of conceptual engineering and design analyses performed for the safety of HAMMER in the area of inherent safety, passive decay heat removal, sodium water reaction, and seismic isolation.

• Journal of the Earthquake Engineering Society of Korea
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• v.19 no.1
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• pp.21-28
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• 2015

The nuclear accident due to the recent earthquake in Japan has triggered awareness of the importance of safety with regard to nuclear power plants (NPPs). An earthquake is one of the most important parameters which governs the safety of NPPs among external events. Application of a base isolation system for NPPs can reduce the risk for earthquakes. At present, a soil-structure interaction (SSI) analysis is essential in the seismic design of NPPs in consideration of the ground structure interaction. In the seismic analysis of the base-isolated NPP, it is restrictive to consider the nonlinear properties of seismic isolation devices due to the linear analysis of the SSI analysis programs, such as SASSI. Thus, in this study, SSI analyses are performed using an iterative approach considering the material nonlinearity of the isolators. By performing the SSI analysis using an iterative approach, the nonlinear properties of isolators can be considered. The difference between the SSI analysis results without iteration and SSI with iteration using SASSI is noticeable. The results of the SSI analysis using an effective linear (non-iterative) approach underestimate the spectral acceleration because the effective linear model cannot consider the nonlinear properties of isolators. The results of the SSI analysis show that the horizontal response of the base-isolated NPP is significantly reduced.