• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.10
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• pp.1274-1284
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• 1999

The Regulatory Guide 1.82 recommends an analysis of hydraulic performance for sump of ECCS (Emergency Core Cooing System) when LOCA(Loss of Coolant Accident) occurs in a nuclear power plant. The present study deals with 3-dimensional, unsteady, turbulent and two-phase flow simulation to examine the behavior of mixture of reactor coolant and debris near the floor of containment building in conjunction with appropriate assumptions. The dispersed solid model has been adjusted to the interfacial momentum transfer between reactor coolant and debris. According to the results, the counterclockwiserecirculation zone had been formed in the region between sump and connection aisle about 376 second after LOCA occurs. The debris thickness accumulated on a sump screen periodically increases or decreases up to 2000 second, afterwards its peak decreases.

• Nuclear Engineering and Technology
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• v.38 no.2
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• pp.195-200
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• 2006

In order to confirm the integrity of IRWST following a severe accident, the hydrogen behavior inside and around the IRWST has been investigated for an SBO accident. A detailed containment model, including 18 control volumes for IRWST, has been developed. Analysis results show that the peak hydrogen concentration is about 57% during the core melting period. The combustion regime shows that flame acceleration and DDT are possible in the IRWST. The flame acceleration criterion is met when the peak hydrogen concentration occurs; the 7 -DDT criterion is also met during some periods. These results show certain measures may be required to assure IRWST integrity against an SBO accident.

• Journal of the Korean Society of Safety
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• v.26 no.5
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• pp.73-80
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• 2011

There are insufficient models that find problems and solutions for accident prevention through risk assessment and suggest safe work process and work instruction from foundation works to finish work for accident decrease. This paper presents a quantitative risk assessment model by analysis of risk factors in each process such as foundation, erection, pier, pier upper and etc based on accident examples and investigation on actual condition in bridges construction work. In addition, the safety management system was developed to perform risk assessment of construction and use it for effective safety training for labor.

• Journal of the Korea Safety Management & Science
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• v.14 no.4
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• pp.23-29
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• 2012

There are insufficient models that find problems and solutions for accident prevention through risk assessment and suggest safe work process and work instruction from foundation works to finish work for accident decrease. This paper presents a quantitative risk assessment model by analysis of risk factors in each process such as appurtenant works, temporary works, structural works, equipment work, finishing work and etc based on accident examples and investigation on actual condition in plants construction work. In addition, the safety management system was developed to perform risk assessment of plants construction and use it for effective safety training for labor.

• Journal of Auto-vehicle Safety Association
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• v.13 no.4
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• pp.114-122
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• 2021

In this paper, an automated vehicle intersection collision accident was analyzed through simulation. Recently, the more automated vehicles are distributed, the more accidents related to automated vehicles occur. Accidents may show different trends depending on the sensor characteristics of the automated vehicle and the performance of the accident prevention system. Based on NASS-CDS (National Automotive Sampling System-Crashworthiness Data System) and TAAS (Traffic Accident Analysis System), four scenarios are derived and simulations are performed. Automated vehicles are applied with a virtual system consisting of an autonomous emergency braking system and algorithms that predict the route and avoid collisions. The simulations are conducted by changing the sensor angle, vehicle speed, the range of the sensor and vehicle speed range. A range of variables considered vehicle collision were derived from the simulation.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.21 no.2
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• pp.152-166
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• 2022

This study analyzed the causal relationship among operating characteristics of commercial freight vehicles, dangerous driving behaviors, and traffic accident risk. The study applied the existing accident cause and prevention theory to arrive at this relationship. Data related to working characteristics of driver, driving experience, driving ability, driving psychology, vehicle characteristics (size), dangerous driving behavior, and traffic accidents were collected from 303 commercial freight vehicle drivers. Working characteristics and dangerous driving behavior data are based on the driver's digital driving record. The traffic accident data is based on the insurance accident data reflecting actual traffic accidents. First, a structural equation model was built and verified using the model fitness index. Then, the developed model was used to analyze the causal relationship between multiple independent and dependent variables simultaneously. Four dangerous driving behaviors (sudden deceleration, sudden acceleration, sudden passing, and sudden stop) were found to be highly related to traffic accidents. The results further indicate that it is necessary to establish a safety management policy and intensive management for small-sized freight vehicles, drivers with insufficient driving ability, and drivers with dangerous driving behaviors. Such policy and management are expected to reduce traffic accidents effectively.

• Journal of the Korean Society of Safety
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• v.27 no.2
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• pp.111-116
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• 2012

This study deals with the traffic accidents of circular intersections in Korea. The purposes are to comparatively analyze the characteristics by operational type, and to develop the models using the data of 82 intersections. In pursuing the above, this study gives particular emphasis to modeling such the accidents as the roundabout and rotary in urban area. The main results analyzed are as follows. First, the null hypotheses that the number of accidents are the same in both the urban and rural intersections, and roundabout and rotary in urban area, were analyzed to be rejected. Second, 3 accident models were developed, which were all statistically significant. The independent variables used in the above models are the ADT, number of approach lane, bus stop, parking facilities, and others. This study could be expected to give some implications to the traffic safety policy decision-making.

• Nuclear Engineering and Technology
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• v.49 no.2
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• pp.434-441
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• 2017

Containment venting is one of several essential measures to protect the integrity of the final barrier of a nuclear reactor during severe accidents, by which the uncontrollable release of fission products can be avoided. The authors seek to develop an optimization approach to venting operations, from a simulation-based perspective, using an integrated severe accident code, THALES2/KICHE. The effectiveness of the containment-venting strategies needs to be verified via numerical simulations based on various settings of the venting conditions. The number of iterations, however, needs to be controlled to avoid cumbersome computational burden of integrated codes. Bayesian optimization is an efficient global optimization approach. By using a Gaussian process regression, a surrogate model of the "black-box" code is constructed. It can be updated simultaneously whenever new simulation results are acquired. With predictions via the surrogate model, upcoming locations of the most probable optimum can be revealed. The sampling procedure is adaptive. Compared with the case of pure random searches, the number of code queries is largely reduced for the optimum finding. One typical severe accident scenario of a boiling water reactor is chosen as an example. The research demonstrates the applicability of the Bayesian optimization approach to the design and establishment of containment-venting strategies during severe accidents.

• Proceedings of the Safety Management and Science Conference
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• 1999.11a
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• pp.53-72
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• 1999

IPQC system was introduced for the flight safety at the age of scientific safety management in the 1980s. In spite of performing this system, aircraft accidents caused by human factors, which were above 70% among all flight accident factors, have not been reduced. Accordingly, throughout this paper I analyzed the aircraft accident factors by means of a literature study and a pilot survey. Then, based on the notion of TQC(Total Quality Control), I hierarchically classified Individual Quality into Capacity Management, Safety Management, and General Management and did the low-ranked management factors as well. AHP (Analytic Hierarchy Process), one of the scientific management methods, was used for estimating the relative importance of Individual Quality Control factors and the heavy aircraft accident causes over the last 20 years were analyzed according to the flight ranks. Based on the comparative analysis of results derived above, an IPQC model as flight ranks is established. In short, according to this newly suggested model we can obtain the maximum flight safety with the preventive actions against aircraft accidents caused by human factors and by improving the operation effect under the reasonable pilot management.

• Journal of Korea Society of Industrial Information Systems
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• v.7 no.4
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• pp.46-52
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• 2002

Due to the administrative expand and the paradigm shift in global environments, the range for the enterprises assessment are now expanding to inclusive administration assessment including all kinds of accidents in work places as well as products and services. Therefore continuous investment and concern to safety and health are needed since some faults in safety and health lead to the enormous expense as well as decline of brand image. In this paper, n are concerned with the safety administration in industrial field and analyze the accident data, before and after the establishment of specialized organization for accident prevention, using the reliability growth model of Duane. The validity of the model is verified under the assumptions of NHPP(non-homegeneous Poisson process) of the accidents.