• Nuclear Engineering and Technology
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• v.56 no.10
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• pp.4068-4076
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• 2024

In the event of severe accidents in pressurized water reactor (PWR) nuclear power plants, the potential leakage of radioactive aerosols through containment cracks poses a considerable radioactive hazard to the public. Understanding aerosol transport and retention in cracks helps reduce the conservatism and uncertainty of radioactive hazard assessment. Concrete cracks are recognized as a pivotal pathway for the leakage of radioactive aerosols, and several researchers have undertaken experimental investigations concerning the aerosol transport and retention in concrete cracks. However, the majority of these studies have rather low gas flow Reynolds numbers. In this work, an experimental setup is built to study aerosol transport and retention in concrete cracks under high Reynolds number flow. The TiO₂ aerosol with a mass median diameter of 1 ㎛ and two concrete crack specimens are used in experiments. The results of gas flow experiments indicate that the Reynolds number is capable of reaching 10547. Combining the flow experimental data and Suzuki's formula, the equivalent heights of these two crack specimens are approximated as 303.67 ㎛ and 231.48 ㎛. The experimental results indicate a notably high retention rate of aerosols, exceeding 0.8. Furthermore, under high Reynolds number flow, the retention rate varies over a relatively narrow range, with the larger the equivalent height of the crack resulting in a lower retention rate. The experimental results match well with the mechanistic analysis based on inertial deposition theory, demonstrating the rationality of the inertial deposition theory.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.2
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• pp.747-754
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• 2012

The purpose of this study was to compare inter-regional accident modes using the National Hospital Discharge Patient Injury Survey. In order to determine economic status of each region, 234 cities and counties were categorized as 5 groups according to their financial self-reliance ratio. The main results are as follows. First, transport accidents had increased by the age group of 25 to 44 but decreased thereafter. Second, the frequency of car accidents was the highest among several types of transport accidents. Most common site of transport accidents was roads and highways. Third, there was significant difference in the modes of transport accident among regions. Fourth, emergency admission rate was quite different according to regional groups but it was no significant difference by economic status. Lastly, there was significant difference in injury patterns by region groups. In regions which were high economic status, there were relatively less serious injury patterns such as sprain, strain, dislocation while regions which were in low economic status had experienced serious injury including fracture, stab wound, and open fracture. We could find the difference in accident modes by regional economic status. Therefore, health authority should consider different accident prevention strategies by regional groups.

• The Korean Journal of Air & Space Law and Policy
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• v.25 no.2
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• pp.113-137
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• 2010

The international community has done a lot of effort to improve the aviation safety. The new high technologies, systems and development of navigation equipments considerably improved the level of aviation safety. However, the aviation accident rate has been showing unchanged status without the decline since 1980. It means it is difficult to secure enough safety by the existing efforts to improve the aviation safety, eventually needs new methods for the accident prevention. With this in mind, the nations interest new methods that can consider a countermeasure by realizing potential risk factors before fatal accidents. In other words, that is to analyze and share the safety information collected from accidents by establishing aviation safety information system. To establish international aviation safety information system, each country's aviation accident incident reporting systems are need to be established. Also aviation safety data taxonomy is need to be standardized. Then, aviation users will communicate the information efficiently. This study investigates and considers each country's aviation accident incident database taxonomy for the analysis of the aviation data and the necessary prevention activity. This will contribute to a better international aviation safety and strengthen the country's aviation diplomacy.

• Journal of Digital Convergence
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• v.10 no.8
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• pp.179-184
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• 2012

A car accident on a highway occurs a chain-reaction collision because of a vehicle's fast velocity. In order to prevent it, the accident vehicle should broadcast a safe message to its neighbors. If there are many neighbor nodes, a frame collision probability is high. To solve this, it was proposed for a system as a previous study to send a safe message without frame-collision using separating channels. However, the separation of multiple channels make feasibility low because of increasing hardware's development cost and complexity. In this paper, we proposes a TDMA-based MAC protocol using a single channel. As a result, we show the frame reception success rate of our protocol was almost the same as the previous protocol.

• The Journal of Korean Society for School & Community Health Education
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• v.8 no.2
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• pp.1-18
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• 2007

Background: The study investigated the causes of safety accidents by facility, focused on safety accidents caused directly or indirectly by school facilities at elementary schools in S City. Purpose: The objective of this study is to provide materials for planning the construction of school buildings and the installation of school facilities and for improving existing facilities and ultimately to minimize mental and Physical losses from safety accidents caused by school facilities and to create pleasant education environment. Method: We selected 10 elementary schools in S City, analyzed the factors of safety accidents caused by facilities inside and outside the schools, and presented the results of the analysis including the factors of safety accidents caused by elementary school facilities. Result: It was found that safety accidents caused by elementary school facilities can be prevented to some degree by considering safety accidents in facility planning. As the safety accident rate is higher at elementary schools than at middle and high schools, it is essential to consider safety accidents in planning the construction of an elementary school and to execute safety accident prevention education in order to reduce safety accidents at elementary schools. In addition, as the curriculums are revised and new facilities are introduced for the new curriculums, elementary students' physical, psychological and environmental factors should be analyzed and studied closely and the results should be reflected in establishing the standards for the installation of elementary school facilities.

• Journal of the Korea Safety Management & Science
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• v.18 no.1
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• pp.75-82
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• 2016

According to the statistics, occupational fatal injuries by the fork lifts were about 30 per year in whole industrial. Fork lifts are widely used in various parts of industries to improve the efficiency of the work. In this study, the current regulations to be adequate in industrial site have to be renew in order to prevent the fatal injuries by the fork lifts. Fatal injury analysis were conducted with several accident cases by the fork lifts. For each accident, the causes of the injuries were examined and proper safety measures were proposed. In this study, the fork lift showed a high fatality rate in industrial accidents and no detailed cause analysis of fatal accidents was conducted in terms of unsafe acts or conditions. First, fork lifts were the highest of the machines caused the accidents. In order to prevent fatal injuries by the fork lifts, the tarket was manufacturing industry. Second, the order of the cause of cognitive engineering agenda in the manufacture industrial was visibility, responsibility and affordance, and revision of acts was proposed. Third, there was not a lots of different points of human error between occurrence types and business sizes. Forth, number of fatalities by the attacker was more than by the inducer.

• Nuclear Engineering and Technology
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• v.31 no.1
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• pp.17-28
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• 1999

A thermal-hydraulic analysis is conducted on the loss-of-coolant-accident (LOCA) during shutdown operation of YGN Units 3/4. Based on the review of plant-specific characteristics of YGN Units 3/4 in design and operation, a set of analysis cases is determined, and predicted by the RELAP5/MOD3.2 code during LOCA in the hot-standby mode. The evaluated thermal-hydraulic phenomena are blowdown, break flow, inventory distribution, natural circulation, and core thermal response. The difference in thermal-hydraulic behavior of LOCA at shutolown condition from that of LOCA at full power is identified as depressurization rate, the delay in peak natural circulation timing and the loop seal clearing (LSC) timing. In addition, the effect of high pressure safety injection (HPSI) on plant response is also evaluated. The break spectrum analysis shows that the critical break size can be between 1% to 2% of cold leg area, and that the available operator action time for the Sl actuation and the margin in the peak clad temperature (PCT) could be reduced when considering uncertainties of the present RELAP5 calculation.

• Journal of Korean Society for Geospatial Information Science
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• v.10 no.1 s.19
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• pp.67-76
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• 2002

At a recent, with an increase of traffic demand and a spread of automobile culture, the safety, convenience and speed of highway is required. On this study, using the real time kinematic GPS, observation value at a center line of ready-built road is obtained and then design specification of highway, IP, IA and R are obtained by least square method. Using those IP, IA and R, we analysed the risk factor of highway alignment by the standard for structure and facility of the road. With using RTK GPS, we could analyse dangerous element of highway alignment rapidly and cope with dangerous area of the existing road. It is also proved to apply availably whether we determine alignment improvement is needed or not or analyze source of accident related with alignment in the region having a high traffic accident rate.

• Nuclear Engineering and Technology
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• v.28 no.3
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• pp.290-298
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• 1996

Direct Containment Heating, DCH, is supposed to occur during a core melt-down accident if the primary system pressure is still high at the time of vessel breach in a Nuclear Power Plant (NPP). In this case, DCH is considered to be one of very important severe phenomena during postulated severe accident scenario because of the fast heat transfer rate to atmosphere and the sharp pressure increase in a containment. To reduce the effect of this DCH phenomena, the capture volume wes designed at Ulchin NPP units 3 and 4. But, the effect of this has not been studied extensively. This work consists of experimental and numerical analyses of the effects of capture volume in the cavity on DCH phenomena. The experimental model is a 1/30 scaled-down model of Ulchin NPP units 3 and 4. We used three types of capture volumes to investigate the effect of size. Numerical analysis using CONTAIN 1.2 is performed with the correlation for the dispersed fraction of molten corium from the cavity into the containment derived from the experimental data to examine the effect of capture volume on DCH phenomena in full scale of Ulchin NPP units 3 and 4.

• Nuclear Engineering and Technology
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• v.47 no.7
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• pp.907-914
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• 2015

The energetic steam explosion caused by contact between the high temperature molten core and water is one of the phenomena that may threaten the integrity of the containment vessel during severe accidents of light water reactors (LWRs). We examined the dependence of steam explosion loads in a typical reactor cavity geometry on selected model parameters and initial/boundary conditions by using a steam explosion simulation code, JASMINE, developed at Japan Atomic Energy Agency (JAEA). Among the parameters, we put an emphasis on the water pool depth that has significance in terms of accident mitigation strategies including cavity flooding. The results showed a strong correlation between the load and the premixed mass, defined as the mass of the molten material in low void zones (void fraction < 0.75). The jet diameter and velocity that comprise the flow rate were the primary factors to determine the premixed mass and the load. The water pool depth also showed a significant impact. The energy conversion ratio based on the enthalpy in the premixed mass was in a narrow range ~4%. Based on this observation, we proposed a simplified method for evaluation of the steam explosion load. The results showed fair agreement with JASMINE.