• The KSFM Journal of Fluid Machinery
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• v.17 no.6
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• pp.84-88
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• 2014

A long term passive cooling system is considered as the most important safety feature for the nuclear design after the Fukushima Daiichi nuclear power plant accident in 2011. The conventional active pump driven safety systems are not available during a station Black Out (SBO) accident. The current design requirement on cooling time of the Passive Auxiliarly Feedwater System (PAFS) is about 8 hours only. To meet the 72 hours cooling time, the pool capacity of cooling water tank should be increased as much as 3~4 times larger than that of current water cooling tank. In order to extend the cooling time for 72 hours, a new passive air-water combined cooling system is proposed. This paper provides the feasibility of the combined passive air-water cooling system. The current pool capacity of water cooling system is preserved, and the cooling capability is extended by an additional air cooler.

• Nuclear Engineering and Technology
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• v.55 no.7
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• pp.2504-2515
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• 2023

In past years the Paul Scherrer Institute (PSI, Switzerland) and the Karlsruhe Institue of Technology (KIT, Germany)) collaborated to develop a model to account for the active role of nitrogen in the air oxidation of a Zircalloy cladding. The "PSI-KIT Nitriding Model for Zirconium based Fuel Cladding" model was implemented at PSI into PSI-MELCOR 1.8.6. In order to make a preliminary evaluation of the effect of the new model on the evolution of full-scale spent fuel pool accidents, one spent fuel pool event was analyzed using the PSI research version of PSI-MELCOR 1.8.6, which includes the nitriding model. To adapt an existing input deck for the calculations, a sensitivity study was conducted to find an optimal nodalization for the analyses. The nitriding model results were compared to those calculated with the MELCOR 1.8.6-PSI without the new nitriding model. The results demonstrate the effect of the nitriding reactions in spent fuel pool accident progression. Moreover, they confirm the impact of ZrN formation during cladding oxidation in air when the oxidation reactions lead to oxygen starvation inside the fuel assemblies. The nitriding reaction led to higher chemical heat generation during the accident and to an earlier failure of the cladding than when the effect of nitrogen reactions was not considered. It should be noted that the nitriding model, as implemented in the PSI version of MELCOR 1.8.6 has not yet been conclusively validated. Thereby the results presented in this paper should be treated as a preliminary demonstration of the capabilities of the model.

• Journal of the Korea Safety Management & Science
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• v.7 no.1
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• pp.45-56
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• 2005

The air bridge that connects an airplane with air terminal is important facilities that help people get in and out an airplane safely and conveniently. As the number of people who takes airplane has been increasing, an unexpected accident or a disorder on an air bridge can lead to the loss of passenger's lives or a great damage of airplane. This paper suggests a method to secure the safety of an air bridge.

• The Korean Journal of Air & Space Law and Policy
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• v.19 no.2
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• pp.137-162
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• 2004

Generally the aircraft accident caused a great loss of lives, severe property damages including aircraft's total loss and thus, affect enormous emotional and economic damages to the public. We, therefore, should try every efforts to prevent the re-occurrence of aircraft accident by examining the cause of accident closely and discovering it through aircraft accident investigation. Though the object of an accident investigation is not to apportion blame but to discover a cause or causes of an accident to prevent future accidents, the cause of an accident would play a vital role in determining the liability of the carrier, legal relationship with the third party and jurisdiction, etc. in the aviation litigation. Therefore, it is very important that aircraft accident investigation are carried out by a professional and independent agency. Also, it needs for us to be careful in applying investigation results in the courts not to be deterrent to discovering the cause of accident. Korea now has the Aviation Accident Investigation Agency Board under the Korean Ministry of Construction and Transportation, but unfortunately it is often pointed out that it lacks professionalism and independency due to the bureaucratism of the Government. We, therefore, should establish a professional and independent aircraft accident investigation agency like United States' NTSB and reflect the issues mentioned-above on the new Act.

• Journal of Auto-vehicle Safety Association
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• v.6 no.1
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• pp.22-26
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• 2014

Fatality of accidents on curved roads where rollover accidents are likely to take place was higher than that on straight roads. We ought to investigate factors affecting injury severity of occupant in a vehicle rollover accident. From January 2011 to December 2013, we collected data about rollover motor vehicle crash accident. We surveyed occupant's injury, vehicle type, safety devices, type of rollover accident and the number of turn in accident. Of the 132 subjects, 56.1% were males, 50.8% were drivers, 48.5% fastened seat belt, and air bag deployed in 12.1%. Among injuries sustained head, chest and abdomen were major sites of severe injury(Abbreviated injury scale>2). Seat belt use, rollover type, and the number of 1/4 turn were found to have significant positive correlations with Injury Severity Score. The regression analysis herein found significance in safety belt use and the number of 1/4 turn. Seat belt use was a significant factor affecting injury severe of occupant in rollover accident.

• Journal of Radiation Protection and Research
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• v.44 no.4
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• pp.128-148
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• 2019

Massive environmental monitoring has been conducted continuously since the Fukushima Daiichi Nuclear Power accident in March of 2011 by different monitoring methods that have different features together with migration studies of radiocesium in diverse environments. These results have clarified the characteristics of radiological environments and their temporal change around the Fukushima site. At three months after the accident, multiple radionuclides including radiostrontium and plutonium were detected in many locations; and it was confirmed that radiocesium was most important from the viewpoint of long-term exposure. Radiation levels around the Fukushima site have decreased greatly over time. The decreasing trend was found to change variously according to local conditions. The air dose rates in environments related to human living have decreased faster than expected from radioactive decay by a factor of 2-3 on average; those in pure forest have decreased more closely to physical decay. The main causes of air dose rate reduction were judged to be radioactive decay, movement of radiocesium in vertical and horizontal directions, and decontamination. Land-use categories and human activities have significantly affected the reduction tendency. Difference in the air dose rate reduction trends can be explained qualitatively according to the knowledge obtained in radiocesium migration studies; whereas, the quantitative explanation for individual sites is an important future challenge. The ecological half-lives of air dose rates have been evaluated by several researchers, and a short-term half-life within 1 year was commonly observed in the studies. An empirical model for predicting air dose rate distribution was developed based on statistical analysis of an extensive car-borne survey dataset, which enabled the prediction with confidence intervals. Different types of contamination maps were integrated to better quantify the spatial data. The obtained data were used for extended studies such as for identifying the main reactor that caused the contamination of arbitrary regions and developing standard procedures for environmental measurement and sampling. Annual external exposure doses for residents who intended to return to their homes were estimated as within a few millisieverts. Different forms of environmental data and knowledge have been provided for wide spectrum of people. Diverse aspects of lessons learned from the Fukushima accident, including practical ones, must be passed on to future generations.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.15 no.1
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• pp.18-25
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• 2007

The safety should be primarily considered for air vehicle, such as helicopter, which is not easy to cope with when out of order or loss of control that followed catastrophe. The U.S National Transportation Safety Board (NTSB) investigated and analyzed for 34 years rotorcraft accidents that occurred from 1963 through 1997. This paper handles intensively the relative investigation and analysis of recent 10 years domestic civil helicopter accidents to those of the United States in order to increase the safety of helicopter transportation and to consider the main design parameter before we develop Korean Civil Helicopter. To understand the overview of civil turbine helicopter accident, it uses the NTSB's accident investigation results and the overall accident trend for U.S civil single and twin turbine engine helicopter according to category, cause, activity, and phase of operation.

• Journal of Auto-vehicle Safety Association
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• v.10 no.2
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• pp.13-19
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• 2018

The purpose of this study was to evaluate the effect of air bag deployment in passenger car head-on collisions on injuries to the driver. The drivers in head-on collisions who were brought to the emergency rooms of two hospitals from January 2011 and October 2014 were evaluated, as were the vehicles involved. The driver injury level were assessed by utilizing Collision Deformation Classification (CDC) codes, and the Abbreviated Injury Scale (AIS) and Injury Severity Score (ISS), respectively. In this study, it was shown that the chest ISS and AIS were significantly high when an air bag only is deployed. A statistically significant difference was found in the crush extent when the driver who fastened the seatbelt was found to be affected more than the ISS 9. Even when an air bag is deployed in a head-on car collision, injury severity can vary according to accident circumstances and crash severity. Accordingly, first aid can be rapidly given, and the injured person can be quickly referred to a hospital, only if the assessment of persons involved in a vehicle accident is accurately carried out.

• Nuclear Engineering and Technology
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• v.46 no.6
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• pp.817-824
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• 2014

To ensure the safety of research reactors, the water level must be maintained above the required height. When a pipe ruptures, the siphon phenomenon causes continuous loss of coolant until the hydraulic head is removed. To protect the reactor core from this kind of accident, a siphon breaker has been suggested as a passive safety device. This study mainly focused on two variables: the size of the pipe rupture and the timing of air entrainment. In this study, the size of the pipe rupture was increased to the guillotine break case. There was a region in which a larger pipe rupture did not need a larger siphon breaker, and the water flow rate was related to the size of the pipe rupture and affected the residual water quantity. The timing of air entrainment was predicted to influence residual water level. However, the residual water level was not affected by the timing of air entrainment. The experimental cases, which showed the characteristic of partical sweep-out mode in the separation of siphon breaking phenomenon [2], showed almost same trend of physical properties.

• Journal of Environmental Health Sciences
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• v.39 no.4
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• pp.346-353
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• 2013

Objectives: The goal of this study is to identify the distribution of the foliar fluorine content of vegetation surrounding the area where hydrofluoric acid was accidently released in Gumi, Gyeongsangbuk-do on September 27, 2012. In addition, it also aims to estimate the concentration of hydrogen fluoride in the air on the day of the accident. Methods: Samples of plant leaves were collected on October 7, 2012 within 1 km from the site where the accident occurred. These samples were analyzed for soluble fluorine ion with an ion selective electrode. The ambient concentration of hydrogen fluoride was calculated using the fluoride content in the plant via the dose-rate equation (${\Delta}F$=KCT). Results: The arithmetic and geometric means of the concentrations were 2158.2 and 1183.7mg F $kg^{-1}$ for leaves and, 2.4 and 1.1 ppm HF for the air, respectively. The highest concentration of hydrogen fluoride in the air was 14.7 ppm, which is higher than the maximum concentration reported by the government (1 ppm) and the exposure limit (ceiling, 3 ppm). The concentrations of both fluorine and hydrogen fluoride decreased with increasing distance from the accident site and showed a significant decrease outside of a 500m radius from the site (p <0.05). Conclusions: The area around the accident site was highly polluted with hydrogen fluoride according to the results of this study. Considering the persistency of hydrogen fluoride in the environment, long-term monitoring and environmental impact assessment should be pursued.