• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• 제9권2호
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• pp.73-80
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• 2011

The radiation shielding analysis for a Burnup-credit (BUC) cask designed under the management of Korea Radioactive Waste Management Corporation (KRMC) was performed to examine the contribution of each radiation source affecting dose rate distribution around the cask. Various radiation sources, which contain neutron and gamma-ray sources placed in active fuel region and the activation source, and imaginary nuclear fuel were all considered in the MCNP calculation model to realistically simulate the actual situations. It was found that the maximum external and surface dose rates of the spent fuel cask were satisfied with the domestic standards both in normal and accident conditions. In normal condition, the radiation dose rate distribution around the cask was mainly influenced by activation source ($^{60}Co$ radioisotope); in another case, the neutron emitted in active fuel region contributed about 90% to external dose rate at 1m distance from side surface of the cask. Besides, the contribution level of activation source was dramatically increased to the dose rates in top and bottom regions of the cask. From this study, it was recognized that the detailed investigation on the radiation sources should be performed conservatively and accurately in the process of radiation shielding analysis for a BUC cask.

• Proceedings of the Korea Water Resources Association Conference
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• 한국수자원학회 2018년도 학술발표회
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• pp.71-71
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• 2018

Sea pollution accidents have been occurred due to the increase of marine ship traffic. Oil spill from the hull hole induced by tanker collision results in the huge sea pollution. Proper and prompt reaction on such oil spill disaster is needed to minimize the damage. Thru-hull emergency wood plug is typically used to manually close small holes, while it is required to develop some mechanical devices for closing large holes in the hull due to huge fluid pressure. Accurate estimation of oil discharge and velocity from such holes are important to develop proper device to control hull hole damage. High resolution CFD modeling investigation on the configurations of hull hole of 7.5 m initial depth and 30 cm diameter, which was observed in the oil spill accident of the Hebei Sprit off the west coast of Korea in 2007, has been carried out to compute the oil spill velocity distribution in terms of flow depth. Friction loss due to the viscous flow and the discharge coefficient of crude oil with specific gravity SG = 0.85 and viscosity of $4-12cP(mPa{\cdot}s)$ at the temperature of $20^{\circ}C-100^{\circ}C$ are presented in terms of Reynolds number based on the results of high-resolution CFD modeling.

• Nuclear Engineering and Technology
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• 제18권4호
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• pp.273-280
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• 1986

The purpose of this study is to obtain the experimental data of the forced flow dryout heat flux in a heat generating debris bed which simulates the degraded nuclear reactor core after severe accident. An experimental investigation has been conducted of dryout heat flux in an inductively heated bed of steel particles with upward forced flow rising coolant circulation system under atmospheric pressure. The present observations were mainly focused on the effects of coolant mass flux, particle size, bed height, and coolant subcooling on the dryout heat flux The data were obtained when carbon steel particles in the size distribution 1.5, 2.5, 3.0 and 4.0 mm were placed in a 55 mm ID Pyrex glass column and inductively heated by passing radio frequency current through a multiturn work coil encircling the column. Distilled water was supplied with variation of mass flux from 0 to 3.5 kg/$\textrm{cm}^2$ s as a coolant in the tests, while the bed height was selected as 55 mm and 110 mm. Inlet temperature of coolant varied by 2$0^{\circ}C$ and 8$0^{\circ}C$. The principal results of the tests are: (1) Dryout heat flux increases with increase of upward forcing mass flux and particle size; (2) The dryout heat flux at the zero mass flux obviously depends on the Particle size as Previous studies; (3) The forced flow dryout heat flux in the shallow bed is somewhat higher than that in the deep bed,

• Fire Science and Engineering
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• 제32권6호
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• pp.1-6
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• 2018

This study is to analyze the characteristics of the yellow insulation ring type of the CSST used for tubing when it is artificially deteriorated and damaged by burning. The CSST for tubing consists of a tube, protective coating, nut, yellow insulation ring, packing, and socket. In addition, it is thought that a yellow insulation ring and rubber packing were used to connect the tube and socket in order to improve the airtightness and insulation performance. The result of the verification of the data acquired from the tests in the 95% confidence interval shows that the Anderson-Darling (AD) and P value were analyzed to be 0.945 and 0.015, respectively. This confirms that the test data of the CSST for tubing is reliable. The analysis of the arithmetic mean of the insulation resistance of a CSST showed that the CSST damaged by burning by a torch, and the one damaged by electrical burning, was $16.7k{\Omega}$ (the greatest relatively) and $208{\Omega}$ (the lowest), respectively, while it was $1.72k{\Omega}$ in the case of a normal product. Therefore, the analysis result of the insulation resistance of the CSST collected from the scene of a fire can be utilized to examine the cause of damage by burning. In addition, it was found that when the maximum current of 97 A was applied to the CSST for about 5 s using a Primary Current Injection Test System (PCITS) the protective film and insulation ring of the CSST has no difference from that of a normal product. However, a part of the metal tube was melted.

• Journal of the Korea Academia-Industrial cooperation Society
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• 제19권12호
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• pp.227-236
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• 2018

This study was conducted to define hippocampal volume differences between a stress-laid group and normal individual group via meta-analysis. This investigation included studies that contained hippocampal volume measurements in association with stress from 1990 to 2016. Magnetic resonance imaging (MRI) measurements of hippocampal volumes were used to determine the mean size, standard deviation and sample size. The pooled effect size was measured by the standardized mean difference (SMD) with a 95% confidence interval. This meta-analysis included 13 studies comprising 374 stress subjects and 439 normal subjects. Eight studies targeted war-related veterans and holocaust survivors, while five targeted personal trauma associated with childhood abuse, rape, accident or financial hardship. The overall mean effect size (Hedges' g) was -0.70 (-1.04; -0.37). Overall, the SMD value was -0.70, with a moderate effect size, but high heterogeneity. Depending on the characteristics of the stressor, studies were divided by subgroups of war-related veterans and subjects with personal trauma and then analyzed again. In the war-related subgroup, the Hedges' g was -0.47 (-0.78; -0.16), while in the personal stressor-related subgroup it was -0.91 (-1.57; -0.26). These results indicate that there was a significant negative correlation between psychological stress and hippocampal volume.

• Journal of the Architectural Institute of Korea Planning & Design
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• 제35권1호
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• pp.73-81
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• 2019

The purpose of this study is to draw safe environmental project factors for enhancing the safety of children in peripheral space around children's park and suggest environmental project measures for peripheral spaces around children's parks, based on the survey of children's park users' consciousness on peripheral spaces. Physical space range for this study was limited to low-rise housing area wihtin the radius of 250m, as peripheral spaces around children's parks in which children's playgrounds were built. In addition, the target areas for examining users' consciousness on peripheral spaces around children's parks were selected according to following criteria. 1)areas with highter portion of children; 2) those with higher portion of single-family houses/multi-housing/tenement houses, which constitute low-rise housing areas; and 3) those with higher safety accident rate of children, which was measured based on criminal and traffic accidents. The finding are as follows: first, users' consciousness on safety accidents that are likely to occur in peripheral spaces around children's parks was examined to show that there is most prominent difference between satisfaction and necessity. This result suggests that users are clearly conscious of the necessity of environmental improvement rather than the satisfaction with the current peripheral environment around children's park.; second, for the difference between satisfaction with and necessity of environmental project factors for access/boundary spaces around children's pakrs, there is most significant difference between the satisfaction with and the necessity of establishment of facilities against illegal parking for clear visibility of community roads, for access spaces, and the separate establishment of bicycle racks around main entry into parks, for boundary spaces. Users' necessity of the establishment of them is judged to be derived from the fact that the safety of children and even adults is threatened, because bicycles invaded into the deep inside of children parks. This study analyzed a correlation between satisfaction and necessity through factor and IPA analysis, and should be initially considenred if the future environmental improvement project would be conducted to promote safe environment in peripheral spaces around children's parks in the future. It will be necessary to provide practical environmental project factors through a field investigation.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• 제32권1호
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• pp.78-88
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• 2022

Objectives: To develop the smart sensor to protect worker's health from chemical exposure by adopting ICT (Information and Communications Technology) technologies. Methods: To develope real-time chemical exposure monitoring system, IoT (Internet of Things) sensor technology and regulations were reviewed. We developed and produced smart sensor. A smart sensor is a system consisting of a sensor unit, a communication unit, and a platform. To verify the performance of smart sensors, each sensor has been certified by the Korea Laboratory Accreditation Scheme (KOLAS). Results: Chemicals (TVOC; Total Volatile Organic Compounds, Cl₂: Chlorine, HF: Hydrogen fluoride and HCN: Hydrogen cyanide) were selected according to a priority logic (KOSHA Alert, acute poisoning statistics, literature review). Notifications were set according to OEL (occupational exposure limit). Sensors were selected based on OEL and the capabilities of the sensors. Communication is designed to use LTE (Long Term Evolution) and Wi-Fi at the same time for convenience. Electronic platform were applied to build this monitoring system. Conclusions: Real-time monitoring system for OEL of hazardous chemicals in workplace was developed. Smart sensor can detect chemicals to complement monitoring of traditional workplace environmental monitoring such as short term and peak exposure. Further research is needed to expand the scope of application, improve reliability, and systematically application.

• Journal of the Korean GEO-environmental Society
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• 제22권12호
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• pp.33-40
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• 2021

The deterioration of underground facilities, disturbance of the ground due to underground development activities, and changes in ground water can cause ground subsidence accidents in the urban areas. The investigation on the geotechnical and hydraulic factors affecting the ground subsidence accident is very significant to predict the ground subsidence risk in advance. In this study, an analysis DB was constructed through 3D ground modeling to utilize the currently operating geotechnical survey information DB and ground water behavior information for risk prediction. Additionally, using these results, the relationship between the actual ground subsidence occurrence history and ground conditions and ground water level changes was confirmed. Furthermore, the methodology used to visualize the risk of ground subsidence was presented by reconstructing the engineering characteristics of the soil presented according to the Unified Soil Classification System (USCS) in the existing geotechnical survey information into the internal erosion sensitivity of the soil, Based on the result, it was confirmed that the ground in the area where the ground subsidence occurred consists of more than 40% of sand (SM, SC, SP, SW) vulnerable to internal erosion. In addition, the effect of the occurrence frequency of ground subsidence due to the change in ground water level is also confirmed.

• Journal of the Society of Disaster Information
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• 제18권4호
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• pp.817-827
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• 2022

The real-name safety management system is to indicate "safety" after inspection by construction personnel before workers use it for the purpose of preventing safety accidents caused by unsafe conditions in temporary facilities and temporary constructions installed at construction sites. Purpose: By implementing the real-name system for safety management at construction sites, the objective is to respond to the "Severe Accident Punishment Act" and to improve the level of safety management at the same time. Method: In this study, a hierarchical analysis model was produced through previous studies of actual conditions such as types of safety incidents and causality at construction sites. The AHP model was used to calculate integrated weights and rankings with a pairwise comparison questionnaire for experts. Conclusion: As a result of the analysis of the upper classes, construction machinery was evaluated the highest, and real-name management system was evaluated the lowest. As a result of the lower-level analysis, it was considered that opening doors for safety facility management, tower cranes for construction equipment, management under the "Occupational Safety and Health Act" under the real-name management system, and CEO duties for safety management organizations were the most important.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• 제33권2호
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• pp.215-229
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• 2023

Objectives: To validate the effectiveness of a real-time chemical exposure monitoring system developed by KOSHA (Korea Occupational Safety and Health Agency), we applied the system to a workplace in the electronics industry for 153 days. Methods: The monitoring system consisted of a PID chemical sensor, a LTE communication equipment, and a web-based platform. To monitor chemical exposure, four sets of sensors were placed in two manufacturing tasks - inspection and jig cleaning - which used TCE as a degreasing agent. We reviewed previous reports of work environment measurements and conducted a new work environment measurement on one day during the period. The PID sensor systems detected the chemical exposure levels in the workplace every second and transmitted it to the platform. Daily average and maximum chemical exposure levels were also recorded. Results: We compared the results from the real-time monitoring system and the work environment measurement by traditional methods. Generally, the data from the real-time monitoring system showed a higher level because the sensors were closer to the chemical source. We found that 28% of jig cleaning task data exceeded the STEL. Peak exposure levels of sensor data were useful for understanding the characteristics of the task's chemical use. Limitations and implications were reviewed for the adoption of the system for preventing poisoning caused by chemical substances. Conclusions: We found that the real-time chemical exposure monitoring system was an efficient tool for preventing occupational diseases caused by chemical exposure, such as acute poisoning. Further research is needed to improve the reliability and applicability of the system. We also believe that forming a social consensus around the system is essential.