• Nuclear Engineering and Technology
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• v.38 no.1
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• pp.45-60
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• 2006

Presently, the VHTGR (Very High Temperature Gas-cooled Reactor) is considered the most attractive candidate for a GEN-IV reactor to produce hydrogen, which will be a key resource for future energy production. A new concept for a reactor cavity cooling system (RCCS), a critical safety feature in the VHTGR, is proposed in the present study. The proposed RCCS consists of passive water pool and active air cooling systems. These are employed to overcome the poor cooling capability of the air-cooled RCCS and the complex cavity structures of the water-cooled RCCS. In order to estimate the licensibility of the proposed design, its performance and integrity were tested experimentally with a reduced-scale mock-up facility, as well as with a separate-effect test facility (SET) for the 1/4 water pool of the RCCS-SNU to examine the heat transfer and pressure drop and code capability. This paper presents the test results for SET and validation of MARS-GCR, a system code for the safety analysis of a HTGR. In addition, CFX5.7, a computational fluid dynamics code, was also used for the code-to-code benchmark of MARS-GCR. From the present experimental and numerical studies, the efficacy of MARS-GCR in application to determining the optimal design of complicated systems such as a RCCS and evaluation of their feasibility has been validated.

• Nuclear Engineering and Technology
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• v.47 no.4
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• pp.416-423
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• 2015

It had been disputed how to apply wall drag to the dispersed phase in the framework of the conventional two-fluid model for two-phase flows. Recently, Kim et al. [1] introduced the volume-averaged momentum equation based on the equation of a solid/fluid particle motion. They showed theoretically that for dispersed two-phase flows, the overall two-phase pressure drop by wall friction must be apportioned to each phase, in proportion to each phase fraction. In this study, the validity of the proposed wall drag model is demonstrated though one-dimensional (1D) simulations. In addition, it is shown that the existing form loss model incorrectly predicts the motion of the dispersed phase. A new form loss model is proposed to overcome that problem. The newly proposed form loss model is tested in the region covering the lower plenum and the core in a nuclear power plant. As a result, it is shown that the new models can correctly predict the relative velocity of the dispersed phase to the surrounding fluid velocity in the core with spacer grids.

• Nuclear Engineering and Technology
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• v.44 no.7
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• pp.709-718
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• 2012

The pressurized water reactor APR1400 adopts DVI (Direct Vessel Injection) for the emergency cooling water in the upper downcomer annulus. The International Standard Problem number 50 (ISP-50) was launched with the aim to investigate thermal hydraulic phenomena during a 50% DVI line break scenario with best estimate codes making use of the experimental data available from the ATLAS facility located at KAERI. The present work describes the calculation results obtained for the ISP-50 using the RELAP5/MOD3.3 system code. The work aims at validation and assessment of the code to reproduce the observed phenomena and investigate about its limitations to predict complicated mixing phenomena between the subcooled emergency cooling water and the two-phase flow in the downcomer. The obtained results show that the overall trends of the main test variables are well reproduced by the calculations. In particular, the pressure in the primary system show excellent agreement with the experiment. The loop seal clearance phenomenon was observed in the calculation and it was found to have an important influence on the transient progression. Moreover, the collapsed water levels in the core are accurately reproduced in the simulations. However, the drop in the downcomer level before the activation of the DVI from safety injection tanks was underestimated due to multi-dimensional phenomena in the downcomer that are not properly captured by one-dimensional simulations.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.1 s.232
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• pp.107-114
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• 2005

In order to analyze the elastic-plastic fracture behavior of a structure, the fracture resistance curve of the material should be known first. The standard CT specimen was used to obtain the fracture resistance curves of a piping system. However, it is known that the fracture resistance curve by the standard CT specimen is very conservative to evaluate the integrity of a structure. Also the fracture resistance curve is effected by the specimen geometry and the dimensions because of the constraint effect. The objective of this paper is to be certain the conservativeness of the fracture resistance curve by the standard CT specimen and to provide an additional safety margin. For these, the fracture tests using a real pipe specimen and the standard CT specimen test were performed. A 4-point bending jig was manufactured for the pipe test and the direct current potential drop method was used to measure the crack extension and the length for the pipe test. Also finite element analyses were performed with a CT specimen and a pipe in order to prove the additional safety margin. From the result of tests and analyses of the pipe and the standard CT specimen, it was observed that the fracture analysis with the standard CT specimen is conservative and the additional safety margin was proved.

• Proceedings of the Korean Society of Disaster Information Conference
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• 2023.11a
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• pp.129-130
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• 2023

The From COVID-19 until recently, the demand for hiking has been rapidly increasing due to the popularization of mountain seekers.,On weekends and holidays, people who do not hike frequently while hiking in large and small mountains to see wildflowers and foliage in the mountains are more likely to be exposed to safety accidents due to an increase in sudden muscle use.,If you fall or get muscle damage during a hike, you can prevent a major accident with a simple treatment. In some cases, the error of first aid may permanently damage the important function of the body.,In particular, during a safety accident on a mountain, while climbing in light clothes, the body temperature rises due to the sweat that was shed at the beginning, and the blood pressure rises due to the contraction of the blood vessels due to the drop in body temperature from the top, resulting in an emergency such as cardiac arrest.,According to statistics from the National Park Service, nearly half (48%) of deaths in national parks are known to be sudden cardiac deaths.,There are many safety accidents that occur frequently in the mountains, but among them, we will study how to cope with acute diseases such as cardiac arrest due to increased blood pressure due to insufficient body temperature control, chest pain or dyspnea, and heart burden due to excessive hiking.

• Korean Journal of Construction Engineering and Management
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• v.23 no.1
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• pp.46-53
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• 2022

The railway platform is an important facility closely related to the safety of passengers, trains, and images of railway facilities, and requires thorough facility management. However, the problem that the finishing material (plastering mortar) for the joint finishing of dissimilar materials (concrete+granite) falls off in the direction of the track at the platform podium is occurring multiple times across the country. Since these problems threaten the safety of train operation and the safety of passengers, immediate and continuous management is required. This study tried to derive improvement plans through the analysis of the drop-off problem of finishing materials occurring at the platform podium. The status of missing finishing materials for the platform podiums of about 200 railway stations and the related design and construction standards of the Korea National Railway were investigated. After that, the cause of the drop-off of the finishing material was analyzed, and as a result, it was found that the main cause was the boundary between the roadbed and the architectural process that occurred during construction. Subsequently, in connection with the derived causes and design, construction standards, (1) improvement of finishing materials or construction methods, (2) design of finishing materials that are easy to adjust height, (3) design of separate finishing methods, (4) improvement methods and durability were suggested.

• Journal of the Korea Institute of Building Construction
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• v.17 no.4
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• pp.349-360
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• 2017

In concrete construction work, formwork is an important process that accounts for 10% of the total construction cost. Recent buildings are becoming bigger and higher. In order to maximize the efficiency and safety of this formwork, the system of formworking has been systematized. However, the human accidents and the noise complaints arise from dismantling processes frequently occur. In order to solve these problems, most of them are dependent on foreign technology, but they do not take into consideration the conditions of domestic construction site. In this study, we developed a table type multi-drop system form for a slab and beam which can improve the process, safety and reduction of disassembly noise, and evaluated the physical properties of the main members which are used in the system. The results of this study show that there is sufficient strength to be used as a slab and a laying material for both a yoke beam and a supporting post. The noise level is improved compared to existing method.

• Journal of the Korea Institute of Building Construction
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• v.24 no.1
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• pp.97-108
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• 2024

This research delves into the escalating concerns of accidents and fatalities in the construction industry over the recent five-year period, focusing on the development of a Safety Perception Model to augment safety measures. Given the rising percentage of elderly workers and the concurrent drop in productivity within the sector, there is a pronounced need for leveraging Fourth Industrial Revolution technologies to bolster safety protocols. The study comprises an in-depth analysis of statistical data regarding construction-related fatalities, aiming to shed light on prevailing safety challenges. Central to this investigation is the formulation of a Safety Perception Model tailored for small-scale construction projects. This model facilitates the quantification of safety risks by evaluating safety grades across construction sites. Utilizing the DWM1000 module, among an array of wireless communication technologies, the model enables the real-time tracking of worker locations and the assessment of safety levels on-site. Furthermore, the deployment of a safety management system allows for the evaluation of risk levels associated with individual workers. Aggregating these data points, the Safety Climate Index(SCLI) is calculated to depict the daily, weekly, and monthly safety climate of the site, thereby offering insights into the effectiveness of implemented safety measures and identifying areas for continuous improvement. This study is anticipated to significantly contribute to the systematic enhancement of safety and the prevention of accidents on construction sites, fostering an environment of improved productivity and strengthened safety culture through the application of the Safety Perception Model.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.37 no.4
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• pp.747-757
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• 2017

Of safety check regulation, 'Construction Technology Promotion Act' and 'Special Act on the Safety Control of Public Structures' contain provisions about the content of safety in construction works and the items of safety checks in the maintenance aspect and thus contribute to accident prevention in the construction industry. Of the regulations responsible for the practical safety of workers, the safety check regulation of Ministry of Employment and Labor demand for safety check from the start of construction based on an agreement with a concerned agency to the completion of construction solely based on 'Guidance Standards for the Specialized Disaster Prevention Instruction in Article 32 of Occupational Safety and Health Act' and 'Appropriation and Usage Standards of Safety and Health Management Costs in the Construction Industry'. There is, however, a huge gap, as well, in them according to client agencies. In small construction sites ordered by a private organization, checks are done formally with no detailed regulations. As a result, the costs of checks continue to drop with only the contract kept intact. This study examined the forms of safety checks practically done in the Jeju region, distinguished and compared them by the construction costs, calculated proper costs based on each construction act, and further proposed improvement measures for the detailed regulations.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.10
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• pp.454-461
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• 2017

The purpose of this study is to investigate the types of domestic safety accidents involving children and to verify the difference of safety knowledge according to variables of parents. Subjects include 226 parents who have 3-5 year old infants enrolled in kindergartens and day care centers in I-city, Jeollabuk-do. The study tools are modified and complemented questionnaire for the study purpose referred to the preceding research data and the literature. For the processing of collected data, frequency analysis, descriptive statistics, one-way ANOVA, and the Duncan post-test were utilized using the SPSS program. The results of this study are as follows: First, safety accidents occurred at the majority of homes which have infant children. On average, the occurrence frequency was 1.78 times per six months. The accidents involving infants occurred in the order of drop or slip, crash or impact, stricture or jamming, fall, stab or cut, burn, swallow or inhalation. Second, both parents had an average level of safety knowledge. There was a distinction in the areas of 'fall' and 'first aid' according the mother's age. In addition, stay-at-home mothers had the higher level of safety knowledge compared with working mothers in the areas of 'general safety knowledge' and 'fire'. There was a distinction in the area of 'fire' according to the father's age. Given these findings, safety training programs for parents to improve safety knowledge needs to be developed.