• Nuclear Engineering and Technology
• /
• 제54권10호
• /
• pp.3949-3956
• /
• 2022

Kori Unit 1 is planning a system decontamination project to reduce radiation exposure of decommissioning workers, prevent the spread of contamination and down-grade the level of classification of radioactive waste. The system decontamination range for Kori Unit 1 will be the entire primary system, including RCS, CVCS and RHRS. Some system design modifications are required for the system decontamination operation. In this paper, major system design modifications were evaluated based on the conditions that system restoration is needed after completion of system decontamination. The major system design modifications are CIDF connection location to system, system decontamination operating pressure control, RCP seal water injection and formation of letdown flow. It was evaluated that there was no negative effect on the system due to the system design modifications. However, as the RCP seal water is injected into the system in the oxidation process, the concentration of the oxidizing agent is diluted. Therefore, the oxidizing agent injection and system decontamination operation procedures should be developed to address the dilution effect of the oxidizing agent. The system design modifications dealt in this paper will be finally confirmed through on-site investigation in the future, and if necessary, the system design modifications will be re-evaluated.

• 반도체디스플레이기술학회지
• /
• 제18권4호
• /
• pp.62-68
• /
• 2019

The optoelectronic display units such as TFT-LCD or OLED require many thin optical plastic films and their mass manufacturing processes employ CO2 laser cutting of those thin films in a large quantity. However, laser film cutting could generate fume particles through melt shearing, vaporization, and chemical degradation and those particles could be of great concern for film surface contamination. In order to appreciate the fume particle dispersion behaviors in laser film cutting, this study relies on random particle simulations by probabilistic distributions of particle size, ejection velocity and angles coupled with Basset-Boussinesq-Oseen model of particle trajectory in low Reynolds number flows. Here, up to one million particles of random sampling have been tested to effectively show fume particles dispersed on the film surface. The computational results could show that particular range of fume particle size could easily disperse into the pixel region of processed optical films.

• 한국환경보건학회지
• /
• 제27권1호
• /
• pp.1-7
• /
• 2001

Ammonia is used in the manufacture of fertilizers, refrigerants, stabilizers and many household cleaning agents. These wide applications resulted in ammonia contamination in water. Ammonia can be removed from water by physical, biological, and chemical methods. Ozonation is effictive in the treatment of water with low concentration of ammonia. This study is undertaken to provide kinetic data for the ozonation of ammonia with or without hydrogen peroxide. The results were as follows; The destruction rate of ammonia increased gradually with the influent hydrogen peroxide concentration up to 0.23 mM and inhibited in the range of 0.23~11.4mM, and the maximum removal rate of ammonia achieved at 0.23mM of hydrogen peroxide, and the overall kinetics was first order. The combination effect of hydrogen and ozone to oxide ammonia in aqueous solution was better than ozone alone. The reacted ammonia was converted completely to nitrate ion.

• 한국환경과학회지
• /
• 제16권5호
• /
• pp.657-664
• /
• 2007

The content and distribution of some heavy metals (Fe, Mn, Cr, Co, Cu, Ni, Zn and Pb) were investigated in the <$63{\mu}m$ bed sediments of the Mangyeong river to recognize the extent of contamination. Results showed that a wide range of concentrations was apparent for every metal. These variations were particularly significant at the confluence of tributaries. High levels of metals occur mainly in the confluence of tributaries. Geoaccumulation indexes have been calculated to assess whether the concentration observed represent background or contaminated levels. It is proved that the Mangyeong River is moderately to strongly polluted for Mn, Cr, Cu, Zn and Pb. The spatial extent of pollution was examined, and it was found that the most polluted area is located in the confluence of Iksan and Jeonju tributaries.

• Advances in environmental research
• /
• 제4권3호
• /
• pp.183-196
• /
• 2015

Migration of leachate generated through embankment of construction waste soil (CWS) in low-lying areas was studied through physical and chemical analysis. A leachate solution containing soluble cations from CWS was found to have a pH above 9.0. To determine the distribution coefficients in the alkali solution, column and migration tests were conducted in the laboratory. The physical and chemical properties of CWS satisfied environmental soil criteria; however, the pH was high. The effective diffusion coefficients for CWS ions fell within the range of $0.725-3.3{\times}10^{-6}cm^2/s$. Properties of pore water and the amount of undissolved gas in pore water influenced advection-diffusion behavior. Contaminants migrating from CWS exhibited time-dependent concentration profiles and an advective component of transport. Thus, the transport equations for CWS contaminant concentrations satisfied the differential equations in accordance with Fick's 2nd law. Therefore, the migration of the contaminant plume when the landfilling CWS reaches water table can be predicted based on pH using the effective diffusion coefficient determined in a laboratory test.

• 한국식품영양과학회지
• /
• 제20권6호
• /
• pp.615-620
• /
• 1991

This study was performed to investigate the contamination level of harmful metals in 4 species of freshwater fishes collected at the three sampling sites of Yeong san river from January to October in 1990. The levels of total mercury, lead, zinc, manganese, copper and cadmium were ditermined and the results were summarized as follows : The overall range(ppm) were Hg, 0.022~0.139 ; Pb, 0.666~0.984 ; Zn, 8.673~15.214 ; Mn, 2.751~5.049 ; Cu, 0.328~1.174 ; Cd, 0.017~0.052. Among the six heavy metals contents, the highest was zinc and the lowest was cadmium. The results showed that all the 4 species of freshwater fishes of Yeong san river studied have not yet dangerous levels enough to pose a health problem.

• 동아시아식생활학회지
• /
• 제19권1호
• /
• pp.116-129
• /
• 2009

The study was conducted to evaluate consumer awareness of the risk elements associated with foods and their information search behavior regarding food safety. The data were collected from 504 adult consumers living in Seoul, Busan, Incheon, Daegu, Daejeon, and Gwangju through a self-administered questionnaire on August, 2006. Frequency analyses, t tests, one-way analysis of variance, and Duncan's multiple range comparison tests were conducted to analyze the responses using SPSS v. 14.0. The levels of recognition of consumers regarding each risk element were generally low. Many respondents answered that they obtained information regarding food safety from TV/radio/newspapers and family/relatives/friends/neighbors. The respondents also indicated that they had strong confidence in the information from family/relatives/friends/neighbors. Additionally, most respondents required information regarding heavy metal contamination, endoctrine disruptors, and avian influenza.

• 한국환경과학회지
• /
• 제15권12호
• /
• pp.1171-1175
• /
• 2006

Deposited road particles (DRPs) were analysed for heavy metal concentrations at four different roads in a city, Korea. The samples were collected using a roadway surface vacuum cleaning vehicle which was commonly used in collecting roadway surface particles. Six particle size ranges were analyzed separately for twelve heavy metal elements (Cd, Cr, Pb, Ni, Al, As, Co, Cu, Fe, Mn, Zn and Hg). At all sampling sites, the high concentration of the heavy metals occurred in the <74um particle size range, which conventional roadway cleaning vehicles do not remove efficiently. The Pb concentration significantly increased with decreasing particle size of DRPs, and other toxic heavy metals (Cd, Cr and Ni) also showed similar results. The heavy metal concentrations in the smaller size fraction of DRPs is important because they are contaminants that are preferentially transported by road runoff during rainfall.

• 환경생물
• /
• 제25권1호
• /
• pp.27-33
• /
• 2007

Sediment microcosm experiments were conducted for 14 and 28 days using Zn spiked sediment to examine chronic toxicity (mortality) of Diporeia spp. as a function of density and time. Mean cumulative Diporeia mortality in 28 day sediment microcosms was 25% at $1,800\;{\mu}g\;g^{-1}$ total Zn in sediment. Although a certain fraction $(20{\sim}40%)$ of Diporeia was dead, its mortality was attributed by handling stress within 4 days and was not significantly encreased with increasing within the range of Zn concentrations examined in this study. These results suggest that Diporeia can tolerate Zn contaminated sediment and may be useful as a biomonitor for Zn contamination in freshwater environments.

• Journal of Welding and Joining
• /
• 제17권5호
• /
• pp.83-88
• /
• 1999

In this paper resistance projection weldability of Zn coated steels with post treatment has been discussed. Projection welding was performed by a condenser discharge type power source which was equipped with welding parameter monitoring system. Mechanical test results indicated that the effect of post coatings on the projection front changed showing very small very small spattering at the weld strength was negligible. However, contamination rate of the block electrode varied depending on the post treatment coatings. Test results also showed that projection height before welding should be kept to be 80-100% of the specimen thickness as far as the surface quality was taken into consideration. Based on the high speed photography, discharge condition at the beginning stage of the welding process. It was considered that the spattering reduced the weld strength slightly at the optimum heat input range.