• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.13 no.4
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• pp.243-251
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• 2015

Nuclear power is currently the second largest power supply method in Korea and the number of nuclear power plants are planned to be increased as well. However, clear management policy for spent fuels generated from nuclear power plants has not yet been established. The back-end fuel cycle, associated with nuclear material flow after nuclear reactors is a collection of technologies designed for the spent fuel management and the spent fuel management policy is closely related with the selection of a nuclear fuel cycle. Cost is an important consideration in selection of a nuclear fuel cycle and should be determined by adding external cost to private cost. Unlike the private cost, which is a direct cost, studies on the external cost are focused on nuclear reactors and not at the nuclear fuel cycle. In this research, external cost indicators applicable to nuclear fuel cycle were derived and quantified. OT (once through), DUPIC (Direct Use of PWR SF in CANDU), PWR-MOX (PWR PUREX reprocessing), and Pyro-SFR (SFR recycling with pyroprocessing) were selected as nuclear fuel cycles which could be considered for estimating external cost in Korea. Energy supply security cost, accident risk cost, and acceptance cost were defined as external cost according to precedent and estimated after analyzing approaches which have been adopted for estimating external costs on nuclear power generation.

• Journal of Korean Elementary Science Education
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• v.35 no.1
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• pp.26-38
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• 2016

The purpose of this study was to grasp the characteristics of composition regarding the material-centered integrated unit of environmental and natural studies, a science subject in Finland, to investigate a need for applying the material-centered integrated unit to the science curriculum of Korea. For the purpose, the study made an analysis on contents, inquiry activities, and visual materials (the most important in the elementary science curriculum and textbook composition), and it brought following results: First, as a result of analyzing the area of contents, the bicycle material-centered integrated unit comprised a large proportion of 44 pages (25.3%) of the whole 174 pages from the environmental and natural studies textbook for the third grade. The contents included such various concepts as traffic rules, safety, environmental protection and pollution, recycling and separate collection, tubes and triangular structures, wedges and screws, leverage, wheels, axles, gears, elasticity (spring), friction, and so on. Second, as a result of analyzing contents related to the thinking ability of inquiry activities, "expecting or confirming expectations" and "application" are included in every lesson, and one lesson is composed in such a way that students can study on bicycles as a practical material for their daily life and they can improve various thinking abilities. Third, as a result of analyzing the circumstances of inquiry activities, daily circumstances made up eight lessons (80.0%) and technical and social circumstances made up two lessons (20.0%) by focusing on bicycles, a material related to students' daily life. Fourth, as a result of analyzing visual materials, the percentage of pictures and photos was high at 53.4% and 45.2% respectively. As a result of analyzing the role of visual materials, the percentage of the illustrative role and explanatory-complementary role was high at 52.1% and 47.9% respectively. Lastly, as a result of analyzing from the epistemological view to interpret the relation between visual materials and students and the position of visual materials, the visual textbook materials were provided toward a way that students can decrease their feeling of epistemological separation in the three fields of ideational metafunction, interpersonal metafunction, and textual metafunction.

• Korean Journal of Environmental Agriculture
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• v.19 no.2
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• pp.171-176
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• 2000

A wastewater treatment pond system was developed for treatment and recycling of dairy cattle excreta of $5\;m^1$ per day. The wastes were diluted by the water used for clearing stalls. The system was composed of three ponds in series. A submerged gas collector for the recovery of methane was installed at the bottom of secondary pond with water depth of 2.4m. This paper deals mainly with performance of methane fermentation of secondary pond which is faclutative one. The average $BOD_5$, SS, TN, and TP concentrations of influent into secondary pond were 49.1, 53.4, 48.6, and 5.3 mg/l, and those of effluent from it were 27.9, 45.7, 30.8, 3.2 mg/l respectively. Methane fermentation of 2.4-meter-deep secondary pond bottom was well established at $16^{\circ}C$ and gas garnered from the collector at that temperature was 80% methane. Literature on methane fermentation of wastewater treatment ponds shows that methane bacteria grow well around $24^{\circ}C$, the rate of daily accumulation and decomposition of sludge is approximately equal at $19^{\circ}C$, and activities of methanogenic bacteria are ceased below $14^{\circ}C$. The good methane fermentation of the pond bottom around $16^{\circ}C$, about $3^{\circ}C$ lower than $19^{\circ}C$, results from temperature stability, anaerobic condition, and neutral pH of the bottom sludge layer. It is recommended that the depth of pond water could be 2.4m. Gas from the collector during active methane fermentation was almost 83% methane, less than 17% nitrogen. Carbon dioxide was less than 1% of the gas, which indicates that carbon dioxide produced in bottom sludges was dissolved in the overlaying water column. Thus a purified methane can be collected and used as energy source. Sludge accumulation on the pond bottom for a nine month period was 1.3cm and annual sludge depth can be estimated to be 1.7cm. Design of additional pond depth of 0.3m can lead to 15 - 20 year sludge removal.