• Journal of radiological science and technology
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• v.26 no.3
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• pp.51-57
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• 2003

Mitigation of fast neutron irradiation damage on reactor vessel and improvement of mechanical integrity are desired for the successful plant life-time extension. In this study, the performance of metallic hydride for this application is reviewed and compared. First, selected prospective metallic hydrides are evaluated by MCNP code and put into the attenuation test using Cf-252 neutron source. Since for the reactor application high moderation and reflection with no absorption are favored, Z factor is introduced for the evaluation. According to the Z value estimation $ZrD_2$ and $TiD_2$ are turned out to be the most favorable fast neutron shielding materials. More thorough evaluation by computer simulation and experimentally, will be followed.

• Journal of Korean Society on Water Environment
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• v.24 no.2
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• pp.147-155
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• 2008

Because of increased nonpoint source runoff potential at highland agricultural fields of Kangwon province, effective agricultural management practices are required to reduce the inflow of sediment and other nonpoint source pollutants into the water bodies. The watershed-scale model, Soil and Water Assessment Tool (SWAT), model has been used worldwide for developing effective watershed management. However, the SWAT model simulated sediment values are significantly affected by the number of subwatershed delineated. This result indicates that the SWAT estimated watershed characteristics from the watershed delineation process affects the soil erosion and sediment behaviors. However, most SWAT users do not spend time and efforts to analyze variations in sediment estimation due to watershed delineation with various threshold value although topography falsification affecting soil erosion process can be caused with watershed delineation processes. The SWAT model estimates the field slope length of Hydrologic Response Unit (HRU) based on average slope of subwatershed within the watershed. Thus the SWAT ArcView GIS Patch, developed by using the regression relationship between average watershed slope and field slope length, was utilized in this study to compare the simulated sediment from various watershed delineation scenarios. Four watershed delineation scenarios were made with various threshold values (700 ha, 300 ha, 100 ha, and 75 ha) and the SWAT estimated flow and sediment values were compared with and without applying the SWAT ArcView GIS Patch. With the SWAT ArcView GIS Patch applied, the simulated flow values are almost same irrespective of the number of subwatershed delineated while the simulated flow values changes to some extent without the SWAT ArcView GIS Patch applied. However when the SWAT ArcView GIS Patch applied, the simulated sediment values vary 9.7% to 29.8% with four watershed delineation scenarios, while the simulated sediment values vary 0.5% to 126.6% without SWAT ArcView GIS applied. As shown, the SWAT estimated flow and sediment values are not affected by the number of watershed delineation significant compared with the estimated flow and sediment value without applying the SWAT ArcView GIS Patch.

• Geophysics and Geophysical Exploration
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• v.14 no.1
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• pp.69-79
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• 2011

In this study, empirical site amplifications and S-wave velocity profiles for shallow and deep soils are estimated using earthquake ground motion records in metropolitan Manila, the Philippines. We first apply a spectral inversion technique to the earthquake records to estimate effects of source, path, and local site amplification. The earthquake data used were obtained during 36 moderate earthquakes at 10 strong-motion stations of an earthquake observation network in Manila. The estimated Q value of the propagation path is modelled as $54.6f^{1.1}$. Most of the source spectra can be approximated with the omega-square model. The site amplifications show characteristic features according to surface geological conditions. The amplifications at the sites in the coastal lowland and Marikina Valley shows predominant peaks at frequencies from 1 to 5 Hz, while those in the central plateau are characterised by no dominant peaks. These site amplifications are inverted to subsurface S-wave velocity. We, next, discuss the relationship between the amplifications and average S-wave velocity in the top 30m of the S-wave velocity profiles. The amplifications at low frequencies are well correlated with the averaged S-wave velocity. However, high-frequency amplifications cannot be sufficiently explained by the averaged S-wave velocity in the top 30 m. They are correlated more with the average of S-wave velocity over depths less than 30 m.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.4
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• pp.385-389
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• 2005

To understand the pollution level by polychlorinated biphenyls (PCBs) in ambient air of industrial area, PCBs concentrations were measured at Sihwa and Banwol industrial region, Korea. The concentrations of total PCB and WHO-TEQ ranged from 2,080 to $5820\;pg/m^3$ (median value is 2,760) and from 0.19 to $1.01\;pgTEQ/m^3$ (median value is 0.42), respectively. In terms of homologues composition the fraction of highly chlorinated biphenyls(from hexa-CB to deca-CB) were higher than the air samples of other regions such as jeonju and yokohama area. The cluster analysis was conducted to study the relation between the air samples and sources such as incinerator flue gases and Aroclor samples. The isomer fractions in the homologue were used as input variables. Based on the results, the industrial ambient air samples were divided from source samples with long Euclidian distance. This suggest that the ambient air samples of Sihwa and Banwol were not on the influence of Aroclor and incinerators. Therefore, further investigation on systematical air monitoring will be required to estimate the sources of PCBs in the above industrial areas.

• The Journal of the Korea Contents Association
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• v.14 no.6
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• pp.255-261
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• 2014

The generation amount of radioactive waste has been rapidly increased by increase of the usage of radioisotope source in medical field. Especially, the use of the radioactive source of I-131 with short half-life of 8.02 days used in treatment of thyroid has been increased, and all of the wastes concerned have been disposed by means of the self-disposal method. IAEA proposed criteria for clearance level of waste which depends on the individual (10 ${\mu}Sv/y$) and collective dose (1 man-Sv/y), and concentration of each nuclide (IAEA Safety Series No 111-P-1.1, 1992 and IAEA RS-G-1.7, 2004). In this study, various radioactive wastes in medical fields are collected and measured for establishing the disposal methods and procedures of radioactive wastes. In addition, comparison evaluation of decay storage period between the half-life which was calculated by attenuation curve based on real measurement and analytical half-life is considered. With comparing the theoretical half-life and the effective half life(7.72 days) which was based on the decay equation of measured data, it is resulted in the theoretical half-life is longer than effective half-life. The storage period of radioactive waste for self-disposal may be curtailed. The result of this study will be proposed as ISO standard.

• Nutrition Research and Practice
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• v.9 no.6
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• pp.650-657
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• 2015

BACKGROUND/OBJECTIVES: The aim of this study was to estimate average total fat and fatty acid intakes as well as identify major food sources using data from the Korea National Health and Nutrition Examination Survey (KNHANES) VI-1 (2013). SUBJECTS/METHODS: Total fat and fatty acid intakes were estimated using 24-hour dietary recall data on 7,048 participants aged ${\geq}3years$ from the KNHANES VI-1 (2013). Data included total fat, saturated fatty acid (SFA), monounsaturated fatty acid (MUFA), polyunsaturated fatty acid (PUFA), n-3 fatty acid (n-3 FA), and n-6 fatty acid (n-6 FA) levels. Population means and standard errors of the mean were weighted in order to produce national estimates and separated based on sex, age, income, as well as residential region. Major food sources of fat, SFA, MUFA, PUFA, n-3 FA, and n-6 FA were identified based on mean consumption amounts of fat and fatty acids in each food. RESULTS: The mean intake of total fat was 48.0 g while mean intakes of SFA, MUFA, PUFA, n-3 FA, and n-6 FA were 14.4 g, 15.3 g, 11.6 g, 1.6 g, and 10.1 g, respectively. Intakes of MUFA and SFA were each higher than that of PUFA in all age groups. Pork was the major source of total fat, SFA, and MUFA, and soybean oil was the major source of PUFA. Milk and pork were major sources of SFA in subjects aged 3-11 years and ${\geq}12years$, respectively. Perilla seed oil and soybean oil were main sources of n-3 FA in subjects aged ${\geq}50years$ and aged < 50 years, respectively. CONCLUSIONS: Estimation of mean fatty acid intakes of this study using nationally represented samples of the Korean population could be useful for developing and evaluating national nutritional policies.

• Journal of the Korea Organic Resources Recycling Association
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• v.27 no.4
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• pp.71-81
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• 2019

This research was conducted to improve availability of agricultural by-products, national natural resources that could be used as fertilizer source, by estimating the amount of production and collecting main contents of fertilizer substances from previous studies and data, in order to be used as basic data to investigate national resources that could be used as alternatives for imported oil-cakes in the future. Conversion factor was used to estimate annual production of agricultural by-products for main 34 crop types in 2018. For total agricultural by-products, rice straws accounted at 50.3% for the highest proportion, followed by 8.7% of rice husks, showing that by-products from rice harvest accounted at 59.0% for all by-products. Further, there were listed the contents of fertilizer substances (nitrogen, phosphoric acid, potash) in 40 types of by-products from agricultural areas. The average contents of nitrogen, phosphoric acid, and potash in agricultural by-products were 1.43%, 0.59%, and 1.90%, respectively. As a result of estimating the annual nitrogen supply amount from 26 agricultural by-products in 2018, it was found that it could supply 44,911 tons of nitrogen. The investigated by-products contained fertilizer substances such as nitrogen, phosphoric acid, and potash, but the contents were lower compared to castor oil-cake used as main component of organic fertilizer. Therefore, resource management plan needs to be established for efficient use of by-products because time, location, and nutrient content of agricultural by-product production were extremely different. Research on fertilizer and manure using agricultural by-products need to be conducted to develop and distribute alternatives for imported oil-cakes.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.260-260
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• 2011

SWAT is semi-distributed and continuous-time distributed simulation watershed model, which can simulate point and nonpoint source pollutants as well as hydrology and water quality. It was developed to predict the effects of alternative management decisions on water, sediment, and chemical yields with reasonable accuracy. It is able to predict and manage hydrology, sediments, nutrients, and pesticides with Best Management Practices (BMPs) in a watershed. SWAT model also has potential for use in ungauged basins to predict streamflow and baseflow from saturated source area in watersheds. According to various cultivation practices and climate change, SWAT model is available to analyze relative change in hydrology and water quality. In order to establish optimum management of water quality, both monitering and modeling have been conducted actively using SWAT model. As SWAT model is computer program to simulate a lot of natural phenomena, it has limitation to predict and reflect them with on hundred percent accuracy. Thus, it is possible to analyze the effect of BMPs in the watershed where users want to simulate hydrology and water quality only if model accuracy and applicability are assessed first of all and the result of it is well for the study watershed. For assessment of SWAT applicability, most researchers have used $R^2$ and Nash and Sutcliffe Efficiency (NSE). $R^2$ and NSE are likely to show different results according to a warm up period and sometimes its results are very different. There have been hardly any studies of whether warm up period can affect simulation results in SWAT model. In this study, how warm up period has a effect on SWAT results was analyzed and a appropriate warm up period was suggested. Lots of SWAT results were compared after using measured data of Soyanggang-dam watershed and applying various warm up period (0 ~ 10 year(s)). As a result of this study, when there was no warm up period, $R^2$ and NSE were 0.645, 0.602 respectively, when warm up period was 2 years, $R^2$ and NSE were 0.648, 0.632, and when warm up period was 4 years, $R^2$ and NSE were 0.663, 0.652 separately. Through this study, sensitive analysis of warm up period in SWAT model was conducted, and this study could give a guideline able to simulate hydrology and water quality for more accuracy than before as users change a lot of warm up periods as well as any simulation parameters.

• Environmental Analysis Health and Toxicology
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• v.25 no.4
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• pp.307-314
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• 2010

Objectives : Arsenic (As) is ubiquitously distributed in the environment and has been known as a human carcinogen. The main source of arsenic exposure in general population is an oral route through As-contaminated water and foods. This study was performed to estimate the daily intake of As from diet and associated factors in Korean adults. Methods : We investigated 590 adults, 249 males and 341 females, with age of 20 years and older, who had not been exposed to the As occupationally. Study subjects were interviewed for demographic characteristics, lifestyles and diets during the last 24 hours. The estimation of As intake daily was based on amount of food consumption and As concentration in each food by using database of As concentrations in 117 food species. Results : Daily As intake was estimated as $56.46\;{\mu}g$/day, $56.60\;{\mu}g$/day in male and $56.36\;{\mu}g$/day in female. As intake was not significant from sex, age group, smoking and alcoholic habits, while was by occupation with the most intake of As in fishery. The daily As intakes was positively correlated with the total food consumption, specifically related with fishes and shellfishes, seaweeds, oils, grains and flavors. About 75% of As intake from diet was contributed by seafoods, such as $32.07\;{\mu}g$/day from fishes & shellfishes and $10.05\;{\mu}g$/day from seaweeds. However, it is necessary to evaluate if the dietary As intake affects on the levels of As in the body. Conclusions : The amount of As intake daily in Korean adults was estimated as $56.46\;{\mu}g$/day, and is determined mainly by diet behavior. The seafoods, such as fishes & shellfishes and seaweeds, is major source of As exposure from diet in Korean.

• Journal of Radiation Protection and Research
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• v.42 no.2
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• pp.114-129
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• 2017

Background: The purpose of this paper is to confirm the event timings and the magnitude of fission product aerosol release from the Fukushima accident. Over a few hundreds of technical papers have been published on the environmental impact of Fukushima Daiichi accident since the accident occurred on March 11, 2011. However, most of the research used reverse or inverse method based on the monitoring of activities in the remote places and only few papers attempted to estimate the release of fission products from individual reactor core or from individual spent fuel pool. Severe accident analysis code can be used to estimate the radioactive release from which reactor core and from which radionuclide the peaks in monitoring points can be generated. Materials and Methods: The basic material used for this study are the initial core inventory obtained from the report JAEA-Data/Code 2012-018 and the given accident scenarios provided by Japanese Government or Tokyo Electric Power Company (TEPCO) in official reports. In this research a forward method using severe accident progression code is used as it might be useful for justifying the results of reverse or inverse method or vice versa. Results and Discussion: The release timing and amounts to the environment are estimated for volatile radioactive fission products such as noble gases, cesium, iodine, and tellurium up to 184 hours (about 7.7 days) after earthquake occurs. The in-plant fission product behaviors and release characteristics to environment are estimated using the severe accident progression analysis code, MELCOR, for Fukushima Daiichi accident. These results are compared with other research results which are summarized in UNSCEAR 2013 Report and other technical papers. Also it may provide the physically based arguments for justifying or suspecting the rationale for the scenarios provided in open literature. Conclusion: The estimated results by MELCOR code simulation of this study indicate that the release amount of volatile fission products to environment from Units 1, 2, and 3 cores is well within the range estimated by the reverse or inverse method, which are summarized in UNSCEAR 2013 report. But this does not necessarily mean that these two approaches are consistent.