• Proceedings of the Korean Radioactive Waste Society Conference
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• 2005.06a
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• pp.32-39
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• 2005

When PFC(Perfluorocarbonate) decontamination technology is applied to removal of radioactive contaminated particulate adhered at surface during the operation of nuclear research facilities, it is necessary to develop a filtration equipment to reuse of PFC solution due to high price, also to minimize the volume of second wastewater. Contaminated characteristics of hot particulate was investigated and a filtration process was presented to remove suspended radioactive particulate from PFC decontamination wastewater generated on PFC decontamination. The range of size of hot particulate adhered at the surface of research facilities measured by SEM was $0.1{\sim}10{\mu}m$. Hot particulate of more than $2{\mu}m$ in PFC contamination wastewater was removed by first filter and then hot particulate of more than $0.2{\mu}m$ was removed by second filter. Results of filter experiments showed that filtration efficiency of PVDF(Poly vinylidene fluoride), PP(Polypropylene), Ceramic filter was $95{\sim}97\%$. A ceramic filter showed a higher filtration efficiency with a little low permeate volume. Also, a ceramic of inorganic compound could be broken easily on experiment and has a high price but was highly stable at radioactivity in comparison of PVDF and PP of a macromolecule which generate $H_2$ gas in alpha radioactivity environment.

• Korean Journal of Agricultural and Forest Meteorology
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• v.1 no.2
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• pp.160-164
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• 1999

Subsurface environments, including the intermediate vadose zone and aquifers, may be contributing to increased atmospheric concentrations of $N_2$O. Denitrification appears to be the major source of $N_2$O in the subsurface environment. In the intermediate vadose zone, the level of denitrifying activity is dependent on the soil morphology, particularly stratified layers within the soil profile, which impede water and solute movement and create conditions favorable for denitrification. Movement of organic C from the soil surface appears to support denitrifying activity by providing an energy source and increasing the consumption of $O_2$. Denitrirication and $N_2$O production have been observed in aquifers but appear to be of greatest significance in shallow unconfined aquifers. The lack of organic C, N $O_2$, or anaerobiosis is often a limiting factor for activity but seems to be site specific. The presence of denitrifying bacteria does not appear to be a major limitation, based on published results, but the ubiquity of denitrifiers in subsurface environments needs to be confirmed. The fate of the $N_2$O produced in subsurface environments is unknown. Transport of $N_2$O by up ward diffusion, by outgassing at contacts with surface waters, and by ground water use need to be quantified to determine the contribution to atmospheric $N_2$O. Contamination of subsurface environment with N $O_3$$^{ }$ and organics has the potential for increasing the contribution to atmospheric $N_2$O by enhancing denitrification .

• Journal of Radiation Protection and Research
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• v.23 no.3
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• pp.175-184
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• 1998

In order to calculate dose rates from steam generators to be replaced from Kori unit 1 in 1998, radionuclide inventories inside steam generator were evaluated from smear test results and measured dose rates from S/G tubes withdrawn for the metallographical examination of damaged tubes. Based on the inventories, contact dose rates and dose rates at 1 m from the surface of a steam generator were calculated using the QAD-CG computer code. Contact dose rates ranged from 11.5 mR/hr at the bottom of channel head to 37.7 mR/hr at the middle of shell barrel, and showed no significant difference with dose rates at 1 m from the surface of steam generator. Shielding effects of lead and carbon steel were compared to provide basic shielding data. Lead shield showed excellent shielding effects. Dose rate at 1 m from the middle of S/G shell barrel decreased from 38.6 mR/hr to 15.5 mR/hr with the lead shield of 2 mm thickness. However, carbon steel showed a poor shielding effect even with the thickness of 2.0 cm. This can be explained with the great differences in the attenuation effect and buildup factor between lead and carbon steel for low energy photons.

• 한국문화재보존과학회:학술대회논문집
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• 2004.10a
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• pp.15-24
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• 2004

The Seokgatap pagoda composed of mainly alkali granite and other minor pink-feldspar granite, fine-grained granite, granodiorite, diorite, gabbro, and tuff. Despite the small loss and damage derived from joints, its peel-off and exfoliation are serious enough to cause the heavy deterioration on the stone surface. The chemical and petrological weathering has partly replaced the original rock-forming minerals with clay minerals and iron oxyhydroxides. Based on the petrogenesis, rock materials of the pagoda is very similar to rocks of Dabotap pagoda and the Namsan granite in the Gyeongju. The central fart of the pagoda has sunken highly, which caused all the corners to split and the structural transformation to become worse. The reverse V-shaped gaps between the materials have broken stones filled in a coarse way. The iron plates inserted between the upper flat stone laid on other stones and tile pagoda body in the north and east side has been exposed in the air and corroded, discoloring of the adjacent stones. The overall diagnosis of the Seokgatap pagoda is the deteriorated functions of the stone materials, which calls for a long-term monitoring and plans to reinforce the stone surfaces. But the main body including the pagoda roof stone needs washing on a regular basis, and the many different cracks should be fixed with glue by using the fillers or hardeners designed for stone cultural properties after removing the cement mortar. In case of the replacement of the stone materials with new stones, it's necessary to examine the pagoda for the center of gravity and support intensity of the materials. The structural stability of the pagoda can be attained by taking a reinforce measure in geotechnical engineering and making a drainage. The ground humidity, which has aggravated weathering and structural instability, should be resolved by setting up a humidity reduction facility. The contamination of lichens and bryophyte around the pagoda and on the surface is serious. Thus biochemical treatments should be given too in order to prevent further biological damages and remove the vegetation growing on the discontinuous planes.

• Journal of the Korean Society of Food Science and Nutrition
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• v.31 no.2
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• pp.216-220
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• 2002

The microbiological examinations of food service operations were conducted for the hygienic evaluation at four elementary schools in Busan, Korea. Total one hundred and seventy two swabbed samples using sponge were collected from the surface of environments, utensils and equipments of food service facilities and analyzed by measuring the total, coliform and psychrotrophic count. Sampling sites were the surfaces of floors, drains, walls, knives, cutting boards, rubber gloves, vinyl aprons, plastic containers, carriers, shelves, trays, dry shelves, electric tray dryer, food containers, soup containers, rice cookers, frying pans, boiling cookers, refrigerators, dumb waiters and dishwashers. The swabbed samples kept in an ice-parked box were transported to a laboratory and analyzed. The results demonstrated that the degree of contamination depended on the sampling sites. Averages of total counts of surface swab samples were ranged from 0.62 to 7.79 Log CFU/200 cm$^2$. The level of coliforms were ranged from not detectable to 5.26 Log CFU/200 cm$^2$, and those of psychrotrophs from not detectable to 6.15 Log CFU/200 cm$^2$. The severely contaminated sites were dumb waiters, drains, rice cookers, knives, plastic containers and floors. Also cutting boards, rubber gloves, carriers, drying shelves, vinyl aprons, boiling cookers, soup containers, frying pans and refrigerators were highly contaminated with the level of abode 3.5 Log CFU/200 cm$^2$. Therefore, those sites should be focused and controlled according to control points of sanitation standard operating procedures (SSOP). Also, periodic microbiological examination in addition to visual examination is recommended on these highly contaminated sites indicated above results at food service operations in elementary school.

• Journal of the korean academy of Pediatric Dentistry
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• v.24 no.4
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• pp.763-770
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• 1997

The air abrasive technique is a non-mechanical method by which teeth are treated before restoration and stains and calculi are removed from tooth surfaces using the kinetic energy of small particles. The air abrasive technique in dentistry was first introduced in the 1950's with as instrument called 'Airdent'. But, as the main restorative materials of the period were amalgam and gold, and the instrument's inability to control the flow of particles caused the particles to be spread throughout the clinics, widespread use was not possible. In the 1990's, as these techincal problems were solved and more interest in new restorative materials rose in an effort to preserve sound tooth structure, new developements took place in instruments related to the air abrasive technique. The air abrasive technique produces less pressure, vibration and heat that might cause patient discomfort and facilitates the preservation of sound tooth structure. It also reduces the need for anesthesia and is less harmful to the pulp. Other advantages include increase in dentin bonding strength of composite resin, lower possibility of saliva contamination and maintenance of a dry field. But there is not direct contact between the nozzle and the tooth, the operator cannot use his or her tactile sense and must rely solely upon visual input. Other disadvantages are: the tooth preparation depends on the operator's ability; alpha-alumina particles, after bouncing off the tooth surface, cause damage to dental mirrors; the equipment is expensive and takes up a certain amount of space in the clinic. The author conducted case report using the air abrasive technique on patient visiting the Department of Pediatric Dentistry at Seoul National University Dental Hospital and arrived at the following conclusions. 1. The tooth preparation capability of different air abrasive devices varied widely among manufacturers. 2. It was more effective in treating early caries lesions and stains compared to lesions where caries had already progressed to produce soft dentin. 3. The cold stream and noise caused by the evacuation system was a major cause of discomfort to pediatric patients. 4. As there is no direct contact with tooth surface when using the air abrasive technique for tooth preparation, considerable experience and skill is required for proper tooth preparation.

• Journal of Adhesion and Interface
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• v.16 no.4
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• pp.137-145
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• 2015

This study aimed to develop epoxy putty as a multi-purpose connection and restoration material that can be used for material-specific restoration work such as metal, wood, ceramics, earthenware and stone artifacts by replacing synthetic resins currently being used for preservation treatment of cultural assets. Existing synthetic resins have the issue of cutting force resulting from high strength, deflection resulting from long hardening time, contaminating the surface of artifacts through staining on tools or gloves and need for re-treatment resulting from material discoloration. Accordingly, paste type restoration material most widely being used in the field of cultural assets preservation treatment was selected and examined the property to select it as an object of comparison. Based on such process, epoxy putty was developed according to the kind of agent, hardener and filler. For the purpose of solving the issues of existing material and allowing the epoxy putty developed to have similar property, property experiments were conducted by selecting agents and hardeners with different characteristics and conditions. The study findings showed that both kinds are paste type that improved work convenience and deflection issue as a result of their work time of within 5~10 minutes that are about 3~10 times shorter than that of existing material. In regards to wear rate for increasing cutting force, it improved by about 3 times, thereby allowing easy molding. For the purpose of improving the issue of surface contamination that occurs during work process, talc and micro-ballon were added as filler to reduce the issue of stickiness and staining on hand. Furthermore, a multi-purpose restoration material with low shrinkage, low discoloration and high cutting force was developed with excellent coloring, lightweight and cutting force features.

• Korean Journal of Soil Science and Fertilizer
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• v.43 no.1
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• pp.51-59
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• 2010

The sediments and soils around a mine are likely to be exposed to contamination of arsenic (As) through mining operations. In this study, the factors associated with As movement in soils around a closed zinc (Zn) mine were evaluated by the relationship of As distributions to physico-chemical properties of soils. A sequential extraction scheme, based on a soil P fractionation, was used to assess the As distributionsin solid phases. A significant difference in As distributions was found between paddy and upland soils. While As contents of paddy soils increased with soil depth, those of upland soils decreased with soil depth. In upland soils, As showed additional significant relationships to oxides of Si, Al and Fe. Although a major fraction of As in soils was found to be in the NaOH extractable fraction, As exhibited highly significant relationship to the Zn species that apparently originated from the mine. Therefore, As mobility around Zn mine seems to be governed by mass flow of the particulates containing As-associated Zn in paddy soils, whereas retention reactions such as adsorption, complexation, and precipitation seem to predominate in upland soils.

• Journal of Korean Society on Water Environment
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• v.23 no.2
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• pp.201-205
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• 2007

This paper reports the amount of $^{222}Rn$ and $^{238}U$ in 18 sites of ground water and 30 sites of surface water. The instrument used to count $^{222}Rn$ activity was the liquid scintillation counter (LSC) which could resolute ${\alpha}$ and ${\beta}$ radiations. And $^{238}U$ was analyzed by the inductively coupled plasma (ICP). Radon and Uranium were not detected in raw and treated water which were sampled in a water treatment plant. However, radon ($^{222}Rn$) was high concentration in ground water from Jeon-la, Gang-won. So was uranium ($^{238}U$) in case of ground water from Gang-won, Choong-chung. Radon ($^{222}Rn$) activities were detected less than 15 pCi/L at 5 sampling points, 15~300 pCi/L at 7 sampling points, 300~4000 pCi/L at 6 sampling points. However, Radon ($^{222}Rn$) activities of all ground water samples were less than 4,000 pCi/L, which was bellow American Alternative Maximum Contamination Level (AMCL). Uranium ($^{238}U$) concentrations were less than $0.1{\mu}g/L$ at 5 sampling points, from $0.1{\mu}g/L$ to $20{\mu}g/L$ at 13 sampling points. Uranium was not detected in about 30% of the whole samples, but the concentration ranged from relatively low to high concentrations depending on the sampling point. The minimum detectable activity (MDA) of radon was 15 pCi/L. and the detection limit of uranium was $0.1{\mu}g/L$.

• Korean Journal of Soil Science and Fertilizer
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• v.18 no.4
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• pp.336-347
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• 1985

Soils and rice plants subject to smoke from the Jang-hang Smelter were samples at two depths to assess the nature and extend of Cd, Cu, Pb, and Zn contamination, particularly with respect to distance from pollution source. Soils at east site within 1km of the center of the smelter were highly contaminated with Cd, Cu, Pb, and Zn. Metal levels in the smoke-polluted area were higher in surface soil than in subsurface soil, and decreased rapidly with distance reaching nearly background levels at 5km from pollution source. A position correlation was found between contents of total and 0.1 N HCl-extractable, or 1.0N $CH_3COONH_4$- extractable heavy metals in surface soils of pollution. Contents of heavy metals in soils were positively correlated with soil organic matter and cation exchange capacity. The contents of heavy metals in brown rice collected from the paddy field around the Jang-hang Smelter were in the range of 0.23-1.33 ppm for Cd, 2.39-6.25 for Cu, 0.95-8.32 ppm for Pb and 14.60-27.31 for Zn. The contents of Cd, Cu, and Zn in rice straw were positively correlated with those in the brown rice. Negative correlation was found between the contents of Cd, Cu, Pb, and Zn in brown rice and the distance from the source.