• 한국지하수토양환경학회지:지하수토양환경
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• 제25권2_spc호
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• pp.86-100
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• 2020

Analyzing and monitoring environmental contaminants based on geophysical exploration techniques have become important and it is now widely applied to delineate spatial distribution geophysical characteristics in wide area. Among the techniques, induced polarization (IP) method, which measures polarization effects on electrical potential distribution, has drawn much attention as an effective tool for environmental monitoring since IP is sensitive to changes in biochemical reactions. However, various reactions stemming from the presence of multiple contaminants have greatly enhanced heterogeneity of polluted sites to result in highly variable electrical characteristics of the site. Those contaminants influence chemical and physical state of soil and groundwater to alter electrical double layer, which in turn influences polarization of the media. Since biochemical reactions between microbes and contaminants result in various IP effects, IP laboratory experiments were conducted to investigate IP responses of the contaminated soil samples under various conditions. Field IP surveys can delineate the spatial distribution of contamination, while providing additional information about electrical properties of a target medium, together with DC resistivity. Reviewing IP effects of contaminants as well as IP surveys can serve as a good starting point for the application of IP survey in site assessment for environmental remediation.

• 한국지하수토양환경학회지:지하수토양환경
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• 제24권5호
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• pp.11-16
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• 2019

In this study, a reliable number of soil samples for TPH fractionation was investigated in order to perform risk assessment. TPH was fractionated into volatile petroleum hydrocarbons (VPH) with three subgroups and extractable petroleum hydrocarbons (EPH) with four subgroups. At the study site, concentrations of each fraction were determined at 18 sampling points, and the 95% upper confidence limit (UCL) value was used as an exposure concentration of each fraction. And then, 5 sampling points were randomly selected out of the 18 points, and an exposure concentration was calculated. This process was repeated 30 times, and the results were compared statistically. Exposure concentrations of EPH obtained from 18 points were 99.9, 339.1, 27.3, and 85.9 mg/kg for aliphatic $C_9-C_{18}$, $C_{19}-C_{36}$, $C_{37}-C_{40}$, and aromatic $C_{11}-C_{22}$, respectively. The corresponding exposure concentrations obtained from 5 points were 139.8, 462.8, 35.1 and 119.4 mg/kg, which were significantly higher than those from 18 points results (p <0.05). Our results suggest that limited number of samples for TPH fractionation may bias estimation of exposure concentration of TPH fractions. Also, it is recommended that more than 30 samples need to be analyzed for TPH fractionation in performing risk assessment.

• Journal of Radiation Protection and Research
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• 제46권1호
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• pp.24-31
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• 2021

Decommissioning efforts are underway at the reactor where the accident occurred, namely the damaged Tokyo Electric Power Company (TEPCO) Fukushima Daiichi Nuclear Power Plant (FDNPP). However, a large amount of groundwater flowing into the site has become contaminated with radioactive substances and is stored in tanks on site, which has hampered the decommissioning work. Although the inflow of groundwater has been greatly reduced through measures such as the construction of frost walls, approximately 170 ㎥ of water treated by the Advanced Liquid Processing System (ALPS) is being stored in tanks, each day. The tanks used to store this treated water are expected to become full by around the summer of 2022. It is not easy to get people to understand the efforts of all concerned parties, and providing clear information to these concerned parties is also a challenge. Questions have also been raised regarding whether other alternatives have been fully explored in the ALPS subcommittee. Some people have commented that the answers to the questions raised regarding the biological effects of tritium transmutation are inadequate. Some suspect that the answers are too detailed and incomprehensible, and that the respondents may be manipulating the public with some malicious intent. In any case, each possible plan presents both advantages and disadvantages, depending on the people who are involved. That makes it an ethical and vexing issue that can sway decisions, as perspectives change. While the environmental release plan is scientifically safe, it may represent a painful alternative. On the other hand, a more careful and imaginative approach to the idea of continued storage in tanks or other forms of storage may reveal some troublesome hidden disadvantages. Under these circumstances, experts must be prepared to answer people's questions in a comprehensive and robust manner.

• 방사성폐기물학회지
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• 제20권4호
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• pp.489-500
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• 2022

The decommissioning of nuclear facilities produces various types of radiologically contaminated waste. In addition, dismantlement activities, including cutting, packing, and clean-up at the facility site, result in secondary radioactive waste such as filters, resin, plastic, and clothing. Determining of the radionuclide content of this waste is an important step for the determination of a suitable management strategy including classification and disposal. In this work, we radiochemically characterized the radionuclide activities of filters used during the decommissioning of Korea Research Reactors (KRRs) 1 and 2. The results indicate that the filter samples contained mainly ³H (500-3,600 Bq·g^-1), ¹⁴C (7.5-29 Bq·g^-1), ⁵⁵Fe (1.1- 7.1 Bq·g^-1), ⁵⁹Ni (0.60-1.0 Bq·g^-1), ⁶⁰Co (0.74-70 Bq·g^-1), ⁶³Ni (0.60-94 Bq·g^-1), ⁹⁰Sr (0.25-5.0 Bq·g^-1), ¹³⁷Cs (0.64-8.7 Bq·g^-1), and ¹⁵²Eu (0.19-2.9) Bq·g^-1. In addition, the gross alpha radioactivity of the samples was measured to be between 0.32-1.1 Bq·g^-1. The radionuclide concentrations were below the concentration limit stated in the low- and intermediatelevel waste acceptance criteria of the Nuclear Safety and Security Commission, and used for the disposal of the KRRs waste drums to a repository site.

• Environmental Analysis Health and Toxicology
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• 제21권1호
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• pp.45-56
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• 2006

This study was conducted to investigate seasonal distributions of fine particles ($PM_{2.5}$) and associated polycyclic aromatic hydrocarbons (PAHs) at three cities. $PM_{2.5}$ samples were collected on glass fiber filters at urban (Chuncheon), metropolitan (Seoul), and industrial complex sites (Ulsan) from September, 2002 to February, 2004 using the Andersen FH 95 Particulate Sampler. About five 24-hour samples were collected from each site per season. The filters were analyzed for mass and six selected PAHs concentrations. $PM_{2.5}$ concentrations were the highest either in winter or spring, which could be attributed to the increase of fossil fuel combustion in winter or the transport of yellow sand to the Korean peninsula from China in spring, respectively. Regional $PM_{2.5}$ concentrations were higher in the order of Seoul>Chuncheon>Ulsan without statistical difference among cities. The filters were extracted using dichloromethane in an ultrasonicator and analyzed for six PAHs (anthracene, fluoranthene, pyrene, benzo[a]anthracene, chrysene, and benzo[a]pyrene) with HPLC. Total PAHs concentrations were statistically different among seasons in each site, and the highest concentrations were observed in winter at each sampling site. For total samples collected, the median total PAHs concentrations in Chuncheon ($4.6ng/m^3$) and Seoul ($4.4ng/m^3$) were approximately two times higher than that in Ulsan ($2.1ng/m^3$). Chrysene was a component found in the highest proportion among total PAHs at each site. Carcinogenic risks calculated based on the BaP toxic equivalency factors (TEFs) over the whole sampling period were higher in the order of Chuncheon>Seoul>Ulsan. This study suggests that the atmosphere of Chuncheon is contaminated with particulate matter and PAHs at the levels equivalent to those of Seoul and that an appropriate measure needs to be taken to mitigate human health risks from inhalation exposure to airborne fine particles.

• 한국지하수토양환경학회지:지하수토양환경
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• 제18권1호
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• pp.85-93
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• 2013

This study is conducted to evaluate the leaching of contaminants from mine tailing by natural water and finally to estimate the leaching and transportation of heavy metal contaminants by rainfall. In order to identify contaminated heavy metal of soil, 17 soil, 2 tailing and 2 waste dump and 2 control samples were taken at mine area and analyzed total metal contents. The leaching experiments were conducted using distilled water. Cu, Pb, Zn was extracted from the reddish mine tailing in a short period time, especially the extraction rate of Cu (45.0%) was highest. The contaminants were leached from the yellowish mine tailing within an hour and the leaching rate of Cd (42.0%) and Zn (17.2%) were relatively high. The reddish soil from the waste dump showed leaching of Cu (5.1%), Pb (4.0%) and Zn (3.3%), however the leaching rate was low except Mi (14.2%). From the yellowish soil sampled from the dumping site, the leaching of Cu (8.2%) and Ni (9.7%) was high while the leaching of Zn (0.2%) were relatively low.

• Advances in environmental research
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• 제2권3호
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• pp.167-177
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• 2013

We investigated that removal of aqueous U(VI) by nano-sized Zero Valent Iron (nZVI) and Fe(II) bearing minerals (controls) in this study. Iron particles showed different U(VI) removal efficiencies (Mackinawite: 99%, green rust: 95%, nZVI: 91%, magnetite: 87%, pyrite: 59%) due to their different PZC (Point of Zero Charge) values and surface areas. In addition, noticeable amount of surface Fe(II) (181 ${\mu}M$) was released from nZVI suspension in 6 h and it increased to 384 ${\mu}M$ in the presence of U(VI) due to ion-exchange of U(VI) with Fe(II) on nZVI surface. Analysis of Laser-Induced Breakdown Detection (LIBD) showed that breakdown probabilities in both filtrates by 20 and 200 nm sizes was almost 24% in nZVI suspension with U(VI), while 1% of the probabilities were observed in nZVI suspension without U(VI). It indicated that Fe(II) colloids in the range under 20 nm were generated during the interaction of U(VI) and nZVI. Our results suggest that Fe(II) colloids generated via ion-exchange process should be carefully concerned during long-term remediation site contaminated by U(VI) because U could be transported to remote area through the adsorption on Fe(II) colloids.

• 대한치과의사협회지
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• 제51권12호
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• pp.650-657
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• 2013

The aim of this study was to achieve healing of Peri-implantitis defects and hard tissue augmentation using a bovine-derived bone mineral on the defect site. Two patients were treated with the surgical approach. With a full muco-periosteal flap elevation, the implant surfaces were exposed and granulation tissue removed around the implant and between the threads. Each surface of the contaminated implant was prepared with the air-abrasive device(PerioFlow$^{(R)}$) for decontamination. Bovine-derived bone mineral(Bio-Oss collagen$^{(R)}$) was then used to fill the defects and muco-periosteal flaps sutured to achieve transmucosal healing. Radiographs and clinical photographs were taken before and after 6 months of healing and an estimate of bone fill was assessed. Within the limits of the present case report, a surgical approach in treatment of peri-implantitis defects using a collagen form of bovine bone mineral was visited. Although limited, the two cases showed the stability and biocompatibility of a bovine-derived bone mineral and effectiveness of air-abrasive device(PerioFlow$^{(R)}$) as a decontamination method.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.1116-1120
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• 2004

In the nuclear power plant, there are several cylindrical vessels such as reactor vessel, pressuriser and so on. The vessels are usually constructed by welding large rolled plates, forged sections or nozzle pipes together. In order to assure the integrity of the vessel, these welds should be periodically inspected using sensors such as ultrasonic transducer or visual cameras. This inspection is usually conducted under water to minimize exposure to the radioactively contaminated vessel walls. The inspections have been performed by using a conventional inspection machine with a big structural sturdy column, however, it is so huge and heavy that maintenance and handling of the machine are extremely difficult. It requires much effort to transport the system to the site and also requires continuous use of the utility's polar crane to move the manipulator into the building and then onto the vessel. Setup beside the vessel requires a large volume of work preparation area and several shifts to complete. In order to resolve these problems, we have developed an underwater mobile robot guided by the laser pointer, and performed a series of experiments both in the mockup and in the real reactor vessel. This paper introduces our robotic inspection system and the laser guidance of the mobile robot as well as the results of the functional test.

• 한국환경과학회지
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• 제17권1호
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• pp.29-36
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• 2008

A large amount of $2.1{\times}10^6m^3$ of polluted sediment was dredged from the Masan Bay and deposited in Gapo confined area, Masan, Korea. The six representative sediments were obtained and analyzed for issue components. The data was discussed with the species of benthos and their distribution. It was judged that toxicological effects of sediment analyzed ranged from ERL to ERM with copper and zinc, and ERL with cadmium, chrome, lead and nickel by the Adverse Biological Effects. The dredging index (DI) of sediments stabilized for 10 years since dumping the confined site was calculated and compared with the DI values of dredged sediment itself. DI values decreased from 0.67 to $0.07{\sim}0.18$, which reflects DI value less than 0.2 is good for benthos in the sediment by the natural recovery of dredged materials. The ecological recovery was confirmed in this confined area as a habitat of benthic organisms.