• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.266-270
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• 2018

원자력 방사능 폐기물 또는 원자력 발전소 해체시 발생 가능한 세슘 이온은 인체뿐만 아니라 생태계 환경에도 큰 악영향을 미친다고 알려져 있다. 이러한 세슘 이온은 자연 속으로 손쉽게 스며들어 발생한 지역뿐만 아니라 쉽게 퍼지게 되어 넓은 지역까지 피해를 주게 되며, 반감기가 30년으로써 한번 자연계에 누출되면 장시간 잔존하여 인간 및 생태계에 악영향을 미치게 된다. 세슘이온이 몸속에 들어오게 되면 장에서 몸으로 100% 흡수되며 내장에 축척되어 연조직 전체에 분포하게 되며 갑상선 암과 같은 심각한 위험에 초래하게 된다. 2011년 발생한 후쿠시마 원전 사고 이후 국내에서도 많은 관심을 가지기 시작하였으며, 따라서 수중의 세슘이온을 제거하기 위하여 나노 입자 형태의 기능성을 가진 물질들을 적용한 많은 연구가 이루어지고 있다. 이러한 나노물질들은 수중의 세슘이온 제거에 대하여 우수한 제거효율을 보여주고 있으나 나노 입자 특성상 사용 이후 회수가 어려워 기능성 물질들의 확산 및 축적에 따른 2차 환경오염의 문제점까지 발생하게 된다. 최근 수처리 분야에서 외부 자기장을 주게 되면 자성을 띄게 되는 물질인 자성체에 대한 관심이 급등하고 있다. 이러한 자성체들은 수중에서 별도의 회수 시스템 없이 자성으로 인하여 완벽히 자기분리 된다. 세슘제거에 탁월한 기능성 물질과 완벽한 자기분리가 가능한 자성체를 결합하여 특별한 회수장치 없이 외부 자기장만 주어진다면 수중의 세슘을 효과적으로 제거 또는 처리할 수 있다. 자성체 입자 표면에 흡착제인 프러시안 블루나 제올라이트와 같은 흡착제를 합성하여 수중의 세슘을 제거하는 연구가 활발히 이루어지고 있다. 그러나 기존의 자성체보다 좀 더 높은 자성을 가지고 있으며 외부 자기장에 의해 강하게 반응을 한다고 알려져 있는 강자성체(Ferromagnetic)를 사용하게 된다면 흡착제와 결합 이후 더욱더 강한 자성을 가진 흡착제가 탄생하며 이를 사용하면 높은 처리율뿐만 아니라 높은 슬러지 회수율을 가질 수 있다. 따라서 본 연구는 흡착제나 이온교환수지와 같은 기능성 물질을 사용하여 수중의 세슘을 제거하는 메커니즘과 강자성체가 가지고 있는 강한 자성의 성질을 결합한 복합체 제조에 대한 연구조사를 중점적으로 실시하였다. 본 연구에 의해 연구 조사된 결과를 바탕으로 수중의 세슘 이온에 대하여 높은 제거효율과 회수율을 가지는 새로운 형태의 복합체 제조에 관한 정보를 제공하고자 한다.

• Journal of the Korean Society of Safety
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• v.37 no.6
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• pp.166-173
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• 2022

A variety of input parameters are taken into consideration while performing a Level 3 PSA. Some parameters related to plume segments, spatial grids, and particle size distribution have flexible input formats. Fine modeling performed by splitting a number of segments or grids may enhance the accuracy of analysis but is time-consuming. Analysis speed is highly important because a considerably large number of calculations is required to handle Level 2 PSA scenarios for a single-unit or multi-unit Level 3 PSA. This study developed a sensitivity analysis supporting interface called MACCSsense to compare the results of the trials of plume segmentation with the results of the base case to determine its impact (in terms of time and accuracy) and to support the development of a modeling approach, which saves calculation time and improves accuracy. MACCSense is an automation tool that uses a large amount of plume segmentation analysis results obtained from MUST Converter and Mr. Manager developed by KAERI to generate a sensitivity report that includes impact (time and accuracy) by comparing them with the base-case result. In this study, various plume segmentation approaches were investigated, and both the accuracy and speed of offsite consequence analysis were evaluated using MACCS as a consequence analysis tool. A simultaneous evaluation revealed that execution time can be reduced using multi-threading. In addition, this study can serve as a framework for the development of a modeling strategy for plume segmentation in order to perform accurate and fast offsite consequence analyses.

• Economic and Environmental Geology
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• v.51 no.2
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• pp.99-111
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• 2018

In this study three target radionuclides ($^{60}Co$, $^{137}Cs$, and $^{125}Sb$) were reacted with solid samples collected from the nuclear facility sites to investigate their sorption and mobility behaviors for preparing unexpected nuclear accidents. The highest sorption distribution coefficients ($K_{ds}$) of target radionuclides ($^{60}Co=947mL/g$, $^{137}Cs=2105mL/g$, $^{125}Sb=81.3mL/g$) were found in topsoil layer under groundwater condition, and the $K_d$ values of three radionuclides decreased in the order of fractured rock and bedrock samples under the same groundwater condition. High $K_d$ values of $^{60}Co$ in topsoil layer and fracture rock resulted from the clay minerals present, and the $K_d$ values decreased 58-69 % under seawater condition due to high ionic strength. $^{137}Cs$ sorption was controlled by the ion exchange reaction with $K^+$ on flayed edge sites (FES) of mica. The $^{137}Cs$ sorption was the most affected by seawater (89-97 % decrease), while $^{125}Sb$ sorption was not much affected by seawater. As the results of column and batch experiments, the retardation factors (R) of $^{137}Cs$, $^{60}Co$, and $^{125}Sb$ were determined about 5400-7400, 2000-2500, and 250-415, respectively, indicating no significant transport for these radionuclides even in fractured zone with groundwater. These results suggest that even in the case of severe nuclear accident at the nuclear facilities the mobility of released radionuclides ($^{60}Co$, $^{137}Cs$, and $^{125}Sb$) can be significantly retarded by the topsoil layer and fractured rock. In addition, the results of this study will be used for the safety and environmental performance assessment of nuclear facilities.

• Journal of Radiation Protection and Research
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• v.39 no.1
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• pp.46-53
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• 2014

For the case of radiation emergency, it is required to assess internal contamination of the public, including children as well as adults. The objective of the present study was to assess counting efficiency of a whole body counter by human body size and standing position of the measurement person. In this study, the FASTSCAN whole body counter used at National Radiation Emergency Medical Center of Korean Institute of Radiological and Medical Science was simulated by a radiation transport computer code. The simulation results of the counting efficiencies agreed well with measurements within the 2% of discrepancy for 4-year child and 5% for adults. The standing positions of the people were adjusted by body size to find the consistent trend of the counting efficiencies by human body size. Body size scaling factors of the whole body counter were derived to consider human body size and improve the measurement accuracy. The counting efficiency assessment methodology in this study can be successively used to improve the measurement accuracy when using a whole body counter for the case of radiation emergency.

• Korean Security Journal
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• no.10
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• pp.387-407
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• 2005

Thanks to the developments of IT technologies, such critical infrastructures as fundamental structures of energies, material circulations, monetary circulations, and living necessaries are intertwined as well as mutually dependent. In this respect, the fact that national infrastructures are closely related to IT infrastructures implies not only expected benefits to provide diverse information-based services, but also anticipated costs to bring about new dangers. However, in spite of these threats, traditional researchers have not put enough interests in these indirect danger, which yield the damages in broad areas through paralyzing risk management systems, although they have investigated such direct threats as nuclear accidents, conflagrations, traffic troubles, and gasoline accidents. Considering that the tendency to depend on electricity, so-called electrification, which is caused by automation and informationalization, is intensified in all parts of society, the breakout problem as a factor to inhibit securities in information-oriented society is significant. Thus, the problems of large-scale power blackout should be treated as national crises. Also, preparation systems for large-scale power blackout have to be provided quickly. In this paper, with analyzing various cases of large-scale power blackout and investigation the causes of them, researches on the blackout management systems of Korea are to be present, on the basis of national crisis management states which are comprised of protection (mitigating and preparing), responding, and recovering(rewarding).

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.15 no.4
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• pp.391-402
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• 2017

The Korea Radioactive Waste Agency (KORAD) has developed a concrete cask for the dry storage of spent nuclear fuel that has been generated by domestic light-water reactors. During long-term storage of spent nuclear fuel in concrete casks kept in dry conditions, the integrity of the concrete cask and spent nuclear fuel must be maintained. In addition, the radiation dose rate must not exceed the storage facility's design standards. A suitable shielding design for radiation protection must be in place for the dry storage facilities of spent nuclear fuel under normal and accident conditions. Evaluation results show that the appropriate distance to the annual dose rate of 0.25 mSv for ordinary citizens is approximately 230 m. For a $2{\times}10$ arrangement within storage facilities, rollover accidents are assumed to have occurred while transferring one additional storage cask, with the bottom of the cask facing the controlled area boundary. The dose rates of 12.81 and 1.28 mSv were calculated at 100 m and 230 m from the outermost cask in the $2{\times}10$ arrangement. Therefore, a spent nuclear fuel concrete cask and storage facilities maintain radiological safety if the distance to the appropriately assessed controlled area boundary is ensured. In the future, the results of this study will be useful for the design and operation of nuclear power plant on-site storage or intermediate storage facilities based on the spent fuel management strategy.

• Journal of the Korea Convergence Society
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• v.3 no.1
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• pp.27-34
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• 2012

After Fukushima Nuclear Accident on Mar11, 2011, to grasp the thought of university students in Korea on radiation and medical radiation and seek for the right mass communication on the radiation safety of the people and the proper teaching method on radiation, 790 questionnaires from the universities which had a four-year department of radiological science in 5 provinces(Gyeonggi, Gangwon, Chungcheong, Jeolla, and Gyeongsang-do) all over the country were collected and analyzed. The questionnaire was composed of 36 items, and it was analyzed that one of the important causes that made them feel that radiation was dangerous was 'even if they were exposed to the small quantity of radiation, they could have trouble later.' ($3.28{\pm}1.05$). In the item of the control of radiation, there were the respondents who answered that the government should take action rather than an individual($3.87{\pm}0.89$). In the item of 'Fukushima Nuclear Accident made me think that 'We should not keep nuclear power generation', the result was $2.79{\pm}0.95$. In the item of 'My thought on the medical radiation has negatively changed since Fukushima Nuclear Accident', the students who hadn't taken the course related with radiation showed a negative thought on the medical radiation, such as, there was $2.64{\pm}1.02$ as a whole, $2.31{\pm}1.00$ in department of radiological science, $2.94{\pm}0.95$ in department of dental hygiene, and $3.13{\pm}0.82$ in other departments. And also, those who thought that the education of radiation was necessary were 82.28%, and T.V or Internet was thought as the most effective teaching method.

• Journal of Radiation Protection and Research
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• v.30 no.3
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• pp.99-105
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• 2005

A model for evaluating radioactive contamination in the urban environment, named METRO-K, was developed as a basic step for accident consequence analysis in case of an accidental release. The three kind of radionuclides $(^{137}Cs,\;^{106}Ru,\;^{131}I)$ and the different chemical forms of iodine (particulate, organic and elemental forms) are considered in the model. The radioactive concentrations are evaluated for the five types of surface (roof, paved road, wall, lawn/soil, tree) as a function of time. Using the model, the contaminative impacts of the surfaces were intensively investigated with respect to with and without precipitation during the measurement periods of radionuclides in air. In addition, a practical application study was conducted using $^{137}Cs$ concentration in air and precipitation measured in an European country at the Chernobyl accident. As a result precipitation was an influential factor in surface contamination. The degree of contamination was strongly dependent on the types of radionuclide and surface. Precipitation was more influential in contamination of $^{137}Cs$ than that of $^{131}I$ (elemental form).

• Journal of Radiation Protection and Research
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• v.40 no.4
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• pp.244-251
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• 2015

The containment filtered venting system reduces the range of the contamination area around the nuclear power plant by strengthening the integrity of the containment building. In this study, the probabilistic assessment code MACCS2 was used to assess the effect of the CFVS to off-site. The accident source term was selected from a Probabilistic Safety Analysis report of SHINKORI 1&2 Nuclear Power Plant. The three source term categories from 19 STC were chosen to evaluate the effective dose and thyroid dose of residents around the power plant and the dose with CFVS and without CFVS were compared. The dose was calculated according to the distance from the nuclear power plant, so the damage scale based on the distance that exceeds the IAEA criteria for effective dose (100 mSv per 7 days) and thyroid dose (50 mSv per 7 days) were compared. The effective dose reduction rates of the STC-3, STC-4, STC-6 were about 95-99% in the whole range (0~35 km), 96-98% for the thyroid dose. There are similar results between effective dose and thyroid dose. After applying the CFVS, the damage scale that exceeds the effective dose criteria was about 1 km (mean). Especially, the STC-4 damage scale was decreased from 26 km (mean) to 1.2 km (mean) significantly. The damage scale that exceed the thyroid dose criteria was decreased to 2~3 km (mean). The STC-4 damage scale was also decreased significantly as compared to STC-3, STC-6 in terms of effective dose.

• Journal of Radiation Protection and Research
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• v.39 no.2
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• pp.109-117
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• 2014

Nuclear emergency planning is to plan sheltering, evacuation and iodine prophylaxis for the residents living in the area where the emergency plan is needed, the area is confirmed based on the dose assessment using the source-term through an accident analysis and the data measured from meteorological tower. In this study, the does change before and after protective measures was assessed stochastically based on the one year meteorological data in the condition of the maximum hypothetical accident which can be considered at the research reactor 'HANARO', and the optimized protective measures were derived based on the reference levels defined as a residual dose by ICRP 2007 recommendation which can be applied in a emergency exposure situation. The optimized protective measures for the HANARO in the maximum hypothetical accident were the evacuation to radius 300 m, the sheltering from 300 m to 800 m, the iodine prophylaxis only for the emergency workers under the protective measures for non emergency workers.