• 한국안전학회지
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• 제33권6호
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• pp.144-156
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• 2018

Level 3 Probabilistic Safety Assessment (PSA) is performed for the risk assessment that calculates radioactive material dispersion to the environment. This risk assessment is performed with a tool of MELCOR Accident Consequence Code System (MACCS2 or WinMACCS). For the off-site consequence analysis of multi-unit nuclear power plant (NPP) accident, the single location (Center Of Mass, COM) method has been usually adopted with the assumption that all the NPPs in the nuclear site are located at the same COM point. It was well known that this COM calculation can lead to underestimated or overestimated radionuclide concentration. In order to overcome this underestimation or overestimation of radionuclide concentrations in the COM method, Multiple Location (ML) method was developed in this study. The radionuclide concentrations for the individual NPPs are separately calculated, and they are summed at every location in the nuclear site by the post-processing of radionuclide concentrations that is based on two-dimensional Gaussian Plume equations. In order to demonstrate the efficiency of the ML method, radionuclide concentrations were calculated for the six-unit NPP site, radionuclide concentrations of the ML method were compared with those by COM method. This comparison was performed for conditions of constant weather, yearly weather in Korea, and four seasons, and the results were discussed. This new ML method (1) improves accuracy of radionuclide concentrations when multi-unit NPP accident occurs, (2) calculates realistic atmospheric dispersion of radionuclides under various weather conditions, and finally (3) supports off-site emergency plan optimization. It is recommended that this new method be applied to the risk assessment of multi-unit NPP accident. This new method drastically improves the accuracy of radionuclide concentrations at the locations adjacent to or very close to NPPs. This ML method has a great strength over the COM method when people live near nuclear site, since it provides accurate radionuclide concentrations or radiation doses.

• 한국방사성폐기물학회:학술대회논문집
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• 한국방사성폐기물학회 2018년도 추계학술논문요약집
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• pp.379-379
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• 2018

MXenes are a new family of 2D transition metal carbide nanosheets analogous to graphene (Lv et al., 2017; Sun et al., 2018). Due to the easy availability, hydrophilic behavior, and tunable chemistry of MXenes, their use in applications for environmental pollution remediation such as heavy metal adsorption has recently been explored (Li et al., 2017). In this study, three-dimensional (3D) MXene ($Ti_3C_2T_x$) films with high adsorption capacity, good mechanical strength, and high selectivity for specific radionuclide from aquose solution were successfully fabricated by a polymeric precursor method using vacuum-assisted filtration. The highest removal efficiency on the films was 99.54%, 95.61%, and 82.79% for $Sr^{2+}$, $Co^{2+}$, and $Cs^+$, respectively, using a film dosage of 0.06 g/ L in the initial radionuclide solution (each radionuclide concentration = 1 mg/L and pH = 7.0). Especially, the adsorption process reached an equilibrium within 30 min. The expanded interlayer spacing of $Ti_3C_2T_x$ sheets in MXene films showed excellent radionuclide selectivity ($Cs^+$ and/or $Sr^{2+}/Co^{2+}$) (Simon, 2017). Besides, the MXene films was not only able to be easily retrieved from an aqueous solution by filtration after decontamination processes, but also to selectively separate desired target radionuclides in the solutions. Therefore, the newly developed MXene ($Ti_3C_2T_x$) films has a great potential for radionuclide removal from aqueous solution.

• Nuclear Engineering and Technology
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• 제53권1호
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• pp.253-257
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• 2021

This work demonstrates the use of baromembrane method based on reverse osmosis (RO) process. The method is realized on mobile complex, which allows to concentrate and determine ultra-low activity of radionuclides in water cooling ponds of Russian nuclear fuel cycle enterprises. The existence level of radionuclide background creates difficult conditions for identification the contribution of liquid discharges enterprise, as standard monitoring methods have a very high detection level for radionuclides. Traditional methods for determining the background radionuclides concentrations require the selection of at least 500 liters (l) of water, followed by their evaporation to form a dry residue. This procedure with RO membranes requires at least 5 days. It is possible to reduce the time and energy spent on evaporation of hundreds of water liters by pre-concentrating radionuclides in a smaller sample volume with baromembrane method. This approach allows preliminary concentration of water samples from 500 l volume till 20 l volume during several hours. This approach is universal for the concentration of dissolved salts of any heavy metals, other organic compounds and allows the preparation of water countable samples in much shorter time compared to the traditional evaporation method.

• 한국방사성폐기물학회:학술대회논문집
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• 한국방사성폐기물학회 2004년도 학술논문집
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• pp.228-228
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• 2004

Nuclear Environment Technology Institute (KHNP-NETEC) developed the conceptual design of the low and intermediate-level radioactive waste (LILW) repository. Among many engineering challenges, it is of particular importance to find out an optimum arrangement of near-surface disposal vaults in the repository area to minimize the radionuclide flux and concentration at the interface between the geo-sphere and bio-sphere. (omitted)

• Nuclear Engineering and Technology
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• 제42권5호
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• pp.562-567
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• 2010

A One-Dimensional Water Flow and Contaminant Transport in Unsaturated Zone (FTUNS) code has been developed in order to interpret radionuclide migration in an unsaturated zone. The pore-size distribution index (n) and the inverse of the air-entry value ($\alpha$) for an unsaturated zone were measured by KS M ISO 11275 method. The hydraulic parameters of the unsaturated soil are investigated by using soil from around a nuclear facility in Korea. The effect of hydraulic parameters on radionuclide migration in an unsaturated zone has been analyzed. The higher the value of the n-factor, the more the cobalt concentration was condensed. The larger the value of $\alpha$-factor, the faster the migration of cobalt was and the more aggregative the cobalt concentration was. Also, it was found that an effect on contaminant migration due to the pore-size distribution index (n) and the inverse of the air-entry value ($\alpha$) was minute. Meanwhile, migrations of cobalt and cesium are in inverse proportion to the Freundich isotherm coefficient. That is to say, the migration velocity of cobalt was about 8.35 times that of cesium. It was conclusively demonstrated that the Freundich isotherm coefficient was the most important factor for contaminant migration.

• Journal of Radiation Protection and Research
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• 제30권4호
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• pp.167-174
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• 2005

The concentrations of natural and artificial radionuclides in soil and gamma ray dose rate in air at 233 locations in Korea have been determined. The national mean concentrations of $^{232}Th,\;^{226}Ra,\;^{40}K,\;^{137}Cs\;and\;^{90}Sr$ in soil were $60{\pm}31,\;33{\pm}14,\;673{\pm}238,\;35{\pm}9.3\;and\;5.0{\pm}3.4\;Bq\;kg^{-1}$, respectively. The mean gamma-ray dose rate at 1 m above the ground was $7918\;nGy\;h^{-1}$. $^{137}Cs$ concentration had highly significant correlation with organic matter content and cation exchange capacity. $^{90}Sr$ concentration had slightly coherent with pH. The results have been compared with other global radioactivity and radiation measurements.

• Nuclear Engineering and Technology
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• 제35권5호
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• pp.387-398
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• 2003

For reference human intrusion scenarios constructed in previous study, a probabilistic safety assessment to derive the radionuclide concentration limits for the low- and intermediate- level radioactive waste disposal facility is conducted. Statistical approach by the Latin Hypercube Sampling method is introduced and new assumptions about the disposal facility system are examined and discussed. In our previous study of deterministic approach, the post construction scenarios appeared as most limiting scenario to derive the radionuclide concentration limits. Whereas, in this statistical approach, the post drilling and the post construction scenarios are mutually competing for the scenario selection according to which radionuclides are more important in safety assessment context. Introduction of new assumption shows that the post drilling scenario can play an important role as the limiting scenario instead of the post-construction scenario. When we compare the concentration limits between the previous and this study, concentrations of radionuclides such as Nb-94, Cs-137 and alpha-emitting radionuclides show elevated values than the case of the previous study. Remaining radionuclides such as Sr-90, Tc-99 I-129, Ni-59 and Ni-63 show lower values than the case of the previous study.

• 방사성폐기물학회지
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• 제8권2호
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• pp.123-133
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• 2010

방사성핵종의 분포유형에 관한 정보에 기초하여 극저준위폐기물의 자체처분 적합성을 통계학적으로 해석할 수 있는 방법론을 개발하였다. 방사성핵종의 분포에 관한 정보를 알 수 없는 경우에 대해서는 널리 알려진 마코프 부등식과 체비셰프 부등식을 적용하여 방사능농도의 산술평균과 허용되는 최대 표준편차의 상관관계식을 제시하였고, 방사성핵종의 농도가 정규분포 또는 로그정규분포를 갖는 경우에 대해서는 확률밀도함수, 누적확률밀도함수 등의 통계학적 관계식을 이용하여 방사능농도의 산술평균과 허용되는 최대 표준편차의 상관관계식을 새롭게 유도하였다. 또한, 자체처분기준 100 Bq/g 및 신뢰수준 95%인 조건에 대한 사례 적용연구를 통하여 방사능농도의 산술평균과 허용되는 표준편차의 범위를 방사성핵종의 분포유형에 따라 정량적으로 비교 제시하고, 자체처분 대상 폐기물의 방사성핵종 분포유형에 관한 정보가 확보될 경우 동일한 신뢰수준에서 자체처분이 허용될 수 있는 범위가 확장될 수 있음을 통계학적으로 입증하였다.

• Journal of Radiation Protection and Research
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• 제22권3호
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• pp.183-193
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• 1997

원전 작업자 피폭관리와 안전성 평가 및 최종적으로 처분허가를 위하여 폐기물 내의 핵종 및 농도를 파악하여야만 한다. 이온교환 수지 및 필터는 그 부피는 작으나 원전 운전중 발생하는 폐기물 내 방사능의 대부분을 차지하고 있다. 본 연구의 목적은 냉각수 정화 계통내의 수지 및 필터 내에 누적되어 있는 방사성 핵종의 양을 예측할 수 있는 방법을 개발하는 것이다. 핵종누적량을 계산하기 위하여 평균제염계수 대신 순간제염계수를 사용하였으며 포트란언어를 사용하여 프로그램을 작성하여 누적량을 계산하였다. 본 예측기법의 검증을 위하여 미국 Rancho-Seco 발전소의 측정자료를 이용하였으며 실험을 통한 계측자료를 검증에 이용하였다. 순간제염계수를 이용한 본 방법의 계산이 평균제염계수를 이용한 것보다 오차가 작았다. 이 방법을 실제 적용하기 위해서는 운전지침에 의하여 주기적으로 계측한 제염제수와 핵종농도 자료만으로도 핵종누적량 계산이 가능하다. 그러나, 특히 발전소 운전상황이 급격하게 변할 때에는, 정확한 누적량 평가를 위하여 제염계수 및 방사성 핵종농도의 측정주기가 짧아져야 한다.

• Nuclear Engineering and Technology
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• 제52권6호
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• pp.1289-1296
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• 2020

The estimation of radioactivity level is vital for population health risk assessment and geological point of view and can be evaluated as rate of exhalation and source concentration (²²⁶Ra, ²³²Th and ⁴⁰K). The present study deals with the soil samples for investigation of radionuclides content and exhalation rates of radon -thoron gas from different sites in northern Haryana, India. Absorbed dose and associated index estimated in the present study are the measures of environmental radioactivity to inhalation dose. Effective doses received by different tissues and organs by considering different occupancy and conditions are also measured. Exhalation rates of radon and thoron are measured with active scintillation monitors based on alpha spectroscopy namely scintillation radon (SRM) and thoron (STM) monitors respectively. Sample height was optimized before measurement of thoron exhalation rate using STM. Average values of radon and thoron exhalation are found 16.6 ± 0.7 mBqkg^-1h^-1 and 132.1 ± 2.6 mBqm^-2s^-1 respectively. Also, a simple approach was also adopted, to evaluate the thoron exhalation which accomplished a lot of challenges, the results are compared with the data obtained experimentally. The study is useful in the nationwide mapping of radon and thoron exhalation rates for understanding the environmental radioactivity status.