원전 사고 시 RASCAL과 HYSPLIT 전산코드를 이용한 대기확산 모델별 방사성물질의 지표면 침적농도 분석

이진오,권재,류강우,장정환,김광표 (사)한국방사선산업학회 2019 방사선산업학회지 Vol.13 No.2

Introduction of the Lagrangian atmospheric dispersion model was considered insteadof the existing Gaussian atmospheric dispersion models for the level 3 probabilistic safety assessmentto reduce uncertainty in the atmospheric dispersion. The objective of the present study was toanalyze atmospheric dispersion behavior, surface deposition, and atmospheric dispersion models. The study was performed using RASCAL computer code, which employs Gaussian plume modeland Gaussian puff model and HYSPLIT computer code, which employs Lagrangian model. Forthe analysis, long-term station blackout accident was assumed. Released radionuclides includedparticle type 137Cs and gaseous type 131I, which are dispersed widely and extensively for nuclearaccident case. Radionuclide emission rate by time resulting from State-of-the-Art Reactor ConsequenceAnalyses project was used as a source term. The atmospheric dispersion behavior and surfacedeposition was analyzed for two case dates, which include a date with average wind speed ofmore than 3 m·s-1 and a date with wind speed of less than 3 m·s-1. For both 137Cs and 131I, atmosphericdispersion directions were roughly similar among three models. However, deposition concentrationof 131I compared with 137Cs was higher by about 100 folds for the Gaussian models andby about 1,000 folds for the Lagrangian model. For 137Cs, deposition concentrations were higherfor Gaussian plume model, Gaussian puff model, and Lagrangian model, in that sequence. For131I, deposition concentrations were generally higher for the Lagrangian model. The difference inthe deposition concentrations can be attributed to differences in the atmospheric concentration byatmospheric dispersion model and dry deposition velocity of released radionuclides. Therefore, it isrequired to study the physico-chemical characteristics of the released radionuclides for more realisticprediction of surface deposition concentration in applying the Lagrangian model instead of theexisting Gaussian plume models in the level 3 PSA. This study results is expected to contribute asan important base data for more realistic prediction of atmospheric

라그랑지 입자 모델을 이용한 k-ε Algebraic Stress Model과 Mellor-Yamada Model의 비교 연구

김상백,오성남 한국대기환경학회 2004 한국대기환경학회지 Vol.20 No.1

The k-ε algebraic stress model (KEASM) was applied to atmospheric dispersion simulation using the Lagrangian particle dispersion model and was compared with the most popular turbulence closure model in the field of atmospheric simulation, the Mellor-Yamada (MY) model. KEASM has been rarely applied to atmospheric simulation, but it includes the pressure redistribution effect of buoyancy due to heat and momentum fluxes. On the other hand, such effect is excluded from MY model. In the simulation study, the difference in the two turbulence models was reflected to both the turbulent velocity and the Lagrangian time scale. There was little difference in the vertical diffusion coefficient σz However, the horizontal diffusion coefficient σy calculated by KEASM was larger than that by MY model, coincided with the Pasquill-Gifford (PG) chart. The applicability of KEASM to atmospheric simulations was demonstrated by the simulations.

Emergency preparedness for the accidental release of radionuclides from the Uljin Nuclear Power Plant in Korea

Park, Soon-Ung,Lee, In-Hye,Joo, Seung Jin,Ju, Jae-Won Elsevier 2017 JOURNAL OF ENVIRONMENTAL RADIOACTIVITY Vol.180 No.-

<P><B>Abstract</B></P> <P>Site specific radionuclide dispersion databases were archived for the emergency response to the hypothetical releases of <SUP>137</SUP>Cs from the Uljin nuclear power plant in Korea. These databases were obtained with the horizontal resolution of 1.5 km in the local domain centered the power plant site by simulations of the Lagrangian Particle Dispersion Model (LPDM) with the Unified Model (UM)–Local Data Assimilation Prediction System (LDAPS). The Eulerian Dispersion Model–East Asia (EDM–EA) with the UM–Global Data Assimilation Prediction System (UM-GDAPS) meteorological models was used to get dispersion databases in the regional domain. The LPDM model was performed for a year with a 5-day interval yielding 72 synoptic time-scale cases in a year. For each case hourly mean near surface concentrations, hourly mean column integrated concentrations, hourly total depositions for 5 consecutive days were archived by the LPDM model in the local domain and by the EDM-EA model in the regional domain of Asia. Among 72 synoptic cases in a year the worst synoptic case that showed the highest mean surface concentration averaged for 5 days in the LPDM model domain was chosen to illustrate the emergency preparedness to the hypothetical accident at the site. The simulated results by the LPDM model with the <SUP>137</SUP>Cs emission rate of the Fukushima nuclear power plant accident for the first 5-day period were found to be able to provide prerequisite information for the emergency response to the early phase of the accident whereas those of the EDM-EA model could provide information required for the environmental impact assessment of the accident in the regional domain. The archived site-specific database of 72 synoptic cases in a year could have a great potential to be used as a prognostic information on the emergency preparedness for the early phase of accident.</P> <P><B>Highlights</B></P> <P> <UL> <LI> An emergency response model for radionuclides is developed. </LI> <LI> Lagrangian Particle Dispersion Model is useful for the emergency preparedness. </LI> <LI> Eulerian Dispersion Model is useful for the long-range transport of radionuclides. </LI> <LI> The dispersion data base for 72 synaptic cases in a year was archived by LPDM. </LI> <LI> The data base could be used effectively for the on-time emergency preparedness. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

우리나라 산불연무영향 예보체계 개발을 위한 산불연무확산모델 고찰 및 제언

박주원,윤호중,이병두,우충식,김영빈,이복남 한국방재학회 2016 한국방재학회논문집 Vol.16 No.6

Due to the increment of forest biomass stock as well as global climate change, the possibility of wildfire occurrence has been risen in Korea. To prevent adverse effects or disasters from such wildland fires, many efforts have been given in fuel-loading management, wildland fire dispersion-model development, response establishment of system to wildland fire, etc. However, wildfire-caused smoke has been given only little attention in Korea, while forest fire-smoke can disperse over vast areas deteriorating the public health. Thus, this study aims to review wildland fire smoke-dispersion models and forecast systems to suggest an appropriate one to contribute to the development of Korean forest-fire smoke impact forecast system. From the review, it was found that the models introduced up to now can be categorized mostly into five model groups by their theoretical approaches: a Box Model, a Gaussian Plume Model, Lagrangian Models which include a Puff Model and a Particle Model, an Eulerian Grid Model, and a Full Physics Model which is based on the Navier-Stokes equations. Regarding the forest-fire smoke impact forecast system, BlueSky series have been widely adopted in North America: BlueSky Framework, BlueSky Canada, BlueSky Playground Beta. Given Korean wildland fire-related situations where most of its wildland fires are a small scale with less than 10 ha-burnt areas, and minimal process time is required for the immediate prediction of smoke dispersion, the Gaussian Plume Model adopted in BlueSky Playground Beta, is suggested for the Korean forest-fire smoke impact forecast system. 우리나라는 산림 바이오매스 축적의 증가와 기후변화 등으로 인해 산불의 발생가능성이 높아지고 있다. 산불로 인한 재난과 피해를 미연에 방지하기 위하여 연료량 관리, 산불확산모델개발, 산불대응체계구축 등과 같은 분야에 많은 노력을 기울이고 있다. 그러나 산불로 인해 발생하는 연무는 광대한 면적에 확산되면서 공공보건에 악영향을 미칠 수 있음에도 불구하고 그에 대한 관심이 낮은 편이다. 이에 본 연구는 우리나라에 적합한 산불연무영향예보체계를 구축하는데 기여하고자 산불연무확산 모델 및 산불연무예보체계를 고찰하고 적합한 모델을 제시하는 것에 목적이 있다. 기존 문헌 고찰 결과, 이제까지 소개된 산불연무확산모델의 대부분은 이론적 접근방법에 따라 상자 모델(Box Model), 가우시안 연속모델(Gaussian Plume Model), 퍼프 모델(Puff Model) 및 입자 모델(Particle Model)을 포함한 라그랑지안 모델(Lagrangian Model), 오일러 격자 모델(Eulerian Grid Model), 그리고 Navier-Stokes 방정식 기반 물리 모델(Full Physics Model)의 5개의 모델 유형으로 구분할 수 있다. 연무확산예측체계와 관련해서는 북미에서는 BlueSky Framework, BlueSky Canada, 및 미 공병대 BlueSky Playground Beta 등의 BlueSky 계열을 채택하고 있다. 10ha 미만의 소형 산불이 대부분이고 연무확산예측을 위한 연산시간을 최소화할 것을 요구하는 우리나라 산불 관련 상황에서는 BlueSky Playground Beta에 사용되는 가우시안 연속모델이 산불연무영향예측체계에 적합한 모델이라고 할 수 있다.

순간적인 화학물질 누출에 따른 초기 피해영향 범위 산정을 위한 분산모델 연구

손태은,이의주,Son, Tai Eun,Lee, Eui Ju 한국안전학회 2022 한국안전학회지 Vol.37 No.2

Most factories deal with toxic or flammable chemicals in their industrial processes. These hazardous substances pose a risk of leakage due to accidents, such as fire and explosion. In the event of chemical release, massive casualties and property damage can result; hence, quantitative risk prediction and assessment are necessary. Several methods are available for evaluating chemical dispersion in the atmosphere, and most analyses are considered neutral in dispersion models and under far-field wind condition. The foregoing assumption renders a model valid only after a considerable time has elapsed from the moment chemicals are released or dispersed from a source. Hence, an initial dispersion model is required to assess risk quantitatively and predict the extent of damage because the most dangerous locations are those near a leak source. In this study, the dispersion model for initial consequence analysis was developed with three-dimensional unsteady advective diffusion equation. In this expression, instantaneous leakage is assumed as a puff, and wind velocity is considered as a coordinate transform in the solution. To minimize the buoyant force, ethane is used as leaked fuel, and two different diffusion coefficients are introduced. The calculated concentration field with a molecular diffusion coefficient shows a moving circular iso-line in the horizontal plane. The maximum concentration decreases as time progresses and distance increases. In the case of using a coefficient for turbulent diffusion, the dispersion along the wind velocity direction is enhanced, and an elliptic iso-contour line is found. The result yielded by a widely used commercial program, ALOHA, was compared with the end point of the lower explosion limit. In the future, we plan to build a more accurate and general initial risk assessment model by considering the turbulence diffusion and buoyancy effect on dispersion.

Model-data comparison of high frequency compressional wave attenuation in water-saturated granular medium with bimodal grain size distribution

Yang, Haesang,Seong, Woojae,Lee, Keunhwa Elsevier 2018 Ultrasonics Vol.82 No.-

<P><B>Abstract</B></P> <P>Several acoustic models, such as the poro-elastic model, visco-elastic model, and multiple scattering model, have been used for describing the dispersion relation in a porous granular medium. However, these models are based on continuum or scattering theory, and therefore cannot explain the broadband measurements in cases where scattering and non-scattering losses co-exist. Additionally, since the models assume that the porous granular medium consists of grains of identical size (unimodal size distribution), the models does not account for the behavior of wave dispersion in a medium that has a distribution of differing grain sizes. As an alternative approach, this study proposes a new broadband attenuation model that describes the high frequency dispersion relation for the p-wave in the case of elastic grain scatterers existing in the background fluid medium. The broadband model combines the Biot-Stoll plus grain contact squirt and shear flow (BICSQS) model and the quasicrystalline approximation (QCA) multiple scattering model. Additionally, distribution of grain size effect is examined rudimentarily through consideration of bimodal grain size distribution. Through the quantitative analysis of the broadband model and measured data, it is shown that the model can explain the attenuation dependencies of frequency and grain size distribution for a water-saturated granular medium in the frequency range from 350kHz to 1.1MHz. This study can be applied to the high frequency acoustic SONAR modeling and design in the water-saturated environment.</P> <P><B>Highlights</B></P> <P> <UL> <LI> High frequency broadband attenuation model is proposed. </LI> <LI> The model considers viscous and scattering losses and bimodal grain size distribution. </LI> <LI> The model describes attenuation dependencies of frequency and grain size distribution for water-saturated granular medium. </LI> </UL> </P>

방사능 누출 사례일의 국내·외 라그랑지안 입자확산 모델링 결과 비교 : Internal Versus Foreign Modeling Results on the Nuclear Spill Event

김철희,송창근 한국대기환경학회 2003 한국대기환경학회지 Vol.19 No.3

A three-dimensional mesoscale atmospheric dispersion modeling system consisting of the Lagrangian particle dispersion model(LPDM) and the meteorological mesoscale model(MM5) was employed to simulate the transport and dispersion of non-reactive pollutant during the nuclear spill event occurred from Sep. 31 to Oct. 3, 1999 in Tokaimura city, Japan. For the comparative analysis of numerical experiment, two more sets of foreign mesoscale modeling system; NCEP(National Centers for Environmental Prediction) and DWD(Deutscher Wetter Dienst) were also applied to address the applicability of air pollution dispersion predictions. We noticed that the simulated results of horizontal wind direction and wind velocity from three meteorological modeling showed remarkably different spatial variatioms, mainly due to the different horizontal resolutions. However, the dispersion process by LPDM was well characterized by meteorological wind fields, and the time-dependent dilution factors(X/Q) were found to be qualitatively simulated in accordance with each mesoscale meteorolocal wind field, suggesting that LPDM has the potential for the use of the real time control at optimization of the urban air pollution provided detailed meteorological wind fields. This paper mainly pertains to the mesoscale modeling approaches, but the results imply that the resolution of meteorological model and the implementation of the relevant scale of air quality model lead to better prediction capabilities in local of urban scale air pollution modeling.

Fukushima ¹³⁷Cs releases dispersion modelling over the Pacific Ocean. Comparisons of models with water, sediment and biota data

Periá,ñ,ez, R.,Bezhenar, R.,Brovchenko, I.,Jung, K.T.,Kamidara, Y.,Kim, K.O.,Kobayashi, T.,Liptak, L.,Maderich, V.,Min, B.I.,Suh, K.S. Elsevier Applied Science Publishers 2019 JOURNAL OF ENVIRONMENTAL RADIOACTIVITY Vol.198 No.-

<P><B>Abstract</B></P> <P>A number of marine radionuclide dispersion models (both Eulerian and Lagrangian) were applied to simulate <SUP>137</SUP>Cs releases from Fukushima Daiichi nuclear power plant accident in 2011 over the Pacific at oceanic scale. Simulations extended over two years and both direct releases into the ocean and deposition of atmospheric releases on the ocean surface were considered. Dispersion models included an embedded biological uptake model (BUM). Three types of BUMs were used: equilibrium, dynamic and allometric. Model results were compared with <SUP>137</SUP>Cs measurements in water (surface, intermediate and deep layers), sediment and biota (zooplankton, non-piscivorous and piscivorous fish). A reasonable agreement in model/model and model/data comparisons was obtained.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Marine dispersion models applied to Fukushima releases in the Pacific Ocean. </LI> <LI> Biological uptake model included within physical dispersion models. </LI> <LI> Model results compared with measurements in water, sediments and biota. </LI> <LI> Generally good agreement in model/model and model/data comparisons. </LI> </UL> </P>

Spectroscopic Ellipsometry and Optical Dispersion Analysis of Nanocrystalline CdS Thin Films

박욱동 한국전기전자재료학회 2018 Transactions on Electrical and Electronic Material Vol.19 No.4

This study reports on spectroscopic ellipsometry (SE) and optical dispersion analysis of chemically deposited CdS thin fi lms. The CdS thin fi lms were prepared using chemical bath deposition and annealed in N 2 atmosphere at temperatures of 100,200, 300, and 500 °C for 60 min. The optical constants of nanocrystalline CdS thin fi lms were investigated with SE. Theellipsometric parameters of the CdS thin fi lms were measured with SE in the photon energy range from 1.24 to 6.48 eV. Toinvestigate the dispersion parameters, the dispersion of the refractive index of the thin fi lms was analyzed using the Wemple–DiDomenico single-oscillator model (W–D model) and the Sellmeier model. The optical dispersion parameters of theoscillator energy, the dispersion energy, the average oscillator strength, and the average oscillator wavelength of CdS thinfi lms were investigated. In addition, dispersion parameters of CdS thin fi lms were investigated as a function of the annealingtemperature. The dispersion parameters of CdS thin fi lms by the W–D model and Sellmeier model change with annealingtemperature, which causes the transformation of the crystal structure.

대기 중 입자 농도 예측을 위한 PUFF-Gaussian 확산 모형 개발

이주용,이승수,이원호 한국풍공학회 2019 한국풍공학회지 Vol.23 No.2

지속적으로 관찰되어 온 백두산 화산폭발 전조 현상들이 사회적 이슈가 되고 있으며 주변국인 일본의 화산활동 또한 활발한 추세이다. 국내와 500km 이상 떨어진 위 화산들은 국내에 직접적인 피해를 주기 어렵지만 화산 분화와 함께 분출되는 화산재의 경우 국내에 직간접적인 피해를 미칠 수 있다. 화산재 확산대응의 일환으로 수치해석 모델이 국내외로 사용되고 있으며 각 수치해석 모델 은 사용된 수치해석 방법에 따라 한계가 있다. 본 논문에서는 라그랑지안 방법을 기반으로 한 PUFF-UAF 모델을 분석하였으며, 초기 입자의 수에 대한 의존성의 문제점과 많은 입자개수를 사용함에도 불구하고 나타나는 화산재 농도 예측의 부정확성에 대한 문제점을 제기하였다. 이에 본 논문 연구를 통하여 라그랑지안 기법의 전산효용성을 이용하고 나타난 문제점을 해결하기 위하여 PUFF-UAF 모 델의 결과에 가우시안 확산 모델을 적용하여 결과를 보완하는 PUFF-Gaussian 모델을 개발하였다. 실제 화산분화로 부터 관측된 결과 와 본 연구로 예측된 결과를 비교한 결과 본 연구에서 제안한 방법의 효용성을 보였다. Mt. Baekdu´s eruption precursors are continuously observed and become a social issue in global scale, and volcanic activities in neighboring Japan are also active. There is no direct risk of the proximity disasters in South Korea in case of eruption incidents from Japan’s volcano or Mt. Baekdu; however severe influences are likely to happen due to volcanic ash spreading. Numerical analysis models are in general used to predict and cope with the diffusion of volcanic ash, where each numerical analysis model has its own limitations caused by the computational algorithm employed. In this study, the authors analyzed the PUFF-UAF model, a ash dispersion model based on Lagrangian approach and found out that the number of particles used in tracking affects the results to a great extent. Even with millions of particles, the concentration of ash predicted by the PUFF-UAF model does not represent the dispersion well. In order to overcome this deficit and utilize the computational efficiency of Lagrangian model, the authors developed PUFF-Gaussian model to consider dispersive nature of the ash by applying the Gaussian diffusion theory to the results of the PUFF-UAF model. The results of proposed method are compared with the field measurements from actual volcanic eruption, and found out that the suggested method can produce very reasonable prediction of ash dispersion.