Updating source term and atmospheric dispersion simulations for the dose reconstruction in Fukushima Daiichi Nuclear Power Station Accident

In order to assess the radiological dose to the public resulting from the Fukushima Daiichi Nuclear Power Station (FDNPS) accident in Japan, especially for the early phase of the accident when no measured data are available for that purpose, the spatial and temporal distribution of radioactive materials in the environment are reconstructed by computer simulations. In this study, by refining the source term of radioactive materials discharged into the atmosphere and modifying the atmospheric transport, dispersion and deposition model (ATDM), the atmospheric dispersion simulation of radioactive materials is improved. Then, a database of spatiotemporal distribution of radioactive materials in the air and on the ground surface is developed from the output of the simulation. This database is used in other studies for the dose assessment by coupling with the behavioral pattern of evacuees from the FDNPS accident. By the improvement of the ATDM simulation to use a new meteorological model and sophisticated deposition scheme, the ATDM simulations reproduced well the 137Cs and 131I deposition patterns. For the better reproducibility of dispersion processes, further refinement of the source term was carried out by optimizing it to the improved ATDM simulation by using new monitoring data

タイキ ト リクメンカン ノ ネツ ミズ オヨビ CO2 コウカン ケンキュウ ノ タメノ アタラシイ タイキ - ドジョウ - ショクセイ モデル ノ カイハツ

京都大学0048新制・論文博士博士(理学)乙第11410号論理博第1441号新制||理||1420(附属図書館)UT51-2004-G905(主査)教授 植田 洋匡, 教授 木田 秀次, 教授 余田 成男学位規則第4条第2項該当Doctor of ScienceKyoto UniversityDA

Development of LOcal-scale High-resolution atmospheric DIspersion Model using Large-Eddy Simulation. Part 5: detailed simulation of turbulent flows and plume dispersion in an actual urban area under real meteorological conditions

We have developed a LOcal-scale High-resolution atmospheric DIspersion Model using Large-Eddy Simulation (LOHDIM-LES) to assess the safety at nuclear facilities and to respond to emergency situations resulting from accidental or deliberate releases of radioactive materials (e.g., a terrorist attack in an urban area). In parts 1–4, LESs of turbulent flows and plume dispersion over a flat terrain, around an isolated building, within building arrays with different obstacle densities, and within an actual urban area were performed, which showed the basic performance comparable to wind tunnel experimental technique. In this study, we extend the LOHDIM-LES to turbulent flows and plume dispersion in an actual urban area under real meteorological conditions by coupling with a meso-scale meteorological simulation model. The LES results of wind speed, wind direction, and concentration values are generally reproduced well. It is concluded that our coupling approach between LES and meso-scale meteorological models is effective in detailed simulations of turbulent flows and plume dispersion in urban areas under real meteorological conditions

The Numerical Analysis of the Capping Inversion Effect in a Convective Boundary Layer Flow on the Contaminant Gas Dispersion

Contaminant gas dispersion is of great concern to public health and social security. In the atmosphere, heating and cooling within a boundary layer due to the daily solar cycle result in a temperature differences, which introduces buoyancy forcing. Especially, a convective boundary layer (CBL) capped by a temperature inversion is one of the common cases in the atmospheric boundary layers during daytime conditions. Wind tunnel experimental studies have focused on the characteristics of plume dispersion under a certain thermal condition in a CBL flow. However, CBL flows have shear- and/or buoyancy-driven flows depending on atmospheric stability conditions and the influence of CBLs on plume dispersion behaviours has not been fully discussed. In this study, we performed numerical simulations of CBL flows capped by a temperature inversion with a wide range of atmospheric stability conditions and categorized distribution patterns of plume concentrations. It is found that the critical value of u*/w* in which the patterns of plume dispersion are different is around 0.4

Development of an atmosphere-soil-vegetation model for investigation of radioactive materials transport in the terrestrial biosphere

International audienceIn order to investigate the transport of radioactive materials we have developed a one-dimensional numerical model that predicts the transfer of water, heat, and gaseous and particulate matters in atmosphere-soil-vegetation continuous system. The model calculates dry, wet and fog deposition of gaseous and particulate matters onto vegetation, taken into account the dependency of plant species such as leaf shape and leaf surface area. As a result of performance tests of the model under various environmental conditions, the model predicted the observed temporal changes in heat, water and CO2 fluxes over vegetative and non-vegetative surface, and temperature, water content, and CO2 concentration in the soil under the temperate and arid climate. The model also reproduced observational data of mass fluxes of fog water and atmospheric gases such as ozone and SO2, and number flux of nano-sized aerosols over the vegetation

Development of an atmosphere-soil-vegetation model for investigation of radioactive materials transport in the terrestrial biosphere

International audienceIn order to investigate the transport of radioactive materials we have developed a one-dimensional numerical model that predicts the transfer of water, heat, and gaseous and particulate matters in atmosphere-soil-vegetation continuous system. The model calculates dry, wet and fog deposition of gaseous and particulate matters onto vegetation, taken into account the dependency of plant species such as leaf shape and leaf surface area. As a result of performance tests of the model under various environmental conditions, the model predicted the observed temporal changes in heat, water and CO2 fluxes over vegetative and non-vegetative surface, and temperature, water content, and CO2 concentration in the soil under the temperate and arid climate. The model also reproduced observational data of mass fluxes of fog water and atmospheric gases such as ozone and SO2, and number flux of nano-sized aerosols over the vegetation

Updating source term and atmospheric dispersion simulations for the dose reconstruction in Fukushima Daiichi Nuclear Power Station Accident

In order to assess the radiological dose to the public resulting from the Fukushima Daiichi Nuclear Power Station (FDNPS) accident in Japan, especially for the early phase of the accident when no measured data are available for that purpose, the spatial and temporal distribution of radioactive materials in the environment are reconstructed by computer simulations. In this study, by refining the source term of radioactive materials discharged into the atmosphere and modifying the atmospheric transport, dispersion and deposition model (ATDM), the atmospheric dispersion simulation of radioactive materials is improved. Then, a database of spatiotemporal distribution of radioactive materials in the air and on the ground surface is developed from the output of the simulation. This database is used in other studies for the dose assessment by coupling with the behavioral pattern of evacuees from the FDNPS accident. By the improvement of the ATDM simulation to use a new meteorological model and sophisticated deposition scheme, the ATDM simulations reproduced well the 137Cs and 131I deposition patterns. For the better reproducibility of dispersion processes, further refinement of the source term was carried out by optimizing it to the improved ATDM simulation by using new monitoring data

Updating source term and atmospheric dispersion simulations for the dose reconstruction in Fukushima Daiichi Nuclear Power Station Accident

In order to assess the radiological dose to the public resulting from the Fukushima Daiichi Nuclear Power Station (FDNPS) accident in Japan, especially for the early phase of the accident when no measured data are available for that purpose, the spatial and temporal distribution of radioactive materials in the environment are reconstructed by computer simulations. In this study, by refining the source term of radioactive materials discharged into the atmosphere and modifying the atmospheric transport, dispersion and deposition model (ATDM), the atmospheric dispersion simulation of radioactive materials is improved. Then, a database of spatiotemporal distribution of radioactive materials in the air and on the ground surface is developed from the output of the simulation. This database is used in other studies for the dose assessment by coupling with the behavioral pattern of evacuees from the FDNPS accident. By the improvement of the ATDM simulation to use a new meteorological model and sophisticated deposition scheme, the ATDM simulations reproduced well the 137Cs and 131I deposition patterns. For the better reproducibility of dispersion processes, further refinement of the source term was carried out by optimizing it to the improved ATDM simulation by using new monitoring data