Local-scale high-resolution atmospheric dispersion and dose assessment system; Realization for the first time of dose assessment based on detailed calculation of radioactive material dispersion taking buildings into account

Nakayama, Hiromasa   ; Onodera, Naoyuki   ; Satoh, Daiki   

We developed the local-scale high-resolution atmospheric dispersion and dose assessment system (LHADDAS) for safety and consequence assessment of nuclear facilities and emergency response to nuclear accidents or deliberate releases of radioactive materials in built-up urban areas. This system comprises three parts, namely, preprocessing of input files, main calculation by a local-scale high-resolution atmospheric dispersion model using large-eddy simulation (LOHDIM-LES) or a real-time urban dispersion simulation model based on a lattice Boltzmann method (CityLBM), and postprocessing of dose calculation by a simulation code powered by lattice dose-response functions (SIBYL). LHADDAS has a broad utility and performs excellently in (1) simulating turbulent flows, plume dispersion, and dry deposition under realistic meteorological conditions; (2) simulating real-time tracer dispersion using a locally mesh-refined lattice Boltzmann method; and (3) estimating the air dose rates of radionuclides from air concentrations and surface deposition in consideration of the influence of individual buildings and structures. This system is promising for use in safety assessment of nuclear facilities (as an alternative to wind tunnel experiments), detailed pre/post-analyses of local-scale radioactive plume dispersion in case of nuclear accidents, and quick response to emergency situations resulting from deliberate release of radioactive materials by terrorist attacks in central urban district areas.