内容記述 | The source term of 137Cs for the Fukushima Daiichi Nuclear Power Station (FDNPS) accident was estimated from the results of local-scale atmospheric dispersion simulations and measurements. To confirm the source term's validity for reproducing the large-scale atmospheric dispersion of 137Cs, this study conducted hemispheric-scale atmospheric and oceanic dispersion simulations. In the dispersion simulations, the atmospheric-dispersion database system Worldwide version of System for Prediction of Environmental Emergency Dose Information (WSPEEDI)-DB and oceanic dispersion model SEA-GEARN-FDM were used. Compared with the air concentrations of 137Cs measured by the Comprehensive Nuclear-Test-Ban Treaty Organization, overall, the WSPEEDI-DB simulation reproduced the measurements with some overestimation. Furthermore, the deposition amounts of 137Cs was investigated using concentrations of 137Cs in seawater. The simulated seawater concentrations of 137Cs were underestimated regionally in the North Pacific. The overestimation and underestimation could be improved without contradiction between the air and seawater concentrations of 137Cs using more realistic precipitation in atmospheric dispersion simulations. This shows that the source term validated in this study could reproduce the spatiotemporal distribution of 137Cs because of the FDNPS accident in both local and large-scale atmospheric dispersion simulations. |