Analysis of ground deposition of radionuclides under different wind fields from the Fukushima Daiichi accident

The relationship between ground deposition of radionuclides and wind fields from the Fukushima Daiichi accident was investigated using the weather research and forecasting/chemistry model with the improvements by adding the radioactive decay process, dry and wet deposition parameterizations. To examine this correlation, wind fields near Fukushima Daiichi nuclear power plant (FDNPP) were defined as four different types mainly based on the wind direction, and the contaminated land areas were classified to five levels. The results showed that the distribution of the ground deposition of the radionuclides is mainly determined by the wind field rather than the precipitation distribution; Northeast wind has the largest contaminated land areas, and it is considered to much more easily accelerate the transport of radionuclides than any other wind direction near the FDNPP. It was also indicated by the results that in terms of high contaminated land area (>100 Bq/m2), total ground deposition is dominated by dry deposition for 131I, and by wet deposition for 137Cs.