Abstract
We discuss mass deposition equations of radionuclides diffused by the Fukushima Daiichi nuclear disaster. The empirical equations of physical dry and moist depositions are constructed by using numerical atmospheric model simulation results including diffused radioactive substances and precipitation. The gamma-ray fluxes from radionuclides in the tracer are evaluated and the ambient dose rate is calculated. The rates are fitted to observations, and four parameters of the deposition equations are optimized. The equation is not only for empirical and statistical correction of numerical atmospheric model simulation results but also for understanding physical deposition processes.Using the optimized equation, we calculate ambient dose rates from March 15 to 16 in 2011, as for 32 points along R114, R399, and Ban-Etsu highway in Fukushima prefecture. They are measured by teams of MEXT, KEK, and Fukushima prefecture. 71% of the calculation errors are under the ratio 3.1. The error level is remarkably smaller than that of no-optimization.
