Study on the mechanism of incorporation of radioactive substances into rain and snow in the atmosphere and its modeling

Basic procedures which allow to estimate the diffusion and the deposition of particles under metrological conditions with rainfall and snowfall were developed considering that there appeared local depositions of radionuclides at high concentrations through rainfalls at Chernobyl accident in 1986. Thus, an all-weather type model for granular deposition was developed to improve the present computing system designed to be used for information transmission to the residents in the surrounding region and refuge guidance for them based on the estimation. As fundamental calculation methods for current of air, three models; the laminar flow model, the local circulation model and the cumulus convection model were used. Further, it is needed to develop an evaluation model in consideration of the interaction between the atmospheric surface layer and surface materials for assessing the adsorption and contamination of radioactive substances onto drinking water and perishable foods. The development of such model is now under way. (M.N.)