release to the environment and diffusion of radioiodine in the environment, 2

Materials emitted from a stack in the atmosphere move and spread. These phenomena are well known as flow phenomenon and diffusion one. In this article, general feature of the atmospheric diffusion is described, and quantities which affect the diffusion are considered. The diffusion over complex tetrain is very difficult to treat purely theoretically, so wind tunnel experiments are usually carried out. Some details concerning these experiments are discussed. Particulate matters spread somewhat in different way compared to gaseous matters, namely falling velocity and their mobility in wind turbulence appear. The spread of these matters are discussed. Some data reported by Commettees concerning the Accident of Three Miles Island are analysed. From the point of view of diffusion, these data are not sufficiently qualified to be analysed exactly, so only some results are obtained. From the data of aerial observations some reasonable results can be deduced, but from those of ground level observations the results which differ by the order of 10-2 from the results can be deduced. However, the paths of the plume are not distinct and therefore, the difference of this order may be possible. (author)