Atmospheric dispersion and deposition

Besides the source term, meteorological factors are decisive for the impact outside the power plant:

• the mean wind determines where (wind direction) the radioactive cloud travels and how fast (wind velocity) it arrives there;
  

• the atmospheric turbulence determines the rate of the vertical and cross-wind diffusion, and thus the dilution of the radioactive cloud;
  

• Amount, kind and duration of precipitation determine, together with the concentration of radionuclides in the atmospheric layer through which the precipitation is falling, the wet deposition;
  

• the surface type (forest, field, concrete, ...), its roughness and humidity as well as the concentration of radionuclides in the layer next to the ground determine the dry deposition (its role is subordinate to the wet deposition).