The application of an eddy diffusivity model to the dispersion of radionuclides in the atmosphere and the calculation of cloud gamma exposure

A model which has been applied successfully to the study of the mesoscale transport of sulphur compounds can be adapted for radionuclides released from nuclear power stations. Although more complicated than the conventional Gaussian plume models it has several important advantages including the better representation of dry deposition and the variation of dispersion parameters with height above the surface. Building entrainment can be included in a straightforward manner and an approximate method can be used to incorporate isotope-dependent deposition velocities. A new method of calculating cloud gamma exposure is described which is particularly suited to eddy diffusivity models. This model will be used as an alternative to Gaussian plume methods in the BNL safety code NECTAR. (author)