chapter  6
56 Pages

Radionuclide Transport Processes and Modeling

WithC. M. Vandecasteele

Nuclear electricity production generates large amounts of artificial radionuclides, which may be concentrated through reprocessing into radioactive wastes. Radionuclides discharged into the atmosphere as gas, aerosols, or fine particles are transported downwind, dispersed by atmospheric mixing phenomena, and progressively settled by deposition processes. The atmosphere is the first important path for the dispersion of radioactive pollutants in the environment. Another key parameter influencing the dispersion of airborne contaminants is the stability of the atmosphere, which is determined by the vertical temperature profile of the atmosphere relative to the adiabatic lapse rate, that is, the temperature decrease that a small air parcel undergoes when rising. The Gaussian model is an empirical model providing an analytical solution to the transport and diffusion equations representing short duration or continuous releases of atmospheric pollutants. The Gaussian model is based on the assumption that diffusion of airborne pollutants can be equated to a probabilistic phenomenon, which can be described by a Gaussian equation.