Effect of Wind Variability on Environmental Consequences of Prolonged Releases of Radioactive Contaminants

The environmental consequences of atmospheric releases of radionuclides are approximated by the bivariate normal diffusion model. Vertical growth of the cloud is dependent on travel time and the stability of the atmosphere. Lateral growth is dependent on travel time and variations in wind velocity. Experimental diffusion data collected following the release of zinc sulphide during stable atmospheric conditions, show that the lateral variance term can be best represented as an exponential function of time. Application of wind variability as a parameter in the model permits a logical extension of time-integrated air concentration calculations to include release times much greater than those used in most experimental studies. The effect of wind variability on environmental consequences is to reduce potential exposures at downwind points of interest. The degree to which these exposures are reduced is dependent upon the rate of release and the dilution rate of the source term. In turn, the dilution rate of the source term is dependent on radioactive decay rate, possible inleakage to the containment vessel and depletion of the contained air-borne material. The model results in a significant reduction of calculated distances to the low population zone boundary as defined by the United States Atomic Energy Commission in the Code of Federal Regulations, Title 10 Part 100, i.e., 10 CFR 100. (author)