THE EFFECT OF VARIATIONS IN SOURCE TERM AND PARAMETER VALUES ON ESTIMATES OF RADIATION DOSE TO MAN S. G. Bloom and W. E. Martin Battelle Columbus Laboratories Columbus, Ohio ABSTRACT Models had been previously developed to characterize the general behavior of plutonium in a typical ecosystem at the Nevada Test Site (NTS) and to provide a basis for estimating the radiation dose from 239pu that might be received by a hypothetical man who resides in and obtains most of his food from this ecosystem. The source term and parameters in these models are subject to wide variations due to uncertainties in sampling, measuring, and interpreting plutonium levels in laboratory experiments and in the environment. Regardless of the extent of these variations, previous exercises with the models indicate that inhalation is far more significant than ingestion as a pathway for transporting 233pu to man and that the lung and bone are the critical organs for radiation dose estimates. These features are used to develop simpler forms of the models which are then used to examine the effects of variations in the source term and parameters. The most significant effects are due to variations in average soil concentration, mass loading factor for air, and the parameters of the lung model used for radiation dose estimates. Average soil concentration can range over several orders of magnitude and radiation dose estimates are directly proportional to this source term. The mass loading factor can also have a wide range of values to which the dose rate to lungs is directly proportional for all practical purposes. The parameters in the lung model are a function of particle size and those chemical and physical factors which determine the translocation class. The effects of particle size are significant but the translocation class has a much greater effect. Particle size within the respirable range can cause a factor of 6 variation in dose rate to lungs but translocation class can cause a factor of 600 to 700 variation. The variation in the rate for bone is not so large with particle size causing less than a factor of 4 variation and translocation class causing less than a factor of 60 variation. 513