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Plutonium-239 and Americium-241 Contamination in the Denver Area

Poet, S. E.; Martell, E. A.

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Abstract

Procedures and results of an experimental investigation of 239Pu and 241Am contamination in the environs of the Rocky Flats plutonium plant and elsewhere in the greater Denver area are presented and discussed. Measurements of 239Pu and 90Sr in the top 1 cm surface layer of soils show that in this layer the 239Pu contamination in offsite areas just east of the Rocky Flats plant ranges up to hundreds of times that from nuclear tests. In the more densely populated areas of Denver the Pu contamination level in surface soils is several times fallout. The depth distribution of 239Pu in undisturbed soils in the more heavily contaminated areas show that the contaminant is concentrated largely in a thin surface layer. Results for soils of known last date of disturbance make it evident that most of the offsite Pu accumulated between 1966 and 1969. This corresponds to the period in which Pu in an oil spill area on the plant site was exposed and subjected to wind reentrainment. 241Am, which grows in from 241Pu present in the contaminant, now contributes between 3 and 15% as much alpha activity as 239Pu and ultimately will approach comparable levels. The important unknowns and uncertainties involved in the estimation of inhalation exposures and the carcinogenic risks from the 239Pu contamination in the environs of Rocky Flats are briefly reviewed.

(C)1972Health Physics Society

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