SREL Reprint #2523

 

 

 

A review of plutonium releases from the Savannah River Site, subsequent behavior within terrestrial and aquatic environments and the resulting dose to humans

T. G. Hinton and J. E. Pinder, III

University, of Georgia, Savannah River Ecology Laboratory, Drawer E, Aiken, SC 29802, USA

Abstract: This chapter reviews two decades of research on plutonium in terrestrial and aquatic environments of the Savannah River Site (SRS), a nuclear production facility covering 800 km2 of South Carolina, USA. Sources and quantities of Pu released over the facility's 40 years of operation are summarized. Some 160 GBq of 238Pu and 239Pu were released in isotopic ratios that allowed researchers to distinguish site emissions from global fallout. The ratios also proved to be a powerful tool useful for identifying major pathways through which Pu moved in the environment. Two major lines of research are reviewed; one examining Pu transport through agricultural systems typical of the southeastern United States, the other examining Pu dynamics within lake systems. Regardless of the crop studied, Pu contamination of plants was dominated by the retention of Pu-bearing particles on plant surfaces from direct deposition and resuspension, rather than root uptake and translocation of Pu within the plant. Large-scale commercial harvesting of contaminated agricultural crops revealed that mechanized harvesting increased Pu contamination of crops. Differences in Pu concentrations among crops were due largely to external plant morphologies that affected soil loading. Studies on Pu transport in aquatic systems showed that over 99% of the Pu inventory was within lake sediments. Persistent and complex annual cycles still exist for Pu within the lake systems studied, some 20 years after the contamination event. Field studies and modeling helped discern the relative importance of anoxic remobilization from the sediments, hydrologic mixing and sedimentation on the Pu cycle within lakes. Remobilization of Pu in the winter appears to contribute more to the seasonal cycle than does the more commonly observed mechanism of remobilization in summer anoxic waters due to associated Fe-Mn redox phenomena. Doses to humans from Pu releases were also reviewed and found to be less than those acquired from naturally occurring radionuclides or from 137Cs releases. Maximum dose equivalents (85 µSv) to an individual at the site boundary would have occurred in 1955 and the population dose due to releases that occurred from 1954 to 1989 was 7 person-Sv.

Keywords: Plutonium; Atmospheric deposition; Resuspension; Root uptake; Agroecosystems; Aquatic ecosystems; Anoxic remobilization; Sediment traps; Radiation dose; Modeling

SREL Reprint #2523

Hinton, T. G., and J. E. Pinder, III. 2001. A review of plutonium releases from the Savannah River Site, subsequent behavior within terrestrial and aquatic environments and the resulting dose to humans. pp. 413-435 In: A. Kudo (Ed.). Proceedings of the Second International Symposium Plutonium in the Environment. Elsevier, Kyoto University, Osaka, Japan.

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