COMPARATIVE DISTRIBUTION OF AM-241 AND PU-239,PU-240 IN SOILS AROUND THE ROCKY FLATS ENVIRONMENTAL TECHNOLOGY SITE

The distribution and behavior of Am-241 and Pu-239,Pu-240 in soils fro m the buffer zone of the Rocky Flats Environmental Technology Site hav e been investigated, Concentrations of both radionuclides decreased at similar rates with soil depth. More than 80% of the total inventory o f both contaminants was found in the upper 9 cm of the soils with over 50% of the inventory residing in the top 3 cm. Comparison with earlie r studies indicate that the plutonium depth profile has not changed si gnificantly over the last 25 y. The inventories of Am-241 and Pu-239,P u-240 decreased with distance from the 903 Pad (a former waste storage site) according to a power function, and the plume extended mainly to ward the east, The lateral movement of the two contaminants away from the 903 Pad was not significantly different, The median activity ratio of Am-241:Pu-239,Pu-240 ranged from 17 to 19% and was independent of sampling location and soil depth, This observation provided further ev idence that the movement of both contaminants is indistinguishable in the study area, Because of the strong correlation between the two radi onuclides, Am-241 concentrations can then be used to infer Pu-239,Pu-2 40 by counting the Am-241 via gamma spectroscopy.