X-Ray Absorption Spectroscopy of Plutonium Particles at the Rocky Flats US Nuclear Weapons Production Site

Abstract

The Rocky Flats Environmental Technology Site (RFETS) was a U.S. Department of Energy (DOE) environmental cleanup site located about 15 miles northwest of downtown Denver. Nearly 40 years of nuclear weapons production had left behind a legacy of contaminated facilities, soils, surface and groundwater. Ultrafiltration studies had shown that plutonium was associated with particles. We employed X-ray absorption spectroscopy to demonstrate that plutonium in soils at the Site was in the insoluble chemical form of PuO2. This information coupled with ultrafiltration studies was used to make the case for particle transport mechanisms as the basis of plutonium and americium mobility, rather than aqueous solubility processes, and established a successful scientific basis for the dominance of physical transport processes by wind and water. This understanding allowed Site contractors to rapidly move to application of soil erosion and sediment transport models as the means of predicting plutonium and americium transport, which led to design and application of site-wide soil erosion control technology to help control downstream concentrations of plutonium and americium in streamflow. Good scientific understanding in the public interest helped the most extensive cleanup in the history of Superfund legislation to finish 1 year ahead of schedule, ultimately resulting in billions of dollars in taxpayer savings.