Understanding Contaminant Transport Pathways at Rocky Flats - A Basis for the Remediation Strategy
- Wright Water Engineers, Inc.: 2490 W. 26th Avenue, Suite 100A, Denver, CO 80211 (United States)
The Rocky Flats Environmental Technology Site (RFETS) is a Department of Energy facility located approximately 16 miles northwest of Denver, Colorado. Processing and fabrication of nuclear weapons components occurred at Rocky Flats from 1952 through 1989. Operations at the Site included the use of several radionuclides, including plutonium-239/240 (Pu), americium-241 (Am), and various uranium (U) isotopes, as well as several types of chlorinated solvents. The historic operations resulted in legacy contamination, including contaminated facilities, process waste lines, buried wastes and surface soil contamination. Decontamination and removal of buildings at the site was completed in late 2005, culminating more than ten years of active environmental remediation work. The Corrective Action Decision/Record of Decision was subsequently approved in 2006, signifying regulatory approval and closure of the site. The use of RFETS as a National Wildlife Refuge is scheduled to be in full operation by 2012. To develop a plan for remediating different types of radionuclide contaminants present in the RFETS environment required understanding the different environmental transport pathways for the various actinides. Developing this understanding was the primary objective of the Actinide Migration Evaluation (AME) project. Findings from the AME studies were used in the development of RFETS remediation strategies. The AME project focused on issues of actinide behavior and mobility in surface water, groundwater, air, soil and biota at RFETS. For the purposes of the AME studies, actinide elements addressed included Pu, Am, and U. The AME program, funded by DOE, brought together personnel with a broad range of relevant expertise in technical investigations. The AME advisory panel identified research investigations and approaches that could be used to solve issues related to actinide migration at the Site. An initial step of the AME was to develop a conceptual model to provide a qualitative description of the relationships among potential actinide sources and transport pathways at RFETS. One conceptual model was developed specifically for plutonium and americium, because of their similar geochemical and transport properties. A separate model was developed for uranium because of its different properties and mobility in the environment. These conceptual models were guidelines for quantitative analyses described in the RFETS Pathway Analysis Report, which used existing data from the literature as well as site-specific analyses, including field, laboratory and modeling studies to provide quantitative estimates of actinide migration in the RFETS environment. For pathways where more than one method was used to estimate offsite loads for a specific pathway, the method yielding the highest estimated off-site was used for comparison purposes. For all actinides studied, for pre-remediation conditions, air and surface water were identified to be the dominant transport mechanisms. The estimated annual airborne plutonium-239/240 load transported off site exceeded the surface water load by roughly a factor of 40. However, despite being the largest transport pathway, airborne radionuclide concentrations at the monitoring location with the highest measurements during the period studied were less than two percent of the allowable 10 milli-rem standard governing DOE facilities. Estimated actinide loads for other pathways were much less. Shallow groundwater was approximately two orders of magnitude lower, or 1/100 of the load conveyed in surface water. The estimated biological pathway load for plutonium was approximately five orders of magnitude less, or 1/100,000, of the load estimated for surface-water. The pathway analysis results were taken into consideration during subsequent remediation activities that occurred at the site. For example, when the 903 Pad area was remediated to address elevated concentrations of Pu and Am in the surface soil, portable tent structures were constructed to prevent wind and water erosion from occurring while remediation activities took place. Following remediation of the 903 Pad and surrounding area, coconut erosion blankets were installed to mitigate erosion effects while vegetation was reestablished [2]. These measures were effective tools to address the primary transport mechanisms identified, coupling the scientific understanding of the site with the remediation strategy.
- Research Organization:
- American Nuclear Society, 555 North Kensington Avenue, La Grange Park, Illinois 60526 (United States)
- OSTI ID:
- 21144212
- Resource Relation:
- Conference: DD and R 2007: ANS Topical Meeting on Decommissioning, Decontamination, and Reutilization 2007, Chattanooga, TN (United States), 16-19 Sep 2007; Other Information: Country of input: France; 2 refs; Related Information: In: Proceedings of the 2007 ANS Topical Meeting on Decommissioning, Decontamination, and Reutilization - DD and R 2007, 336 pages.
- Country of Publication:
- United States
- Language:
- English
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