Applicability of RESRAD Codes as Tools for Evaluating Radioactive Waste Landfills and Release Sites - 22344

Naturally occurring radioactive material (NORM) can be disposed of at a variety of sites, including Resource Conservation and Recovery Act (RCRA) landfills where low levels of radioactive waste are accepted. Sites of inadvertent release of NORM at oil fields may occur that may or may not need remediation. The residual radioactivity (RESRAD) set of computer codes, developed by Argonne National Laboratory for the U.S. Department of Energy (DOE), support the evaluation of several environmental transport pathways related to a radionuclide-contaminated soil source term, but it was not conceived as a model for the evaluation of landfill radiological performance. A critique of the use of the RESRAD family of codes to address radioactive waste landfill and release sites is presented in this paper. Other system-level transport and dose codes, such as GoldSim, GENII, MEPAS, and NORMALYSA are also discussed. The applicability of RESRAD for radioactive waste disposed of under landfill conditions and at spill sites are explored with a focus on identifying approaches and critical factors in identifying the appropriate platform. Advantages afforded by the use of RESRAD for modeling radiological dose for a landfill or a spill site include ease of use cost to the user, and familiarity by the regulator. RESRAD codes can provide an appropriate set of analysis tools for screening sites, and for sites with simple soil covers and with contaminated source areas that can be effectively assumed to be homogeneous. Other software codes may be more appropriate to use in situations for which more flexibility and site specificity is desired, including capabilities to evaluate other potentially relevant environmental transport processes, such as plant and animal transport, which are not supported in RESRAD. Other codes may also be more appropriate to evaluate sites with more complex conditions such as sites with engineered covers, multiple source areas, or multiple aquifers. Other codes may be more appropriate for some sites and situations where the specific inclusion of uncertainty in input parameters is important to capture in the site evaluation rather than using deterministic input values typically used for a screening assessment. Consideration of the conceptual site model, the decisions to be made at the site, as well as strengths and limitations of modeling tools are important for any computer code that one might use to assess risk from potential radionuclide contamination. Key contaminant transport pathways and dose exposure routes are important when choosing RESRAD or other modeling tools to address the decision problem. For example, if biotic transport is an important contaminant transport pathway, RESRAD would not likely be the best choice for the site. It is, perhaps, not the tool that needs to be critiqued, so much as the choice and application of the tool, be it RESRAD, GoldSim or another system-level code for analyzing transport of contaminants and resultant risks. (authors)