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Hydrologic Evaluation and Uncertainty Assessment: Research Sponsored by the U.S. Nuclear Regulatory Commission

The mission of the U.S. Nuclear Regulatory Commission (NRC) is to regulate the nation's civilian use of byproduct, source and special nuclear materials to ensure adequate protection of public health and safety, to promote the common defense and security and to protect the environment. Technical analyses performed to support the agency's mission may include assessments of the migration of radioactive contaminants from licensed facilities to the environment. For example, decommissioning of a licensed facility involves estimation of potential doses to the public from residual radioactivity. This assessment may include simulating infiltration of water and migration of the residual radioactivity through the subsurface environment as a dissolved constituent in the groundwater. Similarly, a performance assessment carried out as part of the licensing of a low-level radioactive waste disposal facility may involve an evaluation of the potential for transport of radionuclides from the facility to the accessible environment.

Pacific Northwest National Laboratory staff have carried out research to support NRC staff evaluations of the hydrologic components of their regulatory analyses. This support has included the development of computer codes and analytical methodologies as documented in a variety of publications. The research carried out for the NRC has covered two broad areas: (1) providing, in part, the technical bases for hydrologic evaluation analyses (specifically an infiltration evaluation methodology) in support of the NRC staff development and testing of a performance assessment methodology for low-level waste disposal facilities, and (2) supporting licensing needs for estimating and evaluating parameter uncertainties (including the application of generic databases) for probabilistic site-specific dose assessment modeling conducted as part of decommissioning analyses.

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