REPOSITORY PERFORMANCE MODELING IN THE UNITED STATES AFTER YUCCA MOUNTAIN

The total system performance assessment (TSPA) for the proposed Yucca Mountain repository formed one of the primary technical bases for the June 2008 License Application submitted by the United States Department of Energy (DOE) to the Nuclear Regulatory Commission (NRC). The 2008 Yucca Mountain TSPA represented the culmination of more than two decades of advances both in underlying scientific understanding of the site and its engineered barrier systems, and in the application of probabilistic risk assessment methods to the long-term behavior of geologic repositories. The probabilistic estimates of million-year annual radiation doses to hypothetical humans living near the site considered a full range of uncertainties in the performance of natural and engineered systems and the consequences of unlikely disruptive events, as required by NRC regulations, and represented the most complete and detailed development to date of a system-level modeling approach adopted in various forms by most repository programs worldwide. Although the details of the 2008 TSPA were unavoidably site-specific and cannot be readily transferred to other potential disposal concepts, the approach remains broadly applicable and is likely to be an important part of the site selection, characterization, and licensing processes as the United States repository program moves forward. The Department of Energy’s Used Fuel Disposition Campaign (within the Office of Nuclear Energy) is currently using simplified modeling tools to evaluate the potential performance of generic disposal concepts including mined repositories in crystalline rocks, clay/shale rocks, and salt, as well as deep boreholes in crystalline rocks. Although greatly simplified by necessity to apply to generic concepts, these performance assessment models build on the insights gained from the Yucca Mountain TSPA and other similar analyses in the US and internationally.

Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000. This abstract is Sandia publication SAND2011-4972A.