Engineered Barrier System Degradation, Flow, and Transport Process Model Report

Performance of a potential Yucca Mountain high-level radioactive waste repository depends on both the natural barrier system (NBS) and the engineered barrier system (EBS) and on their interactions. Although the waste packages are generally considered as components of the EBS, the EBS as defined in the Engineered Barrier System Degradation, Flow, and Transport Process Model Report (PMR), herein referred to as the EBS PMR, includes all engineered components outside the waste packages. Waste packages and waste-form performance is described and modeled in other PMRs. Performance of the drip shield as a means of diverting water is included here, both as-built and following degradation because of various processes. The specific mechanisms and rates of drip shield failure from corrosion and seismic activity are described and modeled in the WP PMR. To evaluate the postclosure performance of a potential repository at Yucca Mountain, a total system performance assessment (TSPA) will be conducted. A set of nine PMRs, of which this document is one, is being developed to summarize the technical basis for each of the process models supporting the TSPA model. These reports cover the following areas: Integrated Site Model; Unsaturated Zone Flow and Transport; Near Field Environment; Engineered Barrier System Degradation, Flow, and Transport; Waste Package Degradation; Waste Form Degradation; Saturated Zone Flow and Transport; Biosphere; and Disruptive Events.