The Effect f Waste Package and Engineered Barrier System Design:Options on Long-Term Waste Package Degradation Characteristics

Sensitivity analyses were conducted to evaluate the impact of a number of waste package and engineered barrier system (EBS) design options on long-term waste package degradation in the potential repository at Yucca Mountain, Nevada. The evaluations were performed by analyzing the waste package degradation in terms of the first breach and first pit-breach profiles with time. Results for each design option were assessed by comparing to results for the reference-case design. An important finding from the analyses is that the waste package lifetime could be extended substantially by limiting and delaying the contact of dripping water with the Alloy 22 corrosion resistant material (CRM) barrier. In the current model, this would keep the CRM barrier outside the conditions that makes the alloy susceptible to localized corrosion. Uncertainty in waste package degradation analysis would be reduced by improved understanding and characterization of the processes that create the local exposure condition on waste package.