Post-Closure Evaluation of the Area 3 and Area 5 Radioactive Waste Management Sites at the Nevada National Security Site in Support of the Site-Wide Environmental Impact Statement

The post-closure performance of the Area 3 Radioactive Waste Management Site (RWMS) and Area 5 RWMS are evaluated for the Site-Wide Environmental Impact Statement using current performance assessment and composite analysis methods and models. Two alternatives with different future waste volumes and inventories are evaluated. The No Action Alternative evaluates the inventory disposed through fiscal year (FY) 2010 plus an additional 4.5E5 cubic meters (m3) (1.59E7 cubic feet [ft3]) of waste disposed at the Area 5 RWMS. The Expanded Operations Alternative evaluates the FY 2010 inventory plus an additional 1.42E6 m3 (5.03E7 ft3) of waste disposed at the Area 5 RWMS and 4.93E4 m3 (1.74E6 ft3) disposed at the Area 3 RWMS. Both the No Action and Expanded Operations Alternatives have a reasonable expectation of meeting all performance objectives of U.S. Department of Energy Order DOE O 435.1, “Radioactive Waste Management.” No significant difference between the two alternatives was found because the waste concentrations are similar. The performance assessment model assesses radiological risk for residents at the RWMS boundary where risk is more closely related to waste concentration than total waste inventory. Results for the composite analysis also indicate that the dose constraint and dose limit can be met for both alternatives