REPOSITORY ENGINEERED BARRIER SYSTEM DESIGN

Abstract

A Viability Assessment (VA) for the Yucca Mountain Project is being completed for delivery in September of 1998. A major element of the VA is the design of a high level waste repository on the Nevada Test Site. The repository is made up of surface and subsurface facilities. The engineered barrier includes the man-made elements of the system that act to retard the migration of radionuclides from a geologic repository. They act in conjunction with the geologic barriers present at Yucca Mountain. The engineered barrier system (EBS) consists of the Waste Package and the underground facility. The focus of this paper is the status of the design of the underground facility portion of the EBS. In addition to a robust waste package, the EBS components in the reference design include a number of features that impede naturally occurring infiltration from reaching and corroding the waste packages. In addition, and as a defense-in-depth strategy, a number of other optional features are being considered. They include drip shields above the waste packages to intercept dripping water and granular backfill around the waste packages to form a diffusion barrier. Plans are being made to test a number of the EBS materials and structures. The Viability Assessment document will discuss the various EBS options and alternative designs and lay out a plan for determining those to be included in the License Application to the Nuclear Regulatory Commission (NRC) scheduled for completion in 2002.