The US Nuclear Regulatory Commission has established two post-closure performance objectives for the Engineered Barrier System (EBS) in a geologic repository. These require containment of the waste followed by controlled release. The EBS for a repository in unsaturated tuff at Yucca Mountain is designed to meet these performance objectives. The major components are the waste form, container, air gap, and borehole liner. Assessment of post-closure performance of the EBS is based on allocating performance for various components toward meeting overall design objectives. Because of the unprecedented time periods considered, 1000 to 10,000 years, computer modeling is essential and will be used in conjunction with testing to assess whether the performance allocations are met. 7 refs., 1 tab.

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Contents: 1. Power reactors.--2. Research and test reactors.--3. Fuels and materials facilities.--4. Environmental and siting.--5. Materials and plant protection.--6. Products.--7. Transportation.--8. Occupational health.--9. Antitrust reviews.--10. General.