11.49. In the United States, plans for a geological repository are cen­tered on Yucca Mountain in Nevada. According to the NRPA, a compre­hensive 10-year program to establish site suitability is required, the start of which has been delayed as a result of objections to the site by the state of Nevada. Should the site be acceptable, an additional 8 years would be required for licensing and construction activities.

11.50. In a conceptual design for the repository, a storage region would be at a depth of 600 to 1200 m from the surface. Suitability “packaged” spent fuel or reprocessed vitrified high-level waste (§11.84) would be stored either in rooms or in holes drilled in the rock. Following a test period of about 50 years when the packages could be retrieved should problems arise, the rooms would be backfilled with excavated rock, which would provide an additional barrier. Since spent fuel is an energy resource should it be reprocessed, there is an argument for reviewing the disposal option during the 50-year retrievable period.

11.51. Containment of the waste is based on a multiple barrier ap­proach. The waste container itself is designed to have several barriers, including an outer stainless steel or copper jacket. If high-level reprocessed waste would be stored, it would be in the form of a solid, glasslike, inert material packaged in a metal container. The final, but extremely important barrier to radioisotope migration is the geologic medium itself, which will be considered further in the next section.