Yucca
Mountain is a remote desert location used for military
purposes. Yucca Mountain is part
of an isolated, unpopulated desert region in Nevada. It is on
the western border of the Nevada test site, where over 900
nuclear weapons were detonated, most underground, from the
dawn of the atomic age until about ten years ago. This area of
Nevada is still actively used by the U.S. military.
Among the
most comprehensive scientific investigations ever
conducted. The intensive scientific study of Yucca
Mountain's suitability as a national used nuclear fuel
repository—called "site characterization"—has been undertaken
to assess the capability of the natural features at Yucca
Mountain to safely contain radioactive waste. Yucca Mountain
site characterization is one of the most thorough scientific
studies ever performed, lasting years, costing more than $6
billion and involving thousands of scientists, engineers and
technicians.
Initial delay
of Yucca Mountain site characterization. The start of site
characterization was delayed for several reasons, among them
the refusal of Nevada to issue the environmental permits
needed for surface-disturbing work, such as maintaining roads,
digging trenches and drilling boreholes. By mid-1992,
following several court cases involving the U.S. Department of
Energy and Nevada, the state had issued the needed permits and
a full-scale study of the site began with no further
interruption.
Surface-based
investigations of Yucca Mountain mostly completed. For
Yucca Mountain site characterization, a specially developed
rig that can drill to a depth of 3,500 feet has drilled three
deep boreholes. Since the rig uses no drilling fluids, samples
are clean of materials that might otherwise be introduced by
drilling. Other activities include the digging of test pits
for use in volcanism studies, the completion of trenching to
gather data on potential geologic faulting in the area, and
drilling of more than 20 shallow boreholes to study rainwater
infiltration.
Underground
Exploratory Studies Facility constructed inside Yucca
Mountain. In 1994, using a tunnel boring machine, DOE
began constructing a system of tunnels that will allow
scientists to conduct seismological, geological and
hydrological studies—known as the Exploratory Studies
Facility. The five-mile tunnel was completed in 1997. Since
then, scientists have expanded tests in the tunnel and its
numerous niches and alcoves to study the reaction of rock and
the movement of water through the rocks to the heat released
by used nuclear fuel in a repository. The data from these
tests will help scientists design the repository and assess
its performance.
Cross-drift
tunnel constructed to expand internal Yucca Mountain
studies. In 1998, DOE excavated a new tunnel, or
cross-drift, more than a mile inside the existing tunnel. The
cross-drift cuts 1.7 miles through all the rock layers of the
potential repository section, allowing scientists and
engineers to examine and test the rocks that make up the
potential repository.
Full array of
scientific apparatus deployed, data collected and
analyzed. Since completing a 1.7-mile cross-drift tunnel
spanning the entire planned width of the proposed repository
in 1998, DOE has deployed a comprehensive array of scientific
apparatus sufficient to complete its characterization of the
site and prepare for a possible site recommendation decision
at the end of 2001. DOE's scientific instruments have
extracted a wealth of additional data from hundreds of tunnel
alcoves, tunnel niches, and boreholes in the repository rock
as well as from a number of surface locations. The enhanced
knowledge of the repository gained over these past 3 years has
led to a significant refinement of DOE's performance
assessment of Yucca Mountain since the 1998 viability
assessment. This latest information has strengthened
scientific confidence in the repository's ability to protect
public health and safety, while uncovering no reason why used
nuclear fuel and defense high-level radioactive waste should
not be permanently disposed of in Yucca
Mountain.
