The U.S. Department of Energy’s Exploratory Studies Facility
is an underground laboratory at Yucca Mountain that allows scientists
and engineers access to the rock that is being studied for a potential
repository.
This underground laboratory consists of an eight-kilometer (five-mile)
main tunnel with several research areas, or alcoves, connected to
it. Construction of the facility began in 1993 and the main tunnel
was completed in 1997.
In October 1998, miners and scientists completed work on a project
called the Enhanced Characterization of the Repository Block (ECRB).
The ECRB study involved excavating a 2.7-kilometer (1.7-mile) cross-drift
tunnel that starts from the north portion of the Exploratory Studies
Facility near the first curve and crosses the mountain from northeast
to southwest.
Inside the cross-drift tunnel, scientists study properties of the
rock and the behavior of water near the potential repository area.
Data is collected to verify models and predictions about the geology
and hydrology surrounding the cross-drift tunnel.
The purpose of studies at Yucca Mountain is to determine whether
the site is suitable for a high-level radioactive waste and spent
nuclear fuel repository. These studies, collectively called site
characterization, are divided into three types of scientific investigations:
- Surface-based testing, which includes analyzing rock, soil samples,
and water movement;
- Underground testing, which includes examining rock at deep
levels; and
- Laboratory analyses, which encompass analyzing liquid and gas
from rock samples collected from surface-based and underground
test activities.
As portions of the underground laboratory were completed, scientists
and engineers on the Yucca Mountain Site Characterization Project
began working in the alcoves built as deep as 300 meters (1,000
feet) underground. Working underground allows them to observe the
actual conditions within the rock they are studying.
Representing many different fields of expertise, these scientists
and engineers conduct tests to better understand the complex geology
and hydrology of Yucca Mountain. The variety of data gathered helps
them assess the geologic, hydrologic, geoengineering, and geochemical
properties of the different layers of rock deposits that make up
the area being studied.
The tests also provide data for potential repository design and
construction. For instance, scientists are assessing the strength
and response of the rock to the tunnel excavation. This allows them
to understand how the rock would perform in an actual repository.
Two major ramps from the surface, a north ramp and south ramp, now
lead to the underground facilities. The ramps’ diameter, 7.6
meters (25 feet), allows for adequate ventilation and safe passageway
for personnel and vehicles. Additionally, it provides flexibility
in construction and operation of the facility. Eventually, the facility
would encompass 28 hectares (69 acres) of surface buildings and
facilities as well as about 10 kilometers (6.2 miles) of underground
ramps and tunnels.
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