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Angela BennerUpward Bound Geology Student |
| Facts about Yucca Mountain | Nuclear Waste | Geology of Yucca mountain | | |
Yucca mountain is the proposed site for the nuclear waste that needs to be
disposed of NOT STORED. Right now the waste is only being stored in containers
across the United States. It would be better for it to be in a central
location because it could be observed better. It is located in Nye County, Nevada, about 160 kilometers northwest
of Los Vegas. It is the site of the
proposed national nuclear waste repository.
Because nuclear waste is a dangerous and sensitive material, it is
important to consider the geological conditions of the area, since these
conditions will determine the appropriateness of this proposal.
The
rocks in Yucca
Mountain are between 11 and 15 million years old. Adjacent to
Yucca is seven cinder cone volcanoes that are allegedly non-explosive.
The top layer of Yucca Mountain is made up of a type of rock called
“tuff,” which is formed from volcanic ash, and is also approximately 11.5 million
years old. There are also faults
under Yucca Mountain, and earthquakes have occurred, with the most recent
happening in 1992 and damaging buildings on the site.
Although volcanic activity is improbable, it would be more
dangerous than earthquake activity.
If built, the repository would be located 300 meters below the ground surface. The water table is 240 to 370 meters below that site. This location is considered to be as safe as or safer than burying the waste below the ocean floor, or even sending it to outer space. Other countries with radioactive waste are also considering geological repositories.
Two
U-shaped tunnels would provide access to the repository. The tunnels would slope slightly, and the
repository would be located at their intersection.
These tunnels travel approximately 5 kilometers into the mountain where
they reach the proposed location. These
tunnels were not built by explosives but by an industrial machine that was 25
feet in diameter which, bore the tunnels up to 30 meters per day.
After 50 years of supervising and inspecting the site to make sure that there is no leakage and that it is still appropriate considering any climatic or geological changes, it would be sealed off. The waste would then need to be stored for at least 10,000 years.
Yucca
Mountain is being considered for the nuclear waste repository site for several
reasons. One reason is that it is
located far enough from people that they would have a lower chance of being
affected by leakage. It is in a dry climate; the region receives “less than 6 inches of rainfall a year”
(www.ymp.gov)
and the water table is 800 to 1000 feet below the ground.
This reduces the chance of radioactive material leaking into the
groundwater.
Whether the radioactive material moves quickly or not through
the ground depends upon the presence of fractures in the rock.
If contaminated water infiltrates through pores in the rock, it will
travel so slowly that the chance of contaminating groundwater within the next
10,000 years is slim. In addition to low hydraulic conductivity the rock
below the repository contain Zeolite minerals. Zeolites have the ability to
adsorb the Uranium ions thus containing any leaking Uranium. If the affected water travels
through cracks or faults in the rock, however, it will move much more quickly and
may contaminate the drinking water
with radio nuclides..
Because
of these features, scientists believe that Yucca Mountain may be “capable of
isolating the spent nuclear fuel and high-level radioactive waste.”
(www.ymp.gov)
However, the infiltration rate of the rainwater is variable, and may
cause problems in the calculations of the safety of the groundwater.
If the climate changes, groundwater may be affected in ways that are not
now apparent.
Yucca Mountain is located on several faults, with the Ghost Dance
fault being the most important because of its size.
Much time and effort has gone into studying the size and characteristics
of the faults, which play a major role in the positioning, successfulness and
safety of the repository. More
information is still needed about these faults.
(Whipple, 19)
The proposed repository will be designed to hold 70,000 metric tons of nuclear waste. “Of this tonnage, 90% would be made up of spent fuel from commercial power plants, and the remaining 10% would be from defense wastes.” (Whipple, 1996) There are both liquids and solids in this amount. Still, the repository would not hold all of the US’s nuclear waste; even if no new nuclear power plants were built, the waste from the current plants would not all fit in the repository.
Storage of radioactive waste is a very thought-provoking problem.
The decision to use an area as a repository must be based on many
factors. The geological factors are
sometimes changeable and can therefore create further complications.
While an area may have factors that make it seem a proper place for a
repository, that appropriateness can quickly change with climate or geological
changes.
While we were at Yucca Mountain we had a tour in and on top of the mountain. Our very nice tour guides, Dave and Walter, took us into the tunnel to the "Hot Rocks Project." The geologists heated the rock to a temperature 100 degrees Celsius to see how it would would react to heat when the waste was installed in the tunnel. We then went to "trench 14" and learned a lot about how the water affected the area.
This page was last updated 06/10/02.
This site is maintained by Angela Benner.
For more information contact me at singinghyena85@hotmail.com
