Yucca Mountain

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Yucca Mountain

Yucca Mountain is a ridge-line in Nye County, Nevada; composed of volcanic material (mostly tuff) ejected from a now-extinct caldera-forming supervolcano. The "mountain" is most notable as the site of the proposed Yucca Mountain Repository, a U.S. Department of Energy terminal storage facility for spent nuclear fuel and other radioactive waste. Like many nuclear facilities, the proposed Yucca Mountain facility is controversial.

Contents

Background

Spent nuclear fuel is the radioactive by-product of electric power generation at commercial nuclear power plants, and high-level radioactive waste is the by-product from production at defense facilities. In 1982, the United States Congress established a national policy to solve the problem of nuclear waste disposal. This policy is a federal law called the Nuclear Waste Policy Act. Congress based this policy on what most scientists worldwide agreed is the best way to dispose of nuclear waste.

The Nuclear Waste Policy Act made the U.S. Department of Energy (DOE) responsible for finding a site, building, and operating an underground disposal facility called a geologic repository. The recommendation to use a geologic repository dates back to 1957 when the National Academy of Sciences recommended that the best means of protecting the environment and public health and safety would be to dispose of the waste in rock deep underground.

In 1983, the DOE selected nine locations in six states for consideration as potential repository sites. This was based on data collected for nearly ten years. The nine sites were studied and results of these preliminary studies were reported in 1985. Based on these reports, President Reagan approved three sites for intensive scientific study called site characterization. The three sites were Hanford, Washington; Deaf Smith County, Texas; and Yucca Mountain.

In 1987, Congress amended the Nuclear Waste Policy Act and directed DOE to study only Yucca Mountain, which is already located within a former nuclear test site. The Act stressed that if, at any time, Yucca Mountain is found unsuitable, studies will be stopped immediately. If that happens, the site will be restored and DOE will seek new direction from Congress.

The facility

Tour group entering North Portal of Yucca Mountain
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Tour group entering North Portal of Yucca Mountain

The purpose of the Yucca Mountain project is to determine if Yucca Mountain is a suitable site for spent nuclear fuel and high-level radioactive waste storage. The prime contractor for the project is Bechtel SAIC Company (a consortium of government contractors Bechtel Corporation and Science Applications International Corporation). The consortium employs 1800 people on the project. The main tunnel of the Exploratory Studies Facility is U-shaped 5 miles (8 km) long and 25 feet (8 m) wide. There are also several cathedral-like alcoves that branch from the main tunnel. It is in these alcoves that most of the scientific experiments are conducted. The galleries (smaller tunnels perpendicular to the main tunnel) where waste will be stored have not been constructed.

The proposed repository zone will cover 1150 acres (4.7 km²), be 1000 feet (300 m) below the surface of the mountain and 1000 feet (300 m) above the water table when and if it is completed. By early 2002, 7 billion US dollars had been spent on the project which has made Yucca Mountain the most studied piece of geology in the world.

The tunnel boring machine (TBM) that excavated the main tunnel cost 13 million US dollars and was 400 feet (125 m) in length when it was in operation. It now sits at its exit point at the South Portal (south entrance) of the facility. The short side tunnel alcoves were excavated using explosives.

Controversy

2010 is the projected date that the facility will begin to accept waste. This project is widely opposed in Nevada and is a hotly debated topic. The state of Nevada is withholding the renewal of water rights to the facility which has forced the contractor to truck in water. Polls indicate that most Nevadans feel that since the US federal government lied about the safety of the nuclear bomb tests, they cannot be trusted in their current assertions that Yucca Mountain site will be safe. There is also general resentment felt by many Nevada residents over the fact that 87% of the land in Nevada is federal property; furthermore, many Nevadans feel it is unfair for their state to have to store nuclear waste when there are no nuclear power plants in Nevada. The nuclear waste is also planned to be shipped to the site by rail which raises concerns for many people over the possibility of rail accidents, sabotage or even theft by terrorists.

Officials counter by pointing to extensive testing of waste containers that show their extreme robustness in the worst situations. In fact, the transport of spent fuel in Europe and Asia is routine with few safety or security issues. Globally, over 70,000 MTU of spent fuel have already been transported by train, truck, and ship. Other proponents of the site say that Nevadans' objections are little more than NIMBYism. In addition, the Nevada Test Site which encompasses Yucca Mountain, is the location where over 900 nuclear weapons have been detonated and continues to serve as primary location for any future nuclear weapons tests if needed. The likelihood that this land area would be used for any other purpose is remote.

On February 12, 2002 the US Secretary of Energy made the decision that this site was suitable to be the nation's nuclear repository. Nevada's governor had 90 days to object and he did so but the United States Congress overrode the objection. If the objection did stand then the site would have to be cleaned up, closed and a new site chosen.

In August 2004 the repository became an election issue, when Senator John Kerry said that he would abandon the plans if elected and accused George W. Bush of going back on a pledge to allow science and not politics to make the decision.

Because of delays in construction, a number of nuclear power plants in the U.S. have resorted to storing waste on-site indefinitely in large steel casks. This system, known as dry cask storage, is itself very controversial, and there are many questions about safety. It is possible that a temporary facility may open at the Yucca Mountain site or somewhere else in the American west if opening of the underground storage continues to be held up.

Stability

Geology

Seismic activity, -
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Seismic activity, 1976-1996

Yucca Mountain is located within Nye County in south central Nevada. The formation that makes up Yucca Mountain was created by several large eruptions from a caldera volcano and is composed of alternating layers of welded-tuff, non-welded tuff, and semi-welded tuff. Tuff has special physical, chemical and thermal characteristics that some experts believe make it a suitable material to entomb radioactive waste for the hundreds of thousands of years required for the waste to become safe through radioactive decay.

Like any geologic formation, Yucca Mountain is criss-crossed by cracks and fissures. Some of these cracks extend from the planned storage area all the way to the water table 1000 feet (300 m) below. It is feared by some that these cracks may provide a route for radioactive waste after the predicted containment failure of the waste containers several hundred years from now. Officials state that the waste containers will be stored in such a way as to minimize or even nearly eliminate this possibility. Even without cracks tuff is slightly permeable to water but due to the depth to the water table it is estimated that by the time the waste enters the water supply it will be safe.

However, the area around Yucca Mountain received much more rain in the geologic past and the water table was consequently much higher than it is today. Critics contend that future climate cannot be predicted to 10,000 years so it is optimistic to assume that the area will always be as arid as it is today. Most geologists that have worked at the site still maintain that the geology will adequately slow the rate of waste seepage to protect water supplies even if the local climate becomes much wetter.

Seismic activity

According to Nevada's Agency for Nuclear Projects, "since 1976, there have been 621 seismic events of magnitude greater than 2.5 within [an 80km] radius of Yucca Mountain." The largest of these earthquakes was in 1992, with a magnitude of 5.6. There are 33 faults in, or near, the repository site.

See also

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External links

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