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NUCLEAR WASTE DISPOSAL

Yucca Mountain: 20 years of scientific evaluation

Approach to federal repository location based on science
There is strong international scientific consensus in favor of deep geologic disposal, such as that envisioned at Yucca Mountain. This con-census emerged in the 1950s and was reaffirmed in 2001 by the National Academy of Sciences, which concluded that geologic disposal is the "only credible solution." The U.S. government has had a legal responsibility to dispose of used fuel from nuclear power plants since the passage of the Atomic Energy Act in 1954.

Scientific investigations as part of site characterization at Yucca Mountain include studies of the geological, hydrologic and geochemical environment, and a detailed evaluation of how conditions might evolve over thousands of years. The site has been scientifically analyzed to account for the safe operation of a repository over 10,000 years.

Congress mandated process, responsibilities
The scientific consensus that geologic disposal of high-level radioactive materials should be pursued resulted in the Nuclear Waste Policy Act of 1982, establishing federal government responsibility and policy for disposal of used nuclear fuel and high-level radioactive waste.

The following responsibilities were assigned by Congress:

One year after a 1986 DOE study that ranked Yucca Mountain first among potential repository sites, Congress amended the NWPA and directed DOE to focus its investigation entirely on Yucca Mountain. The desert site is located on federal land near the Nevada nuclear weapons test site.

DOE has evaluated the site to ensure that public health and the environment will be protected over the lifetime of the project. DOE has developed preliminary engineering specifications for the repository and related facilities, as well as specially designed containers that will safely isolate the nuclear material from the environment. Analyses that integrate the repository design and site-specific data and models have been conducted to assess the long-term performance of a repository at Yucca Mountain.

Major report serves as principal scientific benchmark
The capstone scientific document of nearly 20 years and $7 billion of science, DOE's environmental and engineering study, was released in August 2001. The Yucca Mountain Preliminary Site Suitability Evaluation is the final major science document in the process of evaluating Yucca Mountain, and it paves the way for a decision by Energy Secretary Spencer Abraham on whether to recommend the site to President Bush for development.

"Based on results of this preliminary suitability evaluation...DOE is continuing the process of determining whether to recommend the Yucca Mountain site for the location of a repository," DOE said in the evaluation.

If President Bush concurs with DOE that the site is suitable, Nevada will have an opportunity to reject the president's decision. If the host state does so, then Congress would make the final decision.

If the Yucca Mountain site recommendation is approved, it will be followed by a rigorous licensing process by the U.S. Nuclear Regulatory Com-mission for both construction and operation of a repository. This licensing process provides decision-makers additional confidence that public health and the environment will be protected.

DOE's Preliminary Site Suitability Evaluation said that the repository will perform well within the safety standard for Yucca Mountain set by the Environmental Protection Agency. The report shows that the largest expected annual radiation dose would be 0.1 millirem-a small fraction of EPA's annual limit of 15 millirem for that facility.

One-tenth of a millirem is a miniscule amount of radiation compared to natural radiation levels. On average, Americans receive more than 300 millirem each year. By comparison, 0.1 millirem is the average exposure Americans receive by eating 20 bananas or watching television over the course of a year.

DOE has developed five potential engineered repository designs and all comply with the EPA regulation for Yucca Mountain. DOE is conducting experiments at various locations (including Lawrence Livermore National Laboratory, the University of Virginia and the University of Western Ontario) to further test the ability of the materials used to manufacture containers for used nuclear fuel to withstand a wide range of harsh thermal, geochemical, and mechanical conditions.

Of the 16 nations where geologic disposal is being studied, only the U.S.-proposed site of Yucca Mountain is situated far above the water table-1,000 feet above it. Yucca Mountain has arid features that are important to the comprehensive strategy to manage used nuclear fuel over thousands of years. This strategy uses both natural and man-made features to ensure public safety and environmental protection.

The site's outstanding natural features are amplified by an array of engineered features. A key feature in this multiple-layered safety system is the corrosion-resistant containers. The containers are made of alloy C-22, which is one of the most durable metals known to man. DOE also is proposing titanium drip shields over the containers, which would channel the little water that moves through the mountain away from the containers to further ensure their long-term integrity.

DOE's safety analysis tests these natural and engineered features by examining what would happen in the event of highly improbable events such as earthquakes, volcanoes and inadvertent disturbance of the site centuries from now.

The Energy Department also conservatively assumes that the climate will become wetter in the future and that this additional water is able to penetrate the mountain more effectively than at present. Even assuming these dramatic changes, the analyses show that the public will be protected.

Timeline for the development of a U.S. repository

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