Keeping Nuclear Energy Viable

Keeping Nuclear Energy Viable

This is an excerpt from an article in the 1998 December Science and Technology Review, the house magazine of Lawrence Livermore National Laboratory. The whole article deals with the collection of energy projects in which LLNL is involved. The important thing to note is that storing waste at Yucca Mountain is and will be subject to fierce attack from the ideological anti-nukes. There will be lawsuits. However, the writers of the article choose not to notice the ideological component of the decision to activate Yucca Mountain as a waste storage site.

The decision to ignore ideological attacks is undoubtedly correct from the point of view of getting their work done. However, it means that counterattacks on the anti-nuke ideologists are left to amateurs like me, and there is no publically available analysis of the anti-nuke meme.

Although 20 percent of the country's electrical energy is supplied by nuclear power plants, challenges remain for this source of power. After the experience with Three Mile Island and Chernobyl, concerns continue about the safety and proper waste management of this source of relatively clean electricity.

One issue continuing to concern the public has been the disposal of hazardous nuclear waste generated by nuclear reactors. Thousands of metric tons of spent fuel from commercial nuclear power plants are being stored, temporarily, at facilities that are almost at capacity. A permanent disposal site is crucial, not only for safety and environmental reasons, but also for continuing nuclear power plant operation. Work to provide such a site has been progressing, with Lawrence Livermore involved in a key part of it.

The work on the Yucca Mountain Nuclear Waste Repository is now entering the viability assessment phase, which means that Congress will soon decide whether the Yucca Mountain site is suitable for nuclear waste disposal and whether to seek licensing by the Nuclear Regulatory Commission (NRC). Arriving at this decision point has taken over 20 years.

This considerable effort is required because the project is unique as well as important. No one has had experience in completely isolating stored nuclear waste materials for 1,000 years, which is the capability the NRC is requiring for the repository. After the 1,000-year mark, the nuclear waste releases cannot exceed more than 1 part in 100,000 of its remaining radionuclide inventory, and that rate must hold for at least 10,000 years. This means that repository scientists and engineers must predict how nuclear waste, subject to initially high temperatures as well as radiation, will behave in and interact with its engineered barrier system and the geologic environment for thousands of years.

Lawrence Livermore, one of many organizations working on Yucca Mountain, is responsible for the engineered barrier system to keep the waste contained (see S&TR, March 1996). The work to develop this system includes designing different waste packaging concepts to accommodate spent nuclear fuel and high-level waste, assisting in the design of the containers into which the waste packages will be placed, and studying the interactions of the waste and the waste packaging with the immediate repository environment.

The goal--repository licensability--will be achieved only if high confidence in the long-term safety of the repository is demonstrated. Livermore's work toward this goal is being accomplished by a multidisciplinary team. A wide range of expertise is needed for conducting the detailed investigations of the material behavior and geologic conditions of an engineered barrier system and for developing models that will describe the system's long-term behavior and overall performance. Work performed by Livermore researchers has included a variety of tests to understand corrosion effects on candidate waste packaging materials; detailed measurements of actual blocks of Yucca Mountain rock to understand its thermal, hydrologic, and geochemical characteristics (Figure 2); and testing in the actual repository environment (carried out in onsite laboratories deep within Yucca Mountain) to determine the site's hydrologic and geochemical characteristics.

As the project moves closer to licensing application, which is slated for 2002, Bill Clarke, project leader for engineered barrier system materials, says the project is stepping up its quality assurance (QA) program and checking, certifying, and qualifying all project documentation.

"QA documentation," says Clarke, "provides the basis for scientists and engineers, the regulators, the government, and the public to engage in a process of understanding each other's point of view." The supporting facts and figures in QA documents also allow scientific assessments of repository performance to be defended in licensing hearings.

Clarke says that quality assurance will continue to be important through the long life of the repository because "future researchers without any actual experience on the project will need to understand the threads and progression of this work as they are evaluating repository performance."

One major component of the QA effort deals with the qualification of project software, specifically the large set of numerical models used to simulate repository processes to predict repository performance for tens of thousands of years into the future.

The demands on these models are unprecedented, and development has been challenging because data have been difficult to obtain. For instance, much of the information on how chemical processes affect rocks and other materials over very long times cannot be ascertained by accelerating the change processes in the laboratory. Rather, this information must be obtained from analogs--concrete in civil structures of known ages or very old relics excavated from geologic areas with characteristics relevant to Yucca Mountain geology

The unique models are undergoing a highly structured qualification process that will provide documents describing the purpose, lifecycle, methodologies, and usage of the software. One important component of the documentation is the verification and validation plan, which provides for comparisons of modeling results with other codes, problems, and expert judgment.

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