Environmental Mineralogy and Nuclear Waste Disposal During the last five years Peter C. Burns, Massman Associate Professor of Civil Engineering and Geological Sciences, and his team of researchers in the Environmental Mineralogy and Crystal Structures Laboratory have increased the number of known crystal structures of uranium compounds by approximately 25 percent. They have also increased the number of known uranium mineral structures by almost 40 percent. This is especially noteworthy given the emphasis of the research; Burns focuses on the geologic disposal of nuclear waste and the mobility of actinides in the environment. “We now have sufficient understanding of the solid phases of uranium,” he says, “to conduct very specific experiments which can help predict the mobility of radionuclides in a geologic repository.” Funded by the Environmental Management Science Program of the Department of Energy, Burns’ research is helping to identify how spent nuclear fuel breaks down over time, what alteration phases form, and how those alteration phases impact the mobility of radioactive waste. According to Burns, the most critical step in preventing radionuclides from being released is understanding and controlling the waste form. If it is a stable entity, the nuclear waste can sit in the repository for 10,000 years -- the number of years specified by the Nuclear Regulatory Commission as necessary before a repository can be deemed safe -- without a problem. “On the other hand,” says Burns, “if the waste forms are problematic from the start, then safety becomes more a function of the geology of the region and the engineered barriers in the repository. The risk of something going wrong increases considerably.” Burns and his team have been providing many of the research parameters for the complex performance assessment models involving a nuclear waste repository and the geologic area surrounding it, specifically Nevada’s Yucca Mountain. Yucca Mountain is currently the only site being considered for development as the nation’s first long-term geologic repository for high-level radioactive waste. The physical characteristics of Yucca Mountain that many researchers cite as favorable for a repository include its distance from a large population. It is 100 miles from Las Vegas. Nevada’s dry climate, less than six inches of rainfall a year; an extremely deep water table, 800 to 1,000 feet below the proposed repository floor; and the unique combinations of rock around the site have also been identified as positive and “safe” characteristics. Burns’ focus has been less on the location and more on getting the storable form of the nuclear wastes right. “Then,” he says, “everything else is just a redundant barrier, adding factors of safety.” Another project being examined in the Environmental Mineralogy Lab deals with dioxin-bearing clays, chickens, and farm-raised catfish. Both the Environmental Protection Agency (EPA) and Georgia-Pacific Corporation found dioxins in the clay binder of soybean meal used as feed for chickens and farm-raised catfish. After several months of investigation and extracting soil from the mine where the clay was taken, the EPA found that the samples were heavily contaminated with dioxin but were unable to identify its source. Dioxins have a congener profile, a fingerprint based upon their atomic weights. The congener profiles found in the soybean meal did not match with any known source: Agent Orange, standard pesticides, pulp mill emissions, etc. However, further studies of clay deposits in the geologic area called the Mississippi Embayment indicated similar levels of dioxins with the same general profiles of the dioxins found in the soybean meal. Burns and his team have a grant from Georgia-Pacific Corporation to identify the origins of the dioxins. They have begun characterizing the mineralogy of 40 to 50 samples taken by both Georgia-Pacific and the EPA. “We are finding that the mineralogy of these dioxin-bearing clays is very complicated and variable. But we believe there is a correlation between the dioxin content and the mineralogy,” says Burns. “The dioxins may have been laid down millions of years ago, or they may have been introduced through slowly percolating groundwater, which would still mean they were natural. If they’re not natural, then some as yet unknown mechanism transported them from the surface into the clay very rapidly.” According to Burns, unnatural dioxins have only been in existence for roughly a century. So, if the dioxins are not natural, there remains an undiscovered geologic process that has modified the congener profile so it is no longer recognizable. The dioxin project presents a very interesting question from an organic chemistry and geologic point of view. The Debate Over Yucca Mountain As part of a course emphasizing regional field geology, students in the Department of Civil Engineering and Geological Sciences toured Nevada’s Yucca Mountain facilities during the spring of 2002. At that time Yucca Mountain had recently received a Presidential recommendation as the U.S. site for the disposal of 70,000 metric tons of high-level nuclear waste. The recommendation initiated an automatic series of events including a congressional review -- for approval or disapproval; the submission of a con-struction license to the Nuclear Regulatory Commission (NRC), if approved by Congress; and a review of the construction license by the NRC, which can take up to four years. The Department of Energy could begin construction of the world’s first geologic repository for high-level nuclear waste upon receiving NRC approval. Most experts around the world agree that the safest method for disposing of radioactive waste is to store it deep underground. Based on this consensus in 1982, Congress passed the Nuclear Waste Policy Act, which instructed the Department of Energy (DOE) to identify a suitable site for an underground geologic repository. In 1983 the DOE targeted nine locations for consideration. Preliminary studies on each site were reported in 1985, narrowing the field to three possibilities Hanford, Wash.; Deaf Smith County, Texas; and Yucca Mountain, Nev. As a result of additional feasibility studies, Congress amended the Nuclear Waste Policy Act in 1987 when it directed the DOE to concentrate its site characterization efforts on the Nevada location. On February 15, 2002, President Bush notified Congress that he considers Yucca Mountain qualified for a construction permit application. His announcement was based on a recommendation by Secretary of Energy Spencer Abraham and more than 20 years of scientific study demonstrating the unique characteristics of Yucca Mountain. In his letter to Congressional leaders, President Bush indicated that proceeding with the Yucca Mountain project was “necessary to protect public safety, health, and the nation’s security because successful completion of this project would isolate in a geologic repository at a remote location the highly radioactive materials now scattered throughout the nation.” The decision on what to do with one of the most dangerous substances known to man has brought much criticism of the President’s recommendation. The Sierra Club has urged the President to reject Yucca Mountain as a possible location, stating that the contamination of groundwater is a tremendous threat to Nevada residents. Citizen’s Alert, a 25-year-old grassroots environmental group based in Nevada, also opposes the use of Yucca Mountain as a nuclear waste repository, citing a high earthquake probability and the potential for groundwater contamination as the top two reasons it “is a bad place for nuclear waste.” Whether or not Yucca Mountain becomes the nation’s first long-term nuclear waste repository is uncertain; the debate is still raging. But there is little doubt about the fact that the future of Yucca Mountain may well determine the future of nuclear technology in the United States.