The Geological Aspects and Future of Nuclear Waste Disposal

Waste is a significant byproduct of many forms of energy production. The waste from nuclear energy production is especially hazardous due to its radioactivity, which has the potential to cause harm to both human and environmental health. As spent nuclear fuel accumulates at commercial reactor sites around the country, the United States is in desperate need of a long-term solution for nuclear waste disposal.

Nuclear waste is typically in the form of highly-radioactive uranium and requires carefully planned disposal in order to minimize risks of exposing the environment or humans to radioactivity.

A 1956 report published by the National Academy of Sciences recommended deep geologic repositories for permanent disposal of nuclear waste. Mined geologic repositories are still considered by scientists today to be the best option for disposal and storage; however, many geologic, environmental, economic and other factors impact site location. Consequently, assessing a site for permanent nuclear waste and spent nuclear fuel is difficult, making earth scientists an invaluable resource for evaluating potential sites.

A potential nuclear waste disposal site should be determined based on its chemical, hydrological, mechanical and thermal properties, as well as human and natural disturbances. The porosity, permeability and thermal conductivity of the rock determine its ability to safely isolate high-level nuclear waste (HLW) from seeping into groundwater supplies. A rock with low porosity, low permeability and high thermal conductivity is preferable when selecting a site for disposal. Salt deposits are recommended as a good medium for disposal of radioactive waste due to the absence of water flow, the ability of salt to fill its own fractures and the ease of mining. Other factors include possible human disturbances. For example, if a repository is placed near a valuable mineral resource, this could increase the likelihood of its disturbance if mining were to occur in the future. Also, location of faults and associated seismicity, which can impact nuclear waste by both breaking and shaking the drums of waste, must also be taken into account when creating a site intended for permanent disposal.

Image Caption

The Diablo Canyon Nuclear Power Plant is located near Avila Beach, Calif. Courtesy of Pacific Gas and Electric.

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Waste is a significant byproduct of many forms of energy production. The waste from nuclear energy production is especially hazardous due to its radioactivity, which has the potential to cause harm to both human and environmental health. As spent nuclear fuel accumulates at commercial reactor sites around the country, the United States is in desperate need of a long-term solution for nuclear waste disposal.

Nuclear waste is typically in the form of highly-radioactive uranium and requires carefully planned disposal in order to minimize risks of exposing the environment or humans to radioactivity.

A 1956 report published by the National Academy of Sciences recommended deep geologic repositories for permanent disposal of nuclear waste. Mined geologic repositories are still considered by scientists today to be the best option for disposal and storage; however, many geologic, environmental, economic and other factors impact site location. Consequently, assessing a site for permanent nuclear waste and spent nuclear fuel is difficult, making earth scientists an invaluable resource for evaluating potential sites.

A potential nuclear waste disposal site should be determined based on its chemical, hydrological, mechanical and thermal properties, as well as human and natural disturbances. The porosity, permeability and thermal conductivity of the rock determine its ability to safely isolate high-level nuclear waste (HLW) from seeping into groundwater supplies. A rock with low porosity, low permeability and high thermal conductivity is preferable when selecting a site for disposal. Salt deposits are recommended as a good medium for disposal of radioactive waste due to the absence of water flow, the ability of salt to fill its own fractures and the ease of mining. Other factors include possible human disturbances. For example, if a repository is placed near a valuable mineral resource, this could increase the likelihood of its disturbance if mining were to occur in the future. Also, location of faults and associated seismicity, which can impact nuclear waste by both breaking and shaking the drums of waste, must also be taken into account when creating a site intended for permanent disposal.

Current Status of Waste Disposal

Within the United States, there are currently 100 licensed and operating nuclear power reactors in 35 states, the vast majority of which are east of the Rocky Mountains. In 2014, these plants produced 19.5 percent of U.S. electricity — a proportion that continues to grow annually. There are 11 new reactors under construction at various sites across the country, increasing our capacity to produce more nuclear energy in years to come, as well as producing more nuclear waste that needs disposal. Nuclear waste is classified in two general categories based on the level of radioactivity: low-level waste (LLW), such as contaminated tools and clothing from reactor operations, and the aforementioned HLW, the spent reactor fuel and nuclear defense weapons waste. Currently, nuclear defense weapon waste, such as materials used to produce nuclear weapons during the Cold War, is disposed of in New Mexico’s Waste Isolation Pilot Plant (WIPP). However, with the exception of WIPP, there is currently no repository for the permanent disposal of HLW and LLW.

Today, a reactor’s spent nuclear fuel is stored on-site at the originating reactor. A 2014 Government Accountability Office (GAO) report found that the United States produces 2,200 metric tons of spent nuclear fuel annually, adding to the 70,000 metric tons of nuclear waste already in temporary storage on reactor sites. Once spent, the high-level uranium waste is cooled in a large pool of water for a minimum of five years, where it loses most of its radioactivity. When these pools reach capacity, the spent fuel is removed and transported to a dry storage module, which is an expensive and time-consuming process. Annual operations for each of these on-site storage facilities can cost between $100,000 and $6.5 million, depending on the reactor’s operational level. The GAO estimates that these on-site storage facilities will contain 139,000 metric tons of nuclear waste by 2067.

Federal Agencies and Current Legislation

The U.S. Department of Energy (DOE) Offices of Environmental Management (EM) and Nuclear Energy (NE) and the Nuclear Regulatory Commission (NRC) Office of Nuclear Material Safety and Safeguards (NMSS) are the main federal agencies involved with nuclear waste disposal. The Environmental Protection Agency (EPA) and state governments are also involved in certain aspects of creating long-term storage sites.

The Nuclear Waste Policy Act of 1982 (NWPA) is the main piece of legislation governing the disposal of HLW. NWPA specified a process for evaluating repository sites, created a Nuclear Waste Fund, and included an outline for interaction between state and federal governments. The Act also required DOE to develop, build and operate a geologic repository; EPA to create environmental standards; and NRC to license DOE to operate the repository within EPA’s standards.

A 1986 amendment to NWPA designated Yucca Mountain in Nevada as the future site of all U.S. commercial nuclear waste, and was granted congressional and presidential approval in 2002. Following this approval and after evaluation of the site, DOE submitted a license application to NRC in 2008 to begin development. However, DOE withdrew its application in 2010, and federal funding for creation of the repository was halted by the Obama administration in 2011 under the Department of Defense Continuing Appropriations Act.

Following the decision to suspend Yucca Mountain as a potential repository, the GAO performed a study to determine the reasons for and effects of termination. Although DOE claims that the Yucca Mountain repository program was terminated because better solutions exist, the GAO report highlighted social and political opposition to the repository as the key issues with creating a permanent disposal site, not technical or geologic conditions. The report also recommended more transparency, economic incentives and public education on nuclear waste, as well as consistent funding, policy and leadership on nuclear waste disposal in order for a comprehensive national plan to be established.

The Future of Domestic Nuclear Energy

In 2010, DOE created the Blue Ribbon Commission (BRC) on America’s Nuclear Future to help identify alternatives to Yucca Mountain. The BRC was required to provide information for the future of HLW disposal, and produced a report in January of 2012. In coordination with DOE, BRC created a timeline to create a pilot interim storage facility by 2021, a full-scale interim storage facility by 2025 and a permanent storage facility by 2048.

The government is examining other types of disposal, such as deep borehole (DBH) disposal, which involves drilling 5,000-meter deep holes into crystalline rock, placing canisters of waste at the bottom of each hole and sealing off the top. The main difference between DBH disposal and repository disposal is distribution of waste. A repository would be at one central location whereas drillholes can be distributed around the nation. In January 2016, DOE selected a team to drill a test borehole near Rugby, N.D.. However, the DOE announcement has been met with pushback from the local government. Currently, the Pierce County Commission, within the jurisdiction of which DBH tests would be administered, has sent a letter to the University of North Dakota Energy And Environmental Research Center asking that the project be abandoned. DOE has not yet released a response to the letter.

When considering the future of U.S. nuclear waste disposal, it may be beneficial to look toward other countries’ disposal methods. Finland is progressing to become the world’s first country to open a permanent repository for HLW. At the Onkalo site, a 420-meter-deep access tunnel in Eurajoki, Finland has already been excavated to reach a granite repository that is set to open in 2020 and have the capacity to receive spent nuclear fuel for at least 100 years. A U.S. Geological Survey study finds that shale formations are another option for disposal; studies in France, Belgium and Switzerland also indicate that shales and other mudrocks may be provide suitable sites for repositories.

The future of nuclear waste disposal in the United States has an uncertain path forward. In order to move the current 70,000 metric tons of spent nuclear fuel from reactors across the nation to a permanent storage facility, a comprehensive action plan in needed that includes coordination across the public, private and academic sectors. However, basic research for nuclear waste disposal options can only go so far, because once a site has been chosen, the local geology will dictate the scientific assessment of repository safety and capability. And, given the social and political recommendations provided in the 2011 GAO report, as well as an outdated NWPA, there is still a need for a complete congressional overhaul of nuclear waste policy and public awareness in order to successfully create a permanent storage solution for nuclear waste in the United States.

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Comments (1)

Nuclear waste
It's good to see nuclear waste disposal featuring in AAPG Explorer. Effective, long-term disposal of nuclear waste and other human wastes (solid and liquid) is an urgent task that needs geoscientists as key participants. Besides being easily soluble, salt is known to move under temperature and pressure. It may not be a safe, long term repository for nuclear wastes. It is deplorable to see the much attainable, down to earth goal of waste disposal and pollution control remains neglected while huge resources are deployed in meeting the doubtful target of global warming.
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12/20/2016 5:15:19 AM

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