The production of electricity by any technology produces waste: coal burning creates ash and air pollution, solar-cell wastes contain hazardous heavy metals such as arsenic and cadmium, and nuclear power generates radioactive wastes. Protecting the environment requires careful control of all of these wastes. Radioactive wastes are also a by-product of defense activities, research, medical applications, and industrial production. ORNL has long engaged in development of new technology to ensure safe and environmentally benign disposal of these wastes.

The basis of radioactive waste management is simple. Because radioactive materials become less radioactive over time, the way to safely dispose of radioactive materials is to store them until they become nonradioactive. Different radioactive materials have different half-lives, so their storage times are different. For example, cobalt-60, a radioactive isotope used to sterilize medical equipment and treat cancer, has a five-year half-life. Thus, a pound of radioactive cobalt-60 five years later would decay to a half pound. Every five years the quantity is reduced in half. A rule of thumb is that, after 10 half-lives have passed, the material is essentially no longer radioactive. In contrast, chemical wastes, such as dioxin, can be destroyed by incineration, and toxic heavy-metal wastes, such as lead and arsenic, remain toxic forever and require other waste management technologies to isolate them from the environment.

Very short-lived radioactive wastes are disposed of by storing them in buildings until they are nonradioactive. For example, hospitals use radioactive molybdenum-99/technetium-99m to diagnose diseases and injuries of the brain, liver, and other organs. Because this material has a half-life of three days, hospitals can store molybdenum-99 radioactive wastes for a month until they become nonradioactive. Longer-lived radioactive wastes containing cobalt-60 and similar radioactive materials must be isolated from the environment for approximately 100 years. Such materials are called low-level waste (LLW) and typically become relatively nonhazardous within a century or less. High-level waste (HLW), including spent fuel from power reactors, contains radioactive materials that must be isolated for thousands of years.

Disposal Technologies

The major goal of radioactive waste disposal is to isolate waste materials from groundwater and air until the radioactivity has decayed away. The basic approach is to convert waste to solids that do not readily dissolve in water, put these insoluble solids in sealed waterproof containers, and store the containers away from moving water. For LLW a well-built structure can store the waste. For HLW, the waste must be buried hundreds of meters underground to ensure its isolation from people for thousands of years. In nature, toxic ore deposits, such as lead, arsenic, and cadmium, which have toxicities similar to HLW in a disposal site, do not poison people because the ores are isolated deep underground. Thus, similar underground isolation is planned for disposal of HLW.

ORNL is involved in developing improved methods of LLW and HLW isolation, including engineered waste storage. Michael Gilliam of ORNL's Chemical Technology Division (CTD) is working to devise better wasteforms to solidify liquid LLW. Better methods to predict and demonstrate the long-term performance of waste disposal sites are being developed by researchers in the Environmental Sciences Division. Larry Shappert of CTD and others are testing waste packages to ensure their ability to both store wastes and survive accidents during waste transportation.

On the Oak Ridge Reservation, the staff of the Waste Management and Remedial Action Division is demonstrating tumulus disposal of LLW--a method of storing wastes for more than 100 years until they become nonhazardous. In a tumulus, the solidified waste is confined in concrete packages that are placed on a special concrete pad and covered with layers of different materials to prevent the flow of rainwater through the wastes.

Finally, research is under way at ORNL on advanced disposal options for spent fuel and HLW. Two options are island repositories and waste destruction.

The island repository is a good example of advanced exploratory research--work I have been involved in--to find environments for hazardous wastes where natural forces isolate the wastes from humans. The idea is to place the waste 500 meters under the ocean floor in manmade tunnels accessible by mineshaft on a temporary manmade island. After the repository is filled, the tunnels are backfilled and sealed, and the temporary island is removed. It has several potential advantages.

  • No groundwater flow. Waste disposal sites fail when groundwater runs downhill through a disposal site, dissolves hazardous material, and carries it to the environment by a spring or well water. Under most of the ocean floor, groundwater does not flow because there is no place for it to flow to and no pumping of underground water occurs. With no water movement, wastes cannot escape.

  • On-land disposal sites can fail because of climate changes or accidental human intrusion. The ocean floor is not exposed to climatic changes. Any future human intrusion after removal of the manmade island would require a very large effort by a large, sophisticated organization that would recognize a hazardous disposal site and know what to do if it accidentally entered such a site.

  • The region below the ocean floor has chemically reducing conditions that make most waste insoluble, whereas chemical conditions on land vary.

Added research will be required to confirm the advantages of this disposal option. ORNL is also examining more futuristic options, such as destruction of long-lived radioactive materials using nuclear reactors and accelerators.

How Dangerous Is Radioactive Waste?

Several characteristics of radioactive wastes are often misunderstood.

  • It is widely thought that all radioactive waste is highly hazardous to human health. This assumption is not true. ORNL inventories and projects quantities of all types of radioactive wastes for the U.S. government. Analyses, like those done by CTD's Jerry Klein, show that almost all radioactive waste by volume is LLW, but spent fuel and other forms of HLW contain at least 99% of the radioactivity. Radioactive waste is like any other hazardous waste type--its hazard varies from very toxic (HLW) to some types of LLW that are almost as nontoxic as household garbage.

  • HLW and spent nuclear fuels are highly toxic because they are concentrated. True. This concentration has an advantage. A large nuclear power plant that generates electricity for a half million people produces approximately 25 tons of spent fuel annually. An equivalent coal plant produces 10 million tons annually of air pollutants, potentially hazardous ash, and other wastes. Because spent nuclear fuel is concentrated, large sums of money can be spent per ton to ensure it is carefully disposed of without significantly increasing the cost of electricity. Thus, environmental pollution from properly operated nuclear power plants is low. The large volumes of coal plant emissions make economic pollution control more difficult.

  • Many people believe that disposal sites for radioactive wastes are highly dangerous. In reality, the risks are low for properly disposed of radioactive wastes, and these wastes pose no risk of large-scale accidents. Human experience with lead shows why. Lead poisoning of children has been a major health concern--particularly for children living near freeways. Much of the lead came from leaded gasoline burned in cars. Because of the health problems, leaded gasoline is now banned. Similarly, we have banned use of lead pipes for carrying drinking water because lead can dissolve in the water over time. Lead in car batteries is still acceptable because it does not pose major health risks. The danger occurs when the hazardous material is a liquid, easily dissolves in water, or generates very small airborne particles--in this case, gasoline vaporizes the lead and spreads it through air or water. For the same reasons, the past problems of radioactive wastes have been confined to liquid wastes or wastes that are easily dissolved in water. Radioactive materials, after solidification, packaging, and proper disposal, present small risks because no big energy source is available to spread the material in the environment.

    Institutional Barriers

    The institutional problems in selecting disposal sites are often greater than the technical challenges. Early ignorance, the rush of World War II, and Cold War priorities resulted in a legacy of neglect that is only now being addressed. The Cold War increased the fear of radioactivity. Our national policy was to prevent war by deterrence. This tactic required a potential enemy to fear our nuclear weapons; but in scaring enemies, we scared ourselves. The distinction among low risks from solidified wastes, somewhat larger risks of wastes in liquid form (weapons production sites), and the very large, real dangers of radioactive materials in air (nuclear weapons) was a fine point lost in scaring our enemies. The complexity of waste management and the legacy of past wastes have created real barriers to siting future facilities.

    Our society is also becoming more open and more accepting of an environmental ethic. These desirable changes create new challenges for waste management. Historically, society sited unwanted but needed facilities by building them on the wrong side of the tracks. From the caveman until recently, the waste management philosophy has been "dilution is the solution to pollution." Our goal today--containing radioactive and hazardous waste to isolate it from the environment--requires waste management facilities that were not needed when it was acceptable to dump waste in the river or discharge it up the smokestack. Our changing goals require both new technologies and new institutional arrangements to site facilities in an open, publicly accepted manner. ORNL economists, sociologists, and political scientists are actively investigating how these issues can be resolved. Education is part of the solution, but equally important are mechanisms (such as voluntary siting of facilities and community involvement) to develop trust between local communities and operators of waste disposal sites.

    All forms of energy generation produce wastes--from the toxic metals used to build solar cells to the radioactive wastes from nuclear power plants. Whether this waste is a risk to mankind depends upon the care we take for proper disposal. Just as the end of the Cold War has brought about the need for industrial restructuring from military to civilian applications, ORNL's development of radioactive waste management technologies allows the Laboratory to address waste problems that are a legacy of the Cold War. These efforts enable the Laboratory to better safeguard the environment and reduce costs as it continues to meet the nation's needs in the post-Cold War era.

    Where to?

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