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Understanding Radiation
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Understanding Radiation
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Radiation offers many important benefits to society. However, every use of radioactive materials — for mining, nuclear power, managing nuclear weapons, nuclear medicine, and scientific research — generates radioactive waste. The overall risk to the public from radioactive waste is lower than from other sources of radiation, such as radon and nuclear medicine. Areas where nuclear waste is produced, transported, and stored pose potential risks to the environment and people living close to them. Care must be taken to properly isolate the waste materials from the public and the environment. Radioactive materials can:
By responsibly managing the transportation, storage, and disposal of radioactive materials, users and regulators of radiation can greatly reduce the risk to human health and the environment. Radioactive Waste Disposal
Much of the public anxiety and controversy about nuclear
energy and other uses of radioactive materials concerns how radioactive waste is
handled, transported, and disposed of. Some high-level waste will remain hazardous
for 10,000 years or more, further complicating the problem of ensuring safe, long-term
disposal and raising questions about our responsibility to future generations.
Several federal agencies and some states that regulate the risks of radioactive
waste require disposal facilities to effectively isolate the waste. Examples:
Radioactive waste is divided into seven general categories:
Radioactive waste categories are based on the origin of the waste, not necessarily
on the level of radioactivity. For example, some low-level waste is highly radioactive.
Radioactive wastes can remain hazardous for a few days or for hundreds and even
thousands of years, depending on their radioactive half-lives.
Sites and Methods of Waste Disposal
Several major environmental laws affect the operations of many facilities that generate
radioactive waste, including DOE's nuclear weapons facilities.
High-Level Waste: Interim Storage
The United States currently has no permanent disposal facility for high-level radioactive
waste. The NRC says that interim storage methods can be used safely for 100 years.
However, NRC, the nuclear utility industry, and many independent observers believe
it is important to find a long-term solution for nuclear waste disposal. Significant
obstacles to reaching a solution include scientific challenges and public concerns.
As an interim storage method, nuclear reactor operators keep spent nuclear reactor
fuel on site at nuclear power plants and other reactor sites, usually in concrete,
steel-lined pools of water The water cools the warm fuel and also provides shielding
from the radiation. Reactor operating licenses issued by NRC limit the amount of
spent fuel that can be kept on site.
Chemical reprocessing of spent fuel from reactors in the U.S. defense program is
another source of high-level waste. This process, which has been suspended in the
United States, recovered unused uranium and plutonium for making nuclear weapons.
U.S. policies prohibit the reprocessing of spent fuel from commercial nuclear reactors.
The liquid waste from reprocessing is being temporarily stored in underground tanks
or stainless steel silos. These are located on federal reservations in Washington,
South Carolina, and Idaho, and at the Nuclear Fuel Services Plant in West Valley,
New York. Scientists continue to refine techniques for treating this waste so it
can be more easily and safely transported and disposed of after a permanent disposal
site becomes available.
Proposed High-Level Waste Permanent Disposal Site
On July 23, 2002, President Bush signed House Joint Resolution 87, allowing the DOE to take the next step in establishing a repository in which to store our nation's nuclear waste. The Department of Energy is currently in the process of preparing an application to obtain the Nuclear Regulatory Commission license to proceed with construction of the repository. In the Nuclear Waste Policy Act of 1982, Congress called for the development of a mined geologic repository to dispose of spent fuel and high-level radioactive waste. DOE identified nine potential sites in 1983 and selected three as candidates for further study in 1984. In 1987, Congress directed DOE to limit its study to the Yucca Mountain site and to determine whether the site would be suitable for development as a repository. Under the timetable set by Congress in the 1980s, a permanent repository would have begun receiving spent fuel by February 1998. By late 1998, however, DOE announced it would not be ready to make a recommendation on the suitability of the Yucca Mountain site until 2001. The earliest DOE anticipates operating a Yucca Mountain repository is 2010, and many observers believe even this timetable is optimistic. Meanwhile, according to the Nuclear Energy Institute, the nation's nuclear electric utilities and their customers have committed more than $14 billion, including interest, to a Nuclear Waste Fund. This fund is to pay for the government's spent fuel management program, including the permanent repository, an interim storage facility, and the transportation of spent fuel. It will cost about $4 billion of that money to determine if the Yucca Mountain site is suitable. Public Concerns about Permanent Disposal Options In its March 1995 report, Future Issues in Environmental Radiation, a subcommittee of the EPA's Science Advisory Board (SAB) listed radioactive waste management as one of the seven radiation-related issues most likely to have a significant impact on the future quality of the environment. Public apprehensions about disposal risks are a significant impediment to achieving permanent solutions. Here are some excerpts from the SAB report:
Regardless of their categorization, radioactive wastes and the solutions proposed for the disposal problem are feared by many members of the public. This creates a challenging dilemma: on the one hand, the public's perception of the risk of the materials argues strongly for ultimate disposal; on the other, potential risks of the disposal itself are used by opponents to argue against these efforts. Transuranic wastes are also temporarily stored in metal drums and shielded casks at the sites where they are generated — primarily nuclear weapons facilities and national laboratories. Eventually they will be shipped to DOE's permanent disposal facility, the Waste Isolation Pilot Plant (WIPP). The WIPP, located near Carlsbad, New Mexico, cleared its last legal challenges and began receiving waste shipments in March 1999. The WIPP, authorized by Congress in 1979, is the world's first geological repository for the permanent disposal of transuranic wastes and transuranic mixed wastes.
In 1992, Congress passed the WIPP Land Withdrawal Act, which makes EPA responsible for ensuring that the WIPP complies with the agency's radioactive waste disposal standards and other federal environmental laws and regulations. The law requires that EPA certify that the waste stored in the WIPP can be isolated from the human environment for at least 10,000 years. EPA issued this safety certification for the WIPP on May 13, 1998. The facility must be recertified by EPA every five years throughout its operational life. As of the end of January 2002 the WIPP had received 500 shipments of transuranic waste from four DOE sites. Most low-level radioactive wastes are solidified, put into drums, and buried in 20-foot-deep trenches, which are backfilled and covered in clay each day. When full, the trenches are capped with clay and a foot of grassy topsoil. Only a few commercial facilities that permanently dispose of low-level radioactive waste are operating in the United States. The major facilities are located in:
DOE also has seven major low-level waste disposal sites (Figure 24) to dispose of wastes resulting from defense-related activities, research, and cleanup. Under the 1980 Low-Level Radioactive Waste Policy Act, each state must take responsibility for the non-defense related low-level waste generated within its borders. States can act on their own or in a compact with other states. They have established processes for studying and selecting new disposal sites in consultation with citizens and experts and in accordance with federal and state regulations. By July 1, 2000, 44 states had entered into 10 compacts. None of the compacts or states acting alone had successfully opened a new disposal facility by that date, however. Disposal facilities must be designed, operated, and controlled after they are sealed to ensure that the maximum annual radiation exposure to any individual from the site does not exceed 25 millirem per year. Actual exposures from existing commercial facilities have been considerably lower than that figure. Waste containing both radioactive material and hazardous chemicals must be treated and disposed of in accordance with the separate laws governing the two different types of waste.
A number of commercial facilities are authorized to treat, store, and dispose of mixed waste. These facilities include:
Radioactive Waste Cleanup
One of the most difficult and expensive radiation-related
challenges facing the nation in the next century will be to complete the cleanup
of contaminated sites. More than 100 nuclear weapons production sites and thousands
of facilities have been contaminated by radioactivity and radioactive waste. This
cleanup job will last well into the twenty-first century. The contamination is primarily
the result of the nation's arms race with the former Soviet Union during the Cold
War years following World War II, when a huge industrial complex produced and managed
thousands of nuclear weapons.
In addition, radioactive waste from dismantled nuclear reactors, hospitals that
use nuclear medicine, and research laboratories and other facilities that generate
low-level waste will require continuing disposal efforts.
DOE is responsible for the bulk of the nuclear weapons cleanup. In its 1995 report
on its cleanup effort, Closing the Circle on the Splitting of the Atom, DOE
characterized the waste and contamination from nuclear weapons production as "a
task that had, for the most part, been postponed into the indefinite future," adding:
"That future is now upon us."
DOE's nuclear weapons complex consists of 16 major sites and dozens of smaller sites
across the United States. According to the DOE report, every site in the nuclear
weapons complex is contaminated to some degree with radioactive or hazardous materials.
Buildings, soil, air, ground water, and surface water at the sites are contaminated.
EPA sets the criteria for cleaning up the contamination at these facilities. Some
buildings and sites have been cleaned up, but DOE says that most sites have "significant
and complicated problems that have been compounded over several decades."
One of the most troubling examples of the Atomic Age's environmental legacy is DOE's
Hanford Site in Washington State.
Severe contamination problems at the Hanford site include:
Other weapons sites have similar problems.
DOE has begun cleaning up the weapons complex. Some sites have been fully decontaminated and turned over for other uses. DOE is working to:
But the job will not be finished until 2070 at the earliest. Meanwhile, places like Hanford and Rocky Flats will continue to pose some of the nation's most urgent and high-risk radiation management problems. Every 12 to 24 months, each nuclear reactor is shut down, and the oldest fuel assemblies — those that have become depleted in uranium fuel-are removed from the reactor. Each year, the 100-plus operating nuclear power plants in the United States produce about 2,000 metric tons of high-level radioactive waste in the form of spent fuel. While the material is highly radioactive when removed from the reactor, it loses about 50 percent of its radioactivity in three months and about 80 percent after a year. About one percent remains radioactive for thousands of years. Because the United States has not yet built a permanent repository for long-term disposal of spent fuel, the fuel assemblies are temporarily stored at the reactor site. Steel-lined, concrete vaults filled with water, called spent fuel pools, and above-ground steel or steel-reinforced concrete containers with steel inner canisters are usually used for storage.
The nuclear reactor structures, which produce radioactive spent fuel, themselves become radioactive over time. Eventually they must be shut down, and cleaned up, dismantled, or sealed off until the radioactivity has decayed to a point where it no longer presents a hazard. These processes, called decontamination and decommissioning, produce additional quantities of low-level radioactive waste, as well as fission products and other radioactive components that require safe and secure storage or disposal. Some of the contaminated metal from reactors may be salvaged and recycled for other uses. Low-Level Radioactive Waste Government facilities, nuclear reactors, fuel fabrication facilities, uranium fuel conversion plants, industries, universities, research institutes, and medical facilities generate low-level radioactive waste. In addition to DOE facilities, more than 22,000 commercial users of radioactive materials generate some amount of this waste. The cleanup of contaminated buildings and sites will generate still more low-level waste in the future. Only about one percent of the total low-level waste stream comes from hospitals, medical schools, universities, and research laboratories. Much of this waste can be safely stored on site until its radioactivity has decayed to background levels. NRC regulates the medical, academic, and industrial uses of nuclear materials generated by nuclear reactors through a comprehensive inspection and enforcement program. Some 32 states have entered into agreements with NRC to assume regulatory authority over certain radioactive materials, including some radioisotopes. As disposal costs have gone up, large-quantity waste generators have increasingly turned to predisposal waste processing to reduce the volume of low-level waste that must be sent to disposal facilities. This involves measures such as:
While these activities significantly reduce the volume of waste to be disposed of, they also concentrate the radioactivity and thus require more stringent disposal safeguards. Low-level wastes must be properly packaged and disposed of to minimize the chance of exposure to people or the environment. Disposal sites must have features that will isolate the waste from the environment. Radiation levels around disposal facilities must be monitored carefully to ensure that they meet regulatory standards. Orphaned Sources and Contaminated Scrap Metal Many DOE reactors have been shut down in recent years, and hundreds of reactors, processing facilities, and storage tanks will be dismantled as part of the cleanup from the nation's nuclear weapons program. (See Nuclear Weapons Waste.) Dismantling these facilities creates large amounts of scrap steel and other metals, some of which is contaminated by radioactivity. Scrap metal and other waste can also be contaminated by so-called orphaned radioactive sources. These are primarily specialized industrial devices, such as those used for measuring the moisture content of soil and the density or thickness of materials. These devices often contain a small amount of radioactive material sealed in a metal casing or housing. If equipment containing a sealed radioactive source is disposed of improperly or sent out for recycling, the sealed source may wind up in a metal recycling facility. If the item does not have markings identifying its original owners, the source is called an orphaned source. Approximately 200 lost, stolen, or abandoned licensed sources are reported each year. Orphaned sources are one of the most frequently reported radioactive contaminants in shipments received by scrap metal facilities. If an orphaned source is melted during reprocessing, it can contaminate entire batches of scrap metal, the processing equipment, and even the entire facility. The radiation can also pose a hazard to facility workers and to consumers if contaminated recycled metal were to be used in consumer products. EPA is working with state, federal, and international radiation protection organizations to ensure a national supply of clean metal for general use. In 1998, EPA determined that uncontrolled, orphaned sources and contaminated metal imports pose a higher risk to the public and workers than the recycling of scrap metal from nuclear facilities (which is only one tenth of one percent of the metal used in the United States annually). Therefore, EPA has directed its efforts towards orphaned waste and contaminated metal imports as the more significant problem. The agency's orphaned sources initiative, now being carried out in conjunction with the Conference of Radiation Control Programs Directors, has established a nationwide system that provides quick and effective information on identification, removal, and disposal of orphaned sources. The lesser problem, preparation of contaminated scrap metal from domestic nuclear facilities for recycling, continues to follow guidance developed by the NRC and DOE in the 1970s. These standards apply to materials that are contaminated on the surface only and can be decontaminated. DOE suspended the recycling of all contaminated metal in July 2000. Naturally Occurring Radioactive Materials Radioactive materials that occur in nature and become concentrated through human activities (such as mineral extraction and processing) are considered radioactive wastes. These are receiving increasing attention from the federal and state governments. These materials are known as NORM (naturally occurring radioactive materials) or TENORM (technologically enhanced NORM). They are a subset of a broader category of wastes, NARM (naturally occuring and accelerator-produced radioactive materials) which also includes radioactive waste produced during the operation of atomic particle accelerators for medical, research, or industrial purposes. The radioactivity contained in the waste from accelerators is generally short lived, less than one year, and constitutes a very small percentage of the nation's total radioactive waste stream. NORM and TENORM, however, are of growing concern because some of this waste contains relatively high concentrations of radioactivity. Even NORM with a lower concentration of radioactivity can pose disposal problems because of its high volume. Metal mining and processing, for example, will generate an estimated 20 billion metric tons of waste over the next 20 years. NORM is also a problem because some of it is used in construction, concrete, and roadbuilding, resulting in contamination of the environment and possible human radiation exposure. There were no federal regulations covering disposal of NARM with high radioactivity concentrations as of mid-2000. EPA is working to improve the government's understanding of the radiological hazards posed by all these materials, and is working with the states as they develop guidance related to NORM and TENORM. At the request of Congress, EPA sponsored a study of guidance and risk assessment approaches to TENORM. This study was conducted by the National Academy of Sciences and completed in January 1999. Transporting Radioactive Waste
The federal government's plans to create permanent disposal
facilities for radioactive waste lead to continuing public concern over the safe
transport of these hazardous materials to their final resting places. Tens of thousands
of shipments will be required to dispose of spent fuel from the nation's nuclear
reactors, high-level defense waste stored in nuclear weapons complexes, and transuranic
waste designated for the WIPP in New Mexico. Even more shipments will be needed
for the continuing stream of low-level waste.
Two federal agencies, DOT and NRC, are primarily responsible for overseeing radioactive waste transportation. They must minimize the risk of any accidental releases of radiation and carry out a range of regulations:
High-level and transuranic wastes must be transported in airtight, specially shielded stainless steel containers designed to prevent radioactive releases even in a severe accident or other emergency.
The containers (Figures 28 and 29), constructed with inner and outer containment vessels, must survive extreme durability tests including the following:
Some critics continue to question the safety of radioactive waste shipments and the adequacy of container testing. To date, however, the safety record for waste shipments has been good, much better than for shipments of other hazardous materials. As of mid-1998, four accidents had occurred during spent fuel shipments. None of them released radioactive material. Between 1971 and 1999, 62 accidents occurred during the transport of low-level radioactive waste in the United States. Of these, only four resulted in the release of radioactive materials. The radioactive material was quickly cleaned up and repackaged with no measurable radiation exposure to people along the routes or to the emergency response personnel.
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