Nuclear waste has many sources that are grouped into two broad categories. The first category is nuclear fuel-cycle waste, which consists of any waste arising from the separation and processing of uranium to fabricate nuclear fuel, from nuclear reactors used for any purpose, and from any sub-sequent uses of radioactive materials contained in nuclear fuel or produced in a reactor. Uses of nuclear reactors include generation of electricity; production of plutonium for use in nuclear weapons; production of radioisotopes for use in medicine, industry, or commerce; and research and development. The different types of nuclear fuel-cycle waste include the following:
- High-level radioactive waste arises mainly when spent nuclear fuel from a reactor is chemically reprocessed to remove plutonium for use in nuclear weapons. This highly hazardous waste contains high concentrations of radioactive fission products, such as strontium-90, iodine-131, and cesium-137, and long-lived radionuclides heavier than uranium, such as plutonium and americium.
- Spent nuclear fuel, which resembles high-level waste, is waste if it is not chemically reprocessed. Spent fuel from nuclear power reactors in the United States is not reprocessed at the present time, but reprocessing is carried out in other countries.
- Transuranic waste arises mainly when plutonium removed from spent fuel is used in fabricating nuclear weapons. This waste mostly contains plutonium and other heavy radionuclides, such as americium, in lower concentrations than in high-level waste or spent fuel, although there are exceptions.
- Mill tailings are the very large volumes of residues containing naturally occurring radionuclides that arise mainly when uranium is chemically separated from ores for use in nuclear fuel. The radiation hazard of mill tailings is due mainly to the elevated levels of radium and high emanation rates of radon gas.
- Low-level radioactive waste includes any nuclear fuel-cycle waste other than high-level waste, spent fuel, transuranic waste, and mill tailings. Low-level waste arises in many activities, including operations at nuclear facilities; uses of reactorproduced radioisotopes in medicine, industry, or commerce; cleanup of radioactively contaminated sites; and research and development. Most low-level waste contains relatively low concentrations of radionuclides, but some wastes can be as hazardous as high-level waste or spent fuel.
The second broad category includes any nuclear waste other than the nuclear fuel-cycle wastes described above. Nuclear waste in this category thus includes naturally occurring or acceleratorproduced radioactive material (NARM). Waste containing naturally occurring radioactive material, such as potassium-40, uranium, thorium, or radium, does not include mill tailings. Important wastes of this type include spent radium sources, waste from removal of radionuclides from drinking water, residues from processing of various ores or minerals and other industrial activities, coal ash from electricity generation, and phosphate waste from fertilizer production. Accelerator-produced waste includes accelerator targets any waste arising in the production of medical radioisotopes in accelerators (such as cyclotrons), and subsequent uses of these radioisotopes. Accelerator-produced waste contains mainly short-lived radionuclides and often resembles low-level radioactive waste. In general, NARM waste, especially waste containing naturally occurring radioactive material, has received less attention than nuclear fuel-cycle waste.
DAVID C. KOCHER
League of Women Voters Education Fund (1993). The Nuclear Waste Primer: A Handbook for Citizens, revised edition. New York: Lyons & Burford.