What’s high? What’s low? How are classifications decided?

For more information on radioactive waste, a critique of current policies, and suggestions for an alternative approach to radioactive waste management, see IEER’s publication: High-Level Dollars Low-Level Sense

Radioactive Waste: In general, radioactive waste classes are based on the waste’s origin, not on the physical and chemical properties of the waste that could determine its safe management. Other categories of radioactive waste not listed here include mixed waste and NARM wastes (Naturally-Occurring and Accelerator-Produced Radioactive Materials). One common factor for all categories of nuclear waste is the presence of at least some amount of long-lived radionuclides.

Some Classifications of Radioactive Waste
Category of Radioactive Waste Definition
High-Level Waste (HLW)
  1. Spent Fuel: irradiated commercial reactor fuel
  2. Reprocessing Waste: liquid waste from solvent extraction cycles in reprocessing. Also the solids into which liquid wastes may have been converted. NOTE: The Department of Energy defines HLW as reprocessing waste only, while the Nuclear Regulatory Commission defines HLW as spent fuel and reprocessing waste.
Transuranic Waste (TRU) Waste containing elements with atomic numbers (number of protons) greater than 92, the atomic number of uranium. (Thus the term “transuranic,” or “above uranium.”) TRU includes only waste material that contains transuranic elements with half-lives greater than 20 years and concentrations greater than 100 nanocuries per gram. If the concentrations of the half-lives are below the limits, it is possible for waste to have transuranic elements but not be classified as
TRU waste.
Low-Level Waste (LLW) Defined by what it is not. It is radioactive waste not classified as high-level, spent fuel, transuranic or byproduct material such as uranium mill tailings. LLW has four subcategories: Classes A, B, C, and Greater-Than Class-C (GTCC), described below. On average, Class A is
the least hazardous while GTCC is the most hazardous.
Class A On average the least radioactive of the four LLW classes. Primarily contaminated with “short-lived” radionuclides. (average concentration: 0.1 curies/cubic foot)
Class B May be contaminated with a greater amount of “short-lived” radionuclides than Class A.(average concentration: 2 curies/cubic foot)
Class C May be contaminated with greater amounts of long-lived and short-lived radionuclides than Class A or B. (average concentration: 7 curies/cubic foot)
GTCC Most radioactive of the low-level classes. (average concentration: 300 to 2,500 curies/cubic foot) (The 300 figure is based on the 1985 inventory. The higher figure represents anticipated inventory in 2020, including some decommissioning wastes.)

A Few Notes:

  • Radioactive waste is produced by a number of sources, but by far the largest quantities — in terms of both radioactivity and volume — are generated by the commercial nuclear power and military nuclear weapons production industries, and by nuclear fuel cycle activities to support these industries such as uranium mining and processing.
  • Although all elements up to and including uranium are found in nature, no elements with atomic numbers great than uranium — that is, no transuranic elements — are naturally occurring. [1]Thus, transuranic elements are the artificial elements. All transuranic elements are unstable (and thus radioactive), many of them are alpha-emitters, and
    many (although not all) have very long half-lives.
  • Since “low-level” radioactive waste is defined by what it is not, it thus includes everything from slightly radioactive trash (such as mops, gloves, and booties) to highly radioactive activated metals from inside nuclear reactors. It includes both short-lived and long-lived radionucldes.
  • In both the commercial and military sectors, some of the radioactive wastes generated are mixed with hazardous substances, such as organic solvents or other toxic chemicals. Much of this waste (especially the transuranic waste) contains substantial quantities of long-lived radionuclides, such as plutonium-239 and technetium-99. The radioactive components of mixed wastes are regulated under the Atomic Energy Act by the Nuclear Regulatory Commission for commercial sources, and by the Department of Energy for military sources. The hazardous components, however, are subject to regulation by the Environmental Protection Agency according to an environmental law known as the Resource Conservation and Recovery Act (RCRA).
  • NARM wastes (Naturally-Occurring and Accelerator-Produced Radioactive Materials) are orphan wastes not consistently regulated under any current federal standard. NARM includes such materials as radium-226 and thorium-230 produced outside the nuclear fuel-cycle, and radionuclides produced by particle accelerators. NARM wastes are generated by both federal and non-federal facilities.
  • One of the major problems associated with radioactive waste is the fact that much of it will be radioactive — and thus will require isolation from the human environment — for hundreds of thousands, if not millions, of years. Since this is a time period far longer than all of recorded history, the problem of waste disposal presents an enormous challenge.

For more information on radioactive waste, a critique of current policies, and suggestions for an alternative approach to radioactive waste management, see High-Level Dollars Low-Level Sense


  1. Although at least one instance is known in which a small quantity of plutonium (long since decayed away) and fission products must have been created naturally about 2 billion years ago in a “natural’ reactor at an underground location in what is now Gabon, West Africa. This phenomenon was made possible by a high concentration of uranium and by the fact that the percentage of uranium-235 was much higher so long ago than the 0.7 percent found in today’s uranium ores. (Eisenbud 1987, p.171.) ↩ Return