Alluvium: Sedimentary material deposited by flowing water.

Aquifer: Porous water-bearing formation (bed or stratum) of permeable rock, sand, or gravel capable of yielding significant quantities of water.

Assay: The qualitative or quantitative analysis of a substance often used to determine the proportion of isotopes in radioactive materials.

Atomic Energy Commission: Created by the United States Congress in 1946 as the civilian agency responsible for producing nuclear weapons. It also researched and regulated atomic energy. In 1975, its weapons production and research activities were transferred to the Energy Research and Development Administration, and its regulatory responsibility was given to the new Nuclear Regulatory Commission.

Baseline: A quantitative expression of planned costs, schedule, and technical requirements for a defined project. Baselines should include criteria to serve as a standard for measuring the status of resources and the progress of a project.

Byproduct: Radioactive material from producing or processing nuclear materials. Some byproducts have beneficial commercial uses.

Byproduct Material: The tailings or wastes produced by the extraction or concentration of uranium or thorium from any ore processed primarily for its source material content. See also, Source Material.

Characterization: Sampling, monitoring, and analysis activities to determine the extent and nature of contamination at a facility or site. Characterization provides the necessary technical information to develop, screen, analyze, and select appropriate cleanup techniques.

Chemical Separation: A process for extracting uranium and plutonium from dissolved spent nuclear fuel and irradiated targets. The fission products that are left behind are high-level waste. Chemical separation is also known as reprocessing.

Decommissioning: Retirement of a nuclear facility, including decontamination and/or dismantlement.

Decontamination: Removal of unwanted radioactive or hazardous contamination by a chemical or mechanical process.

Department of Energy: The cabinet-level U.S. Government agency responsible for nuclear weapons production and energy research and the cleanup of hazardous and radioactive waste at its sites. It was created from the Energy Research and Development Administration and other Federal Government functions in 1977.

Elution: Activities of removing “elutes” a material (uranium) adsorbed on ion exchange resin from the “eluant” solution.

Environmental Impact Statement: A report that documents the information required to evaluate the environmental impact of a project. It informs decisionmakers and the public of the reasonable alternatives that would avoid or minimize adverse impacts or enhance the quality of the environment.

Environmental Management Program: An Office of the Department of Energy that was created in 1989 to oversee the Department's waste management and environmental cleanup efforts. Originally called the Office of Environmental Restoration and Waste Management, it was renamed in 1993.

Environmental Protection Agency: A federal agency established in 1970 to enforce environmental laws, including the Resource Conservation and Recovery Act; the Comprehensive Environmental Response, Compensation, and Liability Act; and the Toxic Substances Control Act.

Environmental Restoration: Although usually described as "cleanup," this function encompasses a wide range of activities, such as stabilizing contaminated soil; treating ground water; decommissioning process buildings, nuclear reactors, chemical separations plants, and many other facilities; and exhuming sludge and buried drums of waste.

Evaporation Pond: A containment pond (that preferably has an impermeable lining of clay or synthetic material such as hypalon) to hold liquid wastes and to concentrate the waste through evaporation.

Geological Repository: A mined facility for disposal of radioactive waste that uses waste packages and the natural geology as barriers to provide waste isolation.

Groundwater: Water beneath the surface in the saturated zone that is under atmospheric or artesian pressure.

Half-Life: The time it takes for an isotope to lose half of its radioactivity.

Heavy Metals: Metallic elements, including those required for plant and animal nutrition, in trace concentration but which become toxic at higher concentrations. Examples are mercury, chromium, cadmium, and lead.

Holding Pond: A structure built to contain large volumes of liquid waste to ensure that it meets environmental requirements prior to release.

Ion Exchange: Reversible exchange of ions adsorbed on a mineral or synthetic polymer surface with ions in solution in contact with the surface. A chemical process used for recovery of uranium from solution by the interchange of ions between a solution and a solid, commonly a resin.

Isotopes: Forms of the same chemical element that differ only by the number of neutrons in their nucleus. Most elements have more than one naturally occurring isotope. Many isotopes have been produced in reactors and scientific laboratories.

Land Use: The ultimate uses to be permitted for currently contaminated lands, waters, and structures at each Department of Energy installation. Land-use decisions will strongly influence the cost of environmental management.

Leachate: The liquid that has percolated through the soil or other medium.

Manhattan Project: The U.S. Government project that produced the first nuclear weapons during World War II. Started in 1942, the Manhattan Project formally ended in 1946. The Hanford Site, Oak Ridge Reservation, and Los Alamos National Laboratory were created for this effort. The project was named for the Manhattan Engineer District of the U.S. Army Corps of Engineers.

Mill Feed: Uranium ore supplied to a crusher or grinding mill in an ore-dressing process.

Mill Tailings: see Tailings.

Minimal Action: An alternative scenario that completely rescopes projects and activities to minimize costs while maintaining Base Case human health and environmental risks and without the restrictions of current environmental regulations or agreements. One of three alternative cases analyzed as part of the Baseline Report.

Mixed Waste: Waste containing both radioactive and hazardous constituents.

National Defense Authorization Act: The federal law, enacted in 1994 and amended in 1995, that required the Secretary of Energy to prepare the Baseline Report.

National Priorities List: The Environmental Protection Agency's list of the most serious uncontrolled or abandoned hazardous waste sites identified for possible long-term remedial action under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA). The list is based primarily on the score a site receives from the Environmental Protection Agency Hazard Ranking System. The Environmental Protection Agency is required to update the National Priorities List at least once a year.

Permeability: The ease with which fluid flows through a porous medium.

Pitcheblende: Uranium oxide (U₃O₈). It is the main component of high-grade African or domestic uranium ore and also contains other oxides and sulfides, including radium, thorium, and lead components.

Pore Space: The open spaces or voides of a rock taken collectively. It is a measure of the amount of liquid or gas that may be absorbed or yielded by a particular formation.

Pregnant Solution: A solution containing dissolved extractable mineral that was leached from the ore; uranium leach solution pumped up from the underground ore zone though a production hole.

Radioactive: Of, caused by, or exhibiting radioactivity.

Radioactivity: The spontaneous emission of radiation from the nucleus of an atom. Radionuclides lose particles and energy through this process.

Radioisotope: A radioactive isotope.

Radon: Chemically inert radioactive gaseous element formed from the decay of radium. A potential health hazard.

Reclamation: Process of restoring surface environment to acceptable pre-existing conditions. Includes surface contouring, equipment removal, well plugging, revegetation, etc.

Relocation of Tailings: Relocation of tailings is sometimes necessary if the pile poses a threat to inhabitants or the environment, for example, through being situated too close to populated areas, on top of aquifers or other sources of water, or in unstable areas such as flood plains or faults near earthquake zones.

Reprocessing: Synonymous with chemical separations.

Restoration: The returning of all affected groundwater to its premining quality for its premining use by employing the best practical technology.

Rip Rap: Cobblestone or coarsely broken rock used for protection against erosion of embankment or gully.

Roll Front: A type of uranium deposition localized as a roll or interface separating an oxidized interior from a reduced exterior. The reduced side of this interface is significantly enriched in uranium.

Runoff: The portion of rainfall that is not absorbed by soil, evaporated, or transpired by plants, but finds its way into streams directly or as overland surface flows.

Site Characterization: An onsite investigation at a known or suspected contaminated waste or release site to determine the extent and type(s) of contamination.

Sludge: Slushy matter or sediment such as that precipitated by the treatment of waste.

Slurry: A viscous liquid with a high solids content.

Source Material: Uranium or thorium ores containing 0.05 percent Uranium or Thorium regulated under the Atomic Energy Act. In general, this includes all materials containing radioactive isotopes in concentrations greater than natural and the byproduct (tailings) from the formation of these concentrated materials.

Tailings: The remaining portion of a metal-bearing ore consisting of finely ground rock and process liquid after some or all of the metal, such as uranium, has been extracted.

Thorium: An element that is a byproduct of the decay of uranium.

Uranium: The basic material for nuclear technology. It is a slightly radioactive naturally occurring heavy metal that is more dense than lead. Uranium is 40 times more common than silver.

Uranium Concentrate: A yellow or brown powder obtained by the milling of uranium ore, processing of in situ leach mining solutions, or as a byproduct of phosphoric acid production.

Uranium Mill: A plant where uranium is separated from ore taken from mines.

Uranium Mill Tailings Radiation Control Act (UMTRA) of 1978: The act that directed the Department of Energy to provide for stabilization and control of the uranium mill tailings from inactive sites in a safe and environmentally sound manner to minimize radiation health hazards to the public. It authorized the Department to undertake remedial actions at 24 designated inactive uranium-processing sites and at an estimated 5,048 vicinity properties.

Uranium Mill Tailings: The sand-like materials left over from the separation of uranium from its ore. More than 99 percent of the ore becomes tailings.

Yellowcake: A natural uranium concentrate that takes its name from its color and texture. Yellowcake typically contains 70 to 90 percent U₃O₈ by weight. It is used as feedstock for uranium fuel enrichment and fuel pellet fabrication.