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Uranium (U):  A heavy, naturally radioactive, metallic element (atomic number 92). Its two principally occurring isotopes are uranium-235 and uranium-238. Uranium-235 is indispensable to the nuclear industry because it is the only isotope existing in nature, to any appreciable extent, that is fissionable by thermal neutrons. Uranium-238 is also important because it absorbs neutrons to produce a radioactive isotope that subsequently decays to the isotope plutonium-239, which also is fissionable by thermal neutrons.

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 deposit:  A discrete concentration of uranium mineralization that is of possible economic interest.

Uranium endowment:  The uranium that is estimated to occur in rock with a grade of at least 0.01 percent U3O8. The estimate of the uranium endowment is made before consideration of economic availability of any associated uranium resources.

Uranium hexafluoride (UF6):  A white solid obtained by chemical treatment of U3O8and which forms a vapor at temperatures above 56 degrees Centigrade. UF6 is the form of uranium required for the enrichment process.

Uranium importation:  The actual physical movement of uranium from a location outside the United States to a location inside the United States.

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

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.

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 in active 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 ore:  Rock containing uranium mineralization in concentrations that can be mined economically, typically one to four pounds of U3O8 per ton or 0.05 percent to 0.2 percent U3O8.

Uranium oxide:  Uranium concentrate or yellowcake. Abbreviated as U3O8.

Uranium property:  A specific piece of land with uranium reserves that is held for the ultimate purpose of economically recovering the uranium. The land can be developed for production or undeveloped.

Uranium reserves:  Estimated quantities of uranium in known mineral deposits of such size, grade, and configuration that the uranium could be recovered at or below a specified production cost with currently proven mining and processing technology and under current law and regulations. Reserves are based on direct radiometric and chemical measurements of drill holes and other types of sampling of the deposits. Mineral grades and thickness, spatial relationships, depths below the surface, mining and reclamation methods, distances to milling facilities, and amenability of ores to processing are considered in the evaluation. The amount of uranium in ore that could be exploited within the chosen forward-cost levels are estimated in accordance with conventional engineering practices.

Uranium resource categories (international):  Three categories of uranium resources defined by the international community to reflect differing levels of confidence in the existence of the resources. Reasonably assured resources (RAR), estimated additional resources (EAR), and speculative resources (SR) are described below.

  • Reasonably assured resources (RAR): Uranium that occurs in known mineral deposits of such size, grade, and configuration that it could be recovered within the given production cost ranges, with currently proven mining and processing technology. Estimates of tonnage and grade are based on specific sample data and measurements of the deposits and on knowledge of deposit characteristics. Note: RAR corresponds to DOE's uranium reserves category.
  • Estimated additional resources (EAR): Uranium in addition to RAR that is expected to occur, mostly on the basis of geological evidence, in extensions of well-explored deposits, in little-explored deposits, and in undiscovered deposits believed to exist along well-defined geological trends with known deposits. This uranium can subsequently be recovered within the given cost ranges. Estimates of tonnage and grade are based on available sampling data and on knowledge of the deposit characteristics, as determined in the best-known parts of the deposit or in similar deposits. Note: EAR corresponds to DOE's probable potential resources category.
  • Speculative resources (SR): Uranium in addition to EAR that is thought to exist, mostly on the basis of indirect evidence and geological extrapolations, in deposits discoverable with existing exploration techniques. The location of deposits in this category can generally be specified only as being somewhere within given regions or geological trends. The estimates in this category are less reliable than estimates of RAR and EAR. Note: SR corresponds to the combination of DOE's possible potential resources and speculative potential resources categories.