NUCLEAR FUEL RESERVES

Lightwater reactors, the primary type of nuclear power reactor operated throughout the world, are fueled with uranium dioxide [1344-57-6] UO2 miched from the naturally occurring concentration of 0.71% uranium-235 [15117-96-17, to approximately 3% (1). As of this writing all civiUan nuclear 

Department of Energy (DOE) and the NEA/IAEA employ similar terms to classify uranium resources, as (7) reasonably assured, estimated additional (EA), or speculative. The NEA/IAEA divides the estimated additional resources into two types, EAR-I and EAR-II, describing known resources and undiscovered ones, respectively (8). 

Geochemical Nature and Types of Deposits. The cmst of the earth contains approximately 2—3 ppm uranium. AlkaHc igneous rock tends to be more uraniferous than basic and ferromagnesian igneous rocks (10). Elemental uranium oxidizes readily. The solubiHty and distribution of uranium in rocks and ore deposits depend primarily on valence state. The hexavalent uranium ion is highly soluble, the tetravalent ion relatively insoluble. Uraninite, the most common mineral in uranium deposits, contains the tetravalent ion (II). 

Unconformity-Related Deposits. Deposits of the unconformity-related type occur spatially close to significant unconformities. These deposits usually developed during the period about 1800—800 million years ago in intracratonic basins. Deposits also developed during Phanerozoic time. Examples of unconformity-related deposits include the ore bodies at Cluff Lake, Key Lake, and Rabbit Lake in northern Saskatchewan, Canada, and those in the Alligator Rivers area in northern AustraHa (12). 

Quartz-Pebble Conglomerate Deposits. Known quartz-pebble conglomerate ores are restricted to a specific period of geologic time. These ore types occur in basal Lower Proterozoic beds unconformably situated above Archaean basement rocks composed of granitic and metamorphic strata. A number of commercial deposits are located in Canada and South Africa. Some subeconomic occurrences have been reported in Brazil and India 

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Nuclear Fuel Reserves" under "Nuclear Reactors" in ECT3rd ed., VoL 16, pp. 143—150, byj. A. Patterson, U.S. Department of Energy. 

Several components are required in the practical appHcation of nuclear reactors (1 5). The first and most vital component of a nuclear reactor is the fuel, which is usually uranium slightly enriched in uranium-235 [15117-96-1] to approximately 3%, in contrast to natural uranium which has 0.72% Less commonly, reactors are fueled with plutonium produced by neutron absorption in uranium-238 [24678-82-8]. Even more rare are reactors fueled with uranium-233 [13968-55-3] produced by neutron absorption in thorium-232 (see Nuclear reactors, nuclear fuel reserves). The chemical form of the reactor fuel typically is uranium dioxide, UO2, but uranium metal and other compounds have been used, including sulfates, siUcides, nitrates, carbides, and molten salts. 

Uranium oxide [1344-57-6] from mills is converted into uranium hexafluoride [7783-81-5] FJF, for use in gaseous diffusion isotope separation plants (see Diffusion separation methods). The wastes from these operations are only slightly radioactive. Both uranium-235 and uranium-238 have long half-Hves, 7.08 x 10 and 4.46 x 10 yr, respectively. Uranium enriched to around 3 wt % is shipped to a reactor fuel fabrication plant (see Nuclear REACTORS, NUCLEAR FUEL reserves). There conversion to uranium dioxide is foUowed by peUet formation, sintering, and placement in tubes to form fuel rods. The rods are put in bundles to form fuel assembHes. Despite active recycling (qv), some low activity wastes are produced. 

Nuclear fuel cycle, 77 545-547 safety principles and, 17 546-547 Nuclear fuel reprocessing, 10 789-790 Nuclear fuel reserves, 17 518-530 alternative sources of, 17 527 economic aspects of, 17 526-527 toxicology of uranium, 17 528-529 uranium mineral resources, 17 518-521, 522-525... 

Apatite - [COAL] (Vol 6) - [COLORANTS FORCERAMICS] (Vol 6) - [FERTILIZERS] (Vol 10) -magnetic intensity [SEPARATION - MAGNETIC SEPARATION] (Vol 21) -uranium m [NUCLEAR REACTORS - NUCLEAR FUEL RESERVES] (Vol 17)... 

Monzomte -uranium m [NUCLEAE REACTORS - NUCLEAR FUEL RESERVES] (Vol 17)... 

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