Uranium production from ores

Thorium has been recovered as a by-product of uranium production from ores of the Blind River district in Ontario in which the uranium thorium ratio is 6 1 [C5], In such thorium the Th activity is 3.1 X 6 = 18.6 times the activity of the Th. 

Estimates of speculative lesouices (SR) at 130/kg uianium and those having an unassigned cost range are provided ia Table 4 (23). These resources, which total about 11.28 x 10 t, would be ia addition to the reasonably assured and estimated additional resources. Estimates of uranium resources from unconventional and by-product sources are presented ia Table 5 (24). These resources total about 7 x 10 t for phosphates, 0.013 x 10 t for nonferrous ores, 0.016 x 10 t for carbonates, and 0.014 x 10 t for lignites. These would be ia addition to the reasonably assured resources, estimated additional resources, and the speculative resources (24). 

Nonferrous Metal Production. Nonferrous metal production, which includes the leaching of copper and uranium ores with sulfuric acid, accounts for about 6% of U.S. sulfur consumption and probably about the same in other developed countries. In the case of copper, sulfuric acid is used for the extraction of the metal from deposits, mine dumps, and wastes, in which the copper contents are too low to justify concentration by conventional flotation techniques or the recovery of copper from ores containing copper carbonate and siUcate minerals that caimot be readily treated by flotation (qv) processes. The sulfuric acid required for copper leaching is usually the by-product acid produced by copper smelters (see Metallurgy, extractive Minerals RECOVERY AND PROCESSING). 

Sulfuric acid is the most commonly used reagent for the recovery of uranium from ores, and vanadium is often recovered as a coproduct. The sulfuric acid used is either the by-product sulfuric acid produced at smelters or sulfuric acid produced from elemental sulfur. 

Ore Processing. Vanadium is recovered domestically as a principal mine product, as a coproduct or by-product from uranium—vanadium ores, and from ferrophosphoms as a by-product in the production of elemental phosphoms. In Canada, it is recovered from cmde-oil residues and in the Repubhc of South Africa as a by-product of titaniferous magnetite. Whatever the source, however, the first stage in ore processing is the production of an oxide concentrate. 

World molybdenum production has increased from about 90 metric tons in 1900 — half from Australia and Norway, half from the United States — to 136 tons in 1906, 1364 in 1932 (an order of magnitude increase in 26 years), 10,909 in 1946, and 91,000 tons in 1973. Through the years, molybdenum has been produced in about 30 countries. In 1973, about 60% of the worldwide production was from the United States, 15% from Canada, 15% from the U.S.S.R. and China combined, and 10% from other nations — Chile, Japan, Korea, Norway, and Mexico (King et al. 1973). By 1979, the United States produced about 62% of the world production of 103,000 metric tons, and exported about half, chiefly to western Europe and Japan other major producers in 1979 were Canada, Chile, and the U.S.S.R. (Kummer 1980). In the United States, only three mines in Colorado account for almost 70% of domestic production. Other active molybdenum mining sites in North America are in Arizona, Nevada, New Mexico, Utah, and California molybdenum reserves have also been proven in Idaho, Alaska, Pennsylvania, and British Columbia (Kummer 1980). About 65% of domestic molybdenum is recovered from ores rich in molybdenum the rest is a byproduct from ores of copper, tungsten, and uranium (Chappell et al. 1979). 

Besides the conventional uranium resources, there are also the so-called unconventional uranium resources , which are defined as deposits with very low uranium content, from which uranium is typically only recoverable as a minor by-product. These unconventional uranium resources are obtained from the extraction of phosphates, non-ferrous ores and carbonatites, as well as black schist and lignite. It has to be noted that the distinction between conventional and unconventional resources is not entirely clear cut, but is, instead, somewhat transitional. 

High-grade pitchblende ores are leached with nitric acid to recover uranium. Extraction of uranium from nitrate solutions is usually performed with TBP. TBP-based solvents are used in several areas of the nuclear industry, especially for reprocessing of spent nuclear fuels and for refining the uranium product of the Amex and Dapex processes. Extraction of uranium by TBP solvents is described in sections 12.3.4 and 12.5. 

Large-scale winning of copper by acidic leaching of copper ores sometimes results in waste solutions containing appreciable amounts of uranium. The uranium bearing aqueous raffinate from copper extraction is usually a dilute sulfuric acid solution. Uranium can be recovered using the same technique as described in section 12.3.1. A typical example is uranium production at the Olympic Dam mine in Australia, where the copper ore bodies are estimated to contain a total of over a million metric tons of uranium. 

Patronite. An important commercial deposit of vanadium is the patronite of Peru, an impure sulfide containing free sulfur. This ore was first found in 1905 at Minasragra near Cerro de Pasco, Peru, 16,000 feet above sea level, and was named for its discoverer, Senor Antenor Rizo-Patron (77, 78). Vanadium is also obtained as a by-product from the exploitation of Colorado camotite for radium and uranium (77). 

Viewed in the context of the actinide lifespan, the nuclear fuel cycle involves the diversion of actinides from their natural decay sequence into an accelerated fission decay sequence. The radioactive by-products of this energy producing process will themselves ultimately decay but along quite different pathways. Coordination chemistry plays a role at various stages in this diversionary process, the most prominent being in the extraction of actinides from ore concentrate and the reprocessing of irradiated fuel. However, before considering these topics in detail it is appropriate to consider briefly the vital role played by coordination chemistry in the formation of uranium ore deposits. 

In the first level of the hierarchy, radioactive waste that arises from operations of the nuclear fuel cycle (i.e., from processing of uranium or thorium ores and production of nuclear fuel, any uses of nuclear reactors, and subsequent utilization of radioactive material used or produced in reactors) is distinguished from radioactive waste that arises from any other source or practice. The latter type of waste is referred to as NARM (naturally occurring and accelerator-produced radioactive material), which includes any radioactive material produced in an accelerator and NORM [naturally occurring radioactive material not subject to regulation under the Atomic Energy Act (AEA)]. 

Figure 6.19 Extraction of vanadium by-products from uranium ores using alkaline hydrogen peroxide.

When Mendeleev produced his original Periodic Table in 1869, he left a space for a metallic element of atomic mass 44 preceding yttrium. The first fairly pure scandium compounds were isolated by Cleve in 1879, but it was not until 1937 that the element itself was isolated. Although a relatively abundant element, it is fairly evenly distributed in the earth s crust and has no important ores, though it is the main component of the rare ore thortveitite (Sc2Si207), thus being relatively expensive. In fact, it is mainly obtained as a by-product from uranium extraction. 

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