Uranium economic importance

Depending upon lithologic and structural relationship with host rocks, mineralogy, attendant alteration, paragenesis and spatial and temporal constraints, the uranium resources of the world can be assigned to the 15 main categories of uranium ore deposits. They have been shown numerically numbered in sequence in the order of their approximate economic significance in Table 1.18. At present, only 7 can be said to be economically important (see Table 1.19) and these account for more than 95% of the world resources of ura-... 

Strontium (0.02% of lithosphere) occurs as strontianite, SrCOg, and celestite, SrS04. The metal which has the c.c.p. structure is without economic importance except in pyrotechnics. The radioactive strontium-90 is long-lived and, being easily assimilated and incorporated in bone, is a dangerous product of uranium fission. 

Thorium carbides (ThC, ThC2) and uranium carbides (UC, UC2) exhibit metallic properties, but in other properties differ significantly from the carbides of the subgroups of the IVth, Vth and Vlth groups of the periodic table. Their hardnesses are substantially lower (see Table 5.6-1), they are pyrophoric and are easily hydrolyzed in water or weak aeids. Their only economic importance is as carbidie fuels in nuelear technology, particularly for high temperature and breeder reactors which are currently in the evaluation phase. 

The black shale of the Chattanooga Formation in Tennessee is an example of a large low-grade resource of uranium. The mineralized portion of this Devonian. shale occupies. several counties, but mineralized horizons tens of metres thick average only about 0.0. % U,0,(. For the mo.st part, rocks of this type are not of economic importance, unless political considerations dictate otherwise. 

Sedimentary marine phosphorites are composed principally of phosphatic minerals, and many contain significant amounts of disseminated uranium. These phosphorites have been classified as either miogeosynclinal or platform types. Four additional types that are low in uranium and of little economic importance are residual phosphorites, phosphatized rock, river pebble deposits and guano. 

Uranium mineralization is present in all these different geological provinces, but its economic importance and the geological types of occurrence vary considerably from one geostructural unit to the next. 

Metal compounds, particularly compounds of the heavy metals, have a history of importance as antimicrobial agents. Because of regulations regarding economic poisons in the environment they are no longer widely used in this appHcation. Mercury, lead, cadmium, uranium, and other metals have been imphcated in cases of poisoning that resulted in government response. The metals whose compounds have been of primary interest as antimicrobials are mercury, silver, and copper. 

As in the case of igneous processes, the sedimentary processes of rock formation lead to the formation economic mineral deposits. Many valuable mineral deposits of iron, manganese, copper, phosphorus, sulfur, zirconium, the rare Earths, uranium and vanadium owe their origin to sedimentary processes. Some of these constitute special types of sedimentary rocks, while others form important constituents of sedimentary rocks. 

Nash, J.T., Granger, H.C., Adams, S.S. 1981 Geology and concepts of genesis of important types of uranium deposits. Economic Geology, 75 Anniversary Volume, 63-116. 

Abstract strong commodity prices in the last few years have led to a remarkable renaissance of uranium exploration in Labrador, focused in a complex and geologically diverse region known as the Central Mineral Belt (CMB). Potentially economic epigenetic U deposits are mostly hosted by supracrustal rocks of Paleoproterozoic and Mesoproterozoic age, and are difficult to place in the traditional pantheon of uranium deposit types. Recent exploration work implies that structural controls are important in some examples, but the relationships between mineralization and deformation remain far from clear. Geochronological data imply at least three periods of uranium mineralization between 1900 and 1650 Ma. It seems likely that the Labrador CMB represents a region in which U (and other lithophile elements) were repeatedly and sequentially concentrated by hydrothermal processes. The current exploration boom lends impetus for systematic research studies that may ultimately lead to refined genetic models that may be applicable elsewhere. 

The production of power from controlled nuclear fission of heavy elements is the most important technical application of nuclear reactions at the present time. This is so because the world s reserves of energy in the nuclear fuels uranium and thorium greatly exceed the energy reserves in all the coal, oil, and gas in the world [HI], because the energy of nuclear fuels is in a form far more intense and concentrated than in conventional fuels, and because in many parts of the world power can be produced as economically from nuclear fission as from the combustion of conventional fuels. 

As the oceans of the world contain about 10 kg of deuterium and resources of lithium minerals are of comparable magnitude, it is clear that if this fusion reaction could be utilized in a practical nuclear reactor, the world s energy resources would be enormously increased. Although intensive research is being conducted on confinement of thermonuclear plasmas, it is not yet clear whether a practical and economic fusion reactor can be developed. If fusion does become practical, isotope separation processes for extracting deuterium from natural water and for concentrating from natural lithium will become of importance comparable to the separation of U from natural uranium. 

The study of gas transport in membranes has been actively pursued for over 100 years. This extensive research resulted in the development of good theories on single gas transport in polymers and other membranes. The practical use of membranes to separate gas mixtures is, however, much more recent. One well-known application has been the separation of uranium isotopes for nuclear weapon production. With few exceptions, no new, large scale applications were introduced until the late 1970 s when polymer membranes were developed of sufficient permeability and selectivity to enable their economical industrial use. Since this development is so recent, gas separations by membranes are still less well-known and their use less widespread than other membrane applications such as reverse osmosis, ultrafiltration and microfiltration. In excellent reviews on gas transport in polymers as recent as 1983, no mention was made of the important developments of the last few years. For this reason, this chapter will concentrate on the more recent aspects of gas separation by membranes. Naturally, many of the examples cited will be from our own experience, but the general underlying principles are applicable to many membrane based gas separating systems. 

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