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UNITED STATES MINERAL RESOURCES 



pheric conditions in early Precambrian time. Uran- 

 ium is very mobile in ground and meteoric water 

 systems and reconstitutes into deposits in many 

 kinds of rocks and environments. Uranium forms a 

 great variety of minerals, many of which form rich 

 concentrations, of higher grade than thorium, that 

 are economically attractive. The ultimate resource 

 of thorium, however, is greater than that of 

 uranium. 



URANIUM 



By Warren I. Finch, Arthur P. Butlek, Jr., 

 Frank C. Armstrong, and Albert E. Weissenborn 



ABSTRACT OF CONCLUSIONS 

 Uranium is an important energy resource, and even though 

 the demand for its use in nuclear-powered electrical genera- 

 tors was only moderate in 1972, near-future needs are ex- 

 pected to be very great. In the United States, large exploit- 

 able deposits are found chiefly in sandstone and associated 

 rocks. In other parts of the world, large deposits are mainly 

 in quartz-pebble conglomerate of early Precambrian age and 

 in veins. Domestic resources recoverable at present prices 

 totaled about 273,000 tons of UaOs at the end of 1971, and the 

 total for all countries reporting resources is about 1.6 mil- 

 lion tons of UaOa. These supplies are sufficient to last into 

 the 1980's. Needs beyond 1980 are so great that tremendous 

 efforts in exploration, and research in ore-finding tech- 

 niques, will be required to discover new recoverable re- 

 sources. Identified low-grade paramarginal and submarginal 

 resources in marine phosphorite and black shales and in 

 igneous rocks are very large, but to obtain significant sup- 

 plies of uranium from these sources would require mining 

 and treating vast quantities of rock, disrupting large areas 

 of ground at high unit costs. 



INTRODUCTION 



Uranium is a silvery white metal that consists of 

 the three semistable radioactive isotopes U^^*, U"^, 

 and U"*. It is an important energy source because 

 fission of isotope U^^^ releases large amounts of 

 energy. This readily fissionable nuclide constitutes 

 only about 0.7 percent of natural uranium. The iso- 

 tope U"* makes up most of the remaining 99.3 per- 

 cent and the third, U^^S only about 0.005 percent. 

 U"* is not readily fissionable, but it is fertile ma- 

 terial that under neutron bombardment converts to 

 plutonium-239, which is fissionable. 



Prior to 1942, uranium was used chiefly for color- 

 ing glass and ceramic glazes. An ample supply was 

 obtained by recovering some uranium from ores 

 mined at first for radium and later for vanadium. 

 In 1942, controlled nuclear fission was demonstrated, 

 and uranium had two new and vastly more important 

 uses : as an explosive by the military and as a source 

 of heat to produce steam for generating electricity. 

 With continued development of nuclear reactors to 

 generate electricity, uranium is destined to become 



one of the principal energy sources for the world, 

 for even "in today's light water reactors without 

 Plutonium recycle, in which less than one percent of 

 the total potential heat content is made available, 

 a pound of UaOs produces the heat equivalent of 

 about eight tons of coal" (Johnson, 1972) . 



Military uses for explosives stimulated search for 

 uranium that by 1956 yielded a surplus of that ele- 

 ment. In the 1960's, nuclear reactors for generating 

 electricity were developed from the experimental 

 stage to the commercial stage. By December 1971, 

 domestic nuclear-powered electric plant capacity was 

 about 10 million kw (kilowatts) (nearly 3 percent 

 of the total U.S. electric utility capacity of 357 

 million kw) ; about 45.8 million kw capacity was 

 being built, and about 51.6 million kw was ordered 

 (U.S. Atomic Energy Commission, 1972a). The do- 

 mestic electric power need is growing at a rate of 

 7-8 percent per year, and the nuclear share is ex- 

 pected to grow at a faster and increasing rate, so 

 it is predicted that in the year 2000 nuclear plants 

 will provide about 60 percent of the total electrical 

 power (U.S. Department Interior, 1972). 



Although the demand for electricity generated by 

 nuclear energy is expected to increase significantly 

 for many years, technological developments may 

 ultimately permit a decrease in the amount of ura- 

 nium required to generate the needed electricity. If 

 fast-breeder reactors are developed by the mid- 

 1980's, annual domestic uranium requirements are 

 expected to peak about 1990 at about 100,000 short 

 tons of UaOs, about 10 times the 1972 requirement 

 (solid line, fig. 54), after which they will decline 

 gradually to about the same level as in 1972 as the 

 currently used nonbreeder reactors are phased out 



Figure 54. — Projected domestic annual uranium require- 

 ments, 1972-2010, using light-water reactors (LWR) and 

 high-temperature gas-cooled reactors (HTGR) only, re- 

 lative to changeover to fast-breeder reactors (LMFBR) 

 in 1986 (Johnson, 1972). 



