Uranium from ores

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. 

Another example of a cost-effective liquid-liquid extraction process is the one used for recoveiw of uranium from ore leach liquors (Fig. 15-3). In this case the solvents, alkyl phosphates in kerosine, are recovered by liquid-liquid extraclion using a strip solution, and the... 

Table 12.1 Commercial Processes for Recovery of Uranium from Ores... 

Solvent extraction plays an important role in many commercial processes for the extraction of uranium from ore. In this case, the radioactivity levels are quite low compared with those in spent fuel extraction. The liquors from hy-drometallurgical leaching of ores are typically fairly dilute in uranium (0.5-5 g/L) and contain iron and other metals in solution. Depending on conditions, solvent extraction or ion exchange may be used to separate and concentrate the uranium from the leach liquor. 

It should be noted that breeders would not reduce the demand for uranium ore for many decades because several LWR and/or HWR converters (which produce fissionable material, but less than consumption) are required during the run-in of a breeder cycle to equilibrium. The doubling time of a breeder (the time required for the breeder to produce sufficient fissionable material to start up a second breeder reactor) might be a significant part of its operating life. Furthermore, natural uranium will be required for the thorium cycle, if it is used, and for startup of the fusion cycle. The tritium for the fusion cycle will be made in nuclear reactors, as it now is for nuclear weapons. The nuclear industry will always be dependent on a continuing supply of uranium from ore. 

Burners vs. breeders Burners depend on uranium from ore but may recycle the residual fissionable material from the spent fuel to reduce the ore requirement. Breeders produce more fissionable material than they consume by converting either uranium-238 into plutonium-239 or thorium-232 into uranium-233. The breeders depend on the plutonium-239 or uranium-233 from the burners to bring them into equilibrium, and this may take 30 years. 

When PWRs and CANDUs are compared on the basis of uranium utilization, the CANDU requires 19 percent less uranium from ore on a per kWhr basis (see Table 21.18). As there is now an abundance of low-cost uranium from ore and enrichment service, the electric utilities continue to favor the PWR and BWR types. Operating experience with graphite reactors in England, France, and Russia also has been generally satisfactory. However, the graphite moderator represents a large inventory of combustible material, which contributed significantly to the severity... 

Two engineering system demonstrations were performed to reduce the uranium-from-ore requirements of LWRs recycle of the plutonium and conversion to the thorium-uranium cycle to achieve thermal breeding. The demonstration phase of the plutonium recycle development was carried out in seven power reactors. Several LWRs originally were started up on the thorium-uranium cycle, and a light... 

Acid leaching (especially sulfuric acid) used to extract uranium from ore... 

GreyC. 1993. Uranium From ore to concentrate. The Nuclear Engineer 34(l) 3-9. 

Canada and Australia are the world s largest producers of uranium. All Canadian production is from rich deposits in the Athabasca basin of northern Saskatchewan among those is the McArthur River mine, which has the world s largest high-grade deposit, estimated at 1.52 X 10 t of uranium from ore grading 15-18% uranium. These unconformity -type Saskatchewan deposits, which are also the principal deposit-type for Australian uranium production, contain mainly uraninite [UO2] with associated coffinite [U(Si04)i jc(0H)4j and brannerite [(U,Ca,Y,Ce)(Ti,Fe)206] (Plant et al, 1999). The chief uses of uranium are in nuclear power plants and weaponry. 

Separation of thorium and uranium from ore samples using anion-exchange column (Dowex 1-X8) has been investigated [1]. Thorium was eluted with 6 M HCl. 

Maoner, j. E. and Bailes, R. H. Recovery of uranium from ores by direct leaching with organic solvents. Proc. 2nd Int. Conf. on the Peaceful Uses of Atomic Energy, Geneva, 1958, Paper 496. 

Jonke, A. A. et al. Fluidization techniques in producing refined uranium from ore concentrates. Industr. Engng. Chem. 50, No. 12, 1739 (Dec. 1958). 

The main application for this technique is in a system where the liquid feed contains fine solids that would block a fixed bed or tend to float resin out of a fluidized bed owing to the high density or viscosity of the feed. The process is used for the recovery of uranium from ore deposits containii a high proportion of clay minerals. Such ores produce a slimy pulp that is expensive to filter and thus there is an incemive to extract dissolved metal directly from the leach pulp. A number of plants were constructed in the 1950 in the United States on this principle—known as resin-in-pulp (RIP) operations. The simplest possible method of agitation, namely, to inject air into the base of the mixing tanks, was used in the early plants. ... 

The recovery of uranium from ores uses SX to reject impurities and concentrate the uranium in solution so that it can be economically recovered (Gupta and Singh 2003 Lloyd 1983). The choice of extractant depends on the lixiviant used in the upstream leaching operation, which, in turn, depends on the type of ore in which the uranium is found. Most nranium-bearing ores are readily leached in sulfuric acid and the uraninm is recovered by SX using amines or dialkylorganophosphorus acids. Phosphate ores (snch as those in Florida) are leached in a mixture of sulfuric and phosphoric acids or in phosphoric acid alone. Hot nitric acid has also been used as a lixiviant for nraninm ores (as at Phalaborwa, South Africa). The two common extraction systems for the recovery of uranium(VI) from sulfate leach liquors are compared in Table 5.6. 

---