Solid wastes uranium mining

The amount of solid waste depends on the method of uranium ore exploration. By deep mining, each ton of ore is supplemented by 0.2-0.3 tons of waste ores, and by open pit mining, per 1 ton of ore up to 8-10 tons of excavation materials are produced. Moreover, uranium ores contain from 5% up to 25-30% of waste ores, which are deposited as mine tails. 

The uranium mine tails contain the equal masses of water and solids. Furthermore the treatment of each ton of uranium ore is accompanied by receiving about 3 tons of rafinate, and finally the treatment of 1 ton of uranium ore gives about 4 tons of liquid wastes of different chemical composition, which in turn depends on the treatment technology. 

The relative area of mine solid waste tails (per 100,000 M3 of rock mass) is 0.7-0.8 of the total area. On average, the disturbed areas of uranium ore exploration site are partitioned as follows 32.3% of disturbed land is occupied by dumps, 27.2%, by pits, 20.3%, by industrial areas, 13.3%, by tails, and about 10%, by other types of land disturbance. 

Solid waste comes from the mining and milling of uranium ore and the sludge from spent fuel storage. It also includes contaminated equipment and structures. High-level solid waste includes the hulls from the dissolving of spent fuel, ion exchange resin, and the like. 

At the mill, usually located close to the mine, the ore is crushed and ground to a fine slurry. Sulfuric acid, in which uranium is soluble, is used to leach the product from the bulk material. The residue, consisting of undissolved solids (waste rock) is referred to as the tailings. This material contains most of the radioactivity including radium and toxic materials such as heavy... 

Several wastes important to DOE are excluded from the RCRA definition of solid wastes (40 CFR 261.2). They include source, special nuclear, or byproduct material as defined by the AEA [Section 11(e), (z), (aa)] waste from extraction, beneficiation, and processing of ores and minerals, including overburden from mining uranium ores utility wastes oil and gas drilling muds and brines and some wastes that are reused or recycled. 

In some instances, the source of radon is in wastes from uranium mining or phosphate production. In most cases, it is emitted by the radioactive decay of present in small amounts in rocks and soils. Because radon is a gas, it readily passes through air passages in the body and is breathed in and out. The product formed when a Rn atom gives up an a particle is the isotope polonium-218, which also emits a particles. Unlike radon, polonium is a solid. Health hazards posed by radon seem to be from Po and other radioactive decay products becoming attached to dust particles in the air and then being breathed into the lungs. 

Fig. 1. Schematic flowsheet of uranium processing (acid leach and ion exchange) operation. Numbers refer to the numbers that appear in the boxes on the flowsheet. Operations (3), (6), (9), and (11) may be done by thickening or filtration. Most often, thickeners are used, followed by filters. The pH of the leach slurry <4) is elevated to reduce its corrosive effect and to improve the ion-exchange operation on the uranium liquor subsequently separated, In tile ion exchange operation (7), resin contained in closed columns is alternately loaded with uranium and then eluted. The resin adsorbs the complex anions, such as UC fSO 4-. in which the uranium is present in the leach solution. Ammonium nitrate is nsed for elution, obtained by recycling the uranium filtrate liquor after pH adjustment. Iron adsoibed with the uranium is eluted with it. Iron separation operation (8) is needed inasmuch as the iron hydroxide slurry is heavily contaminated with calcium sulfate and coprecipitated uranium salts. Therefore, the slurry is recycled to the watering stage (3). Washed solids from 1,6). the waste barren liquor from (7), and the uranium filtrate from (11) are combined. The pH is elevated to 7.5 by adding lime slurry before the mixture is pumped to the tailings disposal area. (Rio Algom Mines Limited, Toronto)...

Data from in-situ leach mining and restoration of roll-front uranium deposits also provide information on the potential mobility of the waste if oxidizing ground water should enter the repository. Uranium solids probably will be initially very soluble in carbonate ground water however, as reducing conditions are re-established through water/rock interactions, the uranium will reprecipitate and the amount of uranium in solution will again equilibrate with the reduced uranium minerals ... 

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