Uranium, extraction production

Uses of Nitric Acid. The primary use of nitric acid is for the production of ammonium nitrate for fertilizers. A second major use of nitric acid is in the field of explosives. It is also a nitrating agent for aromatic and paraffinic compounds, which are useful intermediates in the dye and explosive industries. It is also used in steel refining and in uranium extraction. 

Table 4. Distribution coefllcients of uranium fission products in pyridine. Extraction from 0.25 M NaOH + 2.0 M Na COj ...

For the extraction of Tc from molybdemun irradiated by neutrons or separated from uranium fission products, inorganic sorbents, especially aliuninum oxide have widely been applied. In preparing a Tc generator from irradiated molybdenum , MoOj is dissolved in cone, nitric acid, the solution is diluted and passed through an aluminum oxide column. The column is then eluted by 0.2 N H2SO4 to extract Tc. If molybdenum is adsorbed by AljOj as molybdatophos-phate instead of molybdate, the exchange capacity of molybdenum increases from... 

Uses Plasticizer for lacquers, plastics, cellulose esters, and vinyl resins heat-exchange liquid carbonless copy paper systems in aircraft hydraulic fluids solvent extraction of metal ions from solution of reactor products uranium extraction and nuclear fuel reprocessing pigment grinding assistant antifoaming agent solvent for nitrocellulose and cellulose acetate. 

The solvent extraction process that uses TBP solutions to recover plutonium and uranium from irradiated nuclear fuels is called Purex (plutonium uranium extraction). The Purex process provides recovery of more than 99% of both uranium and plutonium with excellent decontamination of both elements from fission products. The Purex process is used worldwide to reprocess spent reactor fuel. During the last several decades, many variations of the Purex process have been developed and demonstrated on a plant scale. 

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. 

The major characteristic of technetium is that it is the only element within the 29 transition metal-to-nonmetal elements that is artificially produced as a uranium-fission product in nuclear power plants. It is also the tightest (in atomic weight) of all elements with no stable isotopes. Since all of technetiums isotopes emit harmful radiation, they are stored for some time before being processed by solvent extraction and ion-exchange techniques. The two long-lived radioactive isotopes, Tc-98 and Tc-99, are relatively safe to handle in a well-equipped laboratory. 

In order to make use of thorium as a nuclear resource for power generation, development of efficient separation processes are necessary to recover 233U from irradiated thorium and fission products. The THORium uranium Extraction (THOREX) process has not been commercially used as much as the PUREX process due to lack of exploitation of thorium as an energy resource (157,180). Extensive work carried out at ORNL during the fifties and sixties led to the development of various versions of the THOREX process given in Table 2.6. The stable nature of thorium dioxide poses difficulties in its dissolution in nitric acid. A small amount of fluoride addition to nitric acid is required for the dissolution of more inert thorium (181). 

Recovery of vanadium with peroxygens involves both oxidation and com-plexation. In solution, conversion of lower oxidation states into vanadium(V) allows separation by solvent extraction (Figure 6.18).269 This chemistry can be used for vanadium by-products in uranium extractions. With hydrogen peroxide, vanadium(IV) is not oxidized in acidic solution, but rather in alkaline conditions, e.g. 60 °C at pH 9 (Figure 6.19).270 Use of excess hydrogen peroxide readily forms peroxo complexes and this is of value in selective dissolution of vanadium from secondary sources. 

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. 

In 1869, Mendeleev predicted the existence and certain properties of an element with atomic mass 45, terming it ekaboron within a decade, the Swede L. F. Nilsson and Frenchman P. T. Cleve independently isolated scandium oxide, subsequently preparing various other compounds. There are few ores where scandium is the main element (e.g. thortveitite, a silicate, Sc2Si207, and sterrite, SCPO4 2H2O) so that it is mainly obtained as a by-product from uranium extraction. 

Technical Devices for Uranium Recovery from Seawater The facilities known to exist for uranium extraction are of two types. The first type requires an external energy source. The second uses seawater motion (waves, tides, streams, etc.) as the natural source of energy. In the first type, the rate of energy expenditure per 1 ton of product (uranium or any other microelement with a concentration level in seawater of around 10 g/L) was 3x 10 kWh [229]. 

Macasek F, Rajec P, Kopune R, and Mikulaj V. Membrane extraction in preconcentration of some uranium fission products. Solvent Extr Ion Exch 1984 2 227-252. 

An extraction process for separating actinide elements (principally uranium, U, and plutonium, Pu) from fission products in an aqueous solution of spent fuel rods is illustrated in Figure 5.31. The extraction solvent is 30% tributyl phosphate (TBP) in kerosene. The most extractable of the fission products are zirconium, niobium and ruthenium. Zirconium, Zr, is used herein to represent the fission products. Determine the number of stages required in the wash section and in the extraction section. Determine the percentage of the Pu in the feed which is recovered in the extract product. V denotes the relative volumetric flowrate. 

By calculating the residence times of the various solids in the tank and relating them to their corresponding extraction curves, the total uranium extraction for the entire train of mixers was estimated. The cost of the various mixer options, the production efficiency net result, and the cost of the installation and tank design could be combined to yield the economic optimum for the plant. 

Molybdenum is not stripped from the amine solvent by sodium chloride. If not kept below around 0.03 g MoAiter, it precipitates as a sludge and interferes with uranium extraction. To control molybdenum concentration, a portion of the solvent leaving the uranium stripping section is contacted in a sin e mixer-settler with an aqueous solution of Na2C03 and NH4OR This converts the molybdenum to sodium molybdate, Na2Mo04, and transfers it to the aqueous phase, from which molybdenum is recovered as a by-product. 

Production of power from nuclear reactors involves uranium mining, fuel fabrication, the reactor operations, and storage of wastes. All of these processes may expose humans and the environment to radiation. Uranium production in the United States was 12,300 tons of U3O8 in 1977, primarily from western states, Texas, and Florida. Mining from deep shafts or open pits is the preferred method of uranium extraction, although in Florida it is produced as... 

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