Uranium extraction from

Uranium Extraction from Ore Leach Liquors. Liquid—Hquid extraction is used as an alternative or as a sequel to ion exchange in the selective removal of uranium [7440-61-1] from ore leach Hquors (7,265,271). These Hquors differ from reprocessing feeds in that they are relatively dilute in uranium and only slightly radioactive, and contain sulfuric acid rather than nitric acid. 

Seawater. The world s oceans contain ca 4 X 10 t of uranium (32). Because the uranium concentration is very low, approximately 3.34 ppm, vast amounts of water would be required to recover significant amount of uranium metal, ie, 10 m of seawater for each metdc ton of U. Significant engineering development and associated environmental concerns have limited the development of an economic means of uranium extraction from seawater (32) (see Ocean RAWMATORiALs). 

Preequilibration of the solvent may be required. In some systems, this cost is minimal, but in others it may be high for example, in uranium extraction from sulfate solutions using tertiary amines, the sulfuric acid preequilibration of the solvent before extraction is a few cents or less per pound of UsOg produced. By comparison, in a TBP-HNO3 system for the recovery of zirconium, the preequilibration costs, using nitric acid, amount to about 50 cents per pound of Zr produced. 

Various processes have been used for uranium extraction from phosphoric acid solution their main features are listed in Table 12.4. The HDEHP-TOPO process is increasingly preferred over others because of the stability of the extractant and the well-understood chemistry of the process. 

The essential ingredients for producing heat in a thermal fission nuclear reactor are the fuel and a moderator. A heat transport system with its coolant is necessary to convey the heat from the reactor to boilers where steam is produced to drive the turbogenerator. The natural materials available for fuel and moderator are uranium ore and water natural uranium extracted from the ore comprises the fissionable isotope uranium-235 and water contains hydrogen which is a good moderator. (Table I)... 

Figure 15 The effect of uranium concentration on uranium extraction from H2S04 by 0.1 M HDEHP in kerosene.106 The curves are labelled with U concentration (g dm-3)...

The early experiments on solvent extraction directly from leached pulp were beset with problems such as losses of solvent in the aqueous phase and the formation of emulsions. The use of mixer-settler, pump mixer, and internal mixer-settler type contactors on a laboratory scale (Gil) has demonstrated the feasibility of uranium extraction from desanded slurries with 5-1. )% solids and from high-density slurries with 48-60% percent solids. The deemulsification rate of a synthetic slurry as a function of the temperature of the system and the pH of the slurries (T12) and the effect of extractant entrainment in the aqueous effluent on solvent extraction of uranium from slurries containing more than 40% solids (E6) have been studied. 

Detailed information on the research carried out in the field of uranium extraction from seawater up to 1984 are given in reviews [ 164, 191-198]. The most intensive investigations are being carried out in Japan in institutes dedicated to uranium recovery firom seawater [196]. 

MacCready, W.L., Wethington, J.A. and Hurst, F.J., Uranium extraction from Florida phosphates. Nucl. Technol. 53 (1981) 344-353. 

Bock, J. and Vallnt, P.L., Uranium extraction from wet process phosphoric acid. A hquid membrane approach. Ind. Eng. Chem. Fund., 1982,21 417 22. 

In view of the anticipated exhaustion of terrestrial uranium reserves in the western world at the beginning of the next century 101), the recovery of uranium from sea water has received much attention over the past three decades 102 U9). First studies on uranium extraction from sea water were carried out as early as 1953 by the Atomic Energy Research Establishment in Harwell (AERE), United Kingdom. Extensive efforts have been made in Japan since the early 1960s from the People s Republic of China activities in this direction have been known since 1970. In the Federal Republic of Germany continuous research on the recovery of uranium from sea water has been in progress since about 1973. Investigations have also been carried out in France, Italy, Soviet Union, Finland, India, and more recently also in the United States and Sweden. 

A comparison of the effect of the structure of phosphate esters on uranium extraction from nitrate media shows that the esters from secondary alcohols give higher uranium distribution coefficients (D s) than those from primary alcohols, phenyl esters extract uranium less strongly than alkyl esters, and benzyl esters are intermediate in extractant strength for uranium (24). 

Sayed, M.S.E. (2003). Uranium extraction from gattar sulfate leach liquor using aliquat-336 in a liquid emulsion membrane process. HydrometaUurgy, 68, 51-6. 

FIGURE 19,4-5 Effect of temperature on mass transfer rate in uranium extraction from wet process phosphoric acid. Redrawn from dela in Hayworth et al.33 and Hunt et al.38... 

Figure 9.17 The effect of complexing agent concentration in the organic extraction phase on the amount of uranium extracted from an aqueous solution.17 (Organic Phase Alamine 336 dissolved in Aromatic 150. Aqueous Phase 0.2% uranium, pH 1.0).

Polonium is a silver-grey, radioactive metal. Discovered by chemist Marie Curie in 1898, polonium was named after her country of origin (Poland). Curie discovered the element while analyzing samples of pitchblende, or uranium ore, from Bohemia. She found that unrefined pitchblende was more radioactive than the uranium extracted from it. Small amounts of polonium and another radioactive element, radium, were later obtained from the refined ore. 

Extraction of metal compounds by SF-CO2 is feasible when they are complexed with organic ligands (7). For example, nitrates of uranium and lanthanides are easily complexable with TBP and solubilities of the complex are very high in supercritical CO2. This method is also applicable to hexavalent uranium extraction from solid UO3 using TTA and TBP in SF-CO2 (6). 

Since UO2 is the most common uranium oxide found in nuclear fuels, uranium extraction from UO2 is indispensable in the nuclear fuel reprocessing and uranium waste treatment. From solid UO2, however, uranium extraction is not possible with this method because TTA nor TBP form complexes with UO2 directly. If we introduce acid homogeneously in SF-CO2, we can expect UO2 dissolution and conversion into U02, which can be complexed with TBP by the charge neutralization as TBP2U02(N03)2. For example, concentrated nitric acid is widely used to dissolve UO2 in aqueous solution forming U02(N03)2. 

Uranium Extraction from Uranium Oxide with a High Pressure Mixture of TBP-HNO3-H2O-CO2... 

Uranium extraction from UO2 has been demonstrated using a high pressure mixture of TBP-HNO3-H2O-CO2 (10). The UO2 powder was prepared by grinding mechanically the UO2 nuclear fuel pellet using a vibrating sample mill (Tl-lOO,... 

Rgure 2 Mass spectrum of uranium extracted from a soil sample. Each mass was counted for a different time. Each peak was counted over a mass range greater than the peak therefore, the edge of the neighboring peaks can be seen in the individual mass scans. 

Wrobicki, J. 1979. Assessment of Feasibility of Uranium Extraction from Phosphates in the Middle East, Written submission read in absentia at the British Sulphur Corporation s Third International Conference on Fertilizers, London, England. 

Ammonium carbonate leaching has been developed specifically for uranium extraction from the ore at Grand Junction, Colorado. The technique and plant resembles that used for sodium carbonate pressure leach. 

The formation of adducts such as [(R3NH)2S04]2-U02S04(H20)3 has also been postulated (Nicol et al. 1987). The mechanism of uranium extraction from sulfate media by amines has been comprehensively reviewed by Mackenzie (2005) and Cattrall and Slater (1973). 

TVEX-TBP Uranium Extraction from Dense Pulps by Using... 

Figure XIX-5 presents the specific long-lived radiotoxicity of spent nuclear fuel within the nuclear fuel cycle as a function of energy produced by the SVBR-75/100 reactors. These calculations show that specific radiotoxicity of the technetium-99, iodine-129 and caesium-135 before the final disposal is 0.014 km /GW(e)/year, without taking into account the losses in reprocessing. It is nearly equal to the specific radiotoxicity of natural uranium extracted from Earth and added to the fuel cycle each year.

The ENHS reactor is FSS. That is, the in-core fissile fuel inventory is kept nearly constant over core life and then recycled as many times as one wishes. The only feed after the initial fuel loading is either depleted uranium, uranium extracted from fuel discharged from LWRs, or natural uranium. 

Singh, H., Vijayalakshmi, R., Mishra, S.L. Gupta, C.K. (2001) Studies on uranium extraction from phosphoric acid using di-nonyl phenyl phosphoric acid-based synergistic mixtures. Hydrometallurgy, 59, 69-76. 

El-Hazek, N.T. El-Sayed, M.S. (2003) Direct uranium extraction from dihydrate and hemi-dihydrate wet process phosphoric acids by liquid emulsion membrane. Journal of Radioanalytical and Nuclear Chemistry, 257 (2), 347-352. 

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