Distribution of uranium

Radiometric ore sorting has been used successfully for some uranium ores because uranium minerals emit gamma rays which may be detected by a scintillation counter (2). In this appHcation, the distribution of uranium is such that a large fraction of the ore containing less than some specified cut-off grade can be discarded with tittle loss of uranium values. Radioactivity can also be induced in certain minerals, eg, boron and beryllium ores, by bombarding with neutrons or gamma rays. 

Geochemical Nature and Types of Deposits. The cmst of the earth contains approximately 2—3 ppm uranium. AlkaHc igneous rock tends to be more uraniferous than basic and ferromagnesian igneous rocks (10). Elemental uranium oxidizes readily. The solubiHty and distribution of uranium in rocks and ore deposits depend primarily on valence state. The hexavalent uranium ion is highly soluble, the tetravalent ion relatively insoluble. Uraninite, the most common mineral in uranium deposits, contains the tetravalent ion (II). 

Radon gas is formed in the process of radioactive decay of uranium. The distribution of naturally occurring radon follows the distribution of uranium in geological formations. Elevated levels have been observed in certain granite-type minerals. Residences built in these areas have the potential for elevated indoor concentrations of radon from radon gas entering through cracks and crevices and from outgassing from well water. 

Gvirtzman G, Friedman GM, Miller DS (1973) Control and distribution of uranium in coral reefs during diagenesis. J Sed Petrol 43 985-997... 

Gueniot B, Munier-Lamy C, Berthelin J (1988b) Geochemical behavior of Uranium in soils, part 11 Distribution of uranium in hydromorphic soils and soil sequences. Application for suificial prospecting. J Geochem Explor 31 39-55... 

Moreira-Nordemann LM, Sieffermann G (1979) Distribution of uranium in soil profiles of Bahia state, Brazil. Soil Science 127 275-280... 

Vigier N, Bourdon B, Turner S, Allegre CJ (2001) Erosion timescales derived from U-decay series measurements in rivers. Earth Planet Sci Lett 193 549-563 von Gunten HR, Roessler E, Lowson RT, Reid PD, Short SA (1999) Distribution of uranium- and thorium series radionuclides in mineral phases of a weathered lateritic transect of a uranium ore body. Chem Geol 160 225-240... 

The D-A model predicts the distribution of uranium and U-series isotopes across a bone section (Figs. 3 and 4). Under constant conditions Uranium is diffusing from the inner and outer surfaces of the bone, giving a u-shaped Uranium concentration profile that gradually flattens with time to a uniform uranium distribution when the bone reaches equilibrium with the uranium in the groundwater. Because the uranium is equilibrating with the outer portions of the bone section first, closed system U-series dates approach the true age of the bone towards the surfaces, but are underestimated towards the centre. Further details of the D-A model are given in the Appendix. 

Exposure Levels in Humans. Although some data on the levels of americium in human tissues exposed to natural background levels (food, water, and air) are available, few measurements have been made on the americium content in human tissues. The principal source of information about occupationally exposed individuals is the U.S. Transuranium and Uranium Registries (USTUR) Tissue Program and database, established to document levels and distribution of uranium and transuranium isotopes in human tissues for occupationally exposed workers (USTUR 1999). Several major database files are available. 

Figure 3. Fission track map of the distribution of uranium in a stalagmite from Grotte Valerie, Nahanni National Park, N.W.T., Canada.

McConnell, M.A., V.M.S. Ramanujam, N.W. Alcock, G.J. Gabehart, and W.W. Au. 1998. Distribution of uranium-238 in environmental samples from a residential area impacted by mining and milling activities. Environ. Toxicol. Client. 17 841-850. 

Figure 4.5 illustrates the distribution of uranium resources among the ten major countries. Approximately 90% of the resources in all RAR and IR categories are to be found in those ten countries, with the leading ones being Australia, Kazakhstan, Canada and South Africa. 

As predicted from the nuciear size effect on the distribution of uranium isotopes, Steriing et al. (2007) and Weyer et al. (2008) report a totai variation of 1.5 %o in the 238 j/2S5 j pg jQg decreasing in the order from biack shaies > basaits, > seawater, > banded iron formations (BiFs). The biack shaies reflect preferentiai reduction by organic matter of U from seawater. 

McNeal, J.M., Lee, D.E., Millard, Jr. FI.T. 1981. The distribution of uranium and thorium in granitic rocks of the basin and range province. Western United States. Journal of Geochemical Exploration, 14, 25-40. 

Fig. 4. Relation between clays and coffinite at Cigar Lake (a, b, c, e and f) and at Oklo (d) (a) to (d) uranium progressively invades the clay phase until complete replacement in (d) (e) coffinite replacing a chlorite mineral (precipitation of coffinite around a chlorite flake) (f) map of the distribution of uranium corresponding to the rectangle in (e). (C = clay mineral Co = coffinite.)...

Neglecting activity coefficients, the coefficient for the distribution of uranium between the organic and aqueous phases is written as... 

Todd, J.F., Elsinger, R.J., and Moore, W.S. (1988) The distributions of uranium, radium, and thorium isotopes in two anoxic fjords Framvaren Fjord (Norway) and Saanich Inlet (British Columbia). Mar. Chem. 23, 393—415. 

Ivanovich, M. et al., Natural analogue study of the distribution of uranium series radionuclides between the colloid and solute phases in the hydrogeological system of the Koongarra uranium deposit, Australia, United Kingdom Atomic Energy Authority Doc. No. AERE-R 12975, Oxfordshire, U.K., Jan. 1988. 

Once absorbed into the system circulation, uranium undergoes chemical transformations to complex with the blood. Uranium in the trivalent form will oxidize to the hexavalent species to form uranyl ions, which form soluble complexes with bicarbonate, citrate, or proteins in the plasma (Chevari and Likhner, 1968 Cooper et al, 1982 Stevens et al, 1980). The distribution of uranium in the blood is approximately 47% complexed with bicarbonate in plasma, 32% bound to plasma proteins, and 20% bound to erythrocytes (Chevari and Likhner, 1968, 1969). 

Environmental distribution of uranium and other frace elements at selected Kosovo sites. Chemosphere 56 861-5. 

Pelhnar, T.C., Fuciarelli, A.F., Ejnik, J.W., Hamilton, M., Hogan, J., Strocko, S., Emond, C., Mottaz, H.M., Landauer, M.R. (1999a). Distribution of uranium in rats implanted with depleted uranium pellets. Toxicol. Sci. 49 29-39. 

In some ways, the skeletal behavior of uranium is quantitatively similar to that of alkaline earths. It is known that the uranyl ion (U02 ) exchanges with Ca + on the surfaces of bone mineral crystals, although it does not participate in crystal formation or enter existing crystals. The early distribution of uranium in different parts of the skeleton is similar to that of calcium. Uranium initially deposits on all bone surfaces but is most highly concentrated in areas of growth. Depending on the microscopic structure of the bone of each species, uranium on bone surfaces may gradually diffuse into bone volume such... 

No studies were located regarding distribution of uranium after dermal exposure in humans or animals. 

Intravenously injected uranium is rapidly taken up by the tissues or excreted in the urine (ICRP 1995). Typically, 25% of intravenously injected uranium (as uranyl nitrate) remained in blood of human subjects after 5 minutes, 5% after 5 hours, 1% after 20 hours, and less than 0.5% after 100 hours although inter-subject variation was high (Bassett et al. 1948 Bernard and Struxness 1957). Measurements of systemic distribution of uranium made at autopsy in one terminally ill human given a single intravenous injection of uranium indicated that the skeleton, kidneys, and other soft tissues after 2.5 hours contained about 10, 14, and 6%, respectively, of the dose. Distribution data taken from another human subject 18 hours after a single intravenous injection uranium showed that the bones, kidneys, and other soft tissues contained about 4-13%, 6%, and 4%, respectively, of the amount injected. At 566 days post-injection, uranium distribution in the skeleton, kidneys, and other soft tissues declined to about 1.4, 0.3, and 0.3%, respectively. 

The distribution of uranium metal implanted in muscle has been investigated in rats (Pellmar et al. 

Bioavailability from Environmental Media. The absorption and distribution of uranium as a... 

Cowart JB, Burnett WC. 1994. The distribution of uranium and thorium decay-series radionuclides in the environment- A Review. J Environ Qual 23 651-662. 

Morishima H, Koga T, Kawai H, et al. 1977. Studies on the movemnent of distribution of uranium in the environments-distribution of uranium in agricultural products. J Radiat Res 18 139-150. 

Pellmar TC, Fuciarelli AF, Ejnik JW et al. 1999a. Distribution of uranium in rats implanted with depleted uranium pellets. Toxicol Sci 49 29-39. 

Knowledge with respect to speciation and distribution of uranium in the ocean... 

Equilibrium distributions of uranium species by the model calculation are shown in Figures 1 and 2. Figure 1 is the calculated result of U speciation under 0% CO2 condition. Uranium almost exists as U02 at pHs 5.5 or below. Uranium also exists as a form of UO2OH and (U02)3(0H)s between pH 5 and 6.5. Uranium is precipitated as a form of 0 -U02<0H)2(s) between pH 6 and 9. The distribution percentage of the solid-phase is over 80%. Uranium exists as U02(0H)3 at pHs 9 or above. The dominant solid-phase is uranyl hydroxide because of the CO2 free condition. The distribution of U species under air condition is shown in Figure 2. Uranium exists as U02 at pHs 5.5 or below and as U020H and (U02)3(0H)s between pH 5 and 6.5. Uranium is precipitated as species of 0 -U02(0H)2(s) between 6 and 7.5. The maximum percentage of the solid-phase is 54%. 

Figure 1. Calculated distribution of uranium species in the aqueous and solid-phase of IxlO M solution equilibrated under 0% CO2 condition.

Conversion of a-U03 to MUsOio involves the replacement of one-fourth of the uranium atoms by divalent metal ions. As a result the oxygen-metal ratio is decreased to 2.5 1, and oxygen Vacancies are created in the chains or in the sheets. Ippolitova et al. reported that the a dimension of the true triuranate cell is twice that of a-U03, owing to the ordered distribution of uranium and zinc atoms in the lattice, and that the true c dimension of ZnU30io is four times that of a-U03... 

Jaupart C., Sclater J. G., and Simmons G. (1981) Heat flow smdies constraints on the distribution of uranium, thorium and potassium in the continental crust. Earth Planet. Sci. Lett. 52, 328-344. 

WoUenberg H. A. and Flexser S. (1985) The distribution of uranium and thorium in the Stripa quartz monzonite, Sweden. Uranium , 155-167. 

Ivanovich M., Duerden P., Payne T., Nightingale T., Long-worth G., Wilkins M.A., Hasler S. E., Edgehill R. B., Cockayne D. J., and Davey B. G. (1988) Natural analogue study of the distribution of uranium series radionuclides between colloid and solute phases in hydrological systems. DOE report AERE-R. 12975/DOE/RW/88.076. 

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