Uranium distribution behavior

Uranium extraction by TBP may in some cases become poorer in the presence of other extractable components because of depletion of free TBP by components other than uranium. Such behavior is illustrated by the U02(N03)2-HN03-TBP system analyzed above, as shown by the data [Ml ] in Fig. 4.7 for the distribution coefficient of uranium as affected by nitric acid concentration. For acid concentration less than about 5 M, the uranium distribution coefficient is greater the higher the acid concentration, because of the salting effect of nitrate ion from the acid. At acid concentrations greater than about S M, increasing acid concentration inhibits uranium extraction, because enough nitric acid has been extracted so that less free TBP is available to form the extractable complex with uranium. Smilar effects have been observed in the extraction of other elements with TBP [Ml]. 

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... 

Martin JM, Nijampurkar V, Salvation F (1978b) Uranium anti Thorium isotope behavior in estuarine systems. In Biogeochemistry of estuarine sediments. UNESCO, p 111-127 Mathieu D, Bemat M, Nahon D (1995) Short-lived U and Th isotope distribution in a tropical laterite derived from Granite (Pitinga river basin, Amazoitia, Brazil) application to assessment of weathering rate. Earth Planet Sci Lett 136 703-714... 

Toole J, Baxter M S and Thomson J (1987) The behavior of uranium isotopes with salinity change in three U.K. Estuaries. Estuarine Coastal Shelf Sci. 25 283-297 Torgersen T, Turekian KK, Turekian VC, Tanaka N, DeAngelo E, O Donnell JO (1996) " Ra distribution in surface and deep water of Long Island Sound Sources and horizontal transport rates. Cont Shelf Res 16 1545-1559... 

The three isotopes of uranium (238U, 235U, 234U) found in nature have longer half-lives (>103 years) than the oceanic mixing time (ca. 103 years). The distribution and concentration of U in rivers, estuaries, and coastal regions are extremely variable and not well understood. More work is clearly needed to understand further the complex interactions of active and carrier phases (Fe and Mn oxides), redox transformations, direct and indirect microbial transformations, and colloidal complexation that may be involved in the nonconservative behavior of U in estuaries. 

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... 

Sontag (1986) Pharmacokinetic Model. An extended multicompartmental model (see Figure 2-9) describing the kinetic behavior of uranium (absorption, distribution, and excretion as a function of time) in the organs of male and female rats was developed using data taken from experiments performed on 13-month-old male and female Sprague-Dawley rats intravenously injected with 1.54 mCi/kg (57 kBq/kg) U-uranyl citrate and sacrificed at 7, 28, 84, 168, or 336 days after injection. 

Jia G, Belli M, Sansone U, Rosamilia S, Gaudino S (2004) Concentration, distribution and characteristics of depleted uranium in the Kosovo ecosystem a comparison with some uranium behaviors in the normtil environment. J Radioanal Nucl Chem 260 481 94... 

Another relevant general review summarizes the knowledge on the behavior of series radionuclides in soils and plants and is intended to provide a comprehensive source of information for environmental impact studies (Mitchell et al. 2013). The summary of the data on plant to soil concentration ratios that depends on the specific soil and type of plant and the distribution of uranium within the parts of the plant is especially important. The dependence of the sorption of dissolved uranium compounds on the type of soil (like the clay content) and the parameters mentioned earlier (pH, complex forming agents, anions, presence of iron, organic matter, etc.), based mainly on studies of the (distribution factor) of spiked soil samples, is discussed. It is noted that in general the uranium concentration in plants is several orders of magnitude lower than in soil, but some plants may efficiently absorb uranium and translocation within the plant is quite common (Mitchell et al. 2013). These features, and especially the soil-to-plant transfer factors, will be discussed in Section 3.4 that deals with the uranium content in plants and soil and the relation between them. 

Last but not least, an excellent comprehensive document that covers practically all facets of environmental behavior of uranium was published by the Canadian Council of Ministers of the Environment (Environment 2007). The chemical and physical properties of uranium were reviewed and its distribution in the environment and bio-accumulation in various flora and biota were discussed. For example, guidelines for the permissible uranium concentration in soil were set according to the intended land use. Eor agricultural use and commercial land use, the maximum uranium concentration was 33 mg kg" for residential and parkland uses it was 23 mg kg , and a value of 300 mg kg" was set for industrial land use. This document also contains many tables that summarize the toxicological effects of uranium on humans and the uranium content in several food products, vegetation, soil, water, etc. In addition, a summary of the analytical methods that are used for the determination of uranium in a variety of environmental samples, very similar to Table 3.1, is given (Environment 2007). 

For finite reactor analysis, much of the contributors behaviors are lumped into few-group nuclear constants that are numerically fitted to values of various core parameters such as exposure, uranium and 11th1 urn concentrations, fuel temperature, coolant and moderator temperatures and densities and gadolinium concentrations in the moderator. The finite reactor analysis provides an examination of the reactivity effects of the power distributions since it models the radial and axial assembly distributions in the core. 

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