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From uranium ore to fuel element: the front-end of the nuclear fuel cycle
Published in Peter R. Mounfield, World Nuclear Power, 2017
After being refined near the mines and mills the product is shipped to a conversion plant. Here, to reach the high level of purity required for nuclear fuel, the ore concentrate is dissolved in 99.95 per cent pure nitric acid. The uranyl nitrate in turn is converted to volatile uranium hexafluoride or ‘hex’ which is used in the enrichment process.
Nuclear Fuel Materials
Published in C. K. Gupta, Materials in Nuclear Energy Applications, 1989
Among the reprocessing methods, the Purex process is the only one that has gained wide acceptance. This is basically a solvent extraction process with TBP as an extractant for the treatment of spent fuel dissolved in nitric acid. The principle of extraction can be enumerated by reference to uranium. Uranyl nitrate behaves as a strong electrolyte, being completely dissociated into uranyl (UO2++) and nitrate (NO3−) ions. Introduction of a common ion, in this case NO3−, into the aqueous solution shifts the equilibrium towards formation of anionic complexes. Undissociated nitrate complex forms a complex with the organic solvent. The following equilibria are established:
A new perspective on the inhibition of plant photosynthesis by uranium: decrease of root activity and stomatal closure
Published in International Journal of Phytoremediation, 2022
Xi Chen, Guo Wu, Pixian Xiao, Qiong Ma, Yi Li, Jinlong Lai, Xuegang Luo, Xiaohui Ji, Jianhua Xia, Xiulin Yang
The U concentration in the soil around the U tailings is about 5.2–48.1 mg·kg−1, of which could absorbed by the plant roots was about 10–100 μM (2.38–23.8 mg·kg−1) (Yan and Luo 2015). Meanwhile, 25 μM of U has been reported to inhibit plant growth but not cause death (Tewari et al.2015; Lai et al.2020). Thus the U concentrations in the present study were chosen: 0 μM (control), 10 μM, and 25 μM. Uranyl nitrate [238U, UO2(NO3)2·6H2O] was used as the U source. Phosphate-free modified Hoagland nutrient solution was used to prepare the different concentrations of U treatments as the phosphate in Hoagland nutrient solution may formed an insoluble precipitate with uranyl ions. The leaves were sprayed with 0.1 mM KH2PO4 once a day to prevent phosphorus deficiency in the seedlings (Lai et al.2020). Similar sized two-leaf seedlings were randomly selected and whose nutrient solution was replaced with the treatment solution containing different U concentrations. After 2 weeks of treatment (the stem length and leaf area in the treatment group were obviously smaller than those in the control), samples were taken to measure all indicators.
Scoping Studies of Dopants for Stabilization of Uranium Nitride Fuel
Published in Nuclear Science and Engineering, 2019
Klara Insulander Björk, Aneta Herman, Marcus Hedberg, Christian Ekberg
Fabrication was performed using a modified internal gelation process.28 A starting material—uranyl nitrate hexahydrate (UNH) [UO2(NO3)2·6H2O]—was produced from metallic uranium (a uranium metal rod) by dissolving it in concentrated nitric acid. The most common procedure, using acid-deficient uranyl nitrate (ADUN) (NO/UO2) solution,29 was not followed. Instead, crystals of UNH were collected from a mother liquor, washed, and air dried, making it possible to produce a solution with NO/UO = 2. The effect of using this method instead of the traditional ADUN technique is that the maximum U concentration is now limited to the solubility of UNH.
Optical Spectroscopic Investigation of Hexavalent Actinide Ions in n-Dodecane Solutions of Tri-butyl Phosphate
Published in Solvent Extraction and Ion Exchange, 2021
Gregg J. Lumetta, Forrest D. Heller, Gabriel B. Hall, Susan E. Asmussen, Sergey I. Sinkov
Uranium(VI) solutions were prepared from a stock of uranyl nitrate of known concentration. The uranyl nitrate stock was available as a legacy source of depleted uranium in our laboratory. Nitric acid was purchased from Sigma Aldrich. The concentration of the HNO3 stock was determined through measurement of solution density prior to making uranyl nitrate solutions.[13]