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Uranium Enrichment, Nuclear Fuels, and Fuel Cycles
Published in Robert E. Masterson, Nuclear Engineering Fundamentals, 2017
The simplest and most straightforward way to create uranium hexafluoride is to convert refined uranium yellowcake into uranium tetrafluoride, UF4(s), which is a stable green salt. Uranium tetrafluoride is then mixed with fluorine gas to create uranium hexafluoride gas. This process is sometimes called the dry hydrofluor process, and a simplified flowchart of how this process works is shown in Figure 10.7. In addition to the dry hydrofluor process, some uranium hexafluoride–processing plants use an alternative process called the wet solvent extraction process to convert uranium yellowcake (U3O8) into uranium tetrafluoride. Uranium hexafluoride can be produced from the UF4 by mixing it with fluorine gas (F2). This process is based on a slightly different set of extraction steps than the dry hydrofluor process uses, and the differences can be seen in Figure 10.8. In both cases, the uranium tetrafluoride is eventually converted into UF6. The chemical equation that governs this reaction is
Nuclear Fuel Materials
Published in C. K. Gupta, Materials in Nuclear Energy Applications, 1989
Figure 9 depicts a nuclear fuel cycle typical of that based on the currently adopted U-Pu fuel cycle. The nuclear energy program in the U.K. is an example of this cycle. Figure 10 shows the pathways/flow pattern of the fuel in distributed locations in the U.K. The cycle spreads over Springfields, near Preston; Capenhurst works, near Chester; Sellafield in Cumbria; and Dounreay in Caithness. At Springfields, uranium ore concentrates are processed to uranium metal, uranium tetrafluoride, and uranium hexafluoride. The uranium metal is used as in the Magnox power station. The uranium hexafluoride is sent to Capenhurst for enrichment and the enriched product is taken to Springfields for the manufacture of enriched oxide to fuel AGR and other reactor stations tht include SGHWR. After reactor irradiation, which takes on an average of 6 years in a Magnox reactor, or 5 years in an AGR, the fuel is discharged. The fuel from this stage enters the back-end of the cycle in which reprocessing becomes the central activity to obtain separation between useful and wasteful components of the fuel. These operations are carried out in Sellafield. Every tonne of natural uranium put into a Magnox reactor contains about 993 kg of 238U and 7 kg of 235U and after irradiation about 990 kg of 238U, 3 kg of 235U, 2.5 kg of plutonium in various isotopes, and about 4 kg of fission products are left. Nuclear fuel reprocessing currently in the U.K. is confined to Magnox fuel and is under the responsiblity of the British Nuclear Fuels Limited (BNFL).
Theoretical study of the mechanism of Te (g) + 3F2 (g)→TeF6 (g)
Published in Molecular Physics, 2022
Fatemeh Hosseini, Hassan Hadadzadeh, Hossein Farrokhpour, Hamidreza Jouypazadeh
The fluorination of metals is an effective method for preparing metal samples for the enrichment of isotopes by gas penetration and gas centrifugation [1–5]. For example, the fluorination of uranium tetrafluoride (UF4) produces uranium hexafluoride (UF6) which is a volatile compound at ordinary temperatures and an exceptionally useful form of uranium feed to the isotope separation. Also, the fluorination reaction has been used as a suitable tool for chemical separation, purification [6–8], and recently in nuclear medicine [9–11].