7783-81-5Relevant articles and documents
Iwasaki, M.
, p. 216 - 226 (1968)
Burns, R. C.,MacLeod, I. D.,O'Donnell, T. A.,Peel, T. E.,Philipp, K. A.,Waugh, A. B.
, p. 1737 - 1739 (1977)
Labaton, V. Y.,Johnson, K. D. B.
, p. 74 - 85 (1959)
Sakurai, T.
, p. 1140 - 1144 (1974)
Sakurai, T.,Iwasaki, M.
, p. 1491 - 1497 (1968)
Labaton, V. Y.
, p. 86 - 93 (1959)
Structural study and properties of the alkali metal, nitrosyl, and ammonium hepta- and octafluorouranates(VI)
Bougon,Charpin,Desmoulin,Malm
, p. 2532 - 2540 (1976)
The thermal decomposition of the heptafluorouranates(VI) of the alkali metals is shown to take place in two steps. The first step gives the octafluorouranates(VI) and UF6, and the decomposition rate is noticeable at temperatures above 100, 130, 150, and 210°C for the Na, K, Rb, and Cs salts, respectively. The second step for Na2UF8 yields pure NaF and UF6 above 300°C, whereas the decomposition temperatures for the K, Rb, and Cs salts are above 300, 350, and 400°C, respectively. Depending on the decomposition conditions, F2 and M2UF7 (M = K, Rb, Cs) or F2, UF6, and M3UF8 are formed. The heptafluorouranates(VI) of all the cations studied, except for ammonium, were shown to exhibit dimorphism. The parameters of their cubic form were obtained and are as follows: KUF7; a = 5.22 A?; RbUF7; a = 5.385 A?; CsUF7; a = 5.517 A?; NOUF7; a = 5.334 A?; NH4UF7; a = 5.393 A?; NaUF7(fccub), a = 8.511 A?, Z = 4. The x-ray pattern of the low-symmetry form of CsUF7 just below the solid transition temperature (15 ± 1°C) was indexed with a tetragonal cell where a = 5.50 A? and c = 5.37 A?. The x-ray diagrams of the low symmetry form of the other MUF7 salts were not indexed, whereas those of the octafluorouranates were indexed with orthorhombic cells. The vibrational spectra of the hepta- and octafluorouranates were found to be very dependent on the temperature, and for the same temperature on the cation size. In the solids at high temperature the disordered F positions are likely to be averaged to give pseudo-D5h and Oh symmetry structures for the UF7- and UF82- ions, respectively. At lower temperature, as the motions are frozen out, the observed spectra for the hepta- and octafluorouranates arise from structures of symmetry no higher than C2ν and D2d, respectively. The ions UF7- and UF82- were characterized in nitrosyl or cesium fluoride HF solutions, which were found to exchange F- ions with these anions. Based on observation of the chemical exchange between UF6 and UF7- and on a comparative study of the WF7- ion, a fluoride ion transfer mechanism is also found for UF7- dissolved in acetonitrile. Some trends observed in this study, like the thermal decomposition temperatures or the relative symmetries, are thought to arise from the differences in the cation-anion interaction. This interaction is stronger with smaller cations, which results in more distorted anions, less ionic U-F bonds, and paradoxically less stable complexes.
Jarry, R. L.,Steindler, M. J.
, p. 1847 - 1849 (1969)
Reaction of Fluorine Atoms with Monomeric and Polymeric Uranium Pentafluoride
Lyman, John L.,Holland, Redus
, p. 4821 - 4826 (1987)
We have measured the room-temperature rate constants for formation of UF6 from the reaction of fluorine atoms with UF5.The rapid growth of UF5 clusters (polymers) from the nascent monomeric species complicates the rate measurements.The ratio of the rate of UF5-dimer formation to the rate of monomer-fluorine recombination is insensitive to the cluster formation.The ratio, kmm/krm = 5.0 +/- 1.0, is our most reliable experimental result.It, along with additional experimental data, gives krm = 8.0 x 1E-12 cm3 molecule-1 s-1 and kmm = 4.0 x 1E-11 cm3 molecule-1 s-1.To obtain the dependence of reaction rates on s, the average UF5 polymer size, we assumed that the rates were proportional to the collision rate.The derived rate constants were kpp = kmms1/6 cm3 molecule-1 s-1 for cluster growth and krp = 4.1 x 1E-14(1 + 2s1/3)2 cm3 molecule-1 s-1 for reaction of fluorine atoms with polymeric UF5.The experimental procedure was to photolyze both F2 and UF6 in helium diluent with a KrF excimer laser to produce UF5 and an excess of fluorine atoms.This allowed the slower recombination reactions to compete with polymerization.We monitored the transient concentration of UF6 with an ultraviolet probe beam at 215 nm.The recombination of fluorine atoms with UF5 monomer is substantially faster than recombination with the polymer.
Preparation of MF6·NaF complexes with uranium, tungsten, and molybdenum hexafluorides
Katz, Sidney
, p. 666 - 668 (1966)
The hexafluorides of uranium, tungsten, and molybdenum react with sodium fluoride to reach 1:2 and 1:1 stoichiometric ratios with unexpected speed when the sodium fluoride has been formed by decomposition of UF6·2NaF. The equilibrium pressures
Use of high-surface-area sodium fluoride to prepare MF6·2NaF complexes with uranium, tungsten, and molybdenum hexafluorides
Katz, Sidney
, p. 1598 - 1600 (1964)
Successful preparation of MF6·2NaF compounds by gas-solid reactions is shown to be dependent on the use of high-surface-area sodium fluoride and proper reaction temperatures. The reaction was fastest with UF6 and proceeded most close
Darstellung and Characterisierung der kationischen Metallocen-Komplexe 2 und : Laborsynthese von UF6
Schulz, Axel,Klapoetke, Thomas M.
, p. 91 - 94 (1993)
The five-coordinate, dicationic complex 2 (1) was formed by reaction of Cp2ZrCl2 and 2 equiv. of AgAsF6 in acetonitrile.A stable, polymeric niobocenium UF6 complex, (2), was synthesized from Cp2NbCl2 and UF6.A convenient laboraotry-scale synthesis of pure UF6 is reported.
Separation of metallic residues from the dissolution of a high-burnup BWR fuel using nitrogen trifluoride
McNamara, Bruce K.,Buck, Edgar C.,Soderquist, Chuck Z.,Smith, Frances N.,Mausolf, Edward J.,Scheele, Randall D.
supporting information, p. 1 - 8 (2014/05/06)
Nitrogen trifluoride (NF3) was used to fluorinate the metallic residue from the dissolution of a high burnup, boiling water reactor fuel (～70 MWd/kgU). The washed residue included the noble-metal phase (containing ruthenium, rhodium, palladium, technetium, and molybdenum), smaller amounts of zirconium, selenium, tellurium, and silver, along with trace quantities of plutonium, uranium, cesium, cobalt, europium, and americium, likely as their oxides. Exposing the noble metal phase to 10% NF3 in argon, between 400 and 550 °C, removed molybdenum and technetium near 400 °C as their volatile fluorides, and ruthenium near 500 °C as its volatile fluoride. The events were thermally and temporally distinct and the conditions specified provide a recipe to separate these transition metals from each other and from the nonvolatile residue. Depletion of the volatile fluorides resulted in substantial exothermicity. Thermal excursion behavior was recorded with the thermal gravimetric instrument operated in a non-adiabatic, isothermal mode; conditions that typically minimize heat release. Physical characterization of the noble-metal phase and its thermal behavior are consistent with high kinetic velocity reactions encouraged by the nanoparticulate phase or perhaps catalytic influences of the mixed platinum metals with nearly pure phase structure. Post-fluorination, only two products were present in the residual nonvolatile fraction. These were identified as a nano-crystalline, metallic palladium cubic phase and a hexagonal rhodium trifluoride (RhF3) phase. The two phases were distinct as the sub-μm crystallites of metallic palladium were in contrast to the RhF3 phase, which grew from the parent, nano-crystalline noble-metal phase during fluorination, to acicular crystals exceeding 20-μm in length.
