A review of the high temperature oxidation of uranium oxides in molten salts and in the solid state to form alkali metal uranates, and their composition and properties

Electrolytic reduction behavior of U3O8 in a molten LiCl–Li2O salt

“…It has been reported that lithium monouranate (Li 2 UO 4 ) is prepared by fusing LiCl with U 3 O 8 and various alkali metal uranates including lithium uranates have been thoroughly reviewed by Griffiths and Volkovich (1999). A phase diagram of a Li 2 O--UO 3 system (Griffiths and Volkovich, 1999) illustrates a number of stable lithium uranates such as Li 2 U 6 O 19 and Li 2 U 3 O 10 with respect to a Li 2 O concentration at 650 • C. However, it is proper to conclude that the lithium uranates found in this work are intermediates, since an electrolytic reduction under an electric current is not static and an exact form of the lithium uranates is difficult to characterize.…”

Uranium co-precipitation with iron oxide minerals

“…Examples of these are some forms of UO 3 solids and U(VI)-doped perovskites like La 2 MgTiO 6 (AZENHA et al, 1992;KHILLA et al, 1986;WEIGEL, 1986;TANNER et al, 1997). However, these forms have not been identified in the geologic environment (BURNS, 1999 and references therein) and they typically form at high temperature under aqueous and non-aqueous conditions (GRIFFITHS and VOLKOVICH, 1999, and references therein). Under chemically reducing conditions soluble U(VI) species can undergo biotic reduction to the sparingly soluble U(IV) species such as UO 2(s) as in FIG.…”

Characterization of Uranium in Archived 2H Evaporator Scale

“…Solid phase U(VI) can also exist as the less common uranate-type form, which has at least three single U-O bonds. 12,13,14 This form of U(VI) has not been documented to occur in the dissolved form. Uranate solids do not contain the short axial double U-O bonds (between ~1.75 to 1.85 Å), that are characteristic of uranyl forms of U(VI).…”