The hydrated tetrafluorides of uranium and plutonium

Abstract

The tetrafluorides of uranium and plutonium form two hydrates, the higher one having 2-5 molecules of water per metal atom and the lower one 2.0 molecules of water or less. Methods for their formation have been investigated.The lower hydrate is pseudo-cubic, a = 5.69 kX for the uranium and 5.63 kX for the plutonium compound, and the proposed structure is similar to that of uranium dioxide, the water molecules occupying vacant uranium sites and being hydrogen-bonded to the fluorine. Very little change of cell dimension was observed over the range UF4,2H,0 to UF4,0.75H,0.The fluorination, at temperatures below loo", of the dioxides with gaseous hydrogen fluoride gives the lower fluoride hydrate and a second product which may be M(OH)F,,HF.

Characterizing the solid hydrolysis product, UF4(H2O)2.5, generated from neat water reactions with UF4 at room temperature

“…Water can also occupy vacancy sites of the U 4+ ion to form two hydrate phases: the pseudo-cubic UF4(H2O)n where 0.5 ≤ n ≤ 2 and UF4(H2O)2.5. 13,14 The 2.5 hydrate, which has been minimally characterized to-date, has been shown to form when anhydrous UF4 is placed in dilute aqueous HF solutions. 15,16 The pseudo-cubic phase, which is a derivative of the CaF2-type phase, can form from a number of reactions, including electrolytic reduction of uranyl fluoride (UO2F2) in aqueous hydrofluoric acid, 17,18 addition of aqueous hydrofluoric acid to aqueous uranium tetrachloride (UCl4), 19 and hydration of UF4 formed from various dehydration reactions.…”

“…15,16 The pseudo-cubic phase, which is a derivative of the CaF2-type phase, can form from a number of reactions, including electrolytic reduction of uranyl fluoride (UO2F2) in aqueous hydrofluoric acid, 17,18 addition of aqueous hydrofluoric acid to aqueous uranium tetrachloride (UCl4), 19 and hydration of UF4 formed from various dehydration reactions. 13,14 One report has even shown that UF4(H2O)n might hydrate as low as n = 0.4. 20 Elevated-temperature interactions of UF4 and water produce a variety of compounds.…”

Expansion of the Na3MIII(Ln/An)6F30 Series: Incorporation of Plutonium into a Highly Robust and Stable Framework

“…Less successful attempts to apply alternative methods for producing metallic plutonium did prove successful in preparing new plutonium phases in some cases; for example, the sodium vapor reduction of PuF 4 resulted in the novel phase (NaPuF 4 ) 1.5 . As part of an effort in the 1940s and 1950s to expand on and characterize the plutonium fluoride family, Zachariasen and Dawson et al . reported on the first crystal structures of several binary and ternary plutonium fluorides and oxyfluorides.…”

Characterization of the Environmentally Induced Chemical Transformations of Uranium Tetrafluoride

“…However characterization of actinide fluorides has typically favored the fully oxidized +6 complex (UF 6 ) due to the relevance as the uranium enrichment feedstock within various nuclear enterprises. [3][4][5] As such UF 6 has been extensively studied both within the context of chemistry and LDRD-2016-00031 LDRD Report chemical engineering; with recent focus on the hydrolysis product, uranyl fluoride, and the synthesis and characterization of various forms of uranyl fluoride hydrates. [6][7][8][9][10][11][12] The hydrolysis of the UF 6 is challenging physical chemistry problem and prior research has typically focused on the reaction products (e.g.…”

“…3 Many of the UF 4 hydrates were synthesized via the reduction of U +6 , or suspensions of UF 4 with aqueous hydrofluoric acid. 5,16 Other methods to produce UF 4 hydrates have involved application of thermal energy to liberate structurally bound water from the 2.5 hydrate; however these methods can be complicated by the unintended production of uranyl fluorides (UO 2 F 2 •xH 2 O) and/or uranium oxides (UO 2 ; U 3 O 8) . 5,17 The primary characterization method of prior work has been single crystal and powder X-ray diffraction, although other characterization methods have been utilized, including Infrared (IR) spectroscopy and NMR, those efforts had not unambiguously identified the material crystal structure.…”