Formation, oxidation and alteration of ianthinite
- Univ. of New Mexico, Albuquerque, NM (United States)
Ianthinite, UO{sub 2.86}{center_dot}1.5H{sub 2}O, is a weathering product of uraninite, UO{sub 2+x}, and has been reported as a corrosion product of UO{sub 2}. Ianthinite alters to schoepite, UO{sub 3}{center_dot}2H{sub 2}O, or studtite, UO{sub 4}{center_dot}2-4H{sub 2}O, in water. The structures of ianthinite, shoepite and studtite are unknown, but their unit cell parameters differ significantly, and transformations are likely reconstructive. XRD powder data for ianthinite and becquerelite are similar, and they are probably isostructural; U{sup 4+}, as U(OH){sub 2}{sup 2+}, replaces Ca{sup 2+} in the interlayer. The proposed formula is U(OH){sub 2}{sup 2+}[(UO{sub 2}){sub 6}O{sub 4}(OH){sub 6}]{center_dot}6H{sub 2}O. Oxidation in air, has been reported to form shoepite; however, in the absence of water, the oxidation of ianthinite, U(OH){sub 2}{sup 2+}[(UO{sub 2}){sub 6}O{sub 4}(OH){sub 6}]{center_dot}6H{sub 2}O + 1/2 O{sub 2} {yields} (UO{sub 2}){sup 2+}[(UO{sub 2}){sub 6}O{sub 4}(OH){sub 6}]{center_dot}7H{sub 2}O, shows that epi-ianthinite is structurally distinct from shoepite. The oxidation of fine-grained material is rapid, and the color change -- from dark purple to yellow -- is dramatic. The acicular habit of ianthinite is preserved during oxidation, and acicular {open_quotes}shoepite{close_quotes} is observed in nature, as well as in leaching experiments on spent fuel. Possible substitution of Pu{sup 4+} for U{sup 4+} suggests that Pu-ianthinite may control Pu solubility in oxidizing, U-saturated solutions.
- OSTI ID:
- 47905
- Report Number(s):
- CONF-931108-Vol.333; TRN: 95:011413
- Resource Relation:
- Conference: Fall meeting of the Materials Research Society (MRS), Boston, MA (United States), 29 Nov - 3 Dec 1993; Other Information: PBD: 1994; Related Information: Is Part Of Scientific basis for nuclear waste management XVII; Barkatt, A. [ed.] [Catholic Univ. of America, Washington, DC (United States)]; Van Konynenburg, R.A. [ed.] [Lawrence Livermore National Lab., CA (United States)]; PB: 964 p.
- Country of Publication:
- United States
- Language:
- English
Similar Records
Potential incorporation of transuranics into uranium phases
Neptunium(V) Partitioning to Uranium(VI) Oxide and Peroxide Solids