Transuranium element incorporation into the {beta}-U{sub 3}O{sub 8} uranyl sheet

Conference · Wed Dec 31 04:00:00 EST 1997

OSTI ID:572128

Miller, M L; Burns, P C; Ewing, R C ^[1]; Finch, R J ^[2]

---

1. Univ. of New Mexico, Albuquerque, NM (United States). Dept. of Earth and Planetary Sciences
2. Univ. of Manitoba, Winnipeg (Canada). Dept. of Geology

Spent nuclear fuel (SNF) is unstable under oxidizing conditions. Although recent studies have determined the paragenetic sequence for uranium phases that result from the corrosion of SNF, there are only limited data on the potential of alteration phases for the incorporation of transuranium elements. The crystal chemical characteristics of transuranic elements (TUE) are to a certain extent similar to uranium; thus TUE incorporation into the sheets of uranyl oxide hydrate structures can be assessed by examination of the structural details of the {beta}-U{sub 3}O{sub 8} sheet type. The sheets of uranyl polyhedra observed in the crystal structure of {beta}-U{sub 3}O{sub 8} also occur in the mineral billietite, where they alternate with {alpha}-U{sub 3}O{sub 8} type sheets. Preliminary crystal structure determinations for the minerals ianthinite, and wyartite, indicate that these phases also contain {beta}-U{sub 3}O{sub 8} type sheets. The {beta}-U{sub 3}O{sub 8} sheet anion topology contains triangular, rhombic, and pentagonal sites in the proportions 2:1:2. In all structures containing {beta}-U{sub 3}O{sub 8} type sheets, the triangular sites are vacant. The pentagonal sites are filled with U{sup 6+}O{sub 2} forming pentagonal bipyramids. The rhombic dipyramids filling the rhombic sites contain U{sup 6+}O{sub 2} in billietite, U{sup 4+}O{sub 2} in {beta}-U{sub 3}O{sub 8}, U{sup 4+} (H{sub 2}O){sub 2} in ianthinite, and U{sup 4+}O{sub 3} in wyartite-II. Interlayer species include: H{sub 2}O (billietite, wyartite II, and ianthinite), Ba{sup 2+} (billietite) Ca{sup 2+} wyartite II, and Co{sub 3}{sup 2{minus}} wyartite II; there is no interlayer in {beta}-U{sub 3}O{sub 8}. The similarity of known TUE coordination polyhedra with those of U suggests that the {beta}-U{sub 3}O{sub 8} sheet will accommodate TUE substitution coupled with variations in apical anion configuration and interlayer population providing the required charge balance.

• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: FG03-95ER14540
• OSTI ID: 572128
• Report Number(s): CONF-961202--
• Country of Publication: United States
• Language: English

Related Subjects

05 NUCLEAR FUELS
36 MATERIALS SCIENCE
BILLIETITE
CRYSTAL STRUCTURE
IANTHINITE
PHASE STUDIES
RADIOACTIVE WASTE DISPOSAL
SPENT FUELS
TRANSURANIUM ELEMENTS
URANIUM MINERALS
URANIUM OXIDES U3O8
YUCCA MOUNTAIN