Solid solution limits in SYNROC zirconolite

Journal Article · Sat Jan 01 04:00:00 EST 1983 · Nucl. Chem. Waste Manage.; (United States)

OSTI ID:6386797

Kesson, S E; Ringwood, A E; Sinclair, W J

In the titanate ceramic high-level wasteform SYNROC, zirconolite (CaZrTi/sub 2/O/sub 7/) is the primary host for uranium and tetravalent actinides, and the secondary host for rare earths and trivalent actinides. Significant amounts of other fission products and processing contaminants also enter into solid solution in its lattice. Experiments investigating the binary joins between CaZrTi/sub 2/O/sub 7/ and various real or hypothetical end-members show that zirconolite solid solutions can accept 27 wt% UO/sub 2/, 20% ThO/sub 2/, at least 29% rare earth oxides, 14% Nb/sub 2/O/sub 3/, 7% Al/sub 2/O/sub 3/, 4% MgO, 4% FeO or 5% MnO, but only limited amounts of Na/sub 2/O, SrO and NiO. The smaller cations Nb/sup 5 +/, Al/sup 3 +/, Mg/sup 2 +/ and Fe/sup 2 +/ are partitioned into the Ti-sites. Rare earths are preferentially accommodated in the Ca-site but also occupy the Zr-site. Th/sup 4 +/ and Mn/sup 2 +/ are strongly partitioned into the Ca-site. In contrast with natural zirconolites, U/sup 4 +/ enters the Zr-site, but can be accommodated in both Ca- and Zrsites via coupled substitution of a small lower valence cation e.g., Mg/sup 2 +/, Fe/sup 2 +/, Fe/sup 3 +/, or Al/sup 3 +/ for Ti/sup 4 +/. A comparison of natural and synthetic zirconolites indicates that the structure requires at least 50 mole % occupancy of the Ti-sites by Ti/sup 4 +/ and 70 mole % occupancy of the Zr-site by Zr/sup 4 +/.

• Research Organization: Research School of Earth Sciences, Australian National University, Canberra, ACT
• OSTI ID: 6386797
• Journal Information: Nucl. Chem. Waste Manage.; (United States), Journal Name: Nucl. Chem. Waste Manage.; (United States) Vol. 4:3; ISSN NCWMD
• Country of Publication: United States
• Language: English

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Cermets
& Refractories-- Structure & Phase Studies
ACTINIDE COMPOUNDS
ACTINIDES
ALKALINE EARTH METAL COMPOUNDS
CALCIUM COMPOUNDS
CALCIUM OXIDES
CHALCOGENIDES
CHEMICAL PREPARATION
ELEMENTS
FISSION PRODUCTS
HIGH-LEVEL RADIOACTIVE WASTES
IRON COMPOUNDS
IRON OXIDES
ISOTOPES
MANAGEMENT
MATERIALS
METALS
MINERALS
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PHASE TRANSFORMATIONS
PROCESSING
QUANTITY RATIO
RADIOACTIVE MATERIALS
RADIOACTIVE WASTE PROCESSING
RADIOACTIVE WASTES
RARE EARTH COMPOUNDS
ROCKS
SOLIDIFICATION
SYNROC PROCESS
SYNTHESIS
SYNTHETIC MATERIALS
SYNTHETIC ROCKS
THORIUM COMPOUNDS
THORIUM OXIDES
TITANIUM COMPOUNDS
TITANIUM OXIDES
TRANSITION ELEMENT COMPOUNDS
URANIUM
URANIUM COMPOUNDS
URANIUM DIOXIDE
URANIUM OXIDES
WASTE MANAGEMENT
WASTE PROCESSING
WASTES
ZIRCONIUM COMPOUNDS
ZIRCONIUM OXIDES
ZIRCONOLITE