Solid solution limits in SYNROC zirconolite
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), Vol. 4:3
- Country of Publication:
- United States
- Language:
- English
Similar Records
The incorporation of cerium in zirconolite
Preparation and characterization of inductively-melted synroc
Related Subjects
36 MATERIALS SCIENCE
HIGH-LEVEL RADIOACTIVE WASTES
SYNROC PROCESS
ZIRCONOLITE
CHEMICAL PREPARATION
FISSION PRODUCTS
QUANTITY RATIO
RADIOACTIVE WASTE PROCESSING
RARE EARTH COMPOUNDS
SOLIDIFICATION
SYNTHETIC ROCKS
THORIUM OXIDES
URANIUM
URANIUM DIOXIDE
ACTINIDE COMPOUNDS
ACTINIDES
ALKALINE EARTH METAL COMPOUNDS
CALCIUM COMPOUNDS
CALCIUM OXIDES
CHALCOGENIDES
ELEMENTS
IRON COMPOUNDS
IRON OXIDES
ISOTOPES
MANAGEMENT
MATERIALS
METALS
MINERALS
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PHASE TRANSFORMATIONS
PROCESSING
RADIOACTIVE MATERIALS
RADIOACTIVE WASTES
ROCKS
SYNTHESIS
SYNTHETIC MATERIALS
THORIUM COMPOUNDS
TITANIUM COMPOUNDS
TITANIUM OXIDES
TRANSITION ELEMENT COMPOUNDS
URANIUM COMPOUNDS
URANIUM OXIDES
WASTE MANAGEMENT
WASTE PROCESSING
WASTES
ZIRCONIUM COMPOUNDS
ZIRCONIUM OXIDES
052001* - Nuclear Fuels- Waste Processing
360202 - Ceramics
Cermets
& Refractories- Structure & Phase Studies