Study of natural zircon-xenotime assemblages for estimation of the actinide waste forms stability
In order to estimate compositions and structural stability of YPO{sub 4}-ZrSiO{sub 4}-USiO{sub 4}-ThSiO{sub 4} solid solution, natural specimens of (U, Th)-enriched zircon-xenotime assemblages were studied. The samples were picked from granitic pegmatites of North Karelia of about 1,850 Ma age. TEM data show that amorphization of the zircon structure is not complete. Xenotime has typical crystal structure. ASEM and EPMA results indicate that zircon and xenotime are micro-heterogeneous in there compositions. Numerous micro-inclusions (<5 {micro}m in diameter) of xenotime and uranium oxide were found within the zircon grains. Xenotime is free from inclusions. The results give rise to the conclusions that xenotime-zircon solid solution is restricted due to high difference in ionic radii (Y{sup 3+} vs. Zr{sup 4+} and P{sup 5+} vs. Si{sup 4+}). Data on high amounts of rare earth elements and phosphorus in natural zircons are result from REE-phosphate inclusions in analyzed zircons. Content of U in the zircon allowed the estimation of the solubility of coffinite end member to be no less than 5 mol.% USiO{sub 4}.
- Research Organization:
- IGEM RAS, Moscow (RU)
- OSTI ID:
- 20015831
- Resource Relation:
- Conference: 1998 Materials Research Society Fall Meeting, Boston, MA (US), 11/30/1998--12/04/1998; Other Information: Single article reprints are available from University Microfilms Inc., 300 North Zeeb Road, Ann Arbor, Michigan 48106; PBD: 1999; Related Information: In: Scientific basis for nuclear waste management XXII. Materials Research Society symposium proceedings: Volume 556, by Wronkiewicz, D.J.; Lee, J.H. [eds.], 1355 pages.
- Country of Publication:
- United States
- Language:
- English
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