Chemistry of Rare Earth Oxalate Vitrification
- PDF / 1,063,374 Bytes
- 9 Pages / 386 x 620 pts Page_size
- 64 Downloads / 208 Views
ceedings: Email alerts: Click here Subscriptions: Click here Commercial reprints: Click here Terms of use : Click here
Chemistry of Rare Earth Oxalate Vitrification J. D. Vienna, D. K. Peeler, J. G. Darab, J. R. Zamecnik, H. LI and J. E. Marra MRS Proceedings / Volume 556 / 1999 DOI: 10.1557/PROC556321
Link to this article: http://journals.cambridge.org/ abstract_S1946427400177796 How to cite this article: J. D. Vienna, D. K. Peeler, J. G. Darab, J. R. Zamecnik, H. LI and J. E. Marra (1999). Chemistry of Rare Earth Oxalate Vitrification. MRS Proceedings,556, 321 doi:10.1557/PROC556321 Request Permissions : Click here
Downloaded from http://journals.cambridge.org/OPL, IP address: 128.118.88.243 on 01 Sep 2012
CHEMISTRY OF RARE EARTH OXALATE VITRIFICATION J. D. VIENNA, D. K. PEELER t , J. G. DARAB, J. R. ZAMECNIK t , H. LI, and J. E. MARRA t Pacific Northwest National Laboratory, Richland, Washington 99352 Westinghouse Savannah River Company, Aiken, South Carolina 29808 ABSTRACT Mixtures of rare earth and actinide oxalates will be vitrified into boro-aluminosilicate-based glasses for intermediate term stabilization according to current plans. The reaction chemistry involved with converting these oxalate feed stocks into glass products determines the potential for foaming, redox, and other melt and off gas related phenomena associated with this process. We've undertaken a detailed study of this conversion process using a variety of complementary techniques. A closed quartz crucible contained in a vertical furnace equipped with a quartz window and video camera was used to study volume expansion of the feed/melt during heating while monitoring the off-gas using a gas chromatograph-mass spectrometer. Simultaneous thermogravimetric and differential thermal analyses were conducted on small samples of feed and frit mixtures. Samples containing Ce were analyzed using established wet chemical techniques to determine Ce3+:Ce4+ ratio (redox) as a function of temperature. We evaluate the results and provide a description of the reaction chemistry of these oxalate feeds during vitrification. INTRODUCTION Approximately 15,000 L of solution containing isotopes of Am and Cm, currently stored at the Savannah River Site (SRS), will be converted into a high-lanthanide glass for stabilization [1]. Pretreatment operations will be performed to separate actinides and lanthanides from impurities (primarily iron, aluminum, and sodium) and to concentrate the solution to approximately 100 grams per liter (g/L) dissolved solids (as equivalent metal oxide) in a nitric acid solution. Approximately 10% of the total dissolved solids are Am and Cm. The nitric acidbased Am-Cm solution (or in the case of this study the non-radioactive surrogate) is transferred
into a reaction vessel. Oxalic acid (8 wt.%) is added to the solution to precipitate the rare-earth elements as oxalates [2]. The precipitate is allowed to settle and the excess liquid is decanted. A dilute oxalic acid wash solution (0. 1 OM) is added to remove excess contaminants (e.g
Data Loading...
