Chemistry of Rare Earth Oxalate Vitrification

Abstract

AbstractMixtures 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.