Open AccessWaste forms based on Cs-loaded silicotitanates
Author(s) -
M. Lou Balmer,
Bruce C. Bunker
Publication year - 1995
Language(s) - English
Resource type - Reports
DOI - 10.2172/86952
Subject(s) - radioactive waste , ion exchange , aqueous solution , materials science , thermal treatment , mineralogy , phase (matter) , ion , nuclear chemistry , chemistry , composite material , organic chemistry
Silicotitanate ion exchange materials are being considered for removal of radioactive Cs and Sr from tank wastes at the Hanford site. The phase evolution as a function of heat treatment temperature for several sol gel derived compositions within the Cs{sub 2}O-SiO{sub 2}-TiO{sub 2} system was investigated, in order to determine if an adequate waste form can be achieved by direct thermal conversion. The Cs leach rates and Cs loss during heat treatment of select materials were measured. Some compositions which contain large amounts of Ti melt to form a glass with reasonably low aqueous leach rates. A new Cs-silicotitanate material with a structure isomorphous to pollucite was discovered. This material forms at low temperatures (700--800 C) where Cs volatility is negligible. The silicotitanate-pollucite exhibits extremely low leach rates (1.42 g/m{sup 2}day ) at 90 C, and has been identified as a promising waste form for Cs containment