Ion-exchange processes and mechanisms in glasses

Abstract

'Recent performance assessment calculations of a disposal system at the Hanford Site in Washington State for low-activity waste glass show that a sodium ion exchange reaction can effectively increase the radionuclide release rate by over a factor of 1,000. The susceptibility of the glass to alkali ion exchange is thus a major factor limiting waste loading. However, low temperature ion exchange has not been thought to be important in recent analyses of waste glass durability. The objective of this work is to develop an understanding of the processes and mechanisms controlling alkali ion exchange and to correlate the kinetics of the ion exchange reaction with glass structural properties. The fundamental understanding of the ion exchange process developed under this study is targeted at developing lower ion-exchange rate glasses that would remain durable at higher alkali waste loading. This report summarizes eight months of work on this three-year project that is being performed cooperatively between Pacific Northwest National Laboratory and Lawrence Berkeley National Laboratory.'