The Impact of Na—H+ Exchange on Long-Term Borosilicate Glass Corrosion: Experiments and Field Observations
New insights from laboratory experiments coupled with field observations indicate that pore water solutions that eventually breach containment materials in disposal systems will interact with sodium-excess borosilicate waste glass in an unexpected way. Because many glass waste forms are relatively sodium-rich, they are especially vulnerable to Na+—H+ exchange (ion exchange or simply, IEX). Although the kinetics of this process has been previously investigated for early-stage glass reactions, the implications of IEX for long-term dissolution resistance have not yet been realized. Non-radioactive glass with major- and minor-element chemical compositions similar to Hanford high-Na waste glass were subjected to dissolution experiments to quantify the rates of matrix dissolution and IEX rates. Single-Pass Flow-Through (SPFT) tests quantified the IEX rate at 40°C pH = 8 and silica saturation and showed a dependence upon the fraction of excess sodium in the glass. The equation for the rate (in moles of sodium released per meter squared per second) dependence on excess sodium is: log10rate[mol/(m2∙s)] = 0.63R + (-11.0); r2 = 0.86 where R = molar Na+/(M3+). Further, rates of Na release are slower by ≥30% in D2O-based solutions compared to those in H2O. These results are the hallmark of IEX reactions. Our results are compared against those from a lysimeter field experiment consisting of glasses buried in Hanford sand and to dissolution experiments conducted with a Pressurized Unsaturated Flow (PUF) apparatus. These longer-term tests indicate an initial decrease in dissolution rate by a factor of 10×, and then a constant steady-state rate thereafter. Thus, these data show that IEX reactions are important at near-saturation conditions and effectively prevent dissolution rates from falling below a minimum value. In sum, IEX modifies the long-term behavior of glass dissolution and models cannot assume that dissolution of Na-rich borosilicate glass will decrease by a factor of 100× to 1000×, as argued for minerals and less sodic glasses.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 1024553
- Report Number(s):
- PNNL-SA-64130; DF0961000; TRN: US1104758
- Resource Relation:
- Conference: Waste Management 2009: Waste Management for the Nuclear Renaissance, March 1-5, 2009 (WM2009), Phoenix, Arizona, Paper No. 9404
- Country of Publication:
- United States
- Language:
- English
Similar Records
Current Efforts in Immobilized Low-Activity Waste Glass Testing to Support the Hanford Site Integrated Disposal Facility - 17119
Experimentally determined dissolution kinetics of Na-rich borosilicate glass at far from equilibrium conditions: Implications for Transition State Theory
Related Subjects
AQUEOUS SOLUTIONS
BOROSILICATE GLASS
CHEMICAL COMPOSITION
CONTAINMENT
CORROSION
DISSOLUTION
GLASS
KINETICS
LYSIMETERS
METERS
SAND
SATURATION
SILICA
SODIUM
WASTE FORMS
WASTE MANAGEMENT
WASTES
borosilicate glass
corrosion