Glass Composition Effects on Stage-III Corrosion of Nuclear Waste Glass

Open Access
Author:
Rice, Jarrett Andrew
Graduate Program:
Materials Science and Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
November 14, 2016
Committee Members:
  • Carlo G Pantano, Thesis Advisor
  • Seong Han Kim, Committee Member
  • William B. White, Committee Member
Keywords:
  • Vitrification
  • Stage-III Corrosion
  • Glass
  • SON68
  • AFCI
  • Nuclear Waste
  • Composition Effects
Abstract:
The corrosion process of glass in solution can be represented and understood by several stages. This study focuses on the recently hypothesized and not well understood Stage-III corrosion. Stage-III corrosion, the unexpected resumption of high-rate glass dissolution, has been observed to occur for some glass waste forms and not for others. The onset is unpredictable, but is likely related to the composition of the waste glass and the state of the contacting solution or environment. The two reference waste glasses studied are comprised of 26 oxides with 20 common components between them. The first glass is a French waste form, referred to as SON68. The other is a waste glass developed by the United States Department of Energy for the Advanced Fuel Cycle Initiative, and is referred to as AFCI. The glass SON68 has been shown to release markedly larger quantities of glass species into the contacting solution, but in the long term, is consistently the more durable of the two glasses, while AFCI is more susceptible to this Stage-III transition. For this reason, these two reference (simulated) waste glasses were studied to determine how the differences and similarities in composition may affect the transition to Stage-III corrosion. Ideally, this might provide clues to the critical species or concentrations triggering the transition. To do this, combinations of the two glasses were melted together in ratios by weight of 75% SON68 to 25% AFCI, 50% SON68 to 50% AFCI, and 25% SON68 to 75% AFCI. These blends, along with pure SON68 and pure AFCI, were reacted according to standard glass durability test methods. Crushed glass powder from each composition was reacted in separate vessels of ASTM Type 1 water at 90°C. Along with powder, bulk glass monoliths were added to some containers as reference samples for characterization. Although only one of the blends transitioned into Stage-III corrosion, pertinent information could be drawn based on composition and precipitated mineral formations for this glass. For all the glass compositions, the likelihood of a Stage-III transition could be rationalized based on a strong base/weak acid model using solution analysis data. Irrespective of a Stage-III transition, clear trends through the range of glass compositions were also identified for the formation of a phyllosilicate mineral, and as a result, its impact on the glass durability was hypothesized.