Glass - Back to the Future!



Presenting Author:
Colleen Mann
<cmann1@sheffield.ac.uk>

article posted 2 Apr 2016


Colleen Mann currently works within the immobilisation science laboratory at the University of Sheffield. She hase been conducting PhD research under the supervision of Dr Claire Corkhill, Prof Neil Hyatt and Prof John Provis. The aim of this research is to understand how the evolving geochemical conditions of an engineered barrier affect the dissolution kinetics of intermediate level waste glass.






Interactions between simulant vitrified nuclear wastes and idealised cement leachates

Colleen Mann1*, John L. Provis1, Neil C. Hyatt1, Antoni E. Milodowski2, Lorraine Field2, Richard Shaw2 and Claire L. Corkhill1


The UK Government have stated their preference for the final disposal of radioactive waste within a Geological Disposal Facility (GDF), at a depth of between 200 m and 1 km1. The GDF will incorporate Engineered Barrier Systems (EBS) that will be optimised to physically and chemically retard the transport of radionuclides to the biosphere. In the case of the proposed GDF for UK Intermediate Level Waste (ILW), groundwater will interact with the cementitious components of the EBS, resulting in a highly alkaline and calcium-rich groundwater composition that will evolve as a function of time. In order to evaluate the merit of such an EBS system for vitrified ILW materials, an assessment of glass durability in cementitious leachate solutions is required.

We present results from an investigation of the interaction of simulated ILW glasses and the International simple glass2 with cement leachate solutions. Glass powders were exposed to idealised cement leachates, of "intermediate" and "old" ages, approximately representative of GDF conditions at ~1000 and ~10,000 years of operation, according to the ASTM standard C1285-14 product consistency test B3. Analysis of the normalised mass loss and normalised leaching rate of these glasses as a function of cement leachate composition was achieved through analysis of solution concentrations.

We present concurrent analysis of monolith sample alteration layers by SEM / EDX and vertical scanning interferometry. Combined, these data support a mechanistic understanding of glass dissolution in the context of a complex geological disposal environment for vitrified UK ILW. These experiments are complimented by a high pH natural analogue study at a historic lime kiln site in the UK, where a range of glass compositions will be exposed to relevant conditions for 1, 2, 5 and 10 years.

References:

1 Department of Energy & Climate Change, Implementing Geological Disposal, 2014.

2 S. Gin, A. Abdelouas, L. J. Criscenti, W. L. Ebert, K. Ferrand, T. Geisler, M. T. Harrison, Y. Inagaki, S. Mitsui, K. T. Mueller, J. C. Marra, C. G. Pantano, E. M. Pierce, J. V. Ryan, J. M. Schofield, C. I. Steefel and J. D. Vienna, An international initiative on long-term behavior of high-level nuclear waste glass, Materials Today, 2013, vol. 16.

3 Standard Test Methods for Determining Chemical Durability of Nuclear, Hazardous, and Mixed Waste Glasses and Multiphase Glass Ceramics : The Product Consistency Test (PCT) ASTM C1285-14, 2002, vol. 15.

Institutions:

1 Immobilisation Science Laboratory, Department of Materials Science and Engineering, The University of Sheffield, Mappin Street, Sheffield S1 3JD, UK

2 British Geological Survey, Environmental Science Centre, Nicker Hill, Keyworth, Nottingham, NG12 5GG, UK