Glass - Back to the Future!

Presenting Author:
Clare Thorpe

article posted 8 April 2016

Dr Clare L. Thorpe is Post Doctoral Research Associate at the University of Sheffield’s Immobilisation Science Laboratory. She graduated from the University of Manchester in 2008 with a MEarth Sci in Geochemistry and completed a PhD in Radionuclide Biogeochemistry in 2012. Prior to commencing her current PRDA position Clare worked for three years on a collaborative Knowledge Exchange project funded jointly by the University of Manchester and Sellafield Ltd studying radionuclide mobility in the Sellafield subsurface.

Leaching methodologies to evaluate the durability of Immobilized Low Activity Waste (ILAW) glasses

1Clare L. Thorpe*, 1Russell J. Hand, 1Neil C. Hyatt, 3Albert A. Kruger, 2David Kosson and 1Claire L. Corkhill
1Department of Materials Science & Engineering, The University of Sheffield, Mappin Street, Sheffield S1 3JD, United Kingdom.
2Vanderbilt School of Engineering, 2301 Vanderbilt Place, Nashville, TN.
3U.S. Department of Energy, Office of River Protection, Richland, WA 99352

At the Hanford site, USA, low activity tank wastes will be immobilised by vitrification to create 150-350,000m3 of Immobilised Low Activity Waste (ILAW) destined for disposal in a shallow subsurface Integrated Disposal Facility (IDF). During reprocessing, tank wastes have a separable low activity waste fraction that will report to the LAW facility for treatment. Radionuclides of concern in LAW glasses will include 60Co, 137Cs, 154Eu, 99Tc and 90Sr alongside toxic metal contaminants. Conditions in the IDF are expected to differ from those within a deep geological disposal facility for high level waste with temperatures expected to be ~ 15° C, an arid climate, variable pH and groundwater flow rates.

Project GLAD (Glass Leaching Assessment for Disposability) investigates newly developed leaching technologies for assessing the durability of ILAW glasses. Four new methodologies developed by the U.S. Environmental Protection Agency for application to the accelerated ageing of ILAW glass are compared to established leaching tests accepted for evaluation of high level waste glasses, including PCT and MCC-1 protocols. The GLAD project studies the process of glass dissolution and constituent leaching as a function of temperature, pH, groundwater composition and flow rate.

Here, the durability of three candidate glasses were analysed and compared to simplified glasses. Results of ‘Method 1313’, a batch leaching test to assess performance as a function of pH, are compared to results obtained from standard PCT-B and MCC-1 tests.

Fig 1: candidate glasses: ORP-LB2, LAWA23 and LAWA44

Fig 2: pH dependent release of Al from candidate glasses

Funding for this work was provided by William F. Hamel, Jr., Federal Project Director, of the U.S. Department of Energy Waste Treatment & Immobilization Plant Project.

Project collaborators: Pacific Northwest National Laboratory (PNNL) and the Consortium for Risk Evaluation with Stakeholder Participation (CRESP).