The initial dissolution rates of simulated UK Magnox-ThORP blend nuclear waste glass as a function of pH, temperature and waste loading

The first comprehensive assessment of the dissolution kinetics of simulant Magnox-ThORP blended UK high-level waste glass, obtained by performing a range of single-pass flow-through experiments, is reported here. Inherent forward rates of glass dissolution were determined over a temperature range of...

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Bibliographic Details
Published in:Mineralogical magazine 2015-11, Vol.79 (6), p.1529-1542
Main Authors: Cassingham, N, Corkhill, C. L, Backhouse, D. J, Hand, R. J, Ryan, J. V, Vienna, J. D, Hyatt, N. C
Format: Article
Language:English
Subjects:
dissolution mechanism
Environmental geology
Europe
geological disposal
glass
glass materials
high-level waste
kinetics
Magnox
MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
mechanism
radioactive waste
simulation
solution
temperature
THORP
UK Magnox
United Kingdom
waste disposal
waste glass
waste loading
Western Europe
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Summary:The first comprehensive assessment of the dissolution kinetics of simulant Magnox-ThORP blended UK high-level waste glass, obtained by performing a range of single-pass flow-through experiments, is reported here. Inherent forward rates of glass dissolution were determined over a temperature range of 23 to 70°C and an alkaline pH range of 8.0 to 12.0. Linear regression techniques were applied to the TST kinetic rate law to obtain fundamental parameters necessary to model the dissolution kinetics of UK high-level waste glass (the activation energy (Ea), pH power law coefficient (η) and the intrinsic rate constant (k0)), which is of importance to the post-closure safety case for the geological disposal of vitreous products. The activation energies based on B release ranged from 55±3 to 83±9 kJ mol-1, indicating that Magnox-THORP blend glass dissolution has a surface-controlled mechanism, similar to that of other high-level waste simulant glass compositions such as the French SON68 and LAW in the US. Forward dissolution rates, based on Si, B and Na release, suggested that the dissolution mechanism under dilute conditions, and pH and temperature ranges of this study, was not sensitive to composition as defined by HLW-incorporation rate.
ISSN:0026-461X
1471-8022
DOI:10.1180/minmag.2015.079.6.28