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Vitrification of simulated highly active calcines containing high concentrations of sodium and molybdenum

Published online by Cambridge University Press:  20 February 2017

Mike T. Harrison  and
Carl J. Steele
Mike T. Harrison*
Affiliation:
National Nuclear Laboratory, Sellafield, Seascale, Cumbria, CA20 1PG, UK.
Carl J. Steele
Affiliation:
Sellafield Ltd, Sellafield, Seascale, Cumbria, CA20 1PG, UK.
*
*(Email: mike.t.harrison@nnl.co.uk)
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Abstract

Sodium carbonate is currently being considered as a wash-out reagent for the removal of the settled solids in the unagitated Highly Active Liquor (HAL) storage tanks at Sellafield. As the settled solids are expected to comprise mainly zirconium molybdate (ZM), this will result in a challenging feed to the Waste Vitrification Plant (WVP) containing high concentrations of both molybdenum and sodium.

In previous studies, it was shown that at high wash-out waste loadings, i.e. 10 – 12 wt% MoO3 incorporation, there was very little tolerance in ‘Ca/Zn’ base glass for extra sodium before the formation of significant separated sodium molybdate salt phase. However, higher amounts of sodium can be accommodated in borosilicate glasses if the wash-out waste loading is reduced. Further studies have now been carried out to investigate the vitrification of more representative calcined waste feeds. Both pure zirconium molybdate (ZM) and blended ZM-reprocessing waste calcines were produced from the appropriate liquor feeds. The maximum waste incorporations of these two calcines in ‘Ca/Zn’ base glass have been determined, along with a complete product quality assessment. This assessment included measuring the bulk density, degree of crystallinity, heat treatment, durability (Soxhlet and PCT), glass transition temperature, and viscosity.

Keywords

SiMowaste management
Type
Articles
Information
MRS Advances , Volume 1 , Issue 63-64: Scientific Basis for Nuclear Waste Management XXXIX , 2016 , pp. 4233 - 4238
Copyright
Copyright © Materials Research Society 2017 

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References

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