Basic science in support of thermal treatment strategy

Basic science in support of thermal
treatment strategy
Neil Hyatt
University of Sheffield
[email protected]
Why we need basic science
Thermal treatment technologies will process
a variety of waste types, producing a wide
spectrum of new wasteforms
Understanding the fundamental materials
science is required to underpin:
Current & recently completed UoS projects
Martin Stennett: Radiation damage of ceramics
Amy Gandy: Radiation damage in glass
Claire Corkhill: Wasteform dissolution
• Products
Owen McGann: IEX resin vitrification
• Processes
Paul Heath: Hot Isostatic Pressing for ILW
• Disposal
Luke Boast: Thermal treatment of PCM
Hence, there is a clear need to develop
fundamental understanding in parallel with
technology development.
Ricardo Curi: Thermal treatment of clinoptilolite
Two examples:
• Thermal treatment of PCM with BFS
• Glass dissolution at hyperalkaline pH
See: Hyatt & James, Nucl. Eng. Int., Feb. (2013).
Steph Thornber: Glass ceramics for Pu residues
Jon Squire: HIP processing of Pu residues
Rob Shaw: Calcination of HLW
James Stevens: Crystallisation of HLW glass
Laura Casey: Pyrochlore ceramics Pu
Hao Zhang: Magnox sludge vitrification
Thermal treatment of PCMs
Current baseline technology
Super-compaction and cement encapsulation
Cannot treat non-compactable PCM
Pu is not chemically or physically immobilised
Organic inventory remains intact
Thermal treatment wish list
Target: slag / metal wasteform (metal to LLW, recycle?)
• Single process to treat all drums
• Treat drums in entirety (inc. drum, no separation)
• Immobilisation and homogeneous distribution of Pu
• Destroy / passivate reactive material
• Achieve product with acceptable durability
Hyatt et al., J. Nucl. Mater, 444 (2014) 186.
Thermal treatment of PCMs
Proof of concept approach
Four generic waste types, defining envelope:
•
•
•
•
Metal waste
Masonry waste
PVC waste
Mixed waste
Utilise blast furnace slag as single additive
Target melting temperature of 1560 oC
Ce used as Pu surrogate
Laboratory mock ups of waste canisters
Achieve volume reduction of 80-90%
Hyatt et al., J. Nucl. Mater, 444 (2014) 186.
Thermal treatment of PCMs
Hyatt et al., J. Nucl. Mater, 444 (2014) 186.
Thermal treatment of PCMs
10 µm
Hyatt et al., J. Nucl. Mater, 444 (2014) 186.
Thermal treatment of PCMs
Hyatt et al., J. Nucl. Mater, 444 (2014) 186.
Thermal treatment of PCMs
Hyatt et al., J. Nucl. Mater, 444 (2014) 186.
Performance of vitrified products
Disposability of thermally treated products
Likely to be vitrified materials
Option to dispose of vitrified products in ILW vaults
A hyperalkaline backfill material may be utilised
Two key questions
Are the general mechanisms of glass dissolution valid
under hyperalkaline conditions?
Could glass dissolution compromise the buffering
capacity of the backfill?
Experiments: simulant borosilicate waste glass,
dissolved in deionised water or saturated Ca(OH)2
solution, at 50 oC under nitrogen gas, using a surface
area / volume ratio of 10,000 m-1.
Corkhill et al., Int. J. Appl. Glass Sci., 6 (2013) 1-16
Utton et al., J. Nucl. Mat., 435 (2013) 112–122
Utton et al., J. Nucl. Mat., 442 (2013) 33–45.
Performance of vitrified products
Water
Ca(OH)2
Ca(OH)2
Blank
Corkhill et al., Int. J. Appl. Glass Sci., 6 (2013) 1-16
Utton et al., J. Nucl.
Mat.,
435
(2013) 112–122
Corkhill
et al.
International
Journal of Applied Glass Science (2013)
Utton et al., J. Nucl.
Mat.,
442
(2013)
33–45.
DOI:10.1111/ijag.12042
Performance of vitrified products
Corkhill et al., Int. J. Appl. Glass Sci., 6 (2013) 1-16
Utton et al., J. Nucl.
Mat.,
435
(2013) 112–122
Corkhill
et al.
International
Journal of Applied Glass Science (2013)
Utton et al., J. Nucl.
Mat.,
442
(2013)
33–45.
DOI:10.1111/ijag.12042
Performance of vitrified products
Corkhill et al., Int. J. Appl. Glass Sci., 6 (2013) 1-16
Utton et al., J. Nucl.
Mat.,
435
(2013) 112–122
Corkhill
et al.
International
Journal of Applied Glass Science (2013)
Utton et al., J. Nucl.
Mat.,
442
(2013)
33–45.
DOI:10.1111/ijag.12042
Performance of vitrified products
1. Incubation regime:
Incorporation of Ca into the hydrated glass surface
and precipitation of M-S-H phases
2. Intermediate regime:
Precipitation of C-S-H phases, including a range of
compositions in the C-(N)-(A)-S-H and M-S-H
systems; rapid Si dissolution
3. Residual regime:
Precipitation of lower Ca/Si ratio C-S-H phases;
steady concentration of Ca; slower dissolution of Si
Note: this a simplified system but clearly complex
-Equilibrated cement waters are more complex
-Glass composition has strong effect on mechanism
-Possibility for RNs to be incorporates in SAPs
Corkhill et al., Int. J. Appl. Glass Sci., 6 (2013) 1-16
Utton et al., J. Nucl. Mat., 435 (2013) 112–122
Utton et al., J. Nucl. Mat., 442 (2013) 33–45.
Conclusions & Acknowledgements
Conclusions
Wasteform science has a key role to play in
developing any future thermal treatment
strategy by underpinning:
• Products
• Processes
• Disposal
In particular, by optimising wasteform
quality and performance, through materials
science, we can improve public confidence in
geological disposal as well as enhancing the
safety margin of the disposal system safety
case.
Acknowledgements
UoS: Nate Cassingham, Claire Corkhill, Paul Heath, Owen
McGann, Ros Schwarz, Andrew Connelly, Martin Stennett,
Paul Bingham, Russell Hand.
Sellafield Ltd: Mike James, Sean Morgan, Andrew Pearson,
Magnox: Linda Rust, Tony Burdett
BNL / NSLS: Bruce Ravel
Sponsorship

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