Vitrified nuclear waste durability in complex natural environments
Lead Research Organisation:
University of Sheffield
Department Name: Materials Science and Engineering
Abstract
Understanding the long-term durability of nuclear waste glass in the subsurface is important in the UK and internationally as many countries intend to dispose of vitrified radioactive waste in underground geological disposal facilities. In order to ensure safe disposal, we need to be confident that radioactive elements will remain isolated and immobilised for sufficient time to allow radioactivity to decay to safe levels. There will be multiple barriers in place (e.g. a metal container and engineered backfill) to delay groundwater from reaching the nuclear waste glass but eventually contact with water is expected. Although there are a number of laboratory tests currently used to determine the rate of glass dissolution in water all accelerate corrosion by increasing the temperature, surface area, or both and give very different predictions depending on the test conditions. Laboratory tests are also performed under simplified, stable, sterile conditions and using deionised water taking no account of how changing geochemical conditions will affect glass corrosion rates. This fellowship will combine materials science, geochemistry and geomicrobiology to study how glass corrodes in real-time in dynamic complex natural environments. I will improve understanding of key factors affecting corrosion (temperature, groundwater geochemistry, saturation, and microbiology) using the Ballidon long duration experiment, where glass samples have been buried for nearly 50 years. To predict the durability of nuclear waste glass thousands of years into the future I will study simulant nuclear waste glass's in conditions relevant to UK and US disposal concepts. The result of this novel investigation will be to critically evaluate, and improve, upon durability tests for glass, to build an improved model of glass corrosion and to establish further long duration experiments to inform the safety case for geological disposal in the UK and abroad.
Planned Impact
My research into glass durability in complex natural environments will directly impact upon beneficiaries in the UK nuclear industry including governmental policy makers 'Radioactive Waste Management' (RWM) responsible for carrying out the government's policy to dispose of high level vitrified waste in a Geological Disposal Facility (GDF). The fellowship directly addresses three key areas within RWM's "Geodisposal Science and Technology Plan 2016" and advances understanding of vitrified waste dissolution under UK relevant burial conditions. Furthermore, through improvements to current dissolution tests, this research will benefit companies developing glass compositions under consideration for the immobilisation of UK legacy intermediate level waste streams (e.g. Geomelt Ltd, National Nuclear Laboratories and the University of Sheffield). Improved low temperature dissolution tests will be investigated as part of this fellowship and could be applied to non-heat generating vitrified intermediate level wastes.
This science is also of interest to policy makers abroad particularly the US Department of Energy, responsible for disposal of US vitrified radioactive wastes. The study of glass dissolution under variable saturation, low temperatures, and changing groundwater composition (work packages 2-5) is pertinent to the safety case for a newly constructed Integrated Disposal Facility for low activity waste at the Hanford Site, Washington State, US. In addition, a number of US simulant glasses have been buried at the Ballidon site (the main natural analogue site studied) and the advanced site characterisation proposed during this fellowship will assist in interpretation of corrosion on those samples. Beneficiaries include Pacific North-West National Laboratories and Savannah River Laboratories who are both involved in ongoing research into US glass durability and collaborative work with the UK. In Europe, my findings and method development will be of interest to other countries working towards geological disposal of vitrified radioactive wastes and at a similar or more advanced stage of GDF implementation including France, Belgium, Sweden and Finland.
This research advances the underpinning science for the proposed UK GDF and, therefore, may help to answer questions posed by environmental groups and members of the public concerned with the safe disposal of vitrified radioactive waste. This research is timely as the RWM will begin another round of consultations in 2018 to allow potential volunteer communities to come forward to discuss hosting the UK GDF. This body of research will contribute to the underpinning science available for members of the public to access during this consultation phase.
Despite the applied nature of this fellowship experiments will advance the fundamental understanding of glass corrosion that may also interest other communities concerned with glass durability. For example work package 3, investigating the role of microorganisms in glass corrosion, may be of interest to archaeologists interesting in ancient glass sample preservation. Furthermore, improved prediction of glass durability under a range of geochemical conditions may interest commercial glass manufacturers (e.g. for the construction industry, semiconductors, scientific instruments).
This science is also of interest to policy makers abroad particularly the US Department of Energy, responsible for disposal of US vitrified radioactive wastes. The study of glass dissolution under variable saturation, low temperatures, and changing groundwater composition (work packages 2-5) is pertinent to the safety case for a newly constructed Integrated Disposal Facility for low activity waste at the Hanford Site, Washington State, US. In addition, a number of US simulant glasses have been buried at the Ballidon site (the main natural analogue site studied) and the advanced site characterisation proposed during this fellowship will assist in interpretation of corrosion on those samples. Beneficiaries include Pacific North-West National Laboratories and Savannah River Laboratories who are both involved in ongoing research into US glass durability and collaborative work with the UK. In Europe, my findings and method development will be of interest to other countries working towards geological disposal of vitrified radioactive wastes and at a similar or more advanced stage of GDF implementation including France, Belgium, Sweden and Finland.
This research advances the underpinning science for the proposed UK GDF and, therefore, may help to answer questions posed by environmental groups and members of the public concerned with the safe disposal of vitrified radioactive waste. This research is timely as the RWM will begin another round of consultations in 2018 to allow potential volunteer communities to come forward to discuss hosting the UK GDF. This body of research will contribute to the underpinning science available for members of the public to access during this consultation phase.
Despite the applied nature of this fellowship experiments will advance the fundamental understanding of glass corrosion that may also interest other communities concerned with glass durability. For example work package 3, investigating the role of microorganisms in glass corrosion, may be of interest to archaeologists interesting in ancient glass sample preservation. Furthermore, improved prediction of glass durability under a range of geochemical conditions may interest commercial glass manufacturers (e.g. for the construction industry, semiconductors, scientific instruments).
Organisations
- University of Sheffield (Fellow, Lead Research Organisation)
- Natural Environment Research Council (Co-funder)
- Vanderbilt University (Collaboration)
- SELLAFIELD LTD (Collaboration)
- U.S. Department of Energy (Collaboration)
- University of Manchester (Project Partner)
- Nuclear Decommissioning Authority (Project Partner)
- United States Department of Energy (Project Partner)
Publications
![publication icon](/resources/img/placeholder-60x60.png)
Corkhill C
(2022)
Surface interfacial analysis of simulant high level nuclear waste glass dissolved in synthetic cement solutions
in npj Materials Degradation
![publication icon](/resources/img/placeholder-60x60.png)
Hyatt N
(2020)
The HADES Facility for High Activity Decommissioning Engineering & Science: part of the UK National Nuclear User Facility
in IOP Conference Series: Materials Science and Engineering
![publication icon](/resources/img/placeholder-60x60.png)
Mansfield J
(2023)
Localised extended ("vermiform") features formed during glass dissolution
in Journal of Non-Crystalline Solids
![publication icon](/resources/img/placeholder-60x60.png)
Nava-Farias L
(2021)
Applying laboratory methods for durability assessment of vitrified material to archaeological samples
in npj Materials Degradation
![publication icon](/resources/img/placeholder-60x60.png)
Thorpe C
(2021)
Forty years of durability assessment of nuclear waste glass by standard methods
in npj Materials Degradation
![publication icon](/resources/img/placeholder-60x60.png)
Thorpe C.L.
(2019)
Evaluation of novel leaching assessment for nuclear waste glasses
in Radwaste Solutions
![publication icon](/resources/img/placeholder-60x60.png)
Thorpe CL
(2024)
Microbial interactions with phosphorus containing glasses representative of vitrified radioactive waste.
in Journal of hazardous materials
Title | Vitrified Nuclear Waste Sculpture |
Description | Designed in collaboration with blacksmith artist John Mallett, this sculpture represents the structure of the glass network within a steel nuclear waste canister. The work is comprised of glass and steel and intended to be transported to outreach events and, in the meantime, displayed in the Turner museum of glass, University of Sheffield. |
Type Of Art | Artwork |
Year Produced | 2021 |
Impact | None yet, it has just been completed |
Description | The main focus of this Fellowship was the Ballidon long-term burial experiment where glasses of archaeological, modern and nuclear waste type composition were buried in a shallow subsurface environment for 20-50 years. Differences were observed between glass samples altered in this complex natural environment and those altered using simplified laboratory test methods. In particular the role of elements sourced from the groundwater and adjacent minerals were found to be important in controlling the dissolution rate of nuclear type glasses and in creating alteration layers that were chemically and structurally different from those observed in laboratory experiments. To further explore the inclusion of elements from outside, glasses from other natural environments were studied including an early Victorian era glass bottle, glasses from a vitrified Swedish hillfort, shipwreck glass from a 250 year old wreck and glasses from the Peak Dale Cave. An experiment designed to last 10 + years was emplaced into the Peak Dale Cave site where porewaters have a pH > pH 13 and represents conditions in a cementitious environment. Key findings from this work: 1) Elements like Fe, Ca and P are sequestered to the glass alteration layer even if not present in the glass. These elements have the potential to affect the dissolution rate of glass through controlling the mineralogy of the alteration layer. Results suggest that, under some conditions, Fe can combine with P in glass alteration layers to precipitate Fe(III)-phosphate phases that may accelerate glass dissolution by disrupting the passivating effect of the silica gel layer. However, where Ca is also present, P preferentially associates with Ca to form amorphous Ca-rich layers. Where Pb or the lanthanide elements are present in glass, these preferentially bind to available P and the resulting precipitates resemble Pb or lanthanide phosphates, likely precursors to apatite phases. Phosphate phases are favorable in a nuclear waste disposal scenario as they sequester lanthanide fission products and actinide elements. 2) The effect of microbial metabolism was also investigated and microbial metabolism was found to be stimulated by the presence of P and Fe in glasses. Microbial reduction of Fe(III) to Fe(II) appeared to reduce the rate of glass corrosion likely as Fe(II) is more soluble and does not sequester to the alteration layer so readily or form Fe(III)phosphates or Fe(III)silicates. Although Fe(III) reduction does take place it does not appear the microbes are directly attacking the glass in these experiments. It was also noted, during experiments with Shipwreck glasses containing Pb, Cu and Co that these biocidal elements deterred barnacle settlement and experiments are ongoing to test if these elements have a similar effect on bacterial colonization of glass surfaces. 3) Analysis of glasses from long term burial experiments have shed some light on the long-term evolution of glass alteration layers, and the formation of layers/zones within them. The structure of most layers appears x-ray amorphous but further work is underway to ascertain if nano-crystalline or poorly crystalline phases form over time. Overall, through presentations at international conferences, attendance at glass alteration workshops (e.g. GOMD 2023) and long term collaborations with other research groups (for example PNNL in the USA) I have promoted the fact that processes occurring only complex natural environments have an important impact on glass dissolution processes. There is a trend towards computational modelling at the atomic scale and oversimplification of systems to accommodate this. My research has shown that there are important influences, such as Ca and P influx from groundwater and Fe(II) reduction by microbial life, that play a significant role in glass dissolution and are unaccounted for in glass dissolution models. |
Exploitation Route | This work is directly applicable in the UK, USA and France to contribute to the understanding of glass dissolution and feed into the safety case for subsurface disposal of vitrified radioactive wastes. France has a large volume of vitrified waste and are implementing radioactive waste disposal in a clay based geology (the French CEA have twice invited me to talk at their conferences). The USA DOE are interested in this work as they are currently working on the safety case for disposal of LAW glass in the Integrated disposal facility (Hanford Site, USA). I work closely with glass scientists from PNNL and have contributed to reviewing a report that integrates glass testing with the performance assessment for glass burial. My work is likely to be used to make the case for testing using on-site groundwater and for consideration of the steel canister in the performance assessment. In the UK both Nuclear Waste Services and Sellafield Ltd have show interest in this work from the point of view of disposal of existing High Level Waste and future disposal of Intermediate Level Waste (if thermal treatment is chosen as the treatment route for ILW). Sellafield has formed a centre of excellence between the University of Sheffield, the University of Bristol and Sheffield Hallam and has expressed and interest in this area. In the academic world the work has raised questions about the accepted model of glass dissolution and the role of external elements in alteration layer evolution. The work has lead to a number of interesting collaborations that will be pursued through applications for further funding. Work conducted on microbial interactions with glass surfaces could be interesting to companies looking to create biocidal glasses or glasses that release elements in a natural setting (such as poorly durable glasses for glass based fertilizers). This work stimulated further lines of research that have resulted in my successful application for a Royal Society Dorothy Hodgkin Fellowship (commenced Jan, 2024). |
Sectors | Energy Environment |
URL | https://www.envchemgroup.com/natural-analogues-nuclear-waste.html |
Description | EPSRC Energy and Decarbonisation Event |
Geographic Reach | National |
Policy Influence Type | Participation in a guidance/advisory committee |
Description | International Reviewer for PNNL report draft: ILAW Glass Program Summary report |
Geographic Reach | North America |
Policy Influence Type | Participation in a guidance/advisory committee |
Description | Participation in EPSRC nuclear international workshop |
Geographic Reach | National |
Policy Influence Type | Participation in a guidance/advisory committee |
Description | Grants for Carers |
Amount | £800 (GBP) |
Organisation | Royal Society of Chemistry |
Sector | Charity/Non Profit |
Country | United Kingdom |
Start | 02/2024 |
End | 08/2024 |
Description | HADES: A User Facility for High Activity Decommissioning Engineering Science |
Amount | £658,445 (GBP) |
Funding ID | EP/T011424/1 |
Organisation | Engineering and Physical Sciences Research Council (EPSRC) |
Sector | Public |
Country | United Kingdom |
Start | 01/2020 |
End | 05/2023 |
Description | Influence of subsurface microbiology on the dissolution of nuclear waste glasses containing redox active metals" (Experiment 95, NNUF call 8) |
Amount | £16,000 (GBP) |
Organisation | Engineering and Physical Sciences Research Council (EPSRC) |
Sector | Public |
Country | United Kingdom |
Start | 08/2022 |
End | 04/2023 |
Description | Microbes, minerals and material heterogeneity; how (bio)geochemical processes affect the long term durability of glassy materials. |
Amount | £1,435,941 (GBP) |
Organisation | The Royal Society |
Sector | Charity/Non Profit |
Country | United Kingdom |
Start | 01/2024 |
End | 01/2032 |
Description | Platform for Long-term Experimental Investigation of Alteration in Disposal Environments and Storage - PLEIADES |
Amount | £597,980 (GBP) |
Funding ID | EP/V035215/1 |
Organisation | Engineering and Physical Sciences Research Council (EPSRC) |
Sector | Public |
Country | United Kingdom |
Start | 09/2021 |
End | 09/2023 |
Description | Radioactive Waste Management Research Support Office PhD Studentship Call |
Amount | £78,000 (GBP) |
Funding ID | RWM430-04 |
Organisation | Nuclear Decommissioning Authority NDA |
Department | Radioactive Waste Management |
Sector | Public |
Country | United Kingdom |
Start | 08/2021 |
End | 08/2025 |
Description | Royal Society of Chemistry Grants for Carers |
Amount | £610 (GBP) |
Organisation | Royal Society of Chemistry |
Sector | Charity/Non Profit |
Country | United Kingdom |
Start | 09/2019 |
End | 11/2019 |
Description | Royal Society of Chemistry Research Fund |
Amount | £2,973 (GBP) |
Funding ID | R20-4913 |
Organisation | Royal Society of Chemistry |
Sector | Charity/Non Profit |
Country | United Kingdom |
Start | 02/2021 |
End | 02/2022 |
Description | Centre of Expertise for Thermal and Immobilisation (Sellafield Ltd.) |
Organisation | Sellafield Ltd |
Country | United Kingdom |
Sector | Private |
PI Contribution | Centre of Expertise for Thermal and Immobilisation (Sellafield Ltd.) was applied for and won by The University of Sheffield, Sheffield Hallam and the University of Bristol. As a member of the consortium but not the leading academic I have benefited from regular discussions with Sellafield representative Helen Steel with whom I have already submitted and application for a PhD bursary and Sellafield has pledged 70k in match funding. |
Collaborator Contribution | Partners contribute a direct pathway to impact for any work done as part of this collaboration. As part the the Thermal Treatment Centre for excellence any work done by myself or any member of my team will be communicated directly to the stakeholders (the Sellafield team considering thermal treatment for Intermediate Level Wastes). Sellafield have also pledge 70 match funding for a Sheffield based student. |
Impact | This partnership has only been in place for two months |
Start Year | 2024 |
Description | Project GLAD: Glass leaching Assessment for Disposability |
Organisation | U.S. Department of Energy |
Department | Pacific Northwest National Laboratory |
Country | United States |
Sector | Public |
PI Contribution | Monthly meeting to discuss aspects of the GLAD project, review manuscripts, co-author manuscripts and co-supervise a PDRA from October 2020. |
Collaborator Contribution | Co-authoring manuscripts, sharing and discussing new data, contributing to a review of glass alteration testing. Sharing of samples LAW A44, ISG, and a high phosphate sample. Co-authoring of a Smithsonian Volume on the Hill Fort project. |
Impact | Publication: Smithsonian Volume (multi-disciplinary) Glass science, archaeology, environmental science. Publication: VALIDATION AND USE OF A pH-DEPENDENCE LEACHING TEST FOR EVALUATION OF LOW ACTIVITY NUCLEAR WASTE GLASSES |
Start Year | 2019 |
Description | Project GLAD: Glass leaching Assessment for Disposability |
Organisation | Vanderbilt University |
Country | United States |
Sector | Academic/University |
PI Contribution | Monthly meeting to discuss aspects of the GLAD project, review manuscripts, co-author manuscripts and co-supervise a PDRA from October 2020. |
Collaborator Contribution | Co-authoring manuscripts, sharing and discussing new data, contributing to a review of glass alteration testing. Sharing of samples LAW A44, ISG, and a high phosphate sample. Co-authoring of a Smithsonian Volume on the Hill Fort project. |
Impact | Publication: Smithsonian Volume (multi-disciplinary) Glass science, archaeology, environmental science. Publication: VALIDATION AND USE OF A pH-DEPENDENCE LEACHING TEST FOR EVALUATION OF LOW ACTIVITY NUCLEAR WASTE GLASSES |
Start Year | 2019 |
Description | The Hillfort Project |
Organisation | U.S. Department of Energy |
Department | Pacific Northwest National Laboratory |
Country | United States |
Sector | Public |
PI Contribution | Monthly meeting are held virtually to discuss the progress of the Hillfort Project and to showcase results from the project. Future directions are discussed and possible additional natural analogues that could be used. Representatives from the University of Sheffield are present at all of these meetings and contribute frequently including to reviewing publication outputs from this project. We have also shared best practice on sample preparation and new experimental techniques. |
Collaborator Contribution | The Hillfort project is run and funded by PNNL and researchers from the University of Sheffield (myself and Russell Hand) take the part of advisers and reviewers of the data. The team at PNNL are investigating both vitrified hillfort material and iron age slag alongside collaborators from Sweden, Israel, US and UK. |
Impact | The collaboration is multi-disciplinary encompassing glass/materials science, geochemistry, microbiology and archaeology. There have been a number of academic publications from this work one of which was published this year and included in the publication section and two that are in the submission process. The collaboration is also writing a publication for the Smithsonian museum that is due out next year. The Hillfort Project is tied into the GLAD project which aims to change the test used to accept vitrified radioactive waste into the Integrated Disposal Facility at the Hanford site USA. This will have an impact on policy at the site. |
Start Year | 2019 |
Description | Article for Physics World |
Form Of Engagement Activity | A magazine, newsletter or online publication |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Public/other audiences |
Results and Impact | An interview was given to Rachel Brazil who wrote an article for physics world quoting extracts from the interview and showcasing the research. https://physicsworld.com/a/a-glassy-solution-to-nuclear-waste/ |
Year(s) Of Engagement Activity | 2022 |
URL | https://physicsworld.com/a/a-glassy-solution-to-nuclear-waste/ |
Description | NWS/RSO Knowledge Capture & Safety Case Impact Trial |
Form Of Engagement Activity | Participation in an activity, workshop or similar |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Industry/Business |
Results and Impact | RSO Knowledge Capture & Safety Case Impact Trial. Two workshops led by Alexander Carter and Katherine Raines to investigate how to include academic research into the NWS virtual safety case (ViSi). |
Year(s) Of Engagement Activity | 2022,2023 |
Description | Natural analogues for nuclear waste: a window into the future? |
Form Of Engagement Activity | A magazine, newsletter or online publication |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Other audiences |
Results and Impact | I was invited to write an article for the Environmental Chemistry Interest Group. ECG Bulletin July 2021. This article is available to the public online but also circulated to members of the special interest group. This article has lead to a science journalist requesting an interview about a longer article for a special issue of physics world. |
Year(s) Of Engagement Activity | 2021 |
URL | https://www.envchemgroup.com/natural-analogues-nuclear-waste.html |
Description | Short film about the Ballidon project |
Form Of Engagement Activity | A broadcast e.g. TV/radio/film/podcast (other than news/press) |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Public/other audiences |
Results and Impact | In collaboration with an Archaeology PhD student from the University of Sheffield a short film was made about the Ballidon project. It was shown at the Society for Glass Technology Conference and can now be viewed on the University of Sheffield's webpages. |
Year(s) Of Engagement Activity | 2022 |
URL | https://player.sheffield.ac.uk/events/ballidon-experiment |
Description | Stourbridge International Festival of Glass |
Form Of Engagement Activity | Participation in an activity, workshop or similar |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Public/other audiences |
Results and Impact | Students and staff manned a stand at the Stourbridge International Festival of Glass over the weekend of the 25th-26th August 2022. The stand focused on the role of glass in radioactive waste disposal and science used to design this glass and predict it's longevity. Prof Claire Corkhill gave a talk to the public about glass formed after the Fukushima nuclear accident and students talked to members of the public about nuclear waste disposal. A new collaboration was formed with a glass artist who specialises in uranium glass. Leaflets and information regarding radioactive waste disposal were distributed. |
Year(s) Of Engagement Activity | 2022 |
URL | https://www.ifg.org.uk/ |