Background
Long-lived radioactive elements such as uranium (U), neptunium (Np), selenium (Se), and technetium (Tc) are significant risk drivers in the disposal of radioactive wastes, and understanding their fate in the host rock environment underpins development of the safety case for a deep Geological Disposal Facility (GDF) to safely dispose of UK’s higher activity radioactive wastes. The so-called ‘Red Bed’ mudstones from the Triassic-aged Mercia Mudstone Group, that exhibit a characteristic red colour due to the presence of ferric iron and also exhibit a grey/green colour presumably due to ferrous bearing phases, are a potential host rock candidate for the UK’s GDF. In this project we will seek to understand, through a series of well-designed laboratory experiments, the speciation and fate of long-lived, redox active radionuclides in contact with RBMs. We will explore how the Fe-bearing minerals present in these deposits, and in particular their redox transformations, might play an important role in controlling the long-term mobility of the radionuclides at depth. This in turn will provide new, and better constrained underpinning data to support the design and development of a relevant safety case for a GDF in ‘Red Bed’ mudstones.
We will investigate the fate of long-lived, redox active radionuclides (e.g., U, Np, Se and Tc) in ‘Red Bed’ Mudstones (RBMs) in three tasks:
a) Sourcing and characterizing RBMs, focusing on the Fe-bearing phases which may impact Eh and radionuclide sequestration.
b) Selecting key radionuclides and investigating their reactions with RBMs in batch systems under relevant groundwater and geomicrobiological conditions, and for environmental perturbations (Eh, (bio)geochemical gradients) known to affect Fe and S transformations and radionuclide behaviour.
c) For select systems from b), investigation of radionuclide retention using flow through experiments by combining bulk analysis and micro-focus imaging techniques.
Analytical approach:
The project will be conducted in the NNUF RADioactive waste management and Environmental Remediation (RADER) (https://www.nnuf.ac.uk/rader) laboratories. We will combine solid and liquid chemistry techniques to investigate the speciation and mobility of Fe and S, and the selected radionuclides. XRD, µ-XRF mapping, (µ-)XAS, and S(T)EM coupled with Energy Dispersive X-Ray analysis will be used to investigate Fe, S and radionuclide distribution and speciation by application to external facilities where necessary. Changes in microbial profiling will be investigated via PCR amplification and in house Illumina MiSeq 16S rRNA gene sequencing (with qPCR for functional gene analysis as required). The liquid phase will be monitored using Inductively Coupled Plasma Mass Spectrometry (ICP-MS), Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES), ion chromatography (IC), and spectrophotometry analyses. Thermodynamic geochemical modelling will be performed (e.g., using PHREEQC) to complement the experimental observations, using thermodynamic solubility constants adapted to the forms of radionuclide identified in the RBMs. Results will be compared to our incubation data to assess the relevance of existing geochemical model to predict radionuclides solubility under these environmental conditions.
Training, Knowledge Exchange and Impact:
The PhD student will gain knowledge in the field of environmental (biogeo)chemistry & mineralogy applied to the study of radionuclide behaviour in complex environments, and will gain expertise in state-of-the-art liquid and solid chemistry techniques. They will also have an industrial supervisor who is a subject matter expert, and through that interaction, they will learn about the importance of research and data informing radioactive waste management. These skills are highly desirable in the nuclear decommissioning and disposal community in academia and industry. The PhD student will join the NWS funded Research Support Office and will be co-funded through the EPSRC-funded CDT SATURN network, and will benefit from the networking and training opportunities that offers.
The PhD student and academic supervisors will work with the NWS subject matter expert to embed and support the direction of the experimental and modelling programme. The project will also be affiliated to the NWS Research Support Office and with international partners to provide wider networking and visibility of the project. Other networking opportunities include participation in national (e.g., Radiochemistry Group events, Mineralogical Society Events), European (EURAD2) and international (e.g., Migration, Goldschmidt) conferences and seminars. Finally, findings from this work will be published in open access under the University of Manchester open access policy to enable visibility and accessibility to the wider academic and industrial community.
Before you apply
We strongly recommend that you contact the project supervisors before applying. For informal enquiries, contact Katherine.morris@manchester.ac.uk & lucie.stetten@manchester.ac.uk
The studentship will be run as part of the SATURN Centre for Doctoral Training and thus you will get to interact with a large cohort of students who are studying nuclear science and engineering at six leading UK universities.
Eligibility
Applicants should have, or expect to achieve, at least a 2.1 honours degree or a master’s (or international equivalent) in a relevant science or engineering related discipline
How to apply
Please complete the enquiry form to express your interest.
We strongly recommend you contact the project supervisor after completing the form to speak to them about your suitability for the project. You can find their details on the project listing.
If your qualifications meet our standard entry requirements, the CDT Admissions Team will send your enquiry form and CV to the named project supervisor.
Our application process can also be found on our website: Apply | EPSRC Centre for Doctoral Training in Skills And Training Underpinning a Renaissance in Nuclear | The University of Manchester. If you have any questions, please contact SATURN@manchester.ac.uk
Equality, diversity and inclusion
Equality, diversity and inclusion is fundamental to the success of The University of Manchester, and is at the heart of all of our activities. We know that diversity strengthens our research community, leading to enhanced research creativity, productivity and quality, and societal and economic impact.
We actively encourage applicants from diverse career paths and backgrounds and from all sections of the community, regardless of age, disability, ethnicity, gender, gender expression, sexual orientation and transgender status.
We also support applications from those returning from a career break or other roles. We consider offering flexible study arrangements (including part-time: 50%, 60% or 80%, depending on the project/funder).
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