Speciation and Fate of Long-Lived, Redox Active Radionuclides in ‘Red Bed’ Mudstones

This PhD project at The University of Manchester investigates the speciation and fate of long-lived, redox active radionuclides—such as uranium, neptunium, selenium, and technetium—in ‘Red Bed’ mudstones, a potential host rock for the UK’s deep Geological Disposal Facility (GDF) for radioactive waste. The Mercia Mudstone Group, characterized by its distinctive red and grey/green coloration due to ferric and ferrous iron phases, is central to the study. Understanding how Fe-bearing minerals and their redox transformations influence radionuclide mobility is crucial for developing a robust safety case for radioactive waste disposal. The research is structured into three main tasks: sourcing and characterizing Red Bed Mudstones (RBMs) with a focus on Fe-bearing phases; investigating the reactions of key radionuclides with RBMs under relevant groundwater and geomicrobiological conditions, including environmental perturbations affecting Fe and S transformations; and, for select systems, examining radionuclide retention using flow-through experiments with bulk analysis and micro-focus imaging techniques. Analytical work will be conducted in the NNUF RADioactive waste management and Environmental Remediation (RADER) laboratories, utilizing advanced solid and liquid chemistry techniques. Methods include XRD, µ-XRF mapping, (µ-)XAS, S(T)EM with Energy Dispersive X-Ray analysis, PCR amplification, Illumina MiSeq 16S rRNA gene sequencing, ICP-MS, ICP-OES, ion chromatography, and spectrophotometry. Thermodynamic geochemical modelling (e.g., PHREEQC) will complement experimental observations, adapting solubility constants to the forms of radionuclide identified in RBMs. Results will be compared to incubation data to assess the predictive relevance of existing geochemical models. The PhD student will gain expertise in environmental (biogeo)chemistry, mineralogy, and state-of-the-art analytical techniques, with training and networking opportunities through the EPSRC-funded CDT SATURN network and NWS Research Support Office. Industrial supervision and collaboration with international partners will enhance the impact and visibility of the project. Participation in national and international conferences is encouraged, and findings will be published open access under the university’s policy. Applicants should have at least a 2.1 honours degree or a master’s in a relevant science or engineering discipline. Flexible study arrangements may be available. The EPSRC funded studentship covers full tuition fees at the Home student rate and a maintenance grant for 4 years (£20,780 pa for 2025-2026), with possible fee waivers for international candidates not requiring ATAS clearance. Additional funding is available for research training support. Applications are accepted year-round, and candidates are strongly encouraged to contact the project supervisors for informal enquiries and to discuss suitability before applying. For further information, see the project listing and contact supervisors at [email protected] and [email protected]. The application process is detailed on the SATURN CDT website. The University of Manchester is committed to equality, diversity, and inclusion, welcoming applicants from all backgrounds and offering flexible study options.