PhD Projects at Manchester

These projects are run by The University of Manchester. Application information can be found in our how to apply section.  Please contact the relevant person below before applying. Click on the titles below to see contact details and more information.

  • Long-term interactions of radionuclides with iron oxyhydroxides in geodisposal and contaminated land environments: A combined abiotic and biological study. ***N.B Applications are no longer being considered for this project***

    ***N.B Applications are no longer being considered for this project***

     

    Contact: Dr Sam Shaw

    The UK has a substantial legacy of nuclear wastes and its safe management is a national priority. Understanding the long-term fate of radionuclides in the environment is key to developing safe management of radioactive wastes and radioactively contaminated land. In radioactive waste disposal, during evolution of the repository, iron oxyhydroxides will be present in wastes and will also form from the corrosion of steel canisters and engineering iron. Recent studies have indicated that iron oxyhydroxides can incorporate a range of radionuclides, including actinides [1-3] and Tc [4]. These sequestration processes have the potential to act as a secondary barrier to radionuclide migration in waste disposal. However, changes in the abiotic and biologically driven processes that occur over the long-term within the environment will alter the biogeochemistry within and around the repository. In turn, this will influence the stability of the iron oxyhydroxide minerals formed and ultimately these changes will impact on the speciation and fate of the radionuclides with the potential for re-release to occur. This experimental study will focus on characterising the fate of key risk driving radionuclides (i.e. U, Tc and Np) associated with deep geological disposal relevant iron oxyhydroxides (e.g. magnetite and goethite) during conditions relevant to the long-term biogeochemical evolution of a repository. The project will examine the influence of both abiotic and biological processes on radionuclide speciation and fate, and utilise advanced geochemical, nanoscale characterisation and microbiological genomic techniques to probe the mechanisms of radionuclide interactions.

     

    Iron (oxyhydr)oxides are ubiquitous in radioactively contaminated environments including contaminated land and radioactive waste disposal systems. In addition, they are sorbent materials utilised within the nuclear industry for clean-up of waste streams, for example in the Sellafield Enhanced Actinide Removal Plant (EARP). Within these contaminated environments, a variety of phases can form as colloids or coatings on mineral surfaces including Fe(III) (oxyhydr)oxides (e.g. goethite) within oxic environments and microbially-mediated formation of Fe(II)/Fe(III) phases (e.g. magnetite) under anoxic conditions. Iron oxyhydroxides are also predicted to form within geodisposal facilities e.g. via corrosion of steel from waste canisters / engineering forming Fe(II)/Fe(III) bearing phases including magnetite, green rust and siderite. The speciation and transport of long-lived radionuclides (e.g. U, Tc and Np) in these systems are often controlled by interaction with iron oxyhydroxide nanoparticles. In particular, surface induced reduction (e.g. forming U(IV)O2), incorporation into particles (e.g. U(V) stabilised in Fe(II)/Fe(III) phases [1] and U(VI) incorporating into hematite [1]) and biological reduction processes (e.g. forming UO2 or non crystalline U(IV) [6]) have been observed in geological disposal relevant systems. However, the biogeochemical conditions within these environmental and engineered systems will fluctuate with time including, for example, changes in oxygen levels, fluid composition and microbial nutrients / electron acceptors. These changes could alter the stability of iron oxyhydroxides phases through abiotic and biologically driven redox processes leading to transformation reactions or dissolution. In particular, both abiotic and microbially driven redox processes can facilitate the atom exchange of Fe within minerals, and electron transfer between the solution and solid mineral particles. These processes are dynamic and can lead to significant amounts (up to 100%) of Fe within the solid phase being exchanged with the solution over time scales 

  • Performance Optimisation of Next Generation Product Storage Cans ***N.B Applications are no longer being considered for this project***

    ***N.B Applications are no longer being considered for this project***

    Contact: Dr Dirk Engelberg

    This PhD project aims to better understand the corrosion behaviour of type 316L stainless steel with exposure to HCl/Chloride-bearing environments. Key aim of the project is to provide underpinning science for the safe storage of nuclear products, with the objective to optimise the engineering design of the next generation product storage cans (the “100 year can”). The project will include design and implementation of experimental protocols to control the humidity of demanding atmospheres at elevated temperature, to measure, in-situ, material degradation type and rate. The application of time-lapse 2D/3D microscopy will be explored for obtaining real time information about material life-time behaviour. The latter analysis will be augmented by state-of-the art characterisation techniques, including high-resolution electron microscopy, electron backscattered diffraction (EBSD), laser confocal microscopy, and focused ion beam techniques (FIB). The application of novel production routes to improve and optimise corrosion performance properties of the new 100-year storage can will be explored.

  • Investigation of the Chemical Degradation of Zinc Acetate under PWR Operating Conditions ***N.B Applications are no longer being considered for this project***

    Contact: Prof Simon Pimblott

     

    ***N.B Applications are no longer being considered for this project***

     

    This project offers a unique chance to work on a bespoke experimental system that simulates nuclear reactor conditions. You’ll also have the opportunity to work with world experts to develop calculations which will support this experimental work. The results of this project will be used to inform policy in relation to the safety of pressurised water reactors.

    Zinc acetate is added to reactor coolant at very low concentrations (a few ppb) as a means of reducing radiation fields when the reactor is shutdown. The interaction of this additive with spinel oxide films that form in the reactor coolant system is of particular interest as it competes with other chemical species in the coolant system and so affects the distribution of radionuclides. This can direct the radiation levels in the immediate vicinity and so is directly related to safety considerations. Although the interaction of zinc with these oxides is well studied; little is known about the in-reactor behaviour of the acetate counter-ion.

    This project will develop a better understanding of the degradation products formed, and the reaction pathways involved, when the acetate ion is decomposed due to exposure to ionising radiation and/or heat flux under PWR primary chemistry conditions. A programme of experiments and radiation-chemical diffusion-kinetic calculations will be employed to quantitatively determine the mechanism of acetate degradation by gamma and ion irradiation at room and at elevated temperature as well as the influence of metal ions and of metallic and metal oxide surfaces on the degradation.

    You’ll be based at the Dalton Cumbrian Facility which houses a one-of-a-kind gamma irradiator and a dual beam particle accelerator system with exceptional capabilities. The Facility is located in West Cumbria, just a few miles from the Sellafield site and The National Nuclear Laboratory’s Central Lab, providing outstanding access to industry experts. This location also offers easy access to the Lake District National Park and other rural attractions.

  • Modelling of Mass Transfer in Novel Solvent Extraction Systems for Nuclear Applications ***N.B Applications are no longer being considered for this project***

    Contact: Prof Andrew Masters

     

    ***N.B Applications are no longer being considered for this project***

     

    The i-SANEX process for nuclear fuel recycling including the minor actinidesis an essential part of the National Nuclear Laboratory’s national programme. The use of dynamic process models for flowsheet analysis and optimisation can greatly leverage the value of experimental work.  This project will use a combination of molecular dynamics simulation and SAFT thermodynamic theory, validated against available experimental data, to generate robust predictions on mass transfer kinetics and distribution coefficients to feed into these flow-sheets.

     

    The project methodology builds on previous experience with the PUREX process. The first step will be the construction and validation of a force-field for the species involved in i-SANEX. Once achieved, we will use this force-field to determine the equilibrium properties of the co-existing phases. Simultaneously we will develop SAFT parameters for this system, validating both against experimental data and our MD simulations, to enable the rapid determination of the phase diagram and distribution coefficients. For kinetic coefficients, we will use MD to model mass transfer through the aqueous/organic interface and use this to parameterise a robust kinetic model to feed into NNL’s flow sheet analysis. A close interaction with the flow-sheet analysts will allow the SAFT/MD modelling to focus on the aspects of the process that are most critical from an engineering point of view and thereby make rapid progress towards an overall engineering model. 

     

  • Identifying the limits and impacts of microbial metabolism in geodisposal scenarios ***N.B Applications are no longer being considered for this project***

    ***N.B Applications are no longer being considered for this project***

    Contact: Prof Jon Lloyd

    Recent research has shown that microbial metabolism is possible in a range of geological disposal scenarios, including clay barrier materials, cements and salt deposits.   When active, microorganisms are likely to have controlling influences on radionuclide biogeochemistry and mobility, which in turn may impact on the long-term performance of a geological disposal facility.  However the physical and chemical constraints on microbial life remain poorly constrained in the extreme environments associated with radioactive waste disposal.  The aim of this studentship is to use state of the art omics techniques combined with microcalorimetry and novel imaging techniques to identify the limits of life in clay barrier materials, cements and salt deposits.  The student will then determine the impact of microbial metabolism on radionuclide speciation and solubility in clay, cementitious and high salt environments.  Based in Manchester’s Research Centre for Radwaste Disposal and the Williamson Research Centre for Molecular Environmental Science, and also working closely with colleagues in the Institute of Resource Ecology (IRE) in Dresden and industry (the UK National Nuclear Lab), the student will receive an excellent training in cutting edge spectroscopy, imaging and bioscience techniques, and will be equipped for future employment in academia or the nuclear industries.

     

    For many years the extreme environments associated with nuclear waste disposal have been assumed sufficient to prevent microbial metabolism. High levels of radiation damage to microbes, in combination with the high pH (in cements), high osmotic potential (in halites) or very low porosity (in clays) were assumed to limit the activity and impact of microbes in the multibarrier systems planned for the disposal of radioactive waste into deep geological formations. For this reason, microbial metabolism has not been fully integrated into performance assessments for geological disposal facilities.

     

    The emergence of molecular-scale tools from the biological and physical sciences, including new high throughput DNA sequencing techniques, has shown that “extremophilic” microorganisms are able to survive under surprisingly inhospitable environments, including those that will be implemented during the geodisposal of radioactive waste.   For example the Manchester team have worked extensively on analogues for cementitious intermediate level waste, and have reported the metabolism of organics (including cellulose and cellulose degradation products) at high pH, which can fuel the respiration (reduction) of electron acceptors including nitrate, sulfate and priority radionuclides.  The “bioreduction” of uranium, neptunium, technetium and selenium under such conditions is of particular note, as this will result in immobilisation of these radionuclides, preventing migration into the biosphere. Similar processes are also likely in highly saline environments also under consideration for geodisposal options globally. In clay systems, where bentonites are used to prevent microbial metabolism around copper cannisters that will be used for the disposal of higher activity wastes, the inhibition of “corrosive” sulfate-reducing bacteria is paramount, and the aim here is to control swelling pressures/pore volumes of bentonites to prevent microbial activity.  However, the study of microbial metabolism in all three systems are in their infancy, and require cross-disciplinary research to identify the key parameters limiting microbial growth, and the potential impact of microbial metabolism on radionuclide speciation in these “extreme” environments.  The aim of this project is to address these limitations in our knowledge of the impact of microbial metabolism on performance assessments of geological disposal facilities. 

  • Rapid Rare Actinide Separation Chemistry: Ligand Exploitation ***N.B Applications are no longer being considered for this project***

     ***N.B Applications are no longer being considered for this project***

    Contact: Dr Sarah Heath

    Separation chemistry is essential in the forensic analysis of nuclear materials. Rapid and selective techniques allow for high confidence in the analysis obtained from the material and can allow for the quantification of radioisotopes.  Traditional separation schemes may not be suitable for all samples.  For example americium and lanthanides are usually purified towards the end of separation schemes after all other elements have been removed.  This not satisfactory for radionuclides with short half lives. These analyses allow for a dataset to be gathered which can be used to determine the origin and intended use of nuclear materials.

    Extraction chromatography has allowed the rapid separation of specific isotopes in nuclear forensics in recent times. This PhD will work to develop novel, rapid separation and preparation of samples suitable for alpha and gamma spectrometry for important radioisotopes of interest in a nuclear forensic investigation. Specifically the minor actinides Am and Cm and fission, daughter and activation products.

    The work will utilise radiochemistry techniques to design, test and then apply selective species to complex forensic matrices to develop additional rapid and selective processes, including possible incorporation into the quantification of the sample.

    Proposal

    Extraction chromatography in radiochemistry has allowed for the rapid separation of specific isotopes of interest in nuclear forensics. The design of elaborate extraction schemes to achieve difficult separations on small samples is an area of active research. Automation and vacuum flow systems are allowing for easier, rapid separations to be achieved on complex or smaller samples sizes; allowing for larger datasets to be obtained.  These datasets are essential for modelling materials in nuclear forensics.

    Schemes have been developed for a number of essential isotopes, e.g. U, Pu, Np, Sr and Cs.  Currently, specific fingerprint isotopes require laborious extraction techniques which may hinder the ability to measure them from complex matrices where a complete dataset is required.

    An example of this is Am and Cm, which in complex matrices can require long separation processes to separate them from the Lanthanide series. Many fission products can also be problematic and well as daughter and granddaughter chronometers (e.g. Cd, Pa, Th). Extractants have been developed which are highly selective for Am, Cm and fission/activation products of interest in the wider literature. These extractants will be adsorbed to polymeric matrices and developed as potential extraction chromatography resins to augment current schemes and to attempt to extract the elements on to a matrix which can be used for direct quantitative measurements.

    The potential improvements of further rapid selective schemes will allow essential data to be obtained as quickly as possible on a forensic sample. These can then be used in tandem with other available materials and automation systems. The overall rapid separation scheme will be investigated to identify improvements and develop specific targeted extractants applied to nuclear forensic matrices.

  • The role of neptunium cation-cation complexes in Np(V) disproportionation ***N.B Applications are no longer being considered for this project***

     ***N.B Applications are no longer being considered for this project***

    Contact: Prof Steve Liddle

    Neptunium is present in spent nuclear fuel but is not recovered through PUREX and instead becomes split over several reprocessing streams adding cost/complexity to plant designs. This occurs because of the rich redox chemistry of neptunium. Disproportionation of neptunium(V) to neptunium(IV/VI) is one important contributing mechanism, particularly at high acidities, and it is thought that disproportionation is promoted by cation-cation-interactions (CCIs) where neptunyl-oxo atoms act as Lewis bases to other metals; this may facilitate electron/proton transfer reactions making valency-control difficult. This is problematic because multiple interconverting species then co-exist in solution, which has major implications for routing within PUREX. Furthermore, there is significant speculation about how these processes might operate in bioreduction pathways, which demands a better understanding to help protect our environment. To further complicate matters, it has been suggested that neptunyl(V)-neptunyl(V) CCIs behave differently to uranyl(V)-uranyl(V) and plutonyl(V)-plutonyl(V) CCIs, and because all three elements are present in PUREX that neptunyl-uranyl and neptunylplutonyl CCIs may also exist. This PhD will probe this issue by: (i) preparing well-defined model homobimetallic di-neptunyl complexes based on path-finding uranyl analogues; (ii) prepare heterobimetallic neptunyl-uranyl/-plutonyl complexes; (iii) develop supporting ligands to move to those that more closely mirror real scenarios; (iv) study the mechanistic and kinetic reactivity of the CCI disproportionation reactions, thus transforming our understanding of this complex chemistry. This chemistry will provide high-impact outputs and train the student in Schlenk-line/glovebox methods and a wide range of world-leading structural, spectroscopic, and magnetic characterisation techniques at UoM (Centre for Radiochemistry Research) and NNL.

     

    Introduction: The UK Nuclear R&D roadmap describes a requirement to reprocess spent fuel if high nuclear energy scenarios are realised; to build a new reprocessing plant in a timely manner we must now make significant improvements to plant design reducing costs and waste volumes. If a fast-reactor fleet was included to close the fuel-cycle, transmute long-lived actinides, and fully exploit fissionable material then reprocessing is essential. Neptunium in spent nuclear fuel is not recovered through PUREX and like americium and curium is routed to high-level waste streams for conversion to glass and repository storage. Unlike americium and curium, however, neptunium splits over several reprocessing streams adding complexity and cost to plant design to specifically manage neptunium throughout the process. As part of the ambitious nuclear R&D national programme a flowsheet is being developed to ensure the complete recovery of neptunium in the U/Pu product. The redox chemistry of neptunium is responsible for its dispersal within PUREX because it co-exists in three oxidation states: +IV, +V, and +VI; Np(V) is not well extracted compared to Np(IV/VI). In nitric acid, radiolysis produces nitrous acid in equilibrium with NOx. Nitrous acid is an oxidising and reducing agent, leading to stabilization of Np(V) in PUREX raffinate due to Np(IV) oxidation and Np(VI) reduction through complex mechanisms. One mechanism that demands better understanding is disproportionation and the role cationcation-interactions (CCIs) play; CCIs involve actinyl-oxos bridging metal ions. There is also increasing speculation how CCIs are involved in bioreduction pathways.

  • Accurate measurement of thermal neutron cross sections to aid characterisation of nuclear waste ***N.B Applications are no longer being considered for this project***

     ***N.B Applications are no longer being considered for this project***

    Contact: Dr Gavin Smith

     

    Nuclear data, including neutron cross sections, underpin the nuclear fuel cycle, allowing calculations, predictions and analyses to be performed. These cross sections must be known to the highest possible accuracy and this is reached by performing cutting edge experiments. This PhD project focuses on neutron cross section measurements on isotopes of particular relevance to the UK nuclear industry.Neutron cross-section measurements will be performed at facilities such as the thermal high flux research reactor at ILL, Grenoble and the neutron time-of-flight facility n_TOF at CERN, Geneva. The first cross section to be measured will be 13C(n,γ), of particular importance to aid characterization of the irradiated graphite from graphite moderated reactors such as AGRs. Further isotopes requiring an improvement in their cross section accuracies have been identified such as 35Cl, 39Ar and 59Fe. As part of the PhD, future needs will be identified and measurements planned/performed.

    There will also be the opportunity to be involved in the applied nuclear physics groups research measuring nuclear fission properties with the fission fragment spectrometer, STEFF which has an on going research program at n_TOF, CERN.

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