Simulation of particle agglomeration, attrition and breakup for nuclear waste transport and retrieval processes

The safe retrieval, transport and processing of radioactive waste slurries is one of the most significant engineering challenges in nuclear decommissioning. These operations involve complex turbulent flows carrying heterogeneous suspensions of particles with varied sizes, shapes and material properties. A critical but poorly understood feature of such flows is that particle size distributions are not stationary. Particles can agglomerate through cohesive interactions, fragment under hydrodynamic stress, or gradually wear down through repeated collisions with other particles and surfaces (attrition). These changes in particle size distributions directly affect settling behaviour, rheology, pipeline transport characteristics, blockage risk and the efficiency of downstream treatment operations. Despite the importance of these processes, existing models for nuclear waste transport typically assume fixed or overly simplified particle populations, leaving a significant gap in predictive capability.<br /> <br /> This PhD will address that gap by developing a novel multi-scale fluid dynamics simulation framework that connects the physics of individual particle collisions to bulk-scale turbulent transport predictions. The novelty of the work lies in bridging the gap between particle-resolved contact and failure mechanics with Lagrangian particle tracking of millions of individual particles in turbulent flows, facilitated using state-of-the-art machine learning techniques.<br />

<p style="margin-bottom:11px">The project will begin with a literature review to identify the governing mechanisms and key dimensionless parameters controlling agglomeration, flocculation, breakup and attrition in particle-laden flows relevant to nuclear waste processing. Building on this, Lagrangian particle tracking simulations will be used to study how particles of different sizes and shapes collide and aggregate under varying flow conditions, with particular attention to the role of local shear and particle morphology in determining aggregation likelihood. The development stage of the project involves particle-resolved simulations in which particles are modelled as assemblies of bonded subparticles. This approach enables realistic simulation of fracture, chipping and surface attrition at the individual particle level, going substantially beyond what is achievable with conventional point-particle methods. Systematic studies will vary collision velocity, angle, particle shape and material properties to build a comprehensive dataset of breakup and damage outcomes. The resulting data will be used to train machine-learning models capable of predicting collision outcomes at a fraction of the computational cost of fully resolved simulations. These reduced-order models will then be embedded within large-scale Lagrangian simulations of turbulent wall-bounded flows, enabling particle size distribution evolution to be tracked through representative transport configurations. The project will culminate in the construction of regime maps identifying the flow regions and operating conditions under which agglomeration, breakup and attrition are expected to dominate, expressed in terms of governing non-dimensional parameters such as particle Stokes number, fluid stress and morphology descriptors. These maps will be interpreted in the context of practical nuclear waste retrieval and processing scenarios, providing guidance on operating conditions that minimise fines generation or reduce blockage risk. The outcomes will be a validated predictive simulation tool with direct relevance to decommissioning and waste management, together with fundamental new understanding of how particle-scale collision mechanics influence bulk transport behaviour in turbulent flows.</p> <p><strong>CDT information</strong></p> <p>This project is part of the Centre for Doctoral Training (CDT) in SATURN (Skills And Training Underpinning a Renaissance in Nuclear). It is led from the University of Manchester and includes leading nuclear research universities in the North of England and Scotland (University of Leeds, University of Sheffield, Lancaster University, University of Liverpool, University of Strathclyde). We aim to deliver the next generation of nuclear researchers to help the UK achieve its Net Zero targets and beyond, in a collegial cohort environment. The CDT will also include technical training in the nuclear fuel cycle to ensure all candidates are familiar with the nuclear sector, and specialist research skills training.</p> <p><a href="http://www.saturn-nuclear-cdt.manchester.ac.uk/">SATURN_Nuclear_CDT</a></p>

<p>To apply for this project you will need to make a formal application for research degree study through the <a href="https://www.leeds.ac.uk/research-applying/doc/applying-research-degrees">University website</a>. You will need to create a login ID with a username and PIN.</p> <ul> <li>For <strong>Application type</strong> please select <strong>Research Degrees, Research Postgraduate</strong>.</li> <li>The admission year for this project is <strong>2026/27 Academic Year</strong>.</li> <li>You will need to select your <strong>Planned Course of Study</strong> from a drop-down menu. For this project, scroll down and select <strong>EPSRC CDT SATURN – Nuclear Science and Engineering</strong>.</li> <li>The project start date for this project is <strong>1 October 2026</strong>, please use this as your <strong>Proposed Start Date of Research</strong>.</li> <li>Please state clearly in the research information section that the research degree you wish to be considered for is<strong> Simulation of particle agglomeration, attrition and breakup for nuclear waste transport and retrieval processes </strong>as well as <a href="https://eps.leeds.ac.uk/chemical-engineering/staff/177/professor-michael-fairweather">Professor Michael Fairweather</a> as your proposed supervisor.</li> <li>Please state clearly that the funding you are applying for is <strong>EPSRC CDT SATURN</strong>.</li> </ul> <p>More information on how to apply is available on our website <a href="https://www.leeds.ac.uk/research-applying/doc/applying-research-degrees">here</a>. You will be required to provide a personal statement which outlines your interest in the project you are applying for, why you have chosen it and how your skills map onto the requirements of the project.</p> <p>Applications will be reviewed and assessed after the closing date of Tuesday 30 June 2026.  We welcome and strongly encourage any potential applicants to contact the supervisor(s) or the CDT SATURN Programme Team for an informal discussion, prior to applying, and recommend submitting your application early.</p> <p><strong>Please note that you must provide the following documents in support of your application by the closing date of Tuesday 30 June 2026:</strong></p> <ul> <li>Full Transcripts of all degree study or if in final year of study, full transcripts to date including grading scheme</li> <li>Personal Statement outlining your interest in the project</li> <li>CV</li> </ul> <p>If English is not your first language, you must provide evidence that you meet the University's minimum English language requirements (below).</p> <p><em>As an international research-intensive university, we welcome students from all walks of life and from across the world. We foster an inclusive environment where all can flourish and prosper, and we are proud of our strong commitment to student education. Across all Faculties we are dedicated to diversifying our community and we welcome the unique contributions that individuals can bring, and particularly encourage applications from, but not limited to Black, Asian, people who belong to a minority ethnic community, people who identify as LGBT+ and people with disabilities. Applicants will always be selected based on merit and ability.</em></p>

Candidates will have, or be due to obtain, a Master’s Degree or equivalent from a reputable university in an appropriate field of Engineering. Exceptional candidates with a First Class Bachelor’s Degree in an appropriate field will also be considered. Applicants are advised to check with the relevant School prior to making an application.

The minimum English language entry requirement for research postgraduate research study is an IELTS of 6.0 overall with at least 5.5 in each component (reading, writing, listening and speaking) or equivalent. The test must be dated within two years of the start date of the course in order to be valid. Some schools and faculties have a higher requirement.

<p style="text-align:start; margin-bottom:24px">A highly competitive EPSRC Centre for Doctoral Training in Skills And Training Underpinning a Renaissance in Nuclear (SATURN) studentship in partnership with Sellafield Ltd, offering the award of full academic fees, together with a tax-free UKRI enhanced maintenance grant of £26,000 per year for 4 years.  Additional training and support will also be provided.<br /> <br /> This opportunity is open to UK applicants only. All candidates will be placed into the EPSRC Centre for Doctoral Training in SATURN Studentship Competition and selection is based on academic merit.<br /> <br /> Please refer to the <a href="https://www.ukcisa.org.uk/">UKCISA</a> website for information regarding Fee Status for Non-UK Nationals.</p> <p><strong>Eligibility Criteria</strong></p> <ul> <li>Applicants must be eligible to pay fees at the Home (UK) rate.</li> </ul> <p>If you are unsure whether you are eligible for UK fees/funding, please see our <a href="https://www.leeds.ac.uk/undergraduate-fees/doc/fee-assessment">fee assessment page</a>.</p> <p><strong>Other Conditions</strong></p> <ul> <li>Candidates who have previously been awarded a PhD or are currently registered on a PhD are excluded from applying. Those who were previously studying for a PhD but did not complete may be considered. </li> <li>Awards must be taken up by 1 October 2026.</li> <li>Applicants must live within a reasonable distance of the University of Leeds whilst in receipt of this scholarship.</li> </ul>

<p>For further information about this project, please contact Professor Michael Fairweather by email to <a href="mailto:M.Fairweather@leeds.ac.uk">M.Fairweather@leeds.ac.uk</a></p> <p>For further information about your application, please contact the PGR Admissions Team by email to <a href="mailto:phd@engineering.leeds.ac.uk">phd@engineering.leeds.ac.uk</a></p> <p>For further information about the CDT SATURN programme, please contact the CDT SATURN Programme Team by email to <a href="mailto:saturn@manchester.ac.uk">saturn@manchester.ac.uk</a> or Dr Timothy Hunter (Programme Director) by email to <a href="mailto:t.n.hunter@leeds.ac.uk">t.n.hunter@leeds.ac.uk</a>. Please include the specific title of the project and list University of Leeds as the project university.</p>