Proving the process of spent fuel drying

PGR-P-1611

Key facts

Type of research degree: 4 year PhD
Application deadline: Friday 28 April 2023
Project start date: Monday 18 September 2023
Country eligibility: UK only
Funding: Funded
Source of funding: Centre for doctoral training
Supervisors: Professor Bruce Hanson and Dr Ana Heitor
Schools: School of Chemical and Process Engineering

<h2 class="heading hide-accessible">Summary</h2>

This project supports the future stewardship for spent AGR fuel. The NDA strategy is to consolidate all spent AGR fuel in a single pond at the THORP facility at the Sellafield site for interim storage, pending a future decision on their disposition route. Whilst the primary plan is for long term wet storage, should issues arise it is recognised that fuel may need to be dried and dry stored. Leeds have been leading academic research in the UK into the drying of SNF, starting in 2013 a series of three PhD projects have been run investigating drying of AGR and Magnox fuels. So far, investigations proven drying conditions and looked at whether water can be removed through cracks in the cladding. This project is intended to build upon work carried out in earlier PhD’s carried out by Leeds and to make use of data use collected as part of other NDA funded projects The aim of this project will be to bridge this gap by developing a full sized mock fuel pin which can potentially be manufactured in bulk for use in future drying trials, by creating a “pin” that is suitable for large scale drying experiments.

<h2 class="heading hide-accessible">Full description</h2>

This project helps underpin the future stewardship for spent AGR fuel and so fits into the Spent Fuel and Nuclear Materials theme. It supports all four of the themes presented in the Bursary call by: <ol> <li>Maintain and develop the key technical skills that will be required to help us carry out the mission over the coming decades. The project is a continuation of a series of PhDs projects that have been building up a UK skill base in fuel drying.</li> <li>Provide fundamental understanding of technologies and processes across the NDA estate. The project will provide a deep technical understanding of the drying process, built on fundamental research.</li> <li>Develop early stage technologies (TRL 1 – 3). Experimental rigs will be created that can be used to test specific aspects of the fuel drying process.</li> <li>Encourage two-way knowledge transfer between the academic and industrial communities working on nuclear decommissioning. The project will create a close collaborative link with UK NNL, who are developing full scale and fully active drying rigs.</li> </ol> The strategic need for this type of research can be drawn from the NDA R&D strategy document, which states that: “Our strategy is to consolidate all spent AGR fuel from the EDF AGR stations in a single pond in the THORP facility at the Sellafield site, and interim store all oxide fuels (SO9) pending a future decision on whether to classify the fuel as waste for disposal in a GDF (SO10).” Whilst the primary plan is for long term wet storage, should issues arise it is recognised that fuel may need to be dried and dry stored. In addition, at the point of disposal, fuel will also need to be dried prior to packaging. Hence the NDA has identified fuel drying in the scope of its Lot 4 R&D framework; i.e. to: <ul> <li>understand fuel drying characteristics and process options, including potential technical basis for dry storage of AGR, typically drying process options and achievable dryness levels</li> <li>understand fuel behaviour in dry storage environments and options for short or extended dry storage period</li> </ul> UoL have been leading academic research in the UK into the drying of SNF.  UoL and EPRSC funded an initial PhD in 2013 which carried out early investigations into drying methods however this work was limited to using pin-holed samples.  A follow up PhD is ongoing and has been looking at whether water can be removed SCC cracks through a combination of experiment and modelling but has not been able to put cracks into long lengths of tubing.  In the meantime, a further Leeds PhD has investigated the related area of Magnox drying. The project is intended to build upon work carried out in earlier PhD’s carried out by Leeds and to make use of data use to be collected as part of other NDA funded projects Whether it be for pre-treatment prior to disposal or long-term storage, drying of AGR (and potentially other fuels) will be required at some point. Building a drying facility will be a significant investment and is likely to cost tens if not hundreds of millions of pounds. Prior to committing to detailed design of such a facility, we will want to be confident it will work with all AGR fuel, so there will be a need to demonstrate the functionality of a drying process. A small-scale rig with the potential to dry up to ~30 pins is under construction but before investing in a final plant further testing will be required on at least the slotted can scale. There are only (estimated) 50 real failed pins known to be in existence and these are destined to be dried as part of an upcoming NDA project. While we can deliberately fail pins should there be a need that would be a less than ideal solution. It also wouldn’t take into account of long-term storage which is likely to be required if pins are to become flooded. Even if we did have real pins, the costs of doing such work with irradiated fuel pins would be substantial and would likely put severe limitations on the amount of testing that would be possible. Furthermore, the scale might be limited to what can fit in available cave space which on some current estimates may be severely limited. Since radioactivity is not a major factor in how pins would dry it would be preferable to carry out this work with a non-active demonstration rig.  This would be significantly quicker and cheaper to design build and operate and allow for a more substantial range of testing which would provide greater confidence in its performance.  However, in order to carry out such tests it is necessary to have a simulant pin which behaves in a suitably representative manner.  At this time, such a pin does not exist with all tests carried out to date and expected in the future relying on simplified defects which are unlikely to have the appropriate behaviour. The aim of this project will be to bridge this gap by developing a full-sized mock fuel pin which can potentially be manufactured in bulk for use in future drying trials. The project will create a “pin” that was suitable for large scale drying experiments. The key aspects would be to develop something that behaved in a suitable manner i.e. it does not have to be a perfect replica it just has to have the right characteristics. For example, we can’t reliably crack 20/25 but we can crack 304 so we could use that.  Other aspects that will be important are: <ul> <li>defect permeability.</li> <li>matching thermal properties and behaviour;</li> <li>surrogate fuel pellets;</li> <li>replicating decay heat;</li> <li>cladding condition other than cracking, e.g. carbon deposits</li> </ul> The PhD builds on the experience and skills gained from the previous projects. Firstly, the project would start off looking at how to put defects in full size pins (the basic process is currently being proven in trials @ Leeds) and could then move onto the other factors. The project will be work closely with UK NNL, who are building an active fuel drying rig. Rig design experience and experimental data will be shared both ways to ensure consistency and the Student will have 1-week secondments built into the project in years 1, 2 and 3 to have the opportunity to get closer to the active work.  The project will ultimately look to test the simulant pin using the drying rigs being built by SL/NDA and compare the drying behaviour to that of real pins which is due to be collected for the NDA shortly after this PhD begins. Output from the project will be: <ol> <li>A proven design for a surrogate fuel pin;</li> <li>A revised fuel drying rig suitable for further experiments to support scale-up;</li> <li>Experimental data to underpin process design;</li> <li>A subject matter expert that could be employed for future fuel drying project</li> </ol> <a href="https://www.nuclear-energy-cdt.manchester.ac.uk/">Centre for Doctoral Training in Nuclear Energy – GREEN</a>

<h2 class="heading">How to apply</h2>

Formal applications for research degree study should be made online through the <a href="https://www.leeds.ac.uk/research-applying/doc/applying-research-degrees">University's website</a>. Please state clearly in the Planned Course of Study section that you are applying for EPSRC CDT Nuclear Energy-GREEN and in the research information section that the research degree you wish to be considered for is Proving the process of spent fuel drying as well as <a href="https://eps.leeds.ac.uk/chemical-engineering/staff/522/professor-bruce-hanson">Professor Bruce Hanson</a> as your proposed supervisor. If English is not your first language, you must provide evidence that you meet the University's minimum English language requirements (below). 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. Applications will be considered on an ongoing basis.  Potential applicants are strongly encouraged to contact the supervisors for an informal discussion before making a formal application.  We also advise that you apply at the earliest opportunity as the application and selection process may close early, should we receive a sufficient number of applications or that a suitable candidate is appointed. Please note that you must provide the following documents in support of your application by the closing date of 28 April 2023: <ul> <li>Full Transcripts of all degree study or if in final year of study, full transcripts to date</li> <li>Personal Statement outlining your interest in the project</li> <li>CV</li> <li>Funding information:  EPSRC CDT Nuclear Energy – GREEN</li> </ul>

<h2 class="heading heading--sm">Entry requirements</h2>

Applicants to research degree programmes should normally have at least a first class or an upper second class British Bachelors Honours degree (or equivalent) in an appropriate discipline. The criteria for entry for some research degrees may be higher, for example, several faculties, also require a Masters degree. Applicants are advised to check with the relevant School prior to making an application. Applicants who are uncertain about the requirements for a particular research degree are advised to contact the School or Graduate School prior to making an application.

<h2 class="heading heading--sm">English language requirements</h2>

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.

<h2 class="heading">Funding on offer</h2>

A highly competitive EPSRC Centre for Doctoral Training in GREEN studentship, consisting of the award of fees with a maintenance grant (currently £17,668 in academic session 2022/23) for 4 years. This opportunity is open to UK applicants only.  All candidates will be placed into the EPSRC Centre for Doctoral Training in GREEN Studentship Competition and selection is based on academic merit. Please refer to the <a href="https://www.ukcisa.org.uk/">UKCISA</a> website for information regarding Fee Status for Non-UK Nationals.

<h2 class="heading">Contact details</h2>

For further information about this project, please contact Professor Bruce Hanson (Programme Director): e: <a href="mailto:b.c.hanson@leeds.ac.uk">b.c.hanson@leeds.ac.uk</a>, t: +44 (0)113 343 0475 For further information about your applicationt, please contact Doctoral College Admissions: e: <a href="mailto:phd@engineering.leeds.ac.uk">phd@engineering.leeds.ac.uk</a>