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What do we do with left over Magnox: optimisation of a direct encapsulation process for the treatment of Magnox fuel and wastes

PGR-P-773

Key facts

Type of research degree
4 year PhD
Application deadline
Saturday 18 July 2020
Project start date
Monday 14 September 2020
Country eligibility
UK and EU
Funding
Funded
Source of funding
Centre for doctoral training
Supervisors
Professor Bruce Hanson and Dr Bhoopesh Mishra
Schools
School of Chemical and Process Engineering
Research groups/institutes
Complex Systems and Processes
<h2 class="heading hide-accessible">Summary</h2>

It is possible that a small quantity of Magnox fuel may not be reprocessed. Experience from the First Generation Fuel Storage ponds at Sellafield site shows us that wet storage of Magnox fuels leads to extensive corrosion of the cladding and partial corrosion of the uranium metal. The main strategy of Magnox fuel storage has been to prevent or inhibit this corrosion, so that the fuel cladding integrity is maintained. In the legacy ponds and silos, corrosion of 1st generation Magnox fuel has occurred and in some cases to completion, but this has led to a problem, as the fuel was intended for retrieval. If this had occurred in an engineered container that was compatible with in-drum cementation, then it could have been directly converted to a waste This project will develop a process to convert Magnox and Exotics fuels into a chemically passive solid waste form, suitable for disposal. It builds the previous work and aims to define the mechanism that drives the Mg-water-chloride reaction, to sufficient detail so as to be able to confidently predict the extend of reaction in the condition prevailing on the plant. The project will also define the optimum conditions that will result in a robust Mg cement, in order to provide a good quality final waste form.

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

<p paraeid="{3ceaa8a2-14e6-4554-a2a5-7a94ce445e3e}{251}" paraid="726966462">It is possible that a small quantity of Magnox fuel may not be reprocessed. Experience from the First Generation Fuel Storage ponds at Sellafield site shows us that wet storage of Magnox fuels leads to extensive corrosion of the cladding and partial corrosion of the uranium metal. The main strategy of Magnox fuel storage has been to prevent or inhibit this corrosion, so that the fuel cladding integrity is maintained. However, Magnox cladding is chemically reactive and when immersed in water for long periods will react to form hydroxides of magnesium and aluminium, with a release of hydrogen gas.&nbsp;</p> <p paraeid="{88e98f74-b350-474c-ad96-011245de1cdb}{2}" paraid="860293810">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;Mg+2H2O&nbsp;&rarr;Mg(OH)2+&nbsp;H2</p> <p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;Al+6H2O&nbsp;&rarr;2Al(OH)3+&nbsp;3H2</p> <p>In addition to the reactivity of the cladding, the uranium metal fuel is also reactive.&nbsp;</p> <p paraeid="{88e98f74-b350-474c-ad96-011245de1cdb}{20}" paraid="1675949731">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;U+0.5(2+x)H2O&nbsp;&rarr;UO(2+x)</p> <p>Under anaerobic conditions hydrogen can be generated.&nbsp;</p> <p paraeid="{88e98f74-b350-474c-ad96-011245de1cdb}{31}" paraid="78726858">In the legacy ponds and silos, corrosion of 1st&nbsp;generation Magnox fuel has occurred and in some cases to completion, whilst in others only partially complete. In this instance the situation and location has led to a problem, as the fuel was intended for retrieval; but if this had occurred in an engineered container that was compatible with in-drum cementation, then it could have been directly converted to a waste.&nbsp;</p> <p paraeid="{88e98f74-b350-474c-ad96-011245de1cdb}{45}" paraid="722009150">In CAPE, a PhD project funded by the NDA and associated with NGN, has been ongoing that will&nbsp;develop a process to convert Magnox and Exotics fuels into a chemically passive solid waste form, suitable for disposal.&nbsp;The main question that this project will address is whether Magnox fuel can be completely converted to Mg/Al/U oxides or hydroxide slurry, in benign conditions, to create a chemical form that is&nbsp;compatible with&nbsp;packaging or encapsulation.&nbsp;</p> <p paraeid="{88e98f74-b350-474c-ad96-011245de1cdb}{67}" paraid="1105271854">The project is near completion and the concept of complete conversion from Mg metal to&nbsp;Mg&nbsp;based cement has been proven. Further work with real samples of corroded Magnox cladding is left to do.&nbsp;</p> <p paraeid="{88e98f74-b350-474c-ad96-011245de1cdb}{81}" paraid="575545941">However, significant unknowns remain in the kinetics of the Mg-water-chloride reaction, as&nbsp;the&nbsp;underlying knowledge&nbsp;base is not clear on the actual reaction mechanism.&nbsp;</p> <p paraeid="{88e98f74-b350-474c-ad96-011245de1cdb}{81}" paraid="575545941">Further information can be found on the <a href="https://www.nuclear-energy-cdt.manchester.ac.uk/">Centre for Doctoral Training Nuclear Energy</a> website.</p> <p paraeid="{88e98f74-b350-474c-ad96-011245de1cdb}{99}" paraid="685949823">&nbsp;</p> <p paraeid="{88e98f74-b350-474c-ad96-011245de1cdb}{103}" paraid="1474096213">&nbsp;</p>

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

<p>Formal applications for research degree study should be made online through the&nbsp;<a href="http://www.leeds.ac.uk/rsa/prospective_students/apply/I_want_to_apply.html">University&#39;s website</a>. Please state clearly in the research information section&nbsp;that the research degree you wish to be considered for is &lsquo;What do we do with left over Magnox: optimisation of a direct encapsulation process for the treatment of Magnox fuel and wastes&rsquo;&nbsp;as well as&nbsp;<a href="https://eps.leeds.ac.uk/chemical-engineering/staff/522/professor-bruce-hanson">Professor Bruce Hanson</a>&nbsp;as your proposed supervisor.</p> <p>If English is not your first language, you must provide evidence that you meet the University&#39;s minimum English language requirements (below).</p> <p><em>We welcome applications from all suitably-qualified candidates, but UK black and minority ethnic (BME) researchers are currently under-represented in our Postgraduate Research community, and we would therefore particularly encourage applications from UK BME candidates. All scholarships will be awarded on the basis of merit.</em></p>

<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>

<p>EPSRC Centre for Doctoral Training Studentship for 4&nbsp;years consisting of academic fees (&pound;4,600 for 2020/21), together with a maintenance grant (&pound;15,285 for 2020/21) paid at standard Research Council rates. It is part funded by Sellafield Ltd. UK applicants will be eligible for a full award paying tuition fees and maintenance.&nbsp; European Union applicants will be eligible for an award paying tuition fees only, except in exceptional circumstances, or where residency has been established for more than 3 years prior to the start of the course. Funding is awarded on a competitive basis.</p>

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

<p>For further information regarding your application,&nbsp;please contact Doctoral College Admissions<br /> e:&nbsp;<a href="mailto:phd@engineering.leeds.ac.uk">phd@engineering.leeds.ac.uk</a>, t: +44 (0)113 343 5057.</p> <p>For further information regarding the project, please contact Professor Bruce Hanson:&nbsp;&nbsp;<a href="mailto:B.C.Hanson@leeds.ac.uk">B.C.Hanson@leeds.ac.uk</a></p>


<h3 class="heading heading--sm">Linked research areas</h3>