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Modelling the Defect Chemistry of Actinide Oxide Nuclear Fuels

   Department of Chemical Sciences

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  Dr M Molinari  No more applications being accepted  Competition Funded PhD Project (UK Students Only)

Huddersfield United Kingdom Ceramics Computational Chemistry Computational Physics Nuclear Physics Materials Science Physical Chemistry Quantum Mechanics Solid State Physics Thermodynamics

About the Project

Since oxidation affects materials stability and lifetimes, comprehensive models of defect formation and oxidative processes are needed for the safe use, storage and disposal of nuclear fuels based on actinide oxides. These fuels display complex chemical properties inherently linked to the oxygen stoichiometry and the multivalent oxidation state of the actinide elements. In this project, molecular modelling is employed to unravel the structural deviations at the nanoscale, and their impact on the oxidation behaviour, vital for the safe manipulation of the fuels in the nuclear fuel cycle.

As fossil fuels are increasingly being phased out to limit global warming, nuclear power plays an increasing crucial role in meeting green and sustainable energy generation and demand. Within the nuclear cycle, the use, storage and disposal of nuclear fuels represents major challenges. This is because very little is known about the defect chemistry and physical properties of the constituent actinide oxides. Uranium oxide is currently the most widely-used nuclear fuel, mixed uranium-plutonium oxide fuels are explored as next-generation fuels, and minor actinides americium and neptunium oxides are found in notable amounts in spent nuclear fuels. In solid solution of actinide oxides, there is a strong correlation between the oxidation state of the cations and the oxygen stoichiometry, which governs the oxygen/metal ratio. For example, uranium oxide can uptake a large concentration of excess oxygen while preserving the fluorite structure; there are at least fourteen known fluorite-based structures, with uranium displaying oxidation states ranging from tetravalent to hexavalent. Changes in the oxygen/metal ratio have dramatic effects on the thermal properties of the fuels, which determine their behaviour in reactors. Such complex chemical landscape is exacerbated at the surfaces and grain boundaries of the polycrystalline fuel samples, particularly as defects are known to segregate at such interfaces. Comprehensive models to describe and correlate the oxygen/metal ratio, the defect chemistry and the defect formation pathways in actinide oxides are the first necessary steps for understanding the oxide fuels behaviour.

Computational modelling in conjunction with modern high-performance computing can help meet these research challenges. In this project, we propose to use molecular modelling to unravel the impact of defects in actinide oxides on their structural dynamics. We will develop knowledge to quantify the impact of defects on the structural dynamics and dependent physical properties, to determine the impact of lattice vibrations on the defect formation and energetics, to define key spectral signatures that may lead to identify such defects in experimental material samples, and to take the first step towards examining their impact on thermal transport. The candidate will work in the Computational Materials and Minerals Group under the supervision of Dr Marco Molinari. Please contact [Email Address Removed] for any further information.

The application must be done via the University website. Application details at

Funding Notes

3 years full time research covering tuition fees and a tax free bursary (stipend) starting at £15,609 for 2021/22 and increasing in line with the EPSRC guidelines for the subsequent years. Funded via the Engineering and Physical Sciences Research Council Doctoral Training Programme at the University of Huddersfield. UK applicants only.
First Class or Upper Second Class Honours degree required. The candidate must hold a Bachelor’s or Master’s degree in Materials Science, Physics, Chemistry, Nuclear Engineering, or related discipline.
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