May 11, 2021

Building the foundations of a predictive tool for spent fuel behaviour (PhD)

The overall aim of the PhD project and associated PDRA position is to construct the basis for a predictive tool for spent fuel behaviour; to model spent fuel in aqueous environments, across length-scales, using results from atomistic simulations, using physical and chemical kinetics, combining radiolysis models with molecular dynamics. We plan to close the loop […]

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May 11, 2021

Electrokinetic remediation application to soils, concretes and other site and process wastes (including EDTA-containing wastes)

Despite a range of existing soil and water remediation, and waste clean-up, techniques available to nuclear site managers, effective in-situ and ex-situ remediation remain a common technical challenge, particularly at sites with complex or low permeability soils / subsurface geology, and on working sites or sites with considerable surface and subsurface infrastructure. This research builds […]

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May 11, 2021

Atomistic simulation of Am incorporation into PuO2

The UK currently holds the world’s largest stockpile of plutonium. For storage the Pu was converted into PuO2 and sealed in inert steel canisters under argon. Since sealing, some canisters exhibit signs of becoming pressurised raising concerns over their viability over anticipated lifetimes. A possible explanation for this pressurisation is the evolution of hydrogen gas […]

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May 11, 2021

Computational Modelling of PuO2: Ageing and Storage Phenomena

Until the UK Government arrives at a decision regarding the final treatment and disposition of Pu, the NDA remain responsible for the “safe and secure storage”. However, ageing mechanisms associated with the storage of PuO2 are poorly understood. The generation, stability and mobility of fission products in addition to the role of the surface oxide […]

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May 11, 2021

Quantum chemical modelling of PuO2 surface chemistry

Quantum chemical calculations (DFT), in both the embedded cluster and periodic boundary condition (PBC) framework, will be employed to study: Non‑ and dissociative adsorption of water on stoichiometric and substoichiometric ThO2 surfaces – comparison with our previous work on water adsorption on other AnO2 (An = U-Cm). Evaluation of the effects of the size of […]

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May 11, 2021

The Recombination of Hydrogen and Oxygen on Metal Oxide Surfaces

Approximately 125 tonnes of separated Pu is in long term storage at Sellafield as calcined PuO2 powder in nested, sealed steel storage cans. Under certain circumstances, gas generation may occur with consequent storage package pressurisation. In practice, this is rarely seen and empirically derived criteria are used to account for the release of known gases […]

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May 11, 2021

Gas generation from the radiolysis of water on uranium oxides and ThO2

This PhD will involve measuring the radiolytic hydrogen yield from water adsorbed surrogate materials for PuO2 and plutonium-uranium mixed oxides. Measurements will be made under gamma and helium ion irradiation. The effect of irradiation on the oxide surface will be characterised.   Powders of UO2, U3O8, UO3 and ThO2 oxides, and possibly (U,Th)O2 will be […]

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May 11, 2021

The Surface Chemistry of Plutonium Dioxide under Conditions Relevant to Interim Storage

Approximately 125 tonnes of separated Pu is in long term storage at Sellafield as calcined PuO2 powder in nested, sealed steel storage cans. Under certain circumstances, gas generation may occur with consequent storage package pressurisation. In practice, this is rarely seen and empirically derived criteria are used to ensure safe storage conditions remain and account […]

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May 11, 2021

Disposability of wasteforms for plutonium immobilisation and efficacy of surrogates

This project aims to reduce the key uncertainties pertaining to zirconolite ceramic/glass-ceramic waste form dissolution. The key objectives are to: Understand the effects of relevant geochemical parameters on the kinetics of HIP-ed ceramic/glass-ceramic zirconolite materials, using Ce and U as surrogates for Pu; Develop an understanding of the dissolution mechanisms of HIP-ed ceramic/glass-ceramic zirconolite materials; […]

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May 11, 2021

Plutonium immobilisation

Key outcomes are to underpin and enable immobilization of the plutonium stockpile through: Pu partitioning data, and verified computational models, to guide wasteform design; and new understanding of mechanisms of crystalline to amorphous phase transition in ceramic wasteforms and its potential deleterious effect on dissolution kinetics. Impact will arise through uptake of research by NDA, […]

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