Daniel J. Bailey

Role of Microstructure and Surface Defects on the Dissolution Kinetics of CeO2, a UO2 Fuel Analogue

The release of radionuclides from spent fuel in a geological disposal facility is controlled by the surface mediated dissolution of UO2 in groundwater. In this study we investigate the influence of reactive surface sites on the dissolution of a synthesized CeO2 analogue for UO2 fuel. Dissolution was performed on the following: CeO2 annealed at high temperature, which eliminated intrinsic surface defects (point defects and dislocations); CeO2-x annealed in inert and reducing atmospheres to induce oxygen vacancy defects and on crushed CeO2 particles of different size fractions. BET surface area measurements were used as an indicator of reactive surface site concentration. Cerium stoichiometry, determined using X-ray Photoelectron Spectroscopy (XPS) and supported by X-ray Diffraction (XRD) analysis, was used to determine oxygen vacancy concentration. Upon dissolution in nitric acid medium at 90 °C, a quantifiable relationship was established between the concentration of high energy surface sites and CeO2 dissolution rate; the greater the proportion of intrinsic defects and oxygen vacancies, the higher the dissolution rate. Dissolution of oxygen vacancy-containing CeO2-x gave rise to rates that were an order of magnitude greater than for CeO2 with fewer oxygen vacancies. While enhanced solubility of Ce(3+) influenced the dissolution, it was shown that replacement of vacancy sites by oxygen significantly affected the dissolution mechanism due to changes in the lattice volume and strain upon dissolution and concurrent grain boundary decohesion. These results highlight the significant influence of defect sites and grain boundaries on the dissolution kinetics of UO2 fuel analogues and reduce uncertainty in the long term performance of spent fuel in geological disposal.

The Environmental Paradox of the Welfare State: The Dynamics of Sustainability

Thus far, there has been a reluctance to instigate a dialogue and engage with the tensions between two literatures with significant insights for each other. The first is the literature on the fiscal sustainability of welfare states, which is invariably predicated upon future growth primarily to manage demographic changes. The second is the post-growth literature, which has enjoyed a renaissance in recent years due to an environmental critique of economic growth. Both literatures contain implications for the analysis of welfare state sustainability. The primary contribution of this paper will be to explore the intractability of the tensions between these discourses and the difficulty of mapping out a progressive policy direction in the twenty-first century which meets both our environmental and social sensibilities. It is claimed that in the post-industrial world the fiscal sustainability of welfare capitalism is dependent upon public expenditure financed indirectly an environmentally unsustainable growth dynamic, but that ironically any conflagration of public welfare programmes is likely to be counter-productive as the welfare state is able to promote de-carbonisation strategies and notions of the public good as well as promoting monetarily and ecologically efficient public welfare services.

Economic renewal through devolution? Tax reform and the uneven geographies of the economic dividend

The economic governance of the UK is currently in flux with various devolution agreements being negotiated across the country. This article examines the changing political economy of the UK enforced by Wave 1 City Deals, to analyse the claims made by devolution proponents that there is an ‘economic dividend’ to devolution. The argument is made that scant evidence exists to suggest that these reforms respond to the pathologies of the UK economy. Instead, the Northern Powerhouse discourse serves to disguise the implementation of a tax and investment settlement which regressively concentrates taxation revenue in the more affluent parts of the country. These reforms though are a political expression of a certain understanding of wealth creation which privileges low tax taxation, inter-territorial competition to promote it and a belief in the major UK cities to drive the economic recovery. It is a strategy likely to produce very uneven geographies of growth which will exacerbate uneven development; ironically so given the ‘Northern Powerhouse’ rhetoric through which it was reasoned.

Synthesis and characterisation of brannerite compositions (U0.9Ce0.1)1−xMxTi2O6 (M = Gd3+, Ca2+) for the immobilisation of MOX residues

A suite of uranium brannerites for the disposal of MOX residues, formulated (U0.9Ce0.1)1−xMxTi2O6 (M = Ca2+ and/or Gd3+), were prepared using a mixed oxide route under oxidising, inert and reducing atmospheres (air, argon and H2/N2). Gd3+ was added to act as a neutron absorber in the final Pu bearing wasteform and Ce added to function as a structural analogue for Pu. X-ray powder diffraction of the synthesised specimens found that phase distribution was strongly affected by the processing atmosphere and Gd content. In all cases prototypical brannerite was formed, accompanied by different secondary phases dependent on processing atmosphere. Microstructural analysis (SEM) of the sintered samples confirmed the results of the X-ray powder diffraction. Bulk XANES found that Ti remained in the Ti4+ oxidation state whereas Ce was uniformly reduced to the Ce3+ oxidation state regardless of processing conditions or stoichiometry. Micro-focus XANES was used to determine U oxidation in the brannerite phase and showed that U oxidised to higher U oxidation states to charge compensate. It was concluded that the charge balance mechanism was a combination of U oxidation and A-site vacancies.

The Recomposition of the Tax System: Exacerbating Uneven Development Through the Northern Powerhouse Agenda

The tax and investment reforms justified through the Northern Powerhouse discourse have set in place the foundations of a new tax settlement in England. Yet, this chapter argues that these reforms will concentrate capital available for reinvestment in those local economies which are already affluent and growing, and in all likelihood further disadvantage Northern regions. The recomposition of the tax system inaugurates a ‘race to the bottom’ between polities who will be encouraged to offer increasingly ‘business friendly’ tax environments. This is being discursively rationalised as part of a strategy to address the UK’s uneven development, but instead is likely to exacerbate regional inequalities by impeding the flow of much-needed capital for investment to the North.

On the existence of AgM9(VO4)6I (M = Ba, Pb)

The syntheses of the reported compounds AgM9(VO4)6I (M = Ba, Pb) were reinvestigated. Stoichiometric amounts of AgI with either M3(VO4)2 (M = Ba, Pb) or PbO and V2O5 were reacted in the solid-state at elevated temperatures in air or in flame-sealed quartz vessels. The resulting products were characterized by X-ray diffraction, scanning electron microscopy with energy dispersive X-ray analysis, and thermal analyses. Results show that, for all reaction conditions, the target AgM9(VO4)6I (M = Ba, Pb) phases could not be isolated. Instead, heterogeneous phase distributions of primarily M3(VO4)2 (M = Ba, Pb) and AgI were obtained. These findings demonstrate that AgI incorporation into single phase, iodine-deficient apatite derivatives for the immobilization of iodine-129 are not feasible under such conditions. This conclusion is important for the conditioning of iodine-129 in advanced reprocessing flowsheets, where iodine is typically sequestered as AgI.