No description available.

No description available.

No description available.

No description available.

This work forms part of a Collaborative Awards in Science and Engineering industrial studentship (iCASE), jointly funded by the Engineering and Physical Sciences Research Council and the National Nuclear Laboratory. The aim is to develop improved models for calculating viscosities of vitreous nuclear waste melts, particularly with respect to the variation in temperature and composition. Both in vitro and in situ experimentation on nuclear material is complicated by radioactivity and its associated expenses, so computational modelling is the principal means we use to study these industrially important glasses. The problem is approached with both top-down and bottom-up methods. From a more fundamental perspective, beginning in Section 7 Molecular Dynamics techniques are used to simulate glass melts at atomic resolution. An audit of literature forcefields, using a systematic methodology for particulate systems generation, involved calculation of structural and diffusive properties to reveal the advantages and disadvantages of contemporary sodium-borosilicate models. After developing an improved glass model, from Section 11 different methods of viscosity computation were trialled to determine that most appropriate for the conditions of the nuclear glass melters. In Section 14 the Inoue2 SBN forcefield was combined with the Green-Kubo technique, using simulated runtimes more than double those of previous literature work. The analyses produced qualitative agreement in compositional and temperature trends, as well as order-of-magnitude quantitative agreement between experimental and computational viscosity results for ternary nuclear glass frits. Complimentary top-down approaches were also used, with rotary viscometry experimentation employed in Section 4 to gather temperature-composition-viscometry data for nuclear waste glasses. These data were used with different fitting algorithms in Section 15 to compare the efficacy of theoretical descriptions for glass viscosity, described in Section 3. A combination of fitting techniques assembles in Section 17 an interpolative second-order model for which the maximum discrepancy between prediction and experiment is 17% of the absolute viscosity.

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The project focused on the hypothesis that degradable, polymer microneedle arrays are a promising alternative to traditional drug delivery routes, offering the patient a painless, high concentration, and quick delivery of therapeutics through the skin. This project explored chitosan-graphene nanocomposites as potential materials for microneedle arrays; the addition of graphene to chitosan is believed to yield improved mechanical properties and electrical conductivity over pristine chitosan, which will allow for long and slender microneedles and for electrically stimulated drug delivery, and may positively affect the degradation and drug delivery properties of chitosan. Graphene derivatives, such as graphene oxide, reduced graphene oxide, graphene quantum dots, and magnetic graphene quantum dots were synthesised and then characterised, before they were used as the filler within chitosan nanocomposites. Their effect at varying concentrations upon the mechanical properties, electrical conductivity, drug release, and enzymatic degradation rate of chitosan were assessed. It was determined that reduced graphene oxide was the optimum nanoparticle to reinforce chitosan, achieving the best mechanical and electrical conductivity properties of the nanocomposites. Chitosan-graphene nanocomposite microneedle arrays were shown to passively release small molecular weight drugs at a high delivery quantity and rate. Conductive chitosan-graphene nanocomposite microneedles were tested to determine the effect of electrical stimulation on the release of large molecular weight drugs from the nanocomposite, with substantial improvements in the release rate of large molecular weight drugs when compared to passive diffusion. The microneedle arrays were shown to survive the force of insertion through compressive loading. The depth of penetration of the microneedles was determined through cross-sectional analysis of chicken skin.

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System architecture is defined as the description of a complex system in terms of its functional requirements, physical elements and their interrelationships. Designing a complex system architecture can be a difficult task involving multi-faceted trade-off decisions. The system architecture designs often have many project-specific goals involving mix of quantitative and qualitative criteria and a large design trade space. Several tools and methods have been developed to support the system architecture design process in the last few decades. However, many conventional problem solving techniques face difficulties in dealing with complex system design problems having many goals. In this research work, an interactive multi-criteria design optimization framework is proposed for solving many-objective system architecture design problems and generating a well distributed set of Pareto optimal solutions for these problems. System architecture design using multi-criteria optimization is demonstrated using a real-world application of an aero engine health management (EHM) system. A design process is presented for the optimal deployment of the EHM system functional operations over physical architecture subsystems. The EHM system architecture design problem is formulated as a multi-criteria optimization problem. The proposed methodology successfully generates a well distributed family of Pareto optimal architecture solutions for the EHM system, which provides valuable insights into the design trade-offs. Uncertainty analysis is implemented using an efficient polynomial chaos approach and robust architecture solutions are obtained for the EHM system architecture design. Performance assessment through evaluation of benchmark test metrics demonstrates the superior performance of the proposed methodology.

The UK has large volumes of radioactive materials which are classified as Intermediate Level Waste (ILW). The baseline treatment for these wastes is encapsulation via cementation, however, this method is not ideally suited for numerous wastes, both in the UK and globally. Alternative thermal processing methods for these materials may be capable of producing wasteforms with improved properties. This thesis presents a series of scoping studies on the thermal treatment of a diverse range of ILWs in order to identify the potential benefits and pits falls of such processes. The wastes selected were Tri-Structural Isotropic (TRISO) Fuel Particles, Prototype Fast Reactor (PFR) raffinate, SIXEP sand/clinoptilolite ion exchange materials and SrTreat® Ion exchange material. The scoping studies performed showed promise for the thermal treatment of all selected waste streams. A summary of the main results for each waste stream are provided below; TRISO Fuel Particles: Immobilisation focused on encapsulation of the particles in highly durable glass matrices. Alumino-borosilicates were determined to be the most effective glass composition for the production of composites, in terms of both their physical and chemical properties. The ability of Hot Isostatic Pressing (HIPing) to improve composites was investigated. Unfortunately, this was shown to result in severe fracturing within the composite. This was hypothesised to occur as a result of excessive pressurisation during the cooling cycle. The HIP process did show some benefits in terms of particle coating properties and with small alterations to the HIP cycle utilised it should also be possible to eliminate the detrimental fracturing features. PFR Raffinate: The vitrification of PFR raffinate was investigated using the G73 glass composition, a glass which has been previously proposed for the immobilisation of other ILWs. This glass was proven to be capable of accommodating a waste loading of up to 20 wt% PFR raffinate. The glass produced was homogeneous with good waste retention, had no noted crystal formation, an aqueous durability comparable to currently employed HLW glasses and the thermal characteristics necessary for industrial scale up. Further study should be performed on the ability of this waste to retain Cs during processing and in aqueous solution. SIXEP Sand/Clinoptilolite Waste: SIXEP sand/clinoptilolite was processed at 95 wt% with a 50 % volume reduction by HIPing. The waste produced was a phase separated glass-ceramic. The wasteform was deemed to be suitable for ILW immobilisation and had an exceptional Cs ii retention in aqueous solutions. However, the presence of an alkali earth sulphate phase increased the Sr release to solution. Attempts to qualify the suitability of this wasteform for disposal, developed methodologies to investigate the properties of phase separated materials. A combination of vertical scanning interferometry (VSI), dissolution experiments and SEM imaging was shown to be capable of elucidating the dissolution behaviour based upon compositional variation. SrTreat®: SrTreat® was processed at 100% waste loading via HIPing. This aim was to investigate the potential for developing ion exchange columns which could subsequently be HIPed, as such, providing a complete waste treatment solution. The HIP process produced a monolithic, mixed phase sodium titanate ceramic. This ceramic was formed by the sintering of individual grain structures and retained the compositional variations seen in the granular waste stream. The wasteform was porous around the grain edges, determined to occur as a result of carbonate formation prior to HIPing. The carbonation of this material is likely to limit the potential to utilise HIPing as a disposal methodology for these wastes. However the aqueous dissolution behaviour of these wastes was still favourable and the process was shown to create a significant reduction in waste volume. The work performed in this thesis has shown that various methods for thermal treatment can be rapidly investigated to determine the potential benefits and pit falls. The application of thermal treatments was shown to be capable of producing significant improvements in wasteform quality by comparison with the cementitious alternatives.