The EFDA-JET tokamak is an experimental fusion device researching fusion as a means of energy production. Inside the toroidal vessel, plasma with temperature in excess of 100 million degrees Celsius is generated and constrained by high power magnetic fields. Additional protection is provided by tiles which clad the inside of the machine. As part of a major upgrade existing heat protective tiles are to be replaced with an advanced design, and renewed interest has been shown in dimensional measurement of the surface. Measurement must occur during shutdown periods where temperature and pressure are at ambient levels. Manned entry is not permissible and all work should be performed remotely. To avoid contamination which could affect the fusion reaction and experimental results, contact with the measurement surface is not permitted. This work assesses non-contact surface measurement technologies, along with standards and guidelines for dimensional surface measurement. Existing measurement test artefacts do not offer the required surface finish and features, so specific test artefacts have been designed and produced. These artefacts are traceable to the national length standard, as traceability is a pre-requisite to evaluate accuracy. Exploratory tests highlighted two technologies for further investigation, laser triangulation and white light fringe projection. Two commercially available, state-ofthe- art examples of each technology have been evaluated using a processing method developed to highlight performance in key areas relevant to EFDA-JET. These areas include quantitative assessments of the effect of surface angle on measurement quality, the effect of depth of field for fringe projection systems and the ability of technologies to record gap and flush from tens of micrometres to millimetres. Tests enable a user to begin to assess the impact the measurement system has on the measurement result, how different technologies and systems used alone or in combination may resolve or compound erroneous results, clarifying or disrupting the meaning of results.

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No description available.

The ambitious 16+ GW new nuclear programme in Britain marks a distinctive low-carbon energy pathway. The proposed new build projects are megainvestments instituting novel ways of governance and public engagement with striking contrasts to previous constructions. To probe into this new era of nuclear megainvestments, the thesis focuses on the proposed £14bn Wylfa Newydd project on Anglesey, on the northwest fringe of Wales. In the intersection of sociotechnical transitions, human geography, and science and technology studies (STS) literatures, the case study addresses the geographies of energy transitions, the politics of governing low-carbon investments, and the changing participation in large-scale infrastructural projects. The multi-scalar ethnographic study included both living in local communities and engaging with stakeholder organisations, from local councils to Whitehall ministries and multinational investors, through interviewing, document analysis, and meeting participations. Based on the findings, the thesis claims that the new nuclear project is better characterised as a megainvestment assembled together from diverse issues across multiple scales, from Welsh language protection to supply chain development, than as a technological object, an energy-generating source, or a financial megaproject. The megainvestment is transformative well beyond Anglesey with distinct practices and visions tied to the investment across various geographic scales. The governance of Wylfa Newydd is blurring the boundaries between public and private organisations with a shift towards collaborative platforms and coproduction of specialist knowledge. The public consultations displace the political controversies to legal wrangles and disputes on (geographic) boundaries by fragmenting affected publics and customising issues. In summary, this transformative project marks a new era of doing megainvestments on multiple geographic scales, with shifts in particular towards collaborative evidence-based governance and customised public consultations.

The ion exchange separation of sodium and potassium ions in the presence of hydrogen ions has been investigated using a new continuous countercurrent contacting technique. A wide range of ion exchange operations has been carried out using trace and gross ionic fractions of the alkali metals with contactors of different numbers of stages. By applying equilibrium stage theory the operating conditions have been selected to achieve good enrichment and/or recovery of the alkali metals. In trace experiments with a 15 stage contactor a Na+ recovery and enrichment of 46% and 9.2 respectively was achieved in the liquid product. A K+ enrichment of 11 was achieved in the resin in another 15 stage run. A contactor using three sections, called respectively the extraction, rectification and elution sections has been used to separate trace ionic fractions of sodium and potassium into two product streams. A 15 stage unit has given a Na+ enrichment and recovery of 2.9 and 91% in the Na+ rich stream and a K+ enrichment and recovery of 5.65 and 57.4% in the K+ rich stream with a loss in the resin waste of only 4.5% of the alkali metals in the feed. Results have been interpreted by equilibrium stage separation theory. Over a wide range of operating conditions the calculated stage efficiency varied (a) for a glass stage design from 36% to 70% and (b) for a perspex stage design from 60% to 110%. It was concluded that equilibrium stage theory can be used to predict the trace ion exchange separations using the new contacting technique and also that as the number of stages is changed the ion exchange separation will be altered in a predictable way. It was found impossible to get a good enrichment and recovery of Na+ ions when the two alkali metals were in gross ionic fractions in the feed solution. Results were shown to be reproducible. Mass transfer coefficients have been calculated. The equilibrium relations for the Na+/K+/H+ Cl- system with Zeo-Karb 225 were established to interpret the Na+/K+ continuous countercurrent separation results. In the binary Na+/H+ and K+/H+ systems it was found that the selectivity coefficients KNaH and KKH changed markedly as the loading of the respective alkali metals in the resin increased. When the alkali metals were in trace ionic fractions, the Na+/H+ and K+/H+ equilibria attained in the ternary Na+/K+/H+ system were the same as in the respective binary systems. However as the ionic fraction of the alkali metals was raised above the trace level, the Na+/H+ and K+/H+ equilibrium distributions differed increasingly from the respective binary system values.

La protection des travailleurs et du public est de primordiale importance dans toutes les phases de la chaîne de production des radionucléides, de la collecte . l’expédition, en passant par la gestion et l’élimination des déchets. Ce travail de thèse explore différents aspects de ces étapes. Les phases de la collecte dans l’installation CERN-Medicis ont été étudiées et la première idée de la chambre de collecte a été décrite. Dans le secteur des transports, l’Agence internationale de l’énergie atomique (AIEA) établit des règles strictes en matière de respect de la conception de nouveaux emballages. De plus, lorsque les activités produites d.passent certaines limites imposées par la réglementation, des emballages spécifiques doivent être utilisés pour le transport. Ils doivent assurer une protection optimale dans des conditions de transport normales et accidentelles et sont appel.s type B. Le coeur de cette étude est la conception d’un nouveau conteneur pour d.placer les échantillons irradiés du site de production aux radiopharmacies. La conception utilise la technique des calculs de Monte Carlo pour l’analyse de la radioprotection et la technique par éléments finis pour prévoir les performances de l’emballage dans les conditions d’essai. Un prototype a été réalisé et la procédure d’homologation a commencé. Pour certains radionucléides, les limites de transport ne sont pas tabulées et des valeurs générales sont utilisées. Une méthode utilisant des calculs de Monte Carlo a été mise en place pour recalculer ces quantités en fonction de leur risque réel. La méthode montre la possibilité d’augmenter la limite de transport pour une liste d’isotopes utilisés dans le domaine de la médecine nucléaire. Le processus de collecte des radionucléides a comme principale conséquence la production de matériaux hautement activés à traiter et à éliminer en tant que déchets. Un outil permettant de d.finir correctement le niveau de dangerosité récemment développé au CERN a été adapté aux scénarios d’irradiation typiques du cyclotron Arronax. / The protection of the workers and the public is of primary importance in all the phases of the radionuclides production chain, from the collection to the shipment, but also in the management and the disposal of the waste. This thesis works explore some aspects of those steps. The phases of the collection in the CERN-Medicis facility have been studied and the first idea of the collection chamber has been outlined. In the transport sector The International Atomic Energy Agency (IAEA) establish strict rules to respect for the design of new packages. Moreover when the activities produced exceed some limits imposed by the regulation per each radionuclides, specific containers shall be used for the transport. They must insure optimal protection in normal and accidental conditions of transport and are called type B. The core of this PhD study is the design of a new transport container to move the irradiated samples from the place of production to the radiopharmacies. The design makes use of several techniques, as Monte Carlo calculations for radiosafety analysis and finite element techniques to foresee the performance of the package under the testing conditions. A prototype has been realized and the homologation procedure started. For some radionuclides the transportation limits are not tabulated and general values are used to limit the activity to transport. A method making use of Monte Carlo calculations has been put in place to recalculate those quantities depending on their real hazard. The method shows the possibility to increase the transport limit for a list of isotopes used in the field of nuclear medicine. The process of radionuclidesÕ collection has as main consequence the production of highly activated materials to be treated and disposed as waste. A tool for a proper definition of the level of hazard recently developed at CERN has been customized for irradiation scenarios typical of the Arronax cyclotron.

The dissolution of a complex, simulated Magnox Waste (MW) glass has been investigated in batch and flow-through experiments at temperatures below 100 °C. The experiments were designed to investigate the dissolution rate dependence on the solution pH and temperature, and to examine the rate influencing effects of aqueous Si and Al species. At ambient laboratory temperatures, enhanced release of B (relative to Si) is observed in acidic buffer media in the pH range 2.1 ≤ pH ≤ 6.8. Normalised release rates of B and Si are similar in basic media in the pH range 7.8 ≤ pH ≤ 9.9. Congruent dissolution of the glass in basic media is surface reaction-controlled and accompanied by the development of secondary gels containing Si, Al, Mg, Fe and a range of additional glass components including d- and f-block elements. Gel development has been identified in both batch and flow-through experiments where significant quantities of glass-derived solutes accumulate in the leachate. Extensive dissolution of the glass at pH 2 (60 °C) is accompanied by the development of Si-rich leached layers at the glass surface and dissolution continues in solutions supersaturated with respect to amorphous silica. Examination of the acid leached glass revealed that regions of the glass which are relatively Si-rich are more durable than those regions which are enriched in metallic glass components. The kinetics of MW glass dissolution were investigated in single-pass flow-through experiments. These experiments were designed to investigate the effects of dissolved Al and Si on the rate of dissolution at fixed pH and temperature (pH 9 and 40 °C). The rate reducing effects of dissolved Al are far greater than those of dissolved Si on a mole per mole basis. In Si-rich alkaline solutions, the concentration of Al is controlled to very low levels by the development of secondary gels. In the absence of significant quantities of dissolved Al, and in systems where Al is extensively complexed by ethylenediamine tetra-acetic acid (EDTA), rates of glass dissolution decrease with increasing silicic acid activity. These data are compared with predictions based on a number of rate law formulations

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No description available.

The aim of this dissertation was to improve the biodegradation performance of a machine cutting oil employed in the processing of uranium at AWE. The machine cutting oil is chemically complex containing mineral oil, surfactants to improve emulsification and a phenolic biocide. Biodegradation was performed by a mixed culture of bacteria isolated from used cutting oil. Continuous, semi-batch and fed-batch systems were examined and stirred tanks and well-mixed biosupport reactors (immobilised cell systems) were compared. A continuous flow system was shown to provide a high rate of productivity with respect to COD removal. The extent of biodegradation would be important for a radioactive application and this ranged from 61-77% for hydraulic residence times of 10-53 hours, however it was noted that the extent of biodegradation was greater in the batch start-up period. The application of a Tween 80 emulsified feed to increase the bioavailability of the oil phase inhibited rather than improved the biodegradation performance. The use of a biosupport reactor improved biodegradation at shorter residence times. Development of these observations led to the operation of semi-batch (SBR) and fed-batch reactor systems (FBR). Following acclimatisation of the culture, the semi-batch systems consistently yielded higher extents of biodegradation in the range of 86-94% removal of COD for a bioprocess cycle of 5 days. The addition of n-hexadecane, as a readily metabolised co-substrate, to two semi-batch experiments did not noticeably increase biodegradation. A fed-batch configuration did not improve on the performance of the semi-batch configuration. GC-MS analysis of the extracted organics produced an unresolved complex mixture (UCM). Oxidation using chromium trioxide (CrO₃) of the UCM suggested that the remaining components were undegraded molecules from the base oil rather than excreted biodegradation intermediates. Phenotypic and genotypic assessment of the bacterial community showed that the overall diversity of the mixed culture was low. The bacterial population shifted throughout the batch period and diversity was further reduced as the cutting oil was degraded. Maximum diversity was observed at the start of the batch period and at steady state for the continuous system.