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<p> This study is concerned with the multivariable stochastic regulatory control of a pilot plant fixed bed reactor which is interfaced to a minicomputer. The reactor is non-adiabatic with a highly exothermic, gaseous catalytic reaction, involving several independent species. A low order state space model for the reactor is developed starting from the partial differential equations describing the system. A parameter estimation method is developed to fit the model to experimental data. Noise disturbances present in the system are identified using two methods, and two alternative dynamic-stochastic state space models are obtained. Multivariable stochastic feedback control algorithms are derived from these models and are implemented on the reactor in a series of DDC control studies. The control algorithms are compared with each other and with a single loop controller. The best of the multivariable control algorithms is used to regulate the exit concentrations of the various species from the reactor and the results are compared to data.</p> / Thesis / Doctor of Philosophy (PhD)

This thesis documents significant contributions to the quantification of input and modelling uncertainties in the simulation of nuclear power plants. This work is intended to support the simulations that are performed to demonstrate the safety of nuclear power plants in general, and in CANDU reactors specifically. The work presented in this thesis extends the methodologies for uncertainty propagation established internationally to CANDU plants and pioneers the integration of these tools with important plant features in CANDUs, such as online fueling. This thesis documents a series of simulation studies performed to quantify the impact of uncertainties (primarily nuclear data uncertainties), on simulations of CANDU stations and light water reactors (LWRs). The novel part of this work includes quantifying the role of operational feedbacks such as online refuelling and reactor control systems, and important modelling uncertainties, on CANDU simulations. To achieve this objective, this thesis examines 4 important areas as documented in journal papers. To demonstrate understanding of the tools developed for the UAM-LWR benchmark and to support the ongoing international effort, select studies from the UAM-LWR benchmark study exercises were performed and published in the first journal paper. Time-dependent PWR neutronics exercises, considering both nuclear data and manufacturing uncertainties, were completed. This work found that the relative importance of nuclear data uncertainties and manufacturing uncertainties depended on whether the parameter of interest was “local”, such as pin power factors, or “global”, such as homogenized assembly properties. The second publication in this thesis documents the adaption of the tools from the first paper to consider CANDU specific features, such as spatial control systems and online refuelling. This paper demonstrated the significant effect that consistent feedback from fuelling operations has on reducing the total uncertainty in core level simulations of CANDU plants. The tools developed for this work were used to support downstream studies by generating extensive sets of realistic initial conditions for many different possible nuclear datasets. The next publications utilized the tools developed above and then extends the methods to include operational aspects of CANDUs in the assessments for the first time. In the third paper these methods were then used to demonstrate the tools’ capabilities to simulate an operational transient (a power maneuver from 100% full power to 59% full power) in a CANDU station and compared the resultant prediction and uncertainties to measure plant responses. A further study, on the role of nuclear data and initial burnup distribution uncertainty on a CANDU plant’s response to perturbations to liquid zone controller levels, was also performed to examine the effect of the commonly used “superposition principle” utilized in industry to make safety analysis of CANDU’s various fueling states more tractable. In both cases the role of nuclear data uncertainties was generally found to be similar in magnitude to the role of uncertainty in the core initial conditions. The results of this work support the continued safe operation of CANDU nuclear generating stations in Canada by quantifying the role of select uncertainties on safety simulation outputs, informing future BEPU analysis for CANDU plants and demonstrating the exceptional flexibility of the CANDU reactor design. This is reflected in one of the major conclusions of these works, which demonstrates that the natural feedbacks in CANDU operation help to minimize the effect of uncertainties in the outcome of many safety analysis. / Thesis / Candidate in Philosophy

La industria alimentaria necesita disponer de tecnologías y procesos industriales acordes a las exigencias actuales en cuanto a calidad nutricional y cuidado del medio ambiente, y a su vez que le resulten económicamente convenientes. Las grasas sólidas y semisólidas se han producido a partir de aceites vegetales desde hace décadas utilizando distintas tecnologías, siendo uno de los objetivos actuales de su producción evitar introducir o generar compuestos perjudicia-les para la salud del consumidor. La acidólisis enzimática, pro-ceso que consiste en utilizar lipasas como biocatalizadores para incorporar ácidos grasos específicos en la estructura de los triglicéridos, se vislumbra como una alternativa válida para cumplir dicho objetivo. En la presente tesis se estudia la producción de biocatalizadores sólidos y su accionar en la reacción de acidólisis entre aceite de girasol y ácidos grasos saturados libres, llevándola a cabo tanto en reactor batch como en uno de lecho empacado. En el Capítulo 1 se hace una introducción general al tema de estudio junto con la revisión bibliográfica general. Los materiales utilizados y los métodos generales de análisis empleados se describen en el Capítulo 2. Los métodos específicos se describen en el lugar donde se plantea su utilización. En el Capítulo 3 se analizan las características más relevantes para esta tesis del pre-parado comercial de lipasas de Rhizomucor miehei, así como la capacidad de las mismas para catalizar la reacción de interés en su estado libre. Los Capítulos 4 y 5 se centran en la pro-ducción de los biocatalizadores sólidos. En el Capítulo 4 se analizan los métodos de inmovilización de las lipasas por adsor-ción. En el Capítulo 5 se describe la preparación y modifica-ción de microesferas de quitosano a fin de ser empleadas como soportes, junto a la caracterización de las mismas me-diante diversas técnicas. Obtenido el biocatalizador que se consideró de mejor desempeño en la reacción de interés, en el Capítulo 6 se realizó el análisis de las condiciones de reacción propiamente dichas, seleccionando los niveles óptimos de las variables, y en el Capítulo 7 se indagó acerca del comporta-miento cinético de este sistema en reactores batch. La construcción y modos de funcionamiento del reactor de lecho empacado se describen en el Capítulo 8, donde también se desarrolla el modelado y simulación de este sistema, inclu-yendo la resistencia a la transferencia de materia. Por último, en el Capítulo 9 se presentan las conclusiones generales a las cuales se abordó con el estudio desarrollado en la presente tesis. / The food industry requires new technologies and processes in line with the current requirements in terms of nutritional quality and environmental care, being at the same time economically profitable. For decades, different technologies have been used to produce solid and semisolid fats. One of the main goals of current processes is to avoid the introduc-tion or generation of compounds which are harmful to human health. Enzymatic acidolysis, which consists in the incor-poration of specific fatty acids in the glycerol backbone of triglycerides, appears as a valid alternative to fulfill this objec-tive. In the present thesis the production of solid biocatalysts and their performance in the acidolysis reaction between sunflower oil and free saturated fatty acids, in batch and packed bed reactor configuration, is studied. In Chapter 1 a general introduction to the subject and the bibliographic revision are presented. The different materials employed, as well as the general analytical methods used throughout the development of this thesis, are described in Chapter 2. The specific methods are detailed in the corresponding sections where their applications are presented. The most relevant characteristics of commercial preparations of Rhizomucor miehei lipases, as well as their capability to act in free form on the reaction in study, are analyzed in Chapter 3. Chapters 4 and 5 are focused on the solid biocatalysts production. In Chapter 4 different lipase immobilization methods based on adsorption principle are analyzed. In Chapter 5 the prepara-tion and modification of chitosan microspheres intended to be used as supports, together with their characterization, are described. Once the most appropriate biocatalyst was ob-tained, the reaction conditions analysis, along with the selection of their optimum values, was developed in Chapter 6. In Chapter 7 the kinetic behaviour of batch reaction systems was studied. The construction and operating mode of the packed bed reactor are described in Chapter 8. In addition, the modeling and simulation of the system, including mass transfer resistance considerations, are also developed. Finally, the main conclusions that can be drawn from the studies developed in the present thesis are presented in Chapter 9.

A series of fuel cycle simulations were performed using CEA's reactor physics code ERANOS 2.0 to analyze the transmutation performance of the Subcritical Advanced Burner Reactor (SABR). SABR is a fusion-fission hybrid reactor that combines the leading sodium cooled fast reactor technology with the leading tokamak plasma technology based on ITER physics. Two general fuel cycles were considered for the SABR system. The first fuel cycle is one in which all of the transuranics from light water reactors are burned in SABR. The second fuel cycle is a minor actinide burning fuel cycle in which all of the minor actinides and some of the plutonium produced in light water reactors are burned in SABR, with the excess plutonium being set aside for starting up fast reactors in the future. The minor actinide burning fuel cycle is being considered in European Scenario Studies. The fuel cycles were evaluated on the basis of TRU/MA transmutation rate, power profile, accumulated radiation damage, and decay heat to the repository. Each of the fuel cycles are compared against each other, and the minor actinide burning fuel cycles are compared against the EFIT transmutation system, and a low conversion ratio fast reactor.

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