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Made available in DSpace on 2014-10-09T12:34:34Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:06:07Z (GMT). No. of bitstreams: 0 / A chave para o renascimento nuclear é a aceitação pública. Diante das necessidades energéticas que existem em todo o mundo e da escassez dos recursos disponíveis, o trabalho de caracterizar e propor novos modelos para representar a opinião pública é de extrema importância a todos os interessados. Embora o estudo da percepção pública sobre riscos seja recente, diversas abordagens do assunto foram sugeridas e apresentadas, em especial o tema das percepções acerca das instalações nucleares. A definição atual de risco, que transita entre modelos objetivos e subjetivos, reflete as opiniões frequentemente conflitantes do público e de especialistas nesse assunto. Estratégias de comunicação com o público podem ser julgadas a partir dos diversos modelos criados, e seus resultados registrados. O uso de modelos estruturais pode conferir um caráter tanto exploratório quanto confirmatório, sendo assim uma ferramenta adequada para desenvolver estudos sobre o tema da percepção pública em geral. Neste trabalho, um modelo estrutural é reapresentado a partir de dados obtidos num estudo anterior e completado com dados coletados depois do acidente nuclear de Fukushima, no Japão. Os efeitos causados por esse acidente ofereceram uma oportunidade única de estudar a opinião pública por meio dos efeitos de um acidente nuclear e a comunicação de riscos. Paralelamente a esse fato, buscou-se reavaliar o modelo estrutural de acordo com os resultados obtidos, de modo a sustentar um aprimoramento constante das ferramentas de trabalho. Ainda, uma comparação dos dados para grupos de interesse na modelagem de risco é apresentada, especificamente para os grupos de indivíduos do público e especialistas e em seguida, para grupos de alunos antes e depois de uma visita educativa à usina nuclear Almirante Álvaro Alberto. Como resultados, para os modelos estruturais, os dados obtidos foram aplicados aos modelos e analisados por meio de uma análise estrutural da matriz de correlação das variáveis latentes, da magnitude dos coeficientes estruturais e os valores de R2. Resultados indicam que a opinião pública mantém sua rejeição, e que a percepção de benefícios, frente aos riscos percebidos após o acidente, diminuiu. O novo modelo tratou de incluir a variável latente correspondente aos fatores emocionais, cujos resultados aumentaram a explicação da variável dependente, denominada propensão a aceitar energia nuclear. Já para os grupos analisados, a diferença de opinião entre os grupos segue as características esperadas em cada grupo, e indica alguns pontos de interesse para estratégias de comunicação e entendimento da formação opinião pública e de especialistas. Os efeitos da visita indicam que esta melhora a percepção de benefícios e reduz a percepção de medo e risco, mas que seus resultados podem ser insuficientes para promover uma mudança sólida numa opinião negativa em relação a estas instalações. / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

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The fission product releases from spherical fuel elements used in modern high temperature gas cooled reactors are one of the first source terms used in describing the safety of planned nuclear plants during normal and accident conditions. The verification and validation of the model and code used to predict the gaseous fission product behaviour and release from spherical fuel elements for the PBMR were documented in this dissertation. The PBMR is the latest design in high temperature gas cooled reactor technology utilizing spherical fuel elements based on the LEU TRISO-coated particle design. Fission products can be divided into relatively short-lived noble gas and halogens, and relatively long-lived metallic fission and activation products. Each group is described by its own models and sets of transport parameters. The noble gases and halogen fission product releases from the fuel elements are direct indications of fuel performance and are modelled by the Booth equation. The fission product release legacy code NOBLEG for noble gases and halogens was developed previously to calculate this diffusion model for high temperature reactors. The model and code are verified and validated for use in PBMR design and analyses under normal operating conditions. The history of irradiation experiments conducted on coated fuel particles and spherical fuel elements was investigated, and the most suitable irradiation tests with their post irradiation investigations were identified for the purpose of validation of the model and code. The model used to determine gaseous fission product behaviour and release from spherical fuel elements is described in detail. The application of this model in the code is verified mathematically with the Booth model, and by inspection of the source code. The thermohydraulic model used by NOBLEG to calculate fuel temperatures is verified with code to code comparisons with the core neutronics code VSOP. The irradiation tests HFR-K5 and -K6 were selected to validate the gaseous fission product code NOBLEG. An investigation was done into the development of NOBLEG to calculate gaseous fission product release under oxidizing conditions caused by water ingress events. New relationships were derived from water vapour injection tests done during the irradiation experiment HFR-K6, that allows NOBLEG to estimate the increase in gaseous fission product release under oxidizing conditions. A new model was proposed to explain peculiarities observed during the water injection tests. / Prof. P.P. Coetzee

No description available.

The induction motor is a highly utilised electrical machine in industry, with the nuclear industry being no exception. A typical nuclear power station usually contains more than 1000 motors, where they are used in safety and non-safety application. The efficient and fault-free operation of this machine is critical to the safe and economical operation of any plant, including nuclear power stations. A comprehensive literature review was conducted that covered the functioning of the induction machine, its common faults and methods of detecting these faults. The Condition Based Maintenance framework was introduced in which condition monitoring of induction machines is an essential component. The main condition monitoring methods were explained with the main focus being on Motor Current Signature Analysis (MCSA) and the various methods associated with it. Three analysis methods were selected for further study, namely, Current Signature Analysis, Instantaneous Power Signature Analysis (IPSA) and Motor Square Current Signature Analysis (MSCSA). Essentially, the methodology used in this dissertation was to study the three common motor faults (bearings, stator and rotor cage) in isolation and compare the results to that of the healthy motor of the same type. The test loads as well as fault severity were varied where possible to investigate its effect on the fault detection scheme. The data was processed using an FFT based algorithm programed in MATLAB. The results of the study of the three spectral analysis techniques showed that no single technique is able to detect motor faults under all tested circumstances. The MCSA technique proved the most capable of the three techniques as it was able to detect faults under most conditions, but generally suffered poor results in inverter driven motor applications. The IPSA and MSCSA techniques performed selectively when compared to MCSA and were relatively successful when detecting the mechanical faults. The fact that the former techniques produce results at unique points in the spectrum would suggest that they are more suitable for verifying results. As part of a comprehensive condition monitoring scheme, as required by a large population of the motors on a nuclear power station, the three techniques presented in this study could readily be incorporated into the Condition Based Maintenance framework where the strengths of each could be exploited.