This research focuses on modelling reflectors in typical material testing reactors (MTRs). Reflectors present some challenges to the usual approach to full-core calculational models. Diffusion theory is standardly used in full-core calculations and is known to be inaccurate in regions where the flux is anisotropic, for example within the reflectors. Thus, special consideration should be given to reflector models. In this research, normalised generalised equivalence theory is used to homogenise cross-sections and calculate equivalent nodal parameters and albedo boundary conditions for the reflector surrounding a typical MTR reactor. Various studies have shown that equivalence theory can be used to accurately generate equivalent nodal parameters for the core and reflector regions of large reactors, such as pressurised and boiling water reactors, in one dimension and for two neutron energy groups. This has not been tested for smaller reactors where leakage, environment sensitivity and multi-group spectrum dependency are much larger. The SAFARI-1 MTR reactor is modelled in this work. A thirty day operational cycle is simulated for this reactor, using the nodal diffusion code MGRAC. NGET reflector equivalent nodal parameters are calculated using the codes NEWT and EQUIVA. The impact of different reflector models are evaluated, based on their effect on the core power, flux distribution, reactivity and neutron leakage over the duration of the operational cycle. It is found that homogenisation introduces some environment dependencies in the reflector parameters, particularly in the corners of the reactor core. In full-core calculations, the reflector parameters show some sensitivity to the in-core reflector structures, but not the fuel composition. A practical reflector model for SAFARI-1 is proposed, which proves that NGET equivalence theory can be used for multi-group reflector modelling in a small MTR reactor. This approach to reflector modelling simplifies the core model, increases the accuracy of a diffusion calculation, and increases the efficiency (shorter calculational time and better convergence behaviour) of computer simulations. / Thesis (MSc (Engineering Sciences in Nuclear Engineering))--North-West University, Potchefstroom Campus, 2013.

This research focuses on modelling reflectors in typical material testing reactors (MTRs). Reflectors present some challenges to the usual approach to full-core calculational models. Diffusion theory is standardly used in full-core calculations and is known to be inaccurate in regions where the flux is anisotropic, for example within the reflectors. Thus, special consideration should be given to reflector models. In this research, normalised generalised equivalence theory is used to homogenise cross-sections and calculate equivalent nodal parameters and albedo boundary conditions for the reflector surrounding a typical MTR reactor. Various studies have shown that equivalence theory can be used to accurately generate equivalent nodal parameters for the core and reflector regions of large reactors, such as pressurised and boiling water reactors, in one dimension and for two neutron energy groups. This has not been tested for smaller reactors where leakage, environment sensitivity and multi-group spectrum dependency are much larger. The SAFARI-1 MTR reactor is modelled in this work. A thirty day operational cycle is simulated for this reactor, using the nodal diffusion code MGRAC. NGET reflector equivalent nodal parameters are calculated using the codes NEWT and EQUIVA. The impact of different reflector models are evaluated, based on their effect on the core power, flux distribution, reactivity and neutron leakage over the duration of the operational cycle. It is found that homogenisation introduces some environment dependencies in the reflector parameters, particularly in the corners of the reactor core. In full-core calculations, the reflector parameters show some sensitivity to the in-core reflector structures, but not the fuel composition. A practical reflector model for SAFARI-1 is proposed, which proves that NGET equivalence theory can be used for multi-group reflector modelling in a small MTR reactor. This approach to reflector modelling simplifies the core model, increases the accuracy of a diffusion calculation, and increases the efficiency (shorter calculational time and better convergence behaviour) of computer simulations. / Thesis (MSc (Engineering Sciences in Nuclear Engineering))--North-West University, Potchefstroom Campus, 2013.

Made available in DSpace on 2014-06-11T19:26:11Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-04-24Bitstream added on 2014-06-13T20:14:51Z : No. of bitstreams: 1 oliveira_em_me_rcla.pdf: 2211300 bytes, checksum: 15a4c95980d17475b36dd5893d6e6bcf (MD5) / A presente pesquisa propôs a elaboração da carta geológico-geotécnica na região do oleoduto “Guararema – São José dos Campos” com o intuito de subsidiar a elaboração de cartas de sensibilidade ambiental ao derramamento de petróleo e derivados, no Vale do Paraíba. A área estudada localiza-se no leste do estado de São Paulo e caracteriza-se pelo contraste de relevo entre as Colinas Sedimentares da Bacia de Taubaté e os Morros Cristalinos das serras do Mar e Mantiqueira; pela diversidade litológica (gnaisses, xistos, granitos, arenitos, argilitos, siltitos, entre outras); pela presença do rio Paraíba do Sul, da represa de Santa Branca e de Áreas de Proteção Ambiental. Esta área é cortada pelo duto que parte do Terminal de Guararema, seguindo até a Refinaria de São José dos Campos e já foi alvo de acidentes relacionados com dutovias (1987, 1994 e 1998). Tais acidentes podem ocorrer novamente, ameaçando a qualidade ambiental da área. As cartas de sensibilidade ambiental. podem auxiliar na redução das conseqüências ambientais do vazamento e tornar eficientes os esforços de contenção e limpeza/remoção, além de servir como suporte técnico a outras atividades socioeconômicas e de gestão ambiental. O método utilizado para a execução do trabalho foi composto por: 1. Pesquisa Bibliográfica; 2. Preparação de Base Cartográfica; 3. Compartimentação do Terreno, Caracterização do Meio Físico, através do método de Unidades Básicas de Compartimentação - UBCs e elaboração de carta preliminar; 4. Trabalho de Campo; 5. Definição dos condicionantes do meio físico; 6. Elaboração da carta Geológico-Geotécnica e; 7. Elaboração da Dissertação.Como resultado, obteve-se os condicionantes do meio físico de interesse às cartas de sensibilidade ambiental para áreas terrestres (tipo de relevo e suas formas; declividade das encostas... / The present work proposed to elaborate a geological-geotechnical map, for the “Guararema- São José dos Campos” pipe-line to subzide the elaboration of Environmental Sensitivity to Oil and Derivatives Spill Maps, in Vale of Paraíba. The area is situated in the east São Paulo state and is caracterized for contrast of the Sedimentary Hills of Basin Tubaté and Crystaline Mounts of Serra do Mar and Mantiqueira; different litologis (gnaiss, shales, granites, sandstone, claystone, siltstone, etc.), the presence of the Paraíba of Sul river, the Santa Branca dam, environmental protection areas and the “Guararema-São José dos Campos” pipe-line. Accidents with pipe-line happened yet (1987, 1994 and 1998) and can occur again, minimizing the environment quality. Hence, a geotechnical cartography metodology has been adopted - Basic Compartiment Units (BCU’s) – the following cartography document, on a 1: 50,000 scale, was made: a Geological-Geothecnical Units map, with seven units (one in Fluvial Plan and two in Sedimentary Hills and four in Crystalline Mounts) accompanied by a syntesis table of the physical environment conditioners. These results allows us to affirm that the geological-geotechnical maps can be instruments used in the making of Environmental Sensitivity Maps in inland areas. The physical environment attributes are: type and forms of relief, declivity, type rivers, depth of the water level, tipe of soils and litologis, characteristics of soil/rocks (discontinuities, porosity, permeability, the aquifer’s recharge capacity and the potential retention of the contaminant.

Orientador: José Eduardo Zaine / Banca: Lucília do Carmo Giordano / Banca: Paulina Setti Riedel / Resumo: A presente pesquisa propôs a elaboração da carta geológico-geotécnica na região do oleoduto "Guararema - São José dos Campos" com o intuito de subsidiar a elaboração de cartas de sensibilidade ambiental ao derramamento de petróleo e derivados, no Vale do Paraíba. A área estudada localiza-se no leste do estado de São Paulo e caracteriza-se pelo contraste de relevo entre as Colinas Sedimentares da Bacia de Taubaté e os Morros Cristalinos das serras do Mar e Mantiqueira; pela diversidade litológica (gnaisses, xistos, granitos, arenitos, argilitos, siltitos, entre outras); pela presença do rio Paraíba do Sul, da represa de Santa Branca e de Áreas de Proteção Ambiental. Esta área é cortada pelo duto que parte do Terminal de Guararema, seguindo até a Refinaria de São José dos Campos e já foi alvo de acidentes relacionados com dutovias (1987, 1994 e 1998). Tais acidentes podem ocorrer novamente, ameaçando a qualidade ambiental da área. As cartas de sensibilidade ambiental. podem auxiliar na redução das conseqüências ambientais do vazamento e tornar eficientes os esforços de contenção e limpeza/remoção, além de servir como suporte técnico a outras atividades socioeconômicas e de gestão ambiental. O método utilizado para a execução do trabalho foi composto por: 1. Pesquisa Bibliográfica; 2. Preparação de Base Cartográfica; 3. Compartimentação do Terreno, Caracterização do Meio Físico, através do método de Unidades Básicas de Compartimentação - UBCs e elaboração de carta preliminar; 4. Trabalho de Campo; 5. Definição dos condicionantes do meio físico; 6. Elaboração da carta Geológico-Geotécnica e; 7. Elaboração da Dissertação.Como resultado, obteve-se os condicionantes do meio físico de interesse às cartas de sensibilidade ambiental para áreas terrestres (tipo de relevo e suas formas; declividade das encostas... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The present work proposed to elaborate a geological-geotechnical map, for the "Guararema- São José dos Campos" pipe-line to subzide the elaboration of Environmental Sensitivity to Oil and Derivatives Spill Maps, in Vale of Paraíba. The area is situated in the east São Paulo state and is caracterized for contrast of the Sedimentary Hills of Basin Tubaté and Crystaline Mounts of Serra do Mar and Mantiqueira; different litologis (gnaiss, shales, granites, sandstone, claystone, siltstone, etc.), the presence of the Paraíba of Sul river, the Santa Branca dam, environmental protection areas and the "Guararema-São José dos Campos" pipe-line. Accidents with pipe-line happened yet (1987, 1994 and 1998) and can occur again, minimizing the environment quality. Hence, a geotechnical cartography metodology has been adopted - Basic Compartiment Units (BCU's) - the following cartography document, on a 1: 50,000 scale, was made: a Geological-Geothecnical Units map, with seven units (one in Fluvial Plan and two in Sedimentary Hills and four in Crystalline Mounts) accompanied by a syntesis table of the physical environment conditioners. These results allows us to affirm that the geological-geotechnical maps can be instruments used in the making of Environmental Sensitivity Maps in inland areas. The physical environment attributes are: type and forms of relief, declivity, type rivers, depth of the water level, tipe of soils and litologis, characteristics of soil/rocks (discontinuities, porosity, permeability, the aquifer's recharge capacity and the potential retention of the contaminant. / Mestre