The effects of neutron displacement damage on materials are sensitive to neutron energy spectra. In controlled neutron damage experiments, a well characterized neutron flux spectrum is critical in determining the equivalent dose for displacement damage. Two techniques were used to characterize the neutron flux spectra in the University of Texas at Austin TRIGA research nuclear reactor. The first technique uses a standard method of measuring the reaction rates of two identical metal foils, one of which was irradiated in a Cd cover, the other of which was irradiated bare. Assuming an analytic form of the neutron spectrum the reaction rates were used to determine an approximate spectrum. The second technique uses the reaction rates measured from a set of activated metal foils along with two spectral unfolding techniques to approximate and then refine the neutron spectrum. A Matlab code was developed which fits radiative capture reaction rates to an approximate spectrum using a least squares approach. The result was used as an initial guess in a second Matlab code which refines the epithermal and fast energy ranges of the spectrum using reaction rates from threshold reactions. Errors in the reaction rates calculated from the resulting spectrum to the measured reaction rates were used to assess the accuracy of the final neutron spectrum. / text

Made available in DSpace on 2014-10-09T12:44:05Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:08:20Z (GMT). No. of bitstreams: 1 06891.pdf: 3372488 bytes, checksum: 65b8800e6379779a3f9693d8cbc1c688 (MD5) / Dissertacao [Mestrado] / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares, Sao Paulo

Made available in DSpace on 2014-10-09T12:44:05Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:08:20Z (GMT). No. of bitstreams: 1 06891.pdf: 3372488 bytes, checksum: 65b8800e6379779a3f9693d8cbc1c688 (MD5) / Dissertacao [Mestrado] / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares, Sao Paulo

No description available.

Made available in DSpace on 2014-10-09T12:45:28Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:59:12Z (GMT). No. of bitstreams: 1 07294.pdf: 5846807 bytes, checksum: a4bf44d31daa27de538647b817894a6c (MD5) / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2014-10-09T12:33:40Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:04:05Z (GMT). No. of bitstreams: 0 / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP

Made available in DSpace on 2014-10-09T12:45:28Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:59:12Z (GMT). No. of bitstreams: 1 07294.pdf: 5846807 bytes, checksum: a4bf44d31daa27de538647b817894a6c (MD5) / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2014-10-09T12:33:40Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:04:05Z (GMT). No. of bitstreams: 0 / Este trabalho apresenta os resultados dos valores de fluxo de nêutrons obtidos a partir da implantação de uma armadilha de nêutrons no núcleo do Reator IPEN/MB-01. Foram analisadas várias configurações de armadilhas implantadas no núcleo do reator IPEN/MB-01 de forma a se eleger a armadilha mais eficiente. Para a caracterização energética, foram irradiados no centro da armadilha de nêutrons, detetores de ativação de vários materiais diferentes (Au, Sc, In, Ti, Ni). As respectivas espectrometrias gama desses elementos após a irradiação com e sem cobertura de cádmio, forneceram valores experimentais das taxas de reação nuclear (atividade de saturação) por núcleo alvo e as respectivas incertezas que servem de entrada ao código SANDBP que calculou o espectro de energia dos nêutrons no centro do Flux-Trap em 50 grupos de energia, utilizando-se dos espectros de entrada calculados na posição de irradiação (centro do \"Flux Trap\") por códigos de Física de Reatores. Os resultados obtidos constataram um aumento do fluxo de nêutrons térmico no centro da armadilha da configuração 203 em relação a configuração sem armadilha (padrão) da ordem de 350% sem contudo haver a necessidade de se aumentar a potência do reator. Foram também efetuadas comparações entre os espectros desdobrados obtidos pelo SANDBP, em relação aos calculados pelos códigos MCNP-4C e XSDRNPM. A caracterização espacial do fluxo de nêutrons térmicos é feita com folhas de ativação na forma de uma liga infinitamente diluída em massa de 1% de Au e 99% de Al em alguns pontos internos da configuração 203 (axialmente ao Flux Trap\" e adjacências radiais) e os resultados mostraram um aumento significativo da magnitude de seus valores quando comparados a configuração padrão retangular. / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP

A python code was developed to compute the alpha knock-on (AKN) neutron spectrum using two already available computational tools. The code was used to calculate the AKN for a given discharge from the DTE2 JET campaign. Results showed that the beam-target contribution dominated the neutron spectra and obscured the AKN tail. A spatial profile of the AKN intensity was created which showed that the majority of the AKN reactions happen in the center of the plasma, but further analysis is needed to get a better picture of whether the AKN component will be measurable or not.

Made available in DSpace on 2014-10-09T12:52:25Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:01:35Z (GMT). No. of bitstreams: 0 / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP