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Doctoral Thesis
Full name
Vitor Ottoni Garcia Arêdes
Knowledge Area
Date of Defense
São Paulo, 2020
Mesquita, Roberto Navarro de (President)
Bitelli, Ulysses D'Utra
João, Thiago Garcia
Rossi, Pedro Carlos Russo
Title in Portuguese
Nova metodologia experimental para medida de taxa de reação nuclear no combustível do Reator IPEN/MB-01 (Tipo Varetas)
Keywords in Portuguese
cobertura de cádmio
medidas experimentais
taxa de reação
vareta combustível
Abstract in Portuguese
O presente estudo foi realizado para propor a validação de um novo método de medida experimental de taxas de reação nuclear epitérmicas (taxas de reação nuclear na faixa de energia do espectro neutrônico acima de 0,55eV), induzidas em detectores de ativação, dentro da vareta combustível. Foram realizados experimentos de irradiação de detectores de ativação (folhas de ativação) dos materiais, Au, Sc, Ni, Ti, In e Mg, utilizando uma nova configuração de cobertura de cádmio, bem como irradiações dos detectores sem a cobertura de cádmio. Cálculos com o software MCNP5, foram utilizados para comparação e validação dessa nova metodologia. A inserção de reatividade negativa da cobertura de cádmio não impôs restrição ao método, ficando bem abaixo dos 500pcm regulados pela IAEA. O novo dispositivo de cobertura de cádmio garantiu o posicionamento correto para os detectores. Resultados de taxas de reação com e sem a cobertura de cádmio de detectores com seção de choque de ativação em faixas de atuação epitérmica do espectro neutrônico, bem como das razões espectrais, evidenciaram baixa perturbação causada pela presença do cádmio no sistema. Os resultados das comparações entre os valores medidos experimentalmente e calculados computacionalmente (MCNP5 e SANDBP) tiveram boa concordância estatística, com desvios próximos a 5%.
Title in English
New experimental methodology for measuring the nuclear reaction rate in the fuel of the IPEN/MB-01 Reactor (Rods Type)
Keywords in English
cadmium coverage
experimental measurement
fuel rod
reaction rates
Abstract in English
The present study was performed in order to validate a new methodology for experimental measurement of epidermal nuclear reaction rates (neutrons energy > 0.55eV), induced in activation foils, inside the fuel rod. Experiments with activation detectors through irradiation (activation foill) of Au, Sc, Ni, Ti, In e Mg, were carried out in the region of interest using a new configuration of cadmium coverage, as well as irradiations of detectors without cadmium coverage. Calculations with the MCNP5 were implemented aiming the comparison and validation of this new methodology. The insertion of negative reactivity of the cadmium coverage does not impose restrictions on the applied method, keeping below of the 500 pcm regulated by the IAEA. The new cadmium coverage device ensures correct placement for detectors. Results of reaction rates, bare and coverage with cadmium, of detectors with activation cross section for neutron energy > 0,55eV, and the spectral ratios, showed low disturbance caused by the presence of cadmium in the system. The comparisons between the values measured experimentally and computationally calculated (MCNP5 and SANDBP) had good statistical agreement, with deviations close to 5%.
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