A series of (123)I measurements have been carried out in a 4π(e(A),X)-γ coincidence system. The experimental extrapolation curve was determined and compared to Monte Carlo simulation, performed by code ESQUEMA. From the slope of the experimental curve, the total conversion coefficient for the 159 keV total gamma transition, α(159), was determined. All radioactive sources were also measured in an HPGe spectrometry system, in order to determine the gamma-ray emission probability per decay for several gamma transitions. All uncertainties involved and their correlations were analyzed applying the covariance matrix methodology and the measured parameters were compared with those from the literature.
In this work the procedure developed for the standardization of 182 Ta sources produced by irradiation at the IPEN IEA-R1 research reactor is presented. The 182 Ta decays with a half-life of 114 days by β − emission, populating the excited levels of 182 W. It emits gamma rays with several energies mainly between 31 keV and 264 keV and between 1001 keV and 1453 keV. The measurements were performed in a 4πβ−γ coincidence system by using the extrapolation technique. The coincidence system is composed of a 4π proportional counter coupled to a NaI(Tl) cristal. The measurements were undertaken selecting two windows in the γ-channel, in order to check the consistency of the results. A Monte Carlo calculation was performed in order to predict the behavior of the observed activity as a function of the 4πβ detector efficiency and the results were compared to experimental values. The most intense gamma-ray emission probabilities of 182 Ta were determined by means of an HPGe gamma spectrometer, the germanium efficiency curve was obtained by using sources 152 Eu, 241 Am, 60 Co, 133 Ba and 166m Ho standardized in a primary system. The uncertainties 4 Resultados e Discussões .
Agradeço à orientadora Profa. Dra. Marina Fallone Koskinas, pela oportunidade oferecida, compreensão nos momentos de dificuldade, pela paciência, pela ajuda e pelo exemplo de orientadora e pessoa. Ao Prof. Dr. Mauro da Silva Dias, pela contribuição a este trabalho, sob a forma de preciosas sugestões e discussões desde o inicio do projeto até sua concretização. À Msc. Ione M. Yamazaki, pela ajuda no laboratório, com a confecção dos filmes. Ao Instituto de Pesquisas Energéticas e Nucleares, IPEN-CNEN/SP, por ter disponibilizado as instalações e a infra-estrutura do Centro de Reator de Pesquisas, CRPq, para a realização deste trabalho. Aos meus amigos, Bruno, Túlio e Iara, que pude conhecer após ingressar à faculdade, e que continuaram me ajudando e apoiando ao longo de todos esses anos. Aos colegas e amigos que pude conhecer após ingressar ao Mestrado, que contribuíram não somente nas disciplinas, mas como na realização deste trabalho. Agradecimento especial a Andréia e a Tatiane. Aos meus amigos, que sempre estiveram presentes em toda a minha vida, e aos amigos que surgiram ao longo dos anos, que sempre me apoiaram, me ajudaram em todos os momentos, e que são muitos importantes para mim: Aline, Fernando, Marília, Marina e Maêva. E finalmente, à minha família, aos meus pais, Shoko Gishitomi e Claudete da S. Gishitomi, e as minhas irmãs, Nathalia C. Gishitomi e Mariana C. Gishitomi, pela ajuda, compreensão, pelo carinho e apoio durante toda minha vida. Tudo o que eu sou eu devo a vocês.
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