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Master's Dissertation
DOI
https://doi.org/10.11606/D.85.2021.tde-14072021-104200
Document
Author
Full name
Ruanyto Willy Correia
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 2021
Supervisor
Committee
Zeituni, Carlos Alberto (President)
Karam Junior, Dib
Taddei, Maria Helena Tirollo
Title in Portuguese
Análise da pureza radioativa de iodo-125 produzido no reator nuclear IEA-R1 pelo método de espectrometria gama e comparação com a exigência internacional
Keywords in Portuguese
braquiterapia
HPGe
iodo-125
iodo-126
Abstract in Portuguese
Com a finalidade de otimizar a produção, a irradiação e a quantificação de iodo-125 utilizado na confecção de sementes de iodo para braquiterapia, uma metodologia teórico-experimental foi aplicada baseada no procedimento proposto por COSTA, O. L., 2015, em que iodo-125 é obtido via ativação neutrônica no reator nuclear IEA-R1 a partir da irradiação de xenônio-124 encapsulado em compartimentos de alumínio. Após todo o preparo das amostras seguindo o processo descrito, iniciou-se o processo de irradiação sob o fluxo de nêutrons da ordem de 1013 nêutrons.cm-2.s-1 por diferentes períodos de tempo. Foram irradiadas seis cápsulas (duas contendo Xe-124 natural e quatro contendo Xe-124 enriquecido 99,9%) a fim de comparar a atividade total produzida variando o parâmetro de enriquecimento da amostra. Depois de serem irradiadas, as capsulas foram abertas e lavadas em meio alcalino aquecido para extração do iodo depositado nas paredes internas. As soluções geradas foram armazenadas em diferentes frascos padrões de acrílico, nomeadas e quantificadas via espectrometria gama com Detector de Germânio Hiperpuro (HPGe ORTEC modelo GEM-C5970-B) para determinação da pureza do radionuclídeo de interesse. Para calibração do HPGe foi aplicada uma metodologia experimental utilizando uma fonte de calibração certificada de bário-133 com atividade bem conhecida em que as eficiências dos fotopicos energéticos foram medidos entre 0 - 667 keV. As curvas de eficiência foram determinadas para uma faixa de energia que cobrissem toda a região de interesse espectral para o iodo-125 e seus subprodutos gerados na reação nuclear, além disso, elas foram construídas para diferentes distâncias da janela do detector e dimensões do frasco padrão de análise. No processo de ativação, iodo-126 foi formado como subproduto indesejado, esse radionuclídeo foi quantificado e sua atividade determinada. Finalmente, foi possível determinar a pureza radionuclídica do iodo-125 e compará-la com as exigências internacionais de qualidade que regulam a produção de medicamentos radioativos.
Title in English
Analysis of radioactive purity of iodine-125 produced in the nuclear reactor IEA-R1 by the gamma spectrometry method and comparison with the international requirement
Keywords in English
brachytherapy
HPGe
iodine-125
iodine-126
Abstract in English
In order to optimize the production, irradiation and quantification of iodine-125 used in the manufacture of iodine seeds for brachytherapy, a theoretical-experimental methodology was applied based on the procedure proposed by COSTA, O. L, 2015, in which iodine-125 it is obtained via neutron activation in the nuclear reactor IEA-R1 from the irradiation of xenon-124 encapsulated in aluminum compartments. After all the preparation of the samples following the described process, the irradiation process started under the neutron flux in the order of 1013 neutrons.cm-2.s-1 for different periods of time. Six capsules were irradiated (two containing natural Xe-124 and four containing 99.9% enriched Xe-124) in order to compare the total activity produced by varying the sample enrichment parameter. After being irradiated, the capsules were opened and washed in a heated alkaline medium to extract the iodine deposited on the inner walls. The generated solutions were stored in different standard acrylic flasks, named and quantified via gamma spectrometry with Hyperpure Germanium Detector (HPGe ORTEC model GEM-C5970-B) to determine the purity of the radionuclide of interest. To calibrate the HPGe, an experimental methodology was applied using a certified barium-133 calibration source with well-known activity in which the efficiency of the energy photopics were measured between 0 - 667 keV. The efficiency curves were determined for an energy range that covered the entire region of spectral interest for iodine-125 and its by-products generated in the nuclear reaction, in addition, the efficiency curves were constructed for different distances from the detector window and dimensions of the standard analysis flask. In the activation process, iodine-126 was formed as an unwanted by-product, this radionuclide was quantified and its activity determined. Finally, it was possible to determine the radionuclide purity of iodine-125 and compare it with the international quality requirements that regulate the production of radioactive drugs.
 
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Publishing Date
2021-07-16
 
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