MARCOS MEDRADO DE ALENCAR

MARCOS MEDRADO DE ALENCAR

Página do item completo

Resultados de Busca

Agora exibindo 1 - 10 de 16

Challenges in measuring 22Na in rainfall by gamma spectrometry in the city of São Paulo, Brazil
2023 - DAMATTO, S.R.; DOMINGOS, R.M.; TEIXEIRA, L.; ISIKI, V.L.; ALENCAR, M.M.; LEONARDO, L.
Na-22 is a naturally occurring radionuclide of cosmogenic origin with half live of 2.6 years, being a beta and gamma emitter (541keV and 1274.5keV, respectively). This cosmogenic radionuclide is mainly formed when cosmic rays interact with argon nucleus, occurring a fragmentation of this nucleus. The process of production of 22Na occur continually in upper atmosphere, lower stratosphere and rainfall is the predominantly process of deposition of cosmogenic radionuclides in terrestrial surface. Na-22 together with 7Be (T1/2) = 53.3 d, gamma ray 476.7keV) can be used as tracers in studies of aerosol transport between layers of the atmosphere. At the same time 22Na is rarely used in these studies due to its extremely low abundance in rainfall. The objectives of this work were to present the first results 22Na activity concentration measured in rainfall collected at the IPEN campus located in São Paulo, Brazil. Large volumes of rainfall samples were collected from October 2022 to April 2023, totaling 20 samples, and 22Na activity concentration was measured by non-destructive gamma-ray spectrometry using a coaxial Be-layer HPGe detector with 46% relative efficiency and associated electronic devices and live counting time varying from 250,000 s to 500,000 s; the rainfall volumes ranged from 14 L to 164 L. The collection container was previously acidified with 1mol L-1 HNO3 to avoid loss of radionuclide by absorption on the container walls. The first eight rainfall samples were collected in a catchment area of 1m2, which was not enough to measure the radionuclide, since all the determined results were smaller than the detection limit of the methodology. After these results, it was decided to increase the catchment area by collecting rainfall samples from the roof of the laboratory building, in an area of 78 m2; the container used to collect samples from this area was also acidified with 1 mol L-1 HNO3. In this new area, 12 rainfall samples were collected, however, as the volume of rainfall was very large in the rains collected, only one sample was acidified, a rainfall of 2 mm and a volume of 98 L; in the other samples, the large volume of rain did not allow the water to become acidic because the collection container overflowed with water. In the acidified rainfall sample, the result of 0.725 ± 0.252 Bq L-1 was determined for the radionuclide 22Na. With this result, it is possible to prove the importance of both the catchment area and the acidulation of the sample in the determination of trace radionuclides in rainfall samples.
Counting efficiency in gamma-ray spectrometry with different sample volumes for the same geometry
2022 - NISTI, M.B.; MADUAR, M.F.; DAMATTO, S.R.; ALENCAR, M.M.
The aim of this study is to determine an easy and fast method to calculate efficiencies in different volumes, in the same counting geometry, for gamma-ray spectrometry technique. Reference Material Soil IAEA 326 was packed in a 100 mL capacity polyethylene bottle with different masses and volumes, and sealed for about four weeks, prior measurement, in order to ensure that radioactive equilibrium had been reached between 226Ra and its progeny. After this time, they were measured by gamma-ray spectrometry with a hyper-pure germanium detector. The masses of the reference material used were 25, 60, 80, 95 and 128g. The energies of gamma-rays used in this paper are recommended due to the considerations: gamma intensity value, peak quality, spectral region without interference and the gamma- ray energies of the 238U and 232Th series very important for determining the natural radioactivity. The efficiency values obtained compared to the adjusted efficiency values were similar and presented a good correlation coefficient. The performance was acceptable for all different masses studied, indicating results consistent for the method. The proposed method could be useful as a tool for laboratories, dealing with of samples on a routine basis, by reducing the cost on the purchase of another counting geometry and optimizing the use of the detection system, thus improving their performance.
Monitoração radiológica dos efluentes gasosos do reator IEA-R1 do IPEN
2022 - GABRIEL, LUIZ H.; RODRIGUES, CARLOS E.C.; NOGUEIRA, PAULO R.; DAMATTO, SANDRA R.; ISIKI, VERA L.K.; TEIXEIRA, LUIZ F.L.; MADUAR, MARCELO F.; ALENCAR, MARCOS M.
A operação normal de uma instalação nuclear ou radiativa envolve a liberação de efluentes radioativos líquidos e/ou gasosos. No Instituto de Pesquisas Energéticas e Nucleares (IPEN) existem diversas instalações nucleares e radiativas, desenvolvendo atividades no campo da física nuclear, radioquímica, engenharia nuclear, produção de radioisótopos e radio fármacos, aplicação de técnicas nucleares na indústria entre outras. A Gerência de Radioproteção do IPEN estabeleceu um programa de amostragem dos efluentes radioativos para determinar a quantidade de material radioativo (termo fonte) liberada para o meio ambiente e detectar imediatamente, qualquer liberação não planejada acima dos limites operacionais pré-estabelecidos. O controle radioativo dos efluentes gasosos e do ar atmosférico ambiental do Instituto foi implementado em 1988 e é realizado pelo Laboratório de Radiometria Ambiental – Centro de Metrologia das Radiações. No controle dos efluentes gasosos são analisados semanalmente, por espectrometria gama de alta resolução com detector de germânio hiperpuro, filtros de celulose e de carvão das instalações radioativas do IPEN, como o Centro do Reator de Pesquisas IEA-R1 e também o Centro de Aceleradores e Cíclotron e a Diretoria de Radiofarmácia – Prédio I e II. Desde a operação do controle dos efluentes gasosos há trinta anos, mais de 3000 filtros foram analisados e os radionuclídeos determinados na maioria das amostras durante esse período de amostragem no Centro do Reator de Pesquisas IEA-R1 foram 131I e 123I. Os resultados obtidos das análises dos filtros do controle dos efluentes gasosos são publicados em relatório de avaliação periódica e disponibilizados internamente via intranet. Todos os resultados obtidos, de 1988 a 2018, confirmam que a liberação de efluentes gasosos radioativos da operação normal das instalações nucleares e radioativas do IPEN está sendo adequadamente controlada e que o impacto radiológico causado por essa liberação é insignificante quando comparado aos limites recomendados pela regulamentação atual da CNEN de 2005.
16 anos de resultados de determinação de radionuclídeos emissores gama na água da piscina do reator IEA-R1
2022 - MADUAR, MARCELO F.; ALENCAR, MARCOS M. de; TEIXEIRA, LUIZ F.L.; NISTI, MARCELO B.
A avaliação dos parâmetros técnicos na operação do Reator de Pesquisas IEA-R1, em particular as características físico-químicos da água da piscina do IEA-R1, é parte integrante das atividades coordenadas pelo CRPq (Centro do Reator de Pesquisas) do IPEN. O Serviço de Gestão de Radiometria Ambiental realiza desde meados de 2003 a análise rotineira por espectrometria gama em amostras da água da piscina do IEA-R1. Os radionuclídeos usualmente detectados são: Ag-110m, Co-58, Co-60, Cr-51, I-131, Mn-54, Na-24, Np-239, Te- 132, W-187 e Zn-65. Alguns nuclídeos são detectados raramente, como Cs-137, Ba-140/ La-140 e Ru-103. O radionuclídeo que apresenta regularmente a maior atividade é Na-24, com concentrações na faixa de 100 a 150 kBq/L, corrigida para o horário de desligamento do IEA-R1. Outros apresentam radioatividade da ordem de 102 a 103 Bq/L (Ag-110m, Co-58, Co-60, Cr-51 e W-187) e os restantes, poucos Bq/L. A principal conclusão, ao longo do tempo, é que o tempo de espera após o desligamento e coleta das amostras é o fator fundamental na definição de quais radionuclídeos são e quais não são passíveis de quantificação radiométrica. As medidas realizadas entre cinco e sete dias após o desligamento do reator fornecem um compromisso ótimo na detecção de nuclídeos de meia-vida inferior a um dia e limites de detecção aceitáveis para nuclídeos de meia-vida superior a dez dias.
Counting efficiency in gamma ray spectrometry with different volumes for the same geometry
2021 - NISTI, M.B.; MADUAR, M.F.; DAMATTO, S.R.; ALENCAR, M.M.
An overview of the gaseous radioactive effluents control and radioactivity assessment in the atmospheric air at IPEN’S campus
2017 - RODRIGUES, C.E.C.; NOGUEIRA, P.R.; DAMATTO, S.R.; MADUAR, M.F.; ALENCAR, M.M.; PECEQUILO, B.R.S.
The routine operation of a nuclear or radioactive installation generally involves the release of radioactive liquid and/or gaseous effluents. At the Nuclear and Energy Research Institute – IPEN there are several nuclear and radioactive facilities, developing activities in the field of nuclear energy. IPEN’s Radioprotection Management has established a radioactive effluent sampling program to determine the amount of radioactive material (source term) released into the environment and to detect immediately any unplanned release above the pre-established operating limits. The IPEN Environmental Radiological Monitoring Program – ERMP evaluates the levels of radioactivity to which individuals of the public are exposed through the analysis of atmospheric samples; the main objective of an ERMP is the confirmatory radiological control, which estimates whether the assumptions made in the calculation of the dose, from the source term, are correct. The objective of the present work is to present the gaseous radioactive effluents control and the radioactivity assessment in the atmospheric air at IPEN’s campus, since there were implanted in 1988 at the Laboratory of Environmental Radiometry of IPEN. In both, gaseous radioactive effluents control and radioactivity assessment in the atmospheric, cellulose and charcoal cartridge filters are analyzed by gamma spectrometry – HPGe weekly, from the IPEN’s radioactive facilities, Accelerators and Cyclotron Center, IEA-R1 Research Reactor Center, Radiopharmacy Center - Building I and II and each 15 days collected from three air samplers located near the nuclear and radiation facilities of IPEN, respectively. The radionuclides determined in the majority of the samples throughout the sampling period were 131I, 18F and 67Ga.
Soil-to-plant transfer factors for radionuclides in samples of lemon balm (Melissa officinalis) commonly used as a medicinal plant
2014 - SUSSA, FABIO V.; ALENCAR, MARCOS M. de; MAZZILLI, BARBARA P.; SILVA, PAULO S.C. da
Radiological characterization of the varieties burley and virginia of Nicotiana tabacum L. cultivated in Brazil
2014 - SILVA, CAROLINA F. da; DAMATTO, SANDRA R.; ROCHA, RIQUE J.F.X. da; ALENCAR, MARCOS M. de
Fast methodology for time counting optimization in gamma-ray spectrometry based on preset minimum detectable amounts
2008 - NISTI, M.B.; SANTOS, A.J.G.; PECEQUILO, B.R.S.; MADUAR, M.F.; ALENCAR, M.M.; DAMATTO, S.R.
Determination of U and Th isotopes in lichen samples of Canoparmelia texana
2008 - ALENCAR, MARCOS M. de; MAZZILLI, BARBARA P.; SILVA, PAULO S.C. da