MARCOS MEDRADO DE ALENCAR

MARCOS MEDRADO DE ALENCAR

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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.
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.