GUILHERME SOARES ZAHN

GUILHERME SOARES ZAHN

(Fonte: Lattes)

Resumo

Has a bachelor's degree in Physics from Universidade de São Paulo (1991), master's at Nuclear Engineering from Universidade de São Paulo (1994) and doctorate at Nuclear Engineering from Universidade de São Paulo (2006). Has experience in nuclear ans applied physics, focusing on nuclear structure, acting on the following subjects: beta decay, neutron activation, gamma spectroscopy, nuclear structure, neutron flux determination and detection, and also on the development od instrumentation and sotware aimed at nuclear applications. (Text obtained from the Currículo Lattes on October 14th 2021)

Possui graduação em Física pela Universidade de São Paulo (1991), mestrado em Tecnologia Nuclear pela Universidade de São Paulo (1994) e doutorado em Tecnologia Nuclear pela Universidade de São Paulo (2006). Atualmente é pesquisador da Comissão Nacional de Energia Nuclear, lotado no Centro do Reator de Pesquisas do Instituto de Pesquisas Energéticas e Nucleares. Tem experiência na área de Física Nuclear, com ênfase em Estrutura Nuclear, atuando principalmente nos seguintes temas: decaimento beta, detecção de nêutrons, irradiadores de nêutrons, ativação neutrônica, fluxo de nêutrons, desenvolvimento de instrumentação e de software para aplicações nucleares. (Texto extraído do Currículo Lattes em 14 out. 2021)

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Examination of Natural Radioactivity Concentration and Radiological Exposure of Soil Within Mining Site in Umuahia South Abia State Nigeria, Using High Purity Germanium (HPGe) Gamma Ray Spectrometry
2023 - ONUDIBIA, MOSES E.; SILVA, PAULO S.C. da; ESSIETT, ANIESUA A.; ZAHN, GUILHERME S.; GENEZINI, FREDERICO A.; IMEH, EDET E.; NNAMANI, NGENE C.; OGODO, ALLOYSIUS C.; MFOM, CELESTIAL B.; OKOH, FRANCA O.
Mining activity is one of the major sources of exposure to radiation. The main goal of this study was to determine the natural radioactivity level and its radiological exposure risk in mining site Umuahia South Abia State, Nigeria, using High Purity Germanium (HPGe) gamma ray spectrometry. The activity concentration of 40K, 226Ra and 232Th in the soil ranges from 31±2 to 367±27 Bq kg-1, with mean value of 142±11 Bq kg-1; from 26±2 to 65±5 Bq kg-1, with mean value of 49±4; and from 53±9 to 109±17 Bq kg-1, with mean value of 77±16 Bq kg-1, respectively. The activity concentrations of 226Ra and 232Th are above the global values of 32 and 45 Bq kg-1 while 40K is depleted in relation to the global mean of 412 Bq kg-1. Radiological parameters are generally in agreement with the values observed for other Nigerian and other countries soil reported in literature. The main responsible for the values observed for the radiological parameters is 232Th followed by 226Ra. The use of this soil for dwelling construction is unlikely to pose any radiological harm for the residents.
Application of a semi-empirical model for the evaluation of radium activity in phosphogypsum used as component of clinker
2021 - GERALDO, R.R.; PASCHUK, S.A.; BARRETO, R.C.; CORREA, J.N.; ZAHN, G.S.; SILVA, P.S.C. da; SILVA, A.M. da; NARLOCH, D.C.; ARAUJO, I.C.
Phosphogypsum is a residue that has been used by the cement industry as a substitute for the natural gypsum, used as a clinker additive during the production of Portland cement. There is a potential increase in this residue consumption since large amounts of phosphogypsum are generated as outcome of the phosphate fertilizer industries. However, phosphogypsum can be considered a source of radioactive contamination due to the presence of 226Ra in its composition. Depending on the concentration of 226Ra, from the radiological protection point of view, this may cause a problem because this radionuclide and its direct decay product 222Rn along with other decay products, represent the largest fraction of radiation internal dose received by people. In order to evaluate the level of radiological risk that may be associated with the use of phosphogypsum, it is necessary to identify the concentration of 226Ra in building materials. The aim of this research is to analyze samples of phosphogypsum in relation to the concentrations of 226Ra, determined indirectly through 222Rn activity measurements. This measurement process has the advantage of being fast, convenient and relatively inexpensive when compared to traditional methods of 226Ra concentration in samples measurements. The proposed physical-mathematical model was used to establish radium concentration from radon exhalation rate from cement mortar samples. The 222Rn activity measurements were performed with a portable detector with cubic phosphate samples with 50 mm edges each placed in a closed atmosphere of the sampling chamber until secular equilibrium is achieved. Obtained concentrations of radium activity in studied samples of phosphogypsum and cement mortars were found below the limits recommended by CNEN and international regulation.
On the feasibility of producing Lu-177 in the IEA-R1 reactor via the direct route
2021 - ZAHN, G.S.; GENEZINI, F.A.; SILVA, P.S.C.; NORY, R.M.; MOREIRA, E.G.; SANTIAGO, P.S.
Over the last years the 177Lu radioisotope has attracted great interest for the use in therapeutic and diagnostic procedures simultaneously, being what is now called a theranostic radioisotope, with outstanding results in prostate and neuroendocrine cancer. There are mainly two ways of producing this radioisotope, by direct neutron capture in a 176Lu target (the “direct route") or by irradiating a 176Yb sample, producing 177Yb that will then decay to 177Lu (also referred as the “indirect route”). In this work, the technical feasibility of producing 177Lu in the IEA-R1 nuclear research reactor via the direct route was assessed, and the specific activity that could be obtained was estimated both experimentally and theoretically.
Natural and artificial nuclides in Salesópolis reservoir
2019 - SILVA, P.S.C.; SEMMLER, R.; ZAHN, G.S.; ROCHA, F.R.; DAMATTO, S.R.; FAVARO, D.I.T.
Natural radioactivity is ubiquitous in the environment mainly due to the presence of the nuclides from the ura-nium and thorium series and 40K. Although in the South Hemisphere nuclear tests have been fewer in number than that in the North, artificial radionuclides can also be found spread at ground level. In this study, the activity concentrations of natural nuclides from the uranium and thorium series, 40K and the artificial 137Cs were deter-mined in a sediment core with 42 cm depth collected in the middle of the Salesópolis reservoir, located in the Metropolitan Region of São Paulo city (SPMR). The Usina Parque Rio Tietê reservoir belongs to the Alto do Tietê system for the capture, storage and treatment of water for SPMR. Therefore, the quality of the water and sediments of this dam is of great importance. The activity concentrations were measured by gamma spectrome-try. Samples were measured and saved at regular intervals at a maximum of 160 000 seconds. The gross area were determined for each peak and plotted against time and the counting rate was obtained by the slope of the curve. Background and reference materials were also counted and treated in the same way. Results showed that 226Ra varied from 45 to 116 Bq kg-1; 228Ra, from 80 to 165 Bq kg-1; 40K, from 155 to 1 187 Bq kg-1 and 137Cs varied from 0.3 to 7 Bq kg-1. The methodology applied for determining low levels of 137Cs in sediment proved to be effi-cient and reproducible.
Neutron activation analysis applied in sediment samples from the Guarapiranga reservoir for metals and trace elements assessment
2012 - GUIMARAES, GUILHERME M.; ZAHN, GUILHERME S.; FRANKLIN, ROBSON L.; SILVA, PAULO S.C.; FAVARO, DEBORAH I.T.