Navegação por autor "950"

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  • IPEN-DOC 25903

    ZAHN, G.S. ; GENEZINI, F.A. ; RIBEIRO JUNIOR, I. . AnalisaCAEN, a simple software suite to reduce and analyze coincidence data collected using CAEN v1724 digitizer. Journal of Physics: Conference Series, v. 1291, p. 1-3, 2019. DOI: 10.1088/1742-6596/1291/1/012044

    Abstract: In this work a small software suite for the reduction and analysis of coincidence data collected using CAEN’s proprietary software was developed. These software check the output files for coincidences, generate a single list mode file with the coincident events, build histograms for each input, plus a time difference histogram and a 2-detector data matrix, perform time gates and allows for the subtraction of accidental coincidences, and perform energy gating on the final data matrices, generating histograms with the gated spectra. Moreover, the suite has an integrator that guides the user through all the required steps.

    Palavras-Chave: programming languages; computer codes; data processing; digital systems; digitizers; coincidence methods

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  • IPEN-DOC 28703

    ZAHN, GUILHERME S. ; TICIANELLI, REGINA B. ; SILVA, PAULO S.C. da ; GENEZINI, FREDERICO A. . Análise dos radionuclídeos encontrados na água do reator IEA-R1. In: SILVA, PAULO S.C. da (Org.); ZAHN, GUILHERME S. (Org.); SOUZA, FRANCISCO de A. (Org.). Contribuições do reator IEA-R1 para a pesquisa nuclear. São Paulo, SP: Blucher, 2022. p. 39-45, cap. 3. DOI: 10.5151/9786555501483-03

    Abstract: O reator IEA-R1 é do tipo piscina aberta, construído nos anos 1950. Nos últimos anos, ele opera a 4,5MW por oito horas às segundas, terças e quartas. Em todo dia de operação, duas amostras da água do reator são retiradas, uma antes de o reator ser ligado pela manhã e outra em torno das 16h, próximo ao final as operação. Essas amostras são contadas em um detector HPGe por 1500 s para verificar possíveis problemas com os elementos combustíveis, entre outros. Neste trabalho, os resultados obtidos nessas análises ao longo de alguns meses de 2019 são discutidos em termos dos radionuclídeos encontrados, bem como da dependência da sua atividade com o tempo.

    Palavras-Chave: radioisotopes; radioactivity; cooling ponds; water

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  • IPEN-DOC 28710

    ZAHN, GUILHERME S. ; GENEZINI, FREDERICO A. ; RIBEIRO JUNIOR, IBERE S. . Aplicação de técnicas de coincidência gama-gama no LFNA-CRPQ. In: SILVA, PAULO S.C. da (Org.); ZAHN, GUILHERME S. (Org.); SOUZA, FRANCISCO de A. (Org.). Contribuições do reator IEA-R1 para a pesquisa nuclear. São Paulo, SP: Blucher, 2022. p. 99-104, cap. 10. DOI: 10.5151/9786555501483-10

    Abstract: As técnicas de coincidência γ−γ consistem no uso de mais de um detector para registrar a radiação proveniente de alguma amostra, registrando-se apenas os eventosem que fótons foram registrados em mais de um detector. Essa técnica foi trazida ao Laboratório de Física Nuclear Aplicada (LFNA-CRPq) em decorrência da experiência em trabalhos anteriores em estrutura nuclear, e permite uma redução significativa no BG dos espectros, bem como nas interferências espectrais encontradas. Neste trabalho será apresentada uma pequena introdução ao uso da técnica, bem como o estado atual de sua implementação no LFNA-CRPq, possíveis aplicações e perspectivas futuras.

    Palavras-Chave: coincidence methods; coincidence spectrometry; radiation detectors; nuclear physics

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  • IPEN-DOC 27903

    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.. Application of a semi-empirical model for the evaluation of radium activity in phosphogypsum used as component of clinker. Brazilian Journal of Radiation Sciences, v. 9, n. 1A, p. 1-15, 2021. DOI: 10.15392/bjrs.v9i1A.1518

    Abstract: 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.

    Palavras-Chave: building materials; concentration ratio; exhalation; gypsum cements; phosphates; radiation detectors; radiation protection; radioactivity; radium 226; radon 222

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  • IPEN-DOC 26415

    ZAHN, GUILHERME S. ; JUNQUEIRA, LUCAS S. ; GENEZINI, FREDERICO A. . CAX and Xsel: a software bundle to aid in automating NAA spectrum analysis. Brazilian Journal of Radiation Sciences, v. 7, n. 2A, p. 1-7, 2019. DOI: 10.15392/bjrs.v7i2A.565

    Abstract: In this work, the scripting capabilities of Genie-2000 were used to develop a software (CAX) that automatically anal-yses all spectrum files in either ORTEC's CHN or CANBERRA's MCA or CNF formats in a folder, generating two output files: a print-ready text file (.DAT) and a Comma-Separated Values (.CSV) file which can be easily imported in any major spreadsheet software. A second tool, named Xsel, consists in an EXCEL spreadsheet which automatically identifies the spectrum lines associated with the elements of interest, generating a clean output sheet which can be easily imported in a general spreadsheet that calculates the concentrations; an important addition to this spreadsheet is the ability to automatically recalibrate each spectrum, increasing the reliability of the peak identification procedure. These software tools are already used in daily routines at IPEN's Neutron Activation Laboratory, greatly reducing the time required for sample analyses, as well as reducing the possibility of transcription errors.

    Palavras-Chave: automation; neutron activation analysis; gamma radiation; gamma spectra; computer codes; calibration; performance; brazilian cnen; data processing

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  • IPEN-DOC 26964

    GENEZINI, FREDERICO A. ; ZAHN, GUILHERME S. ; MORALLES, MAURICIO ; MOREIRA, EDSON G. . Celebrating IEA-R1 first criticality. In: BRAZILIAN MEETING ON NUCLEAR PHYSICS, 40th, September 3-7, 2017, Campos do Jordão, SP. Abstract... São Paulo, SP: Sociedade Brasileira de Física, 2017. p. 1-1.

    Abstract: Early in 1956 USP and CNPq established a cooperation agreement and in the middle of the same year, the Atomic Energy Institute (IEA) was founded. Its primary task was to install the research nuclear reactor purchased from the American company Babcock & Wilcox in the context of the “Atoms for Peace” Program. Another major task was to train reactor operators and users of the new facility. The first start-up was in September 16, 1957, being the first criticality achieved in the Southern hemisphere. IEA-R1 is a pool type, light water cooled and moderated, graphite reflected research reactor. Although designed to operate continuously up to 5 MW, it operated at 2 MW power during 40 years and afterwards it has been operating at 5MW. IEA R1 has several uses, such as radioactive isotope production by neutron flux irradiation up to 10(14)cm(-2)s(-1), for health and industry applications; research and development using radioactive samples and neutron beams (8 radial and 2 tangential beam ports). This year we celebrate the 60th anniversary of the first criticality of the IEA-R1 research reactor and due to a continuous modernization program, it is expected to operate for another long time period.

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  • IPEN-DOC 26847

    COSTA, PRISCILA ; RAELE, MARCUS P. ; DOMIENIKAN, CLAUDIO ; COSTA, FABIO E. ; MADI FILHO, TUFIC ; ZAHN, GUILHERME S. ; GENEZINI, FREDERICO A. . A compact electronic system for a photodiode neutron detector. In: JAKSIC, ALEKSANDAR (Ed.); KARAMARKOVIC, JUGOSLAV (Ed.) INTERNATIONAL CONFERENCE ON RADIATION APPLICATIONS, September 16-19, 2019, Belgrade, Serbia. Abstract... Niš, Serbia: Sievert Association, 2019. p. 36-36.

    Abstract: The demand for portable neutron detectors is on the rise, and for that purpose, low cost boron-10 has been frequently used instead of helium-3, which is usually employed in large and expensive detectors. Portable detectors are of interest in some applications, such as neutron dosimeters or inspection systems targeted in the detection of fissile material and drugs in airports. In this work a portable thermal neutron detection system was developed which is based on a commercial silicon photodiode coupled to a boron converter; this prototype is then plugged into a portable electronic system. The boron layer was produced by pulsed laser deposition, either on a thin glass slide or on the photodiode itself. The boron deposition in the photodiode was made directly in the active area of the detector, so before and after the deposition process a characterization of the device regarding both the dark current and the operation voltage was performed using an americium source. Finally, both configurations were tested. The neutron detection process occurs by detecting the alpha and lithium particles produced by the interaction of the incoming neutron with the boron-10 nuclides. These heavy ions then interact with the active area of the reverse-biased photodiode, producing an electric signal that has to be preamplified and then properly amplified by the portable electronic system, which in turn produces an output that can either be sent to a multichannel analyzer or to a digital counter. The integrated circuit of the low noise preamplifier transforms the detector’s current pulse into a voltage pulse with amplitude proportional to the charge carried by the current pulse. The shaper-driver consists of a differentiator and an integrator and is responsible for filtering and further amplifying the preamplifier signal, generating a NIM-compatible energy output pulse. The performance of the photodiode-amplifier set for alpha particles was successively tested using a 243Am radioactive source. Initial tests were made using the boron-deposited glass, and the electronic signal was properly read. However, when the same system was tested using the boron deposited directly in the photodiode, the output signal couldn’t be read, due to the fact that during the deposition process there was an increase in the dark current and a decrease in the operation bias. In this way, a new portable electronic system was developed using a hybrid integrated amplifier circuit. This new electronic setup allowed the use of both configurations, and was tested both with alpha-emitting Americium and neutron-emitting AmBe sources. In conclusion, both portable electronic systems have proven suitable for the thermal neutron detector developed.

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  • IPEN-DOC 27908

    RIBEIRO JUNIOR, I.S. ; GENEZINI, F.A. ; ZAHN, G.S. . Comparison of two methodologies for spectra analysis in coincidence neutron activation analysis. Brazilian Journal of Radiation Sciences, v. 9, n. 1A, p. 1-12, 2021. DOI: 10.15392/bjrs.v9i1A.1540

    Abstract: The Research Reactor Center (CERPq) of IPEN-CNEN/SP has been developing a facility for Coincidence Neutron Activation Analysis (CNAA), a variation of the Neutron Activation Analysis technique in which gamma-gamma coincidence is used to reduce spectral interferences and improve detection limits of some elements. As the acquisition results in 2D-coincidence spectra, the spectrum analysis has to be dealt with accordingly. There are two distinct ways to perform these analyses, either directly, by fitting bidimensional peaks in the coincidence matrix, or by gating the spectra in one detector around each peak of interest and fitting the resulting 1D-spectrum in the usual way. In this work, the concentrations of As, Co, Cs, Sb and Se were determined in geological and biological reference materials by CNAA using two different methodologies of analysis, using the BIDIM software, which provides 2D-peak-fitting; and a combination of the AnalisaCAEN suite, which gates the 2D-spectra, with Canberra’s Genie2000, which fits the resulting unidimensional spectra. The outcomes allow for a discussion of the advantages and shortcomings of each method, both in terms of usability and of the reliability of the results.

    Palavras-Chave: neutron activation analysis; concentration ratio; geology; comparative evaluations; calibration standards; irradiation; neutron flux; spectra

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  • IPEN-DOC 28739

    RIBEIRO JUNIOR, IBERE S. ; GENEZINI, FREDERICO A. ; ZAHN, GUILHERME S. . Determinação de Sm por análise por ativação neutrônica em amostras geológicas: de arriscada a trabalhosa. In: SILVA, PAULO S.C. da (Org.); ZAHN, GUILHERME S. (Org.); SOUZA, FRANCISCO de A. (Org.). Contribuições do reator IEA-R1 para a pesquisa nuclear. São Paulo, SP: Blucher, 2022. p. 387-395, cap. 40. DOI: 10.5151/9786555501483-40

    Abstract: Nesse trabalho foi desenvolvido um método alternativo para determinação do fator de interferência do 153Sm como uma função do tempo de decaimento em virtude de interferência espectral de raios-X do 239Pu. Para realizar esse estudo foram irradiados dezoito padrões sintéticos de Sm e U no reator IEA-R1. Os fatores de interferência foram determinados experimentalmente para diferentes tempos de decaimento afim de ajustar uma função/curva teórica para os dados experimentais. Ao final será introduzido uma nova possibilidade de determinação do fator de interferência para o 153Sm utilizando medidas em coincidência gama-gama que apresenta a possibilidade de eliminar as interferências dos raios-X do 239Pu.

    Palavras-Chave: samarium 153; neutron activation analysis; geologic surveys; fission; uranium

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  • IPEN-DOC 28206

    RIBEIRO JUNIOR, I.S. ; GENEZINI, F.A. ; SILVA, P.S.C. da ; ANGELINI, M. ; JUNQUEIRA, L.S. ; ZAHN, G.S. . Determination of scale factor for Ni-59 and Ag-108m in ion exchange resin from Angra 1. In: INTERNATIONAL NUCLEAR ATLANTIC CONFERENCE, November 29 - December 2, 2021, Online. Proceedings... Rio de Janeiro: Associação Brasileira de Energia Nuclear, 2021.

    Palavras-Chave: ion exchange; isotope separation; nickel 59; silver 108; radioactive waste management; gamma spectroscopy; angra-1 reactor

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  • IPEN-DOC 27883

    MELO, G.R.; ZAHN, G.S. ; GENEZINI, F.A. ; MOREIRA, E.G. . Development of an environmental monitoring station for HPGe detectors. Brazilian Journal of Radiation Sciences, v. 9, n. 1A, p. 1-14, 2021. DOI: 10.15392/bjrs.v9i1A.1412

    Abstract: Neutron Activation Analysis (NAA) is a well-established nondestructive analytic technique where the gamma radiation emitted by an irradiated sample is analyzed using an HPGe detector. The Neutron Activation Laboratory (LAN) of IPEN-CNEN/SP has been performing NAA analyses for over 30 years, and has plans of implementing quality control protocols to their analyses. In this sense, the environmental monitoring of the laboratories where the detectors are used has been performed for many years, in a manual way with no more than 2 measurements per day. In this work, an automated monitoring station based on a microcontroller ArduinoUNO board has been developed which comprises four thermo hygrometer sensors for monitoring different parts of the environment, plus a thermocouple for monitoring the inside of the liquid nitrogen dewar. The results obtained allow for a discussion on the performance and adequacy of the sensors.

    Palavras-Chave: automation; environment; high-purity ge detectors; monitoring; neutron activation analysis; performance; sensors; thermocouples; uses

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  • IPEN-DOC 26197

    ZAHN, GUILHERME S. ; GENEZINI, FREDERICO A. . Efficiency stability of HPGe detectors under distinct count rates. In: INTERNATIONAL NUCLEAR ATLANTIC CONFERENCE, October 21-25, 2019, Santos, SP. Proceedings... Rio de Janeiro: Associação Brasileira de Energia Nuclear, 2019. p. 1092-1096.

    Abstract: In this work the reproducibility of the e ciency of di erent HPGe detectors was analyzed under a series of di erent conditions. The detectors studied were plugged either to a regular analogical ampli er or to a digital signal processing (DSP) device, in order to evaluate the possible di erences between either setup. Detectors were inspected by performing a long series of sequential measurements with standard calibration sources, and comparing the standard deviation of the number of counts per second in each series to the uncertainty of the individual measurements. Detectors were also subjected to distinct count rates, in order to verify the possible experimental issues associated with this parameter. The results allow a discussion on the stability of the detectors' e ciencies over a few days, the possible dependence with the count rate, and the estimation of the uncertainty related to the e ciency variation.

    Palavras-Chave: calibration standards; comparative evaluations; data covariances; efficiency; high-purity ge detectors; stability

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  • IPEN-DOC 27881

    ZAHN, G.S. ; GENEZINI, F.A. . Efficiency stability of HPGe detectors under distinct count rates. Brazilian Journal of Radiation Sciences, v. 9, n. 1A, p. 1-8, 2021. DOI: 10.15392/bjrs.v9i1A.1410

    Abstract: In this work the reproducibility of the efficiency of different HPGe detectors was analyzed under a series of different conditions. The detectors studied were plugged either to a regular analogical amplifier or to a digital signal processing (DSP) device, to evaluate the possible differences between either setup. Detectors were inspected by performing a long series of sequential measurements with standard calibration sources and comparing the standard deviation of the number of counts per second in each series to the uncertainty of the individual measurements. Detectors were also subjected to distinct count rates, to verify the possible experimental issues associated with this parameter. The results allow a discussion on the stability of the detectors’ efficiencies over a few days, the possible dependence with the count rate, and the estimation of the uncertainty related to the efficiency variation.

    Palavras-Chave: calibration standards; comparative evaluations; counting ratemeters; data covariances; efficiency; high-purity ge detectors; stability

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  • IPEN-DOC 29843

    MEDEIROS, JOSE A.G. de ; MORALLES, MAURICIO ; SILVA JUNIOR, IREMAR A. da ; YORIYAZ, HELIO ; ZAHN, GUILHERME ; GENEZINI, FREDERICO A. ; SOUZA, FRANCISCO A. . Espectrometria gama dos Geradores de Vapor e da Tampa do Vaso do Reator depositados no DIGV (medidas preliminares). São Paulo: Instituto de Pesquisas Energéticas e Nucleares - CEENG, Novembro, 2023. (IPEN-CEN-P&D-ETN-218-01-RELT-009-00). Restrito.

    Título do projeto: Composição Isotópica dos Rejeitos Radioativos da CNAAA

    Abstract: Este documento tem como objetivo apresentar os resultados das medidas preliminares de espectrometria gama dos Geradores de Vapor (GVs) e da Tampa do Vaso do Reator (TVR), realizadas entre os dias 02 e 10 de fevereiro de 2023. Estes equipamentos foram removidos de Angra 1 em 2009 e 2013, respectivamente, e se encontram no Depósito Inicial dos Geradores de Vapor (DIGV) no sítio da Central Nuclear Almirante Álvaro Alberto (CNAAA). As medidas de espectrometria gama buscam possibilitar a avaliação do inventário dos radionuclídeos gama emissores presentes nestas estruturas, mais particularmente daqueles a serem utilizados como radionuclídeos chaves na proposição das razões de concentração de atividade. O inventário dos radionuclídeos chaves, associado aos dados das razões de concentração de atividade de outros radionuclídeos presentes em amostras representativas dos GVs e da TVR, possibilitará a proposição de um inventário radioisotópico estendido dessas estruturas. Este documento apresenta também a medida de mapeamento dosimétrico dos GVs. Essa atividade visa a apresentação de informações complementares àquelas disponibilizadas pela atividade de espectrometria gama na avaliação do inventário dos radionuclídeos gama emissores. A apresentação deste documento atende o item 8.4.2 do Plano de Trabalho, que inclui a "Realização e apresentação dos resultados de espectrometria gama dos Geradores de Vapor e da Tampa do Vaso do Reator" do Acordo de Pesquisa e Desenvolvimento (Ativo Isotópico - Fase B) ,celebrado entre a Eletronuclear (ETN) e o Instituto de Pesquisas Energéticas e Nucleares (IPEN-CNEN/SP).

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  • IPEN-DOC 26795

    ZAHN, GUILHERME S. ; GENEZINI, FREDERICO A. ; MORALLES, MAURICIO . Evaluation of peak-fitting software for gamma spectrum analysis. In: REUNIÃO DE TRABALHO SOBRE FÍSICA NUCLEAR NO BRASIL, 42.; ENCONTRO NACIONAL DE FÍSICA DE PARTÍCULAS E CAMPOS, 40., 1-5 de setembro, 2019, Campos do Jordão, SP. Resumo... São Paulo, SP: Sociedade Brasileira de Física, 2019.

    Abstract: In all applications of gamma-ray spectroscopy, one of the most important and delicate parts of the data analysis is the fitting of the gamma-ray spectra, where information as the number of counts, the position of the centroid and the width, for instance, are associated with each peak of each spectrum. Theres a huge choice of computer programs that perform this type of analysis, and the most commonly used in routine work are the ones that automatically locate and fit the peaks; this fit can be performed in several different ways - the most common are either to fit a Gaussian function to each peak or simply to integrate the area under the peak, but some software go far beyond and include several small corrections to the simple Gaussian peak function, in order to compensate for secondary effects. In this work several gamma-ray spectroscopy software are compared in the task of finding and fitting the gamma-ray peaks in spectra taken with some calibrated standard sources. The results allow for a discussion on the performance of each software in the tasks of identifying and determining the correct area of the gamma-ray peaks, as well as on the advantages and difficulties in using automatic programs when comparing with a manual peak-fitting software, used as reference.

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  • IPEN-DOC 26813

    CORREA, J.N.; PASCHUK, S.A.; BARRETO, R.C.; DENYAK, V.; SCHELIN, H.R.; NARLOCH, D.C.; DEL CLARO, F.; HASHIMOTO, Y.; MATIN, A.C.; SILVA, A.C.M.; ZAHN, G.S. ; SILVA, P.S.C. . Evaluation of the maximum emitting layer of Rn-222 in cementitious building materials. In: INTERNATIONAL CONFERENCE ON DOSIMETRY AND ITS APPLICATIONS, 3rd, May 27-31, 2019, Lisboa, Portugal. Abstract... Lisboa, Portugal: C2TN, Instituto Superior Técnico, Universidade de Lisboa, 2019.

    Abstract: Introduction – Radionuclides present in construction materials are of interest in the view of environmental radioactivity. The limitations established have focused on the concentration of Ra-226 and the consequent exhalation of Rn-222. A physical/mathematical model developed at the Laboratory of Applied Nuclear Physics (LFNA/UTFPR) correlates the exhaled Rn-222 with the Ra-226 inherent to the material. The model considers the exhalation of Rn-222 by a plane surface that simulates exhalation in fl oors, walls and ceilings. Determination of the maximum emitting layer of Rn-222 that effectively exhales is important to support the model. The objective of this research is to determine the maximum emissive layer of Rn-222 that provides internal diffusion and exhalation of radon-222 in cementitious materials. Methods - Cylindrical samples were made of common cement paste and cement paste with sand of high Ra-226 concentration. The samples (thicknesses 1 to 5 cm) were sealed in order to ensure the exhalation of Rn-222 through one surface. Samples and diffusion chambers containing CR-39 solid-state detectors were inserted into a glass vessel. The samples/detectors were stored for 30 days. Subsequently, the detectors were chemically etched and the nuclear tracks in the CR-39 detectors were counted. Results – For each type of sample a curve was fi tted whose threshold indicated the maximum emitting layer. The results obtained on the samples of common cement paste indicated a maximum emitting layer of 2cm. For samples of cement paste with sand with high Ra-226 concentration, no threshold was observed, indicating that the maximum emitting layer is greater than 5cm. Conclusions - The maximum emitting layer thickness of Rn-222 of common materials determined by curve fi tting was 2cm. For materials with high concentration of Ra-226 there is an indication that the emitter layer is larger than 5cm. The obtained results subsidize the physical/mathematical model developed in the LFNA/UTFPR.

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  • IPEN-DOC 25771

    ZAHN, G.S. ; TICIANELLI, R.B. ; SAIKI, M. ; GENEZINI, F.A. . Evaluation of the uncertainty associated with sample holders in NAA measurements in LAN/IPEN. Brazilian Journal of Radiation Sciences, v. 7, n. 2A, p. 1-8, 2019. DOI: 10.15392/bjrs.v7i2A.676

    Abstract: In IPEN’s Neutron Activation Laboratory (LAN/IPEN), thin stainless steel sample holders are used for gamma spec-trometry in NAA measurements. This material is very practical, but its chemical composition may be troublesome, as it presents large amounts of elements with intermediate atomic number, with attenuation factors for low-energy gamma-rays that must not be neglected. In this study, count rates obtained using different sample holders were compared. To accomplish that, an Am-241 source, with 59-keV gamma emission, was used so that low-energy gamma attenuation differences can be determined. Moreover, in order to study the energy dependence of these differences, a Ho-166m source was also used. From these results, it was possible to analyze the experimental error associated to the variations between sample holders, with the aim of introducing an addictive term to the uncertainty analysis of comparative Neu-tron Activation Analysis results.

    Palavras-Chave: neutron activation analysis; stainless steels; americium 241; holmium 166; counting rates; sample holders; data covariances; gamma spectroscopy; comparative evaluations; energy dependence; brazilian cnen

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  • IPEN-DOC 29896

    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.. 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. Journal of Radiation and Nuclear Applications, v. 8, n. 3, p. 215-223, 2023. DOI: 10.18576/jrna/080304

    Abstract: 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.

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  • IPEN-DOC 25908

    SILVA, PAULO S.C. da ; ZAHN, GUILHERME S. ; CARVALHO, RICARDO N. de ; GENEZINI, FREDERICO A. . Gamma ray spectroscopy studies on low and intermediate level radioactive waste from Angra-1 nuclear power plant. In: BRAZILIAN MEETING ON NUCLEAR PHYSICS, 41th, September 2-6, 2018, Maresias, SP. Abstract... São Paulo: Sociedade Brasileira de Física, 2018. p. 1-1.

    Abstract: The determination of the radionuclide composition of low - and intermediate - level radioactive waste is of paramount importance for the design and implementation of Brazil`s planned radioactive waste repository. While there is some knowledge of the radionuclides expected to be present, the exact activity values in each of the waste bins are not determined with su±cient precision, so theres an ongoing e®ort to analyze the composition of this waste and make the radioactive inventory of the bins containt, which comprises several institutions and laboratories. In the present work the gamma - ray spectroscopy of samples of resin, ¯lters and evaporator concentrate from Angra 1 nuclear power plant have been studied. Small aliquots (» 500 mg) of the distinct samples were stored in glass vials and gamma- counted in a characterized high resolution germanium detector. In order to determine the best counting time, these aliquots were counted for 24h (real - time), with the spectroscopy results saved after each full hour of counting. The resulting twenty four spectra were then analyzed with Canberras Genie - 2000 software, using ISOCS e±ciency correction tool. The results for each sample were then compared to determine the required counting time for each of the radioisotopes of interest.

    Palavras-Chave: low-level radioactive wastes; gamma spectroscopy; nuclear power plants; angra-1 reactor; gasers; radioactive wastes; waste management

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  • IPEN-DOC 27065

    COSTA, PRISCILA ; RAELE, MARCUS P. ; YORIYAZ, HELIO ; ZAHN, GUILHERME S. ; GENEZINI, FREDERICO A. . Modelling a prototype of thermal neutron detector using a thin boron film and a photodiode. In: ENCONTRO DE FÍSICA; ENCONTRO NACIONAL DE FÍSICA DA MATÉRIA CONDENSADA, 39.; REUNIÃO DE TRABALHO SOBRE FÍSICA NUCLEAR NO BRASIL, 39.; ENCONTRO NACIONAL DE FÍSICA DE PARTÍCULAS E CAMPOS, 37.; ENCONTRO BRASILEIRO DE FÍSICA DOS PLASMAS, 13.; ENCONTRO DE PESQUISA EM ENSINO DE FÍSICA, 16., 3-7 de setembro, 2016, Natal, RN. Resumo... São Paulo, SP: Sociedade Brasileira de Física, 2016.

    Abstract: Neutron detection is an important task especially for worker protection in nuclear installations. For that purpose, it is desired to have portable and compact detectors, an aim which can be achieved using semiconductor detectors. In this work the Monte Carlo modelling of a neutron detector based on a thin boron film and photodiode is presented. The simulation was carried out using the MCNP6 code, in order to evaluate the detection efficiency for the alpha particles emitted in the boron neutron capture reaction. Two different setup subsets were modelled, taking into account the fact that the film could be deposited either in direct contact to the photodiode surface, or in indirect contact, where the film was deposited in a substrate (glass). In direct contact the thin film thickness ranged from 0 to 5 μm. For the indirect contact the thicknesses of the substrate and air region were varied. For both cases, the model was also prepared to consider the situation in which the film was sandwiched between two photodiodes in order to increase alpha particle detection efficiency. The results show that the thickness of the substrate, of 150 μm or 1000 μm, has a small influence on the alpha particle flux on the photodiode surface. The increase of the air region causes a decrease of 57 % in the flux of alpha particles in the photodiode. These different setups allowed determining the thickness values of thin boron film that delivers a higher alpha particle flux, which will lead to an optimum detection efficiency.

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