TALLYSON SARMENTO ALVARENGA

TALLYSON SARMENTO ALVARENGA

Página do item completo

Resultados de Busca

Agora exibindo 1 - 10 de 15

Estimation of scattered radiation influence on neutron beams at a calibration laboratory using Monte Carlo simulation of a long counter
2023 - ALVARENGA, T.S.; FERNANDES, S.S.; PEREIRA, W.W.; MAYHUGH, M.R.; CALDAS, L.V.E.
At the Neutron Calibration Laboratory (LCN) of IPEN/CNEN, a 241AmBe source was used to test and calibrate neutron detectors. The neutrons emitted by the source reach the detector as intended, but they also scatter undesirably from the building's floor, ceiling, and walls, leading to indirect detection. A Long Counter (LC) detector was modeled using the MCNPX Monte Carlo code. The objective of this study was to measure the contribution of scattered radiation at the LCN / IPEN, and to determine the fluence rate, at different points in the calibration room at source-to-detector distances of 100 cm and 150 cm; subsequently, the results were compared with those of the Brazilian Laboratory of Metrology of Ionizing Radiation (LNMRI). The results show that the fluence rates of LCN / IPEN are comparable to those of this neutron laboratory for the 100 and 150 cm source-to-detector distances using a 241AmBe source (37 GBq). The results show that the calibration of neutron detectors should be performed at distances less than 100 cm, where the contribution of scattered radiation is within the 40% limit recommended by ISO 8529-1.
Application of the Reduced-Fitting Method to determine neutron scattering
2021 - ALVARENGA, TALLYSON S.; POLO, IVON O.; PEREIRA, WALSAN W.; MAYHUGH, MICHAEL R.; CALDAS, LINDA V.E.
As the number of techniques using neutron radiation has grown, the number of neutrons detectors has increased along with need for their calibration. In Brazil this substantial demand for neutron detector calibration falls on a single laboratory located in Rio de Janeiro. One of the major problems in the calibration of neutron detectors is neutron scattering, which varies depending on the size and configuration of the laboratory. This is due to the neutrons that interact with the experimental setup and the surrounding, walls, floor and ceiling. This scatter influences the reading of the instrument to be calibrated and causes systematic errors in the calibration of neutron detectors. ISO 8529-2 recommends the following methods to correct these effects: The Semi-Empirical Method (SEM), the Reduced-Fitting Method (RFM), the Shadow-Cone Method (SCM) and the Generalized Fit Method (GFM). In this study, the neutron scattering characterization was performed in the Neutron Calibration Laboratory (LCN) of IPEN/CNEN, using the RFM method. The neutron source used was 241AmBe, which was positioned in the center of the calibration room. Neutron spectra were obtained using a scintillation detector based on 6Lil(Eu) in combination with a Bonner sphere spectrometer (BSS) at source-detector distances from 30 cm to 258 cm.
Use of Monte Carlo simulation and the Shadow-Cone Method to evaluate the neutron scattering correction at a calibration laboratory
2020 - ALVARENGA, TALLYSON S.; POLO, IVON O.; PEREIRA, WALSAN W.; CALDAS, LINDA V.E.
The calibration of radiation detectors is performed with the aim of ensuring accurate measurements of different types of radiation. Due to scattering neutrons, the neutron beam spectrum will not be the same spectrum as that emitted by the neutron source, thus influencing the reading of the instrument to be calibrated and causing a systematic error in the calibration of the neutron measurement devices. The objective of the present work was to estimate the contribution of scattering neutron radiation to fluence and mean energy using the Monte Carlo simulation and the Shadow-Cone Method with the objective of obtaining direct and scattering counting rates. The counting rates obtained at the Neutron Calibration Laboratory at IPEN, using the Bonner sphere spectrometer, were inserted into the NeuraLN program, which uses the UTA-4 response matrix and has 81 bins of energy used to determine the spectrum, fluence rate, and mean energy at the source-detector distances of 100 cm and 150 cm.
Contribution of the scattered radiation on the neutron beam fluence at the calibration laboratory of IPEN
2020 - ALVARENGA, TALLYSON S.; POLO, IVON O.; PEREIRA, WALSAN W.; SILVA, FELIPE S.; FONSECA, EVALDO S.; CALDAS, LINDA V.E.
In recent years, an upsurge in demand for neutron calibrations has been experienced in Brazil and several other countries in Latin America, mainly due to the increase in oil prospection and extraction procedures. The only laboratory for calibration of neutron detectors in Brazil is located at the Institute for Radioprotection and Dosimetry (IRD/CNEN), Rio de Janeiro. This laboratory is the national standard dosimetry laboratory in Brazil. With the increase in the demand for the calibration of neutron detectors, the need for more calibration services became evident. In this context, the Calibration Laboratory of IPEN/CNEN, São Paulo, which already offers calibration services of radiation detectors with standard X, gamma, beta and alpha beams, recently projected a new calibration laboratory for neutron detectors. One of the main problems in this kind of calibration laboratory is related to the knowledge of scattered radiation. In order to evaluate it, simulations were performed without the presence of the structural elements and with the complete room. Thirteen measurement points were evaluated at various distances. As part of the characterization process of the radiation fields of the new Neutron Calibration Laboratory, this work presents results on the influence of the radiation scattered by the structural components of the room: walls, doors, ceiling and floor, in different calibration positions, on the detector response. Therefore, the neutron radiation attenuation and the scattering parameters were determined at different source-detector distances, through computational simulation, using the MCNP5 Monte Carlo code.
Determination of the scattered radiation at the neutron calibration laboratory of IPEN using the Shadow Cone method
2019 - ALVARENGA, TALLYSON S.; FREITAS, BRUNO M.; FONSECA, EVALDO S.; PEREIRA, WALSAN W.; CALDAS, LINDA V.E.
Because of the increase in the demand for the calibration of neutron detectors, there is a need for new calibration services. In this context, the Calibration Laboratory of Instituto de Pesquisas Energéticas e Nucleares (IPEN), São Pau-lo, which already offers calibration services of radiation detectors with standard X, gamma, beta and alpha beams, has recently projected a new test laboratory for neutron detectors. This work evaluated the contribution of dispersed neutron radiation in this laboratory, using the Cone Shadow Method and a Bonner Sphere Spectrometer to take the measure-ments at a distance of 100 cm from the neutron source. The dosimetric quantities Ambient Dose Equivalent Rate (Ḣ*(10)) and Ambient Dose Equivalent Conversion Coefficient (h*(10)) were obtained at the laboratory, allowing the calibration of detectors.
Anisotropia da fonte de 241AmBe do laboratório de calibração com nêutrons do IPEN
2019 - ALVARENGA, T.S.; POLO, I.O.; PEREIRA, W.W.; CALDAS, L.V.E.
Contribution of the scattered radiation on the neutron beam fluence in the neutron calibration laboratory at IPEN
2018 - ALVARENGA, TALLYSON S.; POLO, IVON O.; PEREIRA, WALSAN P.; SILVA, FELIPE S.; FONSECA, EVALDO S.; CALDAS, LINDA V.E.
Estabelecimento e caracterização de um laboratório de calibração com campos neutrônicos de referência com rastreabilidade ao sistema metrológico internacional
2018 - ALVARENGA, TALLYSON S.
No Brasil, atualmente só há um laboratório de calibração de monitores de radiação de nêutrons, sendo responsável pela guarda e manutenção do padrão brasileiro da fluência de nêutrons, localizado no Laboratório Nacional de Metrologia das Radiações Ionizantes (LNMRI), Rio de Janeiro, no Instituto de Radioproteção e Dosimetria, Comissão Nacional de Energia Nuclear, Rio de Janeiro, com uma demanda grande de serviços com esse tipo de radiação. Com o intuito de descentralizar a oferta de serviços de calibração, surgiu a necessidade da montagem de um segundo Laboratório de Calibração com Nêutrons (LCN), no IPEN. Nas situações práticas envolvendo a calibração de monitores de radiação de nêutrons, um dos problemas principais está relacionado à radiação espalhada, que pode variar dependendo das dimensões do laboratório usado nos procedimentos de calibração. No processo de caracterização do campo de radiação de nêutrons da fonte de 241AmBe, onde foi realizada a avaliação dos espectros, das energias, das taxas de fluência, das taxas de equivalente de dose ambiente [H*(10)] e do coeficiente de conversão de fluência em dose [h*φ(10)] em diferentes posições do LCN, utilizando o feixe completo. A influência da radiação espalhada foi determinada por meio de três técnicas: Métodos de Monte Carlo, de Ajuste Reduzido e do Cone de Sombra. Dos resultados obtidos por meio de simulação e experimentalmente foi possível obter a fração de espalhamento em diferentes distâncias fonte-detector.
Estimativa computacional da radiação espalhada no laboratório de calibração com nêutrons do IPEN
2017 - ALVARENGA, T.S.; FEDERICO, C.A.; VALERIANO, C.C.; CALDAS, L.V.E.
Com o aumento do uso de técnicas que utilizam radiação de nêutrons, houve um crescimento considerável no número de detectores para esse tipo de radiação. Para ajudar a atender à demanda de calibração desse tipo de detector, foi proje-tado um laboratório de calibração de detectores com nêutrons, com fonte de 241AmBe. Neste tipo de laboratório, um dos problemas principais está relacionado ao conhecimento da radiação espalhada, que é significativa neste tipo de ativida-de. Com o intuito de estimar esta radiação espalhada de maneira a balizar a configuração final do laboratório, foram realizadas simulações computacionais utilizando-se o método de Monte Carlo por meio do código MCNP5. As simula-ções foram realizadas modelando o ambiente do laboratório sem a presença dos elementos estruturais e com a sala completa, de maneira a avaliar o fluxo de nêutrons e equivalente de dose ambiente, H*(10), em quatorze posições de especial interesse dentro da instalação. Com base nos resultados, foram avaliadas as limitações e as condições a serem observadas para o uso pretendido do laboratório.
Determination of the scattered radiation at the neutron calibration laboratory of IPEN using the shadow cone method
2017 - ALVARENGA, TALLYSON S.; FREITAS, BRUNO M.; FONSECA, EVALDO S.; PEREIRA, WALSAN W.; CALDAS, LINDA V.E.
Because of the increase in the demand for the calibration of neutron detectors, there is a need for new calibration services. In this context, the Calibration Laboratory of Instituto de Pesquisas Energéticas e Nucleares (IPEN), São Paulo, which already offers calibration services of radiation detectors with standard X, gamma, beta and alpha beams, has recently projected a new test laboratory for neutron detectors. This work evaluated the contribution of dispersed neutron radiation in this laboratory, using the cone shadow method and a Bonner sphere spectrometer to take the measurements at a distance of 100 cm from the neutron source. The dosimetric quantities Ḣ*(10) and Ḣp(10) were obtained at the laboratory, allowing the calibration of detectors.