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Mauro Dias

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Papers by Mauro Dias

Neural networks for predicting neutron ambient dose equivalent measured by means of bonner spheres

IEEE Symposium Conference Record Nuclear Science 2004.

A Neural Network structure has been applied for predicting neutron Ambient Dose Equivalent measur... more A Neural Network structure has been applied for predicting neutron Ambient Dose Equivalent measured by means of a Bonner sphere spectrometer (BSS) set. The present work used the SNNS ("Stuttgart Neural Network Simulator") as the interface for designing, training and validation of a Multilayer Perceptron Network. The back-propagation algorithm was applied. The Bonner sphere set chosen has been calibrated at the National Physical Laboratory, United Kingdom, and uses gold activation foils as thermal neutron detectors. The neutron energy covered by the response functions goes from 0.0001 eV to 10 MeV. A set of 27 continuous neutron spectra was used for training and validating the neural network. Excellent results were obtained, indicating that the Neural Network can be considered an interesting alternative for estimating neutron Ambient Dose Equivalent measured by means of Bonner spheres.

A coincidence system for radionuclide standardization using surface barrier detectors

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1989

A system for the standardization of alpha-gamma or electron-X radionuclide emitters is described.... more A system for the standardization of alpha-gamma or electron-X radionuclide emitters is described. The system consists of one or two surface barrier detectors for alpha or electron detection which are coupled to thin-window NaI(Tl) crystals suitable for low-energy X- or gamma-ray detection. The performance of the system has been verified by the standardization of 241Am, 137Cs and 109Cd solutions. The

Determination of gamma-ray emission probabilities per decay of Ga-68

Applied Radiation and Isotopes, 2014

The procedure for 4π(PC)β À γ primary standardization of 68 Ga is described. Multiparametric fitt... more

Standardization of 55Fe by tracing method

Applied Radiation and Isotopes, 2008

This work describes the procedure followed by the Laborato´rio de Metrologia Nuclear (LMN) for th... more This work describes the procedure followed by the Laborato´rio de Metrologia Nuclear (LMN) for the standardization of 55 Fe by the tracing method. This technique was applied using two radionuclides, which decay by the electron capture process followed by a prompt gamma-ray, namely 51 Cr and 54 Mn, as tracers. The calibration was performed in a 4pb-g coincidence system. The efficiency was obtained by selecting a gamma-ray window set at the 320 keV total absorption peak for 51 Cr and at 834 keV for 54 Mn.

Medidas de Parâmetros Associados a Reações Nucleares Induzidas por Nêutrons no Reator IEA-R1

Contribuições do Reator IEA-R1 para a Pesquisa Nuclear: II Workshop Anual do Reator de Pesquisas – WARP 2, 2022

O presente trabalho apresenta uma retrospectiva dos diversos parâmetros para reações nucleares in... more O presente trabalho apresenta uma retrospectiva dos diversos parâmetros para reações nucleares induzidas por nêutrons, que foram determinados pelo Laboratório de Metrologia Nuclear (LMN) do IPEN, utilizando o reator IEA-R1. Esses parâmetros incluem: secções de choque, integrais de ressonância, além dos parâmetros k0 e Q0, que são associados ao Método de Ativação Neutrônica (NAA). Para este propósito, o LMN dispõe de sistemas de calibração primários e secundários, que são necessários para a determinação da atividade do radionuclídeo

Average Neutron Gross Section Measurements in U-235 Fission Spectrum for Some Threshold Reactions

Radiochimica Acta, 1992

Fission neutron spectrum averaged cross sections have been measured for the threshold reactions &... more Fission neutron spectrum averaged cross sections have been measured for the threshold reactions "Ni(n, 2n)"Ni, 2n ) ' " I , "Mn(n, 2n)='^Mn, "Cu(n, a)®»Co and "P(n , p)3'Si, by the activation technique using high-resolution y-ray spectroscopy. The fast neutron spectrum at the Irradiation position has been characterized by using an additional set of activation foils. The results are presented with a complete uncertainty covariance matrix and are compared with evaluated values and previous measurements.

Standardization and determination of the total internal conversion coefficient of In-111

Applied Radiation and Isotopes, 2014

The standardization of 111 In by means of a SEJ coincidence system, composed of a proportional co... more The standardization of 111 In by means of a SEJ coincidence system, composed of a proportional counter in S geometry, coupled to a 20% relative efficiency HPGe crystal, for measuring gamma-rays is presented. The data acquisition was performed by means of the software coincidence system (SCS) and the activity was determined by the extrapolation technique. Two gamma-ray windows were selected: at 171 keV and 245 keV total absorption peaks, allowing the determination of the total internal conversion coefficient for these two gamma transitions. The results were compared with those available in the literature.

Optimization of a coincidence system using plastic scintillators in 4π geometry

Applied Radiation and Isotopes, 2008

Improvements recently developed at the Nuclear Metrology Laboratory of IPEN-CNEN/SP in Sa˜o Paulo... more Improvements recently developed at the Nuclear Metrology Laboratory of IPEN-CNEN/SP in Sa˜o Paulo were performed in order to increase the detector efficiency of a 4pbÀg coincidence primary system using plastic scintillators in 4p geometry. Measurements were undertaken and compared to the original system and Monte Carlo simulations of the extrapolation curves were calculated for this new system and compared to experimental results. For this purpose, the code Penelope was applied for calculating response functions for each detector and the code Esquema, developed at LMN, was used for simulating the decay scheme processes.

Measurements of k0 and Q0 values for 64Zn(n,γ)65Zn and 68Zn(n,γ)69mZn reactions with covariance analysis

Applied Radiation and Isotopes, 2011

The values of k 0 and Q 0 for 64 Zn(n,g) 65 Zn and 68 Zn(n,g) 69m Zn reactions were determined ex... more The values of k 0 and Q 0 for 64 Zn(n,g) 65 Zn and 68 Zn(n,g) 69m Zn reactions were determined experimentally. The irradiations were performed near the core of the IEA-R1 3.5 MW nuclear research reactor of the Nuclear and Energy Research Institute-IPEN-CNEN/SP, in São Paulo, Brazil. The results for the neutron field parameters f and a were 49.7(19) and À 1.1(31) Â 10 À 3 , respectively. The resulting values of k 0 and Q 0 for 64 Zn(n,g) 65 Zn reaction were 5.63(8) Â 10 À 3 and 1.69(6), respectively, and the corresponding values for 68 Zn(n,g) 69m Zn reaction were 4.00(6) Â 10 À 4 and 2.34(4), respectively. These results were compared with the literature.

Medida da Meia-Vida do 166GHo

Contribuições do Reator IEA-R1 para a Pesquisa Nuclear: II Workshop Anual do Reator de Pesquisas – WARP 2, 2022

O conhecimento prévio da meia-vida de um radioisótopo possibilita o planejamento de experimentos ... more O conhecimento prévio da meia-vida de um radioisótopo possibilita o planejamento de experimentos e determinação de outras grandezas relacionadas a este radionuclídeo. Para aumentar a confiabilidade e precisão, foram realizadas medidas da meia-vida do 166g Ho em detector semicondutor do tipo germânio hiperpuro (HPGe) no Laboratório de Metrologia Nuclear (LMN) do Centro do Reator de Pesquisas − IPEN (CRPq). O 166g Ho foi produzido a partir da reação 165 Ho(n,γ) 166g Ho e as irradiações foram realizadas no reator IEA-R1 (IPEN/CNEN). A média dos valores encontrados para a meia-vida foi de T1/2 = 26,71 ± 0,12 h, que é compatível com os dados encontrados na literatura.

Primary standardization of 90Sr-90Y radioactive solution

An irradiation rig for neutron transmutation doping of silicon in the IEA-R1 research reactor

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1993

An irradiation rig with simple design has been constructed and instalfed in the IBA-RI research r... more An irradiation rig with simple design has been constructed and instalfed in the IBA-RI research reactor for neutron transmutation doping (NTD) of silicon with phosphorus. Crystal ingots with 3 and 4 in. diameter can be irradiated in this device. By adopting a procedure in which two ingots of 20 cm long each are irradiated simultaneously and their positions interchanged at a point when precisely half the total necessary neutron dose has been received, it has been possible to achieve the desired axial uniformity of the neutron dose. This method avoids the use of neutron absorbing shields around the crystals which necessarily compromise the overall irradiation capacity of the reactor. Test irradiations were performed with 50 float zone silicon crystals, and the results of radial and axial unifo~ities in the final resistivity values as well as the doping accuracy obtained in the test irradiations show an excellent doping quality achieved.

Covariance methodology applied to uncertainties in I-126 disintegration rate measurements

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1996

The covariance methodology applied to uncertainties in "? disintegration rate meaurements is desc... more The covariance methodology applied to uncertainties in "? disintegration rate meaurements is described. Two different coincidence systems were used due to the complex decay scheme of this radionuclide. The parameters involved in the determination of the disintegration rate in each experimental system present correlated components. In this case, the conventional statistical methods to determine the uncertainties (law of propagation) result in wrong values for the final uncertainty. Therefore, use of the methodology of the covariance matrix is necessary. The data from both systems were combined taking into account all possible correlations between the partial uncertainties.

Combination of nonlinear function and mixing method for fitting HPGe efficiency curve in the 59–2754kev energy range

Applied Radiation and Isotopes, 2004

A nonlinear function in combination with the method of mixing activity-calibrated and uncalibrate... more A nonlinear function in combination with the method of mixing activity-calibrated and uncalibrated gamma-ray sources is applied for fitting the experimental peak efficiency of HPGe spectrometers in the 59-2754 keV energy range. In addition, a step function was developed for fitting the gamma-ray background under the peak. Calibrated 241 Am, 133 Ba, 137 Cs, 152 Eu, 60 Co and 88 Y sources, as well as one 24 Na source (treated as uncalibrated) were used for obtaining the experimental peak efficiency curve. The results were compared to the conventional linear polynomial fitting. From the fitted parameters, the 24 Na activity was determined and compared with the result obtained from absolute measurements in a 4pb-g coincidence system.

An intercomparison of Monte Carlo codes used in gamma-ray spectrometry

Applied Radiation and Isotopes, 2008

simulations can be of significant help in the process of efficiency determination and their use h... more simulations can be of significant help in the process of efficiency determination and their use has been gaining in popularity over the years. Sophisticated packages exist for this purpose, but a study of the intrinsic differences they possess has not been conducted yet. The results of efficiency calculations with the most important and popular Monte Carlo codes used in gamma-ray spectrometry today were compared amongst themselves, without any reference to the experimental data.

Disintegration rate and gamma ray emission probability per decay measurement of 123I

Applied Radiation and Isotopes, 2012

A series of 123 I measurements have been carried out in a 4p(e A ,X)-g coincidence system. The ex... more A series of 123 I measurements have been carried out in a 4p(e A ,X)-g coincidence system. The experimental extrapolation curve was determined and compared to Monte Carlo simulation, performed by code ESQUEMA. From the slope of the experimental curve, the total conversion coefficient for the 159 keV total gamma transition, a 159 , was determined. All radioactive sources were also measured in an HPGe spectrometry system, in order to determine the gamma-ray emission probability per decay for several gamma transitions. All uncertainties involved and their correlations were analyzed applying the covariance matrix methodology and the measured parameters were compared with those from the literature.

Padronização Primária de Radionuclídeos Produzidos no Reator IEA-R1

Contribuições do Reator IEA-R1 para a Pesquisa Nuclear: II Workshop Anual do Reator de Pesquisas – WARP 2, 2022

Neste trabalho, apresentamos uma retrospectiva dos radionuclídeos produzidos no reator IEA-R1, qu... more Neste trabalho, apresentamos uma retrospectiva dos radionuclídeos produzidos no reator IEA-R1, que foram padronizados no Laboratório de Metrologia Nuclear (LMN) do CRPq, IPEN-CNEN/SP. Para este propósito, o laboratório dispõe de sistemas de calibração primários, utilizando a técnica de coincidência 4πβ−γ, aplicando uma metodologia específica para cada radionuclídeo. Neste método, os elétrons e os raios-X são usualmente registrados por um detector 4π consistindo em um contador proporcional, cintilador plástico ou cintilador líquido. Os raios gama são registrados por meio de detectores semicondutores de HPGe ou de cristais de NaI(Tl). Neste trabalho são apresentados os diagramas eletrônicos

Results of an international comparison for the activity measurement of 177Lu

Applied Radiation and Isotopes, 2012

An international Key Comparison of 177 Lu has recently been carried out. Twelve laboratories perf... more An international Key Comparison of 177 Lu has recently been carried out. Twelve laboratories performed assays for radioactivity content on aliquots of a common master solution of 177 Lu, leading to eleven results submitted for entry into the Key Comparison Database of the Mutual Recognition Arrangement. A proposed Comparison Reference Value (CRV) was calculated to be 3.288(4) MBq/g using all eleven results. Degrees of equivalence and their uncertainties were calculated for each laboratory based on the CRV. Most of the values reported by the participating laboratories were within 0.6% of the CRV.

Improvements in the response calculation of the dual thin scintillator neutron detector

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1992

The present work describes the new features introduced in the Monte Carle code-developed for effi... more The present work describes the new features introduced in the Monte Carle code-developed for efficiency and proton recoil spectra calculations of the dual thin scintillator (DTS) neutron detector-in order to achieve better accuracy and shorter processing time. The improvements include : relativistic kinematics, anisotropy in the angular distributions and application of the forced collision technique. The new calculated values are compared with experimental results at two neutron energies, namely : 2 .446 and 14 .04 MeV, obtained by means of the time correlated associated particle technique .

ISBN: 978-85-99141-03-8 STANDARDIZATION OF Tl-201 RADIOACTIVE SOLUTION

The standardization of 201Tl, using the 4pi(PC)-NaI(Tl) coincidence system, is presented. The dis... more The standardization of 201Tl, using the 4pi(PC)-NaI(Tl) coincidence system, is presented. The disintegration rate was determined by the extrapolation technique, using two methods: electronic discrimination and external absorbers. A Monte Carlo simulation program, developed in our laboratory, which predicts the behavior of the extrapolation curve, was applied and the results were compared with experimental values.