THALES SALVADOR LIMA DE MORAIS

THALES SALVADOR LIMA DE MORAIS

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Primary standardization and Monte Carlo modeling of ( 243Am + 239Np) by means of a 4π(PC)-γ coincidence counting system
2023 - KOSKINAS, MARINA F.; MOREIRA, DENISE S.; YAMAZAKI, IONE M.; COLONNO, MARCELO; SEMMLER, RENATO; MORAIS, THALES S.L.; DIAS, MAURO S.
The procedure followed by the Nuclear Metrology Laboratory (LMN) at the IPEN for the primary standardization of a ( 243Am + 239Np) solution, in secular equilibrium, is described. The measurement was carried out in a 4π(PC) (α,β)− γ coincidence system. The total activity per unit mass of the solution was determined by the extrapolation technique, using a software coincidence counting systsem. The extrapolation curves were compared with Monte Carlo calculations by means of Code ESQUEMA, used in previous works, which, was improved and applied in order to calculate the alpha, beta, gamma, X-rays and coincidence spectra.
k0‑IPEN
2023 - DIAS, MAURO da S.; SEMMLER, RENATO; KOSKINAS, MARINA F.; MOREIRA, DENISE S.; YAMAZAKI, IONE M.; BRANCACCIO, FRANCO; BARROS, LIVIA F.; RIBEIRO, RAFAEL V.; MORAIS, THALES S.L. de
A software package for INAA (Instrumental Neutron Activation Analysis), developed at the Nuclear Metrology Laboratory of the IPEN-CNEN/SP, called k0-IPEN, is described. The package consists of a main program linked to nine subprograms designed to perform automatically most of the tasks necessary in order to obtain the mass fractions of the irradiated samples. External efficiency curves calculated by the Monte Carlo code MCNP6 can be read to extend the calibration curve to source to detector distances where only a few experimental points are available. Covariance analysis was used in all steps of the calculation. The validation of the code was tested in an intercomparison sponsored by the IAEA.
k0-IPEN
2022 - DIAS, MAURO da S.; SEMMLER, RENATO; KOSKINAS, MARINA F.; MOREIRA, DENISE S.; YAMAZAKI, IONE M.; BRANCACCIO, FRANCO; BARROS, LIVIA F.; RIBEIRO, RAFAEL V.; MORAIS, THALES S.L. de
A new software package for INAA, developed at the Nuclear Metrology Laboratory (LMN) of the Nuclear and Energy Research Institute (IPEN-CNEN/SP), called k0-IPEN, is described. The package consists of a main program linked to nine subprograms designed to perform automatically all the tasks necessary in order to obtain the mass fractions of the irradiated samples. The goals of these nine routines are: a) to calculate the experimental peak efficiencies and P/T ratios for the standard sources, together with all the corresponding uncertainties; b) to correct the peak efficiencies for coincidence summing; c) to fit the peak efficiencies and P/T ratios with log-log polynomial functions; d) to determine experimentally the  and f parameters by the Triple Bare and by the Cd Ratio Multimonitor Methods; e) to correct for interferences; f) to determine the average mass fractions, taking into account the correlations among all partial uncertainties involved. In the present version, the only data that must be inserted as input parameter, externally from the package, are the self-shielding correction factor, which is calculated by the MATSSF code, and the geometry factor that corrects for the difference between sizes of standard sources and measured samples. The code can deal with different spectrum formats such as CHN, SPE and CNF. The routine designed to calculate the peak areas has a simple algorithm and is not yet capable of separating multiplets. Therefore, it is suitable for analysing separated peaks, such as those found in standard calibration source measurements. However, for complex spectra, the code can read peak list files obtained from other codes, such as HyperMet or HyperLab. External efficiency curves calculated by the Monte Carlo code MCNP6 can be read to extend the calibration curve to regions where there are only a few experimental points available. The code k0-IPEN is being tested and its validation accomplished by means of an intercomparison sponsored by the IAEA, and presented at this conference.
Medida da meia-vida do 166GHo
2022 - MORAIS, THALES S.L.; KOSKINAS, MARINA F.; MOREIRA, DENISE S.; DIAS, MAURO S.
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 166gHo em detector semicondutor do tipo germânio hiperpuro (HPGe) no Laboratório de Metrologia Nuclear (LMN) do Centro do Reator de Pesquisas − IPEN (CRPq). O 166gHo foi produzido a partir da reação 165Ho(n,γ)166gHo 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.
Preliminary measurements using a Triple to Double Coincidence Ratio (TDCR) Liquid Scintillator Counter System
2021 - KOSKINAS, M.F.; KUZNETSOVA, M.; MOREIRA, D.S.; SHOUERI, R.M.; YAMAZAKI, I.M.; MORAIS, T.S.L.; SEMMLER, R.; DIAS, M.S.
The preliminary measurements using a Triple to Double Coincidence Ratio (TDCR) Liquid Scintillator Counter System, developed by the Nuclear Metrology Laboratory (LMN) at IPEN, is presented and 14C was selected to be standardized. This solution was previously calibrated by the efficiency tracing technique using a (PC)coincidence system, employing 60Co as a tracer. In order to determine the final activity, a Monte Carlo simulation was used to generate the extrapolation curve. The Software Coincidence System (SCS) developed by the LMN was used for both systems to register the events. MICELLE 2 code was used to calculate the theoretical TDCR efficiency. Measurements using HIDEX, a commercial liquid scintillator system, were also carried out and the results from the three methods were compared, showing a good agreement.
Medidas de seção de choque térmica e integral de ressonância para a reação 166mHo(n,γ)167Ho e da intensidade de emissão gama absoluta do 167Ho
2020 - MORAIS, THALES S.L. de
A seção de choque térmica (σ0) e a integral de ressonância (I0) para a reação 166mHo(n;γ)167Ho foram determinadas experimentalmente pelo método de ativação neutrônica e também foi determinada a intensidade de emissão γ absoluta para a energia 347 keV do 167Ho. As amostras foram preparadas a partir de uma solução estoque fornecida pela Electrotechnical Laboratory (Japão) e irradiadas no núcleo do reator de pesquisa tipo piscina IEA-R1 do IPEN-CNEN/SP, operando a 4,5 MW de potência. A densidade de fluxo de nêutrons foi monitorada com fios de liga Au-Al (0,1 % de Au) para a determinação do fluxo térmico e epitérmico pelo método de diferença de cádmio. A atividade do 167Ho foi medida em um espectrômetro de HPGe, calibrado em eficiência de detecção. Para a medida de seção de choque térmica e integral de ressonância, o método utilizado para os cálculos foi baseado no formalismo de Westcott e o tratamento estatístico foi realizado de espectrometria γ com detector de germânio hiperpuro (20 %) previamente detalhando todas as incertezas envolvidas por meio da análise da matriz de covariância. Para a medida da intensidade de emissão γ foi utilizado um sistema absoluto por coincidências 4πβ - γ, acoplado a um espectrômetro de HPGe. Os resultados obtidos foram 2,2 (2) kb para σ0, 2,6 (2) kb para I0 do 166mHo e 45,5 (16)% para Iγ na energia 347 keV do 167Ho.
Preliminary study of radionuclide standardization by TDCR method applying a time-to-amplitude converter
2019 - MORAIS, THALES S.L. de; KOSKINAS, MARINA F.; MOREIRA, DENISE S.; DIAS, MAURO da S.
This paper proposes an alternative to the use of counters for the standardization of radionuclides in a 3-photodetectors liquid scintillation counter by the triple to double coincidence ratio (TDCR) method using an electronic system for processing pulses that allows the subtraction of the accidental coincidences. The electronic system consists of ampli ers, discriminators, logic gates and delay modules feeding a time-to-amplitude converter (TAC) with output to a multichannel analyzer (MCA). This system does not require individual counters for each photodetector and coincident counts contribute to the noise reduction. The method compares 3 di erent TAC spectra registered in MCA with 4, 3 or 2 peaks obtained from di erent con gurations of the electronic system. For testing the system, a series of measurements with a 90Sr standard solution was performed.
Preliminary measurements using a Triple to Double Coincidence Ratio (TDCR) Liquid Scintillator Counter System
2019 - KOSKINAS, MARINA F.; KUZNETSOVA, MARIA; MOREIRA, DENISE S.; SCHOUERI, ROBERTO M.; MORAIS, THALES S.L. de; SEMMLER, RENATO; DIAS, MAURO da S.
The preliminary measurements using a Triple to Double Coincidence Ratio (TDCR) Liquid Scintillator Counter System developed by the Nuclear Metrology Laboratory (LMN) at IPEN, is presented. The TDCR system makes use of three photomultipliers positioned at 120° relative angle, operating in coincidence. For this preliminary measurement, 14C was selected to be standardized. This solution was previously calibrated by the efficiency tracing technique using a  (PC) coincidence system, employing 60Co as a tracer. 14C was chosen due to be a beta pure emitter with low end-point energy of 156 keV. The Software Coincidence System (SCS) developed by the LMN was used for both systems to register the events. MICELLE 2 code was used to calculate the theoretical TDCR efficiency. Measurements using HIDEX, a commercial liquid scintillator system, were also carried out and the results from the three methods were compared, showing a good agreement.
Study of induced activity of 167Ho from different neutron capture paths
2019 - MORAIS, T.S.L.; DIAS, M.S.
The main purpose of this study is to predict the induced activity of 167Ho produced by 165Ho(n,γ)166mHo(n,γ)167Ho, 165Ho(n,γ)166Ho(n,γ)167Ho and 166mHo(n,γ)167Ho reactions to choose the best path to measure the cross section with lowest uncertainty. The activation and decay scheme was established starting from the 165Ho target and considering single, double and triple neutron capture reactions. The activity results were deduced from differential activation equations and decay rates for all reaction products. The calculations were performed considering samples which were taken from a stock solution supplied by the Electrotechnical Laboratory (Japan) for purposes of an international comparison.