Photopeak efficiency response function of an underwater gamma ray NaI(TI) detector using MCNP X

This work presents a study to calculate the response function of a 1.5”x 1” NaI(Tl) scintillation detector when it is used in the marine environment in the energy range from 20 keV to 662 keV. The method takes into account both the scattering of photons in the water and the detection mechanism of the detector. In addition, the calculation of the response function of the whole system is essential for suppressing the background of the measurement and for estimating the concentration of the involved radionuclides, especially given the greater probability of primary gamma photons undergoing multiple scattering events before they interact with the detector. The experimental photopeak efficiency measurements for point sources were compared with the simulated results under the same conditions of the experimental setup to validate the simulation of the detector. Monte Carlo simulations were performed using the MCNP-X code for the investigation of gamma-ray absorption in water in different brines. The energy resolution curve was used to improve the response of the mathematical simulation of the detector. The detector’s simulation was based on information obtained from the gammagraphy technique. Both dimensions and materials were used for the calculation with the MCNP-X code. The photopeak efficiency of a NaI(Tl) detector for different radionuclides in the aquatic environment with different salinities was calculated

Study of gas pipelines cracks using transmission and scattering measures with nuclear technique

Most of the natural gas production is transported through pipelines that require periodic inspections to evaluate the structural integrity of the pipelines due to possible defects caused by degradation that can rupture causing leakage of the fluid causing major disasters. Based on this, the project presents a methodology for predicting cracks in pipe used in gas pipelines. The approximation is based on the principles of gamma densitometry to calculate the density of the pipe wall in order to investigate possible cracks. The natural gas fluid is found in such systems and interferes in the density calculations and therefore will be considered in the simulations. The detection system uses a narrow beam geometry appropriately, comprising gamma ray source (137Cs) and NaI(Tl) 3"x3" detectors for calculating transmitted and scattered photons. Different positioning angles of the detector are investigated. In this study, the MCNP-X code is used to perform the simulations, in order to develop a counting geometry. Simulations of different thicknesses of the crack were also used to determine the minimum thickness detected by the two NaI(Tl) detectors. Having equipment that can estimate cracks present in pipes used in gas pipelines, in addition to predicting their location can reduce costs and make a major contribution to this sector

Use of transmission gamma for study of calculation of incrustation thickness in oil pipelines

Incrustation can be defined as chemical compounds organic, inorganic and mixed, initially insoluble, and which precipitate accumulating in the internal wall of pipes, surface equipment and/or parts of components involved in the production and transport of oil. These compounds, when precipitating, cause problems in the oil industry and consequently result in losses in the optimization of the extraction process. Although the importance and impact of the precipitation of these compounds in the technological and economic scope, there is still the difficulty in determining methods that enable the identification and quantification of the incrustation at an initial stage. The use of the gamma transmission technique may provide support for a better understanding of the deposition of these compounds, making it a suitable tool for the non-invasive determination of their deposition in oil transport pipelines. The geometry used for the incrustation detection include a 280 mm diameter steel pipe containing barium sulphide incrustation (BaSO4) ranging from 5 to 80 mm, a gamma radiation source with divergent beam and as NaI(Tl) 2x2” scintillation detector. The opening size of the collimated beam was evaluated (2 to 7 mm) to also quantify the associated error in calculating the incrustation. The study was realized with computer simulation, using the MCNP-X code and validated by means of analytical equations that indicate the possibility of using this study for this purpose

Development of counting system for wear measurements using thin layer activation and the wearing apparatus

This paper focus on developing a counting system for the Wearing Apparatus, which is a device previously built to generate measurable wear on a given surface (Main Source) and to carry the fillings from it to a filter (second source). The Thin Layer Activation is a technique used to produce activity on one of the Wearing Apparatus' piece, this activity is proportional to the amount of material worn, or scrapped, from the piece's surface. Thus, by measuring the activity on those two points it is possible to measure the produced wear. The methodology used in this work is based on simulations through MCNP-X Code to find the best specifications for shielding, solid angles, detectors dimensions and collimation for the Counting System. By simulating several scenarios, each one different from the other, and analyzing the results in the form of Counts Per Second, the ideal counting system's specifications and geometry to measure the activity in the Main Source and the Filter (second source) is chosen. After that, a set of previously activated stainless steel foils were used to reproduce the real experiments' conditions, this real experiment consists of using TLA and the Wearing Apparatus, the results demonstrate that the counting system and methodology are adequate for such experiments

Study of the source-detector system geometry using the MCNP-X code in the flowrate measurement with radioactive tracers

The use radioactive tracers for flow rate measurement is applied to a great variety of situations, however the accuracy of the technique is highly dependent of the adequate choice of the experimental measurement conditions.To measure flow rate of fluids in ducts partially filled, is necessary to measure the fluid flow velocity and the fluid height. The flow velocity can be measured with the cross correlation function and the fluid level, with a fluid level meter system. One of the error factors when measuring flow rate, is on the correct setting of the source-detector of the fluid level meter system. The goal of the present work is to establish by mean of MCNP-X code simulations the experimental parameters to measure the fluid level [3]. The experimental tests will be realized in a flow rate system of 10 mm of diameter of acrylic tube for water and oil as fluids. The radioactive tracer to be used is the 82Br and for the detection will be employed two 1” NaI(Tl) scintillator detectors, shielded with collimators of 0.5 cm and 1 cm of circular aperture diameter

Estudo de método de transferência de eficiência usando detectores NaI(Tl)

A utilização de detectores cintiladores NaI(Tl) para medições implica na determinação da eficiência de detecção em função da energia dos fótons incidentes. A curva de eficiência pode ser obtida experimentalmente com a utilização de várias fontes mono energéticas calibradas com energias de emissão que abranjam todo o intervalo de interesse ou utilizando o método de Monte Carlo. O Instituto de Engenharia Nuclear desenvolve diversas metodologias usando estes detectores, pois são robustos, baratos e não precisam de resfriamento para sua utilização. A montagem de um arranjo experimental costuma ser complexa, pois vários fatores influenciam no resultado afetando a reprodutibilidade nas medições, tais como: paralelismo entre a fonte e o detector, alinhamento entre fonte e detector e precisão na distância fonte-detector. Diante de tais dificuldades, desenvolveu-se um sistema automatizado de posicionamento para o conjunto fonte-detector controlado por um micro controlador baseado na linguagem ARDUINO visando garantir a reprodutibilidade nos arranjos experimentais.Na fase inicial deste estudo desenvolveu-se um modelo matemático no código MCNP-X utilizando um detector NaI(Tl). Uma validação teórica usando o Método de Transferência de Eficiência foi realizada em três diferentes posições no eixo axial do detector (10,6 cm; 11,3 cm e 12,0 cm). Este método baseia-se na razão dos ângulos sólidos efetivos. A validação experimental apresentou erros relativos máximos de 7,74% para a posição 11,3 cm

NaI(Tl) detectors modeling in MCNP-X and Gate/Geant4 codes

NaI (Tl) detectors are widely used in gamma-ray densitometry, but their modeling in Monte Carlo codes, such as MCNP-X and Gate/Geant4, needs a lot of work and does not yield comparable results with experimental arrangements, possibly due to non-simulated physical phenomena, such as light transport within the scintillator. Therefore, it is necessary a methodology that positively impacts the results of the simulations while maintaining the real dimensions of the detectors and other objects to allow validating a modeling that matches up with the experimental arrangement. Thus, the objective of this paper is to present the studies conducted with the MCNP-X and Gate/Geant4 codes, in which the comparisons of their results were satisfactory, showing that both can beused for the same purposes

Volume fraction prediction in biphasic flow using nuclear technique and artificial neural network

The volume fraction is one of the most important parameters used to characterize air-liquid two-phase flows. It is a physical value to determine other parameters, such as the phase’s densities and to determine the flow rate of each phase. These parameters are important to predict the flow pattern and to determine a mathematical model for the system. To study, for example, heat transfer and pressure drop. This work presents a methodology for volume fractions prediction in water-gas stratified flow regime using the nuclear technique and artificial intelligence. The volume fractions calculate in biphasic flow systems is complex and the analysis by means of analytical equations becomes very difficult. The approach is based on gamma-ray pulse height distributions pattern recognition by means of the artificial neural network. The detection system uses appropriate broad beam geometry, comprised of a (137Cs) energy gamma-ray source and a NaI(Tl) scintillation detector in order measure transmitted beam whose the counts rates are influenced by the phases composition. These distributions are directly used by the network without any parameterization of the measured signal. The ideal and static theoretical models for stratified regime have been developed using MCNP-X code, which was used to provide training, test and validation data for the network. The detector also was modeled with this code and the results were compared to experimental photopeak efficiency measurements of radiation sources. The proposed network could obtain with satisfactory prediction of the volume fraction in water-gas system, demonstrating to be a promising approach for this purpose

Estudo de viabilidade de rotas para produção de 124I

Este relatório visa pesquisar as reações de produção do 124I utilizando o Sb (3He e α) ou Te (próton e dêuteron) como alvos a fim de escolher uma rota para implementação de uma metodologia de irradiação e processamento químico do 124I utilizando o Cíclotron CV-28 do Instituto de Engenharia Nuclear, considerando o compromisso com o rendimento e com as impurezas do processo, custo de produção, além de manter o índice de confiabilidade atual obtido na produção do 123I e 18F

Study of photon attenuation coefficient in brine using MCNP code

In petroleum industry, multiphase flows are common and the relative salt content of the water component depends on the location of oil extraction. The salt present in the water component causes incrustations in the pipeline and may interfere in the flow measurement. This paper presents an elaborate model using MCNP code to simulate a narrow beam gamma ray source, a brine sample and a NaI(Tl) detector, with beam energies ranging from 59,54 keV to 662 keV. Through this model, we can relate the photon attenuation coefficient to the salinity of water. This model can be experimentally reproduced, and used to measure the salinity in situ without affecting the medium