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Agitators or mixers are highly used in the chemical, food, pharmaceutical and cosmetic industries. During the fabrication process, the equipment may fail and compromise the appropriate stirring or mixing procedure. Besides that, it is also important to determine the right point of homogeneity of the mixture. Thus, it is very important to have a diagnosis tool for these industrial units to assure the quality of the product and to keep the market competitiveness. The radioactive particle tracking (RPT) technique is widely used in the nuclear field. In this paper, a method based on the principles of RPT is presented. Counts obtained by an array of detectors properly positioned around the unit will be correlated to predict the instantaneous positions occupied by the radioactive particle by means of an appropriate mathematical search location algorithm. Detection geometry developed employs eight NaI(Tl) scintillator detectors and a Cs-137 (662 keV) source with isotropic emission of gamma-rays. The modeling of the detection system is performed using the Monte Carlo Method, by means of the MCNP-X code. In this work, a methodology is presented to predict the position of a radioactive particle to evaluate the performance of agitators in industrial units by means of an Artificial Neural Network.

MCNP is a code extensively used to simulate experiments involving transport of radiation using the Monte Carlo method. This code allows the study of different geometries, materials, and radiation types (e.g. gamma, neutron, and electron), enabling the building of approximate models before the experimental implementation. The objective of this study is to develop an optimal geometry for the calculation of the mass attenuation coefficient for different materials using the MCNP code. Several measurement geometries were tested with different radiation energies, and the best results were obtained using lead collimators on both detector and radiation source. The considered geometries were isotropic source without any collimation, isotropic source with detector and/or source collimation, and a point source collimated into a cone of directions. The last case was proposed as a replacement for the computationally time expensive simulation of the two-collimator geometry. The energies 59.54 keV, 81 keV, 356 keV, and 662 keV were used to model 241Am, 133Ba, and 137Cs radiation sources, respectively. The materials were, NaI for the detector, aluminum, water, and sea water (3.5% NaCl) for the target sample, and lead for the collimators. The values of mass attenuation coefficient obtained from the simulations were compared with the theoretical NIST XCOM values for validation of the geometries.

Nuclear techniques based on the attenuation of gamma radiation are used in the industry to calculate flow rate, determine fluid density, predict inorganic scale in oil pipelines, evaluate industrial mixers, among other applications. In order to use these nuclear techniques is necessary to perform studies of important parameters of radioactive source and radiation detectors, which are part of the measurement geometry, such as detection efficiency and solid angle. The aim of this study is to calculate the solid angle and the effective solid angle subtended by a NaI(Tl) detector. The effective solid angle considers attenuation in the medium (between source and detector) and other effects of radiation interaction with matter. Mathematical models were developed using the MCNP6 code in order to evaluate the proposed measurement geometry. The source was placed in different positions to the detector to evaluate frontal and lateral solid angle contributions, which is an important parameter to obtain the intrinsic efficiency response function. The simulated model consists of a NaI(Tl) scintillator detector and two point isotropic sources (241Am and 137Cs). The results for the geometry used in this study showed that the difference between solid angle and effective solid angle reached 20.17% for 241Am and 2.58% for 137Cs, which means that it is highly recommended to consider the effective solid angle in the calculations.

Be determined which is the volumetric fraction. This paper presents a methodology to calculate volumetric fractions on the stratified flow regime, considering a cylindrical tube. A mathematical model of a measurement system was developed using the MCNP6 code. The mathematical equation was developed to calculate the volume fractions using the pulse height distributions obtained by a radiation detector. The stratified flow regime model considers air-oil, air-gasoline and oil-gasoline biphasic flow, in order to evaluate the performance of the proposed equation in fluid combinations with different densities. A comparative study with equations developed for square-section tubes from literature was performed. The study considered geometry of a source of 137Cs, an acrylic tubing measuring 8.0 cm in diameter and a 1¼ × ¾" NaI(T1) detector placed at a position diametrically opposed to a radiation source to measure the transmitted beam. The dimensions and materials to perform the simulation of the detectors were based on information obtained from the gammagraphy technique and the detector was experimentally validated. The volume fractions of each of the fluids were 0 up to 100% with variations of 25%.

The NaI(Tl) detector is one of the most used in gamma ray spectrometry because it presents high counting efficiency for gamma rays in a wide range of energy. The crystal can have a lower efficiency that can be indicated by the effects of its aging by several factors such as: the reaction of sodium iodide with magnesium oxide, absorption of water vapor by crystal, and problems related to photomultiplier. In an experiment, several measures can be take and when a doubt exists between one of the measured values it is possible to use a statistical test. Grubbs test is designed to verify the presence of extreme values in sample observations. This paper presents a methodology that has the objective of evaluating the homogeneity of a NaI(Tl) scintillation detector using the Grubbs test to validated the crystal homogeneity. The study pre-established five differents locations in frontal area of detector where measurements were performed using a 137Cs standard source in order to calculate the standard deviation.

This paper includes an analysis of literature about urban development of the colonial city in relation to modernity in Latin America. It illustrates the impact of modernity on the urban identity, and deals on how urban cultural heritage relates to the modernization of the city. The case of study is Cartagena de Indias, declared as a world heritage site in 1984 and district of tourism and culture since 1991. Considering that tourism is an activity that comes from modernity in the 20th century, the effects of tourism on the preservation of urban heritage and urban identity have been examined as well. This examination has been done to better understand the contrasts between the historic and the modern city, and the spacial and social contrasts between the tourist area and the urbanized area.