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Evaluation of Two Ultrasonic Systems for Analysis of Porosity in Ceramic
Get PDFThe Ultrasound Laboratory of the Nuclear Engineering Institute (LABUS / IEN) has developed an ultrasonic
technique to measure porosity in nuclear fuel pellets (UO2). By difficulties related to the handling of UO2
pellets, Alumina (Al2O3) pellets have been used in preliminary tests, until a methodology for tests with pellets of UO2 could be defined. In a previous work, in which a contact ultrasonic technique was used, good results were obtained to measure the porosity of Alumina pellets. In the current studies, it was found that the frequency spectrum of an ultrasonic pulse is very sensitive to the porosity of the medium in which it propagates. In order to define the most appropriate experimental apparatus for using immersion technique in future tests, two ultrasonic systems, available in LABUS, which permit to work with the ultrasonic pulse in the frequency domain were evaluated . One system was the Explorer II (Matec INSTRUMENTS) and the other the ultrasonic pulse generator Epoch 4 Plus (Panametrics) coupled with an oscilloscope TDS 3032B (Tektronix). For this evaluation, several frequency spectra were obtained with the two equipment, by the passage of the ultrasonic wave in the same pellet of Alumina. This procedure was performed on four different days, on each day 12 ultrasonic signals were acquired, one signal every 10 minutes, with each apparatus. The results were compared and analyzed as regard the repeatability of the frequency spectra obtained
Semi-automatic rubble counting system for superheated droplet detectors
Get PDFNeutron dose rate measurements are normally performed by means of PADC, CR-39 and TLD detectors.
Although, none of these devices can give instant reading of the neutron dose, recently new kind of detectors are
being developed, based on the formation of tiny drops in a superheated liquid suspended in a polymer or gel
solution, called superheated droplet detector (SDD) or also as bubble detectors (BD), with no response for
gamma radiation. This work describes the experimental setup and the developed procedures for acquiring and
processing digital images obtained with bubble detector spectrometer (BDS), developed by Bubble Technology
Industries, for personal neutron dosimeter and/or neutron energy fluence measurements in nuclear facilities. The
results of the neutron measurements obtained during the F-18 production, at the RDS-111 cyclotron, are
presented. These neutron measurements were the first ones with this type of BDS detectors in a particle
accelerator facility in Brazil and it was very important to estimate neutron dose rate received by occupationally
exposed individuals
Evaluation of two ultrasonic systems for analysis of porosity in ceramic
Get PDFThe Ultrasound Laboratory of the Nuclear Engineering Institute (LABUS / IEN) has developed an ultrasonic
technique to measure porosity in nuclear fuel pellets (UO2). By difficulties related to the handling of UO2
pellets, Alumina (Al2O3) pellets have been used in preliminary tests, until a methodology for tests with pellets
of UO2 could be defined. In a previous work, in which a contact ultrasonic technique was used, good results
were obtained to measure the porosity of Alumina pellets. In the current studies, it was found that the frequency
spectrum of an ultrasonic pulse is very sensitive to the porosity of the medium in which it propagates. In order
to define the most appropriate experimental apparatus for using immersion technique in future tests, two
ultrasonic systems, available in LABUS, which permit to work with the ultrasonic pulse in the frequency
domain were evaluated . One system was the Explorer II (Matec INSTRUMENTS) and the other the ultrasonic
pulse generator Epoch 4 Plus (Panametrics) coupled with an oscilloscope TDS 3032B (Tektronix). For this
evaluation, several frequency spectra were obtained with the two equipment, by the passage of the ultrasonic
wave in the same pellet of Alumina. This procedure was performed on four different days, on each day 12
ultrasonic signals were acquired, one signal every 10 minutes, with each apparatus. The results were compared and analyzed as regard the repeatability of the frequency spectra obtained
Analysis of ultrasonic techniques for the characterization of microfiltration polymeric membranes
Get PDFThe use of polymeric membranes is extremely important in several industries such as nuclear, biotechnology,
chemical and pharmaceutical. In the nuclear area, for instance, systems based on membrane separation
technologies are currently being used in the treatment of radioactive liquid effluent, and new technologies using
membranes are being developed at a great rate. The knowledge of the physical characteristics of these
membranes, such as, pore size and the pore size distribution, is very important to the membranes separation
processes. Only after these characteristics are known is it possible to determine the type and to choose a
particular membrane for a specific application. In this work, two ultrasonic non destructive techniques were
used to determine the porosity of membranes: pulse echo and transmission. A 25 MHz immersion transducer
was used. Ultrasonic signals were acquired, for both techniques, after the ultrasonic waves passed through a
microfiltration polymeric membrane of pore size of 0.45 μm and thickness of 180 μm. After the emitted
ultrasonic signal crossed the membrane, the received signal brought several information on the influence of the
membrane porosity in the standard signal of the ultrasonic wave. The ultrasonic signals were acquired in the
time domain and changed to the frequency domain by application of the Fourier Fast Transform (FFT), thus
generating the material frequency spectrum. For the pulse echo technique, the ultrasonic spectrum frequency
changed after the ultrasonic wave crossed the membrane. With the transmission technique there was only a
displacement of the ultrasonic signal at the time domain
Synthesis of nanocrystalline rutile-phase titania at low temperatures
Get PDFAnatase and rutile are the predominant phases in titanium dioxide. In many cases, rutile stable phase is the desired product material, but at low temperatures methods of synthesis (aqueous route) produce metastable anatase as a major product that reverts to rutile only when heated up to 1000 °C. Calcination for obtaining rutile phase is the greatest energy demanding step for titanium dioxide production by the sulphate process, and is responsible for almost 60% of total energy consumption. In this work, an innovative technique involving a sonication pre-treatment in acid medium was developed to change particle reactivity and accelerate the anatase-to-rutile transformation. Scanning electron micrographs and surface area measurements confirmed the alteration in texture and porosity of the powders. Results indicate that it
is possible to obtain 100% of rutile phase at temperatures as low as 430 °C
Avaliação da Linearidade de Métodos Analíticos para o Radiofármaco Fluorodesoxiglicose-18
Get PDFLinearity Evaluation of Analytical Methods of Radiopharmaceutical Fluorodeoxyglucose-18”. Radiopharmaceuticals are drugs used in Nuclear Medicine to measure physiological and biological functions, to evaluate higher brain function, to study the pathophysiology of various disorders and to develop effective therapy. Positron emission tomography (PET) and single-photon emission computed tomography are representative molecular imaging methods. Development of radiopharmaceuticals is a key for successful in vivo imaging. However, not only the development of new radiopharmaceuticals are important. The quality and behavior of this radiopharmaceuticals must be improved daily. In this manuscript, the authors introduces experiences and concepts for development of quality control test to be used in the routine of radiopharmaceuticals industry, in order to verify the quality of the method and the quality of the final product (radiopharmaceuticals) produced. The results showed that an alternative methods for quantification of ethanol is required. Despite of the results of the linearity, the quantification of content of radiopharmaceuticals (F-18 and FDG-18) shown to be satisfactory.4 p.Radiofármacos são medicamentos utilizados na Medicina Nuclear para avaliar funções biológicas
e patofisiológicas, realizar estudos do funcionamento do cérebro e diversas outras enfermidades, assim
comodesenvolver uma terapia eficaz. Tomografia por emissão de pósitron e tomografia computadorizada
por emissão de fóton único são alguns dos métodos que utilizam radiofármacos. Desenvolvimento de novos radiofármacos é a solução para a análise in vivo de imagens endógenas. Contudo não só o desenvolvimento é importante. A qualidade e o comportamento do radiofármaco desenvolvido devem ser comprovadas, diariamente. Nesse trabalho os autores avaliam a metodologia de determinação de etanol e do teor de F-18 e FDG-18 como forma de avaliação da qualidade do produto final, e dos método utilizados, assim como dos equipamentos. Os resultados revelam que a metodologia de determinação de etanol em solução de FDG-18 deve ser revista. Contudo a análise de teor de F-18 e FDG-18, mostrou-se bastante eficaz
A PSO approach for preventive maintenance scheduling optimization
Get PDFThis work presents a Particle Swarm Optimization (PSO) approach for preventive maintenance policy
optimization, focused in reliability and cost. The probabilistic model for reliability and cost evaluation is
developed in such a way that flexible intervals between maintenance are allowed. As PSO is skilled for realcoded continuous spaces, a non-conventional codification has been developed in order to allow PSO to solve scheduling problems (which is discrete) with variable number of maintenance interventions. In order to evaluate the proposed methodology, the High Pressure Injection System (HPIS) of a typical 4-loop PWR has been considered. Results demonstrate ability in finding optimal solutions, for which expert knowledge had to be automatically discovered by PSO
Flow Regime Identification Methodology with Mcnp-X Code And Artificial Neural Network
Get PDFThis paper presents flow regimes identification methodology in multiphase system in annular, stratified and
homogeneous oil-water-gas regimes. The principle is based on recognition of the pulse height distributions
(PHD) from gamma-ray with supervised artificial neural network (ANN) systems. The detection geometry
simulation comprises of two NaI(Tl) detectors and a dual-energy gamma-ray source. The measurement of
scattered radiation enables the dual modality densitometry (DMD) measurement principle to be explored. Its
basic principle is to combine the measurement of scattered and transmitted radiation in order to acquire
information about the different flow regimes. The PHDs obtained by the detectors were used as input to ANN. The data sets required for training and testing the ANN were generated by the MCNP-X code from static and ideal theoretical models of multiphase systems. The ANN correctly identified the three different flow regimes for all data set evaluated. The results presented show that PHDs examined by ANN may be applied in the successfully flow regime identification
Artificial Neural Network and Neutron Aplication in a Volume Fraction Calculation in Annular and Stratified Multiphase System
Get PDFMultiphase flows, type oil–water-gas are very common among different industrial activities, such as chemical
industries and petroleum extraction, and its measurements show some difficulties to be taken. Precisely
determining the volume fraction of each one of the elements that composes a multiphase flow is very important in chemical plants and petroleum industries. This work presents a methodology able to determine volume fraction on Annular and Stratified multiphase flow system with the use of neutrons and artificial intelligence, using the principles of transmission/scattering of fast neutrons from a 241Am-Be source and measurements of point flow that are influenced by variations of volume fractions. The proposed geometries used on the mathematical model was used to obtain a data set where the thicknesses referred of each material had been changed in order to obtain volume fraction of each phase providing 119 compositions that were used in the simulation with MCNP-X –computer code based on Monte Carlo Method that simulates the radiation transport. An artificial neural network (ANN) was trained with data obtained using the MCNP-X, and used to correlate such measurements with the respective real fractions. The ANN was able to correlate the data obtained on the simulation with MCNP-X with the volume fractions of the multiphase flows (oil-water-gas), both in the pattern of annular flow as stratified, resulting in a average relative error (%) for each production set of: annular (air= 3.85; water = 4.31; oil=1.08); stratified (air=3.10, water 2.01, oil = 1.45). The method demonstrated good efficiency in the determination of each material that composes the phases, thus demonstrating the feasibility of the technique
Prediction of volume fractions in three-phase flow susing nuclear technique and artificial neural network
No full textThis workpresentsmethodologybasedonnucleartechniqueandartificialneuralnetworkforvolume
fraction predictionsinannular,stratifiedandhomogeneousoil–water–gasregimes.Usingprinciplesof
gamma-rayabsorptionandscatteringtogetherwithanappropriategeometry,comprisedofthree
detectors andadual-energygamma-raysource,itwaspossibletoobtaindata,whichcouldbe
adequatelycorrelatedtothevolumefractionsofeachphasebymeansofneuralnetwork.TheMCNP-X
code wasusedinordertoprovidethetrainingdataforthenetwork.This workpresentsmethodologybasedonnucleartechniqueandartificialneuralnetworkforvolume
fraction predictionsinannular,stratifiedandhomogeneousoil–water–gasregimes.Usingprinciplesof
gamma-rayabsorptionandscatteringtogetherwithanappropriategeometry,comprisedofthree
detectors andadual-energygamma-raysource,itwaspossibletoobtaindata,whichcouldbe
adequatelycorrelatedtothevolumefractionsofeachphasebymeansofneuralnetwork.TheMCNP-X
code wasusedinordertoprovidethetrainingdataforthenetwork