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Estudo experimental de escoamentos bifásicos em duto horizontal usando uma técnica de visualização
Get PDFO estudo da dinâmica dos escoamentos bifásicos gás-líquido é de grande importância para as áreas de energia engenharia nuclear e de petróleo e gás natural. Reconhecidos pela literatura como sendo de grande
complexidade, os escoamentos gás-líquido têm recebido ao longo do tempo uma especial atenção da parte de
cientistas e pesquisadores interessados no desenvolvimento de modelos teóricos, capazes de prever o
comportamento desses escoamentos em termos de seus parâmetros mais importantes e de suas estruturas físicas. As velocidades das fases gás e líquido, a evolução dessas fases durante os escoamentos, as posições das interfaces gás-líquido, são alguns exemplos de parâmetros e de estruturas que requerem cuidadosos estudos experimentais e teóricos. No presente trabalho é realizado um estudo experimental de visualização de
escoamentos bifásicos água-ar, estratificados e intermitentes, em um duto tubo horizontal de seção circular com 51 mm de diâmetro interno. O estudo consiste em filmar uma mistura água-ar que passa por um trecho
transparente do duto, utilizando uma filmadora de alta velocidade. Em seguida, as imagens obtidas da filmagem são analisadas quadro a quadro, e desta análise são extraidos dados de altura das interfaces gás-líquido, comprimentos e velocidades de bolhas de gás. Então, estes dados são verificados com o auxílio de correlações experimentais e teóricas disponíveis na literatura
Applying a neuro-fuzzy approach for transient identification in a nuclear power plant
Get PDFTransient identification in Nuclear Power Plant (NPP) is often a very hard task and may involve a great amount
of human cognition. The early identification of unexpected departures from steady state behavior is an essential
step for the operation, control and accident management in NPPs. The bases for the transient identification relay
on the evidence that different system faults and anomalies lead to different pattern evolution in the involved
process variables. During an abnormal event, the operator must monitor a great amount of information from the
instruments that represents a specific type of event. Several systems based on specialist systems, neuralnetworks,
and fuzzy logic have been developed for transient identification. In the work, we investigate the
possibility of using a Neuro-Fuzzy modeling tool for efficient transient identification, aiming to helping the
operator crew to take decisions relative to the procedure to be followed in situations of accidents/transients at
NPPs. The proposed system uses artificial neural networks (ANN) as first level transient diagnostic. After the
ANN has done the preliminary transient type identification, a fuzzy-logic system analyzes the results emitting
reliability degree of it. A preliminary evaluation of the developed system was made at the Human-System
Interface Laboratory (LABIHS). The obtained results show that the system can help the operators to take
decisions during transients/accidents in the plant
Estudo da influência das micro-estruturas e da porosidade de pastilhas de alumina no pulso ultra-sônico no domínio da frequência
No full textEsse trabalho é parte integrante de um estudo que visa a aplicabilidade
da técnica ultra-sônica no domínio da freqüência para a caracterização não
destrutiva de pastilhas combustíveis cerâmicas, que é de grande interesse
devido a preocupação com a segurança e eficácia na indústria nuclear.
Nesse Trabalho foram analisadas as alterações nos espectros de
freqüência, gerados pela passagem de um pulso ultra-sônico através de
pastilhas cerâmicas à base de óxido de alumínio (Al2O3). Utilizando a técnica
ultra-sônica no domínio da freqüência, juntamente com análise micro-estrutural
das pastilhas, através do microscópio eletrônico de varredura, foi possível
associar as características do material inspecionado ao seu respectivo espectro
de freqüência. A caracterização foi feita em 40 pastilhas de Alumina
sinterizadas às temperaturas de 1150, 1400, 1480, 1540 e 1580°C com
porosidades, medidas pelo método de Arquimedes, variando de 5,09% a
37,3%.
Os resultados obtidos mostram que esta técnica ultra-sônica é eficaz na
determinação da micro-estrutura de pastilhas cerâmicas de Alumina podendo
ser aplicado na caracterização de outros materiais porosos em uma linha de
produção, onde o formato do espectro de freqüência gerado pela estrutura do
material pode determinar se as pastilhas se enquadram nas especificações
requeridas.This work is part of a study to the applicability of ultrasonic technique in
the frequency domain for non-destructive characterization of ceramic pellets
fuel, which is of great interest because of concern about the safety and efficacy
in the nuclear industry.
In this work it was analised if there were changes in frequency spectrum,
generated by the traveling of an ultrasonic pulse through ceramic pellets of
aluminum oxide (Al2O3). Using the ultrasonic technique in the frequency
domain, together with micro-structural analysis of pellets by scanning electron
microscope, it was possible to associate the characteristics of the material
inspected with its respectives frequency spectrum. The characterization was
performed on 40 pellets alumina sintered in the temperatures of 1150, 1400,
1480, 1540 and 15800C with porosities, as measured by the Archimedes
method, ranging from 5.09% to 37.3%.
The results show that the ultrasonic technique is effective in determining
the micro-structure of ceramic alumina pellets and can be applied in the
characterization of other porous materials in a production line, where the format
of the frequency spectrum generated by the structure of the material may
determine if the pellets belong the required specifications
Sistema de auxílio para o direcionamento da atenção no diagnóstico de acidentes em usinas nucleares baseado em inteligência artificial
No full textA identificação de transientes numa central nuclear é freqüentemente uma tarefa muito difícil e, normalmente, depende, basicamente, da cognição humana. A
identificação precoce dos desvios inesperados nos comportamentos com estado
estacionário é um passo essencial para a operação, controle e gestão de acidentes em
centrais nucleares. As bases para a identificação estão na percepção de que diferentes falhas e anomalias no sistema conduzem a distintos padrões evolutivos nas variáveis envolvidas no processo. Durante um evento anormal, o operador deve controlar uma grande quantidade de informação a partir dos instrumentos, próprios a cada tipo específico de evento. Contudo, diversos modelos baseados em sistemas especialistas, redes neurais e lógica fuzzy estão sendo desenvolvidos para a identificação de transientes. No presente trabalho, a investigação centra-se na possibilidade de se utilizar uma ferramenta de modelagem Neuro-Fuzzy para uma eficiente identificação de transientes, com o objetivo de auxiliar o operador a tomar decisões em relação ao procedimento a ser seguido em situações de acidentes / transientes em centrais nucleares. O sistema proposto utiliza redes neurais artificiais (RNA), como primeiro nível de diagnóstico. A partir da identificação de transientes preliminar desenvolvida pela RNA, o sistema de
lógica fuzzy analisa os resultados, emitindo importante grau de confiabilidade. Uma
avaliação preliminar do sistema desenvolvido foi feita no Laboratório de Interface
Homem-Sistema (LABIHS).Transient identification in Nuclear Power Plant (NPP) is often a very hard task
and may involve a great amount of human cognition. The early identification of
unexpected departures from steady state behavior is an essential step for the operation,
control and accident management in NPPs. The bases for the transient identification
relay on the evidence that different system faults and anomalies lead to different pattern
evolution in the involved process variables. During an abnormal event, the operator
must monitor a great amount of information from the instruments that represents a
specific type of event. Several systems based on specialist systems, neural-networks,
and fuzzy logic have been developed for transient identification. In the work, we
investigate the possibility of using a Neuro-Fuzzy modeling tool for efficient transient
identification, aiming to helping the operator crew to take decisions relative to the
procedure to be followed in situations of accidents/transients at NPPs. The proposed
system uses artificial neural networks (ANN) as first level transient diagnostic. After the
ANN has done the preliminary transient type identification, a fuzzy-logic system
analyzes the results emitting reliability degree of it. A preliminary evaluation of the
developed system was made at the Human-System Interface Laboratory (LABIHS). The
obtained results show that the system can help the operators to take decisions during
transients/accidents in the plant
Uranium and thorium determination in Santa Quitéria liquor by ICP-OES analysis
Get PDFThe mineral source of Itataia located in Santa Quitéria (Ceará / Brazil) is a phosphorusuraniferous
one, where uranium occurs in collophanite (fluorapatite) form. Phosphate
minerals of the apatite family make possible the uses of uranium as a byproduct. The sulfuric
leaching of the phosphate rock in order to obtain phosphoric acid also permits uranium
recovery. Thus, the liquor coming from the leaching contains high levels of phosphoric acid
as well as elements like Mg, Fe, U, Zr, Th and some rare earths in significative
concentrations. The direct determination of U and Th content of this liquor is essential to a
rapid response in the uranium separation and purification together process by solvent
extraction, aiming its use for commercial purposes, as nuclear industry fuel. In this study U
and Th were determined by Inductively Coupled Plasma Spectrometry (ICP-OES) in several
samples of liquor, in high concentrations of H3PO4 in environment. Several ratios of U/Th
and H3PO4 concentrations were studied, in order to find the optimal conditions for the direct
determination of U and Th, without need to prior separation
Proposal of counting method for bubble detectors and their intercomparisons
Get PDFThe study of neutron’s spectrometry and dosimetry has become significantly easier due to relatively new devices called bubble detectors. Insensitive to gamma rays and composed by superheated emulsions, they still are subjects of many researches in Radiation Physics and Nuclear Engineering. In bubble detectors, either exposed to more intense neutron fields or for a long time, when more bubbles are produced, the statistical uncertainty during the dosimetric and spectrometric processes is reduced. A proposal of this nature is set up in this work, which presents ways to perform counting processes for bubble detectors and an updated proceeding to get the irradiated detectors’ images in order to make the manual counting easier. Twelve BDS detectors were irradiated by RDS111 cyclotron from IEN’s (Instituto de Engenharia Nuclear) and photographed using an assembly specially designed for this experiment. Counting was proceeded manually in a first moment; simultaneously, ImagePro was used in order to perform counting automatically. The bubble counting values, either manual or automatic, were compared and the time to get them and their difficult levels as well. After the bubble counting, the detectors’ standardizes responses were calculated in both cases, according to BDS’s manual and they were also compared. Among the results, the counting on these devices really becomes very hard at a large number of bubbles, besides higher variations in counting of many bubbles. Because of the good agreement between manual counting and the custom program, the last one revealed a good alternative in practical and economical levels. Despite the good results, the custom program needs of more adjustments in order to achieve more accuracy on higher counting on bubble detectors for neutron measurement applications
High speed ultrasonic system to measure bubbles velocities in a horizontal two-phase flow
Get PDFIn this work, a non invasive technique consisting of a high speed ultrasonic multitransducer pulse-echo system
was developed to characterize gas-liquid two-phase flow parameters that are important in the study of the
primary refrigeration circuit of nuclear reactors. The high speed ultrasonic system consists of two transducers
(10 MHz/φ 6.35 mm), a generator/multiplexer board, and software that selects and has a data acquisition
system of the ultrasonic signals. The resolutions of the system and the pulse time generated from each
transducer are, respectively, 10 ns and 1.06 ms. The system initially was used in the local instantaneous
measurement of gas-liquid interface in a circular horizontal pipe test section made of a 5 m long stainless steel
pipe of 51.2 mm inner diameter, where the elongated bubbles velocity was measured (Taylor bubbles). The
results show that the high speed ultrasonic pulse-echo system provides good results for the determination of
elongated bubbles velocities
A concept map aiding the knowledge management to build the collective knowledge in a nuclear organization - a case study: IEN
Get PDFThis paper´s proposition is to build and apply a tool to aid the knowledge management based in the intellectual
capital as a value and competitiveness aggregator for a science, technology and innovation public organization
in the Brazilian’s nuclear area – the “Instituto de Engenharia Nuclear – IEN”.
It will be presented the hole survey of the finalistic activities and what has been considered the intellectual
capital to be developed and strategically valuated in its decision making practices.
It was also surveyed the inter relations between the stakeholders, hereby the maintainer (CNEN), federal
government, support foundations, public employees and contributors, in many different aspects focusing the
continuity of research and development (R&D) activities and its results.
As it’s going to be detailed, the tool has been designed based in the concept map methodology using the Cmap
tools software. The hole cognitive basis used here was constructed under disclosed and recognized knowledge
models about knowledge, knowledge management, knowledge transference and intellectual capital
Parallel particle swarm optimization algoritms in nuclear problems
Get PDFParticle Swarm Optimization (PSO) is a population-based metaheuristic (PBM), in which solution candidates
evolve through simulation of a simplified social adaptation model. Putting together robustness, efficiency and
simplicity, PSO has gained great popularity. Many successful applications of PSO are reported, in which PSO
demonstrated to have advantages over other well-established PBM. However, computational costs are still a
great constraint for PSO, as well as for all other PBMs, especially in optimization problems with time
consuming objective functions. To overcome such difficulty, parallel computation has been used. The default
advantage of parallel PSO (PPSO) is the reduction of computational time. Master-slave approaches, exploring
this characteristic are the most investigated. However, much more should be expected. It is known that PSO
may be improved by more elaborated neighborhood topologies. Hence, in this work, we develop several
different PPSO algorithms exploring the advantages of enhanced neighborhood topologies implemented by
communication strategies in multiprocessor architectures. The proposed PPSOs have been applied to two
complex and time consuming nuclear engineering problems: i) reactor core design (CD) and ii) fuel reload (FR)
optimization. After exhaustive experiments, it has been concluded that: i) PPSO still improves solutions after
many thousands of iterations, making prohibitive the efficient use of serial (non-parallel) PSO in such kind of
realworld problems and ii) PPSO with more elaborated communication strategies demonstrated to be more
efficient and robust than the master-slave model. Advantages and peculiarities of each model are carefully
discussed in this work