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Determination of thorium in the presence of uranium by wavelength dispersive X- ray fluorescence
No full textThe quantitative analysis of thorium by Wave Dispersion X Ray Fluorescence (WDXRF) is a non-destructive
and fast technique. It allows direct quantification of the element and expresses this as an oxide formula without
opening the samples and separating the elements, though when uranium is present in a higher concentration than thorium a mutual interference takes place in consequence of the element analytic line absorption or
intensification phenomena. This work presents the effects of this kind of interference and over the possibility of
using the ore direct standard addiction method to increase the obtained signal in WDXRF to compensate the
matrix effect allowing the thorium quantification with high reliability of about 95%
Virtual environment simulation as a atool to support evacuation planning
Get PDFThis work is a preliminary study of the use of a free game-engine as a tool to build and to navigate in virtual
environments, with a good degree of realism, for virtual simulations of evacuation from building and risk zones.
To achieve this goal, some adjustments in the game engine have been implemented. A real building with four
floors, consisting of some rooms with furniture and people, has been virtually implemented. Simulations of
simple different evacuation scenarios have been performed, measuring the total time spent in each case. The
measured times have been compared with their corresponding real evacuation times, measured in the real
building. The first results have demonstrated that the virtual environment building with the free game engine is
capable to reproduce the real situation with a satisfactory level. However, it is important to emphasize that such
virtual simulations serve only as an aid in the planning of real evacuation simulations, and as such must never
substitute the later
Design and evaluation of human-system interfaces for industrial plants
Get PDFThe Human-System Interfaces (HSIs) are important parts of an industrial plant in which the operator interact to
carry through its functions and tasks. The HSIs manly include alarms, displays of information and controls. The
development and evaluation of HSIs for control rooms is one of research area at the Human-System Interface
Laboratory (LABIHS). This article shows briefly the state of art of the human-system interfaces, with emphasis
in the three main interface construction methodologies: the task-oriented human interface, the ecological human interface, and the function-oriented human interface. The article also gives a brief description of the LABIHS infrastructure, with emphasis in the tools for construction and testing new interfaces. As a starting point for future developing, a new overview screen for the LABIHS simulator based in the function-oriented
methodology was developed. The new overview screen was evaluated in the LABIHS NPP simulator using the
E-0 procedure of the plant emergency operation procedures (EOPs). The results showed substantial
improvement in the new overview screen compared to the previous one
Determinação de radionuclídeos naturais por espectrometria gama com detector de alta resolução
Get PDFApresenta-se a metodologia para a determinação de radionuclídeos naturais em amostras sólidas, através da medida dos raios gama dos nuclídeos filhos das séries de desintegração do U-238 e Th-232, na qual levaram-se em conta interferências espectrais e efeito de auto-absorção da matriz. Para o raio gama de 911 keV do Ac-228 as correções devido ao efeito de atenuação foram entre 20 a 50%
Visualization of two-phase flow in metallic pipes using neutron radiographic technique
No full textThe study of two-phase flow is a matter of great interest both for the engineering and oil industries. The
production of oil and natural gas involves the transportation of fluids in their liquid and gaseous states,
respectively, to the processing plant for refinement. The forecasting of two-phase flow in oil pipes is of the
utmost important yet an extremely difficult task. With the development of the Electronic Imaging System,
installed in J-9 irradiation channel of the IEN/CNEN Argonauta Reactor, it is possible to visualize the different
types of two phase air-water flows in small-diameter metallic pipes. After developing the captured image the
liquid-gas drift flux correlation as well as the void fraction in relation to the injected air outflow for a fixed
water outflow can be obtained
A technique to correct outlier pixels in images acquired with CCD-based cameras
No full textImages acquired with CCD-based cameras usually contain some spots or regions which do not match with their
neighbourhood, even when focusing a homogeneously illuminated surface of homogeneous colour. This
behaviour, caused by different responses of the CCD elements to red, blue and green light, is specially
noticeable in the case of high sensitivity cameras where even in complete darkness some bright spots still
appears. A technique has been developed in this work to correct defective or outlier pixels in the stored image,
making thus possible to retrieve a cleaner and improved picture afterwards. It is based on the determination of a matrix of defects, obtained from the camera response to complete darkness, after a criterion which takes into
account the deviation of red, green and blue (RGB) values from the corresponding average values occurring in a selected region of acceptable homogeneity. When the camera operates in the normal fashion, focusing an
illuminated object, the defective pixels would exhibit naturally other RGB values. Yet, as a systematic error, the
matrix of defects keeps its pattern, and hence, the defective pixels, even if not clearly identifiable in the image,
are obviously unreliable. Therefore, their RGB values are replaced by average numbers computed from the
surrounding pixels, excluding those ones which are themselves, as well, defectives. All these operations are
automatically carried out by an algorithm written in Fortran language, fed by matrices containing the images to
be cleaned up, and the matrix of defects
Optimization of radiological procedures on the practices of Argonauta reasearch reactor
No full textThe objectives of this work are the evaluation of the gamma and neutron doses derived from operations of
Argonauta reactor at 340 watts power, with emphasis in gamma dose outside the reactor room, in front of the main irradiation channel (J-09), when it is opened, so that the efficiency of the additional shield built in front this channel, can be evaluated and compared with values measured before; as well as to bringing up to date related in the radiological protection procedures for this facility and to train radiological protection staff to work in this area in Argonauta reactor, mainly at 340 watts power
Estados limite de componentes mecânicos considerando encruamento cinemático limitado
Get PDFIn this work, the problem of shakedown is considered for Mises material structures but, with limited kinematic hardening. Stein's overlay model is used for formulation and solution of the problem. It is shown that the algorithm, originally developed for elastic perfectly plastic materials, can be used when hardening is considered. Analytical solutions developed for a restrained block are extended here for the case of hardening in plane stress, allowing the validation of numerical results. Bench marks are used to check numerical results in plane stress and axissimetric problems. This examples intend to validate the theory and its implementation and also a progressive treatment of more complex structures, aiming to approach industrial level.Neste trabalho o problema da acomodação elástica de enfocado, para estruturas constituídas de materiais de Mises, porém com a consideração do encruamento cinemático limitado. O modelo de camadas de microelementos de Stein é utilizado para a formulação e solução do problema e é mostrado que o algoritmo já desenvolvido para o caso de elastoplasticidade ideal, pode ser utilizado também no caso com encruamento. As soluções analíticas, desenvolvidas para o problema de um bloco com restrições, são estendidas para o caso com encruamento e permitem a validação dos resultados numéricos em tensão plana. Comparações com resultados da literatura são levadas a efeito, tanto em tensão plana quanto em problemas com simetria de revolução. Estes exemplos visam à validação da teoria e sua implementação e também o tratamento de estruturas mais complexas que se aproximem progressivamente do nível das aplicações industriais
New Argonauta core reactor using rod fuel elements
No full textThis paper presents a way to modify the Argonauta core reactor which actually uses plate fuel elements with uranium enriched to 20% in U235 to a more feasible rod fuel elements using the Angra I pellets with 3.4% of enrichment (U235). Due to the difficulty to obtain uranium with the original enrichment to substitute, as the reactor safety imposes, the original Argonauta plates with pit corrosions and staunchness problems, this paper proposes a new core using rod fuel element. Those strong structural and feasible fuel elements permit to increase the power of the reactor to the limit of his actual external shielding and thermo hydraulic core reactor system. To calculate the criticality coefficient of this reactor and its neutron flux distribution, the finite element discretization of the diffusion equation is used. First, a reactor calculation with original plates configuration is presented as a numerical benchmark calculation, using two groups of neutron energies and three regions: fuel, water and graphite
Investigation of the water content in concrete for nuclear reactor shielding using neutron radiography analysis
No full textConcrete constructions for the shielding of nuclear reactors are big and made of large volumes of material
generally larger than those required for structural purposes only. This is due to the need of providing
simultaneous shielding to the gamma and neutron radiation emanating from the active core of the nuclear
reactors. Usually larger than normal amounts of water are added to the concrete mix used for radiation shielding
so that after the cure a greater quantity of water is retained in the concrete porosities, what is important for the
attenuation of the radiation. There still remains, however, an uncertainty regarding the quantity of water that is
actually retained in the concrete after its complete cure in 28 days and drying. As the percentage of water in the
concrete mix is usually the minimum required for the concrete to achieve a pre-specified resistance and, on the
other hand, a slight increase of this threshold is desirable for the improvement of the concrete radiation shielding property, further investigations are necessary to provide useful information to the structural designers. The objective of this work is to investigate this issue performing neutron radiography analyses of dry-laminated
mortars samples irradiated in the main irradiation channel of the Argonauta reactor installed at the Instituto de
Engenharia Nuclear-IEN/CNEN, Brazil. The analyses showed that it was possible to increase the water content
in dry ordinary concrete by 3.43% by increasing the water content in the concrete mixture by 20%. The
incorporation of 3.43% of additional water to the concrete seems to be enough for the shielding purpose, in
order to reach the minimum quantity of 7% of total water, because, usually, the ordinary concretes already have
in its composition 2 to 5 % of water in weight