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Time evolution simulation of heat removal in a small water tank by natural convection
Get PDFOne of the cooling modes for any source of heat such as in a shutdown nuclear core is the natural convection. The design specifications of any cooling pool can only be done when the removal heat rate and the corresponding mass flow rate is reasonably established. In our simulation scheme, we assumed that the body forces acting in the cubic water cell are: the weight, the drag force and the integrated pressure forces on the horizontal surfaces, the viscosity shear forces on the vertical surfaces and also a special viscosity drag force due to the mass dislocation along a Bernoulli type current tube outside the motive region. For a suitable time step, the uprising convection velocity is determined by an implicit and also by an explicit solution algorithm. The resulting differential equation depends on updating specific mass, dynamic viscosity and constant pressure heat coefficient with the last known temperature in the cell that absorbed heat. Numerical calculation software was performed using MATLAB’s technical computing language and then applied for a heat generation plate simulating a spent fuel assembler from a shutdown nuclear core. The results show time evolution of convection, terminal velocity and water temperature distribution. Pool dimension as well as pool level decrement are also determined for various air exhausting system conditions and heat rate of the spent fuel plate being cooled
Modeling of the dispersion of tritium from postulated accidental releases from nuclear power plants
Get PDFThis study has the aim to assess the impact of accidental release of tritium postulate from a nuclear power reactor through environmental modeling of aquatic resources. In order to do that it was used computational models of hydrodynamics and transport for the simulation of tritium dispersion caused by an accident in a CANDU reactor located in the ongoing Angra 3 site. It was postulated, then, the LOCA – Loss of coolant accident –, accident in the emergency cooling system of the nucleus ( without fusion), where was lost 66m³ of soda almost instantaneously. This inventory contained 35 PBq and was released a load of 9.7 TBq/s in liquid form near the Itaorna beach, Angra dos Reis –Rj. The models mentioned above were applied in two scenarios ( plant stopped or operating) and showed a tritium plume with specific activities larger than the reference level for seawater (1.1MBq/m³), during the first 14 days after the accident. The main difference between the scenario without and with seawater recirculation (pumping and discharge) is based on the enhancement of dilution of the highest concentrations in the last one. This dilution enhancement resulting in decreasing concentrations was observed only during the first two weeks, when they ranged from 1x109 to 5x105 Bq/m³ close to the Itaorna beach spreading just to Sandri Island. After 180 days, the plume could not be detected anymore in the bay, because their activities would be lower than the minimum detectable value (<11 kBq/m³)
Modeling and control of a nuclear power plant using AI techiniques
Get PDFIn pressurized water reactor (PWR) nuclear power plants (NPPs) pressure control in the primary loops is fundamental for keeping the reactor in a safety condition and improve the generation process efficiency. The main component responsible for this task is the pressurizer. The pressurizer pressure control system (PPCS) utilizes heaters and spray valves to maintain the pressure within an operating band during steady state conditions, and limits the pressure changes during transient conditions. Relief and safety valves provide overpressure protection for the reactor coolant system (RCS) to ensure system integrity. Various protective reactor trips are generated if the system parameters exceed safe bounds. Historically, a proportional-integral-derivative (PID) controller is used in PWRs to keep the pressure in the set point, during those operation conditions. The purpose of this study is to develop fuzzy controllers for the PWR pressurizer modeled by an artificial neural network (ANN) and compare their performance with conventional ones. Data from a 2785 MWth Westinghouse 3-loop PWR simulator was used to test both the conventional and the fuzzy controllers. The simulation results show that the fuzzy controllers have better performance compared with conventional ones
Implementation of a Metrology Programme to provide traceability for Radionuclides Activity measurements in the CNEN Radiopharmaceuticals Producers Centers
Get PDFThe commercialization and use of radiopharmaceuticals in Brazil are regulated by Agência Nacional de Vigilância Sanitária (ANVISA) which require Good Manufacturing Practices (GMP)certification for Radiopharmaceuticals Producer Centers. Quality Assurance Program should implement the GMP standards to ensure radiopharmaceuticals have requirements quality to proving its efficiency. Several aspects should be controlled within the Quality Assurance Programs, and one of them is the traceability of the Radionuclides Activity Measurement in radiopharmaceuticals doses. The quality assurance of activity measurements is fundamental to maintain both the efficiency of the nuclear medicine procedures and patient and exposed occupationally individuals safety. The radiation doses received by patients, during the nuclear medicine procedures, is estimated according to administered radiopharmaceuticals quantity. Therefore it is very important either the activity measurements performed in radiopharmaceuticals producer centers (RPC) as the measurements performed in nuclear medicine services are traceable to national standards. This paper aims to present an implementation program to provide trace ability to radionuclides activity measurements performed in the dose calibrators (well type ionization chambers) used in Radiopharmaceuticals Producer Center placed in different states in Brazil. The proposed program is based on the principles of GMP and ISO 17025 standards. According to dose calibrator performance, the RPC will be able to provide consistent, safe and effective radioactivity measurement to the nuclear medicine services
Processamento de cartuchos de impressoras de jato de tinta: um exemplo de gestão de produto pós-consumo
No full textAvaliação de serviços oferecidos por bibliotecas: o caso da biblioteca do Instituto de Engenharia Nuclear - IEN
No full textEsta pesquisa tem por objetivo a proposição e aplicação de um modelo para a avaliação da satisfação dos usuários de uma biblioteca especializada, com respeito aos serviços prestados pela mesma. Uma extensa revisão da literatura nas bases Scientific Electronic Library Online - SciELO, Scopus e ISI Web of Science foi desenvolvida a fim de dar suporte à construção de um modelo para a avaliação dos serviços oferecidos por bibliotecas. Esta revisão foi especialmente útil para definir o conjunto de critérios de avaliação e para a elaboração do questionário aplicado em uma amostra composta por usuários de uma biblioteca especializada na área de tecnologia nuclear, neste caso, a do Instituto de Engenharia Nuclear – IEN. Como consequência, este trabalho pretendeu analisar os resultados visando a melhoria da qualidade dos serviços oferecidos. A amostra desta pesquisa foi composta por 117 respondentes dentre os quais retornaram 94 formulários. Como resultado, os dados coletados indicaram que os critérios nos quais a biblioteca teve melhor desempenho foram a conservação e a adequação do acervo. Por outro lado, os resultados também mostraram que os critérios atualização e cobertura internacional do acervo foram os que demandaram maior prioridade de ações de melhoria, visto que tiveram baixo desempenho e foram considerados de alta importância para os respondentes.This research aims to propose a model for evaluating the satisfaction of the users of a specialized library, regarding the library services. An extensive literature review on the bases Scientific Electronic Library Online - SciELO, Scopus and ISI Web of Science was developed to support the construction of a model for the evaluation of the services offered by libraries. This review was especially useful to define the set of evaluation criteria and to prepare the questionnaire on a sample of users of a library specialized in the field of nuclear technology, in this case, the Institute of Nuclear Engineering – IEN. Consequently, this work intended to analyze the results to improve the quality of offered services. The sample was composed of 117 respondents of whom 94 returned forms. As a result, the collected data have indicated that the criteria on which the library best performed were the conservation and adequacy of the collection. Moreover, the results also have shown that the update criteria and international coverage of the collection are the ones have greater priority while promoting improvement actions, since they were perceived as having low performance and high importance by the respondents
Eletromagnetic field calculations using edge finite elements
No full textO objetivo deste trabalho _e se obter uma melhor representação dos campos eletrostáticos e magnetostáticos principalmente no caso de potenciais vetoriais em 3D. Utiliza-se para isto uma formulação integral das equações de Maxwell como também o método dos elementos finitos vetoriais para discretizar o modelo geométrico e os potenciais vetoriais eletrostáticos e magnetostáticos. Esta formulação foi implementada numa versão do programa MEF intitulada EDGE program. Entre os exemplos numéricos apresentados estão as guias de ondas onde os elementos finitos escalares apresentam soluções espúrias
Propagation speed of Rγ-511 keV in plastics
No full textThe propagation speed (PS) of visible light -a small frequency range in the large frame of electromagnetic radiations (ER)- in air was measured, during the last hundred years(1), using a great deal of different methods, with high precision results being achieved. Further improvements of detection and electronic measuring systems allowed to determine such parameters as PS by using Rγ (2,3,4,5,6,7) with an advantage that such experiments could also be performed in a larger variety of propagation media non-transparent to visible light. In this context, beside our already performed measurements in air(7), in a good extent comparable to the CODATA value(8), we extended such measurements in plastics as a propagation media. As already well settled(2-7), to perform such PS measurements the availability of a Rγ source in which two Rγ are emitted simultaneously in opposite directions turns out to be essential to the feasibility of the experiment, as far as no reflection techniques could be used. Such suitable source, in all cases, was the positron emitter 22Na placed in a metal container in which the positrons are stopped and annihilated when reacting with the medium electrons, in such way originating -as it is very well established from momentum/energy conservation laws(9)- two Rγ-511 keV each, both emitted simultaneously in opposite directions
Eletromagnetic Field Calculations using Edge Finite Element
No full textESTE RELATÓRIO E PARA USO EXCLUSIVO DO INSTITUTO DE ENGENHARIA NUCLEAR
O direito a utilização de informações relacionadas ao trabalho de pesquisa realizado no IEN ́e limitado aos servidores da CNEN e pessoal de organizações associadas, nos limites dos termos contratuais que regem os respectivos convênios. O conteúdo dos relatórios não pode ser separado ou copiado sem autorização escrita do IEN.The objective of this work is to obtain an electrostatic and a magnetostatic eld representation mainly in the case of
vector potentials (3D). To do that, an integral formulation of Maxwell equation is used as well the Vectorial Finite
Element Method to discretize the geometric model and the eletrostatic and magnetostatic vector potentials. This
formulation was implemented in the MEF program entitled EDGE program. Among the numerical examples, this
work presents the solution of wave guides using the edge nite element and compare the results with the scalar nite
elements in the case of homogeneous wave guides. In the case of inhomogeneous waveguide a mixing vector and
scalar nite element is used. The vector nite element representing the transversal eld and the nodal nite element
representing the longitudinal eld
