GIOVANNI LARANJO DE STEFANI

GIOVANNI LARANJO DE STEFANI

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Parametric study for enhancing the radioisotope production in the IEA-R1 research reactor
2021 - STEFANI, GIOVANNI L. de; GENEZINI, FREDERICO A.; SANTOS, THIAGO A. dos; MOREIRA, JOAO M. de L.
In this work a parametric study was carried to increase the production of radioisotopes in the IEA-R1 research reactor. The changes proposed to implement in the IEA-R1 reactor core were the substitution of graphite reflectors by beryllium reflectors, the removal of 4 fuel elements to reduce the core size and make available 4 additional locations to be occupied by radioisotope irradiation devices. The key variable analyzed is the thermal neutron flux in the irradiation devices. The proposed configuration with 20 fuel elements in an approximately cylindrical geometry provided higher average neutron flux (average increment of 12.9 %) allowing higher radioisotope production capability. In addition, it provided 4 more positions to install irradiation devices which allow a larger number of simultaneous irradiations practically doubling the capacity of radioisotope production in the IEA-R1 reactor. The insertion of Be reflector elements in the core has to be studied carefully since it tends to promote strong neutron flux redistribution in the core. A verification of design and safety parameters of the proposed core was carried out. The annual fuel consumption will increase about 17 % and more storage space for spent fuel will be required.
STC-MOX-Th
2020 - SANTOS, THIAGO A. dos; STEFANI, GIOVANNI L. de
O trabalho trata da criação de um programa elaborado em ambiente MATLAB que calcula os limites térmicos de projeto de um típico reator a água pressurizada (PWR), que é a temperatura central da pastilha combustível e a taxa de ebulição nucleada (DNBR). Outras distribuições de temperatura e grandezas hidrodinâmicas do líquido refrigerante, como a entalpia e a queda de pressão também são calculadas. O código possui peculiaridades, como o fato de permitir cálculos com combustíveis de UO2 puro e proporções do óxido misto de Urânio/Tório - MOX (U,Th). Estas, além da sua interface amigável com o usuário provam que o código pode ser utilizado em trabalhos de pesquisa , bem como em disciplinas de graduação e pós graduação voltadas ao estudo de termo-hidráulica de reatores nucleares em cursos de graduação e pós graduação de engenharia (nuclear e/ou da energia) espalhados pelos país, como no caso do curso de graduação de Engenharia de Energia da Universidade Federal do ABC, onde é uma disciplina optativa. Para a validação do código foram utilizados dados do reator AP-1000 da Westinghouse. O programa se apresentou com comportamento físico dentro do esperado para o modelo, gerando resultados confiáveis para eventuais projetos de reatores (validado com dados experimentais e outros programas), bem como propicia a alunos uma experiência diferenciada dentro da aprendizagem dos conceitos empregados na área, uma vez que o programa permite uma análise mais profunda de determinados conceitos na área de termo-hidráulica que dentro da aula expositiva e com exercícios convencionais não poderiam ser explorados.
Optimization on the core of IEA-R1 research reactor for enhance the radioisotopes production
2019 - STEFANI, GIOVANNI L. de; GENEZINI, FREDERICO A.; MOREIRA, JOÃO M. de L.; SANTOS, THIAGO A. dos
In this work a parametric study was carried out to increase the production of radioisotopes in the IEA-R1 reactor. One of the variables directly proportional to isotope production is the magnitude of the neutron flux in which some material is exposed, so the main objective of this work was to increase neutron flux, especially in the center of the reactor in the beryllium element irradiator (EIBe), within the operational and safety limits of the reactor. The study is initiated by defining a default configuration, in which core of the IEA-R1 reactor is modeled with all fresh fuel assemblies to ensure the reduction of variables that affect the data analysis, then para metric studies were performed evaluating, by comparative analysis of the behavior of the relation of neutron flux versus the fuel for the standard configuration. Therefore, another configuration was tested: the changes in the core of graphite reflecting elements for beryllium, as well as, the result due to reactor core compaction. Parameters such as the fraction of delayed neutrons (Beff) and temperature reactivity coefficient are analyzed to ensure that the configuration has the minimum safety requirements for the reactor safe operation. The results of the study demonstrate a large increase in neutron flux magnitude and in particular in the center of the nucleus in the beryllium irradiating element.
Feasibility to convert an advanced PWR from UO2 to a mixed (U,Th)O2 core
2017 - STEFANI, GIOVANNI L. de; MAIORINO, JOSE R.; MOREIRA, JOAO M. de L.; SANTOS, THIAGO A. dos; ROSSI, PEDRO C.R.
This work presents the neutronics and thermal hydraulics feasibility to convert the UO2 core of the Westinghouse AP1000 in a (U-Th)O2 core, rather than the traditional uranium dioxide, for the purpose of reducing long-lived actinides, especially plutonium, and generates a stock pile of 233U, which could in the future be used in advanced fuel cycles, in a more sustainable process and taking advantage of the large stock of thorium available on the planet and especially in Brazil. The reactor chosen as reference was the AP1000, which is considered to be one of the most reliable and modern reactor of the current Generation III, and its similarity to the reactors already consolidated and used in Brazil for electric power generation. The results show the feasibility and potentiality of the concept, without the necessity of changes in the core of the AP1000, and even with advantages over this. The neutron calculations were made by the SERPENT code. The results provided a maximum linear power density lower than the AP1000, favoring safety. In addition, the delayed neutron fraction and the reactivity coefficients proved to be adequate to ensure the safety of the concept. The results show that a production of about 260 Kg of 233U per cycle is possible, with a minimum production of fissile plutonium that favors the use of the concept in U-Th cycles.
Implementation of the optimization for the methodology of the neutronic calculation and thermo-hydraulic in IEA-R1 reactor
2011 - STEFANI, GIOVANNI L. de; CONTI, THADEU das N.; SANTOS, THIAGO A. dos; FEDORENKO, GIULIANA G.; CASTRO, VINICIUS A.; MAIO, MIREIA F.
Analise experimental do fenômeno de circulação natural no sistema monofásico
2011 - SANTOS, THIAGO A. dos; STEFANNI, GIOVANNI L. de; CONTI, THADEU das N.
Automatização do balanço térmico do circuito de circulação natural
2011 - SANTOS, THIAGO A. dos; STEFANNI, GIOVANNI L. de; CONTI, THADEU das N.