ERIKI MASAHIKO TAKARA

ERIKI MASAHIKO TAKARA

Página do item completo

Resultados de Busca

Agora exibindo 1 - 6 de 6

Nickel electrodeposition in LEU metal foil annular targets to produce Mo-99
2022 - IANELLI, RICARDO F.; SALIBA-SILVA, ADONIS M.; TAKARA, ERIKI M.; GARCIA NETO, JOSE; SOUZA, JOSE A.B.; CARVALHO, ELITA F.U. de; DURAZZO, MICHELANGELO
The most used production route of Mo-99 is through the fission of U-235 in irradiation targets that are irradiated in research reactors. The annular target is a promisor design since it can incorporate high U-235 quantities, thus increasing the production yield of Mo-99. This target type uses a foil of uranium metal enveloped by a thin nickel foil that acts as a diffusion barrier. The process of uranium enveloping with nickel foil is today done manually. This operation risks the nickel foil breaking up during target assembling. In the present work, we studied the nickel electrodeposition over uranium metal foil surfaces to replace nickel foils. A pre-forming procedure of the uranium metal foil by calendering was developed to facilitate the assembling operation. The electrodeposition was done over the uranium foil pre-conformed in a tubular shape. An automated apparatus for electrodeposition of nickel in uranium tubular-shaped foil was developed. The results showed that the high nickel adherence to uranium metal depends on the proper activation of the uranium surface. Among the activation processes studied, the mechanical activation showed good adhesion of the nickel layer, with a loss of only 0.16% of uranium mass. Homogeneous and regular 12 μm thickness electrodeposited layers over the uranium metal were obtained. This work showed that the process could be used in continuous production technology, such as the production of irradiation targets.
Manufacturing LEU-foil annular target in Brazil
2022 - DURAZZO, MICHELANGELO; SOUZA, JOSE A.B.; IANELLI, RICARDO F.; TAKARA, ERIKI M.; GARCIA NETO, JOSE S.; SALIBA-SILVA, ADONIS M.; CARVALHO, ELITA F.U. de
Molybdenum-99 is the most important isotope because its daughter isotope, technetium-99m, has been the most used medical radioisotope. The primary method used to produce Mo-99 derives from the fission of U-235 incorporated in so-called irradiation targets. Two routes are being developed to make Mo-99 by fissioning with low enriched uranium (LEU) fuel. The first adopts UAlx-Al dispersion plate targets. The second uses uranium metal foil annular targets. The significant advantage of uranium foil targets over UAlx-Al dispersion targets is the high density of uranium metal. This work presents the experience obtained in the development of the uranium metal annular target manufacturing steps. An innovative method to improve the procedure for assembling the uranium foil on the tubular target was presented. The experience attained will help the future production of Mo-99 in Brazil through the target irradiation in the Brazilian Multipurpose Reactor (RMB).
Desenvolvimento de sistema de controle para aparato de soldagem por atrito rotativo
2021 - KENIG, GABRIEL; TAKARA, ERIKI M.; KANESHIRO, PERCY J.I.; NASCIMENTO, JESSICA C.; GARCIA NETO, JOSE dos S.; KANASHIRO, LUIS R.; ASATO, OSVALDO L.; NAKAMOTO, FRANCISCO Y.
The friction rotary welding (FRW) is a solid state material welding method that is able to weld not only similar but dissimilar materials as well. The FRW allows the union between two pieces of metal converting mechanical energy into thermal welding. The friction generated by the rotational momentum between the two surfaces generates enough heat to fuse the materials without reaching the fusion temperature, this mechanical connection can be done through atomic diffusion. The equipment needed to perform the FRW process needed a new control system. This paper presents the development of this new control system through a top-down approach based on successive refinement using modeling tools developed to model dynamic systems to discrete events. The result presented in this paper is the control system algorithm in Enhanced Mark Flow Graph, a high level Petri Net derivative and a systematic to map the model in C++ in order to use it in a PIC microcontroller.
Kinects and factors on chemical dissolution of aluminum alloy AA6061 in NaOH alkaline media
2020 - TAKARA, E.M.; SOUZA, J.B. de; CARVALHO, E.F.U.; SILVA, A.S.
Nuclear Medicine is the Field of science that uses radioactive materials in order to diagnose and treat human body deceases. One of the most used radioisotopes for images diagnose purpose is the metastable technetium-99 (99mTc) because of its low decay half life (6 hours) and energy emission of 140keV that ensures low exposition time with the capacity of generating high quality images. The 99mTc is generated by the molibdenum-99(99Mo) radioactive decay during about 66 hours. The 99Mo is fabricated via nuclear fission of low encriched uranium (LEU) through plate irradiation targets (UAlx). The irradiation target cladding is made of Aluminum alloy AA6061 and its substrate is composed by 235U powder scattered in an AA1050 matrix. In general, studies are made targeting the prevention of corrosion mechanisms but the chemical dissolution in alkaline media, under hot cells, are one of the steps required for the post-processing methods of irradiation targets The time spent after irradiation is an important factor because the half life radioactive decay of the produced radioisotopes is relative short, then the procedures of dissolution, extraction, purify and distribution must be optimized in order to increase efficiency. This work presents a study of the factors impact involved on the chemical dissolution of the cladding aluminum alloys (temperature, NaOH solution concentration and dissolution time) as well as the kinects of the process associating it with the formation and destruction of oxides using electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). It was found that the involved parameters contribute individually more effective and that there is no relevant association between the factors. Solution temperature showed to be the most influent factor following by exposition time. It was presented a equivalent circuit model which demonstrates the reaction kinects and the growing of passive layers that slow down the process before it turns up into a soluble phase.
Dissolução eletroquímica de ligas de alumínio em solução alcalina aplicadas ao pós tratamento de alvos de irradiação
2020 - TAKARA, ERIKI M.
O tecnécio-99 metaestável (99mTc) é o radioisótopo mais utilizado nos diagnósticos por imagem devido à sua meia-vida curta de aproximadamente 6 horas e emissão de energia de 140keV. O 99mTc é gerado através do decaimento radioativo do isótopo molibdênio-99 (99Mo) que possui meia vida de aproximadamente 66 horas. Atualmente, 100% de todo 99Mo utilizado como matéria prima no país é importado sendo que dentre as rotas utilizadas para a produção do 99Mo, encontra-se o método da fissão nuclear de urânio de baixo enriquecimento (LEU) por meio de irradiação de alvos do tipo placa (UAlx). Uma das etapas após irradiação consiste na dissolução das ligas de alumínio que compõem o invólucro e a dispersão do núcleo através do procedimento comercial utilizado atualmente que é a dissolução puramente química, à quente, em soluções alcalinas de NaOH. Neste trabalho, estudou-se a influência dos fatores envolvidos na dissolução química (temperatura, concentração da solução de NaOH e tempo de dissolução) comparando-as com a adição de polarização do alvo, a fim de se aumentar a taxa de dissolução e diminuir, dessa forma, o tempo global de pós processamento dos alvos. Verificou-se que a temperatura da solução é o fator mais relevante tanto na dissolução química quanto na dissolução aplicando polarização anódica ou catódica. A presença da polarização pode auxiliar no processo de dissolução dependendo das condições de pH e potencial aplicado, porém, tecnologicamente não apresentou uma redução considerável no tempo de dissolução dos alvos.
Estudos de proteção anticorrosiva sobre eletrodos de níquel e de aço ABNT-316L destinados à eletrólise alcalina da água por EIE
2016 - TAKARA, ERIKI M.; SILVA, ADONIS M.S.