LEANDRO GOULART DE ARAUJO
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Artigo IPEN-doc 27759 Computational fluid dynamic simulation of a gas-solid fluidized bed system2019 - OLIVO-ARIAS, L.P.; ARAUJO, L.G. de; ROJAS-TRIGOS, J.B.The study of the gas-solid system was performed through an analysis of computational fluid dynamics (CFD) in a fluidized bed reactor. This process begins with the interaction between the particles and the gas phase. The fluidization process analysis is achieved through the Eulerian approach represented in the behavior of the solid phase dynamics during the bed expansion process. Within the process, the formation of the dense phase was demonstrated and how it could affect the effects of temperature, pressure and surface velocity of the gas in the fluidized bed system. The purpose of this work is to establish hydrodynamic parameters by evaluating the volumetric fraction of the particles and the axial and radial velocity profile using the drag models of Syamlal O'Brien and Gibilaro. In addition, it should be considered the analysis of the computational dynamics of fluids, such as the generation of the mesh, the selection of the models, and the run time of the simulation. The results of the simulations showed that the solid phase concentration has had a uniform distribution, a dense phase formation, given the changes in operating conditions and a reasonable expansion of the bed in the final simulation time.Artigo IPEN-doc 26681 Radiochemical characterization of spent filter cartridges from the primary circuit of a research reactor2019 - GERALDO, BIANCA; ARAUJO, LEANDRO G. de; TADDEI, MARIA H.T.; FERREIRA, MARCELO T.; MADUAR, MARCELO F.; VICENTE, ROBERTO; MARUMO, JULIO T.Radiochemical-based analyses have been used for the characterization of radioactive waste. Nevertheless, the determination of alpha, beta and gamma emitters by radiochemical analysis of spent cartridge filters from a swimming-pool type reactor has not been previously addressed. This work aims at identifying and quantifying the radionuclides present in this waste, including the difficult to measure radionuclides. The distribution of the radionuclides in the filter was investigated by the determination of gamma-emitting nuclides and the z-score of the measured activity concentrations. The results indicated that all the filters are homogeneous, meeting the homogeneity criteria recommended by the International Atomic Energy Agency.Artigo IPEN-doc 25196 Reaction of ion exchange resins with Fenton's reagent2018 - ARAUJO, LEANDRO G. de; MARUMO, JULIO T.One of the most common treatment methods for spent ion exchange resins is their immobilization in cement, which reduces the release of radionuclides into the environment. Although this method is efficient, it considerably increases the final volume of the waste due to its low incorporation capacity. This work aims to evaluate the degradation of ion exchange resins by the Fenton process (H2O2/Fe (2+)). The resin evaluated was a mixture of cationic and anionic resins, both non-radioactive. The reactions were conducted by varying the catalyst concentration (25, 50, 100, and 150 mmol L-1) and the volume of hydrogen peroxide. Three different temperatures were evaluated by varying the flow of reactants, which were 50, 60, and 70 degrees C. Cement specimens were prepared from the treated solutions and two parameters were assessed-namely, final setting time and axial compressive strength. The results showed that the experimental conditions were suitable to dissolve the resins, and the Fe3+ produced as precipitate during the experiments increased the resistance of the final product. The immobilized product complied with the limits established by regulation.