LEANDRO GOULART DE ARAUJO
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Artigo IPEN-doc 27907 Brazilian clays for environmental solutions applied to radioactive waste management2021 - MACHADO, G.G.; KRUPSKAYA, V.V.; ZAKUSIN, S.V.; HARADA, J.; VICENTE, R.; SOUZA, R.P.; ARAUJO, L.G.; MONTALVAN, E.T.; ESPINOSA, D.C.R.; KAHN, H.; GUILHEN, S.N.Clayey materials have been adopted in most nuclear waste producing countries as a key constituent in engineered barrier systems for final disposal facilities at all levels of radioactive wastes (LILW-SL, LILW-LL, and HLW). The following study presents a thorough characterization upon five Brazilian clay-rich deposits, mostly smectite bearing clays, aiming to evaluate their expected performance as barrier under the conditions associated to a Low and Intermediate Level Waste Repository; being the former a matter of national strategic interest. Samples coming from the Brazilian states of Paraná, Bahia, Paraíba, and Maranhão were treated and analyzed by means of X-Ray diffraction as main technique. Other techniques such as FTIR, LALLS, XRF, and SEM-EDS, were performed in order to establish the mineralogical composition, particle size distribution, and chemical composition. Moreover, several standard clay treatments over the <1 μm size fraction were carried out to reveal information regarding layer charge, major interlayer cations, unit formula and other crystal features of smectite species present in a mineralogical assembly, aiming to provide information for the construction of a molecular model over which would be realistic to simulate the diffusion of radionuclides. Results obtained on 133Cs adsorption experiments indicate that mineralogical composition would probably be the single most influential factor controlling transport capacity of positively charged radionuclides in the current setup. The composition is especially expressed in terms of smectite contents, favoring montmorillonite rich materials containing majorly Na+ as compensating cation in interlayer position. All tested samples can be considered as suitable candidates to be used in the design of final destination storage for nuclear waste. Thus, efficiency on 133Cs adsorption trials also indicate that these materials could have potential uses as sorptive matrices (Sorbents) for water treatment of radionuclide polluted waters such as TENORM waste waters. However, these trends are yet to be contrasted against hydraulic conductivity measurements and swelling pressure in order to have a more comprehensive perspective of this clayey prospects as barrier enhanced layer; aligned to the multilayer barrier system approach for nuclear waste management.Artigo IPEN-doc 27884 Preliminary studies on electron beam irradiation as a treatment method of radioactive oil sludge2021 - TESSARO, A.P.G.; VICENTE, R.; MARUMO, J.T.; TEIXEIRA, A.C.S.C.; ARAUJO, L.G.Radiation-induced advanced oxidation processes have been proposed for the treatment of various types of wastes. However, electron beam technologies for the removal of recalcitrant compounds in petroleum wastes are still poorly understood. This work aims at evaluating the effects on the degradation of organic matter from oil sludge by electron beam irradiation. Characterization methods were employed to identify the chemical elements present in the waste. Radiometric analysis was performed to identify radionuclides and measure dose rates. Preliminary immobilization of the untreated waste with cement indicated resistance values very close to the minimum established in national regulation. To treat the waste, an electron beam accelerator, model Dynamitron II, with variable current up to 25 mA was employed and the irradiation doses ranged from 20 to 200 kGy. Solutions were prepared with an initial H2O2 concentration of 1.34 mol·L-1. The effects on the removal of total organic carbon are discussed.