LEANDRO GOULART DE ARAUJO

LEANDRO GOULART DE ARAUJO

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Biosorption of uranium from aqueous solutions by Azolla sp. and Limnobium laevigatum
2022 - ARAUJO, LEANDRO G. de; VIEIRA, LUDMILA C.; CANEVESI, RAFAEL L.S.; SILVA, EDSON A. da; WATANABE, TAMIRES; FERREIRA, RAFAEL V. de P.; MARUMO, JULIO T.
The main goal of this study was to assess alternatives to the current challenges on environmental quality and circular economy. The former is here addressed by the treatment of radioactively contaminated solutions, and the latter by using abundant and low-cost biomass. In this paper, we examine the biosorption of hexavalent uranium (U(VI)) in a batch system using the macrophytes Limnobium laevigatum and Azolla sp. by three operational parameters: biomass dose, metal ion concentration, and contact time. Simulated solutions were firstly addressed with two biomasses, followed by studies with real liquid organic radioactive waste (LORW) with Azolla sp. The batch experiments were carried out by mixing 0.20 g biomass in 10 mL of the prepared solution or LORW. The total contact time employed for the determination of the equilibrium times was 240 min, and the initial U(VI) concentration was 0.63 mmol L−1. The equilibrium times were 15 min for L. laevigatum and 30 min for Azolla sp. respectively. A wide range of initial U(VI) concentrations (0.25–36 mmol L−1) was then used to assess the adsorption capacity of each macrophyte. Isotherm models validated the adsorption performance of the biosorption process. Azolla sp. presented a much higher U(VI) uptake (0.474 mmol g−1) compared to L. laevigatum (0.026 mmol g−1). When in contact with LORW, Azolla sp. removed much less uranium, indicating an adsorption capacity of 0.010 mmol g−1. In conclusion, both biomasses, especially Azolla sp., can be used in the treatment of uranium-contaminated solutions.
Synthesis of geopolymers for immobilization of radioactive waste using sewage treatment plant sludge
2021 - CASAS, A.; ARAUJO, L.; GARCIA, R.; VICENTE, R.; FRANCO, M.; MARUMO, J.
An algorithmic software model for the characterization of radioactive waste
2021 - TESSARO, ANA P.G.; ARAUJO, LEANDRO G. de; TSUTSUMIUCHI, VICTOR K.; OLIVEIRA JUNIOR, JULIO de; VICENTE, ROBERTO
Non-consolidated information base, repetitive work, and data unreliability are some of the issues that may hamper a radioactive waste characterization program. Therefore, an algorithmic software model for the characterization of radioactive waste is proposed to boost waste management in nuclear-based facilities. The data obtained have enabled the construction of a guide code in the pseudotechnical language. The developed system fully covered the characterization stage, and met the needs identified in the radioactive waste management service. Here, we propose systematic documentation of the characterization methods that are employed during the radioactive waste management processes, besides formulating the system’s data recording.
Thermal plasma technology for radioactive waste treatment
2020 - PRADO, EDUARDO S.P.; MIRANDA, FELIPE S.; ARAUJO, LEANDRO G. de; PETRACONI, GILBERTO; BALDAN, MAURICIO R.
In this paper, a review of radioactive wastes treatment using thermal plasma technology is presented as a treatment method for radioactive waste management.Virtually all waste streams can be treated by the thermal plasma technologies, resulting in a conditioned product, free from organics and liquids, definitely meeting the acceptance criteria for safe storage and disposal. The application of the thermal plasma system in the nuclear area is still one of the current research topics due to the theoretical and practical complexity of the treatment. This paper discusses the performance of the thermal plasma systems, addressing the advantages and limitations of the method.
Inventorying the radionuclides in spent cartridge filters from the primary circuit of a nuclear research reactor by the dose-to-activity method
2020 - TESSARO, ANA P.G.; ARAUJO, LEANDRO G. de; VICENTE, ROBERTO
The high activity of spent cartridge filters from the cooling water polishing system of a nuclear research reactor precludes, in routine work of a waste characterization program, the usual method of radiochemical analysis of filter samples. For this waste, the dose-to-activity method, using a gamma spectrometer and a dose rate meter, is an alternative for the determination of the activities of the gamma emitters with acceptable accuracy. The ratio of photon peak-areas from different radionuclides, corrected by the detector energy-dependent efficiency, allowed estimating the proportions between the activities of the different radionuclides present. Finally, the simulation of the counting geometry, using the point-kernel method to estimate the air dose rate resulting from an arbitrary concentration of those radionuclides and the comparison of the calculated with the measured air dose rate have yielded the needed estimates of the activity concentrations. The aim of this paper is to report the development of the method applied for the determination of the concentration of the gamma-emitters present in cartridge filters from the IEA-R1 Nuclear Research Reactor.
Radiochemical characterization of spent filter cartridges from the primary circuit of a research reactor
2019 - 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.
Chemical analysis of radioactive mixed liquid wastes by alpha/gamma spectrometry, ICP-OES and arsenazo III
2013 - FERREIRA, EDUARDO G.A.; FERREIRA, RAFAEL V.P.; ARAUJO, LEANDRO G.; TADDEI, MARIA H.T.; DELLAMANO, JOSE C.; MARUMO, JULIO T.