CLAUDIA GIOVEDI MOTTA

CLAUDIA GIOVEDI MOTTA

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Hydrogen mitigation
2024 - DE MICHELI, LORENZO; SILVESTRIN, G.; SOUZA, R.F.B. de; NETO, A.O.; GIOVEDI, C.
In the context of discussions surrounding the hydrogen economy, particularly its green aspects, ensuring safety in the production and storage of hydrogen is paramount. This is especially crucial when hydrogen mixes with air, comprising between 6% and 30% in volume, as it poses potential risks of explosions. A proven method to mitigate these dangers is the utilization of Passive Autocatalytic Recombiners (PARs). These devices facilitate the recombination of hydrogen with oxygen on active catalytic surfaces, leading to the generation of water vapour and heat [1], reducing significantly the risk of explosions. PARs are typically composed of materials like stainless steel, alumina, and silica, which support active catalytic elements such as platinum or palladium. To combat catalyst deactivation resulting from water accumulation, researchers have explored the use of hydrophobic materials [2], among which graphene stands out. Recent studies have demonstrated that graphene could be successfully applied directly on surface, [3], using a non-thermal plasma system. This method resulted in the production of a material with few layers and hexagonal structural defects, making it attractive due to its simplicity, low cost, and scalability. In this sense, graphene is a promising option fto be applied as hydrophobic coating in catalysts for PARs. This work investigated the formation of films of graphenoid materials doped with platinum or palladium on a sintered porous metal filter in a single step. X-ray diffraction experiments revealed high amorficity, with percentages of approximately 49.6% and 60.0% for materials containing platinum or palladium, respectively. The D1/G band ratios were 2.9 and 1.6 for materials with platinum or palladium, indicating the presence of structural defects. Contact angle measurements demonstrated strong hydrophobicity for both materials, with values of 124º and 119º, respectively. Catalytic tests showed that the palladium-based converter was able to remove 17% of the injected hydrogen, while the material containing platinum achieved a removal of around 23%, confirming the effectiveness of these coatings in converting hydrogen into water. The experimental results indicated that coating porous steel filters with graphene doped with catalytic metals represents a promising strategy to ensure safety and efficiency in converting hydrogen into green energy systems. This approach has significant implications for sustainability and corporate social responsibility practices.
Assessment of burnable poison reactivity in the ATF fuel assembly
2024 - ABE, A.; GIOVEDI, C.; CARLUCCIO, T.
Simulation of spacer grid static compression test using finite element models
2024 - SANTOS, R.S.B.; GIOVEDI, C.
Nuclear power plants
2024 - GIOVEDI, C.; ABE, A.Y.; OLIVEIRA, A.; DE MICHELI, L.
Best estimate plus uncertainty analysis of metal-water reaction transient experiment
2023 - AVELAR, ALAN M.; DINIZ, CAMILA; CAMARGO, FÁBIO de; GIOVEDI, CLAUDIA; ABE, ALFREDO; CHERUBINI, MARCO; PETRUZZI, ALESSANDRO; MOURÃO, MARCELO B.
Uncertainty analysis is applied in the licensing process for nuclear installations to complement best estimate analysis and to verify that the upper bound value is less than the threshold corresponding to the safety parameter of interest. Metal-water reaction is a critical safety phenomenon of water-cooled nuclear reactors at accident conditions, e.g. Loss-Of-Coolant Accidents (LOCA). AISI 348 cladding is able to increase the accident tolerance comparing to Zr-based alloys and differently from other accident tolerant fuel cladding options, there is operational experience of nuclear power plants with stainless steel. In this study, a transient oxidation experiment of AISI 348 by steam was conducted and the major sources of uncertainty were addressed. An evaluation model was developed to calculate the evolution of mass gain during the experiment. Meanwhile, uncertainty propagation of experimental data was performed. The results show that the mass gain predicted by the transient metal-water reaction model lays within the experimental data uncertainty band. Furthermore, the selection of the oxidation kinetics model seems to be important whether the analysis wills to provide conservative results.
Effectiveness of Ni-based and Fe-based cladding alloys in delaying hydrogen generation for small modular reactors with increased accident tolerance
2023 - AVELAR, ALAN M.; CAMARGO, FABIO de; SILVA, VANESSA S.P. da; GIOVEDI, CLAUDIA; ABE, ALFREDO; MOURAO, MARCELO B.
This study investigates the high temperature oxidation behaviour of a Ni–20Cr-1.2Si (wt.%) alloy in steam from 1200 °C to 1350 °C by Thermogravimetric Analysis (TGA), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS) and X-ray Diffraction (XRD). The results demonstrate that exposed Ni-based alloy developed a thin oxide scale, consisted mainly of Cr2O3. The oxidation kinetics obtained from the experimental results was applied to evaluate the hydrogen generation considering a simplified reactor core model with different cladding alloys following an unmitigated Loss-Of-Coolant Accident (LOCA) scenario in a hypothetical Small Modular Reactor (SMR). Overall, experimental data and simulations results show that both Fe-based and Ni-based alloys may enhance cladding survivability, delaying its melting, as well as reducing hydrogen generation under accident conditions compared to Zr-based alloys. However, a substantial neutron absorption occurs when Ni-based alloys are used as cladding for current uranium-dioxide fuel systems, even when compared to Fe-based alloys.
Neutronic screening of potential candidate for accident tolerant fuel
2020 - ABE, ALFREDO; GIOVEDI, CLAUDIA; MARTINS, M.
Analysis of stresses acting on the internal and external surfaces of fuel rod of a pressurized water reactor using computational simulation
2019 - LIMA, LEONARDO S.; MELO, CAIO; FARIA, DANILO P.; BERRETA, JOSE; ABATI, AMANDA; GIOVEDI, CLAUDIA
During operation of a Pressurized Water Reactor, the cladding of the fuel rod is subjected to various loads, such as: temperature, internal pressure, and external pressure which generate dimensional and geometric variations in the cladding tube. In the fuel rod, at the operating temperature, the internal pressure comes from the initial pre-pressurizing with Helium gas and the release of fission gases by the UO2 pellets during the irradiation. The external pressure is assumed to be the same as that of the coolant. In this paper, it was proposed the study of a mathematical model for computational simulation using the Finite Element Method to calculate and analyze the mechanical stresses acting on the internal and external surfaces of the fuel rod, adopting the normal operating condition, at 0 W of power. The boundary conditions, such as temperature and pressure profile, come from a modified version of a fuel performance code, considering as cladding material an iron-based alloy (austenitic stainless steel). The fuel rod was modeled and simulated using the Solidworks and ANSYS softwares, respectively. The values of the stresses acting on the cladding tube obtained by simulation were compared to the values obtained by analytical calculation. Then, it was checked the consistency of the adopted mathematical model, in order to ensure the reliability of the computational simulation as a tool to evaluate the stresses acting on the internal and external surfaces of the fuel rod under a PWR environment.
The quest for safe and reliable fuel cladding materials
2015 - PINO, EDDY S.; ABE, ALFREDO Y.; GIOVEDI, CLAUDIA
Simulation of the effects of the extend fuel rod burn-up under loca scenario
2015 - GOMES, DANIEL de S.; TEIXEIRA e SILVA, ANTONIO; ABE, ALFREDO; GIOVEDI, CLAUDIA; MARTINS, MARCELO R.