LUCAS STANO JUNQUEIRA

LUCAS STANO JUNQUEIRA

Página do item completo

Resultados de Busca

Agora exibindo 1 - 8 de 8

Sedimentary profiles from a water supply reservoir at São Paulo, Brazil
2019 - SILVA, S.A.; JUNQUEIRA, L.S.; FRANKLIN, R.L.; SILVA, W.L.; FAVARO, D.I.T.; MOREIRA, E.G.
A research project has been conducted by the Environmental Company of São Paulo State (CETESB) and the Nuclear and Energy Research Institute (IPEN) in important water supply reservoirs at São Paulo State in order to perform a wide evaluation on the content of rare earths and some trace elements in sediment profiles. In the present study, preliminary results for two sampling campaigns at the Graminha reservoir are presented:February/2015 (sites 1 and 3) and August / 2015 (sites 1 and 2). Sediment core samples (around 90 cm long) were collected in the dam and sliced at every 2.5 cm. Instrumental Neutron Activation Analysis (INAA) was applied to the sediment samples in order to determine some trace elements (As, Cr, Th, U and Zn) and rare earth elements (REE) (Ce, Eu, La, Lu, Nd, Sm, Tb and Yb). The analytical methodology validation was performed by means of certified reference material analyses. As, Cr and Zn concentration values were compared to the oriented values from CCME (Canada) (TEL and PEL). Sediment quality was classified as good or very good for these elements according these criteria. Enrichment factor (EF) and Geoaccumulation Index (IGeo index)1were applied to the results by using the concentration values of the last layer of the 90.0 cm profile as background values for sediment contamination index assessment. EF>1.5 was found for REE, U and Th in the middle of the sediment profiles,in all sampling points, indicative of anthropogenic contribution. IGeo values in the range of1
Trace element assessment in sediment cores from Graminha reservoir, São Paulo State, by INAA
2019 - JUNQUEIRA, LUCAS S.; SILVA, SHARLLENY A.; FRANKLIN, ROBSON L.; FAVARO, DEBORAH I.T.
In the present study, sediment cores were collected in the Graminha (Caconde) water supply reservoir in Feb/2015 (points 1 and 3) and Aug/2015 (points 1 and 4) sampling campaigns. The four sediment cores with different depths were cut every 2.5 cm, yielding 36, 21, 33 and 37 slices of sediments, respectively, that were individually analyzed by INAA (Instrumental Neutron Activation Analysis). This analytical technique was used to quantify the elements: As, Ba, Br, Co, Cr, Cs, Fe, Hf, Rb, Sb, Sc, Ta, Zn, U and Th. The validation of precision of the methodolody was made by analyzing certified reference material. The concentration values obtained for As, Cr and Zn were compared with TEL and PEL oriented values established by the CCME (Canada) and adopted by CETESB for sediment quality evaluation. None of the sediment cores analyzed surpassed the PEL value for these elements. Sediment samples from points 2 and 3 presented the worst sediment quality but were still classified as good quality for sediments. The enrichment factor (EF) and Geoacumulation Index (IGeo) tools used for contamination level assessment were used for all sediment cores and mostly presented enrichment on As and U. The results from concentrations, EF and IGeo showed a significant increase mostly below 30 cm of depth in every core. Statistical analyses were applied to the elemental concentration values for better interpretation of the results.
Determination of I-129 on radioactive waste from Angra 1 and 2 Power Plants
2019 - JUNQUEIRA, LUCAS S.; ANGELINI, MATHEUS; ZAHN, GUILHERME S.; SILVA, PAULO S.C. da
Radioactive waste must be characterized in order to be deposited in a suitable place for its confinement, avoiding any contamination of the environment. This study determined 129I, one of the difficult-to-measure nuclides that make up the radioactive waste from Angra 1 and 2 nuclear power plants. The methodology used a 129-I (1Bq/mL) liquid certified standard and consisted on guarantying that all the iodine was converted into iodide before the addition of PdCl2 for the precipitation of PdI2. After the separation procedure the 129I was quantified by gamma spectrometry by measuring its X-ray emissions with energies of 29.7 keV and 33.8 keV, as well as the gamma-ray emission of 39.6 keV. The chemical yield of the procedure was 74.4% (0,2).
Ni-59 determination by measurement of annihilation energy
2019 - JUNQUEIRA, LUCAS S.; ZAHN, GUILHERME S.; SILVA, PAULO S.C. da
Radioactive waste is subject to regulations regarding its inventory, transportation and final deposition. Such standards require the knowledge of the tailing contents in a way that is possible to accommodate them in a repository capable of containing their radiation completely. In this study a methodology was established for determining the concentration of 59Ni using the annihilation energy (0.511 MeV) between a positron from its + emission, and an electron that is widely present in matter. To ensure the reliability of the methodology, the area of the annihilation peak was compared to 59Ni Kα and Kβ x-ray peaks. To make this method viable the separations of Ni from the other components of the sample was necessary. This was done by using dimethylglyoxime (DMG) for Ni precipitation. Of all the Ni radioisotopes only 59Ni have a half-life longer than a few days, so that 59Ni can be determined without radioisotopical interferences. After precipitation with DMG, the substrate was vacuum filtered on filter paper, using an apparatus to preserve the geometry of the precipitate in different samples. The 59Ni precipitate was then counted in an extended range gamma spectrometer and the 511 keV peak compared to the Ni x-rays in order to verify the reliability of the method.
CAX and Xsel
2019 - ZAHN, GUILHERME S.; JUNQUEIRA, LUCAS S.; GENEZINI, FREDERICO A.
In this work, the scripting capabilities of Genie-2000 were used to develop a software (CAX) that automatically anal-yses all spectrum files in either ORTEC's CHN or CANBERRA's MCA or CNF formats in a folder, generating two output files: a print-ready text file (.DAT) and a Comma-Separated Values (.CSV) file which can be easily imported in any major spreadsheet software. A second tool, named Xsel, consists in an EXCEL spreadsheet which automatically identifies the spectrum lines associated with the elements of interest, generating a clean output sheet which can be easily imported in a general spreadsheet that calculates the concentrations; an important addition to this spreadsheet is the ability to automatically recalibrate each spectrum, increasing the reliability of the peak identification procedure. These software tools are already used in daily routines at IPEN's Neutron Activation Laboratory, greatly reducing the time required for sample analyses, as well as reducing the possibility of transcription errors.
Activity determination of the difficult to measure radionuclide 55Fe in operational radioative waste from the Angra Nuclear Power Plant
2019 - ANGELINI, MATHEUS; SILVA, PAULO S.C. da; JUNQUEIRA, LUCAS S.
Pressurized Water Reactors, PWR, are responsible for converting nuclear energy from the nuclear reactions, in the core, into thermal energy by heat exchange with the water in the primary system and then into mechanical energy by the pressure increase from the heat exchange and at last, electrical energy, from the turbine rotation due to the resultant pressure. In a reactor such as described, cool water must flow through the Primary System (where the nuclear core is located) in order to allow heat exchange for electrical energy generation and also to refrigerate the core, providing it will not to be melted or causing any acci dent. Materials that make up the internal part of the primary system such as the walls or core coating may suffer effects like drag force due to the high water pressure or neutron activation due to the high l evels of radiation. Therefore some of these nucl ides that compose these materials are expected to be present in the core water and so, a filtration system is required to reduce these nuclides concentrations. At Angra Nuclear Power Plant two types of filtration systems are used , ion exchange resin, respo nsible for adsorbing these nuclides and a polymer type filter responsible for withholding solid particles in suspension. After a while, these filters become saturated and must b e replaced; once replaced , the old ones become Radioactive Waste of Low or Medi um Activity. This study has evaluated the chemical yield of different procedures for 55 Fe determination by using anion exchange chromatography, to be further applied to determine the activity concentration in nuclear waste samples. The activity concentrati ons were determined by Liquid Scintillation Counting (LSC) and Gamma Spectrometry (GS). This project is part of a bigger objective that aims to fulfill several regulations from the Brazilian National Nuclear Energy Commission (CNEN) and the development of a repository for proper storage of radioactive waste materials
Avaliação das concentrações de metais, elementos terras raras e traço em perfis de sedimentos do reservatório Graminha - Estado de São Paulo pela técnica de ativação neutrônica
2018 - JUNQUEIRA, LUCAS S.; FAVARO, DEBORAH I.T.
Avaliação das concentrações de elementos terras raras, metais e traço em sedimentos do reservatório graminha, estado de São Paulo, pela técnica de ativação neutrônica
2017 - JUNQUEIRA, LUCAS S.; SILVA, SHARLLENY A.; FAVARO, DEBORAH I.T.
No presente estudo, perfis de sedimentos foram coletados no reservatório de abastecimento Graminha (Caconde), ESP, em Ago/2014 (pontos 1 e 4). Utilizou-se a técnica analítica de Análise por Ativação com Nêutrons Instrumental (INAA) e os elementos determinados foram: As, Ba, Br, Ca, Co, Cr, Cs, Fe, Hf, K, Na, Rb, Sb, Ta, Th, U e Zn e os elementos terras raras (ETRs) (Ce, Eu, La, Lu, Nd, Sm, Sc, Tb e Yb). Os valores de concentração para os elementos As, Cr e Zn foram comparados aos valores orientadores de concentração (TEL e PEL) estabelecidos pelo CCME (Canadá) e adotado pela CETESB. Os sedimentos foram classificados como de qualidade boa ou ótima, para esses 3 elementos. Os valores encontrados nas ultimas fatias do perfil 1(profundidade 90 cm) foram tomados como valores basais de referência e a partir desses valores, calcularam-se os fatores de enriquecimento (FE) e o Índice de Geoacumulação (IGeo). Valores de FE>1,5 foram encontrados, principalmente, para os ETRs, U e Th, em ambos os pontos, indicativo de presença de contribuição antrópica. Os valores de IGeo confirmaram os valores de FE, com valores de 1