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Abstract  

The method described to determine the neutron fluence is based on the plot of the isotopic variation of Cd and Gd subjected to neutron irradiation in a research reactor. The isotopic ratios are measured by thermal ionization mass spectrometry. The results indicate that the fluence values obtained, using the variation in the ratios114Cd/113Cd,156Gd/155Gd and158Gd/157Gd show standard deviations varying from 0.3 to 6.6%. These values agree with the extrapolated values calculated using the short time Au activation method. The method appears to be useful for determining paleo neutron flux in natural samples and irradiated fuels.

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Abstract  

The use of environmental monitoring as a technique to identify activities related to the nuclear fuel cycle has been proposed by international organizations as an additional measure to the safeguards agreements currently in force. The specific element for each kind of nuclear activity, or nuclear signature, inserted into the ecosystem by several transfer paths, can be intercepted to a greater or lesser degree by different living organisms. This work demonstrates the technical viability of using pine needles as bioindicators for some nuclear signatures (Co, Ni, La, Ce, Sm, Th, and U) associated with uranium enrichment activities using high resolution inductively coupled plasma mass spectrometry (HR-ICP-MS). The concentrations of the elements whose signatures were sought and were determined in pine needle samples collected at five specific sampling locations inside the area investigated demonstrate the potential of the instrument and of the method used to identify and quantify the sought signatures present in low quantities (traces) in the evaluated matrix.

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Abstract  

A sector field mass spectrometer using an inductively coupled plasma as an ion source was used in order to determine the uranium isotopic ratios in reference materials supplied by the National Institute of Standards and Technology (NIST) (NBS 950, 010, 030, 200, 500, 750, and 970). The accuracy obtained for the major isotopes was better than 0.2%.

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Abstract  

The kinetics of the anodic dissolution of metallic uranium in 1, 2, 3, and 4 mol.l-1 HNO3 solutions at 30 °C were studied by potentiostatic polarization. The dissolved uranium was determined by polarography and the anodic dissolution rates by the initial rate method. It was observed that the dissolution rate increases with the applied potential, but is independent of the HNO3 concentration, because it is a zero order reaction. A mechanism for the anodic reaction was proposed based on the adsorption theory.

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Solid-state 2-methoxybenzoates of light trivalent lanthanides

Synthesis, characterization and thermal behaviour

Journal of Thermal Analysis and Calorimetry
Authors: A. Siqueira, G. Bannach, E. Rodrigues, C. Carvalho, and M. Ionashiro

Abstract  

Solid-state LnL3 compounds, where L is 2-methoxybenzoate and Ln is light trivalent lanthanides, have been synthesized. Thermogravimetry (TG), differential scanning calorimetry (DSC), X-ray powder diffractometry, infrared spectroscopy and elementary analysis were used to characterize and to study the thermal behaviour of these compounds. The results led to information on the composition, dehydration, thermal stability and thermal decomposition of the isolated compounds. On heating these complexes decompose in three (Ce, Pr) or five (La, Nd, Sm) steps with the formation of the respective oxide: CeO2, Pr6O11 and Ln2O3 (Ln=La, Nd, Sm) as final residues. The theoretical and experimental spectroscopic study suggests predominantly the ionic bond between the ligand and metallic center.

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Summary  

A simple, selective and sensitive method was developed based on electrothermal atomic absorption spectrometry using Zeeman correction for quantitation of lead, in 100 ml of whole blood sample, as biological indicator for occupational exposure. Confidence parameters and stability of samples were considered. Ashing and atomization temperatures, considered critical, were 700 °C and 1,700 °C, respectively. The levels found during the validation process showed good sensitivity linearity, recovery, precision and accuracy. The stability results presented levels remaining constant for a 15 months period. The variations were not higher than 15% when comparing concentrations in zero time to those obtained after storage period.

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Journal of Thermal Analysis and Calorimetry
Authors: E. Ionashiro, G. Bannach, A. Siqueira, C. de Carvalho, E. Rodrigues, and M. Ionashiro

Abstract  

Solid-state Ln(2-MeO-BP) compounds, where Ln stands for trivalent Eu to Lu and Y(III) and 2-MeO-BP (which is 2-methoxybenzylidenepyruvate) have been synthesized. Simultaneous thermogravimetry and differential thermal analysis (TG-DTA), differential scanning calorimetry (DSC), X-ray powder diffraction, infrared spectroscopy and other methods of analysis were used to characterize and to study these compounds. On the base of the obtained results an Ln(2MeO-BP)3·nH2O general formula can be established.

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Summary  

Within an extensive survey of lower and higher plants in the Azores' Terceira and Santa Maria islands, this study is focused on the evaluation of ectohydric bryophytes and bark from Cryptomeria japonica as an alternative to epiphytic lichens for air-monitoring purposes. Neutron activation analysis (k 0-NAA) has been applied to all field samples for elemental determinations. Judging from the present results, and since the islands embody most features of the whole archipelago, bryophytes do not appear as an option for further campaigns in the Azores, due to scanty supply and relatively poor performance as biomonitors. On the other hand, comparisons of bark with lichens collected at the same sites seem fairly good, and elements are enriched in bark to an even greater extent than in lichens. All things considered - including material availability and ecological concern - bark stands for a sensible choice for biomonitoring in the Azores.

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