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Abstract  

Sediment cores were collected at the Cananeia-Iguape Estuary and thelevels of 210Pb, 226Ra and 137Cs were measuredby gamma-ray spectrometry. The total 210Pb levels in sedimentsvaried from 13.5 to 122.5 Bq . kg —1 , for 226Raranged from 2.4 to 28 Bq . kg —1 and for 137Csfrom 0.28 to 6.1 Bq . kg —1 . Sedimentation rates were calculatedfrom the slope of the excess 210Pb profile in the core. The valuesobtained varied from 5 to 10 mm . y—1 , depending on thesediment deposition inputs in the local of sampling.

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Abstract  

Instrumental analysis methods for 210Pb, 226Raand 137Cs by gamma-spectrometry in sediments, as well as the sedimentationrates in cores collected from Brazilian coastal region are presented. Samplinglocations have covered the Cananeia-Iguape estuary and the continental shelfof southern Sao Paulo State. Values for 210Pb ranged from 122.5to 14.3 Bq . kg —1 for estuarine sediments and from 195.5to 23.6 Bq . kg –1 at the continental shelf. For 226Ra thevalues obtained in sediments varied from 15.2 to 2.3 Bq . kg —1 in the estuary and from 30.1 to 16.1 Bq . kg —1 atthe continental shelf. Sedimentation rates are variable, ranging from 0.53to 0.98 cm . y —1 in estuary sediments and from 0.18 to 0.40cm . y —1 at the continental shelf.

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Abstract  

A radiochemical procedure for low level strontium-90 analysis in fish samples as well as the levels of this radionuclide in fish collected along the Brazilian coast are presented. The method developed was applied in reference samples from the IAEA in order to verify the precision and accuracy of the methodology established. Results obtained for strontium and yttrium yields were about 90%. Strontium-90 levels in fish bones varied from 3 to 12 mBq.g–1 Ca and these data are reference values to our country.

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Abstract  

A method for determining210Po in marine samples by wet dissolution, deposition onto silver disc and counting by -spectrometry is described. Recovery of polonium was obtained with208Po tracer.210Po levels in fish from the Brazilian coast and sediments from Antarctic region were determined. Levels in fish ranged from 0.5 to 5.3 Bq·kg–1 wet and for sediments, mean values of 10 mBq·kg–1 were obtained.

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Solvent extraction studies using tetracycline as complexing agent

XIV. Study of the behaviour of tetracycline as an extracting agent for some fission products

Journal of Radioanalytical and Nuclear Chemistry
Authors: I. Cunha and M. Nastasi

Abstract  

The behaviour of tetracycline as an extracting agent for strontium, iodine, barium, molybdenum, technetium, zirconium, niobium, cesium, ruthenium, tellurium and uranium has been studied and the influence of the acidity of the aqueous phase upon extraction of the elements mentioned has been examined. Experiments have been made to determine whether or not the species extracted into the organic phase is the complex formed between tetracycline and the elements considered as well as to determine the time of shaking necessary so that the equilibrium between the phases is attained. As a practical application, the possibility of using the tetracycline-benzyl alcohol system for separating the fission products137Cs,140Ba,140La,141Ce,103Ru,95Zr and95Nb from each other and from uranium is presented. The same study has been made for131I,99mTc,99Mo,132Te,239Np and uranium and the steps necessary for the separation of these elements are proposed.

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Abstract  

The preparation of ammonium molybdophosphate (AMP) precipitated directly into the IRA-900 resinous structure and their application to the determination of cesium-137 in waters are described. The sample of water is passed through the resin, which retains the cesium. After the removal of strontium-90 and potassium-40 with 0.1M ammonium nitrate solution, the cesium is eluted with 1M sodium hydroxide solution. The AMP dissolved in the alkaline solution is used to precipitate the cesium by acidifying the solution.

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Abstract  

The137Cs radionuclide dispersion in the marine environment through the compartmental model is reported. The model simulates the surface water contamination caused by routine or accidental radionuclide releases. For the simulation the OCEAN program was applied in the North Sea, near to Sellafield and adjacent areas, based on published transfer coefficient data. The results are in good agreement with the literature and the model developed can be applied to the brazilian coastal regions.

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Abstract  

Methodologies for simultaneous analysis of 137Cs, 90Sr, 238Pu and 239+240Pu were developed and applied to seawater samples. 137Cs levels in Brazilian coastal seawater ranged from 0.12 to 4.7 Bq·m-3, for 90Sr from 2.0 to 8.6 Bq·m-3, for 239+240Pu from 0.8 to 4.5 mBq·m-3 and for 238Pu it was of 1.9 mBq·m-3. The artificial radioactivity levels in Brazilian seawater are typical values due to fallout deposition.

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Abstract  

Laboratory experiments using radioactive tracer were performed to study the uptake and elimination of137Cs by theAbudefduf saxatilis. A compartmental model (AnaComp Program) has estimated the transfer rates of the radioactivity through the sea-water and fish compartments as well as the dose caused by the consumption of a contaminated fish.

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Abstract  

A procedure for the isolation of137Cs from acidic fission products solutions, based on the use of silica gel and zirconium phosphate ion exchangers, is presented. The137Cs recovered by the ion-exchange process is converted to powder by coprecipitation of cesium with ammonium molybdophosphate.137Cs pellets have been prepared by compression of137Cs ammonium molybdophosphate powder using a hydraulic press. An important aspect of this procedure is that it does not require neutralization of the Purex waste.

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