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[en] Phosphogypsum is the by-product of producing phosphoric acid by reacting phosphate rock with sulphuric acid. In the south-west of Spain, and near the town of Huelva, there is a big industrial complex with some factories devoted to the production of phosphoric acid, which produce annually 3 x 106 metric tonnes of phosphogypsum. Of this amount 80% is stored in nearby sites named 'gyp-stacks'. The phosphate rock treated in these factories for the production of phosphoric acid has 238U activities between 1000 and 1600 Bq.kg-1, being their daughters in approximately secular equilibrium. A fraction of these radionuclides, and in different proportion, goes with the phosphogypsum. The radionuclide activity concentrations in various phosphogypsum samples collected at different places in the gyp-stacks are given, and an average dose rate in air due to gamma rays at a point 1 m above these areas is also determined. (author)
[en] 137Cs validates Th and Ra isotope ratio dating of contaminated sediments. - This paper aims to show the usefulness of 226Ra/228Ra activity ratios and confirm the possibility of using 230Th/232Th activity ratios as chronological markers in sediment cores from an estuarine system strongly contaminated by discharges from non-nuclear industries (fertiliser plants). The validation was carried out using an independent, well-established dating technique based on the analysis of the 137Cs fallout profile, which comprises the same time interval as that covered by both isotope ratios. The advantage of using the 226Ra/228Ra activity ratio profile instead of the Th-isotope profile is that determination can be accomplished with a non-destructive, simpler and less time-consuming technique, because both Ra isotopes can be determined by gamma-ray spectrometry
[en] The present study was conducted to characterize the raw materials (ilmenite and slag), waste (red gypsum) and several co-products (sulphate monohydrate and sulphate heptahydrated) form the titanium dioxide industry in relation to their elemental composition (major, minor and trace elements), granulometry, mineralogy, microscopic morphology, physical composition and radioactive content in order to apply this knowledge in the valorization of the co-products in the fields such a as construction, civil engineering, etc. In particular, the main properties of cements produced with different proportions of red gypsum were studied, and the obtained improvements, in relation to Ordinary Portland Cements (OPC) were evaluated. It was also demonstrated that the levels of pollutants and the radioactive content in the produced RG cements, remain within the regulated safety limits. (Author). 38 refs.
[en] In this work we present results of a study concerning the distribution and behaviour of several natural radionuclides (U, Th-isotopes, 210Po and gamma-emitters) in a mining river located in the southwest of Spain. Enhancements of U concentrations relative to other analysed isotopes within the U series have been observed, being due to co-precipitation of U with heavy metals in accord with increases in P H along the river. The U excess can be traced to uranium dissolution in waters that have been used as a part of a mineral treatment process within the mine, the water subsequently being released into the river.
[en] This paper aims to show a general and simple method for gamma-ray efficiency calibration in the 186-1500 keV energy range with special attention to applications on environmental studies. This method accounts for differences in densities, composition and counting geometries between real and calibration samples. Self-absorption corrections can be easily determined from a single spectral measurement knowing only the apparent densities of the samples. We have evaluated the influence of background parameters in the response of the spectrometric system and moreover, we have calculated the minimum detectable activity due to background contribution. This calibration has been validated through three different and independent tests
[en] In this paper a simple method for the direct analysis of 210Pb (T1/2=22.3 years) by gamma-ray spectrometry in sediment samples with coaxial Ge detectors is outlined. This method, developed for a cylindrical sample geometry, accounts for variable sample heights and provides a fundamental advantage: individual self-absorption corrections can easily be determined knowing the apparent densities of the samples. The results obtained with the proposed method are in good agreement with those given by other techniques
[en] The estuary formed by the Tinto and Odiel rivers is an ecosystem of great interest because it is seriously affected by the acid mine drainage (AMD) produced by the high mining activity in the watersheds of these rivers, generating in their waters an extremely low pH (2.5- 3.5), and consequently high concentrations of heavy metals and natural radionuclides in dissolution. Secondly, in their estuary there is a large chemical industrial complex, and in particular two phosphoric acid production plants, which use a sedimentary phosphate rock from Morocco as raw material containing at approximately 1.5 Bq/g of U-series radionuclides, which produce annually about 2.5-3 millions of tonnes of a byproduct, called phosphogypsum (PG). PG contains high concentrations of some U-series radionuclides as 226Ra (650 Bq/kg), 210Pb-210Po (600 Bq/kg) or 230Th (450 Bq/kg). Seventeen sampling stations along the end of these rivers and this estuary were selected to study the behaviour of U-series radionuclides in the recent surface sediments and its waters. The most relevant results show a non-conservative behaviour of Uisotopes, precipitating in the zone where large pH changes (3-5) are produced. This behaviour is different from the majority of typical estuaries where only salinity changes are produced, and therefore, a conservative behaviour of uranium is observed. (author)
[en] A simple method for the determination in sediment samples of low-energy gamma-emitters with coaxial Ge detectors and using a cylindrical sample geometry is outlined. This method allows an easy estimation of self-absorption effects by knowing the apparent densities and the composition of the investigated samples. As calibration matrixes solid samples enriched in known amounts of natural radionuclides emitting low-energy gamma rays were used. In this way, the difficult homogenisation steps needed when liquid spikes are added to a solid blank for manufacturing the calibration sample are avoided. The method has been carefully checked and validated by applying it to sediment samples with known activities of some low-energy gamma-ray emitters. Additionally, these sediment measurements have allowed to evaluate the magnitude and importance of the self-absorption corrections