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ABSTRACT: The production of electricity in coal-fired power plants (CFPP) is considered a NORM (Naturally Occurring Radioactive Materials) activity because the coals they burn can present relatively high contents of the naturally occurring radionuclides. In this study, the main radiological impact pathways into the surrounding environments of the four largest coal-fired power plants in Spain were analyzed. These pathways are, first, atmospheric evacuations and wind resuspension and, second, effluent evacuations to nearby rivers or directly to the sea. The atmospheric releases of radionuclides were evaluated by the analyses of soil profiles in the vicinities of the CFPPs. No significant enhancement of radionuclides in the surface soil was observed at the points of maximum deposition of combustion gases, located from 4.3 to 13 km away depending on the considered CFPP. However, an increase of (40)K, (226)Ra, and (232)Th in the surface soils was observed in the first kilometre from the chimney for two CFPPs. This suggested that these radionuclides were released in particulate form. There was also a net influence of the climate in which the CFPPs were located. This was observed in the two CFPPs that were in dry environments, while no increase was observed in the other two, located in more humid environments. The liquid effluents released usually presented an enhancement of dissolved chemical species regarding the initial intake water. Enrichments of the (234,238)U and (226)Ra contents in the water used in the plants' routine procedures were observed, and of (210)Po in the wastewater of just one of the plants. In any case, this enhancement was below the parametric value for the Total Indicative Dose for the hypothetical human consumption of the released waters. As a consequence of these releases of radionuclides, local products destined for human consumption produced in the vicinity of the facilities might incorporate natural radionuclides by these pathways, finding no significant enhancement of the natural radionuclide contents due to the CFPPs.
Journal of Environmental Monitoring 03/2012; 14(3):1064-72. · 1.99 Impact Factor
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ABSTRACT: In several Naturally Occurring Radioactive Material (NORM) industries, relatively high temperatures are used as part of their industrial processes. In coal combustion, as occur in other high temperature processes, an increase of the activity concentration of every natural radioisotope is produced both, in residues and by-products. An additional increase can be observed in the activity concentration of radionuclides of elements with low boiling point. This work is centred in the increase of polonium, more precisely in its radioisotope Po-210, present in the natural chains, and with a half-life long enough to be considered for radiation protection purposes. This additional increase appears mainly in the residual particles that are suspended in the flue gases: the fly-ashes. Besides, scales, with a high concentration of this radioisotope, were observed. These scales are produced on surfaces with a temperature lower than the boiling point of the chemical element. Both, the accumulation in particles and the production of scales are attributed to condensation effects. When effective doses for the public and the workers are evaluated, taking into account these increases in activity concentrations, the use of theoretical models is necessary. In this work a theoretical description of those effects is presented. Moreover, a verification of the predictions of the model was performed by comparing them with measurements carried on in coal-fired power plants. The same description here presented is applicable in general to the behaviour of Po-210 in other NORM industries where high temperature processes involving raw materials are used, as can be ceramic, cement production, tiles production or steel processing.
Journal of environmental radioactivity 11/2010; 102(5):520-6. · 1.47 Impact Factor
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ABSTRACT: The Spanish law that transposes the European Directive 29/96 is based on the recommendations established by ICRP in 1991. This law requires that estimations of the doses due to radioactive emissions, from practices or installations in which ionising radiation sources are used, must be performed in a regular base and in the more realistic possible way. More recently, the ICRP, as well as the European Union, recommended that, in order to reach a realistic estimation, a gradual approach made by consecutive iterations should be made. However, in spite of the huge amount of documentation, realistic dose assessments are usually treated just for artificial radionuclides, being Naturally Occurring Radioactive Materials (NORM) industries only considered by regulation, regarding to the necessity of performing studies to determine if there is or is not a significant increase in the exposition to the workers or to the public. In this paper an adaptation of the general criteria used to carry on realistic dose assessments for the particular case of NORM is presented. Also the difficulties and implications, that applying such criteria involve, are analysed. In addition the main parameters, which could influence the uncertainty of the assessment, are discussed.
http://dx.doi.org/10.1051/radiopro/20095107.
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ABSTRACT: The study presented here, being its main goal to evaluate the behaviour of natural radionuclides in coal combustion, is part of a wider study carried out by CIEMAT and the University of Extremadura (UEX). The research is addressed to the radiological evaluation of the workers and the public as a result of the operation of the four biggest Spanish Coal-Fired Power Plants (CFPPs). Some generally used effects were confirmed in this study, as the difference in concentration of 210Po in fly and bottom-ashes. Enrichment factors relative to 40K as defined by UNSCEAR were found to be a little different than expected. 210Po enrichment was found in gypsum (material obtained as a by-product in the desulphuration process). In order to confirm the assumption considered to explain difference in 232Th activity concentration between bottom and fly ashes, carbon content was measured, obtaining that it should be reviewed.
http://dx.doi.org/10.1051/radiopro/20095106.
