Abstract
Neutron activation analysis and gamma-ray spectrometry was used to determine 238U, 226Ra, 228Ra, 210Pb, 232Th and 40K contents in feed pulverized coal, bottom ash, fly ash from cyclone and baghouse filters, zeolites synthesized from the ashes and two different soil samples. All the samples used in the study was collected at Figueira thermoelectric power plant, located in the city of Figueira, Paraná State, which coal presents a significant amount of uranium concentration. The natural radionuclide concentrations in pulverized coal were 4216 Bq kg–1 for 238U, 180 Bq kg–1 for 226Ra, 27 Bq kg–1 for 228Ra, 28 Bq kg–1 for 232Th and 192 Bq kg–1 for 40K.The ashes fraction presented concentrations ranging from 683.5 to 1479 Bq kg–1 for 238U, from 484 to 1086 Bq kg–1 for 226Ra, from 291 to 1891 Bq kg–1 for 210Pb, from 67 to 111 Bq kg–1for 228Ra, from 80 to 87 Bq kg–1 for 232Th and from 489 to 718 Bq kg–1 for 40K. Similar ranges were observed for zeolites. The activity concentration of 238U was higher than worldwide average concentration for all samples. The concentration of the uranium series found in the ashes were lower than the values observed in similar studies carried out 10 years ago and under the limit adopted by the Brazilian guideline (CNEN-NN-4.01). Nevertheless, the concentrations of this specific area are higher than others coal mines and thermoelectric power plants in and out of Brazil, so it is advisable to evaluate the environmental impact of the installation.
Highlights
Coal, like most materials found in nature, contains trace quantities of the naturally occurring primordial radionuclides arising from the U and Th series and 40K
It can be seen that all radionuclide concentrations increase from the coal to ash and the highest concentrations were observed in the fly ash from baghouse filter, which has the finest particles [3]
The activity concentrations for the uranium series in coal, coal combustion residuals and soil samples, collected in the vicinity of the Figueira power plant were determined and the results were compared with previous studies
Summary
Like most materials found in nature, contains trace quantities of the naturally occurring primordial radionuclides arising from the U and Th series and 40K. The combustion of coal leads to an increase of the natural radionuclides and non-combustible elements with enrichments factor in the ashes of 5–10 times [2]. The increase in specific activities of naturally occurring radionuclides in coal combustion residuals (CCRs) compared to the one of the original coals depends primarily on its inorganic fraction, i.e., the ash content. This release of natural radioactive elements into the environment can cause its redistribution into surface soil, in the vicinity of TENORM (Technologically Enhanced Naturally Occurring Radioactive Materials) industries, such as coal-fired power plants, modifying ambient radiation fields and population exposures. The ash piles increase continuously, and this uncontrolled waste disposal site may lead to radiological environmental contamination [3]
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