Evaluation of radionuclide contamination of soil, coal ash and zeolitic materials from Figueira Thermoelectric Power Plant

Abstract

The feed pulverized coal used at Figueira thermoelectric power plant (FTPP) presents a significant amount of uranium concentration and the potential radiological impact pathways into the surrounding environments should be monitored frequently. Neutron activation analysis was used to determine 238U and 232Th, and gamma-ray spectrometry was used to determine 226Ra, 228Ra, 210Pb and 40K contents present in coal, different types of coal ashes, their synthesized zeolites and two different soil samples collected in the vicinity of FTPP as well as, radiological indices to determine possible health effects due to radiation exposition. The natural radionuclide concentrations in pulverized coal were 216 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 the different zeolitic products. The activity concentration of 238U was higher than worldwide average concentration for all samples. The concentration of the uranium series found in the ashes was 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). The radiological indices indicated that the environmental disposal of fly ashes may represent a risk for public health, therefore, the resulting data can be used for systematic studies on radiological implication due to the release of TENORM caused by coal-fired power plant.