Dose estimation and calculation of radiological hazard index at Doce River / Brazil due to Fundão dam rupture

Abstract

Radionuclide activity monitoring of the natural occurrence of 226 Ra, 228 Ra and 40 K is important in order to assess the radiological impact and human exposure due to natural radioactivity. Surface concentrations of these radionuclides may change due to soil use, urbanization or deforestation. In November 2015, a rupture of a tailings dam in the upper course of Doce River, in the Southeastern part of Brazil, caused a catastrophic environmental hazard-the greatest accident in a mineral area in the Southern Hemisphere. In this work, we developed a prospective evaluation of radioactivity levels in sediments of the Doce River obtained from its estuary before and after the dam rupture. Activities were analyzed by high resolution gamma spectrometry for 226 Ra, 228 Ra and 40 K. Results ranged from 15.86 ± 0.99, 19.83 ± 1.10 and 237.15 ± 8.70 Bq.kg-1 for before the rupture and 20.70 ± 0.99, 31.82 ± 1.30 and 197.50 ± 7.62 Bq.kg-1 for the period after, respectively. This study identified a significant elevation of 226 Ra, 228 Ra activities after the rupture. We also evaluated the annual effective dose equivalent to the local population and the radiological risk index, both internally and externally. The results obtained for the radiological risk to the local population were compared with worldwide values. Keywords: Doce River, dam of Fundão, radiological risk, NORM, natural radioactivity. Carmo, et. al. • Braz. J. Rad. Sci. • 2018 2