131 I and 99m Tc in Effluents from a Nuclear Medicine Facility and Associated Sewage Treatment Unit

The release of liquid effluents containing radionuclides from radioactive plants in urban areas has been the subject of discussions related to the environmental issue. This study presents the analysis of the activity concentrations (AC) of 131 I and 99m Tc in sewage samples collected in a nuclear medicine facility (NMF), associated with an university hospital situated in Rio de Janeiro, Brazil. The analyzes and measurements by gamma spectrometry of the collected sewage samples were performed, whose the estimated values (EV) for AC obtained for 131 I in July (8.78 × 10 3 Bq m -3 ) and September 2016 (9.80 × 10 3 Bq m -3 ) and in February 2017 (1.14 × 10 4 Bq m -3 ) were lower than the exemption level (EL = 1.90 × 10 4 Bq m -3 ). For 99m Tc, the EV for AC obtained from August (4.77 × 10 2 Bq m -3 and 2.96 × 10 4 Bq m -3 ) to September 2017 (2.18 × 10 3 Bq m -3 ) were lower than the EL (1.90 × 10 9 Bq m -3 ). From an environmental point of view, the presence of 131 I in the sewage treatment unit (STU), even if below the legal release limit, points out the greater importance of this radionuclide, as it requires special precautions in its adequate storage for the radioactive decay in the NMF and the dilution effect to reduce its AC minimizing the environmental impact after the effluent release to the environment. The presence of 131 I in the STU was not expected pointing to the need and evaluation of the waste management system (WMS) of the NMF.