131I and 99mTc in effluents from a nuclear medicine facility and associated sewage treatment unit

Abstract

The release of liquid effluents containing ra dionuclides from radioactive plants in urban areas has been the subject of discussions related to the environ mental issue. This study presents the analysis of the activity concentrations (AC) of 131I and 99mTc 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 131I in July (8.78 × 103 Bq m-3) and September 2016 (9.80 × 103 Bq m-3) and in February 2017 (1.14 × 104 Bq m-3) were lower than the exemp tion level (EL = 1.90 × 104 Bq m-3). For 99mTc, the EV for AC obtained from August (4.77 × 102 Bq m-3 and 2.96 × 104 Bq m-3) to September 2017 (2.18 × 103 Bq m-3) were lower than the EL (1.90 × 109 Bq m-3). From an environmental point of view, the presence of 131I 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 131I in the STU was not expected pointing to the need and evaluation of the waste management system (WMS) of the NMF.