Dosimetric Model for Assessment of Radiologic Impact due to the Liquid Waste Release containing radionuclides arising from Medical Installations to the environment

The gradual growth of the use of radionuclides in nuclear medicine, since the decade of 70, and the consequent increase of liquid radioactive discharges for the urban sewer network, brought the necessity of revise the current maximum values for release of radioactive material in sewage systems, and to develop regulation to ensure the protection of man and the environment. According to the IAEAInternational Atomic Energy Agency guidelines, the definition of new limits for authorization of practices must meet the radiological protection and safety requirements established in the Basic Safety Standard (BSS), issued in 1996. This work aims to assess clearance limits for liquid waste releases arising from medical installations using radionuclides for medical diagnosis purposes in the town of Rio de Janeiro. The results will be used to verify the need to revise the current clearance values specified in Brazilian Regulation CNEN-NE-6.05 Radioactive Waste Management in Radioactive Facilities. The proposed methodology is based on the mathematical model recommended by the IAEA, adapted to the observed releases conditions in the study area. Two scenarios are simulated: (i) direct releases to surface water bodies; and, (ii) releases to the sewer system, with the exposure of workers at the sewer treatment stations. Preliminary results indicate the need of revising current Brazilian guidelines in order to consider both the properties of radionuclides and of the type of environment receiving the releases.