RADIOECOLOGIA DE RESERVATÓRIOS APLICADA À RADIOPROTEÇÃO AMBIENTAL: ESTUDO DE CASO NO BRASIL

Abstract

RESERVOIRS  RADIOECOLOGY APPLIED TO ENVIRONMENTAL  RADIOPROTECTION: CASE STUDY IN BRASIL. Radioecology is concerned with the study of the behaviour of radionuclides in the environment whilst the concern of environmental radioprotection is to avoid the deleterious biological effects of exposure to radiation. To achieve these goals, both sciences use environmental dispersion models and dosimetry, which are dependent on environmental transfer factors (ETF). To assess the radiological environment impact (REI) in reservoirs, a model of radionuclides dispersion in the environment was proposed based on the division of the reservoir into compartments interrelated through ETF. The International Atomic Energy Agency (IAEA) proposed ETF's based on world averages for various radionuclides that are widely used for impact assessments of facilities handling radionuclides. This study aims to estimate local values of ETF's, bioaccumulation factors and partition coefficient for the radionuclides ²³⁸U, ²³²Th, ²²⁶Ra, ²²⁸Ra and 210Pb in two reservoirs. One reservoir is located in the caatinga-cerrado transition zone (southwest of Bahia state) and the other one in the tropical forest-savanna transition area (south of Minas Gerais state) and compare them with the values recommended by IAEA. Finally, the result of the dispersion model was used in dosimetric models in order to generate a REI based on dose calculation in the biota. The use of ETF's values locally estimated and values recommended by IAEA resulted in assessments different by orders of magnitude, and the values recommended by IAEA resulted in REI an order of magnitude higher than the one obtained from locally estimated EFT's. This fact points to the need to establish local EFT's. The values recommended by IAEA proved to be conservative and may be used for preliminary assessments.

Keywords: Radioecology; environmental radioprotection; natural radionuclides; uranium mining.