Environmental radiological impact of a Brazilian deactivated Uranium Mine along the period 1999-2009

This study aims to assess the environmental radiological impact (ERI) from the release of wastewaters used by the Mining Industrial Complex at Poços de Caldas (CIPC), today called Ore Treatment Unit (UTM) in Caldas, MG, Brazil, during the period 1999-2009. The effluent waters were analyzed once a week at point 014 (associated with the mine and waste pile 8). Critical radionuclides are ²³⁸U, ²²⁶Ra, ²¹⁰Pb, ²³²Th and ²²⁸Ra. The ²³⁸U and ²³²Th were analyzed by spectrophotometry. The ²²⁶Ra, ²¹⁰Pb and ²²⁸Ra, in turn, were analyzed by radiochemical separation methods and subsequent radiometry. The dose estimates were based on the model proposed by the National Nuclear Energy Commission (CNEN) for a hypothetical critical group associated with the point of effluents release into the river Ribeirao das Antas (point 014). The maximum dose rate allowed by CNEN for release is equal to 0.3 mSv·y^-1for individuals of the critical group. Our calculations were performed using the average concentration along the ten years period study. The estimated dose value for the individual of the critical group was 0.12 mSv·y^-1. It may be concluded that the reference levels established by CNEN were not reached. This indicates that the treatment of effluents generated by the CIPC/UTM was conducted efficiently, ensuring the safety of the population living in the surroundings of the Ore Processing Unit (UTM) at Caldas. (author)