Radiation safety and environmental protection issues of uranium mines and mills in Brazil

Full text: In 1971 an immense uranium ore deposit was discovered in Caetite, Bahia, at the Northeast region of Brazil, estimated to have about 100 thousands tonnes of uranium concentrate (U3O8). Up to 1995, Brazilian needs were restricted to feed the nuclear reactor Angra 1, then supplied by the first Brazilian mine located in Caldas, Minas Gerais. When the Government decided to finish the next reactor, Angra 2, it became necessary to have larger supplies of uranium concentrate. Therefore, the project of producing uranium in Bahia was elaborated by the Industrias Nucleares do Brasil - INB, complying with all the strict national and international safety and environmental protection regulations. Considering the mineral characteristics and the very dry weather conditions of the region, it was decided to use the heap leaching process to extract the uranium ore. After been crushed, the ore is piled and irrigated with a sulphuric acid solution. This technique spares the milling, mechanic agitation and filtration phases, allowing, besides a substantial investment reduction and operation at smaller costs. The extraction process accomplishes the uranium concentration by organic solvents, followed by separation by precipitation, and drying. One of the characteristics of the process is that it can be carried out without the need for liberation of effluents to the environment. Recently, the Brazilian Government announced the decision to resume the construction of Angra 3, and there are plans for the construction of four other new nuclear plants. Accordingly, projects for the expansion of the current uranium production capacity in Caetite were developed, and comprise going for underground mining and shifting to conventional leaching. This paper summarizes the present status of radiation safety and environmental protection activities that are in place in and around the uranium mine and milling facilities of Caetite. It describes the workforce radiation protection measures, including dose assessment for direct exposition and incorporation, over the years of operation, and measures envisaged to comply with the future expansion of the enterprise. The environmental protection programme is presented, detailing the continuous monitoring of up to 30-kilometer area around the unit, including the control of: underground and rain water, air, soil, grass, agricultural products and milk. Reference is made to the request made by INB for hosting the IAEA Uranium Production Site Appraisal Team (UPSAT) programme mission, in order to provide assessment of the status of present operational safety and operational practices for both mining and milling at Caetite. (author)