[en] This work was aimed at studying the behaviour of ²²²Rn in an experimental underground copper mine in Brazil with a single entrance. The ²²²Rn concentrations, measured by using a dynamic radon measuring technique, varied between 30.5 Bq.m^-3, during ventilated conditions applied to the mine galleries, and 19.4x10³ Bq.m^-3 for non-ventilated conditions and when operational mining activities were conducted inside. High radon concentration surges were observed after blasting and drilling activities, in the cases of inadequate ventilation, it was estimated that workers could be subjected to exposures as high as 10 μSv.h^-1, only due to ²²²Rn and its short-lived progeny. The results show the importance of real-time measurements to evaluate radon dynamics during mining operations. (author)

No abstract available

No abstract available

[en] Acid Rock Drainage is of great concern to environmental regulators and mine operators in many countries around the world. During the operational life of an installation, the collect and treat strategy is a commonly employed strategy to reduce pollutant emissions to the environment. Regarding the post-operational scenarios a suite of different strategies is available in the literature. Acid drainage is a crucial problem at the uranium mining and milling site of Pocos de Caldas. Two waste-rock piles (of about 60 ha each) resulted from mining activities. Presently acid waters are being collected and neutralized, the solid material being disposed in the tailings dam. The Institute of Radiation Protection Dosimetry, has developed studies that concluded that a permanent solution to the problem should favor covering the dumps with a three layered cover system. However if the uranium average concentration in the drainage (about 10 mg/L) is taken into consideration, its economical recovery may be thought about. This strategy will imply in the recovery of 30 tons U₃O₈ per year - representing c.a. 30% of the mean annual production of the installation. The recovery would include the use of ion-exchange resins. The technical and economical viability of the strategy as well as technical and economical issues concerning the application of a dry cover to the waste rock piles will be presented and discussed in detail. (author)

[en] Acid mine drainage (AMD) is a world wide problem that occurs whenever sulfidic material is present in association to the mined ore. The acidic waters generated by the process of sulfide minerals oxidation can mobilize important amounts of pollutants and cause significant environmental impacts. The composition of the drainage will depend, on a very large extent, on the mineralogy of the rocks. The purpose of this paper is to demonstrate that acid mine drainage has the potential to enhance the natural levels of environmental radioactivity. The paper revises some strategies to be used in the diagnostic of the problem. General mathematical formulations that can assist on the prediction of the duration of the problem, and the definition of the size of the oxidizing zones in a waste dump are given. A study case on a waste dump of the Pocos de Caldas Uranium Mining Site, Brazil is also presented. (author)

[en] Niobium, phosphate, coal and gold mining facilities have been selected as case studies with the aim of identifying possible sources of radiological impact during and after cessation of industrial operations. The results have shown that acid drainage, as well as chemical processing of mineral ores, constitute relevant impact indicators for present-day and future scenarios. The possible use of solid wastes abandoned at the end of the operations represents a long-term radiological concern. Therefore, it is necessary that Brazilian legislation for environmental licensing be revised taking into account the potential environmental and radiological impacts caused by these industries and establishing remedial procedures for waste storage areas in the existing sites. The indicators developed and procedures carried out can be used in screening for decisions on the adoption of regulatory requirements for practices at such types of installations

[en] Presently, the known uranium resources of Brazil amount to 262,200 tU as recoverable conventional sources producible below US$ 80/kgU. The Pocos de Caldas production centre ceased its operation in 1997 and a production facility with a capacity of 300 t U₃O₈/year is planned to start operation in 1999. It will be sustained by known resources recoverable at costs of up to US$ 80/kgU. Brazil's present uranium requirement is about 120 tU/year. With the completion of the second nuclear power plant the requirement will increase by 250 tU per year, beyond the first core which would demand 560 tU. Different non-uranium mining activities present high concentrations of uranium associated to the main ore. These include three major sources: one, where uranium occurs associated to phosphate and plants where uranium occurs associated to pyrochlore (Nb ore). Recovery of uranium from these installations has the potential to increase the Brazilian production significantly and will play a key role in the case of the construction of the third nuclear power plant. (author)

No abstract available

[en] Acid rock drainage generated as a result of sulfitic minerals oxidation is a source of pollution in many mining sites all around the world. This is the case at the uranium mining site of Pocos de Caldas, Brazil. The present study was aimed at studying the geochemical mechanisms involved on the mobilization of radionuclides from the waste rocks that occurs along with the acid drainage. The environmental radiological impacts caused by these pollutants were also assessed. It has been shown that precipitation of Ra and Pb as sulfates was the most important mechanism in the reduction of both radionuclides activity concentration in the acid drainage. A result of this study was that uranium isotopes were the most important radionuclides in terms of the exposure of the critical group. It has been suggested that the recovery of uranium from the acid drainage would be a feasible practice, economical aspects taken into account. It has also been estimated that pyrite oxidation will occur for more than a thousand years. The long time scale involved on the oxidation of the pyritic material implies the need for the adoption of permanent remedial actions. To assess applicable remediation strategies it has been suggested that oxygen and temperature profile determinations should be carried out in the dump

No abstract available