[en] The Brazilian uranium mining company (INB) processed 2.32 10⁶ tons of uranium ore in its ore treatment unit (UTM - Caldas), located in the Pocos de Caldas plateau. During 16 years of operation, this unit discarded 2.39 10⁶ tons of solid waste in a tailing dam, with an average activity concentration of ²²⁶Ra of 7311 ± 184 Bq kg^-1. Most of the atoms of ²²²Rn generated from the radioactive waste of the tailing dam remain bounded to the mineral structure. However, a fraction of these atoms can be released from the mineral structure and then emanate. Reaching the porous space of the waste piles, the ²²²Rn moves towards the interface waste-atmosphere, exhaling into the atmosphere. The featuring properties of the ²²²Rn transport and the biological damage caused by its progeny transform this small chain of radionuclides into a scourge of nature. Because of that, the dry area of the tailing dam was the scope of this work. A methodology was developed for quantifying the exhalation rate of ²²²Rn. Moreover, the soil from its surroundings was experimentally evaluated as a cover material to reduce the exhalation of ²²²Rn. A collector of ²²²Rn was developed, being denominated 607. This collector was proved to be exact and precise after laboratory tests, when a standard for ²²²Rn exhalation was prepared with caldasite, an uranium ore with high concentration of ²²⁶Ra (26611 ± 581 Bq kg^-1), crushed to the granulometric interval from 1.168 mm to 0.589 mm. The results of ²²²Rn exhalation rate using the collector 607 were not influenced by the adsorption of water steam, considering sampling periods lower than 5 days and mass of water steam lower than 7 g. Sampling for measuring ²²²Rn exhalation rates in the dry area of the tailing dam was carried out using the collector 607, following the experimental design established by the United States Environmental Protection Agency (US EPA). The average exhalation rate in the west part of the tailing dam was 1.30 ± 1.24 Bq m^-2 s^-1 in the winter of 2006 and 2.11 ± 2.12 Bq m^-2 s^-1 in the summer of 2007; while in the north part, the exhalation rate was 1.15 ± 1.67 Bq m^-2 s^-1 in the winter and 1.03 ± 1.26 Bq m^-2 s^-1 in the summer, both results determined in 2007. An experiment was set to estimate the depth of the soil layer necessary to reduce ²²²Rn exhalation rate to values below the reference limit of 0.74 Bq m^-2 s^-1 (US EPA). This study was performed in piles of solid waste covered with soil taken from the area surrounding the tailing dam. The soil was compacted following the United States Nuclear Regulatory Commission (US NRC) procedures. The results indicated layers of 0.14 m and 0.20 m respectively for the north and west part of the tailing dam. (author)