Thermoluminescent dosimetry in the evaluation of the indoor dose of residences in São José de Espinharas-PB, Brazil

Radioecological studies of environmental dosimetry have been conducted worldwide, mainly to assess the natural levels of radiation coming from the primordial radionuclides present in the earth's crust, such as ⁴⁰K and radionuclides from ²³⁸U and ²³²Th series. These radionuclides are the main contributors to external gamma exposure indoors, especially when they are located in areas with different levels of radiation. In this context, this study aimed to determine the external effective dose rates inside houses (indoor dose), located near the uranium mine in the city of São José de Espinharas in the state of Paraiba, Northeast region, Brazil, that contain high levels of terrestrial radionuclides, which are the Naturally. Occurring Radioactive Material (NORM). To characterize the radiometric study, were installed 178 sets of thermoluminescent dosimeters, with three TLDs type LiF: Mg, Ti (lithium fluoride doped with Magnesium and Titanium) each, in the rooms of the residences, these being replaced on average, every 90 days, from December 2012 to November 2014. Environmental effective doses rates calculated for São José de Espinharas varied from 0.71 to 2.07 mSv.y^-1 with an average of 0.90 mSv.y^-1. Municipalities adjacent to the study area were also monitored in the study, highlighting: São Mamede, São José do Sabugi, Patos and Santa Luzia with interval values and averages of 0.77 to 1.41 mSv.y^-1 (0, 94 mSv.y^-1); 0.90 to 1.67 mSv.y^-1 (1.13 mSv.y^-1); 0.77 to 0.93 mSv.y^-1 (0.87 mSv.y^-1) and 1.10 to 1.27 mSv.y^-1 (1.18 mSv.y^-1), respectively. The overall average of the study was around 0.99 ± 0.10 mSv.y^-1, corresponding to an average of 2.5 times higher than the estimated for indoors according to the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), which is 0.41 mSv.y^-1, giving the municipalities, exclusive influences of radioactive materials of natural occurrences, due to the geological formation of the region, when taken into consideration the levels of these radionuclides. It is observed that the results of this radioecological monitoring, does not allow to propose any ⁱndoor contamination condition without first monitor water, food, building materials, as well as the residents to predict any real risk factor for the population of these municipalities. (author)