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High levels of environmental radioactivity are caused by the composition of minerals in the earth's crust and the impact of prospection and utilization of natural sources, mainly due to the presence of 40K and radionuclides of 238U and 232Th series. Radium equivalent activity (RaEq) was calculated to assess the risk associated with primordial radionuclides in areas with clay extraction and production of bricks and tiles for civil construction. Twenty-eight clay samples, collected from potteries in Paraíba and Rio Grande do Norte states, Brazil, were analyzed using a non-destructive gamma-spectrometry method. Results showed radium equivalent activity in the range of 85 to 748 (mean value of 334) Bq kg−1. Around 29% of the samples presented RaEq higher than the limit of 370 Bq kg−1, a value established for specific applications of the products, whose raw material must be assessed in the source of extraction to comply with the radioecological protection principles. The qualitative characterization confirmed that all the radionuclides found in samples are of natural origin, with elevated values for some clay deposits, leading to suggestions to guarantee the safety of using the raw material in civil construction.
Júnior et al. (2021) studied this question.