Natural radioactivity traces in South-Brazilian cereal flours by gamma-ray spectrometry

Cereal flours are the major component of the Brazilian diet and are also important exportation products. Radioactivity concentrations of Th-232, Ra-226, K-40 and Cs-137 were determined in commercial samples of South-Brazilian cereal flours (soy, wheat, corn, manioc, rye and oat flour) to verify the radiological security of these foodstuffs. The measurements were carried out by gamma-ray spectrometry using a 66% relative efficiency HPGe detector. The K-40 flour activities, at 95% of confidence level were in: soy 474 +/- 3 Bq center dot kg(-1); corn 30.0 +/- 0.3 Bq center dot kg(-1); rye 94 +/- 1 Bq center dot kg(-1); manioc 67 +/- 1 Bq center dot kg(-1); oat 76 +/- 1 Bq-kg(-1) and wheat 36.2 +/- 0.4 Bq center dot kg(-1). The lower limit of detection for K-40 ranged from 0.54 to 1.43 Bq center dot kg(-1). The Cs-137 activities in flour samples were: soy <= 0.07 Bq center dot kg(-1), corn <= 0.01 Bq center dot kg(-1), oat 0.03 Bq center dot kg(-1) and in wheat, manioc and rye <= 0.02 Bq center dot kg(-1). The highest concentrations levels of Th-232 and Ra-226 were 0.69 +/- 0.04 Bq center dot kg(-1) and 0.44 +/- 0.03 Bq center dot kg(-1), respectively, in soy flour.