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 232 Th, 226Ra, 40K and 137Cs 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 40K flour activities, at 95% of confidence level were in: soy 474±3 Bq . kg-1; corn 30.0±0.3 Bq . kg-1; rye 94±1 Bq . kg-1; manioc 67±1 Bq . kg-1; oat 76±1 Bq . kg-1 and wheat 36.2±0.4 Bq . kg-1. The lower limit of detection for 40K ranged from 0.54 to 1.43 Bq . kg-1. The 137Cs activities in flour samples were: soy £0.07 Bq . kg-1, corn £0.01 Bq . kg-1, oat £0.03 Bq . kg-1 and in wheat, manioc and rye £0.02 Bq . kg-1. The highest concentrations levels of 232 Th and 226Ra were 0.69±0.04 Bq . kg-1 and 0.44±0.03 Bq . kg-1, respectively, in soy flour.