Preliminary results of natural radioactivity in flours commercialized in the city São Paulo by high resolution gamma ray spectrometry

Abstract

In the present work, the activity concentrations of natural radionuclides 226Ra, 232Th and 40K were analyzed in 32 samples of wheat, corn, manioc and rice flours commonly used by residents of the city of São Paulo, Brazil. All samples were dried, homogenized and tightly sealed in standard 100 mL HDPE flasks with plan screw cap and bubble spigot and measured for 150 ks by gamma spectrometry with an Extended Range Coaxial germanium detector (Canberra GX4020 detector), after approximately 4 weeks storage, in order to ensure secular equilibrium. All spectra were analyzed with the InterWinner 6.0 software. The 226Ra activity concentration was determined from the weighted average concentrations of 214Pb and 214Bi. The 232Th activity concentration was determined from the weighted average concentrations of 228Ac, 212Pb and 212Bi and the 40K one from its single gamma transition. The 226Ra, 232Th and 40K activity concentrations results ranged, respectively, from 0.97 Bq/kg ± 0.42 Bq/kg to 4.75 Bq/kg ± 0.82 Bq/kg, from 8.07 Bq/kg ± 2.36 Bq/kg to 19.02 Bq/kg ± 3.56 Bq/kg and from 25.22 Bq/kg ± 4.38 Bq/kg to 153.5 Bq/kg ± 17.02 Bq/kg.