Radionuclide content of concrete building blocks and radiation dose rates in some dwellings in Ibadan, Nigeria

Thirty-two samples of concrete building blocks were collected from different block making industries in Ibadan. The radioactivity concentrations of the natural radionuclides in the samples were determined by gamma-ray spectrometry with a NaI(Tl) detector. The radioactivity concentrations varied from 6.2 to 57.5 Bq kg−1, 12.4 to 64.9 Bq kg−1 and 95.3 to 766.1 Bq kg−1 for 226Ra, 232Th and 40K, respectively. The radium equivalent activities of the 32 samples varied from 51.3 to 175.7 Bq kg−1. Radiation exposure levels in 30 dwellings were determined using LiF thermoluminescent dosimeters. The annual equivalent dose rates varied from 0.318 to 0.657 mSv y−1 with a mean of 0.433 mSv y−1. The annual effective dose rate to the whole body was calculated as 0.236 mSv y−1, which is less than that (mean) estimated by UNSCEAR for normal background areas.