Reference levels of natural radioactivity for the beach sands in a Brazilian southeastern coastal region

摘要

Gamma dose rates of ten beaches in Ilha Grande, an island of Brazilian southeastern cost, were measured in situ using an environmental radiation detector. The values ranged from 62 nGy h(-1) at Dois Rios Beach to 126 nGy h(-1) at Preta Beach. The activity concentrations of radionuclides Th-232 series, U-238 series and K-40 in three different sand profiles (0-10, 10-20 and 20-30cm) were measured using gamma ray spectrometry and the result is shown in Bqkg(-1). In most of the cases, eight out of ten beaches, K-40 was the main contributor to the calculated local gamma dose rate. The annual effective doses were 0.15 +/- 0.03 mSv yr(-1) for Preta and 0.10 +/- 0.02 mSv yr(-1) for Caxadaco beaches, while in the others beaches the mean value of annual effective doses was 0.08 mSv yr(-1). None of the beaches analysed were considered a radiological risk. (c) 2004 Elsevier Ltd. All rights reserved.