Gamma-ray measurements of naturally occurring radioactive samples from Cyprus characteristic geological rocks

Abstract

Using high-resolution gamma-ray spectroscopy, the terrestrial gamma radiation in all the predominant types of geological rock formations appearing in Cyprus was measured. Soil samples were collected from each rock type, sealed in 1 l plastic Marinelli beakers, and measured in the laboratory for 24 h each. From the measured gamma-ray spectra, activity concentrations were determined for 232Th (range from 1.3 to 52.8 Bq kg-1), 238U (from 0.9 to 90.3 Bq kg-1) and 40K (from 13 to 894 Bq kg-1). Elemental concentrations mean values of (2.8±0.7) ppm, (1.3 ± 0.3) ppm and (0.6 ± 0.1)% were extracted, for thorium, uranium and potassium, respectively. Absorbed dose rates in air outdoors were calculated to be in the range of 0.1-50 nGy h-1, depending on the geological features, with an overall mean value of (14.7 ± 7.3) nGy h-1. The corresponding effective dose rates per person outdoors were estimated to be between 0.1 and 61.4 μSv yr-1, assuming a 20% occupancy factor. © 2003 Elsevier Science Ltd. All rights reserved.