Natural radioactivity and their radiological effects for different types of rocks from Egypt

The present work investigated the radioactivity level of the rocks samples collected from different sites in Egypt. Twenty one rocks samples were analyzed by gamma-ray spectrometry using NaI(Tl) detector with specially designed shield. The concentration of three natural radionuclides namely 226Ra, 232Th and 40K has been determined and compared with chemical data obtained by XRF analysis. The results showed that these radionuclides were present in concentration ranges (3.4–99, 7.5–134 and 93–3382 Bq kg−1), (54.9–211.6, 20.71–170.5 and 2068–2344 Bq kg−1) and (13–106, 29.25–106.1 and 682–755 Bq kg−1) for gneiss, granite and basalt rocks, respectively, while the values were (7.5, 12.5 and 263.9 Bq kg−1) and (113, 148.5 and 1672 Bq kg−1) for 226Ra, 232Th and 40K in sandstone and siltstone rocks, respectively. Also radium equivalent activity, total dose rates and external hazard index of the rocks samples under consideration were calculated. The results showed that granite rocks contain a high proportion of natural radioactive elements, while sandstone rocks have lesser radioactivity concentration compared with other types of rocks. - Highlights: ► This work investigated the radioactivity of rocks from different sites in Egypt. ► Rocks samples were analyzed by gamma-ray spectrometry using NaI(Tl) detector. ► Concentration of three natural radionuclides namely 226Ra, 232Th and 40K has been determined. ► Results compared with chemical data obtained by XRF analysis. ► Absorbed dose rate, radium equivalent activities and external hazard index were evaluated.