Assessment of population doses and radiation hazards from rock samples collected in the South West of Cameroon

The concentrations of the natural radios-nuclides: Ra-226, Th-232, K-50 have been determined in syenites which are typical rocks from Awanda, Bikouessi, and Ngombas, localities in the South West of Cameroon. A HPGe p-type detector coupled to a multichannel analyzer was used to perform measurements and data. processing. The highest average value of Ra-226 concentration (4026 +/- 270 Bq/kg) was observed at Ngombas whereas the highest average value of Th-232 concentration (1385 +/- 176 Bq/kg), were detected at Awanda. However K-40 contributes significantly to increase the radioactivity in rocks from the three locations studied in this work. The radium equivalent activity Ra-eq, the external hazard index H-ex, the outdoor absorbed dose rate D in air and the annual effective close equivalent E were evaluated to external radiation exposure for people living to studied areas. The mean absorbed dose rate in air is 1427.49 n Gy/h at 1.0 m above the soil.