Distribution of radionuclides and radiation hazard assessment in soils of Southern Namibia, Southern Africa.

The activity concentrations of (238)U, (232)Th and (40)K in soil samples taken from four major towns across southern Namibia have been determined by gamma spectroscopy and used to calculate the mean dose rate, radium equivalent activity (Raeq) and external hazard index (Hex) for each town. The average concentrations of radionuclides in the towns vary from 10.7±3.1 to 35.6±8.4 Bq kg(-1) for (238)U, 12.3±4.9 to 77.8±20.9 Bq kg(-1) for (232)Th and 248.0±35.6 to 734.6±61.4 Bq kg(-1) for (40)K. These values are within the range of concentrations reported in some countries but most of the values for (232)Th and (40)K are above the worldwide averages. However, the mean effective dose rate of 0.08±0.03 mSv y(-1) and the mean values of Raeq and Hex for the region are below their respective permissible limits, thus indicating that radiation hazard is negligible in the region.