Radiological analysis of the suitability of Erongo granite for building material

This study measured the natural radioactivity of 226 Ra, 232 Th and 40 K in 20 granite samples obtained from the Erongo Mountain Belt and Usakos Dome of the Erongo region, Namibia. All the samples were analysed using high purity germanium (HPGe) detector after 30-days to allow for secular equilibrium. The average activity concentrations of 226 Ra, 232 Th and 40 K were 39.22 ± 3.79Bqkg −1 , 35.76 ± 17.18Bqkg −1 and 1601.45 ± 212.18 Bqkg −1 respectively. The average activity concentrations of 226 Ra, 232 Th and 40 K were used to estimate the average hazard indices and the results obtained further showed that radium equivalent activity, absorbed dose rate in air, external hazard indices (in and out), internal hazard index, external radioactivity index, internal radioactivity index, activity utilization index, annual effective dose equivalent (in and out door), exposure rate, and excess lifetime cancer risk were 213.85 Bqkg −1 , 105.95 nGyh −1 , 107.11 nGyh −1 , 0.58, 0.29, 0.68, 0.82, 0.20, 1.77, 0.52 mSv.y −1 , 0.13 mSv.y −1 , 462.03 µRh −1 and 1.82 respectively. The results obtained revealed that the radiological hazard indices were lower than their respective acceptable critical values. However, the average value of effective dose equivalent (indoor) obtained was higher than the acceptable limit.