Radiometric survey and estimation of radiation exposure from archean rocks: a case study of Migori gold belt complex, Kenya
Natural radiation is the major source of external doses in our environment. Human exposure to high dose rates poses a health risk. In this research work, radiometric survey and dose rate assessment was carried out on Archean rocks within the gold belt mining complex of Migori, Kenya. The objective was therefore to find out the contribution of different Archean rocks to the ambient gamma-ray dose in the mining complex. The high-resolution gamma-ray spectroscopy NaI (TI) provided a sensitive experimental tool in this study. The gamma –ray radiation hazards due to the specified radionuclides 226Ra, 232Th and 40K was assessed by representative radiation hazard index (Ig)and Radium equivalent activity(Raeq). Standard IAEA certified samples were used for energy calibration and efficiency calculation of the spectrum. Radiological investigations carried out revealed that there is relatively normal level of natural radiation in the area. An arithmetic mean average activity concentration for all the rock samples was found to be1012.20±22.81 Bqkg-1 for 40K; 70.57±18.77 Bqkg-1 for 232Th and 69.19±11.29 Bqkg-1 for 238U. It was evident from the result that potassium contributes most specific activityconcentration compared to thorium and uranium. All different rock types analyzed in this work produced activity concentration that exceeded the world average values. Granite rock which is an igneous rock registered high content of potassium. The 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 concentration compared with other types of rocks.The annual effective dose of between of 0.30 𝑚𝑆𝑣𝑦−1 for rocks and 0.22 𝑚𝑆𝑣𝑦−1 for soil was registered. The average value of radium equivalent was below the recommended maximum values of370 𝐵𝑞𝑘𝑔−1 .