1. Applied Nuclear & Radiation Physics Group, Department of Physics; University of Nairobi; P.O. Box; 30197-00100; Nairobi; Kenya
2. Institute of Nuclear Science & Technology; University of Nairobi; P.O. Box; 30197-00100; Nairobi; Kenya
3. Department of Physics; University of Agriculture; P.M.B. 2240; Abeokuta; Nigeria