Radionuclides Activity and Associated Radiological Indices of Two Commonly Used Brands of Nigerian Cements
Keywords:
NORMs, Cement, Gamma Spectrometry, Exposure, Radiological risksAbstract
Cement is a composite natural product that is widely used in building construction and it is reported to contain varying levels of naturally occurring radioactive materials (NORMs) that might be a source of gamma radiation exposure to human. The radioactivity concentrations of 226Ra, 232Th and 40K in two commonly used brands of cement (CA and CB) for building purposes were determined using gamma-ray spectrometry and the radiological indices [Radium Equivalent activity (Raeq), Absorbed Dose rate (DR), Annual Effective Dose rate (AED), Criteria formula (CF), Representative level index (RLI), Activity utilization index (AUI), Gamma index (Iᵧ), Alpha index (Iα), External hazard (Hex), and Internal hazard (Hin)] were estimated. The average values of activity concentrations of 226Ra, 232Th, 40K are 82.72 ± 5.73, 3.71 ± 0.18, 189.83 ± 9.75 Bqkg-1 and 84.04 ± 7.30, 3.82 ± 0.35, 183.50 ± 8.86 Bqkg-1 for CA and CB brand, respectively. The ranges of estimated values of Raeq were 93.72 - 113.00 Bqkg-1, and 87 – 114.99 Bqkg-1 for CA and CB brand. The mean values of Hin were 0.50 and 0.51 for CA and CB brand. The Hin, Hex and RLI values were less than unity. None of the average values of the Iᵧ nor the values obtained for each samples exceeded the exemptions limit Iᵧ. The average absorbed dose rate in CA and CB brands were 48.44 and 48.85 nGyh-1, respectively. The excess life cancer risk (ELCR) obtained for CA and CB cement brands ranged from 7.80 ×10-6 - 9.55 × 10-6 and 7.24 × 10-5 – 9.79 × 10-6. The values of radiological indices were lower than the permissible limits stipulated by International Commission on Radiological Protection (ICRP) and United National Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) indicating the safe use of such cement brands as materials for building constructions. Therefore, it can be concluded that no significant radiological health risk is envisaged by using the brands of cements under consideration for the construction building for human dwelling.
