Gamma Ray Activity in Raw Materials and the End Product from the West African Portland Cement PLC, Ewekoro, South Western Nigeria

Abstract

Assessment of gamma ray activity in raw materials and the end product in `Elephant cement' from the West African Portland Cement PLC is carried out. Raw materials are collected from the company and are analyzed using gamma-ray spectrometry. The concentrations of 40K, 238U, and 232Th are highest in limestone and least in red alumina. For example, limestone has a 40K concentration of 904.42 ± 39 Bq · kg-1 while red alumina has 313.84 ± 11 Bq · kg-1. The concentration of 238U in limestone is 296.86 ± 12 Bq · kg-1 as compared to 139.44 ± 6 Bq · kg-1 in red alumina. 232Th concentration in limestone is 171.14 ± 12 Bq · kg-1 while in red alumina it is 45.65 ± 2 Bq · kg-1 . The mean activities measured for 40K, 238U, and 232Th are 667.69 ± 24, 323.48 ± 10, and 95.91 ± 4, respectively, while its corresponding mean absorbed dose rate in air at 1 m above the ground was calculated to be 264.96 nGy · h-1 or 2.321 mSv · y-1. The finished product (cement) has a mean absorbed dose rate of 282 nGy · h-1 and an effective dose equivalent of 2.471mSv · y-1. The calculated absorbed doses in nGy · h-1 and mSv · y-1 show that Elephant cement has higher activities of the isotopes than the permissible level suggested by ICRP (80 nGy · h-1or 0.7 mSv · y-1).