Determination of the natural radionuclide content and associated radiation hazard in soil samples collected from the Ohorongo cement plant and the town of Otavi, Namibia

Abstract

The activity concentrations and associated radiation hazard of the primordial radionuclides ²³⁸U, ²³²Th, and ⁴⁰K in soil samples collected from the Ohorongo cement plant and the town of Otavi, Namibia, have been studied by gamma-ray spectrometry. The average activity concen[1]trations of ²³⁸U, ²³²Th, and ⁴⁰K in the plant are respectively 15.0 ± 4.7Bq/kg, 25.1 ± 9.9 Bq/kg, and 310.7±97.2 Bq/kg while they are 21.6±7.2 Bq/kg, 20.3±8.5 Bq/kg and 256.4±113.7 Bq/kg in Otavi. All these values are lower than the worldwide average values. In order to determine the associated health hazard, the activity concentrations were used to calculate different radiological parameters. The values of 43 ± 15 µSv/y and 40 ± 15 µSv/y obtained for the mean effective dose rate at the cement plant and town, respectively, are less than the maximum permissible value of 1.0 mSv/y recommended by the International Commission on Radiation Protection (ICRP). Sim-ilarly, the values of 74.9 ± 25.6 Bq/kg and 70.4 ± 26.7 Bq/kg obtained respectively for the mean radium equivalent activity (Ra_eq) in the cement plant and town as well as the corresponding values obtained for the mean external hazard index are far below the maximum permissible limit. These results imply that radiation hazard is negligible at the Ohorongo Cement plant and town of Otavi.