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Description
The concentrations of naturally occurring radionuclides 238U, 232Th, and 40K in the soil samples collected from the Ohorongo Cement Plant near Otavi, Namibia have been determined and used to estimate the baseline natural radiation level in the cement plant. A total of 50 soil samples were collected from inside and outside of the plant and analyzed using an HPGe detector. The concentrations vary from 7.3 ± 1.2 to 25.6 ± 1.8 Bq/kg with an average of 15.0 ± 4.7 Bq/kg for 238U, 12.7 ± 2.0 to 43.1 ± 3.5 Bq/kg with an average of 25.1 ± 9.9 Bq/kg for 232Th, and 132.2 ± 9.7 to 507.8 ± 22.5 Bq/kg with an average of 310.7 ± 97.2 Bq/kg for 40K. These concentrations were used to calculate the mean absorbed dose rate and the mean annual effective dose for the plant. The value of 0.04 mSv obtained for the mean annual effective dose is less than the maximum permissible dose of 1 mSv a year recommended for the public by the International Commission on Radiological protection. In order to evaluate the associated health hazard, the concentrations were also used to calculate the mean Radium equivalent activity (Req) and the mean external hazard index (Hex) for the plant. The values of 74.9 Bq/kg and 0.20 obtained respectively for Req and Hex are again much below their respective permissible values. These results and the low value obtained for the mean annual effective dose indicate that radiation hazard is negligible in the plant.
