Browsing by Author "Oyedele, James"

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    Determination of natural radioactivity in soils of Henties Bay, Namibia
    (University of Namibia, 2015) Shimboyo, Simon A.; Oyedele, James
    The concentrations of naturally occurring radionuclides 40K, 238U and 232Th in soil samples collected across the town of Henties Bay in Western Namibia have been determined and used to estimate a baseline natural radiation level in the town. These concentrations were measured using an HPGe detector and found to vary from 790.2±31.6 Bq kg−1 to 1039.0±38.7 Bq kg−1 with a mean of 936.1±68.5 Bq kg−1 for 40K, 36.2±2.6 Bq kg−1 to 153.4±4.8 Bq kg−1 with a mean of 62.2±20.0 Bq kg−1 for 238U and 50.4±4.5 Bq kg−1 to 323.6±12.7 Bq kg−1 with a mean of 97.1±44.7 Bq kg−1 for 232Th. The corresponding effective dose rate obtained from the radionuclides is 0.16±0.04 mSv y−1. This dose rate is well below the limit of 1.0 mSv y−1 recommended for the public by the International Commission on Radiological Protection (ICRP) and indicates that the town has a normal background radiation.
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    Distribution of Gamma-Emitting Radionuclides in the Soils of the Neudamm Campus of the University of Namibia, Windhoek, Namibia
    (University of Namibia, 2013) Oyedele, James
    The concentrations of naturally occurring radionuclides 40K, 232Th and 238U in soil samples taken from the Neudamm campus of the University of Namibia, Windhoek, Namibia have been determined and used to calculate a mean annual effective dose for the campus. The concentrations were measured using a sensitive gamma-ray spectroscopic system consisting of a high purity germanium detector and associated equipment. 40K was found to have the highest specific concentration varying between 229.1 13.5 Bq kg􀀀1 and 499.0 16.5 Bq kg􀀀1 with a mean value of 364.5 79.3 Bq kg􀀀1 while the concentration of 232Th varies between 10.4 2.8 Bq kg􀀀1 and 38.5 3.8 Bq kg􀀀1 with a mean value of 28.0 9.2 Bq kg􀀀1 and the concentration of 238U varies between 11.7 1.3 Bq kg􀀀1 and 24.7 2.1 Bq kg􀀀1 with a mean value of 18.5 4.8 Bq kg􀀀1. The value of 0.05 0.01 mSv y􀀀1 obtained for the mean annual effective dose is well below the limit of 1 mSv y􀀀1 recommended for the public by the International Commission on Radiological Protection. This result indicates that radiation hazard is negligible on the campus.
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    Measurement of natural radioactivity and dose rate assessment of terrestrial gamma radiation in the soils of Karibib and Okahandja, Namibia
    (University of Namibia, 2019) Midzi, Wilfred; Oyedele, James; Shimboyo, Simon A.; Taapopi, Erastus E.
    The activity concentrations of the naturally occurring radionuclides 238U, 232Th and 40K in soil samples taken from the towns of Okahandja and Karibib in Namibia have been determined by gamma-ray spectroscopy using an HPGe detector. The average activity concentrations of 238U, 232Th and 40K in Karibib are 29.4±5.8Bq/kg, 49.0±8.6Bq/kg, and 824.3±153.5Bq/kg while they are 40.9±8.6Bq/kg, 57.9±19.4Bq/kg, and 562.4±125.4Bq/kg respectively in Okahandja. Most of these values are much higher than the corresponding worldwide average values. These activity concentrations were used to calculate different radiological parameters in order to evaluate the associated health hazard. The value of 9.5×10−2 mSv/y obtained for the mean effective dose rate in both towns is far below the permissible limit of 1.0mSv/y recommended by the ICRP and implies that there is no significant radiation hazard in the towns. Also, the values of 163.0Bq/kg and 167.1Bq/kg obtained for the average radium equivalent activity (Raeq) in the towns and the corresponding values obtained for the average external hazard index (Hex) are much below their maximum permissible limits thus confirming that radiological hazard is negligible in the towns.
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    Soil radioactivity levels and associated hazards in selected towns in uranium-rich western Namibia
    (University of Namibia, 2016) Shimboyo, Simon A.; Oyedele, James; Sitoka, S.S.
    Soil samples from three major towns and a holiday settlement in uranium-rich western Namibia have been analysed using a HPGe detector for radioactivity due to 238U, 232Th and 40K. The average activity concentrations of the radionuclides in the towns and settlement vary from a low of 18.6 ± 4.6 to a high of 69.6 ± 26.3 Bq kg−1 for 238U, 23.8 ± 8.4 to 91.1 ± 41.0 Bq kg−1 for 232Th and 460.3 ± 76.2 to 959.5 ± 194.7 Bq kg−1 for 40K. In order to evaluate the associated health hazard, the concentrations were used to calculate the mean annual effective dose, radium equivalent activity (Raeq) and external hazard index (Hex) for the towns and settlement. The values of 0.11 mSv, 195.3 Bq kg−1 and 0.53 obtained respectively for the mean annual effective dose, Raeq and Hex are, however, below their permissible limits thus implying that radiation hazard is negligible.