Browsing by Author "Olubi, O. E."

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    Estimation of Effective Dose and Excess Lifetime Cancer Risks due to Ingestion of Natural Radionuclides in Rice Samples from Selected Farms in Southwestern Nigeria
    (Ankara Üniversitesi Nükleer Bilimler Enstitüsü, 2022-11-22) Arije, O. T.; Ayodele, A. E.; Olubi, O. E.; Fizik; Other
    This study was carried out to evaluate the radioactivity concentrations of 40K, 232Th and 238U in ten rice samples of the same species collected from different rice farms across Ondo and Ekiti States, southwestern Nigeria. The activity concentration measurements were determined using n–type co-axial HPGe detectors. In samples from one of the states (Ondo), the activity concentration was found to vary from 36.04 - 2139.35 Bq∙kg-1 for 40K, 0.12 - 79.23 Bq∙kg-1 for 232Th and 0.22 - 83.36 Bq∙kg-1 for 238U. In the other state (Ekiti), the value was found to vary from 3.99 - 2078.91 Bq∙kg-1 for 40K, 5.18 - 73.82 Bq∙kg-1 for 232Th and 14.50 - 83.21 Bq∙kg-1 for 238U. The mean annual effective dose to adults from the consumption of the rice were obtained as 0.93 and 0.84 mSv∙y -1 with excess lifetime cancer risk (ELCR) calculated to be 2.98 x 10-10 and 2.56 x 10-10 for Ondo and Ekiti, respectively. The values were compared with the internationally acceptable limits and were found to be lower compared to the acceptable world average ELCR value of 0.29 x 10–3 for radiological risk to the public by UNSCEAR. The rice samples from the locations are safe for human consumption.
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    Simulation of an anomalous behavior of thermoluminescence glow peak of quartz from Nigeria
    (Ankara : Ankara Üniversitesi, 2017) Oniya, E. O.; Olubi, O. E.; Fen Fakültesi
    Mechanism of the experimentally observed anomalous shift of a thermoluminescence (TL) glow peak that varied with irradiation dose is yet to be fully established. A theory that the anomalous peak must have contained more than one first order composite peaks each with different TL dose characteristics has been one major explanation proposed to explain this observation. This work was undertaken to simulate the anomalous glow peak by using a modified version of a previously proposed model and numerically solving sets of simultaneous differential equations governing the stages of TL phenomena (excitation, relaxation and heating). In the modified model, two additional electron trapping centers were incorporated in order to simulate accurately this glow curve. Computerized glow curve deconvolution (CGCD) analyses was carried out on the simulated glow peak in attempt to retrieve back the electron trapping center energies and to identify their respective peak positions. The outcome of this confirmed the peak to be possibly composite in nature comprising of three overlapping glow peaks at 288, 300 and 317oC with respective energy gaps of 1.70, 1.73 and 1.75eV. It is therefore further substantiated that this kind of temperature shift of peak with dose resulting from composite glow peaks is possible.