Assessment of Radionuclides in Selected Granite Quarry Sites within Ohimini and Gwer - East Local Government Areas of Benue State in Nigeria

The assessment of radionuclides in selected granite quarry sites in Ohimini and Gwer-East Local Government Areas of Benue State was carried out using a 76 × 76 mm NaI (TI) detector crystal optically coupled to a photomultiplier tube (PMT). The detector is enclosed in a 6 cm lead shield with cadmium and copper sheet and data acquisition was done by Canberra Nuclear Products (Meastro) at Center for Energy Research Training, Ahmadu Bello University, Zaria. These sites include Anmuda, Awulema and Ikpayongo quarry sites with five samples from each site making a total of fifteen samples. From the preliminary investigation, the mean absorbed dose in Anmuda, Awulema and Ikpayongo are 12.3 nGy/h, 17.27 nGy/h and 18.87 nGy/h respectively and the corresponding Mean Annual Effective Dose equivalent are 0.15 mSv/y, 0.21 mSv/y and 0.25 mSv/y which are actually below the recommended safe values. The result of the assessment of radionuclides in granite samples includes Radium-226 (226Ra), Thorium-232 (232Th) and Potassium-40 (40K). The mean activity concentration in Anmuda for 40K is 86.717 ± 4.656 Bq/kg, that of 226Ra is 7.862 ± 3.728 Bq/kg and 232Th is 5.280 ± 1.505 Bg/kg, in Awulema, 40K is 155.656 ± 5.074 Bq/kg, 226Ra is 3.614 ± 4.220 Bq/ kg and 232Th is 8.478 ± 3.842 Bq/kg and in Ikpayongo 40K is 329.737 ± 9.405 Bq/kg, 226Ra is 5.394 ± 5.032 Bq/kg and 232Th is 7.067 ± 3.820 Bq/kg. The mean absorbed dose in Anmuda, Awulema and Ikpayongo are 10.6094 nGy/h, 13.845 nGy/h and 21.212nGy/h. The mean annual effective dose equivalent in Anmuda is 0.13 mSvy- 1, Awulema is 0.16 mSvy-1 and Ikpayongo is 0.25 mSvy-1. The average value falls within the global range of outdoor radiation exposure given by UNSCEAR-2000 publication

Author(s): Omenka S Ode1, Ige TA2 and Sombo T3

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