Radiation Exposure Levels Associated with Tin Mining Sites around Toro Area, Bauchi State, Nigeria

Abstract

The concentrations and distribution of natural radionuclides in soils of tin mining sites around Toro and environs, Bauchi Nigeria were investigated. Previous studies revealed that the mining activitiesenhancedthe risk of radiation exposure.Twenty six soil samples were collected from eight sites (locations) to measure their natural radioactivity concentrations due to natural radionuclides (226Ra, 232Th and 40K) using gamma spectrometry techniqueconsistof Thallium activated Sodium Iodide (NaI (Tl)) detector. The mean activityconcentration valuesfor 226Ra, 232Th and 40K are38.78 ± 3.13Bq/kg, 105.77 ± 2.46Bq/kg and 491.89 ± 7.85Bq/kg respectively. The mean absorbed dose rate was found to be 102.24 ± 3.28 nGy/h,which is above the safety limit. To evaluate the radiological hazard of the natural radioactivity, the radium equivalent activity, the hazard index (external and internal hazard index), the absorbed dose rate and the effective dose rate were been calculated and compared with internationally recommended values. The radium equivalent activity values of all samples are lower than the limit of 370Bq/kg except at location DGJ which has the value 442.46 Bq/kg. Also, the values of the external and internal indices are less than unity, except at location DGJ which has value greater than unity. The mean annual effect dose ratewas 0.212mSv/y and is less than 1mSv/y upper limit recommended for the public by International Commission on Radiological Protection (ICRP).