keywords: Natural gamma radiation, dose rate, mean dose rate, isodose map
An in-situ measurement of the background radiation level was carried out in Gidan-Kwano, Minna, Niger state with an objective to establish a reference data record on the levels and distribution of natural background gamma radiation (NGR). The measurement was carried out using a portable calibrated NaI(Tl) scintillation survey meter. A total of 153 points were surveyed across the study area for background environmental radiation. The results obtained, varied significantly due to geological features of the study area. NGR dose rates values ranged between 87 – 252.3 nGyh–1 with overall mean value of 136.75 nGyh–1. This is more than twice higher than the reported world average value of 59 nGyh–1. However, the average annual effective dose obtained from this study is 0.17 mSv/annum, which is less than the recommended limit of 1 mSv/annum by International Commission on Radiation Protection [ICRP] for non-occupational population exposure. An isodose map for the distribution and exposure rate due to natural sources radiation for the study area was also plotted using ArcGIS software.