Seasonal Variation of Terrestrial Gamma Radiation Dose and Evaluation of Annual Effective Dose in AECD Campus, Dhaka, Bangladesh

Background: Seasonal variations of environmental terrestrial gamma dose rates were measured at the Atomic Energy Centre Dhaka (AECD) campus in Shahbag Thana under Dhaka City from January to December 2015. Aim of the study: This kind of study is required to detect the natural and artificial radionuclides (if any) releasing from nuclear facilities in the country or from neighbouring countries. Materials and Methods: The measurement was performed using a portable High Purity Germanium (HPGe) detector (Model No. GEM25P4-83). The portable HPGe detector was placed at 1 meter above the ground facing downward and data acquisition time was 10,000 sec. Four locations were selected in the AECD campus to obtain the spectrum and those locations were marked out using global positioning system. Results: The average dose rate of the four locations from location-1 to location-4 were 0.428 ± 0.041, 0.344 ± 0.073, 0.355 ± 0.049 and 0.405 ± 0.054 µGy.h^-1 respectively. The average dose  rate of six seasons such as winter, spring, summer, rainy, autumn and late autumn were 0.377 ± 0.088, 0.421 ± 0.071, 0.385 ± 0.066, 0.358 ± 0.031, 0.281 ± 0.106 and 0.421 ± 0.023 µGy.h^-1 respectively. The annual effective dose of the population due to the terrestrial gamma radiation were also calculated and it was varied from 0.208 - 0.627 mSv. The mean annual effective dose was found to be 0.472 ± 0.081 mSv which is comparable to the worldwide average value of 0.48 mSv.y^-1. Conclusion: It was observed that winter, spring, summer and late autumn season’s dose rates are higher than those of rainy & autumn seasons.