抄録
The radioactivity concentrations in soil and water samples collected from 25 locations have been determined by using a gamma-ray spectrometry. Gamma-spectrometry measurements were made using a hyperpure germanium detector surrounded with shielding material to reduce the background counting rate. The EmcaPlus MCA emulation software was used for gamma-ray spectrum analysis. Results show that the concentrations of 238U, 232Th and 40K in the soil samples varied from 11.1 to 34.5 Bq.kg-1 with a mean of 17.9±4.9 Bq.kg-1, from 19.5 to 42.6 Bq.kg-1 with a mean of 26.6±5.6 Bq.kg-1 and from 289.1 to 511.1 Bq.kg-1 with a mean of 379.6±49.9 Bq.kg-1, respectively. The concentrations of 238U, 232Th and 40K in the water samples varied from 110.7 to 214.3 mBq.L-1 with a mean of 175.5±25.9 mBq.L-1, from 129.5 to 302.7 mBq.L-1 with a mean of 247.8±40.5 mBq.L-1 and from 299.7 to 467.9 mBq.L-1 with a mean of 379.6±45.3 mBq.L-1, respectively. The external indoor and outdoor background gamma radiation levels have also been measured by using an ionization chamber survey meter. The external indoor gamma dose rate is found to vary from 0.14 μGy.h-1 to 0.22 μGy.h-1 with a mean dose rate of 0.18 μGy.h-1. The outdoor dose rate is found to vary from 0.12 μGy.h-1 to 0.23 μGy.h-1 with a mean value of 0.17 μGy h-1. The annual average effective dose is found to be 0.96 mSv.y-1 (96 mrem.y-1) taking into account the indoor and outdoor occupancy factors 0.8 and 0.2 respectively. This value is comparable with those of world values. This study gives a baseline of radioactivity and external indoor and outdoor radiation levels in the proposed nuclear power plant site area at Rooppur and will be helpful to correlate the radioactivity measured after operation of the reactor.
