Pages: 67-78

Authors: Shyamal Ranjan Chakraborty

Abstract
The specific activities of ²³²Th, ²³⁸U, ⁴⁰K, and ¹³⁷Cs in undisturbed surface soil at 56 locations of Bangladesh, covering its entire area, were measured using high resolution HPGe detector. The mean specific activity concentrations of the mentioned radionuclides were respectively found to be 83.56 ± 17.96 Bq/kg, 44.35 ± 12.65 Bq/kg, 630.89 ± 173.85 Bq/kg, and 5.37 ± ±.4.87 Bq/kg. A good correlation between the activities of ²³²Th and ²³⁸U was found. The radiological parameters namely radium equivalent activity, representative level index, external hazard index, internal hazard index, absorbed dose rate, and effective annual outdoor dose rate due to the natural radionuclides were also calculated. The average values of the mentioned parameters were found to be 212.26 ± 43.93 Bq/kg, 1.55 ± 0.32 Bq/kg, 0.29 ± 0.06, 0.69 ± 0.15, 97.27 ± 20.03 nGy/h, and 119.37 ± 24.58 µSv/y, respectively. The radiation dose levels at the points of sample collection were also measured by a portable radiation dose rate-meter. The average value of the outdoor dose rate was found to be 0.20 ± 0.07 µSv/h ranging from 0.16 ± 0.02 µSv/h to 0.28 ± 0.04 µSv/h. The distributions of natural radionuclides were found to be normal. The concentration levels of different radionuclides were comparable to the corresponding reported values of the soil of different countries.

Key words: surface soil, Bangladesh, gamma spectrometry, radiation hazard index, dose rate

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