Effective dose evaluation for external exposure from surface soil by using resrad-onsite code

Abstract

An annual effective dose evaluation from Dong Nai surface soil (45 samples) to humans was carried out in this work. ResRad-Onsite software has been applied to estimate the maximum exposure dose by considering different exposure levels across an area of ​​5905.7 km2 with a topsoil thickness of 20 cm. The calculation grid used in ResRad Onsite software is divided in the form of a circle of radius 3, 5, 10, 20, and 30 km, respectively, calculated from the circle center in terms of 16 wind directions. A high-purity germanium detector (HPGe) was used to determine 238U, 232Th, 226Ra, 137Cs, and 40K isotopes. The range activity concentrations of them were found to be 6.46 ÷ 48.11; 13.95 ÷ 58.75; 5.71 ÷ 35.27; 0.15 ÷ 1.23 and 6.7 ÷ 222; mBq/g, respectively. The isotope 239,240Pu was determined by the radiochemical separation method, measured on the alpha spectrometer system, and the calculated value range is 0.009 ÷ 0.073 mBq/g. The activity of 90Sr was determined by separation technique, measured on a low-background alpha/beta total counting system (MPC 9300) with a calculated value range of 0.10 ÷ 0.83 mBq/g. By ResRad-Onsite code, the external effective dose derived from the ground (excluding Radon’s contribution) is calculated to be 170 ÷ 658 µSv/year with an average value is 368.6 µSv/year. The external dose from the soil is 136.5 µSv/year (accounting for 37%). The results showed that the annual radiation dose distribution derived from the ground equivalent to the average of some different regions in the territory of Vietnam and the world. In addition, the external effective dose from the ResRad-Onsite code tended to be about 1.36 times smaller than the practical measured due to the library’s different dose conversion coefficients.