Estimation of the External Gamma Dose Rate from Natural Radionuclides on the Territory of Bosnia and Herzegovina

The largest contribution to global exposure of population by ionizing radiation gives the natural sources of external exposure, that are consisted of two main components: cosmic and terrestrial radiation. In the paper, contribution of particular components of primordial radiation and 137Cs from soil on the total dose rate was evaluated. The average values of radionuclide concentration on 10 investigated localities were: 39.9 ± 9 Bq/kg for 238U, 33 ± 9 Bq/kg for 226Ra, 32 ± 7 Bq/kg for 232Th and 434 ± 108 Bq/kg for 40K, while the average value of the ratio 238U/226Ra was 1.15 with standard deviation of 0.11 (or ± 9.6 %). The average absorbed dose rate on 1 m above the soil was: 17 ± 6 nGy/h for 238U series, 21 ± 4 nGy/h for 232Th series, 18 ± 5 nGy/h for 40K, 35 ± 3 nGy/h for cosmic radiation, 111 ± 15 nGy/h for direct measurements by gamma rate meter and 19 ± 9 nGy/h for estimated dose rate of 137Cs in the soil. The average percentage of particular components of radiation in total absorbed dose rate were: 16 ± 4 % for 238U series, 19 ± 4 % for 232Th series, 16 ± 3 % for 40K, 32 ± 3 % for cosmic radiation, and 17 ± 8 % for 137Cs with note that primordial radionuclides (238U series, 232Th series and 40K) participate with average 51 ± 7 %. (author)