The distribution of natural radionuclides 40K, 228Ac, and 226Ra on Romanian Territory: a radiometric study

To estimate the radiation hazard due to the natural terrestrial radioactivity, 598 samples of soil covering the entire Romanian territory were collected and analyzed for the distribution of natural radionuclides K-40, Ac-228, and Ra-226. The ultra-low background Slanic-Prahova underground laboratory was used to determine the gamma-ray-specific activity of these radioactive isotopes with an uncertainty between 5 and 20%. All these data permitted to establishing a set of 2D maps illustrating the distribution of specific activity of each radionuclide as well as of the resulting air dose rate, all of them illustrating an heterogeneous distribution, increased values being displaced on the western and south-western territory. Mediated over 598 points, these determinations led to a value of annual effective dose of 0.7 +/- 0.15 mSv/y and an external hazard index of 0.46 +/- 0.1, both attesting to a radioecologically safe environment for human activity.