MEASUREMENT OF NATURALLY OCCURRING RADIONUCLIDES IN GEOTHERMAL SAMPLES AND ASSESSMENT OF RADIOLOGICAL RISKS AND RADIATION DOSES

摘要

The analysis of ~（226）Ra, ~（232）Th and ~（40）K radionuclides has been carried out in geothermal water and residue samples collected from six wells of geothermal power plant and disposal site, using gamma-spectrometry system equipped with a high-purity germanium detector. The activity concentrations of nine geothermal water samples were found to be lower than minimum detectable activity (MDA) values. The activity concentration of the residue samples ranged from 40 ± 4 to 2694 ± 85 Bq kg~（-1） for 226Ra, 33 ± 4 to 2388 ± 85 Bq kg~（-1） for ~（232）Th, and MDA value to 967 ± 30 Bq kg~（-1） for ~（40）K. In the study, some radiological indexes were examined and found to be higher than the reference values for majority of the residue samples. The annual effective doses arising from some residue samples were calculated to be higher than the permitted dose rate for the public, i.e. 1 mSv y~（-1）.