Measurement of naturally occurring radionuclides in geothermal samples and assessment of radiological risks and radiation doses

Abstract

Total of 26 geothermal water and their residues collected from six well in the geothermal power plant territory were measured by gamma-ray spectrometry. Apart from two geothermal water samples, all geothermal water samples were found below the minimum detectable activity (MDA) values. 226Ra activity concentrations in residue samples were measured from 40±4 Bq kg-1 to 2694±85 Bq kg-1. 232Th activity concentration of residue samples are varying from 33±4 Bq kg-1 to 2388±85 Bq kg-1. 40K activity concentrations of residue samples are ranged between MDA to 967±30 Bq kg-1. The radium equivalent activities of samples are varied from 91±8 Bq kg-1 to 6161±46 Bq kg-1. The annual effective doses of residues were calculated lower than permitted dose rate for public, i.e. 1 mSv y-1. However it was found that if parameter values are changed additional annual effective doses can rise over the reference level of 1 mSv.