NUKLEONIKA 2004, 49(1):1-5

Activities of the main radionuclides from the ²³⁸U and ²³²Th series in the Uniejów geothermal water were determined by combining liquid scintillation counting with a/b separation and g-spectrometry methods. The ²²²Rn and ²²⁶Ra activities were measured after extraction of radon from 10 ml water samples to 10 ml of an Ultima Gold F scintillation cocktail directly in 22 ml scintillation vials. The samples were counted in a new generation portable liquid scintillation counter, Betascout, without separation of the phases over the period of 30 days after extraction. The average values of the specific activities were equal to 2.95 and 0.64 Bq/dm³ for ²²²Rn and ²²⁶Ra, respectively. The ²¹⁰Po radionuclide before counting was preconcentrated from 1 dm³ water samples on hydrated manganese oxide and deposited on silver discs. The discs were immersed in 10 ml of the scintillator and their activity was measured also by the same method. The average ²¹⁰Po concentration was 0.052 Bq/dm³. Activity of the remaining radionuclides was determined by g-spectrometry after their preconcentration on hydrated manganese oxides from 10 dm³ samples. The activities of two radium radionuclides, ²²⁴Ra and ²²⁶Ra, can be calculated from their basic g-lines, whereas ²²⁸Ra can be determined from its decay product - ²²⁸Ac, and were equal to 0.40, 0.65 and 0.58 Bq/dm³, respectively. The activities of ²¹⁰Pb and ²³⁸U (²³⁴Th) were below the detection limit of the method equal to 0.03 Bq/dm³. Based upon the obtained results, it can be concluded that there are not any radiological restrictions for using this water as a heat source or for balneological purposes. However, it cannot be used as drinking water, because the calculated committed effective dose from its one year consumption exceeds the WHO recommended value of 0.1 mSv.