Spectrometric determination of low activities of gamma emitters in water samples

Two variants of the ISO 10703:1997 procedure were developed: (i) the partial substitution of the reagents, thereby reducing the mass of the dry residue by a factor of 2; (ii) preparation of two gamma spectrometry sources by selectively precipitating the radioiodines onto one, and the rest of the radioactive cations onto the other. In variant (ii) the time required to prepare a 131I source from 20 l of water is 2.5 days, and the detection limit is 0.9 mBq/l.