Low-level measurement of the cosmogenic 22Na radionuclide in fresh water by ultra low-background gamma-ray spectrometry after simple radiochemical separation

A simple analytical method was developed for the determination of cosmogenic 22Na radionuclide in fresh water samples by ultra low-background γ-ray spectrometry after radiochemical separation. The method consists in pre-concentration of 22Na(Na) by a ion exchange resin column from a large volume of ca. 500-liter water samples, elution with 4M HCl from the resin, and removal of the main metal components such as Ca and Mg as carbonate precipitates and of 40K(K) as potassium tetraphenylborate K[B(C6H5)4]. The obtained 22Na fraction was successfully measured by an ultra low-background Ge detector installed in the Ogoya Underground Laboratory. (author)