Determination of radium-226 in aqueous solutions by alpha-spectrometry

The new European legislation imposes a lower threshold for radioactivity in drinking water.. This requires the development of more sensitive and relia ble analytical methods. This work presents an improved a-spectrometric tech nique to determine the radium-226 activity in aqueous solution relying on t he radium adsorption onto a thin manganese oxide layer followed by a-measur ement. The preparation of the MnO2 deposit has been optimized as well as th e radium adsorption conditions. Detection threshold and limit of 5 and 10 m Bq .L-1, respectively, with a 10% (95% confidence) uncertainty are currentl y reached. This paper reports on the overall technique and on its applicati on to assess the radium-226 activity in 28 French mineral waters. In additi on, the gross alpha- and beta -activities have been evaluated using proport ional counting while the uranium concentrations were derived from ICPMS.