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

International audienceThe new European legislation imposes a lower threshold for radioactivity in drinking water.. This requires the development of more sensitive and reliable analytical methods. This work presents an improved a-spectrometric technique to determine the radium-226 activity in aqueous solution relying on the radium adsorption onto a thin manganese oxide layer followed by a-measurement. The preparation of the MnO2 deposit has been optimized as well as the radium adsorption conditions. Detection threshold and limit of 5 and 10 mBq .L-1, respectively, with a 10% (95% confidence) uncertainty are currently reached. This paper reports on the overall technique and on its application to assess the radium-226 activity in 28 French mineral waters. In addition, the gross alpha- and beta -activities have been evaluated using proportional counting while the uranium concentrations were derived from ICPMS