Monitoring of low-level radioactivity in ground-level air: γ-spectrometric measurements within IMIS

At the Braunschweig site of physikalisch-technische bundesanstalt (PTB), a trace survey station for monitoring the radioactivity contained in ground-level air is operated within the framework of the German ''integrated measuring and information system'' (IMIS) for monitoring environmental radioactivity and radioactivity contained in foodstuffs. In the routine operating mode of IMIS, the lower limits of detection (LLD) achieved for γ-ray emitting radionuclide measurements performed on aerosol ashes lie in the range from 0.1 μBq/m3 to 0.02 μBq/m3. A software code for data management and time series evaluation is presented. Some examples of observed contaminations of the ground-level air with traces of artificial radionuclides are compiled. (orig.)