RAPID-DETERMINATION OF RADON DAUGHTERS AND OF ARTIFICIAL RADIONUCLIDES IN AIR BY ONLINE GAMMA-RAY SPECTROMETRY

For the determination of airborne radionuclide concentrations in real time, a fixed filter device was constructed which fits directly onto a germanium detector with standard nuclear electronics and a multichannel analyzer buffer connected via a data line to a personal computer for remote control and on-line spectrum evaluation. The on-line gamma-ray spectrometer was applied to the study of radon decay product concentrations in ground-level air and to the rapid detection of any contamination of the environmental air by artificial radionuclides. At Munich-Neuherberg, depending on the meteorological conditions, the measured air concentrations of 214Pb, the first gamma-ray-emitting member of the Rn-222 decay series, varied from about 1 to 50 Bq m-3. For the artifical radionuclides Co-60, I-131 and Cs-137 the detection limits were determined as a function of the varying natural radon daughter concentrations at sampling and counting times of 1 h or 1 day. For these radionuclides minimum detectable air activity concentrations of 0.3 or 0.001 Bq m-3, respectively, were obtained at low radon daughter levels. At high radon daughter levels the respective detection limits were found to be higher by a factor of only about 2.