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Measurement of Xe-133 in air by absorption in polycarbonates - detection limits and potential applications

The Bisfenol-A based polycarbonates possess a high absorption ability to noble gases. On this basis a method for measurements of radioactive noble gases in different media has been recently proposed. In the present work the absorption-in-polycarbonates method for measurement of activity concentration of 133Xe in air is explored. The potential for practical application of the method depends on the achievable detection limits. The Minimum Detectable Activity Concentration (MDAC) is estimated, considering that polycarbonates are exposed to 133Xe in air and then measured by a 24.9% HPGe detector. The dependence of the MDAC on the exposure and the measurement duration is estimated. To estimate the MDAC, the activity of 133Xe absorbed in the polycarbonate is studied numerically using a theoretical model of the sorption and desorption processes. The influence of the natural 222Rn on the MDAC for 133Xe is also taken into account. The MDAC that could be achieved with plate-shaped polycarbonates exposed between 24 h and 96 h and measured for 24 h in 1000 ml Marinelli beaker is in the range 200 Bq/m3 - 130 Bq/m3. This MDAC is two orders of magnitude lower than the recommended detection limits for monitors for discharges of 133Xe to the atmosphere from NPPs, but higher than the concentration of 133Xe in the environmental air. The method is applicable for technological monitoring in nuclear installations. It is feasible for environmental monitoring during and after a major nuclear accident and for homeland security applications related to detection of atmospheric transborder radioactivity transfer.