Performance test of passive radon-thoron discriminative detectors on environmental parameters

This paper describes how humidity, wind and ambient aerosols in air influence the detection responses of passive detectors. Two types of alpha track detectors based on a passive radon (Rn-222)-thoron (Rn-220) discriminative measurement technique were used: the Raduet and Radopot detectors that were developed and calibrated by the National Institute of Radiological Sciences, Japan. The initial experiment showed that the infiltration rate of Rn-220 onto sponges with a high air exchange rate for the Raduet detectors was one third lower than that onto filters for the Radopot detectors. Little distinct dependence on humidity was observed for the Rn-222 detection responses of both detectors. For Rn-220, the detection responses of both detectors for the high air exchange rate seemed to decrease slightly at high humidity conditions. The Rn-220 detection responses of the Radopot detectors had little influence from wind speed. The Rn-220 detection responses of the Raduet detectors for the high air exchange rate seemed to decrease at low wind speeds. Furthermore, there was little difference between the detection responses in the presence and absence of ambient aerosol particles because the ambient aerosols were filtered out during their passive diffusion through the sponges and filters for the Raduet and Radopot detectors, respectively. (C) 2012 Elsevier Ltd. All rights reserved.