Dobromir Pressyanov, Prof.
Sofia University “St. Kliment Ohridski”
In practice it is required to evaluate the achieved radon reduction, preferably shortly after the mitigation installation is activated. As instantaneous measurements are affected by short term radon variations, few days pre- and post-mitigation integrated measurements of sufficient sensitivity might be preferred. Within the European MetroRADON project novel detectors of sufficient sensitivity for that purpose were developed. They are based on using DVDs of low intrinsic background as track detectors, covered with Makrofol N foils. The absorption of radon by Makrofol N is very high (concentration ratio foil/air is > 100). The Makrofol N foil serves as radon absorber/radiator that greatly amplifies the signal (net track-density at etched DVDs). The achievable sensitivity is < 20 Bq m-3 for a one week exposure. The detectors are cheap and usable for measurements at many points in large buildings. A design not affected by thoron presence and temperature variations is described and discussed.