Comparative measurements of soil gas radon concentration using thermoluminescent and track detectors

Track etch detectors are extensively used for Rn measurement in the environment because of their excellent ability to detect heavy charged particles. However, sometimes their application requires additional equipment and evaluation without automatic image analyzer can be time consuming. Moreover, due to track overlapping, track detectors are best suited for relatively low Rn concentrations. Thermoluminescent detectors (TLDs) are routinely used for detection of beta and gamma radiation, and in some cases they can be successfully used to measure other kinds of radiation, e.g. neutrons and alpha. In this study we compare the performance of TLDs and track detectors during field measurement of soil gas Rn concentration. A specially designed detector holder determines the irradiation geometry and contains either CR-39 track detectors or two sets of several (6-14) TLDs. The first set of TLDs (bare) detects both alpha and gamma and the second set is hermetically sealed and detects gamma radiation only. The response of two kinds of Bulgarian thermoluminescent materials, CaSO4: Dy and CaSO4: Dy/graphite mixture was compared to the response of reference track detectors. Measurements were carried out at three distinct sites with different Rn concentration and two types of detector sealing were tested. The obtained results suggest that TLDs can successfully be used to measure medium or higher (> 50 kBq m(-3)) soil gas Rn concentrations. Compared to track detectors TLDs extend the upper limit of detection by as much as two orders of magnitude. (C) 2004 Elsevier Ltd. All rights reserved.