Radon and Thoron (222Rn and 220Rn) Concentration Distribution Study on Three Detection Planes inside of a Closed Room Using Nuclear Track Methodology

Abstract

Abstract:The aim of this study is to determine the indoor radon and thoron concentration distribution on three detection planes, inside of a controlled closed room with microclimate conditions with NTM (Nuclear Track Methodology), using CR-39 Lantrack® bared detectors. One hundred sixty two (162) 1.9 cm × 0.9 cm CR-39 polycarbonate chips were placed in each one of the three planes, 2.0 m × 2.0 m square structures, distributed uniformly in 18 columns and 18 lines, in each plane. After three months exposure to indoor radon and thoron inside of the closed room, with a main concentration value of 862 ± 49 Bq/m 3 , all the detectors were chemically etched in KOH-6.25M solution to 60 ± 1 °C for 18 h, following the well established protocols for indoor radon survey, by the Dosimetry Applications Laboratory of the Physics Institute, UNAM (National Autonomous University of Mexico) and later on read by DIAS (Digital Image Analysis System).The results show that the radon and thoron concentration distribution is not homogeneous in anyone of the planes faces. The six faces of the three planes measured, have a very particular distribution. From the results, it can be observed that each side of each plane shows a peculiar distribution, with gradients of concentrations higher than 50% from one area to another of the same measured plane. These results can help to understand the dynamics of the radioactive gases, and their measurements.