A technique for discrimination of radon (222Rn) and thoron (220Rn) in soil-gas using solid state nuclear track detectors

A technique for discrimination of radon (222Rn) and thoron (220Rn) in soil radon emanometry using SSNTDs has been described. It is based on the large ratio of their half lives and consequent difference in their diffusion lengths. It can be computed that a length of about 25 cm of an air column is adequate to eliminate thoron almost completely while radon is not much affected. Theoretical and experimental curves demonstrating the discrimination of radon and thoron using Kodak Pathe LR-115 cellulose nitrate films have been presented. The design of a sonde for the estimation of radon as well as thoron in soil gas for uranium coefficient of radon in air at room temperature has been determined experimentally. (author)