Measurement of thoron daughter activity levels at monazite belt areas of south India using passive detectors

A summary of the results of a study monitoring the levels of airborne α-particle activities due to thoron and daughters in residential and industrial areas of the monazite belt area in Kerala is presented. A passive detector technique using small strips of LR-115 type II nuclear track detector was used for the survey. The experimental procedures and the method used to estimate the thoron daughter concentration in milli working level (mWL) units are outlined and the results are discussed in terms of the environmental parameters. 1 WL of thoron corresponds to the potential α-energy concentration of short-lived thoron daughters in radioactive equilibrium with a thoron concentration of 280 Bq·m-3. (author)