Radiation dose estimation for indoor radon, thoron and their progenies using a stochastic method—a small-scale survey in Wuhan, China

Passive radon monitors with CR-39s are widely used in major epidemiological surveys. However, the conventional CR-39 track density determining strategy makes it difficult to accurately estimate the concentration because of the heterogeneity of tracks on CR-39s. This study introduced a stochastic method, Latin hypercube sampling, to improve the track density determining strategy and provide the probability distribution of 222Rn concentration and equilibrium equivalent thoron concentration. The first 222Rn and 220Rn discriminated survey was conducted in Wuhan, China, in 2018 using RADUET® and deposition-based passive 220Rn progeny monitors and applying the stochastic method to the measurement. The results indicate that the stochastic method could decrease the effects of the track heterogeneity on the CR-39s and provide reliable results. The 220Rn progeny contributed more than 40% of the total inhalation dose in the survey, which cannot be ignored in urban family dwellings.