Investigation on Thoron Progeny and Radon Progeny Concentrations in Living Environment and an Estimation of Their Effective Dose to the Public

Abstract

This study was conducted to investigate the concentrations of thoron (²²⁰Rn) progeny and radon (²²²Rn) progeny and to compare the radiation exposure due to them in different kinds of dwellings. The results indicated that thoron progeny concentrations indoors might strongly depend on the kinds of building material used in each dwelling, whereas the radon progeny concentration did not depend on the kinds of building material. The average thoron progeny concentration in the traditional Japanese dwellings with soil wall was 3.22Bqm^-3, and the radon progeny concentration in the dwellings was 8.35Bqm^-3. The annual effective dose equivalent to thoron progeny was 1.19mSv, which was higher than that of radon progeny (0.82mSv) in the same dwellings assuming an occupancy factor of 1.