Measurement techniques of thoron and thoron progeny concentrations. Active and passive methods and their calibrations

The measurements of 220Rn and its progeny concentrations are affected always by 222Rn and its progeny. Various types of measurement techniques of 220Rn and its progeny concentrations had been developed by using the differences between half lives of 222Rn and 220Rn and energies of α- and γ-radiations emitted from 222Rn and 220Rn progeny. Active 220Rn measurement techniques include the methods of ionization chamber, scintillation cell, two filter, liquid scintillation and activated charcoal. Decay, α-spectroscopy and integrating methods have used to measure 220Rn progeny concentrations collected on a filter. Passive monitors are suitable to survey mean 220Rn concentration in the living environment. Cup and activated charcoal monitors have been reported for the passive 220Rn methods. Calibrations of active and passive 220Rn monitors should be carried out in the calibration chambers with 220Rn source outside and inside, respectively. (author)