Verification of CR-39 Technique for Attached Radon Progeny Size Distribution

Full text: A new type cascade impactor has been developed to determine the activity size distribution of radon and thoron progeny in a living environment more efficiently. The modified impactor consists of 4 stages for the collection of aerosol samples. The aerosol cut points in the impactor are set for 10, 2.5, 1 and 0.5 μ m at a flow rate of 4 L.min-1. Five CR-39 chips were used as alpha detectors for each stage. In order to separate α particles emitted from radon and thoron progeny, CR-39 detectors are covered with aluminum-vaporized Mylar films. Thickness of films is properly adjusted to allow α particles emitted from radon and thoron progeny to reach the CR-39 detectors. In addition, a 400-mesh metal wire screen was mounted as diffusion collector at the air inlet of the impactor to remove the unattached fraction of radon and thoron decay products. Validation of the technique was performed with the commercial devices. The results confirmed that the developed technique can provide us significant information to estimate the activity size distribution of attached radon and thoron progeny for dose assessment