Regulation and control methods for the unattached fraction of 220Rn progeny in a 220Rn progeny chamber

Abstract

The unattached fraction of 220Rn progeny is one of the key parameters in lung dose evaluation models. To study the behavior of unattached 220Rn progeny and to prepare for calibration of the unattached 220Rn progeny monitors, a 220Rn progeny chamber that could stably regulate different unattached fractions of 220Rn progeny was established. A recirculation loop to eliminate the effects of the sampling and a loop connected to the dilution chamber to supplement the carrier aerosol were set up. Also, a theoretical model regarding the regulation of the unattached fraction of 220Rn progeny was established. Continuous measurements of the unattached fraction were conducted using the combination of a single-layer wire screen and a filter membrane. The experimental results showed that, under different aerosol levels, the relative standard deviation (RSD) of 212Pb concentration during the continuous samplings was within 10.7% and the RSD of the unattached fraction of 212Pb was within 9.9%. The relative deviation between the theoretical and the experimental values of 212Pb concentration was within 16.7% and the model calculation values of the unattached fraction of 212Pb were consistent with measured results.