A Continuous Radon Progeny Monitor with a Vacuum Vessel by Alpha Spectrometry

A continuous monitor for accurately measuring long-term concentrations of low environmental radon progeny was developed in order to estimate the environmental influence of radon around a closed uranium mine. It is important to measure radon progeny concentration because almost all dose from radon is caused by its short-lived progeny. The various features of the monitor are a large sampling flow rate with 80 l.min-1 and the use of alpha energy spectrometry in a vacuum vessel. These have been adopted to obtain high sensitivity and resolution. Use of a long roll-type membrane filter and a reliable automatic system enabled continuous measurement for more than one month. The measurements using the monitors around the closed mine were carried out and the environmental effect was estimated to be less than 1 mSv.y-1. (author)