An automated gross alpha/beta activity monitor applied to time-resolved quantitative measurements of 222Rn progeny in air.

Automated monitors for the determination of airborne radioactivity are widely in use as early warning systems for nuclear emergencies; however, the data acquired for this purpose are seldom used for analyzing spatial and temporal variations of natural radioactivity (especially radon and short-lived decay products). This paper shows that a specific type of airborne gross alpha/beta activity monitor, applied in several European emergency networks, can be effectively used to study the transport of 222Rn progeny in the outdoor environment. Real-time recordings (10-min sampling time) can, independent of the actual equilibrium ratio, be converted to the equilibrium-equivalent decay-product concentration (EEDC) of 222Rn. Medium volume air sampling and a slow-moving tape air sampler yield a low detection limit of < or = 0.1 Bq m-3. This paper further describes all factors and processes contributing to the uncertainty in the data obtained in this way; the total error in single recordings is estimated at 20-25% (95% confidence interval). Data of 222Rn progeny obtained from the Dutch National Radioactivity Monitoring network agree with results of other radon surveys.