Aa Automated Gross Alpha/Beta Activity Monitor Applied to Time-resolved Quantitative Measurements of 222Rn Progeny in Air

Abstract

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.

Exposure to Atmospheric Radon

“…2), we saw no significant year-to-year changes (<15%) at five sites. This observation is in agreement with other long-term studies (21)(22)(23)(24)(25). There was no significant difference between detectors placed at 1 and 2 m, in agreement with earlier reports (8,9,26-28).…”

Diurnal variation of radon progeny

“…5. The predicted/calculated variation is mainly within an upper and a lower envelope defined by the error bars at AE22.5% around the measured values (Smesters, 1995). The average standard deviation of the experimental values is 1.33 Bq/m 3 .…”

“…Some of the measurements are therefore accomplished through the use of an on-line air sampling via a step moving filter-tape (Smesters, 1995). These measurements can be further used to analyse the spatial and temporal variations of natural radioactivity and especially radon and its short-lived decay products.…”

A simple model for describing the concentration of 212Pb in the atmosphere

“…The study by Smetsers (1995) is interesting because it derived from the Dutch National Radioactivity Monitoring Network, designed for the monitoring of nuclear emergencies, similar to our own situation. The detectors were sensitive to a and b radiation, but could not discriminate between various sources, so thoron and radon were confused.…”