Detection of Radon Decay Products in Rainwater

Abstract

The Argonne National Laboratory-East (ANL-E) Environmental Radiation Monitoring System measures and records ambient radiation levels and provides detection capability for radon decay products in rain clouds. These decay products in rainwater tracked into a facility on the shoes of workers can cause false alarms from hand and shoe monitors. The monitors at ANL-E can easily detect the radon decay products, and the 19.6 and 26.8 min half-lives of the beta-particle emitters are long enough in many cases for sufficient activity to still be present to initiate a contamination alarm when the shoes are checked for radioactivity. The Environmental Radiation Monitoring System provides a warning when precipitation contains elevated levels of radon decay products. It is based on a prototype developed at the Super Collider Laboratory. During its first year of operation there were nine alarms from radon decay products with an alarm trigger point set at 30% greater than background. The alarms occurred at both monitoring stations, which are approximately 1,000 m apart, indicating large diameter radon clouds. The increases in background were associated with low atmospheric pressure. There was no correlation with radon released from the coal-burning steam plant on the site. Alarms also occurred when short-lived accelerator-produced radioactivity in the exhaust stack plume passed over the NaI(Tl) detector in one of the stations. The 450 MeV proton accelerator near the station produced 12C, 13N, and 15O by spallation of air nuclei. The gamma-ray spectrum from the plume from the accelerator exhaust stack was dominated by the 511 keV annihilation gamma rays from decay of these radionuclides. These gamma rays were easily distinguished from the 609 keV, 1,120 keV, and 1,764 keV gamma rays emitted by the radon decay products.

214Bi/214Pb radioactivity ratio three-year monitoring in rainwater in Prague

“…The present study confi rms the results obtained by other authors in similar studies through different measurements and methodologies of analysis [1,[9][10][11][12][13]. Anomalies of 214 Bi/ 214 Pb ratio, during rainfall events, refl ect anomalies of the 222 Rn (their progenitor) that has a half-life of about 3.82 days and is Bi/ 214 Pb ratio (in black) and hourly ambient dose equivalent rate (in grey) with their anomalies results as Z-score (in black triangles and grey circles, respectively) obtained from the application of the proposed hybrid method for time-series analysis (multiple linear regression + empirical mode decomposition + support vector regression) during the period December 2014 -January 2018.…”

“…Such monitoring can be carried out in different ways and the most common ways are gamma-ray spectrometry and gamma dose rate measurements [1,[6][7][8][9]. In this framework, the continuous monitoring of radioactivity ratio of 214 Bi/ 214 Pb as tracers in rainwater was carried out by several works [9][10][11][12]. During atmospheric thermal inversions, there is an increase in the concentration of natural gamma-emitting radionuclides of the short-lived 222 Rn progeny ( 214 Pb and 214 Bi with half-lives of 26.9 min and 19.9 min, respectively) that causes an increase in the total natural gamma background.…”

“…These descendants of radon are incorporated in the raindrops and dragged to the ground [13]. In the atmospheric mixing of the overall variability in ambient gamma dose, radon variability attributable to diurnal changes contributes less than radon variability during precipitation periods [9,10]. Therefore, any information about radon progeny concentrations could be useful for modelling the variation of the natural gamma background depending on the 222 Rn fl ux and the variable atmospheric conditions [11,12].…”