Using an Imaging Plate to Measure the Concentration of Radon Progeny in Air

Abstract

A simple technique was developed for using an imaging plate (IP) to estimate the individual concentrations of radon progeny in the air. The objective of this technique is to survey concentrations in high-humidity environments, such as caves, utility mains, and underground facilities.An IP called BAS-III, which performs well in extremely humid environments, was selected. The sampling flow rate was 65 liters per minute by a 47 mm-dia. glass-fiber filter (GF/F), and the grab sampling time was determined to be 5-10 minutes. One minute after the air sampling, the surface of the filter was attached directly to the IP in a prepared cassette. This was repeated six times for 10 minutes, for a total exposure of 60 minutes. Six values of Photo-Stimulated Luminescence (PSL) indicating the decay curve of the radon progeny sampled on the filter were analyzed. In environments with extremely high concentrations of radon, more accurate measurements can be obtained by making a simple distinction between PSL values for α and β rays. The lower detection limit for the equilibrium equivalent concentration (EEC) of radon was estimated to be about 20 Bqm-3. This system can be successfully adopted in humid areas.