Development of Electret Technology to Measure Indoor Radon-Daughter Concentrations: Final Report (Phase 1)

摘要

A new type of radon progeny monitor called an electret radon progeny integrating sampling unit (E-RPISU) was developed and demonstrated which uses an electret ion chamber to measure the progeny concentration. A conventional 1 LPM particulate air sampling system is used to collect the progeny on a 35 cm (sup 2) filter which is mounted on the side of the electret ion chamber such that the collected progeny are exposed to the inside of the chamber. The alpha radiation emitted by the progeny collected on the filter ionizes the air in the 220 ml chamber. The ions of opposite polarity collect on the surface of the 127 mu m thick electret and reduce its surface voltage. A specially built surface voltmeter is used to measure the electret voltage before and after sampling. The electret voltage drop which occurs during the sampling period is shown to be proportional to the time integrated progeny concentration. Two prototype systems were fabricated and tested in homes and in calibrated radon chambers. The resulting data are presented and analyzed. The calibration factor for the E-RPISU ranged from 1.5 to 2.0 V/mWL-day depending on the electret voltage. Two of the E-RPISUs were delivered to UNC Geotech for further testing. 32 refs., 11 figs., 5 tabs.