A portable, battery-powered, continuous airborne {sup 222}Rn sampler
- Environmental Measurements Laboratory, New York, NY (United States)
The Polyport, designed at the Environmental Measurements Lab (EML) for deployment in atmospheric balloons or remote areas, was laboratory and field tested to determine its effectiveness in collecting {sup 222}Rn gas in dry and humid air. Twelve 6-cm long tubes, each containing 0.4 g of a new hydrophobic Beaded Carbon Molecular Sieve (BCMS) material, are housed within the 27-ounce battery-powered Polyport unit. Each sorbent tube individually adsorbs {sup 222}Rn under dynamic sampling conditions of 1-2 h duration. The exposed sorbent is later weighed for water uptake, transferred and counted in a low background liquid scintillation (LS) counter that detects a and 0 emitting {sup 222}Rn progeny with >250% counting efficiency. Each sorbent tube can be {gamma}-counted if it contains sufficient adsorbed {sup 214}Pb and {sup 214}Bi activity above background. The variables tested were sample flow-rate (SFR), temperature, sampling time and relative humidity (RH). At STP and an optimum SFR of 5 L h{sup -1}, the sorbent`s {sup 222}Rn Collection efficiency (CE) dropped from 58% to 15% as RH increased from 20% to 80%. A single calibration curve was developed to estimate the {sup 222}Rn CE, based on data obtained from the amounts of both {sup 222}Rn and water vapor adsorbed by the BCIVIS material over a 20 to 35{degrees}C degree temperature range. This calibration curve was used in 2 field tests and the hourly {sup 222}Rn levels compared with the levels obtained using the EML Radometer, an alternative {sup 222}Rn measuring device. The minimum detectable {sup 222}Rn concentration at STP, for both an hourly Polyport sample and an hourly LS count, was about 2 Bq m{sup -3} (0.12 pCi L{sup -1}) at 20% RH, based on the optimum SFR, 58% CE and 6 mBq lower limit of detection of the LS counter.
- OSTI ID:
- 393955
- Report Number(s):
- CONF-9607135--
- Journal Information:
- Health Physics, Journal Name: Health Physics Journal Issue: Suppl.6 Vol. 70; ISSN HLTPAO; ISSN 0017-9078
- Country of Publication:
- United States
- Language:
- English
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