A NEW APPROACH TO DETERMINING 222Rn IN AIR USING LIQUID SCINTILLATION COUNTING

I have developed a new approach to determining 222Rn in air using liquid scintillation counting (LSC). With this method, special charcoal canisters absorb the 222Rn. When the canister is connected to a standard Teflon® vial, radon is transferred to the scintillation cocktail. Exposure time is 3-7 days, with desorption and measurement taking up to 20 h. A complete set consists of 3-5 charcoal canisters per vial. An ordinary vial cap is used to close the vial after desorption for storage and counting with an LS spectrometer. A discrete charcoal canister allows up to 20 ml of cocktail per sample, which decreases the radon elution time. High-energy resolution and low background with Teflon vials allow improved sensitivity of the method compared to commercially available disposable vials. Only Teflon® vials are used in the laboratory, which prevents evaporative losses. A low detection limit down to 1.0 Bq m'3 for a 6-day exposure and 10-min counting time are easily obtained (background: 0.1 cpm; efficiency: 1.0 cpm per Bq m'3).