Determination of 222Rn absorption properties of polycarbonate foils by liquid scintillation counting. Application to 222Rn measurements

This work demonstrates that a Liquid Scintillation Counting (LSC) technique using a Triple to Double Coincidence Ratio counter with extending dead-time is very appropriate for the accurate measurement of 222Rn activity absorbed in thin polycarbonate foils. It is demonstrated that using a toluene-based LS cocktail, which dissolves polycarbonates, the 222Rn activity absorbed in thin Makrofol N foil can be determined with a relative standard uncertainty of about 0.7%. A LSC-based application of the methodology for determination of the diffusion length of 222Rn in thin polycarbonate foils is proposed and the diffusion length of 222Rn in Makrofol N (38.9±1.3 µm) and the partition coefficient of 222Rn in Makrofol N from air (112±12, at 20 °C) and from water (272±17, at 21 °C) are determined. Calibration of commercial LS spectrometers for 222Rn measurements by LSC of thin polycarbonate foils is performed and the minimum detectable activities by this technique are estimated.