Simultaneous determination of lead-210, gross beta and gross alpha activities of air filters by pulse shape discrimination liquid scintillation counting
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A chemical procedure for transferring deposited solid matter from a cellulose filter into the liquid scintillation cocktail has been described. The influence of chemical and color quenching on alpha and beta detection efficiency, as well as on misclassification of beta and alpha pulses was corrected by an external standard method. Under the chosen pulse shape discrimination level (PSD), the alpha and beta detection efficiencies were above 85% and spillovers of alpha and beta pulses were below 10% and 2% respectively. Determination limits for samples containing up to 200 mg of mineral matter were 0.015 mBq m−3 for alpha, 0.055 mBq.m−3 for210Pb and 0.055 mBq.m−3 for beta activity (counting time 12000 s and volume of filtered air ∼ 1000 m3). The method has been applied for routine monitoring of210Pb as well as for gross alpha and beta activities of longer-living radionuclides (T1/2.>11 hrs) in suspended air matter.
KeywordsRadionuclide Liquid Scintillation Liquid Scintillation Counting Mineral Matter Solid Matter
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