Measurement of gross alpha and beta in air filter samples by using liquid scintillation counter

The determination of gross alpha and gross beta in particulate air filter samples was carried out by alpha, beta discrimination method using Liquid Scintillation Analyzer by setting the PSA value at 55 for 5 ml 0.1 HCl plus 15 ml of Ultima Gold AB cocktail by using ²⁴¹Am and ⁹⁰Sr/⁹⁰Y sources. The standardized method was compared with the gross alpha and gross beta activity determined by conventional method of direct counting with end window G.M. counter and ZnS (Ag). The minimum detectable activity of LSA method was found to be 9.3 mBq and 17.7 mBq for gross alpha and gross beta respectively for 6000 sec compared to the conventional method of 9.8 mBq and 189 mBq respectively at the same counting time. The result of analysis by both method indicate that the alpha, beta discrimination set up of LSA method is highly effective in the determination of low level alpha, beta activity in air filter samples. (author)