Liquid scintillation counter calibration approach for 90 Sr detection and testing performance of TK100 resin.

90 Sr detection efficiency determination was applied for liquid scintillation counting (LSC) by computing a model for the relation between detection efficiency and the time passed since radiochemical separation. This allowed more flexibility in analysis times after separation as the model accounts for 90 Y in-growth. Establishment of secular equilibrium was therefore not required for LSC measurements. In addition, this approach increases counting efficiency compared to classical ones as both 90 Sr and 90 Y spectrums are used. This in turn has a positive impact on minimum detectable activity. The method was validated using proficiency test samples for both Čerenkov radiation measurement and scintillation cocktail measurement. Commonly used extraction material Sr-resin was compared to alternative, TK100 resin. Inductively-coupled plasma mass spectrometry measurements for recovery determination showed limitations for TK100 usage due to incomplete Sr retention on the resin. Limitations were further confirmed by LSC activity measurements.