INVESTIGATION OF RADIOACTIVE COUNTING SAMPLES OF SELECTED RADIONUCLIDES IN VARIOUS LIQUID SCINTILLATORS

This article presents some results of the investigation of radioactive counting samples prepared with the use of liquid scintillators. Liquid scintillation cocktails Atomlight (NEN) and Opti-phase HiSafe II (LKB) in standard glass vials of 20 ml volume were used. The counting efficiencies for several radionuclides in the above scintillators were compared. Two different experimental methods for measurement of the samples were applied: (1) The 4-pi-beta-gamma coincidence method with a liquid scintillator in the beta channel (for beta-gamma and EC-gamma emitters). In this case the counting efficiency was calculated according to the formula epsilon(beta) = N(c)/N(gamma). (2) The triple-double coincidence ratio (TDCR) method (for pure beta or EC emitters). In this case the counting efficiency was calculated as epsilon(D) = N(D)/N(O), where N(D) - the total number of double coincidences, N(O) - the number of disintegrations in the sample. The effect of the complexing agents HDEHP (diethylhexyl phosphoric acid) and EDTA (ethylenediaminetetraacetic acid) on the quality of the counting samples was studied. The application of the water solution of EDTA to prepare the counting samples of a few radionuclides improved both the counting efficiency and the stability of the samples. A slight quenching effect of HDEHP was observed.