engleski

Rapid method for tritium measurements with liquid scintillation counting on Quantulus 1220

Taking into account the tritium low level in the environment, special conditions have to be fulfilled in order to obtain accurate and reliable tritium measurements. Low activity concentration of natural water samples demands high and stable overall efficiency of counting system for the detection of low energy beta particles together with a low and stable background. Results of experiments were obtained using Ultra Low Level Liquid Scintillation Spectrometer Wallac 1220 Quantulus with EASYView and WinQ software. To optimize tritium analysis in waters by ultra-low background liquid scintillation spectrometer Quantulus 1220 the optimization of sample/scintillant ratio, choice of appropriate scintillation cocktail and comparison of their efficiency, background and minimal detectable activity (MDA), the effect of chemi- and photoluminescence and combination of scintillant/vial were performed. Accessible cocktails in our laboratory at this moment are OptiPhase HiSafe 2 and OptiPhase HiSafe 3 which we used for comparison of their efficiency, FOM values, background and minimal detectable activity (MDA). Possible interference of chemiluminescence and photoluminescence in liquid scintillation counting in energy range of 3H had been investigated, we determined maximal waiting time for background and samples with very low/high activity and estimated half-life of chemiluminescence decay. ASTM D4107-08 method had been successfully applied in our laboratory for two years. The goal of this paper is to demonstrate development and optimization of new direct method in our laboratory proposed by Pujol and Sanchez-Cabeza 1999, which turned out to be faster and simpler than ASTM method. The calculated efficiency for OptiPhase HiSafe 2 and OptiPhase HiSafe 3 were (35.1 ± 0.5)% and (30.5 ± 0.6)% , respectively. The minimum detectable activity achieved was 2.0 Bq·1-1 for a total counting time of 300 minutes.

tritium; LSC

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