Progress of Cryogenics and Isotopes Separation , ISSN: 1582-2575
2017, Volume 20, Issue 1

Performance parameters of two Quantulus 1220 for low level tritium measurements

Abstract

Liquid scintillation counting (LSC) is the most commonly used technique for measuring low-energy beta emitters, namely for tritium. ISO 9698/2010, International Standard specifies the conditions for the determination of tritium activity concentration in samples of environmental water or of tritiated water ([³H]H₂O) using liquid scintillation counting.

This paper presents the results of a comparative study conducted with four Tritiated standard solutions, using two ultra-low level liquid scintillation spectrometers Quantulus 1220^TM. We investigated the variation of three measurement parameters: the counting efficiency, the figure of merit and the background counting rates. Measurements were performed using two ultra-low level liquid scintillation spectrometers Quantulus 1220^TM, one in service from 1998 manufactured by Wallac (Q1) and the other from PerkinElmer in service starting with 2011 (Q2). After measurements made we had 25 observations for Q1 and 63 observations for Q2, respectively.

The two ultra-low level liquid scintillation spectrometers Quantulus 1220^TM used in this study had different characteristics. The mean value of the background for Q2 is higher than the mean value for Q1, while the detection limit of Q2 is lower than that of Q1 due to higher counting efficiency. The mean value of figure of merit recorded during studied period for Q2 was higher than that of Q1. The recorded differences of studied parameters between the two ultra-low level liquid scintillation spectrometers are due to different performances of the spectrometers photomultipliers.