Enhancing low-level tritium detection in environmental waters: assessing the Hidex ULLA liquid scintillation counter.

Tritium (³H) is a vital tracer in isotope hydrology and environmental studies, necessitating accurate and precise low-level detection methods. This study evaluated the performance of the new Hidex ULLA Liquid Scintillation Counter for ultra-low-level tritium assays in environmental water samples. The optimization of instrumental parameters enabled accurate and reproducible ³ H measurements. Test samples (10-132 TU) were analyzed in triplicate, including ³ H-free water and NIST traceable standards. The results demonstrated excellent accuracy and reproducibility, as evidenced by Zeta scores and linearity across these tritium concentrations. The system's stability over extended measurement time periods ensured reliable performance for routine ultra-low level ³ H analysis. The optimization of key parameters such as coincidence time and region of interest (ROI) achieved the highest figure of merit (FoM) by using a 25 ns coincidence time and the DigPb open mode for optimal spectral fittings. Detection limits (DL) based on ISO11929 recommendations were significantly improved but highlighted the need for sample enrichment for most low-level environmental applications, with LSC counting times preferably exceeding 1000 min. Overall, the Hidex ULLA Liquid Scintillation Counter proved to be a robust and reliable instrument suitable for ultra-low-level tritium detection in environmental water samples.
Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Risto Juvonen and Timo Oikari reports a relationship with HIDEX that includes: employment. This study was funded by the International Atomic Energy Agency with technical support from Hidex Oy. All sample preparation and 3H measurements were conducted independently at the IAEA. Blind raw data was supplied to Hidex for advanced processing using spectral fittings algorithms. RJ and TO conducted Hidex data processing and are employed by Hidex Oy. Lorenzo Copia and Leonard I Wassenaar declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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