A recently published research study evaluated the performance of the ultra low level Hidex ULLA instrument for measurement of ultra-low-level tritium levels from environmental water samples. The study is one of the first to assess the performance of Hidex ULLA introduced to the market in 2022 to fill the market gap of low counts per minute measurements.
Tritium (3H) is a naturally occurring radioactive isotope of hydrogen that was anthropogenically introduced to the atmosphere as a result of nuclear bomb testing during the 1950s and 1960s. It remains a vital tracer in isotope hydrology for various applications including studying water pollution levels, quantification of critical zone hydrology, and assessing the age of groundwater.
Why does tritium analysis require low detection limits?
The level of tritium has significantly declined over time requiring laboratories to depend on costly techniques or analytical instruments with extremely low detection limits. Such an analytical instrument has been absent from the liquid scintillation market in the last decade until Hidex developed and launched the ultra low level analyzer in 2022.
How was the instrument performance evaluated?
This study, conducted independently by the IAEA with technical support from Hidex, studied whether the Hidex ULLA can accurately quantify low tritium levels. In the study, test water samples in triplicates were compared to 3H-free (dead water) water samples for background signal, and NIST-traceable standards for counting efficiency.
Key features of the instrument include three photomultiplier tubes utilising triple to double coincidence ratio (TDCR) method and a digital lead shield. The testing took into account, instrument stability and linearity over the period of a month and 3H sample measurements were compared to a conventional Quantulus 1220.
What did the researchers conclude from the study?
Parameters that were optimised in the study include the coincidence time and the tritium counting window also known as the region of interest (ROI) to achieve the highest figure of merit (FoM). The instrument showed high precision and accuracy in measurements with the researchers reporting excellent agreement among triplicates with minimal deviations at very low tritium levels.
The study concluded that the Hidex ULLA counter was an accurate and reliable instrument for the detection of modern-day tritium levels from environmental water samples. The study reported that a comparison with the Quantulus 1220 was feasible. Typical values for FoM and DL for the Quantulus 1220 instrument, using a similarly optimized counting procedure in the same facility, were 1245 and 5.77 TU, respectively, with a background signal of 0.58 CPM—results consistent with those reported for the ULLA system
This post is based on the research article titled " Enhancing low-level tritium detection in environmental waters: assessing the Hidex ULLA liquid scintillation counter " by Lorenzo Copia, Leonard I. Wassenaar, Risto Juvonen, and Timo Oikari, published in Journal of Environmental Radioactivity, 2024. The content of the study has been summarised, for a more comprehensive understanding, please refer to the original publication.
