The IAEA confirms the Hidex ULLA’s suitability for contemporary ultra-low-level tritium analysis
13 November 2024
At a glance
> In a recent study, the ultra-low-level analyser’s detection levels was found to address key analytical challenges posed by significantly reduced 3H levels.
> The IAEA’s Isotope Hydrology Laboratory rigorously tested the instrument, finding it “exhibited excellent stability and linearity over extended measurement periods.”
> The Hidex ULLA now provides researchers with an alternative to the discontinued Quantulus 1220.
The challenges in 3H analysis
3H plays a crucial role in hydrogeological and environmental studies, being used to evaluate groundwater ages, estimate aquifer recharge rates, and investigate water pollution. First anthropogenically introduced into the environment by nuclear weapons testing in the middle of the 20th century, this caused a significant increase in 3H levels, but these have significantly reduced since the banning of such testing to low steady-state and original background levels. This has introduced analytical limitations in studies using 3H, bringing about a demand for ultra-low-level testing and a need for a highly sensitive instrument since the discontinuation of the Quantulus 1220.
With the introduction of the Hidex ULLA in 2022, true ultra-low-level analysis has been made available again. In a recent study by the International Atomic Energy Agency, the ULLA was rigorously tested at its Isotope Hydrology Laboratory (IHL) to assess its efficacy in measuring low 3H concentrations in environmental water samples.
Absolute counting of environmental radionuclides
The ULLA improves detection efficiency through the use of three high-precision PMTs, superseding traditional dual-PMT designs like the Quantulus 1220. By using three, the ULLA can offer quench corrections without internal or external standard sources through the Triple-to-Double Coincidence Ratio (TDCR), offering absolute counting for 3H and other environmental radionuclides like 14C.
Furthermore, to reduce interference from cosmic radiation, the ULLA is equipped with a 550 kg internal Pb shield and an active guard detector. This consists of a plastic scintillator surrounding the counting chamber, coupled to a PMT, to detect and quantify environmental or cosmic background radiation. The active guard allows for the subtraction of background pulse events affecting the sample vials.
“High precision and accuracy”
The Hidex ULLA’s performance exceed expectations, with the IAEA noting, "The ULLA demonstrated high precision and accuracy in measuring ultra-low-level tritium concentrations in environmental water samples [and] exhibited excellent stability and linearity over extended measurement periods (1 month),” which is crucial for long-term environmental monitoring and research.
The study confirmed that its detection limits are ideal for contemporary 3H levels in environmental water samples, addressing key analytical challenges, and positioning it as a robust, reliable instrument for ongoing and future detection requirements.
Find out more
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