Michaela Fröhlich (Canberra): Enabling ultra-sensitive measurements of strontium-90, lead-210 and actinides

Accelerator mass spectrometry (AMS) with its ultra-low detection limit and sensitivity, offers a great variety of applications for a range of radionuclides. For strontium-90, a major fission product primarily introduced into the environment through atmospheric nuclear weapons testing, AMS provides superior sensitivity and efficiency compared to traditional radiometric methods. However, challenges such as isobaric interference from zirconium require careful chemical separation and optimisation of the instrumental setup. Initial work carried out at the Heavy Ion Accelerator Facility will be presented.
AMS is also critical for ultra-low background studies in dark matter experiments such as SABRE South - a direct detection dark matter experiment based on ultra-pure NaI(Tl) crystals. Residual radioactivity from impurities must be quantified and ideally minimised to reduce background signals by careful selection and development of ultra-pure materials and equipment. Here the focus is on lead-210 and the current status will be discussed, paving the way for AMS-based measurements supporting the SABRE-South experiment.
Finally, corals are excellent temporal archives providing insights into radionuclide deposition from historical nuclear tests. Analysis of a Porites Lutea coral from the Montebello Islands revealed distinct uranium and plutonium signatures linked to the nuclear testing program conducted there. Temporal variation of their isotopic concentrations and ratios with a time resolution of a few months will be reported.