Measurement of Pa-231 for radiological dose assessment from uranium mining
Mr Peter Medley1,2,3, Dr. Stephen Tims2, Dr. Michaela Froehlich2, Dr. Andreas Bollhöfer4, Prof. Keith Fifield2, Mr. Dominik Koll2, Dr. Zuzana Slavkovská2, Prof. Anton Wallner5
1Environmental Research Institute of the Supervising Scientist, Darwin, Australia, 2Australian National University, Canberra, Australia, 3Queensland Health, Brisbane, Australia, 4Bundesamt für Strahlenschutz, Freiburg, Germany, 5Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany
Naturally occurring radionuclides in the environment lead to a natural background exposure from ionising radiation to people. Industrial processes, such as the operational and post-remediation phases of uranium mining, can lead to increased release above natural background levels of these radionuclides into the environment. The movement and partitioning of these radionuclides in environmental systems can lead to bioaccumulation in organisms. Traditional indigenous land rights exist on many former mine sites in Australia where traditional owners may exercise their rights such as hunting and gathering. The bioaccumulation of radionuclides in traditional food items on former mine sites can therefore lead to an increased exposure to people from ionizing radiation.
The Ranger Uranium Mine in the Alligator Rivers Region (ARR) of the Northern Territory of Australia ceased all mining and milling operations in January 2021. Mine site remediation is taking place with the intention to release the former mine site to traditional owners. Detailed information on biological uptake of naturally occurring radionuclides is needed to undertake a radiological dose assessment for people intending to collect food from the site. Protactinium-231 is one of the radionuclides that have the potential to be released through uranium mining activities and to bioaccumulate in organisms. Uptake of Pa-231 has been modelled using analogue elements but has not previously been directly measured in the ARR.
AMS is the only suitable technique capable of achieving the low limits of detection required to measure Pa-231 in natural environmental samples. We have developed new, safer radiochemical methods to prepare the Pa-233 isotopic tracer and for extraction of Pa from biological samples. We report on methods development for Pa-231 at the ANU, measured activity concentrations of Pa-231 in traditional food items from the ARR and implications for potential doses from ionizing radiation to people.
Peter has Over 20 years of experience with techniques for low-level measurement of environmental radioactivity using radiochemistry, alpha and gamma spectrometry and liquid scintillation counting techniques. Peter is a current PhD student at the Australian National University, studying radiochemistry and Accelerator Mass Spectrometry (AMS).