Analysis of uranium, thorium and radium radioisotopes in coal seam gas associated water samples

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South Pacific Environmental Radioactivity Association
The Australian coal seam gas (CSG) industry, located mainly in eastern Australia, has grown significantly over the last decade and is now a significant contributor to natural gas production in Australia. CS6 extraction involves drilling boreholes across landscapes which intersect with coal seams. Gas is then flowed to the surface along with associated produced waters. In order to increase gas production, some wells are subjected to hydraulic fracturing which involves pumping water, chemicals and a proppant into the coal seams. The resulting flow-back waters are then collected at the surface prior to treatment and disposal. There are significant public concerns about the water quality of flow-back and produced waters associated with CSG operations, in particular the concentration of geogenic contaminants including radioisotopes such as 226Ra and 222Ra. In order to address these concerns, accurate data on water quality needs to be collected. CSG waste waters are complex, saline matrices and sensitive, robust analytical methods are required to reliably quantify the concentrations of contaminants including radioisotopes ln this work, radioisotopes of uranium, thorium and radium were analysed in CSG flow-back and produced waters samples collected from CSG bores located in Central Queensland, Australia. The water samples were processed for the determination of 233U, 238U, 228Th, 230Th, 232Th, 226Ra activity concentrations by alpha-particle spectrometry and 222Ra by gamma-ray spectrometry. GSG associated water consist of high concentrations of total dissolved solids (TDS) ranging from 800 to 10,000 mg/L. Such high salinity levels pose difficulties for the measurement of the radioisotopes of interest, resulting in low sample recoveries and poor resolution alpha spectra. This paper presents radiochemical techniques used to reduce the complex sample matrix effects in analysing CSG associated water samples. Manganese dioxide co-precipitation technique was chosen to concentrate the elements of interest, followed by the isolation of uranium and thorium using UTEVA (Eichrom) resin. The determination of 222Ra by alpha spectrometry was found to be challenging due to low sample recoveries and poor alpha spectra resolutions. This was overcome by diluting the samples in large volumes prior to lead sulphate co-precipitation, which isolates radium and barium from other metals in the samples. The developed radiochemical technique was suitable and robust for determining the radioisotopes of interest in CSG associated water samples.
Atun Zawadzki's name is not spelt correctly in the citation. It is listed as Atun Zawdzki.
Uranium isotopes, Thorium isotopes, Radium isotopes, Coal seams, Water, Australia, Boreholes, Spectroscopy, Queensland
Maizma, S., Chellappa, J., Zawdzki, A., Apte, S. King, J., Jarolimek, C., & Angel, B. (2018). Analysis of uranium, thorium and radium radioisotopes in coal seam gas associated water samples. Paper presented to the SPERA Conference 2018, "Bringing environmental radioactivity research to Western Australia, Perth, Western Australia, 6 - 9 November 2018. (pp. 56-57).