Preparation of certified reference materials for gross alpha beta measurement

No Thumbnail Available
Journal Title
Journal ISSN
Volume Title
South Pacific Environmental Radioactivity Association
Gross alpha beta measurement techniques are used for rapid radioanalytical screening of both solid and liquid samples for environmental, scientific and industrial purposes. A number of gross alpha beta measurement techniques are available depending on the sample matrix and each should report the gross or total alpha or beta radioactivity relative to the alpha or beta emitting radionuclide in the calibration source. To establish measurement accuracy and reliability, certified reference materials (CRMs) which are traceable to a national standard should be used to prepare a calibration source in the same geometry as the sample. it was our aim to develop solid CRMs for gross alpha beta techniques using a quartz mineral spiked with standardised and traceable radiotracer solutions. The quartz mineral was pulverised and then sieved to prepare a starting material which had a narrow particle size distribution range to reduce the likelihood of size fractionation. A standard operating procedure for the Malvern Mastersizer 2000 was developed to assess the adequacy of the starting material with the effect of ultrasonics and pump speed being investigated. The starting material vi/as spiked with either 241Am or spiking 99Sr/90Y to prepare the alpha CRM or beta CRM respectively. The solutions were standardised by ANSTO Radionuclide Metrology to provide direct traceability to the Austral an National Standard tor Radioactivity. Spiking was performed using the acetone bath method. The sieved quartz material was mixed with acetone in a large round-bottom flask and accurately known quantities of radionuclide solution added. The flask was rotated on a rotary evaporator tor a few hours to ensure an even distribution of the radionuclide through the quartz. The acetone was evaporated, the dry spiked quartz material transferred to a poly-ethylene bottle and further homogenised by shaking for a few hours using a Turbula mixer. Homogeneity testing using 10 aliquots from each CRM and radionuclide losses on the rotary evaporator glassware and mixing vessel were established using radiochemical separation and alpha spectrometry tor 24‘Am and Liquid Scintillation Counting (LSC) for 90Sr/90Y. Each sample for testing underwent a separation and purification process that included dissolution, precipitation and re-dissolution and column purification using Eichrom® pre-packed cartridge stack of TEVA®, TRU® and Sr-Spec® resins. Canberra Alpha Analyst and Apex Alpha Counting Software was used tor Alpha spectrometry and 90Sr/90Y was measured on a Packard Tri Carb 3lOOTR LSC. This CRM is intended to be used in gross alpha beta counting instrumentation such as gas flow proportional counters and plastic scintillator detector chambers in accordance with lSO18589-6 Measurement of radioactivity in the environment — Soil Part 6: Measurement of gross alpha and gross beta activities and ultimately to be available tor commercial use.
Quartz, Calibration, Minerals, Geometry, Liquid scintillators, Purification, Dissolution
Wilsher, K., Harrison, J., van Wyngaardt, F., Lee, S., & Mokhber-Shahin, L. (2018). Preparation of certified reference materials for gross alpha beta measurement. Paper presented to the SPERA Conference 2018, "Bringing environmental radioactivity research to Western Australia, Perth, Western Australia, 6 - 9 November 2018, (pp. 52-53).