Twenty years ago South Africa's Radioactivity Standards Laboratory (now operated by the NMISA) was the first to measure the activity of55Fe by combining the triple-to-double coincidence ratio (TDCR) liquid scintillation method with theoretical efficiency formulae. The extracted activity was however found to be consistently low by about 6%. Due to improvements in both the counting system and analysis technique, it was decided to re-examine the method as applied at the NMISA. The latest results are presented and discussed, particularly with regard to a quantitative study into which vial type is better suited to obtaining accurate55Fe activity measurements. © 2009 Elsevier Ltd.
Simpson, B. R. S., van Wyngaardt, W. M., & Lubbe, J. (2010). Fe-55 activity measurements at the NMISA revisited. Applied Radiation and Isotopes, 68(7–8), 1529–1533. https://doi.org/10.1016/j.apradiso.2009.11.069