title: Fe-55 activity measurements at the NMISA revisited.
abstract: Twenty years ago South Africa's Radioactivity Standards Laboratory (now operated by the NMISA) was the first to measure the activity of (55)Fe 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 accurate (55)Fe activity measurements.
authors.affiliation: National Metrology Institute of South Africa, Rosebank, Cape Town, South Africa. bsimpson@nmisa.org
authors.forename: B R S
authors.initials: BR
authors.lastname: Simpson
authors.forename: W M
authors.initials: WM
authors.lastname: van Wyngaardt
authors.forename: J
authors.initials: J
authors.lastname: Lubbe
mesh_terms: D006078:Government Programs; D007504:Iron Radioisotopes / Q000032:analysis*; D012588:Scintillation Counting / Q000379:methods; D013019:South Africa
chemical_list: D007504:Iron Radioisotopes