title: Activity determination of (59)Fe by 4π beta-gamma counting using liquid scintillation in the beta channel.
abstract: This paper reports on absolute activity measurements of iron-59 made at the National Metrology Institute of South Africa (NMISA) via 4π(LS)β-γ coincidence counting. The exercise formed part of an Asia Pacific Metrology Program (APMP) regional key comparison. Source data were analysed by the extrapolation technique for a number of gamma-ray window settings. In addition, a feasibility study was undertaken on a second technique; a non-extrapolation method based on a detection efficiency analysis. The reported activity concentration of the (59)Fe solution was determined with a relative uncertainty of 0.28% (k=1), the uncertainty being due mainly to the rate vs. efficiency fitting process. The result from the non-extrapolation method was lower than that given by extrapolation by 0.33%, within two standard deviations. Possible reasons for the small discrepancy are discussed.
authors.affiliation: Radioactivity Standards Laboratory, NMISA, 15 Lower Hope Road, Rosebank 7700, Cape Town, South Africa. Electronic address: mvrooy@nmisa.org.
authors.forename: M W
authors.initials: MW
authors.lastname: van Rooy
authors.affiliation: Radioactivity Standards Laboratory, NMISA, 15 Lower Hope Road, Rosebank 7700, Cape Town, South Africa.
authors.forename: M J
authors.initials: MJ
authors.lastname: van Staden
authors.affiliation: Radioactivity Standards Laboratory, NMISA, 15 Lower Hope Road, Rosebank 7700, Cape Town, South Africa.
authors.forename: J
authors.initials: J
authors.lastname: Lubbe
authors.affiliation: Radioactivity Standards Laboratory, NMISA, 15 Lower Hope Road, Rosebank 7700, Cape Town, South Africa.
authors.forename: B R S
authors.initials: BRS
authors.lastname: Simpson
keywords: Extrapolation technique; Iron-59; Liquid scintillation coincidence counting; Non-extrapolation method