Activity determination of (59)Fe by 4π beta-gamma counting using liquid scintillation in the beta channel

M W van Rooy; M J van Staden; J Lubbe; B R S Simpson

doi:10.1016/j.apradiso.2015.11.054

Activity determination of (59)Fe by 4π beta-gamma counting using liquid scintillation in the beta channel

Appl Radiat Isot. 2016 Mar:109:276-280. doi: 10.1016/j.apradiso.2015.11.054. Epub 2015 Nov 22.

Authors

M W van Rooy¹, M J van Staden², J Lubbe², B R S Simpson²

Affiliations

¹ Radioactivity Standards Laboratory, NMISA, 15 Lower Hope Road, Rosebank 7700, Cape Town, South Africa. Electronic address: mvrooy@nmisa.org.
² Radioactivity Standards Laboratory, NMISA, 15 Lower Hope Road, Rosebank 7700, Cape Town, South Africa.

PMID: 26631452
DOI: 10.1016/j.apradiso.2015.11.054

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.

Keywords: Extrapolation technique; Iron-59; Liquid scintillation coincidence counting; Non-extrapolation method.