title: Standardisation of223Ra by liquid scintillation counting techniques and comparison with secondary measurements.
abstract: An aqueous solution of223Ra chloride in equilibrium with its decay progeny was standardised by liquid scintillation counting techniques. Since secular equilibrium with the decay progeny of223Ra had been established by the time of measurement, the apparent detection efficiency of223Ra was approximately 6 and was determined by both the CIEMAT/NIST efficiency tracing technique and the 4π(LS)-γ digital coincidence counting techniques. The results obtained were compared with γ-spectrometry and ionisation chamber measurements. Whilst the γ-spectrometry measurements were in agreement (albeit exhibiting a large spread (18%) in the individual activity estimations using the main γ-emissions), a significant discrepancy of the order of 9% was identified between the liquid scintillation counting results and those obtained using published calibration factors for a variety of radionuclide calibrators.
authors.affiliation: National Physical Laboratory, Hampton Road, Teddington, Middlesex TW11 OLW, UK. Electronic address: john.keightley@npl.co.uk.
authors.forename: John
authors.initials: J
authors.lastname: Keightley
authors.affiliation: National Physical Laboratory, Hampton Road, Teddington, Middlesex TW11 OLW, UK.
authors.forename: Andy
authors.initials: A
authors.lastname: Pearce
authors.affiliation: National Physical Laboratory, Hampton Road, Teddington, Middlesex TW11 OLW, UK.
authors.forename: Andrew
authors.initials: A
authors.lastname: Fenwick
authors.affiliation: National Physical Laboratory, Hampton Road, Teddington, Middlesex TW11 OLW, UK.
authors.forename: Sean
authors.initials: S
authors.lastname: Collins
authors.affiliation: National Physical Laboratory, Hampton Road, Teddington, Middlesex TW11 OLW, UK.
authors.forename: Kelley
authors.initials: K
authors.lastname: Ferreira
authors.affiliation: National Physical Laboratory, Hampton Road, Teddington, Middlesex TW11 OLW, UK.
authors.forename: Lena
authors.initials: L
authors.lastname: Johansson
keywords: Calibration figure; DCC; Dial setting; Digital coincidence counting; Liquid scintillation counting; Primary standardisation; Ra-223; Radioactivity