The paper begins with the reasons which led to the installation of the Système International de Référence (SIR) more than 30 years ago, describes its main features and presents briefly the way it works. Then more detail is given on the treatment of impurities and on the determination of the efficiency curve. The improvements, which have been made recently to update the SIR and make it more efficient, are also discussed. A brief survey of the status of the present SIR is then given before focusing on the new developments which are in progress to enlarge the scope of the SIR towards measurements of radiopharmaceuticals with short half-lives and of α- and β-particle emitters.
Liquid scintillation counting is a very powerful technique for the activity determination of a number of radionuclides. In radionuclide metrology, the TDCR method and the CIEMAT/ NIST efficiency tracing technique are widely used in many laboratories.Both methods require rather complex calculation techniques to derive the counting efficiency of the nuclide under study.This article explores the various sources of uncertainty that should be considered when applying these two techniques, and focuses on possible ways to evaluate them. Concrete examples are provided within the paper.
Some formulae used for evaluation of the uncertainties of the degree of equivalence between laboratories participating in an international comparison of activity measurement are presented. Two approaches are considered using two different estimators for the key comparison reference value: the arithmetic mean and the weighted mean. For each approach, four cases which can be encountered when dealing with comparison data are detailed. Finally, the effect of the uncertainties on the weights used in the second approach is also considered. This work has been developed for analysis of results of comparisons organized in the field of ionizing radiations, but the formulae are sufficiently general to allow their use for other comparisons. However, correlations between results have not been considered.
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