Traceability of measurements of radioactivity and of amount of substance

Comparability of measurement results in space and time are highly desirable to observe whether differences are real, whether concordance of results is real and whether trends over time of the quantity measured, are significant.The metrological way to achieve this, is to make results ‘traceable’ to a common ‘stated reference’ (definition in the Vocabulaire International de Métrologie — VIM). This ‘stated reference’ should be (the value of) the relevant SI unit wherever and whenever possible. The latest traceability concepts for results of measurements of radioactivity and amount of substance are presented and critically compared for their similarity. Transparent and simple pictures of traceability chains are given, respecting the VIM definition.