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In the summer of 2017, the Système International de Référence Transfer Instrument (SIRTI) of the Bureau International des Poids et Mesures (BIPM) was hosted by the National Research Council of Canada (NRC) in Ottawa, Canada. This SIRTI visit was unique in many aspects. It was the first visit of the SIRTI to Canada. NRC was the first National Metrological Institute (NMI) to perform comparisons of four isotopes (⁹⁹ᵐTc, ¹⁸F, ⁶⁴Cu and ¹¹C) during a single two-week period. Finally, this was the first official measurement of ¹¹C in the SIRTI. The NRC had performed a primary standardization of ¹¹C in February of 2017 and calibrated its Secondary Standard Ionizing Radiation Chamber System (SSIRCS) in preparation for the SIRTI comparison. Two primary Liquid Scintillation methods (CIEMAT/NIST and TDCR) were employed and the results agreed. The stock material was received from a local cyclotron in the form of a¹¹C-labelled sodium acetate (NaC₂H₃O₂). Three ampoules were prepared for the purposes of comparison; one concentrated from the bulk material and two derived from a single dilution. Some inconsistency was evident due to a weighing problem for one of the ampoules containing the diluted solution, whose measurements were excluded from the analysis. The other two ampoules’ results were consistent within their respective uncertainties. The SIRTI was very stable and the final BIPM report will detail the stability checks, performance and behaviour of the SIRTI during its measurement campaign in Canada. There is still no Key Comparison Reference Value (KCRV) for ¹¹C as NRC is the first participant. However, during a test of the SIRTI at NPL in 2014, an equivalent SIRTI activity was measured as 9.87(5) kBq which was consistent with MonteCarlo predictions for ¹¹C in the SIRTI of 9.867(15) kBq. The NRC SIRTI equivalent activity for ¹¹C agrees within uncertainty with these results. This offers encouragement to other NMIs to request a¹¹C comparison given the consistency of experimental results from NRC and test results from the National Physical Laboratory, UK (NPL) and the BIPM. Finally a half-life measurement was determined from the NRC measurement of multiple half-lives of a ¹¹C ampoule and was found to be 20.332(40)min. From the SIRTI measurements at NRC, the half-life was derived as 20.328(13) min. This is smaller but consistent with the DDEP recommended value of 20.361(23)min., International Conference on Radionuclide Metrology, May 27-31, 2019, Salamanca, Spain

An informal bilateral comparison of ¹⁴C liquid scintillation (LS) counting at the National Research Council of Canada (NRC) and the National Institute of Standards and Technology (NIST) has been completed. Two solutions, one containing ¹⁴C-labeled sodium benzoate and one containing ¹⁴C-labeled n-hexadecane, were measured at both laboratories. Despite observed LS cocktail instabilities, the two laboratories achieved accord in their standardizations of both solutions. At the conclusion of the comparison, the beta spectrum used for efficiency calculations was identified as inadequate and the data were reanalyzed with different inputs, improving accord., 20th International Conference on Radionuclide Metrology and its Applications, June 8-11, 2015, Vienna, Austria