Results of the CCRI(II)-S16.Lu-177 International Supplementary Comparison of the Activity Measurements of a Solution of ¹⁷⁷Lu

Main text A supplementary international comparison of the measurement of the activity per unit mass of a solution of 177 Lu was organized in 2024. The solution was distributed by IRA. Seven laboratories participated and reported their results from many variants of coincidence methods and liquid-scintillation counting methods. Various averages of the reported results and the associated uncertainties are obtained. This report describes the procedures of this comparison, the measurements by the participants, supplementary comparison reference value, and the degrees of equivalence of the results. Comparative analyses are also provided by technique of measurement. To reach the main text of this paper, click on Final Report . Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/ . The final report has been peer-reviewed and approved for publication by the CCRI, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).