International comparison of activity measurements of a solution of ⁵¹Cr

Main text A bilateral comparison between LNE-LNHB, France and the RC POLATOM, Poland on activity measurements of the 51Cr solution was organized in 2022 as the EURAMET project No 1554 and registered as EURAMET.RI(II)-K2.Cr-51 key comparison. In both laboratories, primary activity measurements techniques based on 4π(LS)-γ coincidence and anti-coincidence counting methods were used. LNE-LNHB also performed indicative measurements in a large-well NaI(Tl) detector using the 4πγ method. The final result of the comparison in RC POLATOM was the weighted mean of the results of the 4π(LS)-γ coincidence method and the 4π(LS)-γ anti-coincidence method, and in the LNE-LNHB - the value obtained by the 4π(LS)-γ anti-coincidence method. The power-moderated mean of the final results values was calculated. An additional ampoule containing the same 51 Cr solution was sent to the BIPM in order to link the results achieved in the bilateral comparison to the BIPM SIR reference system. 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).