Update of the BIPM comparison BIPM.RI(II)-K1.Co-60 of activity measurements of the radionuclide ⁶⁰Co to include the 2020 result of the PTB (Germany), the 2020 result of the NIST (United States), the 2020 result of the SMU (Slovakia), the 2021 result of the BARC (India), the 2021 result of the LNE-LNHB (France), the 2021 result of the POLATOM (Poland), the 2021 result of the ENEA-INMRI (Italy), the 2021 result of the NPL (United Kingdom), the 2021 result of the LNMRI-IRD (Brazil), the…

Main text Since 1976, 30 laboratories have submitted 85 samples of 60 Co to the International Reference System (SIR) for activity comparison at the Bureau International des Poids et Mesures (BIPM), with comparison identifier BIPM.RI(II)- K1.Co-60. Recently, the PTB (Germany), the NIST (United States), the SMU (Slovakia), the BARC (India), the LNE-LNHB (France), the POLATOM (Poland), the ENEA-INMRI (Italy), the NPL (United Kingdom), the LNMRI-IRD (Brazil), the NMISA (South Africa) and the ANSTO (Australia) participated in the comparison and the key comparison reference value (KCRV) has been updated. The degrees of equivalence between each equivalent activity measured in the SIR and the updated KCRV have been calculated and the results are given in the form of a table. A graphical representation is also given. 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).