Abstract. Since 2004, both the National Metrology Institute of Japan (NMIJ) and the Institute for Reference Materials and Measurements (Geel) have submitted samples of known activity of ⁶⁰Co to the International Reference System (SIR). The values of the activity submitted were about 1.4 MBq. The key comparison results now include an IRMM result for the first time and have been updated for Japan. The key comparison reference value has been re-evaluated following the recommendations of the CCRI(II) and the matrix of degrees of equivalence in the key comparison database now contains 22 results, identifier BIPM.RI(II)-K1.Co-60.

Main text. 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 kcdb.bipm.org/.

The final report has been peer-reviewed and approved for publication by Section II of the Consultative Committee for Ionizing Radiation (CCRI(II)), according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).