Update of the ongoing comparison BIPM.RI(II)-K1.Co-60 including activity measurements of the radionuclide 60Co for the IFIN-HH (Romania), NIST (USA) and the BEV (Austria)

Since 2006, the Institutul de Fizica si Inginerie Nucleara 'Horia Hulubei' (Romania), and the National Institute of Standards and Technology (USA) and the Bundesamt fur Eich- und Vermessungswesen (Austria) have each submitted samples of known activity of 60Co to the International Reference System (SIR). The values of the activity submitted were between 180 kBq and 3.1 MBq. The key comparison results now include updated results for these three national metrology institutes with the identifier BIPM.RI(II)-K1.Co-60. 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 nineteen results as some very early results have now been excluded, identifier BIPM.RI(II)-K1.Co-60. (authors)