Since 1976, seven national metrology institutes (NMIs) and an international organization have submitted 20 samples of known activity of ⁷⁵Se 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.Se-75. The activities ranged from about 1.4 MBq to 15 MBq. The results of a CCRI(II) comparison held in 1992 for this radionuclide, with comparison identifier CCRI(II)-K2.Se-75, are linked to the BIPM comparison for 18 participants through individual measurements of the comparison ampoules in the SIR. This has enabled six NMIs to update their earlier SIR results and another 11 NMIs and the BIPM to have degrees of equivalence in the key comparison database (KCDB). The degrees of equivalence between each equivalent activity measured in the SIR and the key comparison reference value (KCRV) have been calculated and the results are given in the form of a matrix for 18 NMIs and the BIPM. A graphical presentation is also given.

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 Mutual Recognition Arrangement (MRA).