In 1998, five national metrology institutes (NMI), an international laboratory and the Bureau International des Poids et Mesures (BIPM) took part in a comparison of activity measurements of ²³⁷Np as part of the EUROMET project No 416 comparison identifier EUROMET.RI(II)-K2.Np-237. The nominal activity per mass of the ²³⁷Np solution distributed was 150 kBq g^-1. The three ampoules received by the BIPM for this comparison were also measured in the International Reference System (SIR) for activity comparison at the BIPM (identifier BIPM.RI(II)-K1.Np-237). Two other participants to the EUROMET comparison also submitted ampoules of the same ²³⁷Np solution to the SIR. These SIR measurements enable the EUROMET comparison to be linked to the BIPM.RI(II)-K1.Np-237. The degrees of equivalence between each laboratory and the key comparison reference value (KCRV) have been calculated and the results are given in the form of a graph and matrix for the three SIR participants and four other NMIs from the EUROMET comparison.

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 the CCRI Section II, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).