An international comparison of the pure β-emitter ⁹⁰Y has been performed recently, with comparison identifier, CCRI(II)-K2.Y-90. A total of eight laboratories performed assays for radioactivity content on aliquots of a common master solution of ⁹⁰Y prepared by the National Institute of Standards and Technology (NIST). The average activity concentration of the solution measured by the laboratories was 8664 kBq g^-1; u = 4 kBq g^-1 at a reference time of 0 h UTC 1 November 2003. Using this value as the key comparison reference value, degrees of equivalence and their associated uncertainties have been calculated and the results are given in the form of a matrix for the eight participants. 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).