Abstract. Since 2004, the Institute for Reference Materials and Measurements (IRMM, Geel, Belgium), Physikalisch-Technische Bundesanstalt (PTB, Germany), Országos Mérésügyi Hivatal (OMH, Hungary), Laboratoire national de métrologie et d'essais–Laboratoire national Henri Becquerel (LNE–LNHB, France) and the National Metrology Institute of Japan (NMIJ) each submitted one sample of known activity of ¹³⁴Cs to the International Reference System (SIR). The OMH, PTB and LNE–LNHB results replace their 1992, 1994 and 1998 SIR measurements respectively while the IRMM and NMIJ submissions are their first measurements in the SIR, replacing the 1978 CCRI(II) comparison results. The values of the activity submitted were between about 0.6 MBq and 5.4 MBq. The key comparison results have been added to the matrix of degrees of equivalence that now contains 12 results, identifier BIPM.RI(II)-K1.Cs-134, to which the remaining ten eligible results from the CCRI(II)-K2.Cs-134 held in 1978 are linked.

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).