Abstract. In 2005, the Bhabha Atomic Research Centre (BARC), India, and the Comisión Nacional de Energía Atómica (CNEA), Argentina, each submitted one sample of known activity of ¹³⁴Cs to the International Reference System (SIR). This was followed in 2006 by the submission of an ampoule by the Institutul de Fizica si Inginerie Nucleara (IFIN-HH), Romania. The values of the activity submitted were between about 0.7 MBq and 1.3 MBq. The 2005 results replace earlier SIR measurements while the 2006 result of the IFIN-HH replaces a CCRI(II) comparison result of 1978. Consequently, there are now thirteen results in the BIPM.RI(II)-K1.Cs-134 comparison for which the key comparison reference value has been updated.

Also, in 2005, the APMP ran a key comparison for the activity of this radionuclide and the results are now linked to the BIPM.RI(II)-K1.Cs-134 comparison through the previous submissions of the pilot laboratory, NMIJ (Japan), and of the LNE-LNHB (France). This has enabled the VNIIM (Russian Federation) to update its result from the 1978 CCRI(II)-K2.Cs-134 comparison and the INER (Chinese Taipei) to be linked for the first time. In addition, the remaining eight eligible results from the 1978 CCRI(II) comparison are still linked provisionally to the SIR results.

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).