Abstract. An international comparison on radioactivity measurements of ¹³⁴Cs was carried out in 2005 between the NMIJ/AIST, LNE-LNHB, INER and the VNIIM, identified as the comparison APMP.RI(II)-K2.Cs-134. The original solution was prepared by the NMIJ and sent to the BIPM/SIR and eleven other institutes. The results were in agreement, using the half-life value of 753.1 days (2.062 y) recommended for this study. These results will be linked to the BIPM.RI(II)-K1.Cs-134 comparison in due course to provide degrees of equivalence for the APMP participants.

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