Update of the BIPM comparison BIPM.RI(II)-K1.Am-241 of activity measurements of the radionuclide ²⁴¹Am to include the 2009 results of the POLATOM (Poland), MKEH (Hungary) and the 2011 results of the LNE-LNHB (France)

Since 2009, three national metrology institutes (NMI) have submitted three samples of known activity of ²⁴¹Am to the International Reference System (SIR) for activity comparison at the Bureau International des Poids et Mesures (BIPM), with comparison identifier BIPM.RI(II)-K1.Am-241. The values of the activity submitted were between about 3 MBq and 38 MBq. These three results replace their earlier results obtained in the linked CCRI(II)-K2.Am-241 in 2003. There are now five results in the BIPM.RI(II)-K1.Am-241 comparison, 16 results remaining from the CCRI(II)-K2.Am-241 comparison and two results in the COOMET.RI(II)-K2.Am-241 comparison. The degrees of equivalence between each equivalent activity measured in the SIR and the KCRV dating 2007 have been calculated and the results are given in the form of a table. A graphical presentation is also given.