Abstract The JRC applied six measurement techniques to standardise the activity of an 241 Am solution in frame 2003 key comparison CCRI(II)-K2.Am-241. methods used were alpha-particle counting at a defined small solid angle, high-efficiency particle and photon with windowless 4π CsI(Tl) sandwich spectrometer, alpha pressurised proportional counter, alpha-gamma coincidence sum counter NaI(Tl) we...