Final report of the new BIPM comparison BIPM.RI(II)-K1.Ra-223 of activity measurements of the radionuclide ²²³Ra including the 2014 result of the NPL (United Kingdom), the 2014 result of the PTB (Germany) and the 2018 result of the LNE-LNHB (France)

Since 2014, 3 laboratories have submitted 3 samples of ²²³Ra 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.Ra-223. The NPL (United Kingdom), the PTB (Germany) and the LNE-LNHB (France) participated in the comparison and the key comparison reference value (KCRV) has been calculated for the first time. The degrees of equivalence between each equivalent activity measured in the SIR and the KCRV have been calculated and the results are given in the form of a table. A graphical presentation is also given. (authors)