BIPM comparison BIPM.RI(II)-K1.Th-228 of activity measurements of the radionuclide ²²⁸Th

Abstract

Since 1986, two national metrology institutes (NMI) have submitted two samples of known activity of 228Th 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.Th-228. The values of the activity submitted were about 300 kBq and 2 MBq. A key comparison reference value (KCRV) has been evaluated for the first time for 228Th. There is only one result remaining in the BIPM.RI(II)-K1.Th-228 comparison, the 1986 NIST result being outdated. 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. 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, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).