Final report of the SIM 60Co absorbed-dose-to-water comparison SIM.RI(I)-K4

Transfer chambers were used to compare the standards for 60Co absorbed dose to water maintained by seven laboratories. Six of the laboratories were members of the Sistema Interamericano de Metrologia (SIM) regional metrology organization while the seventh was the International Atomic Energy Agency (IAEA) laboratory in Vienna. The National Research Council (NRC) acted as the pilot laboratory for the comparison. Because of the participation of laboratories holding primary standards, the comparison results could be linked to the key comparison reference value maintained by the Bureau International des Poids et Mesures (BIPM). The results for all laboratories were within the expanded uncertainty (two standard deviations) of the reference value. The estimated relative standard uncertainty on the comparison between any pair of laboratories ranged from 0.6% to 1.4%. The largest discrepancy between any two laboratories was 1.3%. (authors)