Standardisation of the 129I, 151Sm and 166mHo activity concentration using the CIEMAT/NIST efficiency tracing method

The 129I, 151Sm and 166mHo standardisations using the CIEMAT/NIST efficiency tracing method, that have been carried out in the frame of the European Metrology Research Program project “Metrology for Radioactive Waste Management” are described. The radionuclide beta counting efficiencies were calculated using two computer codes CN2005 and MICELLE2. The sensitivity analysis of the code input parameters (ionization quenching factor, beta shape factor) on the calculated efficiencies was performed, and the results are discussed. The combined relative standard uncertainty of the standardisations of the 129I, 151Sm and 166mHo solutions were 0.4%, 0.5% and 0.4%, respectively. The stated precision obtained using the CIEMAT/NIST method is better than that previously reported in the literature obtained by the TDCR (129I), the 4πγ-NaI (166mHo) counting or the CIEMAT/NIST method (151Sm).