23rd International Conference on Radionuclide Metrology and its Applications - ICRM 2023

Primary standardization of Ac-225 at NRC

30 Mar 2023, 10:00

20m

Oral Liquid scintillation counting techniques Liquid scintillation counting techniques

Speaker

Raphael Galea (National Research Council of Canada)

Description

A solution of Ac-225 was standardized by NRC using the triple-to-double coincidence ratio (TDCR) method. The counting efficiencies were calculated assuming a counting efficiency of 100% for alpha decays and those calculated using the MICELLE2 monte carlo code for beta decays and was approximately 500% for the NRC TDCR system. The relative uncertainty for the activity concentration was determined to be 0.25% and this agreed with measurements performed using gamma spectroscopy and a predicted calibration factor for the Vinten Ion Chamber as calculated using an EGSnrc model, implementing radioactive decay. Finally, the half life of Ac-225 was determined from long term measurements using ion chambers and liquid scintillation counting. The NRC measured half life for Ac-225 was found to be 9.909(6) days and is consistent within an expanded uncertainty coverage of k=2 with the most recent [1,2] measurements of this decay parameter.

References:
[1] Pomme et. al., Appl.Radiat.Isot. 70, (2012) 2608-2614.
[2] Kossert et. Al, Appl.Radiat.Isot. 156 (2020) 109020.