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Ra-224 activity, half-life, and 241 keV gamma ray absolute emission intensity: a NIST-NPL bilateral comparison



Denis E. Bergeron, Sean Collins, Leticia Pibida, Jeffrey T. Cessna, Ryan P. Fitzgerald, Brian E. Zimmerman, Peter Ivanov, John Keightley, Elisa Napoli


The national metrology institutes for the United Kingdom and the United States have compared activity standards for 224Ra, an -particle emitter of interest as the basis for therapeutic radiopharmaceuticals. Solutions of 224RaCl2 were assayed by absolute methods, including digital coincidence counting and triple-to-double coincidence ratio liquid scintillation counting. Ionization chamber and high-purity germanium (HPGe) -ray spectrometry calibrations were compared; further, a solution was shipped between laboratories for a direct comparison by HPGe spectrometry. New determinations of the absolute emission intensity for the 241 keV  ray and of the 224Ra half-life are presented and discussed in the context of previous measurements and evaluations.
Applied Radiation and Isotopes


Decay constant, emission probability, coincidence counting, TDCR, ionization chamber, gamma-ray spectrometry, activity standard, comparison, alpha therapy


Bergeron, D. , Collins, S. , Pibida, L. , Cessna, J. , Fitzgerald, R. , Zimmerman, B. , Ivanov, P. , Keightley, J. and Napoli, E. (2020), Ra-224 activity, half-life, and 241 keV gamma ray absolute emission intensity: a NIST-NPL bilateral comparison, Applied Radiation and Isotopes, [online], (Accessed May 21, 2024)


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Created December 31, 2020, Updated March 1, 2021