Primary standardization of 224Ra activity by liquid scintillation counting.

A standard for activity of 224Ra in secular equilibrium with its progeny has been developed, based on triple-to-double coincidence ratio (TDCR) liquid scintillation (LS) counting. The standard was confirmed by efficiency tracing and 4παβ(LS)-γ(NaI(Tl)) anticoincidence counting, as well as by 4πγ ionization chamber and NaI(Tl) measurements. Secondary standard ionization chambers were calibrated with an expanded uncertainty of 0.62% (k = 2). Calibration settings were also determined for a 5 mL flame-sealed ampoule on several commercial reentrant ionization chambers (dose calibrators). • A solution of 224Ra was standardized for activity by triple-to-double coincidence ratio (TDCR) liquid scintillation counting. • Efficiency tracing and anticoincidence provided confirmatory measurements. • Radionuclide calibrator settings determined with typical expanded (k = 2) uncertainties < 1%. [ABSTRACT FROM AUTHOR]