Activity determination of (227)AC and Ra-223 by means of liquid scintillation counting and determination of nuclear decay data

作者：Kossert Karsten^*; Bokeloh Karen; Dersch Rainer; Naehle Ole

来源：Applied Radiation and Isotopes, 2015, 95: 143-152.

DOI：10.1016/j.apradiso.2014.10.005

• (227)AC
• Ra-223
• Liquid scintillation counting
• TDCR
• Ra-223 half-life
• Photon emission probabilities

The activity concentrations of solutions containing (222)AC and Ra-223 in equilibrium with their progenies, respectively, were measured by means of liquid scintillation counting. The counting efficiencies were determined with the aid of a free parameter model. The corresponding calculations comprise the computation of several alpha, beta and beta/gamma branches. For short-lived progenies like Po-215 the counting efficiency depends on the counter dead time. Measurements were made in custom-built triple-to-double coincidence ratio (TDCR) systems and various dead-time adjustments were used. In addition, two commercial counters were used to apply the CIEMAT/NIST efficiency tracing technique using H-3 as a tracer.
For the (227)AC solution, the overall relative standard uncertainty of the activity concentration was found to be 0.93%. The dominant uncertainty components are assigned to the efficiency computation of the low-energy beta transitions of (227)AC. We have identified a need for improved (222)AC decay data to achieve a significant reduction in the overall uncertainty.
In the case of Ra-223, the activity concentrations were determined with relative standard uncertainties below 0.3%. Hence, PTB is prepared to provide calibration services for Ra-223, which is an isotope of increasing interest in nuclear medicine.
The TDCR measurements were also used to determine the half-life of Ra-223. The decay was followed for about 58 days and a half-life T-1/2=11.4362(50) d was obtained.

• 出版日期2015-1