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In 2014, PTB and the company Eckert & Ziegler organized a national comparison exercise to determine the activity of a (90)Y solution. One aim of the comparison was to assess the measurement capability of hospitals and medical practices in Germany. P6-type vials were filled with aliquots of a radioactive (90)Y solution and then sent to 19 participants who were asked to measure the activity in the ampoules as well as in their own standard geometry using syringes. Most of the submitted results have a deviation of less than ±10% from the PTB reference activity when measured in the P6-type vials. The spread is somewhat larger when measured in a syringe geometry. The comparison revealed that some participants have difficulties in applying decay corrections and only a few participants were capable of estimating realistic measurement uncertainties., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

The activity concentrations of solutions containing 227 Ac and 223 Ra 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 215 Po 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 3 H 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 227 Ac decay data to achieve a significant reduction in the overall uncertainty. In the case of 223 Ra, the activity concentrations were determined with relative standard uncertainties below 0.3%. Hence, PTB is prepared to provide calibration services for 223 Ra, which is an isotope of increasing interest in nuclear medicine. The TDCR measurements were also used to determine the half-life of 223 Ra. The decay was followed for about 58 days and a half-life T 1/2 =11.4362(50)d was obtained., (Copyright © 2014 Elsevier Ltd. All rights reserved.)