Standardization of 89Sr

Two methods were used for the standardization of the pure beta-emitter 89Sr solution received in the framework of the 2000 BIPM comparison of activity measurements. The first method was by scintillation counting using the triple to double coincidence ratio (TDCR) technique. The existing three detector-system was improved by the inclusion of a MAC-3 module produced by LNHB-Saclay. This module contains the circuits for the coincidence, dead time and gate functions. This was the first use of this equipment in an international comparison. The DETECSZ program (LNHB) was used to obtain the activity concentration, at the reference time, as 26.09±0.21 kBq g−1. The second method was the efficiency tracer technique, using a 60Co standard solution and a 4πβ–γ-coincidence system. The radioactivity concentration was calculated from a general extrapolation curve, by using data from several sources. The value was 26.58±0.28 kBq g−1 on the reference date 01.10.2000, 00h UTC. The two results are in agreement within the limits of their combined uncertainties.