Standardization of Tc-99 by three liquid scintillation counting methods

•Activity concentration of Tc-99 solution measured using three LSC methods.•Methods used are TDCR, CNET and 4π(LS)β–γ coincidence tracing.•Beta spectral shape confirmed by agreement between three methods.

The NMISA participated in the international key comparison of the pure beta-emitter Technetium-99, CCRI(II)-K2.Tc-99. The comparison solution was standardized using three methods, namely the TDCR efficiency calculation method, the CIEMAT/NIST efficiency tracing method and the 4π(LS)β–γ coincidence tracing method with Co-60 as tracer. Excellent agreement between results obtained with the three methods confirmed the applicability of the beta spectral shape given by the latest (2011) DDEP evaluation of Tc-99 decay data, rather than the earlier (2004) evaluation.