Cross-validation of standardisation techniques at ANSTO using cobalt-60 and learnings from the presence and identification of non-gamma-ray emitting impurities.

To fulfil the technical requirements for accreditation to ISO/IEC 17025, the end-to-end validation of all processes associated with standardising 60Co, including gravimetric source dispensing, primary standardisation by the 4π(LS)ß-γ coincidence and live-timed anti-coincidence extrapolation techniques, and impurity determination were performed and documented. Pure-beta-emitting impurities in a 60Co stock solution were identified. The impact of such impurities on measurement by liquid scintillation counting and comparison in the ESIR are discussed. A fresh 60Co source was produced, standardised, and compared using the SIR.