Investigation into the standardization of 99Tc

The standardization of 99Tc by several primary methods was investigated. This was performed to support a new 99Tc transfer standard that has been developed and will be disseminated by the National Institute of Standards and Technology (NIST) as Standard Reference Material SRM 4288B. The standardization for the 99Tc content of the solution was based on 4πβ liquid scintillation (LS) measurements with 3H-standard efficiency tracing (CIEMAT/NIST method). Confirmatory determinations were performed by 4πβ(LS)-γ(NaI) live-timed anti-coincidence (LTAC) counting and an LS-based 4πβ triple-to-double coincidence ratio (TDCR) method.