Comparison of tritiated-water standards by liquid scintillation for calibration of a new Standard Reference Material®

A new National Institute of Standards and Technology (NIST) tritiated-water (3H-labeled oxidane) standard was prepared and calibrated. It is the 17th in a series of linked standards since 1954 and will be disseminated as Standard Reference Material® SRM 4927G, having a massic activity of 544.2 kBq g−1, with an expanded (k=2) relative standard uncertainty of 0.96%, at a Reference Time of 1200 EST, 1 May 2015. The calibration is based on relative liquid scintillation (LS) measurements using quench-varied efficiency tracing with two previous 1999 issues, viz., SRM 4927F and 4926E. Measurement comparisons were also made with respect to a 1994 tritiated-water French national standard and to a tritiated-water solution measured by 19 laboratories as part of an international measurement comparison organized by the Bureau International des Poids et Mesures (BIPM) in 2009. Confirmatory measurements for the massic activity of both SRM 4927F and 4927G by a triple-to-double coincidence ratio (TDCR) technique were also made.