A liquid-scintillation-based primary standardization of 210Pb.

A new radioactivity solution standard of 210Pb has been developed and will be disseminated by the National Institute of Standards and Technology (NIST) as standard reference material (SRM) 4337. This new 210Pb solution standard is contained in a 5 mL flame-sealed borosilicate glass ampoule, consists of (5.133+/-0.002)g of a nominal 1mol L(-1) nitric acid solution, has a density of (1.028+/-0.002)g mL(-1) at 20 degrees C, has carrier ion concentrations of about 11 microg Pb2+ and 21 microg Bi3+ per gram of solution, and is certified to contain a massic activity (9.037+/-0.22)kBq g(-1) as of the reference time 1200 EST, 15 June 2006. All of the uncertainties cited above correspond to standard uncertainties multiplied by a coverage factor k=2. The standardization for the (210)Pb content of the solution was based on 4pialphabeta liquid scintillation (LS) measurements using CIEMAT/NIST (3)H-standard efficiency tracing (CNET). Confirmatory determinations were also performed by high-resolution HPGe gamma-ray spectrometry, by 2pialpha spectrometry with a Si surface barrier detector of separated 210Po, and by 4pibeta(LS)-gamma(NaI) anticoincidence counting.