title: Standardization of radium-223 by liquid scintillation counting.
abstract: Liquid scintillation (LS) counting was undertaken as part of the primary standardization of (223)Ra. Radium-223 decays with a half life of 11.43 d through a chain of shorter-lived daughter radionuclides, resulting in five alpha decays and three beta decays. The CIEMAT/NIST method of tritium efficiency tracing was employed, with the beta efficiencies being calculated using the program CN2004, developed by the Physikalisch-Technische Bundesanstalt (PTB). The total calculated LS efficiency, considering all daughter radionuclides, was approximately 598%. Separate experiments were performed to rule out loss of the 3.96 s (219)Ra daughter from the cocktail and possible counting loss of the 1.78 ms (215)Po daughter due to LS counter dead-time. No loss was observed in either experiment. In the final experiment an expanded uncertainty (k=2) of 0.55% was achieved. Results were in excellent agreement with confirmatory measurements performed by 2pialpha proportional counting. However, results are not in agreement with methods based on gamma ray measurements.
authors.affiliation: Ionizing Radiation Division, Physics Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899-8462, USA. Jeffrey.cessna@nist.gov
authors.forename: J T
authors.initials: JT
authors.lastname: Cessna
authors.forename: B E
authors.initials: BE
authors.lastname: Zimmerman
mesh_terms: D006207:Half-Life; D011883:Radium / Q000592:standards*; D012588:Scintillation Counting / Q000379:methods; D014316:Tritium
chemical_list: D014316:Tritium; D011883:Radium