Revision of the NIST Standard for 223Ra: New Measurements and Review of 2008 Data

Published

July 1, 2015

Author(s)

Denis E. Bergeron, Jeffrey T. Cessna, Leticia S. Pibida

Abstract

After discovering a discrepancy in the transfer standard currently being disseminated by the National Institute of Standards and Technology (NIST), we have performed a new primary standardization of the alpha-emitter 223Ra using Live-timed Anticoincidence Counting (LTAC) and the Triple-to-Double Coincidence Ratio Method (TDCR). Additional confirmatory measurements were made with the CIEMAT-NIST efficiency tracing (CNET) of liquid scintillation counting,integral-ray counting using a NaI(Tl) well counter, and several High Purity Germanium (HPGe) detectors in an attempt to understand the origin of the discrepancy and to provide a correction. The results indicate that a -9.5 % difference exists between activity values obtained using the former transfer standard relative to the new primary standardization. During one of the experiments, a 2 % difference in activity was observed between dilutions of the 223Ra master solution prepared using the composition used in the original standardization and those prepared using 1 mol∙L-1 HCl. This effect appeared to be dependent on the number of dilutions or the total dilution factor to the master solution, but the magnitude was not reproducible. A new calibration factor (“K-value”) has been determined for the NIST Secondary Standard Ionization Chamber (IC “A”), thereby correcting the discrepancy between the primary and secondary standards.

Citation

Journal of Research (NIST JRES) -

NIST Pub Series

Journal of Research (NIST JRES)

Pub Type

NIST Pubs

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Keywords

radium-223, standards, liquid scintillation spectrometry, anticoincidence counting, ionization chambers, traceability

Citation

Bergeron, D. , Cessna, J. and Pibida, L. (2015), Revision of the NIST Standard for 223Ra: New Measurements and Review of 2008 Data, Journal of Research (NIST JRES), National Institute of Standards and Technology, Gaithersburg, MD, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=917481 (Accessed May 28, 2023)