Journal of Radioanalytical and Nuclear Chemistry

, Volume 322, Issue 2, pp 263–269 | Cite as

Simple methods for calculating activity of a parent-progeny system

  • Cong WeiEmail author
  • Kelly Garnick
  • Thomas Scott
  • Anthony Wetherby


Based on the original work of Rutherford (Radio-activity, 1905) and Bateman (Proc Camb Philos Soc 15:423–427, 1910), the authors designed two schemes consisting of explicit equations as simple methods for accurately obtaining activity of 90Sr and 90Y before they reach secular equilibrium. Application of the methods to the 90Sr/90Y system where 90Sr and 90Y are not in equilibrium will substantially reduce the time needed for determining activity of 90Sr because neither sequential measurements of 90Sr or 90Y (up to about 2 weeks) nor waiting for 90Sr and 90Y to reach equilibrium (more than 3 weeks) will be needed. We also implemented the explicit equations for decay/ingrowth correction of progeny’s activity and applied them to the 95Zr/95Nb system. Using the equations, the authors corrected activity concentrations of 95Nb to a designated reference time from the activity concentrations measured from samples at different times, for instance, 2, 8, 15, and 29 days after a reference time. During those measurement times, 95Nb and 95Zr were not in equilibrium. The corrected 95Nb activity concentrations were within an accuracy of − 10%.


89,90Sr/9095Zr/95Nb Ingrowth correction Rapid analysis Nuclear incident Secular equilibrium 



The authors wish to thank Brian Baker and Patrick Regan of FDA/ORA/WEAC for their support of this work. The authors also wish to thank the FRMAC organizers especially Phil Torretto for the inter-laboratory comparison study opportunity. In addition, the authors wish to acknowledge Larry Jassin at EZA for providing us with blank air filter samples before the exercise.

Supplementary material

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Supplementary material 1 (XLSX 48 kb)
10967_2019_6724_MOESM2_ESM.docx (29 kb)
Supplementary material 2 (DOCX 20 kb)
10967_2019_6724_MOESM3_ESM.pdf (1 mb)
Supplementary material 3 (PDF 1026 kb)


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Copyright information

© This is a U.S. Government work and not under copyright protection in the US; foreign copyright protection may apply  2019

Authors and Affiliations

  • Cong Wei
    • 1
    Email author
  • Kelly Garnick
    • 1
  • Thomas Scott
    • 1
  • Anthony Wetherby
    • 1
  1. 1.Winchester Engineering and Analytical Center (WEAC), Office of Regulatory Affairs (ORA)The US Food and Drug AdministrationWinchesterUSA

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