Effective Determination of the Long-lived Nuclide 41Ca in Nuclear Reactor Bioshield Concretes: Comparison of Liquid Scintillation Counting and Accelerator Mass Spectrometry

Warwick, P.E., Croudace, I.W. and Hillegonds, D.J. (2009) Effective Determination of the Long-lived Nuclide 41Ca in Nuclear Reactor Bioshield Concretes: Comparison of Liquid Scintillation Counting and Accelerator Mass Spectrometry. Analytical Chemistry, 81 (5), 1901-1906. (doi:10.1021/ac802225a).

Abstract

The routine application of liquid scintillation counting to 41Ca determination has been hindered by the absence of traceable calibration standards of known 41Ca activity concentrations. The introduction of the new IRMM 41Ca mass-spectrometric standards with sufficiently high 41Ca activities for radiometric detection has partly overcome this although accurate measurement of stable Ca concentrations coupled with precise half-life data are still required to correct the certified 41Ca:40Ca ratios to 41Ca activity concentrations. In this study, 41Ca efficiency versus quench curves have been produced using the IRMM standard, and their accuracy validated by comparison with theoretical calculations of 41Ca efficiencies. Further verification of the technique was achieved through the analysis of 41Ca in a reactor bioshield core that had been previously investigated for other radionuclide variations. Calcium-41 activity concentrations of up to 25 Bq/g were detected. Accelerator mass spectrometry (AMS) measurements of the same suite of samples showed a very good agreement, providing validation of the procedure. Calcium-41 activity concentrations declined exponentially with distance from the core of the nuclear reactor and correlated well with the predicted neutron flux.

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Contributors

Author: P.E. Warwick

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