A non-extrapolation method for ↑(55)Fe activity measurement based on liquid scintillation coincidence counting, is described. The figure-of-merit, P, describing the counting system is established by tracing internally with the #-emitting radionuclide ↑(54)Mn. from which the detection efficiency corresponding to ↑(55)Fe is calculated. The technique is similar in concept to the CIEMAT/NIST method for pure β-emitters. The advantage of replacing the external ↑(3)H standard with ↑(54)Mn is that it has very similar decay energetics to ↑(55)Fe. The practical application of the method is appraised particularly with regard to systematic effects on the extracted ↑(55)Fe activity for different ↑(54)Mn/↑(55)Fe activity ratios,#1998 Elsevier Science Ltd. All rights reserved
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