Simple counting technique for measuring mixtures of two pure beta-emitting radionuclides

Abstract

A simple counting technique to measure mixtures of two pure beta-emitting radionuclides is described. The method is based on elements of two liquid scintillation techniques that are widely used to measure single-radionuclide solutions, namely the triple-to-double coincidence ratio (TDCR) efficiency calculation technique and the CIEMAT/NIST efficiency tracing method. Double- and triple-coincidence count rates, together with the figure-of-merit P determined from an external tracer, are used to extract the component activities of a source. A simulation was used to gauge the effect of counting statistics on the method's ability to extract a mixture composition under normal counting conditions and to validate derived uncertainty formulas based on counting statistics. The method is demonstrated experimentally for various mixture combinations of C-14 and Ni-63. It is shown that the accuracy of the technique can be enhanced by improving the determination of the figure-of-merit.