The enhanced triple to double coincidence ratio (ETDCR) method for standardization of radionuclides by liquid scintillation counting

This work is a continuation of previous papers on the TDCR method, and is based on the counting efficiency variation by photomultiplier tube (PMT) defocalisation in the triple scintillation detector. The enhanced triple to double coincidence ratio (ETDCR) method, a new version of the TDCR method, uses a modified counting system, having five, instead of two, coincident counting channels, and takes into consideration the diversity of optical efficiencies of the three PMTs of the detector. It is no longer extrapolative and is used for direct calculation of the source activities even for low energy emitters. The counting results of a set of sources, having equal chemical composition and figure of merit, composed of four radionuclides, 14C, 63Ni, 3H and 55Fe, are presented and discussed. Their identical composition makes it possible to compare the counting parameters and to correct the activity computing method. Application of different statistical distributions to processing the counting results are discussed. (orig.)