A review of the triple-to-double coincidence ratio (TDCR) method for standardizing radionuclides.

This paper gives a review of the development of the triple-to-double coincidence ratio (TDCR) method for standardizing pure beta- and pure electron capture (EC)-radionuclides. The initial idea of Schwerdtel and practical realization and elaboration of the TDCR method by Pochwalski is presented. The main aspects and theoretical principle of the method are summarized and progress on the development of the theoretical model is presented. The details of the activity determination of pure beta- and pure EC radionuclides are discussed, along with specific details in the application of the method in each case. The enhanced TDCR method based on the MAC3 electronic system developed in France is also discussed. Different applications of the TDCR method in metrology laboratories around the world are also pointed out.