A simple computing program for application of the TDCR method to standardization of pure-beta emitters R. Broda a, *, P. Cassette b , K. Mal / etka a , K. Pochwalski a, 1 a RC POLATOM, 05-400 Otwock-S Â wierk, Poland b CEA/DAMRI/LPRI, BP 52, 91193 Gif sur Yvette Cedex, France Abstract The Triple to Double Coincidence Ratio (TDCR) method is an absolute LSC method for the activity determination of many radionuclides. The method is based on a statistical description of the phenomena in a triple photomultiplier LS counter. The TDCRB-1 program was developed to calculate the radioactive concentration of a solution and is based on the TDCR method data processing. The program, in FORTRAN language has a modular structure, which easy enables to understand its functioning. The outline of the theory, a structure and algorithm of the program, as well as an example of the output results, are presented. # 2000 Published by Elsevier Science Ltd. All rights reserved. 1. Introduction The Triple to Double Coincidence Ratio (TDCR) method is an absolute activity measurement method, used in Liquid Scintillation Counting (LSC) to stan- dardize a variety of dierent radionuclides. The method is based on a statistical description of the light emitted by the scintillator. The associated theory, pre- viously described in the literature, was used to develop a simple TDCRB-1 program to calculate the detection eciency and hence the source activity, of a triple photomultiplier LS counter for pure beta radio- nuclides. A set of counting points obtained by chan- ging the detector ®gure of merit is necessary. The paper describes models used to develop the program, including assumptions made in the counting eciency calculations and the program algorithm. Details of the program are described in the user manual. The structure of the program, written in FORTRAN language, is fully modular, to make it easy to read and modify. The form of the program is intended to enable each user of the TDCR method to have easy access to each sequence of the counting e- ciency determination procedure. The program is con- structed in the most simple way. The user can alter the program to include his own input ®le format. Subroutines can be independently modi®ed by the user, while retaining the structure of the de®ned input/ output parameters. Output data tables contain all measurement data and values used for activity determination for each counting point, which enables veri®cation of the appropriateness of the TDCR model and calculational accuracy. A schematic diagram of a set of counting points of each source is printed out, to facilitate a quick general view of measurement results. Each measurement anomaly is usually clearly visible in a plot of counting results versus TDCR parameter. Calculation results are saved on a computer disc. The TDCRB-1 program, examples of input data set Applied Radiation and Isotopes 52 (2000) 673±678 0969-8043/00/$ - see front matter # 2000 Published by Elsevier Science Ltd. All rights reserved. PII: S0969-8043(99)00229-8 www.elsevier.com/locate/apradiso * Corresponding author. Fax: +48-22-779-8880. 1 Retired from RC POLATOM.