Standardization of the EC nuclides55Fe and 65Zn with theCIEMAT/NIST LSC tracer method

A study is made of the standardization of 55Fe and 65Zn under different experimental and theoretical conditions. Sample composition, tracer nuclide, ionization quench approximations, kB values and approximations for the average L Auger electron energy, were varied to find out the optimum conditions. A standardization of 55Fe and 65Zn is possible with a relative standard uncertainty of about 0.5% using 54Mn as a tracer. However, the experiments with 3H as a tracer show that the EC decay model and the LSC theory which are included in the CIEMAT/NIST programs are not fully satisfactory for these two EC radionuclides.