Standardization of 125I, 85Sr and 109Cd by CIEMAT/NIST method

We applied the CIEMAT/NIST method to the standardization of 125I, 85Sr and 108Cd in liquid scintillation counting. The effects of the chemical nature of the quencher on the standardization curves for these nuclides and the convenience of using CH3NO2 instead of CCl4 for quenching samples were studied. Monte Carlo simulations were used to compute energy spectrum of the electrons produced in the interaction of the KL-and KM-photons with the liquid scintillator. We demonstrated that photons with energies in the range between 20 and 40 keV create both Compton and photoelectric electrons. These Monte Carlo simulations also permitted us to determine accurately the X-ray contribution to the counting efficiency for 125I, 85Sr and 109Cd. (Author)