Study of a Monte Carlo rearrangement model for the activity determination of electron-capture nuclides by means of liquid scintillation counting.

A new Monte Carlo approach for the computation of the electron spectra of electron-capture nuclides is applied to obtain efficiencies in liquid scintillation counting for CIEMAT/NIST applications. The new method is applied to the radionuclides (109)Cd and (125)I by using a stochastic atomic rearrangement model, taking into account rearrangement processes including L-, M-, and N-subshells. The counting efficiencies were computed with the new code MICELLE which also comprises an approach for calculating the counting efficiency of a radionuclide in a gel phase sample. The calculated counting efficiencies are compared with experimental results.