Application of the CIEMAT–NIST method to plastic scintillation microspheres

An adaptation of the MICELLE2 code was used to apply the CIEMAT–NIST tracing method to the activity calculation for radioactive solutions of pure beta emitters of different energies using plastic scintillation microspheres (PSm) and ³H as a tracing radionuclide. Particle quenching, very important in measurements with PSm, was computed with PENELOPE using geometries formed by a heterogeneous mixture of polystyrene microspheres and water. The results obtained with PENELOPE were adapted to be included in MICELLE2, which is capable of including the energy losses due to particle quenching in the computation of the detection efficiency. The activity calculation of ⁶³Ni, ¹⁴C, ³⁶Cl and ⁹⁰Sr/⁹⁰Y solutions was performed with deviations of 8.8%, 1.9%, 1.4% and 2.1%, respectively. Of the different parameters evaluated, those with the greatest impact on the activity calculation are, in order of importance, the energy of the radionuclide, the degree of quenching of the sample and the packing fraction of the geometry used in the computation. - Highlights: • CN method has been used to the measurement of β emitters with PSm. • MICELLE2 has been adapted to simulate particle quenching energy losses in PSm. Activity is dependent on chemical quenching and on geometry used for simulation. • Deviations are below 10% for ⁶³Ni and below 3% for ¹⁴C, ³⁶Cl and ⁹⁰Sr/⁹⁰Y