Optimized production of dual-isotope sources for gamma detector calibration

Radioisotopes ¹⁵²Eu and ¹⁵⁴Eu are suitable options for calibrating HPGe detectors due to their long half-lives, high spectral purity, and distinct gamma lines. In this study, the production of these radioisotopes through direct irradiation of natural europium in the Tehran Research Reactor was investigated. For the optimal design of the irradiation process, the MCNPX 2.6.0 simulation code was used and then the practical production of the radioactive source was carried out under specified conditions. The sample was irradiated at a location with a neutron flux of 1.31 n/(cm²s) for 2 days, and after a 21-day cooling period, gamma spectroscopy was performed using an HPGe detector. The experimental results showed that the obtained activities were in good agreement with the simulation predictions. Additionally, a comparison of the detector efficiency using the produced source and a standard reference source confirmed the proper performance of the produced source. This study shows that the combination of simulation and experimental methods can provide an efficient and reliable approach for producing radioactive standard sources in research reactor environments. It can also be concluded that, given the natural abundance and lower cost of natural europium compared to the enriched isotopes 151Eu and 153Eu, its use as the primary target is a cost-effective and practical solution for the production of standard calibration sources.