New measurements on neutron-induced activation towards an innovative approach for controlled interferences in neutron activation analysis

Neutron Activation Analysis (NAA) is a widely utilized technique for precise elemental quantification across diverse fields such as geology, materials science, and archaeology. Despite its high sensitivity and specificity, NAA is often hindered by interferences arising from competing nuclear reactions in mixed thermal/fast neutron fields. Thermal neutrons predominantly produce radioactive nuclei through neutron capture (n,γ) reactions, while fast neutrons can trigger alternative reactions such as (n,p) on another nuclei possibly present in the material under analysis leading to the production of the same radio-isotope as the main capture reaction and so complicating spectral analysis and increasing uncertainty of the method. This study supports the proposal of an innovative approach to accurately quantify interferences in NAA based on a system allowing irradiations in controlled neutron fields with variable thermal/fast neutron ratios. As calculations are intensively used to optimize the system based on this new approach, the capabilities of simulation tools must be tested against new data to ensure accuracy of the proposed method. A deuterium-tritium (d-T) neutron generator-based facility was used to irradiate metallic samples under tailored conditions. Key reactions investigated were 27 Al(n,γ) and 28 Si(n,p), both of which produce the 28 Al radio-isotope. Post-irradiation spectra were analyzed using a HPGe detector to determine neutron-induced radio-isotope activity in samples. Monte Carlo simulations and activation calculations accurately reproducing the irradiation conditions were performed and the results are compared to the experimental values. This work highlights the potential of controlled neutron fields to resolve longstanding challenges in NAA, paving the way to a versatile and scalable solution for interference quantification and a more accurate material elemental analysis. • Neutron Activation Analysis accuracy is affected by interferences. • Accurate determination of fast neutrons contribution help controlling the effect of interferences. • New neutron-induced activation measurements with both thermal and fast neutrons have highlighted and quantified interferences. • Comparison with simulations have checked the accuracy of the codes in modelling neutron-induced reactions of interest. • An innovative approach allowing to control the interferences in NAA has been proposed.