Environmental Monitoring for Safeguards Using $k_{0}$ -standardized Neutron Activation Analysis

Multi-elemental analysis of samples containing uranium by Instrumental Neutron Activation Analysis (INAA) has been generally known as a problematic task due to the numerous radioisotopes produced from the uranium fission when the sample is irradiated with thermal neutrons. In k₀ -standardized NAA (k₀-NAA), it is possible to correct for this effect through the introduction of k₀ -fission factors. In this work, the aim was to determine the feasibility of k₀-NAA as a screening technique for accurate U and n(²³⁵ U)/n(²³⁸ U) isotopic ratio determination (we further refer to the technique as k₀-UNAA) and where k₀ -UNAA could be positioned versus the other screening techniques. In k₀-UNAA, we use an adapted k₀ formalism to determine the n(²³⁵ U)/n(²³⁸ U)-ratio. Several swipe samples spiked with different U isotopic ratios were analyzed and demonstrate the feasibility of k₀-UNAA as a accurate and reliable screening method for the quantification of environmental samples up to several tens of ng. At these levels the uranium concentration can be quantified with a reasonable uncertainty and reliable n(²³⁵ U)/n(²³⁸ U) isotopic ratio analysis could also be performed.