Environmental monitoring for safeguards using k0-standardised 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-standardised 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(²³⁵U)/n(²³⁸U) 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(²³⁵U)/n(²³⁸U)-ratio. Several swipe samples spiked with different isotopic ratio´s U were analysed 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(²³⁵U)/n(²³⁸U) isotopic ratio analysis could also be performed.