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

Abstract

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 k 0 -standardised NAA (k 0 -NAA)it is possible to correct for this effect through the introduction of k 0 -fission factors. In this work the aim was to determine the feasibility of k 0 -NAA as a screening technique for accurate U and n(235U)/n(238U) isotopic ratio determination (we further refer to the technique as k 0 -UNAA) and where k 0 -UNAA could be positioned versus the other screening techniques. In k 0 -UNAA we use an adapted k 0 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 k 0 -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.