A multi-technique approach to environmental particle analysis for nuclear safeguards

The International Atomic Energy Agency uses Environmental Sampling for Safeguards (ESS) to give additional assurance of the absence of undeclared nuclear materials and activities in States covered by comprehensive safeguards agreements. The analysis of individual micrometer-sized particles (so-called 'particle analysis') has been used since the beginning of the ESS programme because of its high inherent sensitivity (pg levels) and the wide range of isotopic information which can be obtained using mass spectrometric analysis techniques. This paper examines the application of a range of other analytical techniques to providing complementary information on individual particle morphology, structure and composition. The techniques applied are secondary electron microscopy (SEM) with energy-dispersive X-ray fluorescence microanalysis (EDX), transmission electron microscopy (TEM), micro-Raman spectroscopy, and ion-microprobe secondary ion mass spectrometry (IM-SIMS) used in full spectral mode. We start by applying these techniques to a range of U test compounds - uranium oxides, fluorides (UF4 and UO2F2) and di-uranate salts - to establish the fingerprint information available (including, in the case of UO2F2, a preliminary assessment of environmental stability). The diagnostic value of the multi-technique approach is then trialled by application to the differentiation of a set of 6 'blind' UO2 samples of identical isotopic composition. This was successfully achieved. Our overall conclusion is that application of the expanded range of particle analysis techniques has much to offer in the analysis of nuclear environmental samples, providing information on, for example, the process history of particles. (author)