Correlative morphological, elemental and chemical
analyses of actinide-bearing particles for nuclear safeguards
and nuclear forensics

The analytical chemistry unit of the Division of Military Applications(DAM) of the French Atomic Energy Commission (CEA) has capabilities for characterizing micrometric particles (so-called particle analysis). These capacities are regularly implemented in support of the IAEA’s safeguards. Indeed, the unit is a member of the Network of Analytical Laboratories (NWAL) which carry out bulk and particle analyses of environmental samples (i.e. cotton wipers used to collect dust particles into nuclear facilities by wiping smooth surfaces). Moreover, these capacities are also used in the framework of nuclear forensics, as a complement to “bulk” methods, which involve a dissolution step, lengthy radiochemical treatment and measurement by radiometric (α-spectrometry) and/or mass spectrometry (ICPMS, TIMS) techniques. Implementation of more direct particle analysis, without or with very short sample preparation, allow reporting results within a shorter analytical delay (24 hours to a few days) than bulk methods and possibly identifying and characterizing components of a mixture. Several micro-analytical techniques are used for both programs at CEA/DAM. A Large Geometry – Secondary Ion Mass Spectrometer (LG-SIMS) is operational since 2022 for measurement of the isotope composition of individual micro-particles made of actinides (uranium and/or plutonium). The isotope composition is complemented by a morphological description of the particles (size, geometry, surface texture, etc.) thanks to electronic imaging performed with a Scanning Electron Microscope (SEM), by the identification of the other major or minor elements which compose the micro-particles thanks to an Energy Dispersive X-ray Spectrometer (EDS) attached to the SEM, and by the determination of the chemical phase(s) (molecular composition, crystalline structure) of the actinide compounds by means of a micro-Raman spectrometer [1-3]. Furthermore, morphological, elemental and chemical phase analyses can be carried out exactly at the same micrometric spot, i.e. for the same micro-particle, thanks to a coupling device which allows performing the Raman analysis within the SEM measurement chamber (so-called in-SEM Raman spectrometry) [4,5]. The aim of this publication is to describe the SEM/EDS – Raman spectrometer coupling and its application to the correlative morphological, elemental and chemical analyses of actinide-bearing micro-particles. Advantages and limitations of the coupling are discussed and two relevant examples of application to nuclear safeguards and nuclear forensics are presented.