Microscopic studies of spherical particles for nuclear safeguards

A combination of micro-analytical techniques was used for the characterization of spherical particles in the size range 9–12 μm as a part of nuclear safeguards verification activities pursuant to the Treaty on the Non-Proliferation of Nuclear Weapons (NPT). The particles were removed from cotton swipe samples taken in a nuclear facility under safeguards and examined first by scanning electron microscopy combined with energy-dispersive X-ray spectrometry (SEM–EDX). Particles of interest were then relocated under an optical microscope and manipulated. One such particle was subjected to destructive analysis by secondary ion mass spectrometry (SIMS) in order to determine if uranium was present in the core of the particle. A second particle was examined using focused ion beam (FIB) etching to allow an examination of the interior by SEM–EDX. The particle manipulation and relocation techniques presented here allow the sequential examination of a single particle of interest by a combination of analytical techniques, thus yielding surface morphological, elemental, isotopic and depth-profiling information. The objective of these investigations is to provide assurance of the absence of clandestine or undeclared nuclear activities in States coming under comprehensive safeguards obligations.