Age Dating of Individual Micrometer-Sized Uranium Particles by Secondary Ion Mass Spectrometry: An Additional Fingerprint for Nuclear Safeguards Purposes

A direct and simultaneous analysis of the age and isotopic composition of nuclear material at the particle scale is described in this study. By comparison with other conventional techniques such as inductively-coupled plasma mass spectrometry or thermal-ionization mass spectrometry, secondary ion mass spectrometry enables one to determine the ages of individual particles in a mixture of nuclear materials. Having access to the purification date can give precious information on the history of a nuclear facility or nuclear material for safeguarding purposes. The high sensitivity of this technique combined with its imaging capabilities enables one to detect and to sort out all particles according to their isotopic composition in one analysis. The succession of two microbeam analyses on an individual particle allows the determination of the precise 235U abundance and the model age. The methodology was successfully applied to a mixture of uranium particles coming from certified reference material with a 235U abundance ranging from 10% to 97%: the accuracy on the 235U abundance is greater than 0.5% and the accuracies on the 235U abundance and the model age are better than 0.5% and 3%, respectively.