Participation of Czech laboratories in isotopic, structural, and elemental characterization of uranium nuclear forensic samples within the 7th collaborative material exercise

This paper describes the nuclear-forensic characterization of materials provided by the Nuclear Forensic International Technical Working Group within the 7th Collaborative Material Exercise. The characterized materials were two powdered uranium material samples labelled ES-1 and ES-3 and two uranium metal samples labelled ES-2 and ES-4. A combination of several analytical techniques was used by a group of Czech laboratories to the identification of chemical compounds and the determination of the uranium isotopic and elemental composition of all four samples. Those results allowed for an unambiguous conclusion that ES-1 was depleted uranium trioxide, ES-2 was depleted uranium-vanadium alloy, ES-3 was depleted uranium nitrate, and ES-4 was depleted uranium metal. A further conclusion was that ES-2 cannot originate from the same source as the other three samples and that ES-1, ES-3, and ES-4 had a common source material. The highlights of this work were in obtaining the isotopic composition of uranium, including minor isotopes, in the early (24-hour) phase of the exercise using the Secondary Ion Mass Spectrometry in a single-particle measurement mode and in the application of the Neutron Activation Analysis with uranium separation prior to irradiation for the elemental screening of the uranium samples.