Developing 226Ra and 227Ac age-dating techniques for nuclear forensics to gain insight from concordant and non-concordant radiochronometers

The model age or 'date of purification' of a nuclear material is an important nuclear forensic signature. In this study, chemical separation and MC-ICP-MS measurement techniques were developed for Ra-226 and Ac-227: grand-daughter nuclides in the U-238 and U-235 decay chains, respectively. The Th-230-U-234, Ra-226-U-238, Pa-231-U-235, and Ac-227-U-235 radiochronometers were used to calculate model ages for CRM-U100 standard reference material and two highly-enriched pieces of uranium metal from the International Technical Working Group Round Robin 3 Exercise. Results demonstrate the accuracy of the Ra-226-U-238 and Ac-227-U-235 chronometers and provide information about nuclide migration during uranium processing.