Exercise Celestial Skónis: Part 1 – History, purpose, design and results of traditional forensic examinations of the 6th Collaborative materials exercise of the nuclear forensics International Technical Working Group

The Nuclear Forensics International Technical Working Group conducted its sixth and largest Collaborative Materials Exercise, Celestial Skónis, in which laboratories from 20 countries (one virtual participant) and the European Commission, working with 15 law enforcement agencies, analyzed a set of samples containing special nuclear material as part of an elaborate mock nuclear forensics investigation. The nuclear materials used during the exercise included (1) depleted uranium and (2) stable cerium metal ingots contaminated on their surfaces with trace amounts of depleted uranium- and weapons grade plutonium-oxy-fluoride powders. This exercise also included traditional evidence (e.g., cut surfaces of pipes, toolmarks on plastic bags, and patent and latent fingerprints) comingled/contaminated with radioactivity. Participating laboratories processed traditional forensic evidence contaminated with radioactivity and analyzed nuclear materials in support of the mock investigation over a two-month period. These results were used to evaluate the “State of Practice” and identify promising “Emerging Technologies” in nuclear forensic science. This work is presented in two parts. Part 1 summarizes the history and purpose of these exercises, describes the design of the 6th and latest in this series, presents results of traditional forensic examinations on evidence contaminated with radioactivity, and summarizes the traditional and nuclear forensic evidence used to answer investigatory questions posed during the exercise. Part 2 summarizes results of nuclear forensic analyses that were conducted on the nuclear materials, giving special focus to the challenges of interpreting U and Pu isotopic results and the utility of those results for connecting people, places, things and events.