PNNL

Imagine a suspicious package being intercepted at a border crossing. Inside is a small amount of uranium. Investigators need to know what it is, where it came from, if it is dangerous, and whether it is connected to a larger security threat. In a real incident, scientists and law enforcement officials would have little time to begin piecing together those answers.

For the Nuclear Forensics International Technical Working Group (ITWG), that challenge is the focus of the Collaborative Materials Exercise (CMX), a recurring exercise designed to assess and advance the international community’s ability to analyze found materials outside of regulatory control (MORC) during a nuclear security investigation.

Pacific Northwest National Laboratory (PNNL) has played a long-standing role in that effort, helping lead the international exercise series alongside the Atomic Weapons Establishment (AWE) Nuclear Security Technologies in the United Kingdom since the first CMX (previously called Round Robin Exercises) in 1998. Together, they are working to advance the science behind nuclear forensics investigations.

“These real-world exercises are invaluable learning opportunities for the community, allowing participants to test and demonstrate their concepts of operations for managing a nuclear forensic investigation, from processing evidence at a radiological crime scene, to examining radiologically contaminated evidence and characterizing special nuclear materials that together support nuclear forensic conclusions,” said Pennsylvania State University professor and PNNL joint appointee Jon Schwantes. “At the completion of these exercises, participants share best practices and identify emerging technologies that ultimately improve how the world responds to a nuclear security event involving MORC.”

A long-standing partnership

Established in 1996, the ITWG brings together nuclear forensic practitioners from more than 55 countries and multinational organizations. The group includes scientists, law enforcement officials, regulators, and policymakers, and it conducted its first CMX in 1999.

The CMX series of exercises is organized and facilitated by the Exercise Task Group of the ITWG, which has been chaired or cochaired by a PNNL-affiliated scientist since the first CMX. Schwantes has served as the United States cochair for the ETG since 2010, alongside fellow ETG Cochair Olivia Marsden, from AWE. Together, the ETG cochairs take turns facilitating CMXs, with Schwantes acting as the exercise facilitator for the most recently completed CMX. In addition to this leadership role, forensics experts at PNNL supported the CMX with materials analysis and data interpretation.

In May 2026, the ITWG completed its eighth CMX, Exercise Red Tutu (CMX-8), the largest exercise in the series to date. This exercise brought together 27 laboratories from 26 countries and the European Commission, along with 17 law enforcement agencies.

PNNL played a central role in CMX-8, providing the first detailed analyses of the special nuclear materials used in the exercise, leading the development of the exercise scenario, coordinating exercise play, and summarizing the results.

“Organizing these exercises takes a herculean effort by dozens of folks across the US government and beyond,” said Schwantes. “Scientists at PNNL provided invaluable support during the planning stages of the exercise by providing the first detailed analyses of the materials. This information was then used by scientists from the US, Canada, Germany, and the UK to develop the exercise objectives and scenario.”

Staff at PNNL also helped to coordinate, manage, and organize participant results. Each participant submitted preliminary reports at 24 hours and 1 week after the start of their exercise, followed by a final report at the close of the two-month exercise.

“Analyzing the data coming in from the labs—from the 24‑hour report through the two‑month report—was very interesting,” said PNNL chemist Ana Arteaga. “You can really see the progression of the data, showing how each lab applied its own unique approach to solving the same problem.”

Turning science into investigative clues

The CMX scenarios use well-characterized “real-world” nuclear materials alongside conventional forensic evidence to challenge participants to answer questions that matter to the investigation. The goal is not simply to identify a material but to extract information from it and put that information into an investigative context.

CMX-8 was built around a fictional nuclear security investigation that involved the discovery of four uranium-bearing materials representing MORC and nuclear forensic evidence at two fictional crime scenes. Participants could also participate in a separate radiological crime scene module, where they examined conventional forensic evidence, including toolmarks (spent shell casings), indented writing, torn edges (plastic trash bags and tape), trace evidence (chinchilla hair), fibers (twine from a rope), patent and latent fingerprints, and DNA.

Together, those different types of evidence reflect the way a real investigation can unfold. Scientists may need to determine what a specific material is and whether it presents an immediate health risk. Investigators may then need to understand where the material came from, how it was processed, whether it is connected to other seizures, or what those findings could mean for a broader security investigation.

“The CMX exercises have really elevated the complexity and opportunities for countries to showcase their best, while remaining inclusive of a range of capabilities among participants,” said Erin Morrison, a chemist at PNNL who manages the project executing PNNL CMX scope. “The main goal of CMX is to assess the state of the international nuclear forensic community and provide opportunities to advance analysis and detection capabilities in support of nuclear nonproliferation.”

What comes next

The exercise formally concluded with an exercise review meeting in Bucharest, Romania, in May of 2026. For participants, however, that meeting marks the beginning of the next phase of turning observations and data from CMX-8 into lessons that can strengthen nuclear forensic practice worldwide.

“The closing of the exercise in Romania was a valuable learning experience for everyone involved,” said Arteaga. “It offered the international nuclear forensics community the opportunity to present their results and learn from one another in a supportive, collaborative setting. Some of the most meaningful conversations focused on what went well—and, importantly, what didn’t.”

This effort is funded by the National Nuclear Security Administration, through its Nuclear Smuggling Detection and Deterrence program, which funds PNNL to develop and administer the CMX exercises, reflecting the role nuclear forensics play in the broader United States nuclear security mission.

For PNNL, CMX-8 is also another chapter in a nearly three-decade partnership with the international nuclear forensics community. The next exercise, CMX-9, is already on the horizon with a projected fall 2028 start date.

As ITWG prepares for the next challenge, PNNL’s continued leadership will help ensure that scientists and investigators are prepared not only to analyze the evidence when a nuclear security incident occurs but also to turn that evidence into answers.