Oxygen isotopes can trace where uranium oxides were made — and where they’ve been

A new review of the nuclear fuel cycle has turned up key indicators that could signal nuclear material has fallen into the wrong hands. When uranium is being prepared for use in nuclear reactors, certain uranium oxide forms retain “water fingerprints” that could later point to fabrication, storage or transport routes. A paper in Applied Geochemistry sums up two decades of measurements and process chemistry that led to these findings.

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Why this matters: If illicitly trafficked nuclear material carries a measurable imprint of local water vapor or process water, investigators can narrow likely production regions and eliminate impossible origins faster — especially when that information is combined with trace-impurity and radiochronometry signatures.

What they did: Using oxygen isotope measurement methods, Lawrence Livermore National Laboratory partnered with Los Alamos National Laboratory and French researchers to investigate which uranium oxide forms best retain water fingerprints. 

• They walked step by step through the front end of the nuclear fuel cycle, looking for where oxygen can be exchanged during ore processing, calcination, deconversion, reduction and post-fabrication hydration. 
• Los Alamos scientists contributed expertise on particle isotope and element compositions, fuel cycle processing context and forensic implications.

How it works: Oxygen in uranium oxides can equilibrate with hydrogen dioxide or stable oxygen depending on process conditions (notably humidity, temperature and cooling rate). 

• Hydrous alteration minerals such as metaschoepite can lock in local water vapor after exposure.
• Knowing what water touched the material, and when, can become a forensic clue if samples are handled and stored correctly. 

Funding: National Nuclear Security Administration’s Office of Nuclear Smuggling Detection and Deterrence. 

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