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Image of microscopic uranium particle sample
Evan Groopman, a research physicist, prepares a microscopic uranium particle sample to be measured in the NAUTILUS instrument in the Accelerator Mass Spectrometry Laboratory at the U.S. Naval Research Laboratory in Washington, D.C. (U.S. Navy photo by Nicholas E. M. Pasquini)

Researchers with the U.S. Naval Research Laboratory (NRL) designed and built an instrument called NAUTILUS to provide new measurement capabilities to measure nuclear, cosmo/geo-chemical, and electronic materials.

At the end of last year, NRL participated in an international round-robin exercise, called Nuclear Signatures Inter-laboratory Measurement Evaluation Program (NUSIMEP-9), sponsored by the European Commission (Nuclear Safety and Security Division) to measure microscopic particulate samples with “unknown” uranium isotope ratios.

“NRL recently received the final report from the international round-robin exercise and found that the Laboratory performed quite well, correctly identifying all of the “unknown” isotopic compositions,” said David Willingham, a research chemist and head of the Accelerator Mass Spectrometry Section. “In this case, NRL used a globally unique mass spectrometer called NAUTILUS to perform these measurements, as part of the Accelerator Mass Spectrometry Section’s participation in the NUSIMEP-9 sample analysis exercise.”

The NUSIMEP-9 test samples were prepared to mimic environmental sampling/nuclear Safeguards missions, such as those performed by the International Atomic Energy Agency (IAEA). The exercise was conducted for the IAEA’s Network of Analytical Laboratories (NWAL), of which NRL is not a member; however, NRL does collaborate with the laboratories to develop better uranium-bearing particle analyses. The IAEA is responsible for deterring the proliferation of nuclear weapons by detecting early the misuse of nuclear material or technology, and by providing credible assurances that states are honoring their safeguards obligations. The analysis of nuclear material samples and environmental samples taken by IAEA inspectors is an essential component of this undertaking.

Twenty-two other laboratories were involved, many of which perform these types of measurements as their core mission (e.g., IAEA) with their instruments dedicated solely for these types of measurements. A key element of the safeguards system is the physical inspection of nuclear facilities by IAEA inspectors. States declare in considerable technical detail the types and quantities of nuclear material they possess. Among other verification measures, IAEA inspectors may take nuclear material samples from various points of the nuclear fuel cycle and collect environmental samples by swiping surfaces at various locations during the conduct of a verification activity.

These samples, which may be in solid, liquid, or gaseous form, are then subject to sophisticated analysis by IAEA scientists. The scientists focus on the isotopic make-up of uranium and plutonium contained in the samples, unaware of the country from which they were obtained. The analytical results provide a powerful tool for supporting conclusions as to the correctness and completeness of states' nuclear material declarations and help to inform the IAEA’s evaluation of whether a state is complying with its safeguards obligations.

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