U.S. Department of Energy

Pacific Northwest National Laboratory

Groundbreaking research approach enhances discovery

Until now, nuclear fuel studies could be conducted only in highly restricted facilities with costly, restricted technology by specially trained personnel. These limiting factors vanished when NPSI's Richard Clark and his team made it possible to study important degradation processes in irradiated uranium oxide (UO2) in essentially any facility by any researcher with any relevant instrumentation.

The Epsilon project team developed a safer and less costly sample preparation method.

The team's work on NPSI's Epsilon project has cut the nuclear fuel ATM-109 down to a size that is safer, less complicated to handle, and more versatile in its uses than ever before. This world-leading innovation could save millions of dollars while affording more researchers access to this area of study--now research institutions without Category-level facilities can study used nuclear fuel for the first time. Clark and his team have demonstrated a method of generating micron-size samples of radioactive material that makes it safer and cheaper to use in studies and offers collaborative opportunities never before possible.

The project has revived PNNL research active in the 1990s and extended it to create a new paradigm in nuclear materials characterization and handling. Their strategy of conducting materials science at the micron scale will allow more researchers to study nuclear fuel degradation in non-radiological facilities with a broader range of instruments.

Clark's team has been studying the formation of epsilon phase particles in used nuclear fuel since 2015. Epsilon phase particles are five metal phases resulting from the irradiation of UO2 fission products. Their formation can lead to point and line defects in the fuel, and eventually problems such as cracking. Researchers believe much of the same chemistry that causes epsilon phase particles may also be at work in corroding the first layer of containment surrounding nuclear fuel (called cladding). As dry storage of used nuclear fuel becomes more prevalent, cladding integrity becomes more important to confirm and preserve. The team's breakthrough sample preparation of ATM-109 smooths the path toward safe storage of used fuel and other useful applications.

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