Idaho National Laboratory researchers have recently demonstrated a new sample preparation technique that makes it easier to examine irradiated fuel at the nanoscale. This accomplishment revealed material behavior that suggests increased stability of a new type of reactor fuel. Further study and improvement in nuclear fuel performance are now much more attainable, said Dennis Keiser, a researcher in INL’s Nuclear Fuels and Materials Division.

INL’s Advanced Test Reactor has several isolated experimental chambers where new materials can be intensely irradiated under controlled conditions. Once a new fuel or material has been irradiated, researchers examine it to see how it performed. Cracks, bubbles, or other irregularities warrant closer scrutiny.

Once INL researchers were able to obtain tiny, intact pieces from the fuel plate, they had to make the samples thin enough to analyze with a transmission electron microscope (TEM). The new sample preparation technique — called “Focused Ion Beam In-Situ Lift-Out” — mills the material with an ion beam to yield sections that are just tens of nanometers thick, which can reveal new features under a TEM.

Researchers are still analyzing the data they’re collecting from this approach, but initial findings are promising. For example, the fuel they examined contained an organized lattice of gas bubbles that suggests enhanced irradiation stability.

The approach, INL researchers predict, could inspire a host of new discoveries related to nuclear fuel research, design, and development.

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