Researchers uncover hidden pore network within nuclear fuel
New understanding of how nuclear fuel breaks down and changes in an operating nuclear reactor could help keep some reactors running longer, will inform the next generation of nuclear reactor fuel systems.
Researchers at MIT have conducted an extensive study on the inner structure of a specific type of metal fuel called U-10Zr, which is utilized in advanced nuclear reactors. This fuel was previously employed in experiments involving sodium-cooled fast reactors such as the Experimental Breeder Reactor-II (EBR-II) and the Fast Flux Testing Facility (FFTF).
The researchers utilized cutting-edge high-energy synchrotron X-ray computed tomography at Brookhaven National Laboratory to analyze the intricate pore networks and chemical changes that developed within the fuel following its use in the FFTF reactor.
The findings from this study have the potential to enhance the longevity of certain nuclear reactors, as well as inform the design of future nuclear reactor fuel systems. According to Ericmoore Jossou, a senior author of the study and Professor of Nuclear Science and Engineering at MIT, "This study helps us model the pore distribution in the fuel more accurately... It also helps us design for the safe operation of metallic fuels in reactors by giving us a better understanding of the role of pores and their importance."
The research team focused on samples from the FFTF reactor, which operated from 1982 to 1992. The samples were prepared by the Idaho National Laboratory and analyzed using the synchrotron X-ray tomography technique at Brookhaven. This technique allowed the researchers to reconstruct the internal pore networks in three dimensions, revealing how porosity, chemistry, and fuel-cladding interactions evolve across the fuel radius.
The researchers discovered that porosity increased gradually from the center of the fuel towards the edge, but the density of pores jumped by more than two orders of magnitude at the fuel's edge, near the cladding.
Additionally, the study mapped the microstructural changes alongside chemical variations within the fuel. The researchers found that the morphology and channels of pores were influenced by the local chemical environment, specifically whether it was uranium-rich or zirconium-rich. This finding had never been reported before and sheds light on the mechanisms that govern nuclear fuel behavior within reactors.
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