Elevated temperature nanoindentation and in-situ SEM mechanical testing of uranium fuels
September 29-October 4, 2019
Due to the Fukushima nuclear accident there has been a large effort by several countries to develop accident tolerant fuel forms for commercial light water reactors. A challenge with the current UO2 fuel is its low thermal conductivity which leads to higher center line temperatures in the fuel. New nuclear fuel forms are looking to increase the thermal conductivity and other thermophysical proprieties while also maintaining adequate mechanical properties and uranium loading. The elastic modulus, fracture toughness, and creep properties of the fuel are important for modeling the pellet clad mechanical interactions during operation of a nuclear reactor. During the operation of a nuclear reactor the cladding material creeps down and fuel pellet swells which leads to physical contact between the two. The pellet clad mechanical interactions can lead to potential cladding failures and release of radioactive material. The advanced fuel forms that are under consideration for replacing UO2 in commercial light water reactors is UN, U3Si2, composite UO2 and UO2 with additives. The composite UO2 is looking to increase the thermal conductivity with different additions and the UO2 with additives are intended to increase the grain size of the UO2. The increase in grain size can reduce the release of fission gas products into the plenum of the cladding rod improving the operational lifetime of the fuel. While there is a large amount of work on the thermal properties of these accident tolerant fuel forms the literature is quite sparse on the mechanical properties necessary for modeling such interactions as the pellet clad mechanical interactions.
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David Frazer, Joshua White, Tarik Saleh, and Peter Hosemann, "Elevated temperature nanoindentation and in-situ SEM mechanical testing of uranium fuels" in "Nanomechanical Testing in Materials Research and Development VII", Jon Molina-Aldareguia, IMDEA-Materials Institute, Spain Eds, ECI Symposium Series, (2019). https://dc.engconfintl.org/nanochemtest_vii/109