Characterization of phases formed between U-Pu-Mo fuels and Fe-12Cr cladding

Exposure to high temperatures and irradiation can lead to interaction between fuel and cladding constituents, inter-diffusion, and formation of brittle or low-melting phases. Therefore, understanding of fuel-cladding interaction (FCCI) is critical for evaluation of fuel performance in a reactor environment. In this contribution, phases formed between U-22Pu-4Mo and U-25Pu-15Mo (in wt%) fuel alloys and Fe-12Cr cladding were characterized using scanning and transmission electron microscopy (SEM/TEM) techniques. Phases formed within FCCI layers in both alloys were identified by implementing selective area diffraction pattern analysis as Cr0.3Mo0.7 (Im-3m), Fe2U (Fd-3m), UCrFe (Fd-3m), and Fe2Pu (Fd-3m). Phases formed at the end of the FCCI layer in the U-22Pu-4Mo alloy included UCrFe (Fd-3m), Fe2U (Fd-3m), and Cr2FeO4 (Fd-3m) while in the U-25Pu-15Mo alloy the phases were consistent with Cr0.49Fe0.51 (P42/mnm), Cr0.8Fe0.2 (Im-3m), and UCrFe (Fd-3m).