Microstructural analysis of as-processed U–10 wt.%Mo monolithic fuel plate in AA6061 matrix with Zr diffusion barrier

For higher U-loading in low-enriched U–10 wt.%Mo fuels, monolithic fuel plate clad in AA6061 is being developed as a part of Reduced Enrichment for Research and Test Reactor (RERTR) program. This paper reports the first characterization results from a monolithic U–10 wt.%Mo fuel plate with a Zr diffusion barrier that was fabricated as part of a plate fabrication campaign for irradiation testing in the Advanced Test Reactor (ATR). Both scanning and transmission electron microscopy (SEM and TEM) were employed for analysis. At the interface between the Zr barrier and U–10 wt.%Mo, going from Zr to U(Mo), UZr2, γ-UZr, Zr solid-solution and Mo2Zr phases were observed. The interface between AA6061 cladding and Zr barrier plate consisted of four layers, going from Al to Zr, (Al, Si)2Zr, (Al, Si)Zr3 (Al, Si)3Zr, and AlSi4Zr5. Irradiation behavior of these intermetallic phases is discussed based on their constituents. Characterization of as-fabricated phase constituents and microstructure would help understand the irradiation behavior of these fuel plates, interpret post-irradiation examination, and optimize the processing parameters of monolithic fuel system.