Fuel-Cladding Compatibility of AFC2-A Transmutation Alloys: FY2007 Report

As part of the Global Nuclear Energy Partnership/Advance Fuel Cycle Initiative (GNEP/AFCI) program, the compatibility of Type HT-9 stainless steel (SS) and U-Pu-Zr-based alloys with additions of Am and Np has been tested by studying a solid-solid diffusion couple between Type HT-9 SS and the as-cast fuel alloy 60U-20Pu-3Am-2Np-15Zr. In addition, the influence of processing carry-over of fission product lanthanide content into the fresh fabricated fuel has been studied through investigation of a diffusion couple between HT-9 SS and a U-20Pu-3Am-2Np-1.5Ln-15Zr as-cast fuel alloy (Ln = 6La-25Ce-16Pr-53Nd). These couples were annealed at the approximate fuel-cladding temperature of 550 C for a period of 120 hours. Analysis was performed using a scanning electron microscope equipped with energy-dispersive and wavelength-dispersive spectrometers (SEM/EDS/WDS) to evaluate any developed diffusion structures. At 550 C, no uniform diffusion layers were observed. Since no uniform phase layers that could lead to reduced mechanical properties are found at the fuel-cladding interface, the steel should maintain its original mechanical properties.