Interdiffusion behavior in UPuZr fuel versus stainless steel couples

Fuel-Cladding Interaction Between U-Pu-Zr Fuel and Fe

“…Out-of-pile annealing tests on diffusion couples have been conducted to investigate FCCI behavior between U-Zr and U-Pu-Zr fuel alloys and Fe, Fe-12Cr, and HT-9 cladding. [4][5][6][7][8][9][10][11] The most inclusive study of quaternary U-Pu-Zr-Fe system at 973 K (700°C) has been conducted using thermal analysis and energy-dispersive spectroscopy (EDS) in scanning electron microscope (SEM). [9] However, there are issues associated with the characterization of Pu phases using EDS such as unavailability of U and Pu standards for appropriate EDS calibration, spatial resolution, magnification-dependent sensitivity of the technique, and overlaps of U and Pu EDS peaks, all of which restrict accurate quantitative chemical analysis of Pu-based phases in SEM.…”

Metallic fuels for advanced reactors

“…These alloys are completely compatible with the sodium used as a liquid metal bond and reactor coolant, exhibiting no reaction [4]. Fuel-cladding chemical interaction between these Zr-based fuel alloys and the stainless steel cladding has been observed to occur at a relatively predictable rate [48]. For austenitic stainless steels, FCCI is described by the correlation [49]:…”

Fuels for sodium-cooled fast reactors: US perspective

“…In addition to fuel swelling and fission gas release, such phenomena included fuel constituent redistribution (interdiffusion of U, Pu, and Zr within the fuel to create Zr-depleted radial zones with attendant lower, local solidus temperatures), and fuel/cladding interdiffusion enhanced by lanthanide fission products present in increasing amounts with higher burnup, which could lead to formation of lower-melting-temperature composition regions in the fuel, effectively thinning of the cladding. These phenomena were studied in some detail [33][34][35][36][37][38][39].…”

“…The significant result was the understanding that formation of such zones is due to phase equilibria effects established in the temperature gradient across the radius of the fuel -meaning that the low-solidus-temperature Zr-depleted would form in a region of the fuel where, under normal conditions, the temperature would not exceed the local solidus temperature [34,[36][37][38]. Studies of U-PuZr and cladding interdiffusion found that interdiffusion zones would melt under simulated transient conditions at temperatures as low as 675°C, leading to cladding penetration and breach [33,39]. The beneficial effects of Zr at the fuel/cladding interface were exhibited in various ways (e.g., [40]).…”