Investigation of Tin as a Fuel Additive to Control FCCI

One method to control fuel-cladding chemical interaction (FCCI) in metallic fuel is through the use of an additive that inhibits FCCI. A primary cause of FCCI is the lanthanide fission products moving to the fuel periphery and interacting with the cladding. This interaction will lead to wastage of the cladding and eventually to a cladding breach. Tin is being investigated as a potential additive to control FCCI by reacting with the fission product lanthanides. The current study is a scanning electron microscopy (SEM) characterization of a diffusion couple between U-10Zr-4.3Sn (wt%) and the 4 most abundant lanthanide fission products. As the lanthanides move into the fuel, they are interacting with and breaking down the Zr5Sn3 precipitates that formed during fresh fuel fabrication. This reaction produced Ln-Sn precipitates and δ phase (UZr2), which is conducive to normal fuel operation and increased burnups.