Adhesion strength of sputter deposited diffusion barrier layer coatings for the use in U–Mo nuclear fuels

Advanced designs for high-density U–Mo/Al nuclear fuel feature an interfacial barrier layer between the U–Mo fuel bulk and the Al cladding, which is intended to avoid the formation of an irradiation induced diffusion layer (IDL). Sputter deposition was suggested as a method to apply such interfacial barriers to the U–Mo/Al fuel system. We investigated the adhesion strength of sputter deposited Ti, Zr, Zry-4, Nb and Ta barrier layers of 15–20 μm thickness in the U–Mo/Al system by pull-off tests. The adhesion strength is a measure for the robustness of a diffusion barrier layer against delaminating due to inner stresses. We found, that the adhesion strength of sputter deposited diffusion barrier layers is at least similar or even better compared to both the adhesion strength of barrier layers produced by the INL co-rolling process and the fuel-to-cladding adhesion strength achieved by the AREVA-CERCA C2TWP process.