Evaluation of the Ductility of Cold Sprayed Copper Coatings for the Long-term Disposal of Nuclear Fuel

An internationally recognized best practice for the permanent disposal of nuclear fuel is to use deep geological repositories where the used nuclear fuel is stored in specially designed carbon steel canisters. Copper, as an excellent corrosion-resistant material, has been applied to a carbon steel canister by the means of cold spray (CS) coating in the Canadian design of the used fuel container. In order to meet design requirements, we experimentally studied a number of factors that can impact the ductility of the CS copper coatings. Although not apparent from literature, the current investigation shows that significant changes in ductility in the range of approximately 8-26% can be obtained when the feedstock powder properties (e.g., chemical composition and particle size) are changed while keeping the spray and heat treatment conditions constant. Testing results show that the nitrogen-cold sprayed copper coatings’ ductility decreases with increasing hardness in a linear relationship, and can be improved with annealing temperature rising from 300 °C to 600 °C. The effects of substrate geometry and the variability of the process are also discussed.