Electroplating of zirconium on uranium-molybdenum alloy fuel for high performance research reactors

The Fuel Fabrication Capability (FFC) within the US High Performance Research Reactor Conversion Program, which is funded by the United States Department of Energy through NNSA NA-23 (Office of Material Management and Minimization), commissioned an investigation to determine the conceptual feasibility of using electroplating techniques to apply a coating of zirconium (Zr) onto depleted uranium/molybdenum alloy (U-10Mo). A new electroplating process for plating zirconium metal onto the U-10Mo alloy plate fuel has been developed. The plating is conducted in a proprietary molten salt mixture that does not react with the U-10Mo and produces a 25μm thick Zr layer. This approach provides an alternative method to the existing process baseline approach of roll-bonding Zr foil onto the DU-10Mo fuel foil during the fabrication of fuel elements for high performance research reactors. In order to achieve good quality plating, both the U-10Mo surface preparation and the method of residual salt removal are important. The best method for surface prep found so far, an acid wash in 8 molar nitric acid followed by an ethanol rinse, produces better results than electropolishing. The removal of the residual salt appears to have an impact on the final plating quality as well. Final washes in hot water resulted in significant amounts of plating defects that were eliminated when the salt was removed with ethanol. (author)