Electrodeposited Overlays for Improved Durability of Nuclear Reactors

Processes are sought to improve reliability and extend the life of next generation molten salt reactor systems, by developing scalable processes to apply bimetallic structures of corrosion-resistant materials onto boiler and pressure vessels, to improve the corrosion resistance of components within liquid-fuel and liquid-cooled reactors. Molten salts enable more economic operation due to higher temperatures (>600°C), thermal energy storage, and ability to dissolve fuel in the coolant. Coolants require the development of new corrosion resistant materials that meet or supersede existing standard codes for these systems. Reactors require validation and testing of material systems that produce robust component structures enabling them to withstand corrosive environments. The Phase I/II objective is to develop and demonstrate a scalable, low-cost nuclear reactor bimetallic overlay electrodeposition process that can improve the lifetime and durability of molten salt reactor components. State-of-the-art overlays and diffusion bond processes based on a scalable approach will further improve corrosion resistance to high temperature operation. Demonstrated efficacy of a manufacturing process for overlay deposition onto certified materials for improved lifetime and durability of molten fluoride salt reactor components by: developing electrodeposition conditions to apply nickel-molybdenum overlays; performing diffusion bonding of the overlay to substrate via hot isostatic pressing; 500 hour molten fluoride salt corrosion trials at 700°C; preparing a preliminary economic analysis. Studies showed: ability to grade overlays; hot isostatic pressing of overlay without delamination or debonding; reduced mass loss during molten fluoride salt corrosion trial by over 80%; reduced substrate intergranular attack; estimated cost for overlay on 3-ft 316H pipe of $92 compared to $146.39 for Hastelloy N. Optimize control of bimetallic nickel-molybdenum overlay application (electrodeposition, diffusion bonding) process to improve overlay microstructure and achieve lower mass loss and less intergranular attack during static and continuously flowing molten fluoride salt reactor trials. Process scaling-optimization will provide understanding required to apply overlays onto the internal pipe diameter enabling simulated molten salt reactor heat exchanger trials. Phase II will establish the potential commercial readiness of the overlay and down-selected /optimized the parameters required to improve the lifetime and durability during molten salt reactor operation. This approach could be used to apply low cost high value corrosion resistant overlays to a wide range of substrates for pre-use and repair applications within the high temperature corrosion community. This not only includes nuclear reactors but concentrated solar cell systems, supercritical carbon dioxide systems, and many others.