Electrodeposited Overlays for Improved Durability of Nuclear Reactors

C47-20a-271162Next generation molten salt reactor systems require the development of scalable processes to apply bimetallic structures of corrosion-resistant materials onto boiler and pressure vessels. This will improve the corrosion resistance, reliability, and lifetime of components in liquid-fuel and liquid-cooled reactors. Molten salts enable economical operation due to higher temperatures (>600°C), thermal energy storage, and ability to dissolve fuel in the coolant. Coolants require 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. Develop and demonstrate a scalable, low-cost bimetallic overlay electrodeposition process to improve the lifetime and durability of molten salt reactor components. State-of-the-art overlays and diffusion-bond processes, based on scalable manufacturing-ready approaches, will improve corrosion resistance to high temperature operation, and help to drive near- and long-term commercialization of molten salt systems. Functionally graded diffusion-bonded bimetallic overlays eliminated corrosive attack of 316H stainless steel substrates after exposure to molten fluoride-lithium-sodium- potassium salts at 750°C for 1000 hours. Overlays were applied to the internal diameter of small pipes, as exemplars for fluid transfer, heat exchangers, and reactors. The combined cost of a 316H stainless steel pipe and an overlay was 67% less expensive than building the same component out of nickel-based superalloys. These technical and economic benefits led to support and interest from the molten salt cooled, nuclear, concentrated solar power, supercritical carbon dioxide cycles, and methane pyrolysis communities. Overlays will be applied and diffusion bonded onto target substrates and components (valves, plumbing, and heat exchangers) of interest to the team. The overlay properties (corrosion resistance/adhesion) will be validated in simulated environments. Data obtained from processing and testing will be used to develop standards for the materials and manufacturing process recommendations (i.e., technical specification sheets and preferred operating procedures) for commercial overlay application. Development and demonstration of these technical/commercial elements will lead to commercial acceptance of the overlay technology and alignment with future government and commercial missions. This technology produces a low-cost, high-value corrosion resistant overlay that can be applied to a wide range of substrates and components for manufacturing and repair applications within the molten salt cooled community. This includes nuclear reactors, concentrated solar cell, supercritical carbon dioxide cycles, and methane pyrolysis systems.