Electrodeposited Overlays for Improved Durability of Nuclear Reactors

The Department of Energy seeks state of the art techniques and processes to improve the reliability and extend the life of next generation molten salt reactor systems. One such requirement for implementation of these next generation systems is an improvement in the system sustainability by developing scalable processes to apply bimetallic structures of corrosion-resistant materials onto standard boiler and pressure vessels, such that the corrosion resistance of components within liquid-fuel and liquid cooled reactors can be improved. The use of molten salts enables more economic operation due to higher temperatures (>600°C), thermal energy storage, and the ability to dissolve fuel in the coolant medium. These coolants will require the development of new corrosion resistant material systems that will have to meet or supersede existing standard codes for these systems. Therefore, state of the art reactors require validation and testing of new material systems that can produce robust component structures and enable them to withstand these corrosive environments. The overall objective of the Phase I and II programs is to develop and demonstrate a scalable, low cost nuclear reactor overlay process that can improve the corrosion resistance and lifetime of molten salt reactor components. Additionally, we will evaluate the potential of various state of the art overlays and bond diffusion processes based on our scalable approach, to further improve corrosion resistance to high temperature operation. In Phase I, the team will apply a range of nickel molybdenum compositions with controlled thicknesses onto qualified substrates. State of the art hot isostatic pressing processes will be developed for diffusion bonding the overlay to the substrate. These preparation procedures will then be optimized by evaluating the amount of inter-diffusion between the overlay and substrate and by performing standard adhesion tests. After optimization, a limited number of the best overlays will be produced for corrosion evaluation using a state-of-the-art molten salt reactor. Toward the end of Phase I a preliminary economic and scalability assessment will be undertaken to ensure the cost effectiveness of the approach. In Phase II, the overlay process will be scaled to overlay and diffusion bond prototype boiler and pressure vessels of interest to the Department of Energy for beta-scale performance testing. This approach could be used to apply low cost high value corrosion resistant overlays to a wide range of substrates. These overlays could provide a low cost solution that could improve the corrosion and erosion resistance of a large number of valuable systems that have durability challenges due to chemistry and heat. This not only includes nuclear reactors but concentrated solar cell systems, supercritical carbon dioxide systems, and many others.