Alumina Nanoceramic Coatings: An Enabling Technology for Heavy Liquid Metal-Cooled Fast Reactors

Next generation nuclear systems will outperform the current fleet of reactors by providing innovative solutions to the long-lasting issues of non-proliferation, fuel cycle efficiency, radioactive waste management, safety and economics. However, in order for this scenario to become reality novel materials are to be developed to sustain the far more demanding operating conditions of these advanced plant concepts: higher burnup and operating temperature, intense radiation fields, liquid metal or molten salt corrosion and tritium permeation. A short-term solution to this daunting challenge is to develop coatings for qualified structural materials capable to withstand the reactor environment. In the last years, the Istituto Italiano di Tecnologia (IIT) has developed multifunctional nano-ceramic coatings, by means of Pulsed Laser Deposition (PLD), for high-temperature Heavy Liquid Metal (HLM)-cooled systems, such as Generation-IV (GIV) and fusion reactors. Optimized coatings of alumina (Al₂O₃) on the relevant substrates (i.e. AISI 316, 1515-Ti and EUROFER-97 steels) have been tested as anti-corrosion, anti-tritium-permeation radiation-resistant barriers. In particular, their compatibility in presence of Pb and Pb-alloys has been proven up to 10˙000 hours, at 550 °C and the tritium permeation reduction of these films has been found in the order of 104-105. Furthermore, Al2O3 coatings showed excellent behavior under heavy ions irradiation, at damage levels relevant for fission and fusion applications (up to 450 dpa), preserving integrity and barrier performance, while evolving from an amorphous to a crystalline state. In sum, Al2O3 coatings deposited by PLD hold promise as valuable technology for next generation, safe and economically competitive nuclear power plants. (author)