Development of high-performance nuclear components is a crucial objective to achieve the lifetime extension of the existing nuclear fleet and boost the deployment of emerging advanced reactor technologies. Austenitic stainless steels, particularly type 316, have been used extensively as a structural material for nuclear reactors because of their relatively low cost and high corrosion resistance, excellent processability, and high temperature stability. However, they suffer from severe corrosion attack in liquid metals and molten salts above 500oC. To improve their corrosion resistance, surface modification of the steel surface with Al2O3 is promising. Therefore, there is a strong need to evaluate the irradiation tolerance of Al-based coatings. For this purpose, the proposed project is designed to perform the irradiation of Al2O3-coating formed on stainless steel 316L through a combined electrodeposition and subsequent thermal treatment approach, and to conduct post-irradiation-examination (PIE) studies. The dual beam high-dose irradiation based on aluminum ions and helium ions, is likely to produce significant structural changes within the coating layer and across the coating-substrate interface. The formation of dislocation loops, cavities, or component precipitation, and the mechanical property changes of the samples can be disclosed through the advanced characterization of the control sample and irradiated samples with state-of-the-art techniques. Furthermore, the changes of the corrosion resistance to corrosive media for the irradiated samples will also be evaluated in this project.

The proposed project is of practical and fundamental importance for developing advanced nuclear technologies. Because Al-based coatings have high tolerance to irradiation damage, high temperatures, corrosive coolants, and reactive fission products, they could significantly improve the performance of nuclear structural materials for wide nuclear applications. Alumina coatings have the potential to improve the tolerance of structural materials to liquid metals (sodium and lead) for fast reactors, tritium for fusion reactors, high temperatures for accident-tolerant light-water reactors. Alumina and aluminum nitride coatings also have high tolerance to corrosive molten salts for molten salt reactors. This project will enable rapid and straightforward examinations of alumina coatings in highly irradiative and high temperature environments. The obtained results will help us develop strategies to develop technologies for manufacturing high-performance coatings based on the requirements of nuclear applications. Fundamentally, this project will improve our understanding of irradiation-induced structural changes within the coating, the substrate, and their interface based on the Al2O3-coated SS 316L model system. The dual ion beam technique based on the simultaneous introduction of heavy ions (such as Fe ions) and helium ions provides a surrogate of 27Al(n, α)24Na reaction to study the Al-based coatings and structural materials, as well as an accelerated irradiation method since two ion beams are simultaneously employed. Furthermore, the advanced characterization of the control sample and irradiated samples with state-of-the-art techniques makes it possible to elucidate the relation between the structural changes and the irradiation. These studies have not been reported so far.