Application of chemical interaction between (Fe, Cr) oxides and Mo oxide at high temperature for self-healing intelligence on nuclear fuel cladding in LWRs

A novel scheme for a bilayer coating with self-healing ability is proposed in this study. The candidate materials for the coatings and the potential self-healing reaction are assessed in high-temperature aqueous environments and high-temperature air. The pure Cr2O3 layer and the composite of Cr2O3 and MoO3 are the candidate materials for the outer layer and inner layer, respectively, due to their compatibility under normal condition and fabricability. Fe2O3–MoO3 reactions exhibit a potential ability to heal the cracks because of a high reaction rate under normal condition. The self-healing process proceeds via the following mechanism under normal condition: Fe2O3 (a corrosion product in the coolant) diffuses into the cracks on the coating and reacts with MoO3 (inner layer) to produce the insoluble Fe2(MoO4)3, which deposits and repairs the cracks. In the loss-of-coolant accident (LOCA) situation, Cr2O3–MoO3 reaction is expected to strengthen the adhesion of the coating.