SiC composite claddings: LWR performance optimization for nominal and accident conditions

The Fukushima Daiichi event in 2011 demonstrated the need for enhanced nuclear energy safety, becoming a major driving force for global investments in accident-tolerant fuels (ATFs) over the past decade. Candidate ATF cladding material concepts that are being developed in replacement of the standard zirconium-based alloy (zircaloy) fuel cladding materials used in light water reactors (LWRs) must outperform commercial zircaloys under nominal operation, high-temperature transient (<1200°C) and accident (>1200°C) conditions. SiC/SiC composites are a rather revolutionary ATF cladding material concept exhibiting inherent refractoriness, pseudo-ductility, and a lack of accelerated oxidation during a loss-of-coolant scenario. Due to their unique potential in meeting the stringent property requirements of the ATF cladding application, SiC/SiC composites have already claimed large global investments. Despite these investments, all state-of-the-art variants of the SiC/SiC composite cladding material concept must still overcome inherent shortcomings prior to their perspective deployment. Two important weaknesses are their inadequate compatibility with the coolant (water and steam) and the early (<2 dpa) saturation of radiation-induced swelling during nominal operation. SCORPION strives for a radical improvement in the performance of SiC/SiC composite fuel claddings by highly innovative material tailoring on the nanoscale, so as to limit hydrothermal corrosion and radiation swelling, while also modifying the fibre/matrix interface for better stability under irradiation and in high-temperature oxidizing environments. SCORPION is an ATF application-driven international collaboration between Europe, the USA and Japan, which combines multidisciplinary scientific excellence, stakeholder know-how, and cutting-edge manufacturing approaches to produce proof-of-concept SiC/SiC composite cladding materials with a radically optimized performance for Gen-II/III LWR service environments.