The Behavior of Cr-coated Zry cladding above the eutectic temperature

Mohamad, A. B. ; Nemoto, Yoshiyuki  ; Furumoto, Kenichiro*; Okada, Yuji*; Sato, Daiki*

The development of Accident Tolerant Fuel (ATF) was initiated to search for better and new materials to improve the safety of Light Water Reactors (LWRs). It is widely recognized that the Cr coating on Zry cladding has shown an improvement in behavior under accident conditions and in normal operation. However, some issues have been pointed out by experts in the development of Cr coatings: eutectic temperature of Cr-Zr, brittleness of the intermetallic phase, ductility limit after quenching and cracking of the Cr coating. In this presentation, the oxidation behavior of Cr-coated Zr cladding above the eutectic temperature and the mechanical behavior of the intermetallic phase obtained from the small-scale tests are elucidated in detail. From the JAEA high temperature oxidation test, the liquid fraction of the intermetallic phase did not melt the cladding itself, although it was tested above the eutectic temperature. In addition, the hardness of the intermetallic phase is slightly lower than that of the oxygen-stabilized zirconium phase. In the near future, it will be necessary to carry out large scale tests on the Cr-coated Zry cladding in order to better understand the integrity of this cladding material under accident conditions.