Performance of Ti-coated SiC at high-temperature steam as accident tolerant fuel cladding

Pham, V. H.   ; Ishibashi, Ryo*; Sasaki, Masana*; Nemoto, Yoshiyuki  ; Yamashita, Shinichiro   

Silicon carbide (SiC) is one of most potential candidates for accident tolerant fuel claddings. Among these candidates, SiC shows the best performance under severe accident conditions in high-temperature steam. However, during normal operation, there are some concerns on the dilution of silica from SiC in aqueous environment under long-term operation/irradiation. In order to improve its performance under normal operation, coating of Titanium-layer on SiC cladding was proposed. To study the influence of the Ti-coating layer on oxidation resistance of SiC cladding and its performance at high-temperature steam, oxidation tests of Ti-coated SiC samples in steam up to 1500C were carried out. Results of this study showed that Ti coating layer did not negatively affect much on the oxidation resistance of the SiC cladding. No spallation/lamination was observed on sample surface or coating layer, even on the sample after oxidation at 1500C in steam for two hours. Oxidation kinetics of the Ti-coated SiC seemed to follow two different oxidation states. Comparison of oxidation tests among Zry-4 and SiC and Ti-coated SiC showed that SiC cladding in general and Ti-coated SiC cladding specifically exhibited a considerably lower oxidation rate than Zry-4 cladding. This lower oxidation rate would benefit in resulting less exothermic heat and less hydrogen generation in severe accident events.