Reaction of yttria-stabilized zirconia with zirconium, silicon and Zircaloy-4 at high temperature: a compatibility study for cermet fuels

Compatibility studies for cermet (ceramic and metal) fuels have been completed for a temperature range of 1073–1423 K. A reaction between yttria-stabilized zirconia (YSZ), as a simulated fuel, and Zr, as a candidate for a metallic matrix, has been observed at temperatures ⩾1273 K, which means the formation of a metallic reaction layer at the interface between YSZ and Zr and the occurrence of metallic phases inside the YSZ. Similar results were observed for the YSZ–Zry4 (cladding) system. On the other hand, the degree of reaction was relatively large for the YSZ–Si (metallic matrix) system, and Si diffused into the YSZ. However, the maximum fuel center-line temperature can be predicted to be less than ≈1273 K for cermet fuels. Therefore, compatibility between the ceramic fuel and the metallic matrix should be good under normal reactor operational conditions. Furthermore, since the temperature of the fuel-cladding gap is lower, the cermet fuel and the cladding material are compatible.