(a) Results of screening steam oxidation tests at very high temperatures, performed at KIT on WH SiC/SiC composite fuel claddings: 1600 °C, 1 h (left); 1700 °C, 1 h (middle); 1750 °C, 16 min (right). Severe damage is visible on the surface of the tube tested at 1750 °C; SEM/EDS inspection of all tube surfaces detected the formation of SiO₂. (b) Transient steam oxidation test (heating rate: 10 °C/min) to 1845 °C performed at KIT on CEA SiC/SiC composite fuel claddings showed severe tube damage accompanied by a gaseous phase release. Transient tests require sealed rodlets filled with graphite susceptors for high-frequency inductive heating (c). Light optical microscopy images of metallographic cross-sections of intact (d) and damaged (e) tube areas; the latter shows the failure of the outer CVD SiC layer (adapted from [38]).