Steam oxidation of PFC materials for advanced tokamaks

Steam chemical reactivity experiments were conducted for several ITER-like tokamak plasma-facing-component (PFC) materials: NB31 and NS31 carbon fiber composites (CFCs), W-1%La, DShG-200 Be, and Be (S65C and Kawecki PO Ductile Be) specimens irradiated to fast neutron fluences ranging from 5 × 10¹⁹ to 1 × 10²¹ n/cm². Experiments were performed at 800-1100 °C for CFC, 550-1000 °C for W-1%La, 500-900 °C for unirradiated Be, and 600-800 °C for irradiated Be. Average hydrogen generation rates are presented for these new measurements as a function of temperature, and the results are compared to previous studies on similar materials. In general, the new results extend the temperature and material range from previous studies, are consistent with previous work, and provide Arrhenius-type hydrogen generation expressions useful for safety assessment calculations. Little irradiation influence on oxidation behavior was observed for Be irradiated to 1 × 10²¹ n/cm², whereas significant influence was observed in previous tests on Be irradiated to 5 × 10²² n/cm².