High-temperature steam-oxidation behavior of Zr-1Nb cladding alloy E110

Oxidation experiments were conducted at 1000–1200 °C in flowing steam with samples of as-received Zr-1Nb alloy E110 tubing and/or polished E110 tubing. The purpose was to determine the oxidation behavior of this alloy under postulated loss-of-coolant accident conditions in light water reactors. The as-received E110 tubing exhibited a high degree of susceptibility to nodular oxidation and breakaway oxidation at relatively low test times, as compared to other cladding alloys. The nodules grew much more rapidly at 1000 °C than 1100 °C, as did the associated hydrogen uptake. The oxidation behavior was strongly affected by the surface condition of the materials. Polishing to ≈0.1 μm roughness (the roughness of the as-received tubing was ≈0.4 μm) delayed breakaway oxidation. Polishing also removed surface impurities. For polished samples oxidized at 1100 °C, no significant nodular oxidation appeared up to 1000 s. For polished samples oxidized at 1000 °C, hydrogen uptake >100 wppm was delayed from ≈300 s to >900 s. Weight-gain coefficients were determined for pre-breakaway oxidation of polished-only and machined-and-polished E110 tubing samples: 0.162 (mg/cm2)/s0.5 at 1000 °C and 0.613 (mg/cm2)/s0.5 at 1100 °C.