The corrosion of some zirconium alloys under radiation in moist carbon dioxide-air mixtures

In-reactor experiments are reported in which Zircaloy-2 and $\text{Zr-2}\text{1}\text{2}$ wt % Nb alloys were exposed to moist carbon dioxide-air mixtures at 300°C for periods up to ≈ 800 days. For Zircaloy-2 the corrosion was significantly enhanced by the reactor radiation but the percentage hydrogen pick-up was reduced. For $\text{Zr-2}\text{1}\text{2}$ wt % Nb alloy the effect of radiation on the corrosion rate ranged from a slight suppression to a significant enhancement, depending on the metallurgical condition of the alloy, but there appeared to be no effect on the percentage hydrogen pick-up. The effect of improving the purity of the corrodent was also studied in the absence of radiation. The results are used to predict that the corrosion and hydrogen pick-up of typical reactor pressure tubes exposed to moist carbon dioxide-air mixtures are unlikely to cause a significant deterioration of their mechanical properties.