**2. Oxidation characteristics of Zircaloy-3 cladding**

The temperature range which might be encountered for the evaluation of the effects of oxidation on the Zircaloy-3 cladding for the TREAT fuel is from room temperature, approxi‐ mately 25°C, to 1200°C. Extremely unlikely accidents cause temperature to approach 1200°C. Normal reactor operation restricts the maximum temperature to 600°C. The design basis reactivity insertion accident must not cause the cladding to exceed an equilibrium temperature of 820°C. During typical reactor operations, the cladding is below 600°C in a transient and near room temperature the rest of the time. So, the corrosion which occurs in all these temperature range is of interest.

Oxidation rate data in air have been obtained on zirconium, Zircaloy-2, and Zircaloy-4. Limited rates have been measured for Zircaloy-3, but rates are lower than Zircaloy-2. Conservatively, the data obtained by Kendall [11] on Zircaloy-2 are used to represent the rates of Zircaloy-3. Zircaloy-4 rates are higher. The following discussion presents the characteristics of the oxidation of zirconium and the above alloys in the temperature range of interest (25 to 820°C).
