THE KINETICS OF UNIFORM OXIDE FORMATION AND ITS RELATIONSHIP TO RADIATION EFFECTS ON ZIRCALOY-2

Specimens of Zircaloy-2 plate were irradiated with 2 MeV proton at 350 degrees C up to total dose of I dpa (displacement per atom). Uniform corrosion tests, at 400 degrees C in 10.3 MPa steam, were performed in an autoclave. It was found that the radiation enhanced the uniform co rrosion rate. The oxide morphology was studied by cross-sectional tran smission electron microscopy. The oxide consists of two types of oxide layer, one formed in the early stage which is equiaxial, the other fo rmed later which is columnar. Comparing the as-received and irradiated specimens, it was found that the difference in oxide thickness depend s on the development of columnar oxide layer. The effect of radiation on the oxide morphology is considered to be the same in the oxide nucl eation stage, but produces a significant difference in the oxide growt h stage. It is believed that the stress induced the oxide morphology e volution, and had some effects on the corrosion behavior. A corrosion model is proposed to explain these results.