Comparison of the PWR cladding corrosion models for test IFA-638.1-3

The cladding corrosion test (IFA-638) is being performed to investigate the corrosion properties of different modern PWR cladding materials. The experimental results are evaluated by the corrosion models, EPRI/KWU/CE, ESCORE, NEPLC, and COCHISE. The oxide layer thickness on pre-irradiated parts (upper parts) of each rod is well predicted by the COCHISE model after 118 days exposure, but the other models overpredicted the thickness. All the models overpredicted the oxide thickness after 263 days exposure and the divergency between measured and calculated oxide thickness becomes larger. The differences in calculated oxide thickness between the models at low burnup (fresh parts) are attributed to the different transition point determinations of the models. Comparing the measurements with the calculations from the pre-irradiated parts of each rod, overall overprediction could be accounted for by the fact that the post-transition regime of all these four models were calibrated for standard Zircaloy-4 materials. The differences between the models were attributed to the empirical variables such as frequency factor (k2, B) and activation energy (Q2) in Tables 1, 2, and 3, which were calibrated with other experimental/plant data