The Fracture and Spallation of Zirconia Layers in High Burnup PWR Fuel Claddings Submitted to RIA Transients
Titre du congrès :SMIRT-18 International Conference on Structural Mechanics in Reactor Technology
Ville du congrès :Pékin
Date du congrès :07/08/2005
Several high-burnup PWR-fuel-claddings associated to high corrosion levels have been subjected to RIA transients in the CABRI facility. The zirconia layer surrounding the Zircaloy-4 fuel rods exhibited a complex behavior during the RIA transients. Regularly spaced incipient cracks are initiated in the zirconia layer and stop at the Zircaloy interface beneath the oxide. These cracks are mainly initiated in the direction normal to the maximum principal stress. The crack density in post-test metallographies appears to be tightly linked to the maximum applied strain. This cracking process is sometimes followed by oxide spalling. Oxide spalling has a major impact on thermal-mechanical fuel rod behavior during such transients, thus the understanding and modeling of spallation is an issue that deserves attention. The present paper provides a quantitative analysis of the related data generated within the scope of the CABRI REP-Na tests, in the last decade, and more recently in the first tests of the CABRI Water loop program. A link with several other mechanical testing programs such as tensile tests, creep tests is also established.