Improved Modelling For Oxidation Of Zircalloy Fuel Cladding Tubes In PWRs

Sammanfattning: The fuel cladding is an essential component in the defence-in-depth strategy for nuclear safety. Its integrity and durability are therefore critical for maintaining acceptable safety conditions. However, the integrity of the cladding can be compromised during normal operation due to corrosion and hydriding. To ensure a sufficient level of safety, design and safety criteria have been established to limit oxidation and hydriding. EDF has various multiphysics software tools at its disposal to ensure that these criteria are met. One such tool, CYRANO3, uses oxide thickness measurements from the beginning of the French nuclear industry to model corrosion and hydriding. This study aims to improve CYRANO3 by expanding its validation database and improving its models. The first part of the study focuses on improving the CYRANO3 database by providing a more comprehensive understanding of normal corrosion in a pressurized water reactor, allowing the models to be recalibrated to better represent actual corrosion behaviour.  In the second part, a deeper analysis is conducted to improve the models and increase knowledge of the parameters that influence corrosion. This analysis highlights the significance of temperature and power as input parameters, which will affect the accuracy of CYRANO3 results. Additionally, this study has identified areas for further improvement, including modifications to the implemented corrosion models and a better understanding of the assumptions made about input data.