Modelling FeCrAl cladding thermo-mechanical performance. Part I: Steady-state conditions

Among the challenges posed by accident-tolerant fuels (ATFs) is the demonstration of their safe behaviour under normal and postulated accident conditions. In order to accurately predict the response of novel materials in such scenarios, the development of modelling capabilities is paramount. This paper provides an integral characterization of FeCrAl cladding under steady-state conditions up to high burnup, highlighting the major differences with respect to Zircaloy-4 and the key properties responsible for their distinct behaviour. To that end, the fuel performance code FRAPCON-4.0 has been extended to FeCrAl cladding simulation. Such extension has been carried out according to a critical review of the thermo-mechanical data and correlations reported in the open literature for several FeCrAl alloys. The main outcome of this study is that there are no major performance differences between FeCrAl and Zircaloy-4 at end-of-life, except for their stress states, which differ due to different creep deformation rates. Therefore, modelling the thermo-mechanical response of FeCrAl cladding would benefit from an accurate description of its creep behaviour, not only in the case of foreseeable conditions during reactor operation but also for the potential implications that it may have under transient scenarios.