Modelling FeCrAl cladding thermo-mechanical performance: CIEMAT’s contribution to IAEA/CRP ATF-TS

• FRAPCON/FRAPTRAN extensions were developed to assess FeCrAl cladding’s response in DBA and DEC-A/LOCA scenarios. • First-time derivation of an instantaneous plasticity model for FeCrAl alloy C26M strain-hardening. • Fuel safety evaluation methodology suggests improved performance in DEC-A, but no differences with Zircaloy under DBA. This paper provides insights into the response of the advanced technology fuel (ATF) cladding FeCrAl during postulated design basis accident (DBA) and design extension condition without significant fuel degradation (DEC-A) scenarios. Such insights are gained through the development and application of in-house extensions of the FRAPCON/FRAPTRAN fuel performance codes, coupled with the statistical tool DAKOTA, within the framework of a loss-of-coolant accident (LOCA) safety evaluation methodology. While most of the specific FeCrAl models and correlations embedded in these extensions have been documented in the existing literature, the derivation of an instantaneous plasticity model describing the strain-hardening behaviour of FeCrAl alloy C26M is presented for the first time in this paper. The application of the methodology to the DEC-A/LOCA scenario suggests an improved performance of the advanced cladding material, as it maintains its integrity, in contrast to Zircaloy. However, in the DBA/LOCA scenario, no significant differences between these cladding materials were observed.