Numerical investigation against CABRI-E7 experiment by coupling fuel-pin failure module with FRTAC

Fuel-pin failure hold considerable importance in safety evaluations of sodium-fast reactors (SFRs) as fuel swelling and cladding rupture are key phenomena in the early stages of core disruptive accidents (CDAs). For transients leading to pin failure, the failure modes and initial fuel disruption depend partly on pre-transient irradiation effects, such as fission-gas retention and release, fuel swelling, cladding deformation, and central void formation. With the increasingly stringent requirements on safety analysis, it is necessary to accurately evaluate the thermo-mechanical degradation of the fuel-pin resulting from pre-transient irradiation. Therefore, this study developed a fuel-pin failure module based on mechanistic models of pre-transient fuel-pin characterization and proposed an innovative approach by coupling this module with the self-developed Fast Reactor Transient Analysis Code (FRTAC). The results of the numerical simulation against the CABRI-E7 test are presented and discussed in this paper. The expected heat transfer mechanism between fuel and cladding was reproduced by the simulation, and the temperature distribution of the fuel pin agreed well with other reference analysis codes. Additionally, analyses based on elastoplastic mechanics theory and biaxial stress rupture criteria were conducted, with a specific focus on the thermal and mechanical failure of the fuel-pin. The overall code assessment indicated that the prediction error was within an acceptable range, demonstrating that the module's reliability and its applicability to safety analyses of oxide fuel in CDAs of SFRs.