Thermomechanical Assessment of Fuel Rod Cladding Made of Zirconium Alloy and Silicon Carbide Material During Reactivity-Initiated Accident

This paper presents a thermomechanical assessment of various types of fuel cladding during a reactivity-initiated accident (RIA) which is simulated by the finite element analysis program ANSYS. Four cladding concepts are analyzed; one concept considers currently used zirconium alloy and three concepts consider silicon carbide (SiC) material. The SiC claddings consist either of composite material or of a two-layered structure formed of SiC composite and monolithic SiC. Each cladding is analyzed for two states of nuclear fuel: fresh and high burnup. A gap that exists between fuel pellets and cladding in fresh state is either reduced or removed in a high burnup state. It was shown that zirconium cladding resists RIA conditions very well in fresh state, however, in high burnup state significant stress and plastic strain occur. The SiC cladding was shown to have many advantages over zirconium alloy. Nevertheless, its lower strength appears to be critical in RIA conditions when cladding needs to withstand exceeding loading after the fuel-cladding gap disappears due to the expansion of the fuel pellet.